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   23725篇
  免费   121篇
  国内免费   180篇
安全科学   465篇
废物处理   1063篇
环保管理   2620篇
综合类   4381篇
基础理论   6281篇
环境理论   7篇
污染及防治   5279篇
评价与监测   1786篇
社会与环境   2049篇
灾害及防治   95篇
  2022年   199篇
  2021年   157篇
  2019年   136篇
  2018年   745篇
  2017年   734篇
  2016年   797篇
  2015年   327篇
  2014年   532篇
  2013年   1390篇
  2012年   768篇
  2011年   1460篇
  2010年   1014篇
  2009年   1119篇
  2008年   1323篇
  2007年   1541篇
  2006年   738篇
  2005年   730篇
  2004年   642篇
  2003年   725篇
  2002年   694篇
  2001年   823篇
  2000年   526篇
  1999年   349篇
  1998年   202篇
  1997年   218篇
  1996年   216篇
  1995年   243篇
  1994年   232篇
  1993年   185篇
  1992年   216篇
  1991年   225篇
  1990年   225篇
  1989年   190篇
  1988年   207篇
  1987年   148篇
  1986年   173篇
  1985年   165篇
  1984年   176篇
  1983年   159篇
  1982年   165篇
  1981年   142篇
  1980年   113篇
  1979年   128篇
  1978年   127篇
  1977年   109篇
  1976年   117篇
  1974年   133篇
  1972年   113篇
  1967年   112篇
  1964年   112篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
41.
42.
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   
43.
44.
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   
45.
Classification and distribution of mangrove vegetation are vital information for the proper development of a mangrove management plan. In this study, classification for the mangroves of the district of Kemaman were done using both 1 : 5000 aerial photographs and Landsat TM imageries. The coverage by aerial photographs is limited to the coastal and estuarine areas only. Thus, for areas further upstream of the aerial photo coverage, Landsat TM imageries were used. Analysis of aerial photographs and remote sensing images revealed that the mangroves of Kemaman could be classified into 14 different classes of vegetation. All the 14 classes were identified from areas covered by the aerial photographs. For areas covered by the Landsat images only 7 classes of vegetation were identified. The accuracy for aerial photograph and Landsat images are 91.2% and 87.8%, respectively. It can be concluded that although both techniques are useful in determining the mangrove vegetation classes, the large 1 : 5000 aerial photographs are more accurate and provided more detailed information comparatively.  相似文献   
46.
In the periods of summer and autumn bloom of the Stephanodiscus hantzschii Crun. in recreational water bodies, studies on the vertical distribution of chlorophyll a, its contents per unit biomass, efficiency in using photosynthetically active radiation (EPhAR), and assimilative activity of microalgae were performed. The results confirmed the existence of two ecophysiological forms of St. hantzschii and provided evidence that both forms are typically autotrophic and can efficiently use low-intensity PhAR for photosynthesis.  相似文献   
47.
48.
49.
A new methodological approach to the development of biological and technological safety standards for the impact of underground mining on the natural biota is proposed.  相似文献   
50.
New experimental data on biological productivity of plant communities in oligotrophic and mesotrophic bogs of the middle taiga subzone over the past five years are presented. The relationship between net primary production and the stock of live phytomass is estimated. The stock of necromass in oligotrophic bog ecosystems increases from west to east, while the stock of live phytomass and net primary production decrease.  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