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   10867篇
  免费   189篇
  国内免费   79篇
安全科学   357篇
废物处理   553篇
环保管理   1656篇
综合类   1370篇
基础理论   2603篇
环境理论   17篇
污染及防治   3094篇
评价与监测   870篇
社会与环境   545篇
灾害及防治   70篇
  2023年   121篇
  2022年   219篇
  2021年   263篇
  2020年   145篇
  2019年   147篇
  2018年   328篇
  2017年   322篇
  2016年   473篇
  2015年   277篇
  2014年   498篇
  2013年   972篇
  2012年   611篇
  2011年   681篇
  2010年   499篇
  2009年   454篇
  2008年   609篇
  2007年   622篇
  2006年   525篇
  2005年   416篇
  2004年   351篇
  2003年   305篇
  2002年   282篇
  2001年   169篇
  2000年   162篇
  1999年   119篇
  1998年   97篇
  1997年   78篇
  1996年   79篇
  1995年   112篇
  1994年   97篇
  1993年   80篇
  1992年   70篇
  1991年   50篇
  1990年   50篇
  1989年   44篇
  1988年   36篇
  1987年   45篇
  1986年   45篇
  1985年   46篇
  1984年   44篇
  1983年   46篇
  1982年   58篇
  1981年   43篇
  1980年   34篇
  1978年   31篇
  1964年   32篇
  1959年   27篇
  1958年   37篇
  1957年   20篇
  1955年   19篇
排序方式: 共有10000条查询结果,搜索用时 23 毫秒
991.
ABSTRACT: This paper describes the integration of a comprehensive hydrological model known as the Hydrological Simulation Program Fortran (HSPF) into a problem solving environment (PSE) for watershed management. The original PSE concept was a structure providing web‐based access to a suite of models, including HSPF and other models of in‐stream hydrodynamics, biological impacts and economic effects, for the watershed‐wide assessment of alternative land use scenarios. The present paper describes only the HSPF integration into the PSE program. Example applications to the 148 square kilometer (57 square mile) Back Creek subwatershed in the upper Roanoke River system (1,479 square kilometers or 571 square miles) in southwest Virginia are used to illustrate important concepts and linkages between land development and hydrological change using hypothetical' what if'scenarios. The features of HSPF and its limitations in this context are discussed. The paper as such is a proof‐of‐concept paper and not a completion report. It is intended to describe the PSE tool building process rather than analysis of the many possible simulation outcomes. However, the dominance of raw imperviousness as a contributor to hydrograph response is apparent in all the PSE simulations described in this paper.  相似文献   
992.
ABSTRACT: Many urban and suburban communities in the Midwest are seeking to establish sustainable, morphologically and hydraulically varied, yet dynamically stable fluvial systems that are capable of supporting healthy, biologically diverse aquatic ecosystems — a process known as stream naturalization. This paper describes an integrated research program that seeks to develop a scientific and technological framework to support two stream naturalization projects near Chicago, Illinois. The research program integrates theory and methods in fluvial geomorphology, aquatic ecology, hydraulic engineering and social theory. Both the conceptual and the practical challenges of that integration are discussed. Scientific and technical support emphasize the development of predictive tools to evaluate the performance of possible naturalization designs at scales most appropriate to community based projects. Social analysis focuses on place based evaluations of how communities formulate an environmental vision and then, through decision making, translate this vision into specific stream naturalization strategies. Integration of scientific and technical with social components occurs in the context of community based decision making as the predictive tools are employed by project scientists to help local communities translate their environmental visions into concrete environmental designs. Social analysis of this decision making process reveals how the interplay between the community's vision of what they want the watershed to become, and the scientific perspective on what the watershed can become to achieve the community's environmental goals, leads to the implementation of specific stream naturalization practices.  相似文献   
993.
This paper describes several alternatives to traditional methods of army training on dedicated ranges using live, full-calibre ammunition. These are: training/sub-calibre ammunition; training over private land; live or engagement simulation; virtual reality (VR) simulation; constructive simulation; and mechanical simulation. The advantages and disadvantages of each are examined with respect to military and environmental considerations. Varied examples from the British, US and Swiss armies are used to examine the future role of these alternative approaches in meeting a fast-changing training requirement within multiplying environmental controls and resource constraints. This paper concentrates particularly on the training requirements of artillery systems because these are amongst the most demanding in resource terms. The three cited nations operate similar artillery systems and are subject to similar constraints. The US Army's move towards simulation has been triggered largely by economic and operational factors along with tightening regulatory controls. The Swiss and British forces are highly constrained by space, the British due to population density and the Swiss due to topography. While all the alternatives offer environmental and resource advantages, VR simulation provides the most positive benefits.  相似文献   
994.
995.
A method for evaluating areas for national park status   总被引:1,自引:0,他引:1  
A procedure for evaluating different areas as national parks based on a scoring system is proposed. A National Park Evaluation Form (NPEF) evaluating natural, cultural, and recreational resources in accordance with international criteria for national parks is presented. The evaluation points given to an area indicate the possibility of the area becoming a national park. In this method, subjectivity and bias have been minimized by a special application of the Delphi technique. The method outlined here could help in the efforts of selecting and establishing national parks in many countries.  相似文献   
996.
Book reviews     
Baker  Ilyas  Kassas  M.  Bandler  Hans  Lisowski  Marylin  Disinger  John F.  Duthie  David  Briggs  K. B. 《The Environmentalist》1992,12(4):291-304
Environment Systems and Decisions -  相似文献   
997.
Acid rain in Asia   总被引:3,自引:0,他引:3  
Acid rain has been an issue of great concern in North America and Europe during the past several decades. However, due to the passage of a number of recent regulations, most notably the Clean Air Act in the United States in 1990, there is an emerging perception that the problem in these Western nations is nearing solution. The situation in the developing world, particularly in Asia, is much bleaker. Given the policies of many Asian nations to achieve levels of development comparable with the industrialized world—which necessitate a significant expansion of energy consumption (most derived from indigenous coal reserves)—the potential for the formation of, and damage from, acid deposition in these developing countries is very high. This article delineates and assesses the emissions patterns, meteorology, physical geology, and biological and cultural resources present in various Asian nations. Based on this analysis and the risk factors to acidification, it is concluded that a number of areas in Asia are currently vulnerable to acid rain. These regions include Japan, North and South Korea, southern China, and the mountainous portions of Southeast Asia and southwestern India. Furthermore, with accelerated development (and its attendant increase in energy use and production of emissions of acid deposition precursors) in many nations of Asia, it is likely that other regions will also be affected by acidification in the near future. Based on the results of this overview, it is clear that acid deposition has significant potential to impact the Asian region. However, empirical evidence is urgently needed to confirm this and to provide early warning of increases in the magnitude and spread of acid deposition and its effects throughout this part of the world.  相似文献   
998.
Packaging waste has become a focus for attention by policy‐makers in a number of countries. This article offers a simple policy measure — a packaging tax or levy — which serves the required aims of policy, namely: reducing waste at source; increasing the rate of recycling; and consistency with the polluter pays principle. The tax is illustrated in the context of beverage containers in the UK and Japan. The merits of the proposal are its simplicity and flexibility. The article suggests that the relevant environmental damages are captured by waste disposal costs and litter. Other life cycle impacts, such as emissions from energy use, could be included but only if there are not more efficient ways of regulating them.  相似文献   
999.
ABSTRACT: Most water-resouree investigations in semiarid basins of the Great Basin in western North America conclude that ground-water recharge from direct precipitation on the valley floor is negligible. However, many of these basins contain large areas covered by unvegetated, active sand dunes that may act as conduits for ground-water recharge. The potential for this previously undocumented recharge was investigated in an area covered by sand dunes in Desert Valley, northwestern Nevada, using a deep percolation model. The model uses daily measurements of precipitation and temperature th determine energy and moisture balances, from which estimates of long-term mean annual recharge are made. For the study area, the model calculated a mean annual recharge rate of as much as 1.3 inches per year, or 17 percent of the long-term mean precipitation. Model simulations also indicate that recharge would be virtually zero if the study area were covered by vegetation rather than dunes.  相似文献   
1000.
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