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   35599篇
  免费   405篇
  国内免费   480篇
安全科学   1115篇
废物处理   1726篇
环保管理   4645篇
综合类   5543篇
基础理论   9280篇
环境理论   12篇
污染及防治   8758篇
评价与监测   2563篇
社会与环境   2619篇
灾害及防治   223篇
  2023年   175篇
  2022年   384篇
  2021年   402篇
  2020年   250篇
  2019年   333篇
  2018年   555篇
  2017年   582篇
  2016年   900篇
  2015年   666篇
  2014年   1045篇
  2013年   2991篇
  2012年   1224篇
  2011年   1632篇
  2010年   1327篇
  2009年   1385篇
  2008年   1661篇
  2007年   1597篇
  2006年   1427篇
  2005年   1267篇
  2004年   1226篇
  2003年   1173篇
  2002年   1111篇
  2001年   1325篇
  2000年   927篇
  1999年   562篇
  1998年   421篇
  1997年   445篇
  1996年   483篇
  1995年   553篇
  1994年   460篇
  1993年   406篇
  1992年   439篇
  1991年   419篇
  1990年   385篇
  1989年   374篇
  1988年   341篇
  1987年   293篇
  1986年   284篇
  1985年   297篇
  1984年   314篇
  1983年   302篇
  1982年   312篇
  1981年   266篇
  1980年   204篇
  1979年   220篇
  1978年   188篇
  1977年   161篇
  1975年   165篇
  1973年   198篇
  1972年   183篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
72.
Long-term stationary studies on the ecology of the northern mole vole (Ellobius talpinus Pall.), performed by the mark–recapture method from 1985 to 1997, have provided original data on population dynamics and structure. The analysis shows that, to reveal cyclic fluctuations of population size in this species, the period of three years should be taken as a unit of time for estimating the duration of one phase. The 12-year population cycle in E. talpinus has four distinct phases: an increase, a peak, a decline, and a minimum. At each phase, the population is characterized by certain features of family structure, age composition, birth and death rates, and the composition of migrants.  相似文献   
73.
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   
74.
75.
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   
76.
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   
77.
78.
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   
79.
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   
80.
Heavy metal accumulation by plant communities has been studied in different zones of impact of gas field development. The contents of heavy metals in different blocks of plant communities has proved to depend not only on the location of phytocenosis but also on its species composition. Communities dominated by species of the family Poaceae contain smaller amounts of heavy metals than those dominated by species of the family Asteraceae, especially of the genus Artemisia. The order of precedence in the accumulation of heavy metals in different blocks of plant communities has been revealed.  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