首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   605篇
  免费   18篇
  国内免费   86篇
安全科学   75篇
废物处理   21篇
环保管理   60篇
综合类   283篇
基础理论   157篇
环境理论   7篇
污染及防治   28篇
评价与监测   9篇
社会与环境   37篇
灾害及防治   32篇
  2024年   1篇
  2023年   17篇
  2022年   14篇
  2021年   32篇
  2020年   27篇
  2019年   20篇
  2018年   29篇
  2017年   53篇
  2016年   46篇
  2015年   39篇
  2014年   60篇
  2013年   100篇
  2012年   25篇
  2011年   28篇
  2010年   18篇
  2009年   11篇
  2008年   7篇
  2007年   15篇
  2006年   18篇
  2005年   16篇
  2004年   20篇
  2003年   28篇
  2002年   19篇
  2001年   10篇
  2000年   5篇
  1999年   5篇
  1998年   5篇
  1997年   4篇
  1996年   2篇
  1995年   9篇
  1994年   3篇
  1993年   3篇
  1992年   2篇
  1991年   2篇
  1990年   2篇
  1989年   4篇
  1988年   1篇
  1987年   4篇
  1986年   1篇
  1985年   1篇
  1983年   1篇
  1977年   2篇
排序方式: 共有709条查询结果,搜索用时 15 毫秒
111.
Conservation translocation is a common method for species recovery, for which one increasingly frequent objective is restoring lost ecological functions to promote ecosystem recovery. However, few conservation translocation programs explicitly state or monitor function as an objective, limiting the ability to test assumptions, learn from past efforts, and improve management. We evaluated whether translocations of hihi (Notiomystis cincta), a threatened New Zealand passerine, achieved their implicit objective of restoring lost pollination function. Through a pollinator-exclusion experiment, we quantified, with log response ratios (lnR), the effects of birds on fruit set and seed quality in hangehange (Geniostoma ligustrifolium), a native flowering shrub. We isolated the contributions of hihi by making comparisons across sites with and without hihi. Birds improved fruit set more at sites without hihi (lnR = 1.27) than sites with hihi (lnR = 0.50), suggesting other avian pollinators compensated for and even exceeded hihi contributions to fruit set. Although birds improved seed germination only at hihi sites (lnR = 0.22–0.41), plants at sites without hihi had germination rates similar to hihi sites because they produced 26% more filled seeds, regardless of pollination condition. Therefore, although our results showed hihi improved seed quality, they also highlighted the complexity of ecological functions. When an important species is lost, ecosystems may be able to achieve similar function through different means. Our results underscore the importance of stating and monitoring the ecological benefits of conservation translocations when functional restoration is a motivation to ensure these programs are achieving their objectives.  相似文献   
112.
兰州市城区冬季TSP容许排放总量的估算   总被引:6,自引:0,他引:6       下载免费PDF全文
利用RAMS大气动力模式模拟的气象场驱动中尺度大气扩散模式HYPACT的方法,模拟出TSP的浓度分布及每个污染单元对于地面浓度的分担率,然后根据TSP的国家质量标准,用线性规划的原理与方法计算了兰州市冬季典型日条件下TSP的大气环境容量.计算结果表明,兰州市全年的主要污染物TSP的大气环境容量远小于排放量,削减率达41.99%左右(2000年12月24日),需要削减的排放量很大.  相似文献   
113.
用ALMANAC作物生长模型模拟冬小麦生长   总被引:7,自引:1,他引:6  
冬小麦是黄淮海地区的主要农作物。精确模拟冬小麦产量能够帮助生产者获得更好的经济效益。根据实验资料调整了ALMANAC作物生长模型部分参数后,用其对该地区的冬小麦生长进行了模拟,结果显示ALMANAC模型能够较好地模拟冬小麦的叶面积指数和产量。叶面积指数的模拟结果与实测结果的比值为1.0552,可决系数R2为0.7021;生物量模拟的最大误差为-6.01%,经济产量模拟的最大误差为-5.41%。模型还可以揭示影响冬小麦生长的主要胁迫因素。  相似文献   
114.
种植密度和降水对冬小麦田N2O排放的影响   总被引:6,自引:2,他引:4  
为研究种植密度对农田N2O排放的影响和探讨N2O排放季节性波动的原因,于1999~2000年小麦生长季在南京市郊江宁县进行了不同播种量(0、90、180和270kg/hm2)的大田试验.观测分析结果表明:在相同的气象条件和田间管理下,播种~越冬阶段的N2O排放不受播种量的影响,返青~成熟阶段的N2O排放通量与播种量成正比.裸地条件下的N2O排放与播量为90kg/hm2下的排放无明显差异.造成该生长季内N2O排放季节性波动的主要原因是降水,返青~成熟阶段的N2O排放通量随观测日前6d的加权平均降水量呈指数增加.  相似文献   
115.
隋立华  黄益宗   《生态毒理学报》2011,6(5):507-514
由于人口的快速增长,人类活动导致近地层O3浓度不断提高,O3浓度升高将对植物、动物和人体健康产生极大的危害.采用开顶式气室(OTC)原位实验方法,研究O3浓度升高对不同生长期冬小麦叶片抗氧化系统的影响,进而分析O3对植物的伤害机制.结果表明,O3浓度升高可导致冬小麦拔节期和抽穗期叶片超氧化物歧化酶(SOD)、过氧化物酶...  相似文献   
116.
Wildlife conservation and management (WCM) practices have been historically drawn from a wide variety of academic fields, yet practitioners have been slow to engage with emerging conversations about animals as complex beings, whose individuality and sociality influence their relationships with humans. We propose an explicit acknowledgement of wild, nonhuman animals as active participants in WCM. We examined 190 studies of WCM interventions and outcomes to highlight 3 common assumptions that underpin many present approaches to WCM: animal behaviors are rigid and homogeneous; wildlife exhibit idealized wild behavior and prefer pristine habitats; and human–wildlife relationships are of marginal or secondary importance relative to nonhuman interactions. We found that these management interventions insufficiently considered animal learning, decision-making, individuality, sociality, and relationships with humans and led to unanticipated detrimental outcomes. To address these shortcomings, we synthesized theoretical advances in animal behavioral sciences, animal geographies, and animal legal theory that may help conservation professionals reconceptualize animals and their relationships with humans. Based on advances in these fields, we constructed the concept of animal agency, which we define as the ability of animals to actively influence conservation and management outcomes through their adaptive, context-specific, and complex behaviors that are predicated on their sentience, individuality, lived experiences, cognition, sociality, and cultures in ways that shape and reshape shared human–wildlife cultures, spaces, and histories. Conservation practices, such as compassionate conservation, convivial conservation, and ecological justice, incorporate facets of animal agency. Animal agency can be incorporated in conservation problem-solving by assessing the ways in which agency contributes to species’ survival and by encouraging more adaptive and collaborative decision-making among human and nonhuman stakeholders.  相似文献   
117.
粉尘是大气气溶胶的主要成分之一,对大气能量平衡起着关键作用。一般来讲,黄土高原(LP)粉尘主要来源于北方沙漠区,但有关中国东部及其周边地区粉尘来源的争论仍在继续。为此,本文对比分析了亚洲主要粉尘源区如中亚(CA)和中蒙(CM)粉尘循环对青藏高原阶段性隆升的响应,探讨了CA和CM粉尘排放对下游的贡献。利用美国大气研究中心(NCAR)最新发布的通用地球系统模式(CESM 1.0),进行了改变青藏高原海拔高度为现在10%,20%,30%?…100%的9个数值试验。分析结果表明,随着青藏高原阶段性隆升中亚和中蒙干旱区冬季降水均线性减弱,与前人研究结果一致。青藏高原阶段性隆升阻塞西风环流使其减弱从而引起中亚粉尘释放减弱;而青藏高原阶段性隆升引起亚洲冬季风加强,促使中蒙粉尘释放加强,与中亚相反。模拟结果与地质记录对比进一步证实了中蒙粉尘源区对黄土高原、中国东部及临近区域粉尘沉降的贡献。  相似文献   
118.
The goal of ecosystem-based management (EBM) is to support a sustainable and holistic multisectored management approach, and is recognized in a number of international policy frameworks. However, it remains unknown how these goals should be linked to assessments and management plans for marine fauna, such as mammals and fish stocks. It appears particularly challenging to carry out trade-off analyses of various ocean uses without a framework that integrates knowledge of environmental, social, and economic benefits derived from nonstationary marine fauna. We argue this gap can be filled by applying a version of the ecosystem-service approach at the population level of marine fauna. To advance this idea, we used marine mammals as a case study to demonstrate what indicators could operationalize relevant assessments and deliver an evidence base for the presence of ecosystem services and disservices derived from marine mammals. We found indicators covering common ecosystem service categories feasible to apply; examples of indicator data are already available in the literature for several populations. We encourage further exploration of this approach for application to marina fauna and biodiversity management, with the caveat that conceptual tensions related to the use of the ecosystem service concept itself needs to be addressed to ensure acceptance by relevant stakeholders.  相似文献   
119.
Carnivore predation on livestock is a complex management and policy challenge, yet it is also intrinsically an ecological interaction between predators and prey. Human–wildlife interactions occur in socioecological systems in which human and environmental processes are closely linked. However, underlying human–wildlife conflict and key to unpacking its complexity are concrete and identifiable ecological mechanisms that lead to predation events. To better understand how ecological theory accords with interactions between wild predators and domestic prey, we developed a framework to describe ecological drivers of predation on livestock. We based this framework on foundational ecological theory and current research on interactions between predators and domestic prey. We used this framework to examine ecological mechanisms (e.g., density-mediated effects, behaviorally mediated effects, and optimal foraging theory) through which specific management interventions operate, and we analyzed the ecological determinants of failure and success of management interventions in 3 case studies: snow leopards (Panthera uncia), wolves (Canis lupus), and cougars (Puma concolor). The varied, context-dependent successes and failures of the management interventions in these case studies demonstrated the utility of using an ecological framework to ground research and management of carnivore–livestock conflict. Mitigation of human–wildlife conflict appears to require an understanding of how fundamental ecological theories work within domestic predator–prey systems.  相似文献   
120.
To better understand why leader–member exchange (LMX) differentiation in teams may be detrimental to individual and team performance, we propose that team members' perception of LMX differentiation (PLMXD) is more important than statistical measures of LMX differentiation. Specifically, we hypothesize a multilevel model in which relationship conflict and procedural justice (climate) mediate the relationships of individual and collective PLMXDs with individual and team performance, respectively. Using a sample of 235 individuals in 53 teams, we found that individual PLMXD was negatively related to individual performance through relationship conflict perceptions, controlling for LMX. At the team level, collective PLMXD was negatively related to team performance through procedural justice climate and relationship conflict, controlling for a statistical measure of LMXD. Theoretical implications and directions for future research are explored.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号