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   96357篇
  免费   1243篇
  国内免费   1146篇
安全科学   3810篇
废物处理   3651篇
环保管理   14402篇
综合类   21520篇
基础理论   27130篇
环境理论   78篇
污染及防治   17350篇
评价与监测   5925篇
社会与环境   4298篇
灾害及防治   582篇
  2022年   896篇
  2021年   905篇
  2020年   690篇
  2019年   896篇
  2018年   1336篇
  2017年   1328篇
  2016年   2354篇
  2015年   1890篇
  2014年   2698篇
  2013年   9436篇
  2012年   2497篇
  2011年   2874篇
  2010年   3442篇
  2009年   3542篇
  2008年   2458篇
  2007年   2380篇
  2006年   2661篇
  2005年   2543篇
  2004年   2813篇
  2003年   2706篇
  2002年   2222篇
  2001年   2638篇
  2000年   2185篇
  1999年   1603篇
  1998年   1399篇
  1997年   1379篇
  1996年   1513篇
  1995年   1607篇
  1994年   1493篇
  1993年   1350篇
  1992年   1351篇
  1991年   1316篇
  1990年   1266篇
  1989年   1231篇
  1988年   1072篇
  1987年   996篇
  1986年   999篇
  1985年   1065篇
  1984年   1168篇
  1983年   1173篇
  1982年   1183篇
  1981年   1096篇
  1980年   951篇
  1979年   932篇
  1978年   827篇
  1977年   731篇
  1976年   645篇
  1974年   623篇
  1973年   644篇
  1972年   644篇
排序方式: 共有10000条查询结果,搜索用时 359 毫秒
221.
222.
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   
223.
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   
224.
225.
226.
227.
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   
228.
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   
229.
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   
230.
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