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   34199篇
  免费   415篇
  国内免费   515篇
安全科学   1127篇
废物处理   1636篇
环保管理   4763篇
综合类   5366篇
基础理论   8817篇
环境理论   23篇
污染及防治   8935篇
评价与监测   2314篇
社会与环境   1922篇
灾害及防治   226篇
  2023年   158篇
  2022年   332篇
  2021年   351篇
  2020年   265篇
  2019年   337篇
  2018年   531篇
  2017年   550篇
  2016年   826篇
  2015年   654篇
  2014年   967篇
  2013年   2868篇
  2012年   1196篇
  2011年   1618篇
  2010年   1324篇
  2009年   1351篇
  2008年   1638篇
  2007年   1695篇
  2006年   1448篇
  2005年   1230篇
  2004年   1130篇
  2003年   1215篇
  2002年   1090篇
  2001年   1297篇
  2000年   953篇
  1999年   605篇
  1998年   407篇
  1997年   413篇
  1996年   417篇
  1995年   481篇
  1994年   496篇
  1993年   405篇
  1992年   440篇
  1991年   392篇
  1990年   427篇
  1989年   376篇
  1988年   321篇
  1987年   307篇
  1986年   258篇
  1985年   284篇
  1984年   306篇
  1983年   301篇
  1982年   275篇
  1981年   268篇
  1980年   212篇
  1979年   212篇
  1978年   195篇
  1977年   132篇
  1975年   151篇
  1972年   135篇
  1971年   143篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
111.
112.
113.
Sharlin SA  Mor-Barak M 《Disasters》1983,7(2):142-147
This paper describes the help given by the social services department of a shipping company to bereaved families following a shipping disaster. In the absence of clear, factual and prompt information from an authoritative source, there is a tendency for bereaved individuals to deny their loss and thereby delay the process of mourning and eventual recovery. Appropriate intervention and support can help to overcome this tendency as was seen in the Madasa case.  相似文献   
114.
Much of the forest wealth on the plains and in the hilly areas of India has been foolishly destroyed, and the rich heritage of wildlife has been slaughtered mostly for only temporary gain. The wanton axing of the larger indigenous trees and the uprooting of other floristic elements in the hills and on the lower slopes of the mountains, gradually impoverishes them, and may be followed by erosion that ultimately leaves the slopes barren. These alarming threats to the chir (Pinus roxburghii) and fir (Abies pindrow) forests of Kashmir will have disastrous consequences. Once densely-forested, the mountain slopes in Kashmir have become largely naked through too-heavy tapping and cutting of the trees; with concomitant landslides, frequent floods, and loss of fertile topsoil. Unfortunately, the people living in the areas of the chir and fir trees, do not play a proper part in their protection, and the last two decades have witnessed, year by year, the rapid march of urbanization and manifold destructive activities which have taken a heavy toll on these precious species. Urgent conservation measures are essential to preserve these endangered trees in Kashmir.  相似文献   
115.
This paper describes a novel technology for the removal of solidified radioactive waste from underground storage tanks at the DOE Hanford site in southeast Washington. The process involves the use of a unique high pressure system which pulverizes the hardened saltcake with stainless steel pellets to a powder for easy vacuum removal. The steel pellets can be magnetically separated from the waste material for re-use. Specifically this study analyzes the effects of various steel abrasives, pressure of the air stream, and stand-off distance on removal rates and penetration depth on simulated saltcake samples using the high pressure technique. A full-scale test set-up and protocol were implemented to allow for comprehensive testing. To insure reproducibility of the method, tests were then run for the optimum removal parameters. A time-dependent test was also conducted to determine the relationship of removal rates to length of pressure blasts. The results of these tests revealed that stand-off distance and pressure could be positively correlated to removal volumes. Additionally, a statistical analysis confirmed that nozzle angle is independent of removal rate. This study demonstrated that the pellet ‘blaster’ technique is a safe, effective method for removal of radioactive wastes without any increase in either waste mass or volume.  相似文献   
116.
Corporations own approximately 25% of all private land in the United States and, therefore, play an essential role in protecting biodiversity and maintaining natural habitats. The Wildlife Habitat Council (WHC) is a unique joint venture between conservation organizations and corporations to utilize corporate lands for ensuring biodiversity. The following case studies demonstrate how corporations have helped ensure healthy ecosystems and provided critical leadership in regional efforts. Amoco Chemical Company's Cooper River Plant has been instrumental in developing a cooperative project that involves numerous corporations, plantation owners, private citizens, nonprofit organizations, government agencies, and community groups to develop a comprehensive, ecosystem-based management plan for part of the Cooper River in Charleston, South Carolina, USA. The second case focuses on the Morie Company, a national sand quarry operator headquartered in southern New Jersey, USA. Morie Company is working with WHC, community groups, the Pinelands Commission, and other state regulatory agencies to explore sustainable development opportunities for companies within the Pinelands regulations. The third case takes us to DuPont Company's Asturias, Spain, site. A win—win success story of improved habitat and cost savings is the result of DuPont's concern for the environment, ability to work with a variety of groups, and willingness to consider innovative restoration techniques. The fourth case discusses Consumers Power Company's Campbell Plant in West Olive, Michigan, USA. In addition to implementing projects that contribute to biodiversity, Consumers Power has developed an environmental education field station to teach others about the importance of natural habitats. The final case highlights Baltimore Gas & Electric Company's efforts to maintain habitat for endangered species at their Calvert Cliffs site in Maryland.  相似文献   
117.
118.
ABSTRACT: Bankfull depth and discharge are basic input parameters to stream planform, stream restoration, and highway crossing designs, as well as to the development of hydraulic geometry relationships and the classification of streams. Unfortunately, there are a wide variety of definitions for bankfull that provide a range of values, and the actual selection of bankfull is subjective. In this paper, the relative uncertainty in determining the bankfull depth and discharge is quantified, first by examining the variability in the estimates of bankfull and second by using fuzzy numbers to describe bankfull depth. Fuzzy numbers are used to incorporate uncertainty due to vagueness in the definition of bankfull and subjectivity in the selection of bankfull. Examples are provided that demonstrate the use of a fuzzy bankfull depth in sediment trans. port and in stream classification. Using fuzzy numbers to describe bankfull depth rather than a deterministic value allows the engineer to base designs and decisions on a range of possible values and associated degrees of belief that the bankfull depths take on each value in that range.  相似文献   
119.
Groundwater was being remediated with pump and treat technology at a facility where the groundwater was contaminated with commonly used degreaser solvents. Hydraulic conductivity of the heterogeneous residuum was beneficiated by applying pneumatic fracturing technology. The remedial system was controlled and monitored by a sophisticated remote telemetry system. A case history follows.  相似文献   
120.
The distribution and impacts of different nitrogen pollutants are inextricably linked. To understand the problem fully, the interactions between the different pollutants need to be taken into account. This is particularly important when it comes to abatement techniques, since measures to reduce emissions of one nitrogen pollutant can often lead to an increase in another. This project represents a step towards greater understanding of these issues by linking together new and existing nitrogen flux models into a larger framework. The modelling framework has been constructed and some of the nitrogen flows between fields, farms and the atmosphere have been modelled for a UK study area for typical farm management scenarios.  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