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   959篇
  免费   32篇
  国内免费   8篇
安全科学   52篇
废物处理   43篇
环保管理   255篇
综合类   82篇
基础理论   256篇
环境理论   2篇
污染及防治   200篇
评价与监测   67篇
社会与环境   34篇
灾害及防治   8篇
  2023年   9篇
  2022年   16篇
  2021年   12篇
  2020年   6篇
  2019年   14篇
  2018年   20篇
  2017年   21篇
  2016年   28篇
  2015年   30篇
  2014年   26篇
  2013年   60篇
  2012年   58篇
  2011年   58篇
  2010年   39篇
  2009年   60篇
  2008年   68篇
  2007年   59篇
  2006年   56篇
  2005年   32篇
  2004年   42篇
  2003年   39篇
  2002年   35篇
  2001年   9篇
  2000年   15篇
  1999年   14篇
  1998年   14篇
  1997年   11篇
  1996年   14篇
  1995年   15篇
  1994年   18篇
  1993年   11篇
  1992年   9篇
  1991年   7篇
  1990年   5篇
  1989年   9篇
  1988年   5篇
  1987年   2篇
  1986年   3篇
  1985年   8篇
  1984年   4篇
  1983年   8篇
  1982年   8篇
  1981年   3篇
  1980年   4篇
  1979年   3篇
  1978年   2篇
  1977年   4篇
  1976年   2篇
  1971年   1篇
  1957年   2篇
排序方式: 共有999条查询结果,搜索用时 31 毫秒
921.
922.
923.
924.
The U.S. Department of Energy has generated liquid wastes containing radioactive and hazardous chemicals throughout the more than forty years of operation at its Hanford site in Washington State. Many of the waste components, including nitrate and carbon tetrachloride (CCl4), have been detected in the Hanford groundwater. In-situ bioremediation of CCl4 and nitrate is being considered to clean the aquifer. Preliminary estimates indicate that this technology should cost significantly less than ex-situ bioremediation and about the same as air stripping/granular activated carbon. In-situ bioremediation has the advantage of providing ultimate destruction of the contaminant and requires significantly less remediation time. Currently, a test site is under development. A computer-aided design tool is being used to design optimal remediation conditions by linking subsurface transport predictions, site characterization data, and microbial growth and contaminant destruction kinetics.  相似文献   
925.
This paper discusses common organizational problems that cause inadequate planning and implementation processes of endangered species recovery across biologically dissimilar species. If these problems occur, even proven biological conservation techniques are jeopardized. We propose a solution that requires accountability in all phases of the restoration process and is based on cooperative input among government agencies, nongovernmental conservation organizations, and the academic community. The first step is formation of a task-oriented recovery team that integrates the best expertise into the planning process. This interdisciplinary team should be composed of people whose skills directly address issues critical for recovery. Once goals and procedures are established, the responsible agency (for example, in the United States, the US Fish and Wildlife Service) could divest some or all of its obligation for implementing the plan, yet still maintain oversight by holding implementing entities contractually accountable. Regular, periodic outside review and public documentation of the recovery team, lead agency, and the accomplishments of implementing bodies would permit evaluation necessary to improve performance. Increased cooperation among agency and nongovernmental organizations provided by this model promises a more efficient use of limited resources toward the conservation of biodiversity.  相似文献   
926.
Benchmarking is a powerful management technique that can help improve an organization's environmental performance on a number of dimensions. Benchmarking is not a cookbook solution but a systematic process of searching for the organization that is the best at a given process (“best-in-class”) and continually adopting or adapting new processes to accelerate improvement. As a continual process including planning, analysis, integration, action, and maturity phases, benchmarking should be integrated into the planning stage of the management system. Once processes are strategically identified, they can be improved within the company's Total Quality Management program. Many benefits, such as teamwork and job satisfaction, accompany benchmarking, but the greatest companywide advantage is becoming more competitive. Finding a suitable partner is crucial to the success of the benchmarking process. This article shows the traditional one-on-one approach is the most effective because it saves time and money that allows organizations to learn from each other. In addition, examples of where benchmarking partners may be found, as well as several success indicators in the benchmarking process, are presented. Since the ultimate intent of benchmarking is positive change, the difference between reengineering and continuous performance improvement and the role benchmarking plays in each is also discussed.  相似文献   
927.
928.
The intent of this article is to outline, integrate, and interpret relevant scientific, economic, and social issues of rbST technology that have contributed to the acceptance dilemma for this product. The public is divided into social groups, each with its own set of criteria on which they base rbSTs acceptability. Criteria for the scientific community may best be described as physiological. However, for consumers, criteria may be more practical, or procedural, including human health, animal welfare, environmental concerns, and overproduction. Because the business of dairy production depends on demand from the consuming public, the criteria for acceptance of rbST by producers largely reflects those of the consumers. Of necessity, producers are also critical of rbST from a business and animal improvement standpoint. Although this article demonstrates that rbST has met most physiological criteria for acceptance, the consuming public has treated the acceptance issue with forceful skepticism. The question this article addresses is, why? The authors comment that with rbST and other biotechnologies applied to agricultural animal production, it will be the responsibility of government health agencies, scientists, and manufacturers of the products to provide early, adequate, and honest public education. Attention to the concerns of the public may be the only means to prevent hysteria over this and future agricultural products of biotechnology and will, therefore, allow the public to form logical and thoughtful criteria assessments with respect to acceptance or rejection of each product.  相似文献   
929.
930.
Simulating contaminant transport in unsaturated zones with sparse hydraulic property information is a difficult, yet common, problem. When contaminant transport may occur via preferential flow, simple modeling approaches can provide predictions of interest, such as the first arrival of contaminant, with minimal site characterization. The conceptual model for unsaturated zone flow at Rainier Mesa and Shoshone Mountain, Nevada National Security Site, establishes the possibility of preferential flow through lithologies between potential radionuclide sources and the saturated zone. After identifying preferential flow as a possible contaminant transport process, we apply a simple model to estimate first arrival times for conservatively transported radionuclides to reach the saturated zone. Simulated preferential flow travel times at Rainier Mesa are tens to hundreds of years for non-ponded water sources and 1 to 2 months for continuously ponded water sources; first arrival times are approximately twice as long at Shoshone Mountain. These first arrival time results should then be viewed as a worst-case scenario but not necessarily as a timescale for a groundwater-contamination hazard, because concentrations may be very low. The alternative approach demonstrated here for estimating travel times can be useful in situations where predictions are needed by managers for the fastest arrival of contaminants, yet budgetary or time constraints preclude more rigorous analysis, and when additional model estimates are needed for comparison (i.e., model abstraction).  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