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   3630篇
  免费   27篇
  国内免费   17篇
安全科学   83篇
废物处理   225篇
环保管理   280篇
综合类   437篇
基础理论   789篇
环境理论   3篇
污染及防治   1233篇
评价与监测   353篇
社会与环境   262篇
灾害及防治   9篇
  2023年   34篇
  2022年   98篇
  2021年   85篇
  2020年   44篇
  2019年   66篇
  2018年   116篇
  2017年   109篇
  2016年   170篇
  2015年   108篇
  2014年   178篇
  2013年   342篇
  2012年   211篇
  2011年   279篇
  2010年   170篇
  2009年   157篇
  2008年   210篇
  2007年   219篇
  2006年   160篇
  2005年   149篇
  2004年   107篇
  2003年   91篇
  2002年   92篇
  2001年   81篇
  2000年   51篇
  1999年   32篇
  1998年   20篇
  1997年   17篇
  1996年   9篇
  1995年   26篇
  1994年   21篇
  1993年   13篇
  1992年   16篇
  1991年   13篇
  1990年   14篇
  1989年   8篇
  1988年   11篇
  1987年   4篇
  1983年   4篇
  1967年   5篇
  1966年   4篇
  1965年   4篇
  1964年   11篇
  1963年   9篇
  1962年   11篇
  1960年   8篇
  1958年   13篇
  1957年   5篇
  1956年   5篇
  1943年   3篇
  1940年   3篇
排序方式: 共有3674条查询结果,搜索用时 0 毫秒
1.
Conservation conflicts are gaining importance in contemporary conservation scholarship such that conservation may have entered a conflict hype. We attempted to uncover and deconstruct the normative assumptions behind such studies by raising several questions: what are conservation conflicts, what justifies the attention they receive, do conservation-conflict studies limit wildlife conservation, is scientific knowledge stacked against wildlife in conservation conflicts, do conservation-conflict studies adopt a specific view of democracy, can laws be used to force conservation outcomes, why is flexibility needed in managing conservation conflicts, can conservation conflicts be managed by promoting tolerance, and who needs to compromise in conservation conflicts? We suggest that many of the intellectual premises in the field may defang conservation and prevent it from truly addressing the current conservation crisis as it accelerates. By framing conservation conflicts as conflicts between people about wildlife or nature, the field insidiously transfers guilt, whereby human activities are no longer blamed for causing species decline and extinctions but conservation is instead blamed for causing social conflicts. When the focus is on mitigating social conflicts without limiting in any powerful way human activities damaging to nature, conservation-conflict studies risk keeping conservation within the limits of human activities, instead of keeping human activities within the limits of nature. For conservation to successfully stop the biodiversity crisis, we suggest the alternative goal of recognizing nature's right to existence to maintenance of ecological functions and evolutionary processes. Nature being a rights bearer or legal person would imply its needs must be explicitly taken into account in conflict adjudication. If, even in conservation, nature's interests come second to human interests, it may be no surprise that conservation cannot succeed.  相似文献   
2.
Through a systems approach indicators are shown to have the nature of variables, adopting different values or states, while other associated terms allude to special meanings assigned to specific values of the indicators. Practical implications are discussed. The concept of situational indicators of sustainability is introduced, representing a non-numerical function of both “pressures” or “driving forces” and “state” variables. A cost-effective multi-tiered approach to situational indicators is proposed. The concept of situational indicators is shown to be a particular case of indicators of systems behavior. A general systems formulation of the problem of sustainability highlights the importance of indicators of systems behavior and the central role of models in their definition.  相似文献   
3.
4.
5.
The aim of this study was to determine whether there is increased leakage of neuron-specific enolase (NSE) and S-100 protein into amniotic fluid in pregnancies with neural tube defects, since both these proteins are produced by neural tissue, and to compare the value of these substances for detecting such defects with that of the more conventional techniques of alpha-fetoprotein (AFP) and acetylcholinesterase (AChE) gel electrophoresis. Amniotic samples from 25 mid-pregnancies (15–17 weeks' gestation) with neural tube defects (14 with open spina bifida and 11 with anencephaly) and from seven mid-pregnancies with abdominal wall defects were compared with a control material consisting of 80 amniotic fluid samples from 80 consecutive mid-pregnancy amniocenteses, with normal karyotypes and AFP concentrations. All of the above cases of abnormalities were primarily detected through increased AFP levels in the amniotic fluid. Amniotic fluid samples from 13 pregnancies with fetuses with autosomal chromosomal abnormalities and seven amniotic fluid samples contaminated with blood were also included in the investigation. It is concluded from the results that the conventional AFP assay combined with AChE gel electrophoresis is the best method for screening amniotic fluid for neural tube defects and defects of the abdominal wall. Neither NSE nor S-100 assay alone proved to be superior for the detection of these cases in mid-trimester amniotic fluid. The S-100 assay, however, could give additional information in cases where AChE gel electrophoresis is not decisive; for example, in samples contaminated with blood.  相似文献   
6.
引言 墨西哥城大都市区(MCMA)位于被称作"墨西哥谷(Valle deMexico)"的天然围合的盆地里,海拔2240m.它下辖联邦区和墨西哥州的34个自治市.墨西哥城是墨西哥的首都,位于联邦区(DistritoFederal,DF),四面环山,海拔高度超过5000m.墨西哥州是墨西哥人口最稠密的地区(据报道有1300万居民),人口仅次于它的是墨西哥城,大约有860万人[1].  相似文献   
7.
8.
9.
10.
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