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   1950篇
  免费   57篇
  国内免费   21篇
安全科学   93篇
废物处理   78篇
环保管理   438篇
综合类   192篇
基础理论   554篇
环境理论   5篇
污染及防治   454篇
评价与监测   127篇
社会与环境   61篇
灾害及防治   26篇
  2023年   20篇
  2022年   37篇
  2021年   49篇
  2020年   27篇
  2019年   43篇
  2018年   56篇
  2017年   61篇
  2016年   83篇
  2015年   51篇
  2014年   72篇
  2013年   164篇
  2012年   94篇
  2011年   140篇
  2010年   87篇
  2009年   101篇
  2008年   113篇
  2007年   104篇
  2006年   110篇
  2005年   56篇
  2004年   52篇
  2003年   60篇
  2002年   49篇
  2001年   34篇
  2000年   48篇
  1999年   21篇
  1998年   21篇
  1997年   12篇
  1996年   25篇
  1995年   21篇
  1994年   27篇
  1993年   11篇
  1992年   15篇
  1991年   10篇
  1990年   10篇
  1989年   15篇
  1988年   12篇
  1987年   10篇
  1986年   11篇
  1985年   9篇
  1984年   7篇
  1983年   11篇
  1982年   15篇
  1981年   15篇
  1980年   4篇
  1979年   7篇
  1978年   7篇
  1977年   4篇
  1975年   5篇
  1969年   4篇
  1958年   2篇
排序方式: 共有2028条查询结果,搜索用时 15 毫秒
901.
Photosynthetically fixed energy from the sun, in the form of net primary production, ultimately supports the majority of life on earth. Given the importance of this energy source, we calculate the human appropriation of net primary production (HANPP) for the province of Nova Scotia, Canada. We find that over 25% of potentially available production is appropriated by humans through harvest (forestry and agriculture) and land cover change. The level of appropriation in Nova Scotia is close to the global average, when methodological differences between studies are taken into account, but substantially less than in Austria and India where detailed surveys have also been conducted. Furthermore, HANPP is not distributed evenly throughout the province, but is instead concentrated in the north-central counties, where appropriation reaches 50%. We discuss the implications of these results, and the novel method used to obtain them, in the context of biophysical assessment and the species-energy hypothesis.  相似文献   
902.
903.
904.
Changing Species Richness and Composition in Canadian National Parks   总被引:3,自引:0,他引:3  
Abstract: Canada's national parks and their surrounding areas differ markedly in size, climate, vegetation, and extent of human development. We tested the extent to which total species richness, native species richness, and the number of extirpations and introductions of terrestrial vertebrates were correlated with each of these factors. To do this, we used surveys of park fauna from the present and from the time of park establishment. Richness, extirpations, and introductions were all strongly related to climate. After we controlled for climate, smaller parks had higher rates of species loss than larger parks. Land-use patterns (forest cover and fragmentation, roads, etc.) within parks were strongly correlated with land use in the regions surrounding the parks, showing that parks have not been isolated from regional development. Richness and extirpations within parks were generally more strongly related to regional characteristics than to the characteristics of the parks themselves. Species richness and numbers of introduced species were higher in parks found in landscapes with greater fragmentation. Frequencies of extirpations were less clearly related to human-influenced habitat characteristics. Introductions and extinctions most often involved game species or species directly associated with human activities. There is little evidence of subtle ecological effects being responsible for species loss. Our results suggest that management should focus on direct human interventions, such as hunting, introduction of game species, and habitat fragmentation, in parks and surrounding areas.  相似文献   
905.
Over the last five years, insurance products have been expanded to assist companies better manage environmental liabilities. The most progressive of these products is a finite‐structured program whereby the convergence of insurance and financial markets expand the meaning of “alternative risk transfer.” Finite programs blend financial markets and banking concepts with risk transfer concepts to more effectively and efficiently allow the insured to manage the financial implications of its environmental liabilities. This article presents the advantages of using finite‐structured environmental insurance policies and discusses how potential insureds can protect against several types of remediation project risks, including cleanup costs, inflation uncertainty, and variability in investment returns. © 2001 John Wiley & Sons, Inc.  相似文献   
906.
907.
This paper investigates the methodological problems associated with the use of housing market data to measure the willingness to pay for clean air. With the use of a hedonic housing price model and data for the Boston metropolitan area, quantitative estimates of the willingness to pay for air quality improvements are generated. Marginal air pollution damages (as revealed in the housing market) are found to increase with the level of air pollution and with household income. The results are relatively sensitive to the specification of the hedonic housing price equation, but insensitive to the specification of the air quality demand equation.  相似文献   
908.
To better understand sublethal effects of harmful algal blooms (HABs) on fish, mummichog, Fundulus heteroclitus (L.), were exposed in the laboratory to varying, environmentally relevant densities of Pfiesteria shumwayae (Glasgow et Burkholder, CCMP 2089, dinoflagellate) and Chaetoceros concavicornis (Mangin, CCMP 169, diatom). Two experiments were conducted during the spring of 2003 and 2004 to quantitatively examine the effects of acute (2 h) P. shumwayae and C. concavicornis algal exposure on mummichog brain activity using c-Fos expression as a marker of altered neuronal activity. Brains from HAB-exposed fish were removed, sectioned, and stained using immunocytochemistry prior to quantifying neuronal c-Fos expression. Fish exposed to P. shumwayae and C. concavicornis showed increased c-Fos expression compared to unexposed control fish. A significant dose-response relationship was observed, with increased labeling in brains of fish exposed to higher cell densities for both HAB species tested (P ≤ 0.01). Increased labeling was found in the telencephalon, optic lobes, midbrain, and portions of the medulla. The greatest increases in expression were observed in the telencephalon of P. shumwayae-exposed fish, and in the telencephalon and optic lobes of C. concavicornis-exposed fish (P ≤ 0.01). These increases in c-Fos expression are consistent with other physical and chemical stress exposures observed in fish. Neuronal stress, evidenced by c-Fos expression, demonstrates a sublethal effect of exposure and changes in brain activity in fish exposed to HAB species.  相似文献   
909.
910.
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