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   20099篇
  免费   140篇
  国内免费   268篇
安全科学   223篇
废物处理   1279篇
环保管理   2519篇
综合类   2475篇
基础理论   5883篇
环境理论   4篇
污染及防治   4018篇
评价与监测   1747篇
社会与环境   2290篇
灾害及防治   69篇
  2023年   71篇
  2022年   155篇
  2021年   135篇
  2020年   94篇
  2019年   134篇
  2018年   1708篇
  2017年   1644篇
  2016年   1499篇
  2015年   330篇
  2014年   327篇
  2013年   831篇
  2012年   824篇
  2011年   1891篇
  2010年   1179篇
  2009年   1074篇
  2008年   1480篇
  2007年   1855篇
  2006年   387篇
  2005年   420篇
  2004年   384篇
  2003年   461篇
  2002年   479篇
  2001年   375篇
  2000年   247篇
  1999年   141篇
  1998年   123篇
  1997年   97篇
  1996年   126篇
  1995年   139篇
  1994年   114篇
  1993年   100篇
  1992年   111篇
  1991年   105篇
  1990年   85篇
  1989年   81篇
  1988年   74篇
  1987年   78篇
  1986年   57篇
  1985年   67篇
  1984年   83篇
  1983年   79篇
  1982年   67篇
  1981年   72篇
  1980年   54篇
  1979年   50篇
  1978年   39篇
  1977年   39篇
  1976年   38篇
  1973年   45篇
  1972年   52篇
排序方式: 共有10000条查询结果,搜索用时 640 毫秒
41.
Environmental conditions in cooling ponds of thermal power plants are favorable for marsh frogs. Their populations inhabiting Verkhne-Tagil and Reftinskoe reservoirs differ in some traits, such as size and age composition, growth rate after metamorphosis, spawning type, fecundity, and characteristics of larval development. Differentiation in body size manifests itself at the early stages of terrestrial life and progresses at later stages. As a consequence, larger individuals may reach maturity and participate in reproduction at an earlier age.  相似文献   
42.
Changes in the survival parameters of the red fox were analyzed at different phases of the population cycle. It was found that the survival rate in all age classes, including newborns, drastically increased at the phase of population growth. The relationship between the general mortality rate and population size was determined. A hypothesis concerning the mechanism of these changes in the general mortality rate is suggested.  相似文献   
43.
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   
44.
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   
45.
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   
46.
Whereas past research has treated co-management of common pool resources as if villagers and project implementing authorities were the only relevant actors, numerous external factors beyond the control of these two partners create barriers to successful co-management. This paper draws on discussions with Forest Department officials to examine the influence of these forces on the outcomes of Joint Forest Management (JFM) in Tamil Nadu, India. An empirical inquiry into the operational aspects of JFM indicates the important roles of political parties, powerful people, and other state institutions and functionaries as well as the flow of foreign funding. Further, the strong demand by local people for socio-economic development interventions as opposed to improvement of degraded forests belittles the role of the Forest Department relative to other departments. Numerous other conditioning factors and relationships are explored. The authors call for reforms in public governance to allow better participation of all the actors involved for this participatory management approach to succeed and sustain.  相似文献   
47.
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   
48.
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   
49.
Although stewardship has been widely defined and used in environmental management and planning, there is a dearth of studies that describe how the lay public perceives this concept. A national sample of residents in 14 states who live near DOE nuclear facilities were interviewed to delineate public understanding and awareness of the stewardship program of the U.S. Department of Energy (DOE). This study discusses the findings of the survey and discusses how institutional trust influences public participation and resident’s choices of potential stewards. Almost 40% of the respondents could not define stewardship; those who did, believed that ‘responsibility,’ ‘management,’ and ‘accountability’ are key elements of stewardship. In addition, about a third of the respondents identified Federal groups and the DOE as potential stewards. Readers should send their comments on this paper to: BhaskarNath@aol.com within 3 months of publication of this issue  相似文献   
50.
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