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   17781篇
  免费   242篇
  国内免费   591篇
安全科学   483篇
废物处理   849篇
环保管理   2131篇
综合类   2887篇
基础理论   4590篇
环境理论   2篇
污染及防治   4735篇
评价与监测   1270篇
社会与环境   1538篇
灾害及防治   129篇
  2023年   113篇
  2022年   259篇
  2021年   202篇
  2020年   149篇
  2019年   192篇
  2018年   299篇
  2017年   316篇
  2016年   451篇
  2015年   337篇
  2014年   526篇
  2013年   1459篇
  2012年   613篇
  2011年   833篇
  2010年   689篇
  2009年   753篇
  2008年   846篇
  2007年   863篇
  2006年   722篇
  2005年   643篇
  2004年   608篇
  2003年   662篇
  2002年   593篇
  2001年   808篇
  2000年   540篇
  1999年   333篇
  1998年   248篇
  1997年   228篇
  1996年   248篇
  1995年   292篇
  1994年   219篇
  1993年   182篇
  1992年   205篇
  1991年   202篇
  1990年   211篇
  1989年   193篇
  1988年   153篇
  1987年   159篇
  1986年   114篇
  1985年   149篇
  1984年   151篇
  1983年   138篇
  1982年   133篇
  1981年   134篇
  1980年   107篇
  1979年   113篇
  1977年   88篇
  1975年   81篇
  1974年   80篇
  1973年   95篇
  1972年   88篇
排序方式: 共有10000条查询结果,搜索用时 141 毫秒
311.
Hydroxyprogesterone caproate is one of the most effective and widely used drugs for the treatment of uterine bleeding and threatened miscarriage in women. Hydroxyprogesterone caproate was administered to pregnant rats in order to assess the effect of intraperitoneal exposure to supranormal levels of hydroxyprogesterone caproate on the male reproductive potential in the first generation. The cauda epididymal sperm count and motility decreased significantly in rats exposed to hydroxyprogesterone caproate during embryonic development, when compared with control rats. The levels of serum testosterone decreased with an increase in follicle stimulating hormone and luteinizing hormone in adult rats exposed to hydroxyprogesterone caproate during the embryonic stage. It was suggested that the impairment of male reproductive performance could be mediated through the inhibition of testosterone production.  相似文献   
312.
313.
314.
315.
战略环境评价方法学研究   总被引:18,自引:0,他引:18  
徐鹤  朱坦 《上海环境科学》2001,20(6):295-296
通过对国内外开展战略环境评价实施的研究,分析了战略环境评价程序中各个阶段的主要内容与方法,项目环境影响评价与战略环境评价在方法学上的异同,提出了我国在战略环境评价起步阶段方法研究应注意的方面。  相似文献   
316.
Sathaye  J.A.  Makundi  W.R.  Andrasko  K.  Boer  R.  Ravindranath  N.H.  Sudha  P.  Rao  S.  Lasco  R.  Pulhin  F.  Masera  O.  Ceron  A.  Ordonez  J.  Deying  X.  Zhang  X.  Zuomin  S. 《Mitigation and Adaptation Strategies for Global Change》2001,6(3-4):185-211
This paper summarizes studies of carbon (C) mitigation potential and costs of about 40 forestry options in seven developing countries. Each study uses the same methodological approach – Comprehensive Mitigation Assessment Process (COMAP) – to estimate the above parameters between 2000 and 2030. The approach requires the projection of baseline and mitigation land-use scenarios. Coupled with data on a per ha basis on C sequestration or avoidance, and costs and benefits, it allows the estimation of monetary benefit per Mg C, and the total costs and carbon potential. The results show that about half (3.0 Pg C) the cumulative mitigation potential of 6.2 Petagram (Pg) C between 2000 and 2030 in the seven countries (about 200× 106 Mg C yr-1) could be achieved at a negative cost and the remainder at costs ranging up to $100 Mg C-1. About 5 Pg C could be achieved, at a cost less than $20 per Mg C. Negative cost potential indicates that non-carbon revenue is sufficient to offset direct costs of these options. The achievable potential is likely to be smaller, however, due to market, institutional, and sociocultural barriers that can delay or prevent the implementation of the analyzed options.  相似文献   
317.
318.
Compounds in the atmosphere contaminate samples of groundwater. An inexpensive and simple method for collecting groundwater samples is developed to prevent contamination when the background concentration of contaminants is high. This new design of groundwater sampling device involves a glass sampling bottle with a Teflon-lined valve at each end. A cleaned and dried sampling bottle was connected to a low flow-rate peristaltic pump with Teflon tubing and was filled with water. No headspace volume was remained in the sampling bottle. The sample bottle was then packed in a PVC bag to prevent the target component from infiltrating into the water sample through the valves. In this study, groundwater was sampled at six wells using both the conventional method and the improved method. The analysis of trichlorofluoromethane( CFC-11 ) concentrations at these six wells indicates that all the groundwater samples obtained by the conventional sampling method were contaminated by CFC-11 from the atmosphere. The improved sampling method greatly eliminated the problems of contamination, preservation and quantitative analysis of natural water.  相似文献   
319.
320.
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