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Cache-Enabled in Cooperative Cognitive Radio Networks for Transmission Performance
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作者 Jiachen Yang Chaofan Ma +3 位作者 Jiabao Man Huifang Xu Gan Zheng Houbing Song 《清华大学学报自然科学版(英文版)》 EI CAS CSCD 2020年第1期1-11,共11页
The proliferation of mobile devices that support the acceleration of data services(especially smartphones)has resulted in a dramatic increase in mobile traffic. Mobile data also increased exponentially, already exceed... The proliferation of mobile devices that support the acceleration of data services(especially smartphones)has resulted in a dramatic increase in mobile traffic. Mobile data also increased exponentially, already exceeding the throughput of the backhaul. To improve spectrum utilization and increase mobile network traffic, in combination with content caching, we study the cooperation between primary and secondary networks via content caching. We consider that the secondary base station assists the primary user by pre-caching some popular primary contents.Thus, the secondary base station can obtain more licensed bandwidth to serve its own user. We mainly focus on the time delay from the backhaul link to the secondary base station. First, in terms of the content caching and the transmission strategies, we provide a cooperation scheme to maximize the secondary user’s effective data transmission rates under the constraint of the primary users target rate. Then, we investigate the impact of the caching allocation and prove that the formulated problem is a concave problem with regard to the caching capacity allocation for any given power allocation. Furthermore, we obtain the joint caching and power allocation by an effective bisection search algorithm. Finally, our results show that the content caching cooperation scheme can achieve significant performance gain for the primary and secondary systems over the traditional two-hop relay cooperation without caching. 展开更多
关键词 COOPERATIVE COGNITIVE radio network content CACHING power ALLOCATION
Detecting Fake News Over Online Social Media via Domain Reputations and Content Understanding
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作者 Kuai Xu Feng Wang +1 位作者 Haiyan Wang Bo Yang 《清华大学学报自然科学版(英文版)》 EI CAS CSCD 2020年第1期20-27,共8页
Fake news has recently leveraged the power and scale of online social media to effectively spread misinformation which not only erodes the trust of people on traditional presses and journalisms, but also manipulates t... Fake news has recently leveraged the power and scale of online social media to effectively spread misinformation which not only erodes the trust of people on traditional presses and journalisms, but also manipulates the opinions and sentiments of the public. Detecting fake news is a daunting challenge due to subtle difference between real and fake news. As a first step of fighting with fake news, this paper characterizes hundreds of popular fake and real news measured by shares, reactions, and comments on Facebook from two perspectives:domain reputations and content understanding. Our domain reputation analysis reveals that the Web sites of the fake and real news publishers exhibit diverse registration behaviors, registration timing, domain rankings, and domain popularity. In addition, fake news tends to disappear from the Web after a certain amount of time. The content characterizations on the fake and real news corpus suggest that simply applying term frequency-inverse document frequency(tf-idf) and Latent Dirichlet Allocation(LDA) topic modeling is inefficient in detecting fake news,while exploring document similarity with the term and word vectors is a very promising direction for predicting fake and real news. To the best of our knowledge, this is the first effort to systematically study domain reputations and content characteristics of fake and real news, which will provide key insights for effectively detecting fake news on social media. 展开更多
关键词 SOCIAL media FAKE NEWS detection CONTENT modeling DOMAIN reputations
Effects of Cooking and Processing Methods on Nitrate Content in Leafy Vegetables 预览
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作者 Huihe LI 《农业生物技术:英文版》 CAS 2019年第3期95-97,共3页
[Objectives]The aim is to provide a theoretical basis for people to store and process vegetables more scientifically.[Methods]Changes in the nitrate content of three kinds of leafy vegetables (cabbage,lettuce and cele... [Objectives]The aim is to provide a theoretical basis for people to store and process vegetables more scientifically.[Methods]Changes in the nitrate content of three kinds of leafy vegetables (cabbage,lettuce and celery) cooked and processed by different methods were studied.[Results]After the three kinds of leafy vegetables were processed by different methods,the nitrate and vitamin C content of the leafy vegetables reduced,and their reduction was above 50% after they were boiled.After they were salted for 5 min,nitrate content decreased by 20%-40%,and changed slightly with time.Salting had a small effect on Vc content.After lettuce and celery were soaked in 0.05% NaCl solution for 30 min,the effect was the best.CaCl2 had an obvious effect on the reduction of nitrate content in lettuce.[Conclusions]The study is of great significance to safety production and evaluation of edible value of agricultural products. 展开更多
关键词 LEAFY VEGETABLES NITRATE CONTENT VC CONTENT
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Seed filling dynamic traits of oil flax in response to nitrogen and phosphorus 预览
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作者 Yaping Xie Bin Wang +8 位作者 Limin Wang Junyi Niu Wei Zhao Bin Yan Li Zhao Zhao Dang Wenjuan Li Yanni Qi Jianping Zhang 《Oil Crop Science-中国油料作物学报英文版》 2019年第3期152-165,共14页
Crop yield is primarily seed-filling-limited in production system under field conditions.This study was aimed to determine whether seed filling traits of oil flax(Linum usitatissimum L.)could be controlled by phosphor... Crop yield is primarily seed-filling-limited in production system under field conditions.This study was aimed to determine whether seed filling traits of oil flax(Linum usitatissimum L.)could be controlled by phosphorus(P),nitrogen(N),and phosphorus and nitrogen(NP)supply.Effects on seed filling traits were investigated in 2 years including capsule diameter,capsule height,capsule dry matter(DM),seed DM per capsule,pericarp DM per capsule,protein content and oil content.DM translocation from pericarps to seed,translocation efficiency,and contribution of photoassimilates during seed filling period were also detected.In a randomized complete block design,cultivar'Longyaza 1'was grown under P(33 kg P/ha),N(75 kg N/ha),and NP(33 kg P/ha and 75 kg N/ha)along with a zerofertilizer(CK)treatment in 2013 and 2014.Results suggested that DM translocation efficiency and contribution efficiency increased to different extent due to P,N or NP application.At 42 DAA(days after anthesis),seed DM per capsule reached the greatest,while protein content and pericarp DM obtained the least level.However,the highest oil content was detected at 35 DAA.A significant positive linear relationship was observed between seed DM,capsule DM and DM translocation in both years.Protein content showed inconsistent relation with oil content.The results indicated that appropriate N and P management could be an effective approach to increase oil flax production. 展开更多
关键词 OIL FLAX nitrogen phosphorus seed filling dry matter TRANSLOCATION EFFICIENCY contribution EFFICIENCY protein CONTENT OIL CONTENT
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硝苯地平缓释片(Ⅰ)含量及含量均匀度测定方法的改进
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作者 王玮 秦绍刚 《首都食品与医药》 2019年第12期188-189,共2页
建立了高效液相色谱法(HPLC)法测定硝苯地平缓释片(Ⅰ)含量及含量均匀度的分析方法。采用AgilentZORAX EclipseXDBC18色谱柱(250mm×4.6mm,5μm),以甲醇-水(60:40)为流动相,流速为1.0ml·min-1,检测波长为235nm,进样量为20μl,... 建立了高效液相色谱法(HPLC)法测定硝苯地平缓释片(Ⅰ)含量及含量均匀度的分析方法。采用AgilentZORAX EclipseXDBC18色谱柱(250mm×4.6mm,5μm),以甲醇-水(60:40)为流动相,流速为1.0ml·min-1,检测波长为235nm,进样量为20μl,柱温为30.0℃。结果表明,硝苯地平峰与样品中的相邻峰能达到良好分离。经过方法学验证,本法可为分析硝苯地平缓释片(Ⅰ)含量及含量均匀度提供检测依据。 展开更多
关键词 硝苯地平缓释片(Ⅰ) 含量 含量均匀度 方法改进
A preliminary study on an upper ocean heat and salt content of the western Pacific warm pool region 预览
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作者 Xiaoxin Yang Xiaofen Wu +1 位作者 Zenghong Liu Chunxin Yuan 《海洋学报:英文版》 SCIE CAS CSCD 2019年第3期60-71,共12页
On the basis of Argo profile data of the temperature and salinity from January 2001 to July 2014, the spatial distributions of an upper ocean heat content(OHC) and ocean salt content(OSC) of the western Pacific warm p... On the basis of Argo profile data of the temperature and salinity from January 2001 to July 2014, the spatial distributions of an upper ocean heat content(OHC) and ocean salt content(OSC) of the western Pacific warm pool(WPWP) region and their seasonal and interannual variations are studied by a cyclostationary empirical orthogonal function(CSEOF) decomposition, a maximum entropy spectral analysis, and a correlation analysis.Probable reasons for variations are discussed. The results show the following.(1) The OHC variations in the subsurface layer of the WPWP are much greater than those in the surface layer. On the contrary, the OSC variations are mainly in the surface layer, while the subsurface layer varies little.(2) Compared with the OSC, the OHC of the WPWP region is more affected by El Ni?o-Southern Oscillation(ENSO) events. The CSEOF analysis shows that the OHC pattern in mode 1 has strong interannual oscillation, with eastern and western parts opposite in phase. The distribution of the OSC has a positive-negative-positive tripole pattern. Time series analysis shows that the OHC has three phase adjustments with the occurrence of ENSO events after 2007, while the OSC only had one such adjustment during the same period. Further analysis indicates that the OHC variations are mainly caused by ENSO events, local winds, and zonal currents, whereas the OSC variations are caused by much more complex reasons. Two of these, the zonal current and a freshwater flux, have a positive feedback on the OSC change in the WPWP region. 展开更多
关键词 ocean HEAT CONTENT SALT CONTENT the western Pacific WARM POOL ARGO data
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Effects of Different Preservation Methods on Vitamin C and Nitrate Content in Vegetables 预览
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作者 Lili SONG Huijuan ZHANG 《亚洲农业研究:英文版》 2019年第4期62-66,共5页
This paper studied and compared the effects of three preservation methods( normal temperature 20℃,fresh-keeping box cold storage 4℃,and fresh-keeping box + fresh-keeping film cold storage 4℃) on six kinds of vegeta... This paper studied and compared the effects of three preservation methods( normal temperature 20℃,fresh-keeping box cold storage 4℃,and fresh-keeping box + fresh-keeping film cold storage 4℃) on six kinds of vegetables. The results showed that the content of vitamin C in the six vegetables was higher in cold storage than in normal temperature storage;the nitrate content was lower in cold storage than in normal temperature storage. In both the normal temperature storage and cold storage,the vitamin C in vegetables declined with the increase of the storage time,while the nitrate content increased with the increase of the storage time. Thus,cold storage has better fresh-keeping effect for vegetables. In cold storage conditions,the vitamin C content was higher in vegetables packaged by fresh-keeping box,and the nitrate content was lower,followed by the fresh-keeping film + fresh-keeping box cold storage. In conclusion,the best preservation method for vegetable is fresh-keeping box cold storage. 展开更多
关键词 PRESERVATION methods Vegetable VC CONTENT NITRATE CONTENT ULTRAVIOLET SPECTROPHOTOMETRY
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Influences of soil moisture and salt content on loess shear strength in the Xining Basin, northeastern Qinghai-Tibet Plateau
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作者 FU Jiang-tao HU Xia-song +5 位作者 LI Xi-lai YU Dong-mei LIU Ya-bin YANG You-Qing QI Zhao-xin LI Shu-xia 《山地科学学报:英文版》 SCIE CSCD 2019年第5期1184-1197,共14页
Moisture and salt content of soil are the two predominant factors influencing its shear strength. This study aims to investigate the effects of these two factors on shear strength behavior of loess in the Xining Basin... Moisture and salt content of soil are the two predominant factors influencing its shear strength. This study aims to investigate the effects of these two factors on shear strength behavior of loess in the Xining Basin of Northeast Qinghai-Tibet Plateau, where such geological hazards as soil erosion, landslides collapse and debris flows are widespread due to the highly erodible loess. Salinized loess soil collected from the test site was desalinized through salt-leaching in the laboratory. The desalinized and oven-dried loess samples were also artificially moisturized and salinized in order to examine how soil salinity affects its shear strength at different moisture levels. Soil samples prepared in different ways(moisturizing, salt-leaching, and salinized) were measured to determine soil cohesion and internal friction angle. The results show that salt-leaching up to 18 rounds almost completely removed the salt content and considerably changed the physical components of loess, but the soil type remained unchanged. As salt content increases from 0.00% to 12.00%, both the cohesion and internal friction angle exhibit an initial decrease and then increase with salt content. As moisture content is 12.00%, the salt content threshold value for both cohesion and internal friction angle is identified as 3.00%. As the moisture content rises to 16.0% and 20.00%, the salt content threshold value for cohesion is still 6.00%, but 3.00% for internal friction angle. At these thresholds soil shear strength is the lowest, below which it is inversely related to soil salinity. Beyond the thresholds, however, the relationship is positive. Dissimilar to salinity, soil moisture content exerts an adverse effect on shear strength of loess. The findings of this study can provide a valuable guidance on stabilizing the engineering properties of salinized loess to prevent slope failures during heavy rainfall events. 展开更多
关键词 Salinized LOESS Desalinized LOESS Salt-leaching Shear strength indices Moisture CONTENT Salt CONTENT
复方小檗碱鞣酸蛋白胶囊的质量控制研究
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作者 黄春青 祝晶 +3 位作者 曹桂红 杨婷 许波 罗曼 《中国医院药学杂志》 CAS 北大核心 2019年第21期2152-2156,共5页
目的:建立测定复方小檗碱鞣酸蛋白胶囊中4种成分含量及马来酸氯苯那敏与硝酸硫胺含量均匀度的方法。方法:采用均匀实验优选复方小檗碱鞣酸蛋白胶囊中4种成分含量测定提取方法,采用十八烷基硅烷键合硅胶为填充剂;以磷酸盐缓冲液[0.05 mol... 目的:建立测定复方小檗碱鞣酸蛋白胶囊中4种成分含量及马来酸氯苯那敏与硝酸硫胺含量均匀度的方法。方法:采用均匀实验优选复方小檗碱鞣酸蛋白胶囊中4种成分含量测定提取方法,采用十八烷基硅烷键合硅胶为填充剂;以磷酸盐缓冲液[0.05 mol·L^-1磷酸二氢钾溶液和0.05 mol·L^-1庚烷磺酸钠溶液(1∶1),含0.2%三乙胺,并用磷酸调节至pH 3.0]-甲醇(43∶57)为流动相;检测波长262 nm;进样量10μL,测定复方小檗碱鞣酸蛋白胶囊中盐酸小檗碱、马来酸氯苯那敏、硝酸硫胺和乳酸依沙吖啶含量及马来酸氯苯那敏与硝酸硫胺含量均匀度。结果:硝酸硫胺在25.02~200.2μg·mL^-1、马来酸氯苯那敏在6.555~78.66μg·mL^-1、盐酸小檗碱在12.01~96.06μg·mL^-1和乳酸依沙吖啶在2.491~24.91μg·mL^-1范围内呈良好的线性关系。回收率分别为104.19%、98.41%、100.48%和98.72%,RSD(n=9)分别为0.56%、1.16%、1.72%和1.67%。结论:建立了简便、快速、准确测定复方小檗碱鞣酸蛋白胶囊中4种成分含量及马来酸氯苯那敏与硝酸硫胺含量均匀度的方法,为复方小檗碱鞣酸蛋白胶囊质量标准的完善提高提供依据。 展开更多
关键词 复方小檗碱鞣酸蛋白胶囊 高效液相色谱法 含量 含量均匀度
Spatial variability of soil water content and related factors across the Hexi Corridor of China 预览
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作者 LI Xiangdong SHAO Ming’an +1 位作者 ZHAO Chunlei JIA Xiaoxu 《干旱区科学:英文版》 SCIE CSCD 2019年第1期123-134,共12页
Soil water content(SWC) is a key factor limiting ecosystem sustainability in arid and semi-arid areas of the Hexi Corridor of China, which is characterized by an ecological environment that is vulnerable to climate ch... Soil water content(SWC) is a key factor limiting ecosystem sustainability in arid and semi-arid areas of the Hexi Corridor of China, which is characterized by an ecological environment that is vulnerable to climate change. However, there is a knowledge gap regarding the large-scale spatial distribution of SWC in this region. The specific objectives of this study were to determine the spatial distribution patterns of SWC across the Hexi Corridor and identify the factors responsible for spatial variation of SWC at a regional scale. This study collected and analyzed SWC in the 0–100 cm soil profile from 109 field sampling sites(farmland, grassland and forestland) across the Hexi Corridor in 2017. We selected 17 factors, including land use, topography(latitude, longitude, elevation, slope gradient, and slope aspect), soil properties(soil clay content, soil silt content, soil bulk density, saturated hydraulic conductivity, field capacity, and soil organic carbon content), climate factors(mean annual precipitation, potential evaporation, and aridity index), plant characteristic(vegetation coverage) and planting pattern(irrigation or rain-fed), as possible environmental variables to analyze their effects on SWC. The results showed that SWC was 0.083(±0.067) g/g in the 0–100 cm soil profile and decreased in the order of farmland, grassland and forestland. The SWC in the upper soil layers(0–20, 20–40 and 40–60 cm) had obvious difference when the mean annual precipitation differed by 200 mm. The SWC decreased from southeast to northwest following the same pattern as precipitation, and had a moderate to strong spatial dependence in a large effective range(75–378 km). The SWC showed a similar distribution and had no significant difference between soil layers in the 0–100 cm soil profile. The principal component analysis showed that the mean annual precipitation, geographical position(longitude and latitude) and soil properties(soil bulk density and soil clay content) were the main factors dominating the varian 展开更多
关键词 SOIL water CONTENT spatial VARIABILITY geostatistical analysis SOIL CLAY CONTENT Hexi CORRIDOR
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Synergistic antioxidant interactions between green tea and Ocimum gratissimum
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作者 Sumaya Farooq Amit Sehgal 《亚太热带生物医学杂志:英文版》 CAS 2019年第8期333-338,共6页
Objective: To evaluate the antioxidant interactions between aqueous infusions of green tea and Ocimum gratissimum at different ratios. Methods: Antioxidant activities of aqueous infusion of green tea and Ocimum gratis... Objective: To evaluate the antioxidant interactions between aqueous infusions of green tea and Ocimum gratissimum at different ratios. Methods: Antioxidant activities of aqueous infusion of green tea and Ocimum gratissimum (leaves) alone or in combination at various proportions (3:1, 2:1, 1:1, 1:2, 1:3) were determined by DPPH, ABTS, NO and ex-vivo assays including lipid peroxidation and haemolysis. Total phenolic content and flavonoid content was calculated by Folin-Ciocalteu reagent and aluminum chloride colorimetry method, respectively. A correlation study was also conducted between the antioxidant activity and total phenolic/flavonoid content of various infusions. The interactions were analyzed by combination index applying CompuSyn software. Results: Green tea exhibited high radical scavenging ability as compared to Ocimum gratissimum infusion. Combination of green tea and Ocimum gratissimum exhibited moderate antagonism to strong synergistic interaction at various ratios. A strong correlation was found between total phenolic content/total flavonoid content and antioxidant activities of individual infusions (green tea and Ocimum gratissimum). For binary mixture at different ratios, a weak to strong correlation was observed between total phenolic content and antioxidant activity and almost no correlation between total flavonoid content and antioxidant potential. Conclusions: Overall, green tea and Ocimum gratissimum combination (1:1) displayed the highest antioxidant potential and maximum synergism. 展开更多
关键词 ANTIOXIDANT Combination index Green tea OCIMUM gratissimum TOTAL PHENOLIC CONTENT TOTAL flavonoid CONTENT
Efficacy of weight adjusted bone mineral content in osteoporosis diagnosis in Chinese female population
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作者 Ting-Ting Liu Xiao-Dan Li +2 位作者 Wen-Zhi Wang Jian-Gao Zhang Ding-Zhuo Yang 《中华医学杂志:英文版》 SCIE CAS CSCD 2019年第7期772-781,共10页
Background:Areal bone mineral density(aBMD)applied for osteoporosis diagnosis unavoidably results in the missingdiagnosis in patients with large bones and misdiagnosis in those with small bones.Therefore,we try to fin... Background:Areal bone mineral density(aBMD)applied for osteoporosis diagnosis unavoidably results in the missingdiagnosis in patients with large bones and misdiagnosis in those with small bones.Therefore,we try to find a new adjusted index of bone mineral content(BMC)to make up shortcomings of aBMD in osteoporosis diagnosis.Methods:In this multi-center epidemiological study,BMC and aBMD of lumbar spines(n=5510)and proximal femurs(n=4710)were measured with dual energy X-ray absorptiometry(DXA).We analyzed the correlation between the bone mass and body weight in all subjects including four age groups(<19 years,20-39 years,40-49 years,>50 years).And then the body weight was used for standardizing BMC(named wBMC)and applied for the epidemiological analysis of osteoporosis?Results:The correlation of body weight and BMC is 0.839 to 0.931 of lumbar vertebra 1-4(Li_4),and 0.71 to 0.95 of femoral neck in different age groups.When aBMD was applied for diagnosing osteoporosis,the prevalence was 7.55%,16.39%,and 25.83%in patients with a high,intermediate,and low body weight respectively.However,the prevalence was 21.8%,18.03%,and 11.64%by wBMC applied for diagnosing osteoporosis.Moreover,the prevalence of osteoporosis increased by 3.76%by wBMC with the body weight increased by 5 kg.The prevalence decreased by 1.94%when the body weight decreased by 5 kg.Conclusions:wBMC can reduce the missed diagnosis in patients with large body weight and reduce misdiagnosis in those with small body weight.Including children,wBMC may be feasible for osteoporosis diagnosis individuals at any age. 展开更多
关键词 BONE MINERAL CONTENT Weight-standardized BONE MINERAL CONTENT BONE density Dual-energy X-ray ABSORPTIOMETRY OSTEOPOROSIS
滇中高原火后更新森林植物和土壤水分含量的时空格局
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作者 陈丽芳 窦群 +1 位作者 张志明 沈泽昊 《地理学报:英文版》 SCIE CSCD 2019年第7期1179-1192,共14页
Plant moisture content(PMC) is used as an indicator of forest flammability, which is assumed to be affected by climate drought. However, the fire-induced drought stress on PMC and its spatial and temporal variations a... Plant moisture content(PMC) is used as an indicator of forest flammability, which is assumed to be affected by climate drought. However, the fire-induced drought stress on PMC and its spatial and temporal variations are unclear. Based on a parallel monitoring experiment from 2014 to 2015, this study compared the PMCs and soil moisture contents(SMC) at five post-fire sites in central Yunnan Plateau, Southwest China. The number of years since last fire(YSF), season, topographic position, plant species and tissue type(leaf and branch) were selected as causal factors of the variations in PMC and SMC. A whole year parallel monitoring and sampling in the post-fire communities of 1, 2, 5, 11 and 30 YSF indicated that drought stress in surface soils was the strongest in spring within the first 5 years after burning, and the SMC was regulated by topography, with 64.6% variation in soil moisture accounted for by YSF(25.7%), slope position(22.1%) and season(10.8%). The temporal variations of PMC and SMC differed at both interannual and seasonal scales, but the patterns were consistent across topographic positions. PMC differed significantly between leaves and branches, and among three growth-forms. The mean PMC was lower in broad-leaved evergreen species and higher in conifer species. Season and soil temperature were the primary determinants of PMC, accounting for 19.1% and 8.3% of variation in PMC, respectively. This indicated phenology-related growth rather than drought stress in soil as the primary driver of seasonal changes in PMC. The significant variations of PMC among growth forms and species revealed that seasonal soil temperature change and dominant species in forest communities are useful indicators of fire risk assessment in this region. 展开更多
关键词 plant MOISTURE CONTENT SOIL MOISTURE CONTENT TOPOGRAPHY season SOIL temperature year since last fire drought stress
野菊多糖提取工艺研究 预览
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作者 高俊明 刘伟 +2 位作者 李斌 陈磊 田薇 《丽水学院学报》 2019年第2期56-60,共5页
以野菊为材料,研究了乙醇浓度、提取时间、回流次数对多糖提取率的影响,并在单因素试验的基础上,以滤渣中酚酸的含量及提取液中多糖的含量为指标,进行了3因素3水平的正交试验。结果表明:最佳工艺为4倍量95%的乙醇回流提取2次各1 h,该条... 以野菊为材料,研究了乙醇浓度、提取时间、回流次数对多糖提取率的影响,并在单因素试验的基础上,以滤渣中酚酸的含量及提取液中多糖的含量为指标,进行了3因素3水平的正交试验。结果表明:最佳工艺为4倍量95%的乙醇回流提取2次各1 h,该条件野菊多糖获得量最优,酚酸杂质含量最低。该工艺稳定可行,可为野菊多糖大规模提取作依据。 展开更多
关键词 野菊多糖 提取工艺 正交实验 酚酸含量测定 多糖含量测定
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阿司匹林双嘧达莫片的含量测定及含量均匀度研究 预览
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作者 李宇 田海燕 +1 位作者 崔晓雨 刘洪海 《中国药业》 CAS 2019年第18期27-29,共3页
目的建立测定阿司匹林双嘧达莫片含量的紫外分光光度法,并测定含量均匀度。方法双嘧达莫层的溶剂为0. 1 mol/L的盐酸溶液,测定波长为284 nm;阿司匹林层的溶剂为pH 6. 8的磷酸盐缓冲液,测定波长为266 nm;测定含量。以小杯法测定含量均匀... 目的建立测定阿司匹林双嘧达莫片含量的紫外分光光度法,并测定含量均匀度。方法双嘧达莫层的溶剂为0. 1 mol/L的盐酸溶液,测定波长为284 nm;阿司匹林层的溶剂为pH 6. 8的磷酸盐缓冲液,测定波长为266 nm;测定含量。以小杯法测定含量均匀度。结果双嘧达莫质量浓度在4~32μg/mL范围内与吸光度线性关系良好(r=0. 999 7,n=7),平均回收率为100. 68%,RSD=0. 33%(n=9);阿司匹林质量浓度在60~240μg/mL范围内与吸光度线性关系良好(r=0. 999 8,n=7),平均回收率为100. 25%,RSD=0. 42%(n=9)。小杯试验3批样品的A+2. 2 S分别为6. 1,7. 2,6. 7。结论该方法简便、快速、准确,可测定阿司匹林双嘧达莫片含量,且制剂含量均匀度较好。 展开更多
关键词 紫外分光光度法 阿司匹林双嘧达莫片 含量 含量均匀度
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Effects of spring fire and slope on the aboveground biomass, and organic C and N dynamics in a semi-arid grassland of northern China 预览
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作者 ZHAO Xiang HU Shuya +4 位作者 DONG Jie REN Min ZHANG Xiaolin DONG Kuanhu WANG Changhui 《干旱区科学:英文版》 SCIE CSCD 2019年第2期267-279,共13页
The aboveground primary production is a major source of carbon(C) and nitrogen(N) pool and plays an important role in regulating the response of ecosystem and nutrient cycling to natural and anthropogenic disturbances... The aboveground primary production is a major source of carbon(C) and nitrogen(N) pool and plays an important role in regulating the response of ecosystem and nutrient cycling to natural and anthropogenic disturbances. To explore the mechanisms underlying the effect of spring fire and topography on the aboveground biomass(AGB) and the soil C and N pool, we conducted a field experiment between April 2014 and August 2016 in a semi-arid grassland of northern China to examine the effects of slope and spring fire, and their potential interactions on the AGB and organic C and total N contents in different plant functional groups(C3 grasses, C4 grasses, forbs, Artemisia frigida plants, total grasses and total plants).The dynamics of AGB and the contents of organic C and N in the plants were examined in the burned and unburned plots on different slope positions(upper and lower). There were differences in the total AGB of all plants between the two slope positions. The AGB of grasses was higher on the lower slope than on the upper slope in July. On the lower slope, spring fire marginally or significantly increased the AGB of C3 grasses, forbs, total grasses and total plants in June and August, but decreased the AGB of C4 grasses and A.frigida plants from June to August. On the upper slope, however, spring fire significantly increased the AGB of forbs in June, the AGB of C3 grasses and total grasses in July, and the AGB of forbs and C4 grasses in August. Spring fire exhibited no significant effect on the total AGB of all plants on the lower and upper slopes in 2014 and 2015. In 2016, the total AGB in the burned plots showed a decreasing trend after fire burning compared with the unburned plots. The different plant functional groups had different responses to slope positions in terms of organic C and N contents in the plants. The lower and upper slopes differed with respect to the organic C and N contents of C3 grasses, C4 grasses, total grasses, forbs, A. frigida plants and total plants in different growing months. Slope p 展开更多
关键词 ABOVEGROUND biomass plant functional group SPRING FIRE SLOPE position N CONTENT organic C CONTENT SEMI-ARID grassland
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Is seawater geochemical composition recorded in marine carbonate? Evidence from iron and manganese contents in Late Devonian carbonate rocks
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作者 Zhe Wang Wen Guo +4 位作者 Ting Nie Haoran Ma Tianzheng Huang Yuanlin Sun Bing Shen 《中国地球化学学报:英文版》 EI CAS CSCD 2019年第2期173-189,共17页
Iron and manganese are the important redoxsensitive elements in the ocean.Previous studies have established a series of paleo-depositional redox proxies based on the form and content of iron in sedimentary rocks(e.g.,... Iron and manganese are the important redoxsensitive elements in the ocean.Previous studies have established a series of paleo-depositional redox proxies based on the form and content of iron in sedimentary rocks(e.g.,degree of pyritization,FeHR/FeT,Fe/Al).These proxies were developed and applied on siliciclastic-rich marine sediments.Although marine carbonate rocks are generally considered to preserve the geochemical signals of ancient seawater,neither Fe nor Mn content in marine carbonate rocks(Fecarb,Mncarb)has been independently used as a proxy to quantify environmental cues in paleo-oceans.Both Fe and Mn are insoluble in oxic conditions(Fe2O3,Fe(OH)3,MnO2),while their reduced forms(Fe^2+and Mn^2+)are soluble.Therefore,oxic seawater should have low concentrations of dissolved Fe^2+and Mn^2+,and accordingly carbonate rocks precipitated from oxic seawater should have low Fecarband Mncarb,and vice versa.To evaluate whether Fecarband Mncarbcan be used to quantify oxygen fugacity in seawater,we measured Fecarband Mncarbof Upper Devonian marine carbonate rocks collected from nine sections in South China.Fecarbof intraplatform basin samples wassignificantly higher than that of shelf samples,while shelf and basin samples had comparable Mncarb.The modeling result indicates that the dramatic difference in Fecarbcannot be explained by variation in oxygen fugacity between the shelf and basin seawater.Instead,both Fecarband Mncarb appear to be more sensitive to benthic flux from sediment porewater that is enriched in Fe2+and Mn^2+.Porewater Fe^2+and Mn^2+derive from bacterial iron and manganese reduction;flux was controlled by sedimentation rate and the depth of the Fe(Mn)reduction zone in sediments,the latter of which is determined by oxygen fugacity at the water–sediment interface.Thus,high Fecarbof the basin samples might be attributed to low sedimentation rate and/or low oxygen fugacity at the seafloor.However,invariant Mncarbof the shelf and basin samples might be the consequence of complete reduction of Mn in sedim 展开更多
关键词 CARBONATE ROCKS Fe CONTENT Mn CONTENT Oxygen FUGACITY BENTHIC flux
硫酸沙丁胺醇雾化吸入溶液冻融稳定性研究 预览
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作者 毛毅斌 徐欣 +1 位作者 刘哲鹏 孙涛 《广东化工》 CAS 2019年第9期97-98,96共3页
为了使硫酸沙丁胺醇雾化吸入液在运输以及存储条件下有更好的稳定性,本研究采用反复冻融法考察了硫酸沙丁胺醇雾化吸入液冻融稳定性。将硫酸沙丁胺醇雾化吸入液置于冰箱(-10℃至-20℃)内放置两天,取出后再放入40℃稳定箱内两天,三次循... 为了使硫酸沙丁胺醇雾化吸入液在运输以及存储条件下有更好的稳定性,本研究采用反复冻融法考察了硫酸沙丁胺醇雾化吸入液冻融稳定性。将硫酸沙丁胺醇雾化吸入液置于冰箱(-10℃至-20℃)内放置两天,取出后再放入40℃稳定箱内两天,三次循环后取出,放置室温,观察其外观性状并检测其含量及有关物质变化。结果显示其外观性状,pH,含量以及有关物质等检查项均符合标准,溶液稳定性良好。硫酸沙丁胺醇雾化吸入液在运输以及冻融条件下有较好的稳定性。 展开更多
关键词 硫酸沙丁胺醇 冻融 含量 有关物质
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营林技术对林业的重要性探究 预览
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作者 董智娇 《现代农业研究》 2019年第8期68-69,共2页
提高营林管理质量,推动林业可持续发展是一项长期系统的项目工程,因此,林业机构人员要创新理念,更新转变林业工作方式,完善林业机制,增强林业管理实效,为提高林业可持续发展奠定基础,本文从林业管理方面的建设内容与要素开始详细介绍,... 提高营林管理质量,推动林业可持续发展是一项长期系统的项目工程,因此,林业机构人员要创新理念,更新转变林业工作方式,完善林业机制,增强林业管理实效,为提高林业可持续发展奠定基础,本文从林业管理方面的建设内容与要素开始详细介绍,再对林业管理中出现的问题与现状进行分析研究,最后深入探讨与研究林业管理对林业系统可持续发展采取的对策及建议。 展开更多
关键词 林业管理 可持续发展 内容 问题 对策
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社会网络分析及其在考古学研究中的应用
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作者 陆青玉 栾丰实 王芬 《东南文化》 CSSCI 北大核心 2019年第5期14-20,共7页
考古学社会网络分析的发展可分为三个阶段,目前正处于繁荣期,在我国的考古学研究中具有巨大的应用潜力。它以抽象的节点和连线构成的网络来模拟古代各种社会关系,尤其注重对物质文化交流、社会结构的时空变化等相关问题的探讨,为全面解... 考古学社会网络分析的发展可分为三个阶段,目前正处于繁荣期,在我国的考古学研究中具有巨大的应用潜力。它以抽象的节点和连线构成的网络来模拟古代各种社会关系,尤其注重对物质文化交流、社会结构的时空变化等相关问题的探讨,为全面解读古代社会提供了一种新的视角。同时,在静态的网络数据与动态的历史事实之间的对接等方面,我们目前的研究还需要注意一些问题。 展开更多
关键词 考古学 社会网络分析 内容 步骤 应用
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