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   42049篇
  免费   422篇
  国内免费   305篇
安全科学   1149篇
废物处理   1572篇
环保管理   5450篇
综合类   8844篇
基础理论   10975篇
环境理论   23篇
污染及防治   10476篇
评价与监测   2369篇
社会与环境   1673篇
灾害及防治   245篇
  2022年   270篇
  2019年   284篇
  2018年   528篇
  2017年   513篇
  2016年   778篇
  2015年   631篇
  2014年   885篇
  2013年   2993篇
  2012年   1121篇
  2011年   1621篇
  2010年   1390篇
  2009年   1435篇
  2008年   1657篇
  2007年   1745篇
  2006年   1548篇
  2005年   1318篇
  2004年   1333篇
  2003年   1271篇
  2002年   1230篇
  2001年   1621篇
  2000年   1124篇
  1999年   732篇
  1998年   569篇
  1997年   561篇
  1996年   565篇
  1995年   638篇
  1994年   600篇
  1993年   540篇
  1992年   563篇
  1991年   529篇
  1990年   568篇
  1989年   563篇
  1988年   474篇
  1987年   430篇
  1986年   409篇
  1985年   434篇
  1984年   439篇
  1983年   456篇
  1982年   451篇
  1981年   432篇
  1980年   369篇
  1979年   392篇
  1978年   331篇
  1977年   290篇
  1976年   299篇
  1975年   275篇
  1974年   283篇
  1973年   282篇
  1972年   296篇
  1967年   284篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
91.
92.
93.
In a 1981 survey of 436 Florida citrus growers, 27 pesticide related poisoning incidents were reported that were to have taken place within one year of the interview date. From these reports it is possible to estimate that there are 376 citrus fieldworker related poisonings per year in Florida. This number of estimated poisonings may be developed into an incidence rate of 113 fieldworker poisonings per 10,000 fieldworkers.  相似文献   
94.
ABSTRACT: This paper describes the formulation of an Index of Water Quality to evaluate the level of pollution in fresh water. A Four-Round Delphi equation, using a panel of seven nationally recognized water scientists, was performed to ascertain the pollutants to be included in the index, the relationship between the quantity of these pollutants in the water and the resulting quality of the water, and the importance of each pollution variable to each water use as well as to overall pollution. A multiplicative index was used to bring the pollutants together into one system.  相似文献   
95.
Living veligers of the Cassoidea have been observed to use a mantle appendage to form and resorb periostracum. Anatomical and histological examinations of a ranellid (Cymatium sp.) larva collected from the Red Sea in 1987 revealed the structure and location of the pallial appendage. The mantle edges of juvenile or adult species of the Cassoidea do not show a comparable specialization. It is demonstrated that cassoid larval conch characters are sufficient to prove the existence of a pallial appendage without anatomical confirmation. A mantle appendage is not known from teleplanic (long-living planktic) veligers of other gastropod superfamilies. In cases where the larval strategies of the latter are known they are totally different. Therefore it is suggested that the adaptation of cassoid larvae to pelagic life is unique among gastropods representing an autapomorphic character of the superfamily.  相似文献   
96.
97.
   Global change, i.e. the mega-process radically transforming the relationship between nature and human civilization since the end of World War II, is investigated from the point of view of systems analysis. It is argued that this unbridled process should rather be domesticated by planetary control strategies transpiring from a new science called “geocybernetics”. The formal aspects of geocybernetic theory are sketched and illustrated in a tutorial theatre world reflecting the overall environment and development problematic. Within this setting a straightforward operationalization of the sweeping “sustainable development” ideal through a set of concise paradigms can be achieved. Evidence is provided that geocybernetics is actually feasible on the basis of earth system modelling and fuzzy-control techniques.  相似文献   
98.
99.
100.
Simplicity and efficiency in design and estimation are all important in deciding on sampling strategies. A simple model is given and illustrated for four practical situations to show how a good sampling strategy should be selected.The U.S. Government right to retain a non-exclusive, royalty free licence in and to any copyright is acknowledged.  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