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   33659篇
  免费   404篇
  国内免费   315篇
安全科学   1185篇
废物处理   1589篇
环保管理   5055篇
综合类   4820篇
基础理论   8618篇
环境理论   12篇
污染及防治   8278篇
评价与监测   2396篇
社会与环境   2197篇
灾害及防治   228篇
  2023年   150篇
  2022年   279篇
  2021年   358篇
  2020年   223篇
  2019年   293篇
  2018年   488篇
  2017年   535篇
  2016年   805篇
  2015年   617篇
  2014年   934篇
  2013年   2915篇
  2012年   1164篇
  2011年   1545篇
  2010年   1256篇
  2009年   1295篇
  2008年   1611篇
  2007年   1541篇
  2006年   1388篇
  2005年   1215篇
  2004年   1180篇
  2003年   1138篇
  2002年   1070篇
  2001年   1158篇
  2000年   867篇
  1999年   568篇
  1998年   432篇
  1997年   438篇
  1996年   454篇
  1995年   526篇
  1994年   449篇
  1993年   402篇
  1992年   437篇
  1991年   391篇
  1990年   365篇
  1989年   360篇
  1988年   320篇
  1987年   274篇
  1986年   287篇
  1985年   284篇
  1984年   306篇
  1983年   302篇
  1982年   301篇
  1981年   273篇
  1980年   208篇
  1979年   203篇
  1978年   185篇
  1977年   147篇
  1975年   150篇
  1973年   177篇
  1972年   148篇
排序方式: 共有10000条查询结果,搜索用时 421 毫秒
31.
32.
33.
34.
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   
35.
36.
37.
Quick fix. Putting out firs. Do it over. Fix it again. Bottlenecks. Come back to it later. Out of stock. Back order. Not what we ordered. Is that the best you can do? It's the contractor's fault. Not within specs. Defective. Nobody's perfect. Lost in the system. Over budget. Delayed. Late penalities. Fines.  相似文献   
38.
Although most research has focussed on inorganic nutrient forms of nitrate (NO-3) and phosphorus (PO34) in runoff and receiving waters, nitrogen loss from agricultural land can also occur in organic and ammonium-nitrogen form; phosphorus losses, although often dominated by particulate transport, may occur in soluble organic and inorganic form. Furthermore, fluxes between different species may take place during transport from the land to the stream and as a result of in-stream, in-river or in-lake transformations. Knowledge of the spatial and temporal variation in all nitrogen species and phosphorus fractions in a drainage basin is therefore essential if the wider environmental significance of elevated nutrient concentrations in natural waters are to be assessed. This paper reviews recent work on N and P losses from agricultural land and presents some results from two intensive agricultural catchments: Slapton, Devon and the river Windrush catchment in the Cotswolds.  相似文献   
39.
This paper is concerned with developing a model for group decision making under multiple criteria. The multiple criteria group decision making (MCGDM)problem involves a set of feasible land use patterns that are evaluated on the basis of multiple, conflicting and noncommensurate criteria by a group of individuals. The model integrates the Analytic Hierarchy Process (AHP) and an integer mathematical programming method. The former provides a tool for structuring the decision problem and determining land suitability for different socio-economicactivities (the uses of land), the latter is used to identify the land use pattern that maximizes consensus among interest groups. The model is used to analyze environmental conflict over land resource allocation in the Cape Region of Mexico.  相似文献   
40.
Ligustrum lucidum Ait. f. tricolor (Rehd.) Rehd. in relation to atmospheric pollutants in Córdoba city, Argentina. The study area receives regional pollutants and was categorized taking into account traffic level, industrial density, type of industry, location of the sample point in relation to the street corner, treeless condition, and topographic level. Dried weight/fresh weight ratio (DW/FW) and specific leaf area (SLA) were calculated, and concentrations of chlorophylls, carotenoids, total sulfur, soluble proteins, malondialdehyde (MDA), and hydroperoxy conjugated dienes (HPCD) were determined in leaf samples. Sulfur content correlates positively with traffic density and SLA correlates negatively with some combinations of the categorical variables; MDA correlates positively with topographic level and total protein concentration correlates negatively with treeless condition. On the basis of our results, traffic, location of trees, type of industry, situation of a tree with respect to others, and topographic level are the environmental variables to bear in mind when selecting analogous sampling points in a passive monitoring program. An approximation to predict tree injury may be obtained by measuring DW/FW ratio, proteins, pigments, HPCD, and MDA as they are responsible for the major variability of data.  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