期刊文献+
共找到11,646篇文章
< 1 2 250 >
每页显示 20 50 100
Institutional Determinants to Climate Variability Adaptation by Smallholder Irish Potato Farmers in Rubanda District, South Western Uganda 预览
1
作者 Frank Mugagga Julius Elepu +1 位作者 Alex Nimusiima Yazidhi Bamutaze 《美国气候变化期刊(英文)》 2019年第1期77-93,共17页
Climate variability and change pose greater challenge not only to human life but to the environment at large. This study sought to evaluate the significance of institutional factors in climate variability adaptation o... Climate variability and change pose greater challenge not only to human life but to the environment at large. This study sought to evaluate the significance of institutional factors in climate variability adaptation of smallholder Irish potato farmers in Rubanda District, South Western Uganda with the objective of assessing the adaptation measures adopted by smallholder Irish potato farmers, determining the institutional factors that influence adoption of climate variability adaptation measures;and evaluating the institutional challenges that affect the adapting Irish potato farmers. A cross-sectional survey was undertaken to collect data from 197 systematically sampled smallholder farmers from two purposively selected sub counties (Muko and Bubaare) in Rubanda District, using structured questionnaires;whilst key informant interviews were used to elicit data from purposively selected personnel from the local government as well as private and civil society organizations. Multiple linear regression was used to determine the relative influence of selected variables on adaptation measures against climate variability. Results indicate that smallholder Irish potato farmers are adapting to climate variability through agronomic measures such as terracing, mulching, contour ploughing, changing planting dates, early planting, crop-rotation, and technology related measures such as rain water harvesting technologies, adaptive varieties and fertilizers among others. Results from multiple linear regression analysis show that several institutional factors are influencing adoption of climate variability adaptive measures with the most significant ones being access to agricultural extension services, cultivated area and size of land owned. Despite the interventions undertaken, adaptation to climate variability is constrained by the limited access to financial/credit resources and inadequate technical capacity as well as limited access to information and irregularity of extension services. The study recommends that public and priv 展开更多
关键词 ADAPTATION Climate Variability INSTITUTIONAL Factors SMALLHOLDER FARMERS SOUTH WESTERN Uganda
在线阅读 免费下载
Living with Climate Change: Assessment of the Adaptive Capacities of Smallholders in Central Rift Valley, Ethiopia 预览
2
作者 Zenebe Mekonnen Habtemariam Kassa 《美国气候变化期刊(英文)》 2019年第2期205-227,共23页
Farms less than 2 hectares have constituted almost 90% of the total number of farms in Ethiopia. These small farms are rain fed and are vulnerable to climate change and variability extremes such as droughts. This in t... Farms less than 2 hectares have constituted almost 90% of the total number of farms in Ethiopia. These small farms are rain fed and are vulnerable to climate change and variability extremes such as droughts. This in turn undermined the ability of smallholders’ farmers to feed themselves and the growing population. A questionnaire survey was conducted with a random sample of 355 smallholder farmers distributed in three agro-ecologies, namely, lowland, midland, and highland in central rift valley of Ethiopia (Arsi Negele district). This was supplemented with 18 focus group discussions and 30 key informant interviews. How do smallholder farmers live with climate change and variability challenges? On the basis of this question, this study has assessed the factors that determine the adaptive capacities, strategies and livelihoods of smallholders to climate change and variability;and the role of climate capacities and landscape functions for sustainable adaptation in response to climate change and variability. The results showed that even if most respondents (>95%) have the perception and intention of climate change;it was nearly 3% of them have higher adaptive capacity to adapt to climate change impacts. Adaptive capacity of smallholders and the potential impact exerted by climate change risks were negatively correlated (r = &#8722;0.134 and p < 0.02). The results showed that farmers have made some evolution in their livelihoods as an adaptation strategy. Adaptation strategies explicitly depend on adaptive capacity-human, natural, financial, social and physical resources. Indeed, the results indicated limited climate-specific and climate-relevant capacities at the local level which suggests a need to strengthen climate capacities. Moreover, it has been implicated that maintaining the landscapes, which provide landscape production functions that build the well-being and adaptive capacity of farmers, could help to sustain farmers’ livelihood and build their adaptive capacity to withstand the challenges of climate ch 展开更多
关键词 ADAPTATION Climate Capacity INCOME INEQUALITY Potential Impacts Landscapes Functions SMALLHOLDER
在线阅读 免费下载
Traditional Selection Criteria of Ogaden Cattle in Pastoral and Agro Pastoral Production Systems and Its Implication to Resilience of the Breed in the Face of Climate Change in the Future 预览
3
作者 Yesihak Yusuf Mummed 《动物科学期刊(英文)》 2019年第3期355-366,共12页
Selecting for adapted livestock breeds that will produce at optimum in the anticipated climate change scenario is one way of sustaining the production system. Africa has accumulated indigenous knowledge to coping up w... Selecting for adapted livestock breeds that will produce at optimum in the anticipated climate change scenario is one way of sustaining the production system. Africa has accumulated indigenous knowledge to coping up with climate variability in the past. It is common practice to shift to livestock agriculture as climate becomes less predicted in Africa. Cattle contribute more than 80% of meat and milk in Ethiopia. The aim of this paper was to identify traditional selection criteria of Ogaden cattle breed in pastoral and agro pastoral production systems and suggest possible intervention strategies. Questionnaire survey was conducted in Wabeshebele Zone of Ethiopia, in three districts based on cattle population and accessibility on 126 households. The results of the study revealed that farmers preferred to own diversified livestock species to cope up with unpredicted climate. Milk production and body conformation were ranked first and second criteria in selecting female which were followed by adaptive characteristics such as coat color, fertility and longevity, respectively, while in male, adaptive characters such as hump size, body conformation, coat color and fertility were given priority over milk production. Selection criteria of cattle practiced in the society strongly favored adaptation and ability to perform in feed constraint environment in addition to meat, milk and fertility. However, the simplest reproductive biotechnology, AI, was rarely practiced in the study area. It was recommended that indigenous knowledge of the society on selection criteria of the cattle breed need to be integrated with utilization of assisted reproductive biotechnologies and on farm research innovations on the breed so far acquired in any improvement program of the breed in the future. 展开更多
关键词 Ogaden CATTLE TRADITIONAL Selection Criteria Adaptation
在线阅读 免费下载
Polarization Filtering Method for Suppressing Surface Wave in Time-Frequency Domain 预览
4
作者 Xiaoming Yang Yang Gao +2 位作者 Wenzhong Zhang Yanchun Wang Meihua Lan 《地球科学国际期刊(英文)》 2019年第4期481-490,共10页
In order to suppress the surface wave in three-component seismic exploration, according to the polarization characteristics of body wave and surface wave, a time-frequency domain polarization filtering method based on... In order to suppress the surface wave in three-component seismic exploration, according to the polarization characteristics of body wave and surface wave, a time-frequency domain polarization filtering method based on wavelet transform was studied. A covariance matrix was constructed in the time-frequency domain for the three-component seismic data, measured the polarization parameters of seismic waves. Combining the corresponding eigenvalues and eigenvectors of the matrix, the elliptic rate and elevation angle were used as constraints, and the polarization filter function was built to separate the surface waves. The separated surface waves were inversely transformed and then were adaptively subtracted from the original records. After the polarization filtering suppressed the surface wave, the signal-to-noise ratio of the converted wave was effectively improved. It laid a good foundation for the next seismic data processing and seismic exploration development. The actual data processing results show that the method can effectively extract surface waves from three-component seismic records and avoid the interference of surface waves on seismic signals. 展开更多
关键词 THREE-COMPONENT SEISMIC Data Surface WAVE POLARIZATION FILTERING ADAPTATION
在线阅读 免费下载
Anatomical Structure of Vegetative and Generative Organs of <i>Silybum marianum</i>(L.) Gaertn. (Fam. Asteraceae) 预览
5
作者 B. A. Nigmatullaev G. M. Duschanova +1 位作者 B. A. Abdurahmonov G. B. Sotimov 《美国植物学期刊(英文)》 2019年第1期38-43,共6页
The article provides information about the anatomical structure of the vegetative and generative organs grown in Tashkent conditions, and reveals the structural features: a mesomorphic leaf, a dorsi-central mesophyll ... The article provides information about the anatomical structure of the vegetative and generative organs grown in Tashkent conditions, and reveals the structural features: a mesomorphic leaf, a dorsi-central mesophyll type characteristic of dicotyledonous plants;stem beam type. A comparative analysis of the anatomical structure showed that the seed coat has a general plan of the structure with other members of the family Asteraceae. 展开更多
关键词 Silybum marianum Anatomical Structure Leaf Fruit Adaptation
在线阅读 免费下载
Forests Policies and Programmes in India: Implications for Climate Change Adaptation 预览
6
作者 Indu K. Murthy Poornima Kumar 《林学期刊(英文)》 2019年第3期226-240,共15页
Climate change is a major global environmental and developmental challenge and climate proofing of vulnerable sectors, programmes, natural systems and communities by integrating adaptation and mitigation options into ... Climate change is a major global environmental and developmental challenge and climate proofing of vulnerable sectors, programmes, natural systems and communities by integrating adaptation and mitigation options into planning process are increasingly becoming an integral part of development. The basic premises on which this could happen are the national and sectoral policies that govern any programmes and actions implemented on ground. This study reviews existing policies, plans and programmes and their implications for climate change. Based on the analyses, key areas of research, policy initiatives and institutional and capacity development needs have been identified, to facilitate climate change adaptation. The forest policies formulated so far in India have been broadly aimed at conservation, reduction of pressure on forests and provisioning of biomass to the large forest dependent population for their fuel and fodder needs apart from generating revenue through production and sale of timber. However, these have not been formulated with climate change as a consideration and therefore may become less effective as climate change and its impacts become increasingly evident. The study clearly identifies that the current policies and programmes have elements/features and activities that directly or indirectly contribute positively towards adaptation, although the primary implications are towards biodiversity and to some extent ecosystem functioning. It finally highlights the need for incorporating climate change concerns in forest sector development programmes and also to address the issue of climate change. 展开更多
关键词 FOREST Sector CLIMATE Change Adaptation FOREST POLICIES PROGRAMMES CLIMATE VARIABILITY
在线阅读 免费下载
《巴黎协定》“适应”制度评析 预览
7
作者 许健 钱林 《太原理工大学学报:社会科学版》 2019年第2期41-48,共8页
2015年通过的《巴黎协定》第七条及其相关规定设立了“适应”制度的大致框架,规定了全球适应目标、国际社会在“适应”领域的合作与支持,以及国家驱动为主的“适应”模式,极大地推动了“适应”在国际环境立法中的发展。然而《巴黎协定... 2015年通过的《巴黎协定》第七条及其相关规定设立了“适应”制度的大致框架,规定了全球适应目标、国际社会在“适应”领域的合作与支持,以及国家驱动为主的“适应”模式,极大地推动了“适应”在国际环境立法中的发展。然而《巴黎协定》中“适应”制度存在着全球适应目标模糊、资金分配失衡、追踪机制框架化等问题,影响着“适应”制度的实施效果。对此,有必要以国家自主贡献为依托,通过平衡“减缓”与“适应”资金分配等方式完善“适应”制度。此外,中国应当重视与《巴黎协定》“适应”制度的衔接,积极开展“适应”行动。 展开更多
关键词 “适应” 《巴黎协定》 全球适应目标 国际合作 国家驱动 中国应对
在线阅读 下载PDF
Addressing Climate Change Vulnerability in Alaska Native Villages Through Indigenous Community Knowledge 预览
8
作者 Elizaveta Barrett Ristroph 《社会学研究:英文版》 2019年第1期1-19,共19页
From a Western standpoint, Alaska Native Villages (ANVs) and other indigenous groups have a particular vulnerability to climate change. At the same time, these groups may be seen by themselves and Westerners as having... From a Western standpoint, Alaska Native Villages (ANVs) and other indigenous groups have a particular vulnerability to climate change. At the same time, these groups may be seen by themselves and Westerners as having particular knowledge that can help them adapt to climate change. This paper explores how ANVs are vulnerable to climate change and considers factors such as colonization that aggravate this vulnerability. It then explores how indigenous community knowledge may reduce vulnerability and facilitate adaptation and resilience. It concludes that indigenous community knowledge alone is insufficient to support adaptation and resilience, given the degree of social, political, and climate change, so long as Western institutions privilege Western science over other forms of knowledge. That said, indigenous community knowledge should inform agency decision-making and development projects and may serve as cultural capital that can support resilience. The desire to use indigenous knowledge may be a proxy for a larger issue—the need to include indigenous communities in decision-making about climate change. 展开更多
关键词 Alaska NATIVE VILLAGES ndigenous KNOWLEDGE CLIMATE change ADAPTATION VULNERABILITY
在线阅读 下载PDF
重金属超积累植物及其进化:事实与争议
9
作者 曾超珍 严明理 刘志祥 《植物生理学报》 CAS CSCD 北大核心 2019年第8期1063-1074,共12页
土壤重金属污染是全球性的环境问题。重金属超积累植物(超富集植物)在土壤重金属污染修复中具有广阔的应用前景,同时也是研究植物对极端环境适应与进化的良好模型。目前关于重金属超积累植物及其进化在如下三方面仍存在诸多争议与矛盾:... 土壤重金属污染是全球性的环境问题。重金属超积累植物(超富集植物)在土壤重金属污染修复中具有广阔的应用前景,同时也是研究植物对极端环境适应与进化的良好模型。目前关于重金属超积累植物及其进化在如下三方面仍存在诸多争议与矛盾:一、重金属超积累植物的界定;二、植物重金属超积累性状与超耐受性状的关系;三、植物超积累重金属的适应性意义。植物对重金属的耐受和积累机制复杂多样,而QTL分析、比较基因组学等方法的应用将最终揭示植物超积累重金属的生理、遗传与进化机制。 展开更多
关键词 重金属 超积累 超耐受 进化 适应性
VANET中基于捎带确认机制的自适应数据传播策略 预览 被引量:1
10
作者 赵金龙 张娓娓 陈绥阳 《计算机应用研究》 CSCD 北大核心 2019年第6期1858-1862,1872共6页
车载自组网(VANET)通过自组织分散环境传播交通数据,交通数据的特点使得VANET数据传播方法更适合依赖广播。然而,当在高密度场景下广播数据时,可扩展问题和数据传播冗余问题变得尤为突出,可能导致广播风暴的发生。针对数据传播冗余和广... 车载自组网(VANET)通过自组织分散环境传播交通数据,交通数据的特点使得VANET数据传播方法更适合依赖广播。然而,当在高密度场景下广播数据时,可扩展问题和数据传播冗余问题变得尤为突出,可能导致广播风暴的发生。针对数据传播冗余和广播开销等问题,以最远转发策略和捎带确认机制为基础,提出一种捎带确认的自适应最远转发策略(AckAMFR),根据存储转发的概念进行信息的传输和存储,降低了数据冗余,具有较强的可靠性和较小的广播开销。仿真结果表明,该转发策略具有低广播开销和高数据传输率的特性。 展开更多
关键词 车载自组网 捎带确认 自适应 数据冗余 存储转发
在线阅读 下载PDF
感应与调适:元明易代两起祥瑞的文学意义发微
11
作者 饶龙隼 《复旦学报:社会科学版》 CSSCI 北大核心 2019年第4期85-94,共10页
世当元明易代鼎革之际,两起祥瑞同时异地并出,颇引起东南士绅的关注,亦激发相关叙咏与解读。其一,至正二十年(1360)春某月日,在西昌石塘萧氏故居之旧址,于蓬蒿瓦砾中突产瑞芝二本;其二,也正是在这一年春二月某日,金华硕儒宋濂应聘将赴金... 世当元明易代鼎革之际,两起祥瑞同时异地并出,颇引起东南士绅的关注,亦激发相关叙咏与解读。其一,至正二十年(1360)春某月日,在西昌石塘萧氏故居之旧址,于蓬蒿瓦砾中突产瑞芝二本;其二,也正是在这一年春二月某日,金华硕儒宋濂应聘将赴金陵,临行前自占得'文物之祥'。透过这两起祥瑞之表象,可考见其文学意义迥异:前者,表征为西昌十名贤对文明发祥的感应,而在明初政治高压下有更强的适应性;后者,表征为浙东文人入明后的文学观调适,而在明初政治高压下缺乏更强的适应性。正因为得益于自身更强的适应性,西昌文人在政治高压下保有后劲,而将西昌雅正文学接引入馆阁,后又将馆阁文学风范推广到朝野;也正是受累于自身更弱的适应性,浙东文人在政治高压下缺乏后劲,因使其调适过的文学观不合时用,最终导致浙东文学传统顿然消歇。 展开更多
关键词 萧氏瑞芝 文物之祥 感应 调适 文学意义 发微
盾构推进姿态控制策略研究 预览
12
作者 任颖莹 孙振川 褚长海 《隧道建设(中英文)》 北大核心 2019年第6期1038-1044,共7页
为提高盾构施工过程中姿态控制系统的控制精度和控制性能,提出一种盾构推进姿态控制策略。该策略将轨迹自动跟踪控制方法与模糊自适应PID闭环控制算法相结合,通过轨迹、位移、压力等多个闭环反馈实现对各个分区液压缸的速度控制,保证盾... 为提高盾构施工过程中姿态控制系统的控制精度和控制性能,提出一种盾构推进姿态控制策略。该策略将轨迹自动跟踪控制方法与模糊自适应PID闭环控制算法相结合,通过轨迹、位移、压力等多个闭环反馈实现对各个分区液压缸的速度控制,保证盾构推进轨迹按照设计的隧道轴线运行,并通过电液控制试验平台中的推进系统对提出的策略进行试验验证。结果表明,文章提出的控制策略能够使位移偏差维持在5 mm之内,可以很好地满足施工要求。 展开更多
关键词 盾构 推进系统 姿态控制 自适应 轨迹跟踪控制
在线阅读 下载PDF
高原适应遗传学缺氧诱导因子通路相关基因及其药理学研究进展
13
作者 贺启莲 格日力 +1 位作者 李占强 芦殿香 《药学学报》 CAS CSCD 北大核心 2019年第4期611-619,共9页
人类对高原缺氧环境的适应表现、机制及相关药理学研究一直是科研探索的热点。一个世纪以来,主要集中于青藏高原、南美洲安第斯高原和埃塞俄比亚高原的高原世居人群对于慢性缺氧所具有的独特生理适应已经得到了科学验证,而近10年来的基... 人类对高原缺氧环境的适应表现、机制及相关药理学研究一直是科研探索的热点。一个世纪以来,主要集中于青藏高原、南美洲安第斯高原和埃塞俄比亚高原的高原世居人群对于慢性缺氧所具有的独特生理适应已经得到了科学验证,而近10年来的基因研究也证实高原适应具有遗传学基础,尤其与缺氧诱导因子(hypoxia inducible factor,HIF)通路及缺氧反应基因(hypoxia response elements,HREs)具有密切关系。但有趣的是,对高原缺氧的适应表现和遗传机制在上述三大高原世居人群中却并不完全相同,其中西藏人具有更好的高原适应表现,并且HIF通路是其最关键的适应机制。同时,由于HIF通路涉及广泛,可调节数以百计的下游基因表达,并与癌症、炎症、缺血、急性脏器损伤和感染等多种疾病密切相关,因此HIF通路的激活剂和抑制剂研究也取得了很大进展。本文就三大高原世居人群对高原环境的不同适应反应、HIF及HREs在不同种族高原适应中的遗传学作用机制、HIF通路的药理学研究进展进行了综述,以期为高原低氧遗传性适应及HIF相关性疾病的进一步研究提供参考。 展开更多
关键词 缺氧 高原 适应 缺氧诱导因子 脯氨酸羟化酶
Multispecies hybridization in birds 预览
14
作者 Jente Ottenburghs 《鸟类学研究:英文版》 CSCD 2019年第3期239-249,共11页
Hybridization is not always limited to two species;often multiple species are interbreeding. In birds, there are numerous examples of species that hybridize with multiple other species. The advent of genomic data prov... Hybridization is not always limited to two species;often multiple species are interbreeding. In birds, there are numerous examples of species that hybridize with multiple other species. The advent of genomic data provides the oppotunity to investigate the ecological and evolutionary consequences of multispecies hybridization. The interactions between several hybridizing species can be depicted as a network in which the interacting species are connected by edges. Such hybrid networks can be used to identify ‘hub-species’ that interbreed with multiple other species. Avian examples of such ‘hub-species’ are Common Pheasant (Phasianus colchicus), Mallard (Anas platyrhynchos) and European Herring Gull (Larus argentatus). These networks might lead to the formulation of hypotheses, such as which connections are most likely conducive to interspecific gene flow (i.e. introgression). Hybridization does not necessarily result in introgression. Numerous statistical tests are available to infer interspecific gene flow from genetic data and the majority of these tests can be applied in a multispecies setting. Specifically, model-based approaches and phylogenetic networks are promising in the detection and characterization of multispecies introgression. It remains to be determined how common multispecies introgression in birds is and how often this process fuels adaptive changes. Moreover, the impact of multispecies hybridization on the build-up of reproductive isolation and the architecture of genomic landscapes remains elusive. For example, introgression between certain species might contribute to increased divergence and reproductive isolation between those species and other related species. In the end, a multispecies perspective on hybridization in combination with network approaches will lead to important insights into the history of life on this planet. 展开更多
关键词 Adaptation ADMIXTURE Genomics INTROGRESSION Network analysis PHYLOGENETICS SPECIATION
在线阅读 免费下载
软刺裸鲤和齐口裂腹鱼肌肉和骨骼中的元素分析
15
作者 武晓会 刘洋 许强华 《中国农业科技导报》 CAS CSCD 北大核心 2019年第11期163-169,共7页
软刺裸鲤(Gymnocypris doubula)和齐口裂腹鱼(Schizothorax prenanti)分别是生长在高海拔(>4 500 m)低氧的青藏高原水体和低海拔(<1 000 m)长江上游水体的两种裂腹鱼亚科鱼类。为探究不同海拔裂腹鱼体内微量元素的差异,采用微波... 软刺裸鲤(Gymnocypris doubula)和齐口裂腹鱼(Schizothorax prenanti)分别是生长在高海拔(>4 500 m)低氧的青藏高原水体和低海拔(<1 000 m)长江上游水体的两种裂腹鱼亚科鱼类。为探究不同海拔裂腹鱼体内微量元素的差异,采用微波消解电感耦合等离子体质谱(ICP-MS)法测定软刺裸鲤(GD)和齐口裂腹鱼(SP)肌肉、脊椎骨和头盖骨中Na、Mg、Al、K、Ca、Fe、Zn等常量元素和V、Cr、Mn、As、Se、Sr、Sb、Ba等微量元素含量,并对两种裂腹鱼的元素含量进行差异比较和分析。结果表明,GD和SP肌肉中仅有Se和Sb含量呈现显著性差异,仅有As含量在两种裂腹鱼的脊椎骨中存在显著差异。GD肌肉中极高含量的Se和Sb元素、以及GD脊椎骨中极高含量的As元素可能与高原低氧适应相关。该研究在国内首次使用微波消解法对两种不同海拔高度的裂腹鱼肌肉和骨骼中的常量元素和微量元素进行测定分析,有效探究了两种裂腹鱼体内元素的差异,为后续通过体内组织的元素分析来解析裂腹鱼适应低氧环境的生理机制提供依据。 展开更多
关键词 软刺裸鲤 齐口裂腹鱼 元素含量 低氧环境 适应
油松地理种群针叶形态解剖与生理指标遗传变异分析
16
作者 陈新宇 孟景祥 +3 位作者 周先清 袁虎威 钮世辉 李悦 《北京林业大学学报》 CAS CSCD 北大核心 2019年第7期19-30,共12页
【目的】针叶作为松树生命活动的重要器官,其不同地理种群的形态解剖特征与生理指标的关联尚待阐明,两者间联系可以为认识油松适应性变异提供新的视角。【方法】本研究在对来自油松全分布区不同生境的8个地理种群田间对比试验基础上,分... 【目的】针叶作为松树生命活动的重要器官,其不同地理种群的形态解剖特征与生理指标的关联尚待阐明,两者间联系可以为认识油松适应性变异提供新的视角。【方法】本研究在对来自油松全分布区不同生境的8个地理种群田间对比试验基础上,分析了4年生苗木次生针叶形态解剖指标、蒸腾与光合生理指标变异及两类指标间的相关关系。【结果】(1)针叶粗细、维管束、气孔和树脂道指标在地理群体间存在显著遗传变异;(2)各生理指标在地理种群间有极显著遗传差异;(3)针叶的净光合速率、蒸腾速率和胞间CO2浓度与形态解剖指标均存在不同紧密程度的正相关;(4)种群的胞间CO2浓度与产地年降水和1月均温与年降水比值呈显著正相关,气孔限制值与年降水量和1月均温/年降水量成显著负相关;(5)种群针叶的气孔线数与经度成显著正相关,而树脂道数与经度显著负相关,但与海拔成显著正相关;树脂道面积和叶肉面积比值与经度和纬度成显著负相关。【结论】遗传相对稳定的针叶形态解剖指标差异可在一定程度上反映地理种群间的光合生理差异,种群间存在针叶气孔量和调节能力随降水量及其维持力减低而提高趋势,树脂道数量及相对截面积随降水量降低而降低的适应性进化趋势。该发现为认识针叶形态解剖特性与光合生理指标关系,松种的适应性进化以及遗传改良提供了理论参考。 展开更多
关键词 地理种群 针叶形态解剖 光合生理 遗传变异 适应性 油松
气候变化对农业水管理的影响及应对策略研究 预览
17
作者 许迪 李益农 +1 位作者 龚时宏 张宝忠 《农业工程学报》 EI CAS CSCD 北大核心 2019年第14期79-89,共11页
气候变化导致全球年平均气温上升、降水模式变化、河流特性改变、极端气候事件频发等,显现出其对农业水资源和农业生产造成的影响,使全球尤其是干旱和半干旱地区可持续农业发展和现代农业水管理面临重大挑战。该文介绍气候变化下的极端... 气候变化导致全球年平均气温上升、降水模式变化、河流特性改变、极端气候事件频发等,显现出其对农业水资源和农业生产造成的影响,使全球尤其是干旱和半干旱地区可持续农业发展和现代农业水管理面临重大挑战。该文介绍气候变化下的极端气候事件发生,评价气候变化通过气温和降水的改变以及极端气候事件频度和程度加剧等各种方式对农业用水可利用量和水质以及作物需水造成的影响,阐述气候变化通过水要素对灌溉用水、可用耕地、作物产量带来的影响,综述气候变化对农业水管理的影响及应对策略,提出在气候变化对农业水管理的影响及应对策略研究上,应认真考虑气候变化对农业水管理影响的尺度效应和不确定性,从而有助于因地制宜地制定和合理选用农业水管理应对策略;应积极构建基于多模型集成模式的气候变化对农业水管理影响的综合评估方法,从而有利于改善综合预测评估结果的准确性和可靠性;应深入进行农业水管理应对策略的适应-减缓利弊权衡研究和协同效用分析,从而有效改进和提高应对策略的效用。建议国内应该加强对综合评估方法和效用分析的研究力度。 展开更多
关键词 气候变化 农业 水资源 农业水管理 农业生产 应对策略 适应 减缓
在线阅读 下载PDF
BCRH-15D型现场混装乳化炸药车改进 预览
18
作者 王晓峰 《广东化工》 CAS 2019年第2期134-135,151共3页
通过对BCRH-15D型现场混装乳化炸药车的"水环"、静态混合器、装药计量系统、电控系统等的改进,满足了安全技术要求,提高了整车对作业环境的适应性,从而满足了市场需求。
关键词 现场混装车改进 适应 安全要求 市场需求
在线阅读 下载PDF
不同海拔高度农牧民气候变化及其影响感知差异分析 预览
19
作者 梅江梅 周尧治 《高原农业》 2019年第1期108-116,共9页
本研究通过问卷调查山南市不同海拔高度的农牧民对气候变化及其影响的感知,并通过计算其相对感知强度,探究不同海拔高度农牧民气候变化及其影响的感知差异,并因地制宜地提出适应气候变化的措施。结果表明:(1)山南市绝大部分农牧民感知... 本研究通过问卷调查山南市不同海拔高度的农牧民对气候变化及其影响的感知,并通过计算其相对感知强度,探究不同海拔高度农牧民气候变化及其影响的感知差异,并因地制宜地提出适应气候变化的措施。结果表明:(1)山南市绝大部分农牧民感知到气候变化,不同海拔高度的农牧民对本地气候变化的感知存在差异。农牧民对夏季升温、过去与现在气候对比方两方面,相对感知强度很高,而且基本随着海拔高度的升高而增强。这表明海拔高度是影响农牧民对气候变化感知一个重要因素。(2)不同海拔高度的农牧民一致认为可利用水源发生了变化,且随海拔升高,认为可利用水源减少的农牧民增多,变化的时间大致在2011年以后。这与国家气象信息中心数据显示的山南市降水量从2010年开始至今持续低于多年平均值相吻合。(3)政府应建立防灾减灾体系,拓展当地的产业格局,根据不同海拔村庄的气候环境制定相宜的适应计划,积极利用气候变化带来的潜在利益,减少气候变化带来的损失。 展开更多
关键词 气候变化 感知 适应 不同高度 差异分析 西藏
在线阅读 免费下载
基于语言顺应论的英语阅读教学模式 预览
20
作者 张晓丽 《大学英语教学与研究》 2019年第1期3-6,共4页
本文基于语言顺应论和英语阅读过程的本质,提出了顺应性英语阅读教学模式。作者把阅读过程分为读前、读中和读后三个阶段,在阅读过程中,教师应该引导学生从词汇、句子、语篇方面顺应文章的语言结构;从作者的心理世界、文本的社会和文化... 本文基于语言顺应论和英语阅读过程的本质,提出了顺应性英语阅读教学模式。作者把阅读过程分为读前、读中和读后三个阶段,在阅读过程中,教师应该引导学生从词汇、句子、语篇方面顺应文章的语言结构;从作者的心理世界、文本的社会和文化背景方面顺应文章的语境。文章旨在帮助学生更好地理解文章,提高阅读理解能力,培养阅读兴趣。 展开更多
关键词 阅读 顺应 语境
在线阅读 下载PDF
上一页 1 2 250 下一页 到第
使用帮助 返回顶部 意见反馈