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   32543篇
  免费   345篇
  国内免费   285篇
安全科学   1051篇
废物处理   1541篇
环保管理   4257篇
综合类   5249篇
基础理论   8334篇
环境理论   11篇
污染及防治   7998篇
评价与监测   2310篇
社会与环境   2234篇
灾害及防治   188篇
  2023年   151篇
  2022年   286篇
  2021年   353篇
  2020年   214篇
  2019年   267篇
  2018年   479篇
  2017年   494篇
  2016年   774篇
  2015年   563篇
  2014年   930篇
  2013年   2669篇
  2012年   1093篇
  2011年   1462篇
  2010年   1176篇
  2009年   1252篇
  2008年   1510篇
  2007年   1445篇
  2006年   1300篇
  2005年   1163篇
  2004年   1104篇
  2003年   1073篇
  2002年   1009篇
  2001年   1186篇
  2000年   837篇
  1999年   525篇
  1998年   386篇
  1997年   410篇
  1996年   412篇
  1995年   499篇
  1994年   414篇
  1993年   368篇
  1992年   404篇
  1991年   388篇
  1990年   359篇
  1989年   349篇
  1988年   314篇
  1987年   262篇
  1986年   264篇
  1985年   270篇
  1984年   276篇
  1983年   284篇
  1982年   281篇
  1981年   248篇
  1980年   189篇
  1979年   209篇
  1978年   180篇
  1977年   154篇
  1975年   162篇
  1973年   184篇
  1972年   165篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
711.
The spatial structure of populations has been studied in two rodent species inhabiting the subzone of meadow steppes of the steppe zone of Omsk oblast: the narrow-sculled vole (Microtus gregalis Pall.) and steppe lemming (Lagurus lagurus Pall.). Their populations are represented by combinations of territorial family groups whose structure and spatial distribution vary by season depending on population density, the phase of the population cycle, and the status of their members in the population. In the areas cohabited by M. gregalis and L. lagurus, the pattern of territory use and the rhythm of animal activity during the day depend primarily on their total density: under conditions of low density, the population groups of both species are spatially separated; at increased density, they are distributed with respect to the pattern of daily activity. Both species jointly use part of the territory but at different times of day: M. gregalis, mainly at night and in the morning; L. lagurus, in the daytime.  相似文献   
712.
713.
The abundance and trophic structure of zooplankton along the longitudinal profile of two typical rivers in the Yaroslavl sector of the Volga region are determined by anthropogenic and zoogenic factors. The distribution of zooplankton under the influence of these factors is described by the concept of patch dynamics. The abundance of zooplankton reaches the highest values in the ameliorated upper reaches of rivers and in beaver ponds.  相似文献   
714.
1 INTRODUCTIONEnergy and environmental issues in China have receivedsignificant attention in both the peer-reviewed literatureand in international energy and environmental policymaking in the last number of years. China's coal dominatedenergy consumption results in significant regional pollutionproblems, most notably acid rain that affects nearly 1/3rdof China's landmass and air pollution that plagues manyof its major cities. China now ranks as the top emitterof sulphur dioxide (SO2) pol…  相似文献   
715.
Lichens are widely used to assess the atmospheric pollution by heavy metals and radionuclides. However, few studies are available in publications on using lichens to qualitatively assess the atmospheric pollution levels. The paper presents research results applying epiphytic lichens as bio-monitors of quantitative atmospheric contamination with uranium. The observations were conducted during 2.5 years in the natural environment. Two experimental sites were used: one in the vicinity of a uranium contamination source, the other one - at a sufficient distance away to represent the background conditions. Air and lichens were sampled at both sites monthly. Epiphytic lichens Hypogimnia physodes were used as bio-indicators. Lichen samples were taken from various trees at about 1.5m from the ground. Air was sampled with filters at sampling stations. The uranium content in lichen and air samples as well as isotopic mass ratios (235)U/(238)U were measured by mass-spectrometer technique after uranium pre-extraction. Measured content of uranium were 1.45 mgkg(-1) in lichen at 2.09 E-04 microgm(-3) in air and 0.106 mgkg(-1) in lichen at 1.13 E-05 microgm(-3) in air. The relationship of the uranium content in atmosphere and that in lichens was determined, C(AIR)=exp(1.1 x C(LICHEN)-12). The possibility of separate identification of natural and man-made uranium in lichens was demonstrated in principle.  相似文献   
716.
Species richness, taxonomic diversity, and qualitative composition of the butterfly fauna (Lepidoptera, Diurna) are discussed in the light of data on the altitudinal zonality of local faunas in the southern Far East and Transbaikalia. It is shown that qualitative elevation-dependent changes in the fauna occur only in the western and northern parts of the region.  相似文献   
717.
Trends in the anthropogenic transformation of flora in the city of Astrakhan and its environs over the past 100 years are discussed. In general, the process of flora synanthropization is observed, with natural aboriginal plant communities being replaced by anthropogenically altered communities.  相似文献   
718.
719.
720.
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   
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