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   25657篇
  免费   231篇
  国内免费   243篇
安全科学   666篇
废物处理   892篇
环保管理   3321篇
综合类   5989篇
基础理论   6100篇
环境理论   9篇
污染及防治   6397篇
评价与监测   1568篇
社会与环境   1058篇
灾害及防治   131篇
  2022年   178篇
  2018年   308篇
  2017年   313篇
  2016年   458篇
  2015年   369篇
  2014年   576篇
  2013年   1882篇
  2012年   709篇
  2011年   954篇
  2010年   741篇
  2009年   851篇
  2008年   949篇
  2007年   1005篇
  2006年   903篇
  2005年   766篇
  2004年   748篇
  2003年   779篇
  2002年   692篇
  2001年   961篇
  2000年   640篇
  1999年   443篇
  1998年   280篇
  1997年   298篇
  1996年   329篇
  1995年   344篇
  1994年   356篇
  1993年   290篇
  1992年   326篇
  1991年   335篇
  1990年   349篇
  1989年   319篇
  1988年   299篇
  1987年   248篇
  1986年   251篇
  1985年   270篇
  1984年   247篇
  1983年   260篇
  1982年   263篇
  1981年   266篇
  1980年   222篇
  1979年   223篇
  1978年   226篇
  1977年   195篇
  1976年   213篇
  1975年   178篇
  1974年   227篇
  1973年   195篇
  1972年   198篇
  1971年   173篇
  1967年   201篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
11.
The past two decades have witnessed an increase in the exploration for, and development of, mineral resources at Arctic latitudes. Such effort has resulted in the commencement of production at a number of different localities in close proximity to the ocean. Since proximity to a source of transportation for the conveyance of concentrates to the market is a primary requirement governing the economic decisions for the mine to proceed, it is logical that ore deposits near a coastline are primary targets for development.

Closely tied to coastal mining developments is the need to dispose of tailings and waste rock in the most economical manner. Prior to the advent of heightened public awareness and environmental concern, and the enactment of pollution legislation, disposal practices were largely based upon convenience. Currently, however, proposed disposal and operating practices receive closer scrutiny, with a view to providing adequate protection for aquatic resources and habitat. This paper summarizes some of the features of three Arctic mines, wastes from which enter the marine environment, and compares the disposal practices used at each to measures of environmental change as indicated by metal concentrations in various media.  相似文献   
12.
13.
14.
15.
16.
The Trial     
  相似文献   
17.
Geochemical characteristics of surficial sediments in the Panangad region of Cochin estuary, the largest brackish-water humid ecosystem in the south-west coast of India, were analysed. Temporal variations in nutrient stoichiometry, seasonal characteristics of redox elements Fe and S, and the phosphorus geochemistry were employed for the purpose. The stoichiometric analysis pointed towards autochthonous origin of organic matter, possibility of nitrogen limitation, and allochthonous modification of redox conditions. Seasonal variations were not statistically significant for all the geochemical parameters, whereas significant spatial variations were observed with lower values at sandy stations, suggesting that the texture of the sediments is the main factor influencing the sediment geochemistry. Significant inter-relations between the geochemical parameters also suggest a common control mechanism. Based on these geochemical characteristics, the study region can be effectively categorized into two distinct zones, viz. (1) erosion and transportation and (2) deposition zones.  相似文献   
18.
This paper examines the relationship between survivor reactions to a downsizing and retention subsequent to a downsizing. We hypothesize that survivors who experience the downsizing as distributively, procedurally, and interactionally just and who see top management as trustworthy will feel more attached to the organization because each reduces the threat inherent in downsizing. In addition, we hypothesize that survivors who feel empowered will also feel more attached to the organization because they feel better able to cope with the downsizing. We further hypothesize that those survivors who feel more attached to the organization following the downsizing will be more likely to remain with the organization in the coming year. The theoretical model is tested on a sample of aerospace employees who survived an organizational downsizing. The trustworthiness of management, distributive justice, procedural justice, and three dimensions of empowerment are found to facilitate more organizational attachment. Higher levels of attachment are found, in turn, to facilitate less voluntary turnover in the year following the downsizing. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   
19.
20.
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