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   21579篇
  免费   191篇
  国内免费   333篇
安全科学   425篇
废物处理   1042篇
环保管理   2731篇
综合类   2890篇
基础理论   6161篇
环境理论   2篇
污染及防治   5039篇
评价与监测   1596篇
社会与环境   2123篇
灾害及防治   94篇
  2023年   94篇
  2022年   217篇
  2021年   172篇
  2020年   120篇
  2019年   160篇
  2018年   759篇
  2017年   741篇
  2016年   808篇
  2015年   351篇
  2014年   468篇
  2013年   1388篇
  2012年   727篇
  2011年   1428篇
  2010年   1005篇
  2009年   1093篇
  2008年   1339篇
  2007年   1558篇
  2006年   692篇
  2005年   670篇
  2004年   606篇
  2003年   715篇
  2002年   686篇
  2001年   797篇
  2000年   521篇
  1999年   305篇
  1998年   227篇
  1997年   207篇
  1996年   232篇
  1995年   271篇
  1994年   208篇
  1993年   176篇
  1992年   197篇
  1991年   195篇
  1990年   206篇
  1989年   193篇
  1988年   152篇
  1987年   158篇
  1986年   110篇
  1985年   148篇
  1984年   157篇
  1983年   141篇
  1982年   132篇
  1981年   131篇
  1980年   107篇
  1979年   113篇
  1977年   86篇
  1975年   81篇
  1974年   80篇
  1973年   95篇
  1972年   88篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
Data on the existence of a specific system regulating the growth, size, and structure of enterobacterial populations are first summarized in terms of the chemical ecology concept formulated by S.S. Shvarts. The role of this system in transgene functioning is described using the example of the lux operon integrated into Escherichia coli. A relatively simple test for estimating such interactions is proposed.Translated from Ekologiya, No. 2, 2005, pp. 91–96.Original Russian Text Copyright © 2005 by Pshenichnov, Maslennikova, Nikitina.  相似文献   
32.
The distribution pattern of the gastropod Bradybaena fruticum has been studied in a forest-steppe landscape. Analysis of the frequencies of polymorphic biochemical and conchological characters has yielded preliminary results on the characteristics of the species population structure whose formation was determined by a set of natural and anthropogenic factors.Translated from Ekologiya, No. 1, 2005, pp. 39–47.Original Russian Text Copyright © 2005 by Snegin.  相似文献   
33.
34.
Aspects of the trophic attributes of the mudskipper,Periophthalmus barbarus occurring in the mangrove swamps of ImoRiver estuary, Nigeria, were investigated during a 12-month period(April, 1992-March, 1993). Feeding intensity increased with size;it was higher in the dry season (November-April) than in the wetseason (May-October); monthly changes in the indices of feedingintensity were significantly correlated. Major food objectscomprised detritus and benthic algae; crustaceans, insects,macrophyte matter and sand grains were minor food objects whilefish, molluscs, Chilopoda, nematodes and fungi were unconsciouslydevoured objects. Diet varied seasonally; algae and sesarmid crabswere generally more in the dry season than during the rains whereasFPOM and fish increased in the wet over dry season. The mudskipperdisplay a high degree of euryphagy and can be considered as ageneralist and an omnivore. The lower trophic status of P. barbarusqualifies it as a good aquaculture candidate. Food richness washigher in big-sized class (BSC) than small-sized class (SSC).Size-based and seasonal variations were not apparent in foodrichness. Diet breadth was higher in the BSC than the SSC; therewas dry season increase in diet breadth.  相似文献   
35.
A site contaminated by mercury serves as an example for evaluating the environmental medicine aspects of mercury emissions on individuals living in the surroundings. Based on defined, conventional scenarios, estimations of internal exposure were made for seven different age groups and with regard to such contact media as soil, air and food. Using human monitoring methods, an attempt was made to compare the epidemiological results. The site-specific and pathway-specific estimation of exposure is based on a multitude of various samples as well as on measurements of concentrations in the compartments relevant for intake. As based upon rigid guideline values, both these calculations and the epidemiological investigations reveal a slight increase in the mercury exposure.  相似文献   
36.
The effect of industrial air pollution on natural small mammal populations has been studied in the northern taiga subzone of the boreal forest zone. The results of long-term monitoring have been used to demonstrate the possibility of predicting changes in the main population and community characteristics of the animal species studied as dependent on the degree of anthropogenic impact.  相似文献   
37.
38.
Four introduced and one aboriginal species of the genus Pinus L. have been studied in the middle taiga subzone of southern Karelia. Significant interspecific differences in the dates of onset, cessation, and peak of the growth of shoots and needles have been revealed. It has been shown that their annual increment depends on the rate of growth, rather than on its duration. The dynamics of shoot and needle growth in introduced and aboriginal species, though largely similar, differ in some respects. These differences reflect species-specific responses to hydrothermal conditions in a certain growing season.  相似文献   
39.
40.
In the diurnal lepidopteran fauna of the northern taiga subzone in the western Russian Plain, the species inhabiting primary biotopic complexes typical of this subzone currently account for slightly more than 60% of the total species richness and abundance. A large part of the fauna is represented by the species of more southern origin, whose expansion to the northern taiga was caused by anthropogenic transformation of landscapes between the 12th and 20th centuries and recent climate warming.  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