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   99827篇
  免费   1241篇
  国内免费   1167篇
安全科学   3887篇
废物处理   3690篇
环保管理   15043篇
综合类   21536篇
基础理论   27726篇
环境理论   76篇
污染及防治   19174篇
评价与监测   5999篇
社会与环境   4451篇
灾害及防治   653篇
  2022年   837篇
  2021年   844篇
  2020年   673篇
  2019年   886篇
  2018年   1321篇
  2017年   1348篇
  2016年   2311篇
  2015年   1876篇
  2014年   2624篇
  2013年   9321篇
  2012年   2565篇
  2011年   3186篇
  2010年   3478篇
  2009年   3602篇
  2008年   2816篇
  2007年   2744篇
  2006年   2930篇
  2005年   2754篇
  2004年   3048篇
  2003年   2916篇
  2002年   2472篇
  2001年   3017篇
  2000年   2376篇
  1999年   1672篇
  1998年   1434篇
  1997年   1424篇
  1996年   1557篇
  1995年   1634篇
  1994年   1538篇
  1993年   1382篇
  1992年   1384篇
  1991年   1352篇
  1990年   1294篇
  1989年   1272篇
  1988年   1118篇
  1987年   1029篇
  1986年   1013篇
  1985年   1091篇
  1984年   1188篇
  1983年   1195篇
  1982年   1192篇
  1981年   1112篇
  1980年   961篇
  1979年   959篇
  1978年   840篇
  1977年   739篇
  1976年   662篇
  1974年   654篇
  1973年   675篇
  1972年   683篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
101.
20世纪70和80年代,"酸雨"成为一个主要公共政策问题.在加拿大和北欧的斯堪的纳维亚半岛的酸化水体中,生物群落及生境遭到频繁破坏,诸如土著鲑鱼和鳟鱼种群受损乃至灭绝的现象屡见不鲜.  相似文献   
102.
The effect of mountain relief and industrial air pollution on biometric parameters of pine stands was studied. The empirical–statistical models of the dependence of biometric characteristics on the parameters of forest sites were developed using raster modeling and multivariate analysis. The possibility of predicting changes in the biometric parameters at any site on the basis of these models is shown.  相似文献   
103.
We present a case of ultrasonographic prenatal diagnosis at 24 weeks of femur—fibula—ulna (FFU) complex. To our knowledge, this is the first report of an early prenatal diagnosis of FFU.  相似文献   
104.
105.
106.
107.
Benthic organisms can significantly alter the physical properties of marine sediments, but it has hitherto been difficult to assess and quantify the effects of bioturbation. In situ geophysical techniques offer new methods for measuring these effects: measurement of acoustic shear-wave velocity and electrical resistivity allows nondestructive assessment of the properties of the grain framework and pore-fluid matrix, respectively, of the seabed sediment. The influence of burrowing invertebrates on the structural properties of sandy sediments at intertidal locations on the coast of Wales (UK) was investigated during the periol 1986–1987 using these techniques. Three species (Arenicola marina, Corophium arenarium and Lanice conchilega) were selected on the basis of their contrasting styles of burrow construction. All three species produced measurable and significant, although different, changes in bed properties. They modified shear-wave propagation through the bed by changing bed rigidity: while A. marina and C. arenarium decreased rigidity by creating open burrows, L. conchilega increased rigidity by building shell-lined tubes. All produced a decrease in electrical resistivity by altering porosity and/or tortuosity, which implies an increase in permeability; these changes were attributable not only to the presence of the burrows but also to modification of the between-burrow sediment texture and bed properties.  相似文献   
108.
109.
110.
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   
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