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   26162篇
  免费   286篇
  国内免费   216篇
安全科学   756篇
废物处理   974篇
环保管理   3639篇
综合类   4841篇
基础理论   6731篇
环境理论   17篇
污染及防治   6439篇
评价与监测   1612篇
社会与环境   1460篇
灾害及防治   195篇
  2022年   216篇
  2021年   215篇
  2020年   171篇
  2019年   217篇
  2018年   341篇
  2017年   368篇
  2016年   522篇
  2015年   448篇
  2014年   610篇
  2013年   2102篇
  2012年   789篇
  2011年   1063篇
  2010年   862篇
  2009年   992篇
  2008年   1093篇
  2007年   1102篇
  2006年   1008篇
  2005年   856篇
  2004年   784篇
  2003年   811篇
  2002年   750篇
  2001年   959篇
  2000年   717篇
  1999年   434篇
  1998年   306篇
  1997年   324篇
  1996年   349篇
  1995年   380篇
  1994年   373篇
  1993年   351篇
  1992年   333篇
  1991年   352篇
  1990年   336篇
  1989年   310篇
  1988年   259篇
  1987年   229篇
  1986年   255篇
  1985年   239篇
  1984年   250篇
  1983年   259篇
  1982年   258篇
  1981年   251篇
  1980年   232篇
  1979年   242篇
  1978年   168篇
  1977年   183篇
  1975年   139篇
  1974年   161篇
  1973年   152篇
  1972年   159篇
排序方式: 共有10000条查询结果,搜索用时 203 毫秒
361.
362.
363.
364.
365.
366.
367.
The product service systems’ (PSS) sustainability potential is described in the framework of the new types of stakeholder relationships and/or partnerships, producing new convergence of economic interests, and a potential concomitant systemic resources optimization.In this perspective, it is argued that the design competencies should move towards those of the ‘strategic design’, thus introducing the concept of ‘strategic design for sustainability’: the design of an innovation strategy, shifting the business focus from designing (and selling) physical products only, to designing (and selling) a system of products and services which are jointly capable of fulfilling specific client demands, while re-orienting current unsustainable trends in production and consumption practices.Some examples of PSS are presented and discussed using the PSS categories ‘services providing added value to the product life cycle’, ‘services providing final results to customers’, and ‘services providing enabling platforms for customers’. The cases derive from an analysis of the ‘environmental friendly innovation’ yearly endowed prize submissions. The Politecnico di Milano University together with the Bocconi University and Legambiente (an environmental NGO) promotes the initiative in Italy.  相似文献   
368.
We describe a new method for the post-mortem examination of the fetal central nervous system. The brain is immobilized in gelatin prior to ultrasonic examination. Correlation with prenatal ultrasound is excellent and subsequent pathological examination is enhanced and facilitated.  相似文献   
369.
Amniotic fluid (AF) levels of 17-hydroxyprogesterone (17OHP) and testosterone (T) were determined at 16–17 weeks in 17 pregnancies at risk for CAH and results compared to 75 normal controls. The fetus was predicted to be unaffected in 12 cases on the findings of normal AF levels of both 17OHP and T and the latter allowed a correct prediction of fetal sex in all instances. HLA typing confirmed normality in 12 cases revealing 5 carriers, 5 homozygous normal and 2 indeterminate. Steroid levels of the 2 groups were similar. Three fetuses were predicted to be CAH affected on unambiguously high levels of 17OHP and T (in female only). HLA typing was in agreement, and the diagnosis was confirmed in 2 abortuses and a female newborn by physical and hormonal studies. In the last 2 cases AF levels of OHP and T were normal but HLA (A/B/C) genotypes were identical to the CAH affected siblings. Normal physical and hormonal findings in the 2 aborted fetuses would exclude the possibility of an in utero virilizing form of CAH. The discrepancy could be explained on the basis that the fetuses had an allelic form of 21-hydroxylase deficiency or on the basis of recombination (not fully tested). It is concluded that a fully informative prenatal diagnosis of CAH should not rely entirely on HLA typing but on hormonal studies.  相似文献   
370.
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