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   31423篇
  免费   354篇
  国内免费   272篇
安全科学   1075篇
废物处理   1578篇
环保管理   4099篇
综合类   4739篇
基础理论   8016篇
环境理论   8篇
污染及防治   7899篇
评价与监测   2287篇
社会与环境   2157篇
灾害及防治   191篇
  2023年   157篇
  2022年   323篇
  2021年   387篇
  2020年   230篇
  2019年   275篇
  2018年   505篇
  2017年   529篇
  2016年   807篇
  2015年   581篇
  2014年   939篇
  2013年   2625篇
  2012年   1137篇
  2011年   1472篇
  2010年   1196篇
  2009年   1218篇
  2008年   1515篇
  2007年   1415篇
  2006年   1306篇
  2005年   1156篇
  2004年   1086篇
  2003年   1026篇
  2002年   960篇
  2001年   1102篇
  2000年   774篇
  1999年   491篇
  1998年   369篇
  1997年   386篇
  1996年   402篇
  1995年   469篇
  1994年   398篇
  1993年   345篇
  1992年   377篇
  1991年   359篇
  1990年   330篇
  1989年   323篇
  1988年   299篇
  1987年   243篇
  1986年   250篇
  1985年   250篇
  1984年   269篇
  1983年   255篇
  1982年   268篇
  1981年   222篇
  1980年   165篇
  1979年   183篇
  1978年   162篇
  1977年   133篇
  1975年   138篇
  1973年   167篇
  1972年   143篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
The effect of mountain relief and industrial air pollution on biometric parameters of pine stands was studied. The empirical–statistical models of the dependence of biometric characteristics on the parameters of forest sites were developed using raster modeling and multivariate analysis. The possibility of predicting changes in the biometric parameters at any site on the basis of these models is shown.  相似文献   
62.
In recent years flows of foreign direct investment (FDI) to developing countries have rapidly been increasing. It is now an important contributor to the national economy and urban growth in scores of developing countries. Rapid urbanization in these countries is leading to many problems in the cities. Existing urban infrastructure and municipal services have been unable to cope with the increased demand arising from growing population and rapid economic growth. Consequently, the environment in these cities has deteriorated alarmingly. This paper assesses the role of FDI in urban environmental management (UEM) by analyzing the linkages between them for Hanoi City in Vietnam. The paper's analysis and findings are presented under three main themes: one, FDI, employment and income; two, FDI and environmental degradation; and three, potential of utilizing FDI for the provision of urban environmental infrastructure and services (UEI&S) in order to improve the urban environment. Both primary and secondary source data have been used. Policy implications of the research findings are drawn from the perspective of sustainable development.  相似文献   
63.
64.
We present a case of ultrasonographic prenatal diagnosis at 24 weeks of femur—fibula—ulna (FFU) complex. To our knowledge, this is the first report of an early prenatal diagnosis of FFU.  相似文献   
65.
66.
Observations of air temperature changes in a steppe marmot burrow were performed from late July to mid-October. Until early September, temperature in the burrow remained relatively constant, but then it began to decrease rapidly. This occurred after air temperature above the ground became equal to the temperature in the burrow. Supposedly, it is in this particular period that marmots begin to plug the entrance to the burrow with earth, thus reducing heat exchange between the increasingly cold aboveground air and the air in the burrow.  相似文献   
67.
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   
68.
69.
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   
70.
Studies on paleosols under an archaeological landmark of a rare type (a complex of kurgans with “whiskers”) dating from the Early Iron Age (the fourth century AD) have been performed in the steppe zone of the Transural Plateau. The size and shape of third-order soil polygons under stony ridges (“whiskers”) between the kurgans have been described in detail. The results have shown that the paleosol under the kurgans erected at the turn of the Late Sarmatian and Hun times (1600 years ago) is characterized by a higher humus content and deeper location of the carbonate horizon, compared to the recent soil. This indicates that an increase in atmospheric humidity took place in the fourth century AD.  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