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   3018篇
  免费   42篇
  国内免费   25篇
安全科学   163篇
废物处理   154篇
环保管理   612篇
综合类   334篇
基础理论   725篇
环境理论   5篇
污染及防治   756篇
评价与监测   212篇
社会与环境   106篇
灾害及防治   18篇
  2023年   25篇
  2022年   37篇
  2021年   26篇
  2020年   21篇
  2019年   31篇
  2018年   66篇
  2017年   67篇
  2016年   89篇
  2015年   58篇
  2014年   84篇
  2013年   280篇
  2012年   143篇
  2011年   177篇
  2010年   120篇
  2009年   122篇
  2008年   154篇
  2007年   187篇
  2006年   152篇
  2005年   105篇
  2004年   104篇
  2003年   116篇
  2002年   89篇
  2001年   67篇
  2000年   46篇
  1999年   51篇
  1998年   38篇
  1997年   43篇
  1996年   43篇
  1995年   40篇
  1994年   41篇
  1993年   34篇
  1992年   37篇
  1991年   26篇
  1990年   29篇
  1989年   19篇
  1988年   13篇
  1987年   20篇
  1986年   25篇
  1985年   17篇
  1984年   18篇
  1983年   28篇
  1982年   28篇
  1981年   25篇
  1980年   19篇
  1979年   16篇
  1977年   11篇
  1976年   9篇
  1975年   9篇
  1974年   10篇
  1971年   11篇
排序方式: 共有3085条查询结果,搜索用时 15 毫秒
951.
952.
953.
954.
The burgeoning number of accidents with dangerous chemicals makes it incumbent upon community and regional planners to systematically deal with this problem. The first step invariably involves the assessment of the likelihood and type of incident which may impact a given area so that disasters may be averted or, at least, their effects mitigated. This paper presents one such assessment scheme, the Community Chemical Hazard Vulnerability Inventory (CCHVI). This instrument, aside from considering the type and volume of substances posing a threat to a designated area, considers the physical and human resources available, as well as the general state of readiness of the area (including such things as the interface of emergency-related organizations). The use of such vulnerability assessment instruments allows local emergency planners to identify particular dangers within their communities and permits regional planners to allocate funds for planning according to relative needs.  相似文献   
955.
Modeling houses as two coupled chambers, namely, the living area and basement, predicts more accurately the total indoor radon source flux from building materials and geology than a one-chamber model in houses with disparate radon concentrations. Three regional surveys found mean radon concentration ratios between basement and living area to range from 1.4 to 4.2, implying weak interchamber coupling in most cases. The invariability of second-order system parameters under steady infiltration but different initial conditions confirms the adequacy of the two-chamber model. The presence of a characteristic radon source flux was detected within the basements of two houses, in one case across different infiltration, coupling, and initial conditions. One-chamber models fit to two-chamber tracer gas data in one house show a source flux variation of a factor of 6 across changing coupling, while the two-chamber source flux variation was only a factor of 1.5. A substantial fraction of the apparent one-chamber living area source flux in these cases is the variable convective radon flux from the basement. The technique is not sensitive enough to detect living area source fluxes if either the interchamber coupling is strong or if the basement source flux is substantially larger.  相似文献   
956.
Biological monitoring data are obtained to document changes in population abundance for resource management, to verify compliance with regulatory directives, and to assess cause and effect for research purposes. Particular statistical analyses are often not appropriate because suitable field designs are either not available or not matched a priori to the monitoring objectives. When monitoring to detect normal changes in population numbers, quantitative problems may not be as difficult as they are in detecting and assigning causation induced by a natural or man-made pollutant. Changes in biotic abundance can be caused or influenced by compensation, indirect effects, direct mortality, and interactions among environmental variables. Even though data from baseline monitoring programs should usually only be used to detect change in biotic abundance, they sometimes can be used to draw inferences about cause by correlation or to test laboratory results against a long-term historical record. Available quantitative methodologies useful in evaluating monitoring data are limited and interpretations about cause and effect are difficult.  相似文献   
957.
This paper analyses the extent to which the new Reagan mineral policy will encourage increased US production, substitution, recycling and conservation, domestic stock-piling and diversification of foreign supplies. Major inadequacies of the mineral policy are the transfer of responsibility for research and development from the government to the unprepared private sector, the lack of emphasis on short-term research and development in mineral processing technology, and the lack of coordination between minerals policy and national security and foreign policy. However, overall the policy is a positive step towards reducing the current US minerals supply vulnerability.  相似文献   
958.
959.
Time is running out on this country's planners. Generally speaking, the art of planning has retrogressed since the time of Christ. If we are to survive, this will have to be drastically changed by the year 2000. To achieve this, we need to begin to change our thinking, today. We badly need wider social planning, giving us more alternatives-more thought on where we are going. Reasonableness requires blending of planning and construction-but a sharp line of independence is essential. We must think about all the consequences of a particular act. Through intensive professional development and achievement of professional expertise, many outstanding technicians often move into vital decision making positions within their respective agencies. As planners, they see a part of the action but miss the big picture. Problem solutions become restricted to agency or individual authorities and are not always the best alternative. Thus, the planning field is overflowing with solutions to our every problem but many solutions offer spot control, and while the black spot is removed from the garment the white spot remaining from the solution offers little consolation to the wearer.  相似文献   
960.
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