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   898篇
  免费   12篇
  国内免费   11篇
安全科学   39篇
废物处理   32篇
环保管理   205篇
综合类   121篇
基础理论   223篇
污染及防治   203篇
评价与监测   67篇
社会与环境   24篇
灾害及防治   7篇
  2023年   6篇
  2022年   9篇
  2021年   8篇
  2020年   17篇
  2019年   13篇
  2018年   14篇
  2017年   12篇
  2016年   18篇
  2015年   18篇
  2014年   29篇
  2013年   84篇
  2012年   34篇
  2011年   56篇
  2010年   29篇
  2009年   42篇
  2008年   43篇
  2007年   67篇
  2006年   35篇
  2005年   31篇
  2004年   28篇
  2003年   30篇
  2002年   32篇
  2001年   26篇
  2000年   15篇
  1999年   13篇
  1998年   11篇
  1997年   13篇
  1996年   12篇
  1995年   7篇
  1994年   14篇
  1993年   13篇
  1992年   7篇
  1991年   6篇
  1990年   10篇
  1989年   12篇
  1988年   6篇
  1987年   9篇
  1986年   5篇
  1985年   6篇
  1984年   8篇
  1983年   4篇
  1982年   4篇
  1981年   12篇
  1980年   5篇
  1979年   6篇
  1978年   4篇
  1977年   4篇
  1975年   8篇
  1974年   5篇
  1972年   3篇
排序方式: 共有921条查询结果,搜索用时 406 毫秒
611.
A model of resource evaluation incorporating reversibility of actions and substitutability for resource services is presented, along with associated decision criteria. The model extends and generalizes the Krutilla—Fisher procedure for evaluating unique resources. The more general technique is used to assess the official analysis of the Tellico Dam project in eastern Tennessee. In terms of measured values, the preservation option is shown to be superior to development only under extreme assumptions. The existence of substantial unmeasured preservation values in the Tellico case strengthens the environmentalist position, however, particularly since net benefits of development are apparently negative.  相似文献   
612.
High total soil fluoride (10 000 microg g(-1)) in the metalliferous fluorspar tailings was reflected by elevated concentrations in standing live vegetation (300-1000 microg g(-1)); plant roots (c. 6000 microg g(-1)); plant litter (c. 4000 microg g(-1)); total body concentrations of invertebrates (400-4000 microg g(-1)) and the small mammals Microtus agrestis (120-360 microg g(-1)) and Sorex araneus (140-250 microg g(-1)). Seasonal changes in the standing live vegetation and the availability of soil fluoride to plants are discussed. Seasonal changes in total body concentrations of the small mammals were related to the age structure of the populations as well as dietary levels. In the small mammals, the concentration ratios were < 0.5 at the tailings dam and > 1.1 at the control site, indicating that both species were able to regulate fluoride accumulation at the higher levels of intake. Soft tissue concentrations were, as expected, very low compared to the hard tissues but, still, were generally significantly higher at the tailings dam compared to the control site. Evidence of dental fluorosis was found in Microtus agrestis, but not Sorex araneus.  相似文献   
613.
The arsenic levels of 23 mineral waters on sale to the public in the United Kingdom were measured. The arsenic content of most waters was below 1 g L–1 but the statutory limits of 50 ug L–1 for natural mineral waters and 100 g L–1 for non-alcoholic beverages were exceeded by the French mineral water, Vichy Célestins (220 ug L–1). Regular consumption of mineral water of such elevated concentration could make a significant contribution to the intake of the more toxic inorganic species of arsenic, with possible adverse long-term effects on the health of some individuals. The general need for analytical speciation studies of dietary arsenic is emphasised.  相似文献   
614.
615.
616.
Misunderstandings and misconceptions have arisen as the Triad approach has gained wider application. The Triad initiative's ability to catalyze second‐generation cleanup practices will be hampered if inaccurate or incomplete assumptions create persistent confusion about what Triad is or how it works. This article has been prepared by the multi‐agency workgroup responsible for articulating the Triad approach and coordinating national Triad efforts. It serves to address some misunderstandings about key Triad concepts. As an aid to those wishing to learn more, a new Web site (the Triad Resource Center, http://www.triadcentral.org) and a new Triad reference document from the Interstate Technology and Regulatory Council (ITRC) are introduced as sources of explanatory information supporting the Triad approach. © 2004 Wiley Periodicals, Inc.  相似文献   
617.
Stakeholder participation is expected to improve the efficiency, equity, and sustainability of natural resource management research and development (R&D) projects by ensuring that research reflects users’ priorities, needs, capabilities, and constraints. Use of participatory methods and tools is growing rapidly; however, there is little systematic evidence about what participation actually means in practice, or about what difference it makes. Based on an inventory of 59 self‐described participatory R&D projects in the area of natural resource management, this article characterizes the typical project and analyzes how stakeholders are selected, how they participate in the research process, and what their involvement means for project costs and impacts. The results suggest that, while projects are generating a range of direct and indirect benefits for participants, more careful attention needs to be paid to achieving equitable impacts. Current practices may lag behind best practices in key areas, such as power sharing and participant selection, and may therefore be missing important contributions from women and other marginalized groups.  相似文献   
618.
ABSTRACT: Adaptive management is a heuristic approach to treating stream restoration projects as continuous, cyclic experiments, yielding results to be incorporated into future decisions. This comprehensive assessment views failures as surprises that are valuable lessons. Monitoring, evaluation of data, and communication of results are critical; the monitoring results trigger feedback mechanisms to invoke adaptation to the newly acquired information and communication of new hypotheses, treatments, or policies. The principles of adaptive management were applied to a monitoring study of three urban stream restoration sites in Maryland. Data were collected and evaluated for various restoration techniques, including vanes, cross vanes, step pools, root wads, imbricated riprap walls, and coir fiber rolls. Improvements to the existing Maryland design guidelines and policies were developed as the feedback mechanism. With the increasing application of adaptive management in stream restoration efforts, it is likely that repeated failures will be prevented and future restoration projects will be more successful in achieving their goals.  相似文献   
619.
620.
Use of off-road vehicles (ORVs) in permafrost-affected terrain of Alaska has increased sharply over the past two decades. Until the early 1960s, most ORV use was by industry or government, which employed heavy vehicles such as industrial tractors and tracked carriers. Smaller, commercial ORVs became available in the 1960s, with the variety and number in use rapidly increasing. Wheeled and tracked ORVs, many used exclusively for recreation or subsistence harvesting by individuals, are now ubiquitous in Alaska. This increased use has led to concern over the cumulative effects of such vehicles on vegetation, soils, and environmental variables including off-site values. Factors affecting impact and subsequent restoration include specific environmental setting; vegetation; presence and ice content of permafrost; microtopography; vehicle design, weight, and ground pressure; traffic frequency; season of traffic; and individual operator practices. Approaches for mitigating adverse effects of ORVs include regulation and zoning, terrain analysis and sensitivity mapping, route selection, surface protection, and operator training. We regret the untimely death of Gunars Abele on August 27, 1989; he was a valued colleague and good friend.  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