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   17472篇
  免费   92篇
  国内免费   245篇
安全科学   161篇
废物处理   1145篇
环保管理   2101篇
综合类   2266篇
基础理论   5001篇
污染及防治   3684篇
评价与监测   1585篇
社会与环境   1818篇
灾害及防治   48篇
  2023年   58篇
  2022年   130篇
  2021年   104篇
  2020年   68篇
  2019年   100篇
  2018年   1578篇
  2017年   1492篇
  2016年   1378篇
  2015年   275篇
  2014年   270篇
  2013年   704篇
  2012年   725篇
  2011年   1678篇
  2010年   984篇
  2009年   923篇
  2008年   1250篇
  2007年   1591篇
  2006年   310篇
  2005年   311篇
  2004年   321篇
  2003年   340篇
  2002年   364篇
  2001年   355篇
  2000年   230篇
  1999年   118篇
  1998年   95篇
  1997年   84篇
  1996年   108篇
  1995年   126篇
  1994年   96篇
  1993年   86篇
  1992年   90篇
  1991年   92篇
  1990年   79篇
  1989年   71篇
  1988年   69篇
  1987年   75篇
  1986年   52篇
  1985年   64篇
  1984年   73篇
  1983年   67篇
  1982年   59篇
  1981年   64篇
  1980年   47篇
  1979年   47篇
  1977年   38篇
  1976年   36篇
  1974年   35篇
  1973年   44篇
  1972年   51篇
排序方式: 共有10000条查询结果,搜索用时 640 毫秒
181.
We present a case of fetal abdominal cystic hygroma that presented at 19 weeks of gestation. Ultrasonographic evaluation of the fetus revealed soft tissue enlargement of the left leg and a retroperitoneal mass in the left pelvis and abdomen. This represents the first reported case of prenatal diagnosis of abdominal cystic hygroma.  相似文献   
182.
Intrauterine fetal demise (IUFD) in one of twins at 12 weeks of gestation was accompanied by markedly elevated maternal serum alpha-fetoprotein (AFP) at 17 and 18 weeks. Amniotic fluid AFP from the healthy surviving twin's sac at 18·5 and 23 weeks was also greatly increased along with a positive acetylcholinesterase (AChE) band. Persistently elevated AFP and positive AChE so long after fetal demise–-6·5 and 11 weeks post IUFD–-has not, to our knowledge, been previously described. In similar cases, high level ultrasound and careful placental examination at birth should be utilized to search for fetal abnormalities or multiple pregnancy with IUFD.  相似文献   
183.
184.
185.
186.
Synthetic hydrophilic polymers find promising applications in pharmacology, biotechnology and chemistry. The biocompatibility, biodegradability and pharmacological activity of these polymers depend much on their hydrophilic nature. This article summarizes the recent developments in the utilization of the different classes of these hydrophilic polymers as pharmacologically active agents, for enzyme modification and as catalysts and supports for chemical reactions.  相似文献   
187.
188.
189.
Independent teams undertook environmental monitoring of particular concentrations of major construction projects forming part of Hong Kong’s U.S. $20 billion airport infrastructure programme located in dense urban areas. The team combination of environmental specialists with experienced civil engineers enabled pragmatic mitigation measures to be developed and accepted by the construction personnel with the result that potentially significant adverse impacts were averted. The authors discuss the mechanism and success of this innovative approach.  相似文献   
190.
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   
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