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   21203篇
  免费   235篇
  国内免费   124篇
安全科学   542篇
废物处理   903篇
环保管理   2951篇
综合类   3425篇
基础理论   5919篇
环境理论   10篇
污染及防治   5481篇
评价与监测   1324篇
社会与环境   871篇
灾害及防治   136篇
  2021年   141篇
  2019年   129篇
  2018年   237篇
  2017年   254篇
  2016年   414篇
  2015年   311篇
  2014年   469篇
  2013年   1687篇
  2012年   586篇
  2011年   835篇
  2010年   685篇
  2009年   685篇
  2008年   856篇
  2007年   891篇
  2006年   798篇
  2005年   681篇
  2004年   674篇
  2003年   649篇
  2002年   632篇
  2001年   774篇
  2000年   586篇
  1999年   332篇
  1998年   274篇
  1997年   290篇
  1996年   290篇
  1995年   340篇
  1994年   310篇
  1993年   289篇
  1992年   286篇
  1991年   288篇
  1990年   299篇
  1989年   288篇
  1988年   255篇
  1987年   250篇
  1986年   229篇
  1985年   208篇
  1984年   271篇
  1983年   221篇
  1982年   276篇
  1981年   229篇
  1980年   186篇
  1979年   209篇
  1978年   191篇
  1977年   154篇
  1976年   144篇
  1975年   148篇
  1974年   161篇
  1973年   163篇
  1972年   150篇
  1971年   148篇
排序方式: 共有10000条查询结果,搜索用时 109 毫秒
761.
Abstract: The consequences of rapid rainforest clearance on native avifauna are poorly understood. In Southeast Asia, Singapore, a newly developing country, has had 95% of its native lowland rainforest cleared. Most of the rainforest was lost in the mid- to late-nineteenth century. We compared avifauna checklists from 1923, 1949, and 1998 to determine the extent of extinctions between 1923 and 1998 in Singapore. Of 203 diurnal bird species, 65 were extirpated in Singapore in the past 75 years. Four of these species were nonforest- dependent species, whereas 61 (94%) were forest bird species dependent on the primary or old secondary forest to survive. Twenty-six forest bird species became extinct between 1923 and 1949, whereas 35 forest species disappeared after 1949. We compared the body lengths, feeding guilds, and vertical feeding zones between extinct and extant forest bird species to determine whether extinction patterns were dependent on these characteristics. Larger forest bird species went extinct between 1923 and 1949. Body sizes, however, did not affect the loss of forest bird species between 1949 and 1998. We observed high losses of insectivorous birds; the insectivore-carnivore and insectivore-granivore guilds lost> 80% of the species present in 1923. The highest losses were among birds that fed in the canopy. None of the forest bird species are currently common (>100 individuals/species) within Singapore. Our study shows that more than half the forest avifauna became locally extinct after extensive deforestation. Based on this fact, the countries within Southeast Asia should reconsider their heavy deforestation practices.  相似文献   
762.
763.
本世纪期间,技术进展已经使农作物生产率发生了革命,但农作物产率的提高已经开始放慢,而世界人口却继续增长.土地退化和水资源的压力是对非常需要的土地生产率提高的严重障碍.满足21世纪全球食品需要将要求一致的人口控制政策,推进可持续消费,和大大提高我们对土地、水及其它自然资源的使用效率.本文提供了对这些问题的前瞻性分析和解决这些问题的建议.  相似文献   
764.
Human impacts on methane emission from mangrove ecosystems in India   总被引:4,自引:0,他引:4  
This study deals with the emission of methane in relation to changing environmental conditions and human impact, in three mangrove ecosystems of south India. Time-varying fluxes of methane adopting the close chamber technique were used to estimate CH4 emission from an unpolluted site (Pichavaram mangroves) and two polluted sites viz. (1) Ennore Creek mangroves (affected by fertilizer effluents and crude oil discharges) and (2) Adyar estuary mangroves (affected by the discharges of organic and industrial wastes), covering monthly and seasonal variations. The results indicate annual average CH4 emissions of 7.4, 5.02 and 15.4 mg m−2 h−1 from the sediment–water interface of the Pichavaram, Ennore Creek and Adyar estuary respectively. Emission characteristics obtained at Pichavaram mangroves represent a natural variability with changing physico-chemical factors, whereas the emission characteristics at Ennore Creek and Adyar estuary mangroves show anthropogenic influence. Several environmental factors such as oxygen availability, organic matter, soil physical and chemical properties, in addition to human-mediated interventions have been identified as influencing emission rates in the mangrove ecosystems. Preliminary CH4 emission estimates for the mangrove ecosystems along the Indian sub- continent and the tropical and subtropical coastline of the world by linear extrapolation based on surface area range from 0.05 to 0.37 and 2.8 to 19.25 Tg CH4 year−1 respectively. Our results also highlight the impact of human activities on future emission of methane from the mangrove ecosystems. Received: 3 March 1999 / Accepted: 14 September 1999  相似文献   
765.
Russian Journal of Ecology - Abstract—The study of the effect of mycorrhiza symbiosis on the transformation of carbon and nitrogen compounds in soils is important in view of the necessity to...  相似文献   
766.
This essay identifies and examines scapegoat ecology, an emergent genre in online environmental discourse. In scapegoat ecology, a public of environmentally minded individuals focuses attention and vitriol on a single person for being particularly harmful to the environment. This essay argues that such discourse deflects attention from more complex and systemic environmental factors and implicitly exonerates the broader community, assuring it of its own environmental commitments while excusing it from further ecological action. The essay describes the form and appeal of scapegoat ecology, then provides a series of illustrative case examples before highlighting the implications of such discourse for both environmental communication and broader social/political conversations.  相似文献   
767.
768.
769.
The ecosystem services (ES) concept is being increasingly incorporated into environmental policy formulation and management approaches. The Corporate Ecosystem Services Review (ESR) is a framework used to assess the dependence and impact that a business has on ES. The success of the corporate experience of ES assessment provides an opportunity for adaption for local authority decision making. In this paper, the ESR tool was adapted to the South African setting at a local government level, and tested at two sites in the Msunduzi Municipality, KwaZulu-Natal. In testing the tool and gathering feedback from key stakeholders, it was found that there are both opportunities and challenges to this approach. Overall, however, it provides an opportunity for the systematic inclusion of ES assessment into existing regulatory frameworks for land-use planning and Integrated Environmental Management, whether in a strategic application, at a broader spatial (municipal) scale or in a specific locale within the municipality.  相似文献   
770.
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