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   87907篇
  免费   1222篇
  国内免费   1090篇
安全科学   3715篇
废物处理   3091篇
环保管理   13743篇
综合类   20991篇
基础理论   25923篇
环境理论   71篇
污染及防治   13673篇
评价与监测   5216篇
社会与环境   3289篇
灾害及防治   507篇
  2022年   777篇
  2021年   783篇
  2020年   637篇
  2019年   854篇
  2018年   1066篇
  2017年   1095篇
  2016年   2103篇
  2015年   1815篇
  2014年   2559篇
  2013年   9211篇
  2012年   2073篇
  2011年   2229篇
  2010年   3180篇
  2009年   3322篇
  2008年   1761篇
  2007年   1588篇
  2006年   2086篇
  2005年   2077篇
  2004年   2417篇
  2003年   2279篇
  2002年   1808篇
  2001年   2104篇
  2000年   1903篇
  1999年   1458篇
  1998年   1354篇
  1997年   1340篇
  1996年   1467篇
  1995年   1564篇
  1994年   1454篇
  1993年   1322篇
  1992年   1305篇
  1991年   1270篇
  1990年   1231篇
  1989年   1191篇
  1988年   1036篇
  1987年   975篇
  1986年   990篇
  1985年   1060篇
  1984年   1150篇
  1983年   1169篇
  1982年   1170篇
  1981年   1094篇
  1980年   939篇
  1979年   920篇
  1978年   820篇
  1977年   717篇
  1976年   647篇
  1975年   609篇
  1973年   639篇
  1972年   645篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
191.
192.
Early non-invasive fetal sexing is widely available over the Internet, leading to concerns about its possible use for sex selection. The aim of this review is to summarise the results of surveys describing lay attitudes towards sex selection for non-medical reasons to help address or inform such concerns. A search of electronic databases and key journals was supplemented by an Internet search and citation-tracking. Twenty-one quantitative studies were identified. Most were conducted in the US, with five recent studies in the UK and Germany. Most studies found that, overall, people were not in favour of sex selection. However, this varied from 94 to 18%. People may hold more negative attitudes when the method of sex selection is specified, particularly if this involves termination of pregnancy (TOP). Attitudes towards the general availability of sex selection are less negative than those towards personal use. Attitudes were consistently negative in German surveys. Little is known of such attitudes outside the US, the UK and Germany, and how such attitudes may change as new sex selection technologies become available. Studies of use of early non-invasive fetal sexing for sex selection for non-medical reasons are needed to assess the extent to which concerns about usage are justified and to assist in debates on how these might be most appropriately addressed. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   
193.
The components of an environmental decision support system (EDSS) were outlined in Part 1 of this paper. Here, an example application is given using a range of data from the database in order to assess the utility of one specific model chosen from the modelbase: the one-dimensional thermal stratification model, EDD1. The model is applied to a range of lake types worldwide.  相似文献   
194.
195.
196.
197.
Critical loads offer a unique way of evaluating impacts of acid deposition by quantifying environmental sensitivity. The critical loads of acidity for UK peat soils have been based upon an arbitrary reduction in pH of 0.2 units. This chemical shift needs to be better related to adverse effects on sensitive biological receptors. It is known that effective precipitation pH equates closely to soil solution pH, and the latter is directly linkable to biotic effects of pH change. On continuation of a long-term experiment assessing impacts of simulated acid rain on peat microcosms in a realistic outdoor environment, Calluna vulgaris continued to flourish at acid deposition loads well above the existing critical load. Calluna plants were harvested and analysed, and acid deposition treatments to the microcosms continued to allow natural vegetation to regenerate. A diverse mixture of moorland plants and bryophytes established at acidity treatments well above the existing critical load, and only a very high acid load resulted in no natural regeneration. A critical effective rain pH value of 3.6 is suggested as a basis for setting critical loads. At this pH, Calluna grows well, and a healthy diverse vegetation community re-establishes when harvested. It is suggested that the peat critical load should be set at the acid load that, at any specific site, would result in a mean effective precipitation pH of 3.6.  相似文献   
198.
A new methodological approach to the development of biological and technological safety standards for the impact of underground mining on the natural biota is proposed.  相似文献   
199.
Heavy metal accumulation by plant communities has been studied in different zones of impact of gas field development. The contents of heavy metals in different blocks of plant communities has proved to depend not only on the location of phytocenosis but also on its species composition. Communities dominated by species of the family Poaceae contain smaller amounts of heavy metals than those dominated by species of the family Asteraceae, especially of the genus Artemisia. The order of precedence in the accumulation of heavy metals in different blocks of plant communities has been revealed.  相似文献   
200.
Although stewardship has been widely defined and used in environmental management and planning, there is a dearth of studies that describe how the lay public perceives this concept. A national sample of residents in 14 states who live near DOE nuclear facilities were interviewed to delineate public understanding and awareness of the stewardship program of the U.S. Department of Energy (DOE). This study discusses the findings of the survey and discusses how institutional trust influences public participation and resident’s choices of potential stewards. Almost 40% of the respondents could not define stewardship; those who did, believed that ‘responsibility,’ ‘management,’ and ‘accountability’ are key elements of stewardship. In addition, about a third of the respondents identified Federal groups and the DOE as potential stewards. Readers should send their comments on this paper to: BhaskarNath@aol.com within 3 months of publication of this issue  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