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   97506篇
  免费   1233篇
  国内免费   1132篇
安全科学   3915篇
废物处理   3701篇
环保管理   14753篇
综合类   21366篇
基础理论   27310篇
环境理论   73篇
污染及防治   17841篇
评价与监测   5895篇
社会与环境   4399篇
灾害及防治   618篇
  2022年   854篇
  2021年   857篇
  2020年   660篇
  2019年   870篇
  2018年   1294篇
  2017年   1329篇
  2016年   2261篇
  2015年   1851篇
  2014年   2591篇
  2013年   9255篇
  2012年   2537篇
  2011年   3094篇
  2010年   3435篇
  2009年   3578篇
  2008年   2698篇
  2007年   2520篇
  2006年   2770篇
  2005年   2685篇
  2004年   2946篇
  2003年   2828篇
  2002年   2343篇
  2001年   2744篇
  2000年   2172篇
  1999年   1635篇
  1998年   1399篇
  1997年   1398篇
  1996年   1528篇
  1995年   1629篇
  1994年   1513篇
  1993年   1353篇
  1992年   1364篇
  1991年   1334篇
  1990年   1284篇
  1989年   1240篇
  1988年   1094篇
  1987年   1015篇
  1986年   1005篇
  1985年   1078篇
  1984年   1171篇
  1983年   1176篇
  1982年   1181篇
  1981年   1100篇
  1980年   946篇
  1979年   948篇
  1978年   833篇
  1977年   723篇
  1976年   646篇
  1974年   624篇
  1973年   662篇
  1972年   653篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
The past two decades have witnessed an increase in the exploration for, and development of, mineral resources at Arctic latitudes. Such effort has resulted in the commencement of production at a number of different localities in close proximity to the ocean. Since proximity to a source of transportation for the conveyance of concentrates to the market is a primary requirement governing the economic decisions for the mine to proceed, it is logical that ore deposits near a coastline are primary targets for development.

Closely tied to coastal mining developments is the need to dispose of tailings and waste rock in the most economical manner. Prior to the advent of heightened public awareness and environmental concern, and the enactment of pollution legislation, disposal practices were largely based upon convenience. Currently, however, proposed disposal and operating practices receive closer scrutiny, with a view to providing adequate protection for aquatic resources and habitat. This paper summarizes some of the features of three Arctic mines, wastes from which enter the marine environment, and compares the disposal practices used at each to measures of environmental change as indicated by metal concentrations in various media.  相似文献   
82.
The occurrence and impact of psychological contract violations were studied among graduate management alumni (N = 128) who were surveyed twice, once at graduation (immediately following recruitment) and then two years later. Psychological contracts, reciprocal obligations in employment developed during and after recruitment, were reported by a majority of respondents (54.8 per cent) as having been violated by their employers. The impact of violations are examined using both quantitative and qualitative data. Occurrence of violations correlated positively with turnover and negatively with trust, satisfaction and intentions to remain.  相似文献   
83.
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   
84.
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   
85.
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   
86.
87.
88.
89.
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   
90.
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