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   45177篇
  免费   410篇
  国内免费   321篇
安全科学   1217篇
废物处理   2462篇
环保管理   5853篇
综合类   6141篇
基础理论   12373篇
环境理论   10篇
污染及防治   10876篇
评价与监测   3474篇
社会与环境   3286篇
灾害及防治   216篇
  2023年   172篇
  2022年   344篇
  2021年   367篇
  2020年   238篇
  2019年   293篇
  2018年   1867篇
  2017年   1783篇
  2016年   1945篇
  2015年   744篇
  2014年   1015篇
  2013年   3010篇
  2012年   1633篇
  2011年   2824篇
  2010年   1955篇
  2009年   1899篇
  2008年   2461篇
  2007年   2695篇
  2006年   1517篇
  2005年   1330篇
  2004年   1275篇
  2003年   1307篇
  2002年   1250篇
  2001年   1449篇
  2000年   1003篇
  1999年   631篇
  1998年   478篇
  1997年   478篇
  1996年   493篇
  1995年   578篇
  1994年   482篇
  1993年   425篇
  1992年   458篇
  1991年   447篇
  1990年   429篇
  1989年   422篇
  1988年   369篇
  1987年   299篇
  1986年   293篇
  1985年   318篇
  1984年   348篇
  1983年   322篇
  1982年   332篇
  1981年   280篇
  1980年   215篇
  1979年   234篇
  1978年   196篇
  1977年   175篇
  1975年   178篇
  1973年   212篇
  1972年   175篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
82.
Three hundred and fifty-four women who underwent midtrimester genetic amniocentesis were matched for age, parity, indication, and smoking history, with an equivalent number of women who had declined the procedure, for the purpose of comparing the neonatal respiratory status of their offspring. There was no evidence that the infants exposed to genetic amniocentesis were compromised.  相似文献   
83.
The impact of prenatal sonographic diagnosis of oesophageal and gastrointestinal obstructions has been analysed over a 10-year period. Three groups of patients were evaluated. The first group consisted of 46 newborns with abnormal prenatal sonogratns, 41 of which were confirmed to have intestinal obstruction postnatally. The second group consisted of 17 neonates with normal prenatal sonograms who had intestinal obstruction postnatally. The third group included 56 newborns who did not undergo a prenatal sonogram but who had intestinal obstruction confirmed at surgery. Polyhydramnios without the appearance of a stomach on ultrasound was diagnostic of pure oesophageal atresia. Polyhydramnios with intestinal dilation was diagnostic of intestinal obstruction. Although surgery was performed earlier in the infants diagnosed prenatally with ultrasound, mortality was no less than in the group that did not undergo a prenatal sonogram, probably because of the high incidence of associated anomalies.  相似文献   
84.
85.
In this paper we deal with the problem of identifying environmental principles for the design and operation of supply chains. The operations that are included in supply chains are briefly described along with the approaches that are applied in order to improve their environmental performance. A background of environmental principles for achieving eco-efficiency and building of environmentally friendly organizational systems is presented and emphasis is put on the application of such principles “from cradle to grave”. Then, environmental principles applicable to particular objects of logistics networks planning are identified and commented upon. In addition, selective case studies from the literature, which show the applicability of the formulated principles and their relevance to practice, are discussed. The paper concludes with some remarks regarding the benefits for companies and societies, in general, that occur as a result of the application of the formulated principles.  相似文献   
86.
87.
88.
89.
90.
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