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   2132篇
  免费   125篇
  国内免费   755篇
安全科学   174篇
废物处理   134篇
环保管理   193篇
综合类   1229篇
基础理论   340篇
污染及防治   696篇
评价与监测   115篇
社会与环境   69篇
灾害及防治   62篇
  2024年   1篇
  2023年   36篇
  2022年   138篇
  2021年   144篇
  2020年   81篇
  2019年   62篇
  2018年   86篇
  2017年   126篇
  2016年   101篇
  2015年   141篇
  2014年   179篇
  2013年   246篇
  2012年   195篇
  2011年   186篇
  2010年   141篇
  2009年   135篇
  2008年   162篇
  2007年   119篇
  2006年   142篇
  2005年   94篇
  2004年   59篇
  2003年   45篇
  2002年   43篇
  2001年   37篇
  2000年   49篇
  1999年   52篇
  1998年   49篇
  1997年   40篇
  1996年   35篇
  1995年   23篇
  1994年   18篇
  1993年   11篇
  1992年   8篇
  1991年   7篇
  1990年   4篇
  1989年   2篇
  1988年   3篇
  1987年   1篇
  1986年   2篇
  1985年   1篇
  1984年   2篇
  1983年   2篇
  1982年   2篇
  1981年   1篇
  1972年   1篇
排序方式: 共有3012条查询结果,搜索用时 781 毫秒
691.
Sediments from two rivers in China, the Haihe and Dagu Rivers, were examined for estrogenic activity using an estrogen receptor (ER)-mediated in vitro bioassay system. ER-active compounds were isolated from sediments by Soxhlet extraction, and the crude extracts were fractionated using a florisil column into three fractions. The estrogenic activity of each extract was detected by measuring luciferase activity in the human breast cancer cell line MCF-7 transfected with a luciferase receptor gene. Significant estrogenic activity was observed in each total extract. The 17beta-estradiol equivalents (E2-EQs) ranged from 8.24 to 95.28 ng E2 g(-1) dw. As a result, the relative estrogenic potencies of three fractions in this study descended in the order of Fraction 3>Fraction 2>Fraction 1. The results of the bioassay analysis indicated the heavy pollution status of these sites with estrogenic contaminants. In this study, five selected chemicals, the natural estrogens 17beta-estradiol (E2) and estrone (E1), and the xeno-estrogens 4-octylphenol (OP), 4-nonylphenol (NP), and Bisphenol A (BPA) were also analyzed using the in vitro bioassay. The estrogenic activity of these chemicals were E2>E1>NP>OP>BPA.  相似文献   
692.
HSE培训是提高员THSE意识,确保安全生产稳定局面的有效途径。河南油田井下作业队伍专业化整合以来,通过制定切实可行的培训计划、合理划分培训层次,采用灵活的培训方式和持续严密的考核,使全员的HSE培训收到了预期的效果。本文结合工作实际,对如何提高全员HSE培训质量进行探讨。  相似文献   
693.
This study systematically evaluates residential consumer responses to a utility conservation initiative based on an econometric analysis of a sample of 510 households served by Artesian Water Company, Inc. (New Castle County of Delaware). Using a panel study approach covering the period from 1992 to 1997, this study shows that Artesian's water conservation program has had statistically significant and persistent impacts on residential water consumption.  相似文献   
694.
695.
696.
切实加强我国环境教育师资队伍建设   总被引:4,自引:0,他引:4  
新的世纪已经到来,实现中国教育的全面振兴,要求环境教育必须取得实质性进展,这也是我国经济、社会实现可持续发展的必要准备,环境教育师资队伍建设是推动环境教育深入开展的关键,能否稳定、扎实、有效地开展环境教育,取决于有没有一支高素质的从事环境教育的师资队伍,因为,环境教育师资队伍是顺利实现环境教育目的,目标的前提,是组织开展实践性环境教育活动的保障,因此,加强环境教育师资队伍建设意义重大。  相似文献   
697.
698.
黑龙江省是中国的大豆之乡,在中国大豆生产中起着举足轻重的作用。近年来,大豆加工业迅猛发展,但与此同时产生的废水处理问题也不容忽视。本文通过实地调研和现状分析,指出目前大豆加工企业废水处理共有问题,并提出相应的对策和措施,为中国大豆加工业污水处理提供基础和借鉴。  相似文献   
699.
Regional vegetation pattem dynamics has a great im- pact on ecosystem and climate change.Remote sensing data and geographical information system (GIS) analysis were widely used in the detection of vegetation pattern dynamics.In this study,the Yellow River Delta was selected as the study area.By using 1986, 1993,1996,1999 and 2005 remote sensing data as basic informa- tion resource,with the support of GIS,a wetland vegetation spa- tial information dataset was built up.Through selecting the land- scape met...  相似文献   
700.
Regional vegetation pattern dynamics has a great impact on ecosystem and climate change. Remote sensing data and geographical information system (GIS) analysis were widely used in the detection of vegetation pattern dynamics. In this study, the Yellow River Delta was selected as the study area. By using 1986, 1993, 1996, 1999 and 2005 remote sensing data as basic information resource, with the support of GIS, a wetland vegetation spatial information dataset was built up. Through selecting the landscape metrics such as class area (CA), class percent of landscape (PL), number of patch (NP), largest patch index (LPI) and mean patch size (MPS) etc., the dynamics of vcgetation pattern was analyzed. The result showed that the change of vegetation pattern is significant from 1986 to 2005. From 1986-1999, the area of the vegetation, the percent of vegetation, LPI and MPS decreased, the NP increased, the vegetation pattern tends to be fragmental. The decrease in vegetation area may well be explained by the fact of the nature environment evolution (Climate change and decrease in Yellow River runoff) and the increase in the population in the Yellow River Delta. However, from 1999 2005, the area of the vegetation, the percent of vegetation, LPI and MPS increased, while the NP decreased. This trend of restoration may be due to the implementation of water resources regulation for the Yellow River Delta since 1999.  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