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   2158篇
  免费   258篇
  国内免费   6篇
安全科学   37篇
废物处理   16篇
环保管理   635篇
综合类   351篇
基础理论   1122篇
环境理论   3篇
污染及防治   65篇
评价与监测   48篇
社会与环境   138篇
灾害及防治   7篇
  2025年   3篇
  2024年   60篇
  2023年   100篇
  2022年   74篇
  2021年   124篇
  2020年   124篇
  2019年   114篇
  2018年   74篇
  2017年   85篇
  2016年   89篇
  2015年   104篇
  2014年   90篇
  2013年   123篇
  2012年   94篇
  2011年   102篇
  2010年   118篇
  2009年   116篇
  2008年   108篇
  2007年   125篇
  2006年   84篇
  2005年   76篇
  2004年   69篇
  2003年   26篇
  2002年   31篇
  2001年   41篇
  2000年   32篇
  1999年   20篇
  1998年   22篇
  1997年   18篇
  1996年   20篇
  1995年   18篇
  1994年   16篇
  1993年   18篇
  1992年   12篇
  1991年   8篇
  1990年   6篇
  1989年   4篇
  1988年   4篇
  1987年   10篇
  1986年   5篇
  1985年   4篇
  1984年   3篇
  1983年   7篇
  1982年   9篇
  1981年   8篇
  1980年   7篇
  1979年   4篇
  1978年   4篇
  1971年   4篇
  1968年   1篇
排序方式: 共有2422条查询结果,搜索用时 0 毫秒
61.
高黎贡山自然保护区位于怒江水系和伊洛瓦底江水系之间。据调查,共有鱼类47种。鱼类组成特点:北部多为中亚高山区种类,属华西区;南部以南亚类群占优势,属华南区。  相似文献   
62.
输电线路建设项目水土保持方案编制的几点认识   总被引:2,自引:0,他引:2  
针对输电建设项目的特点,阐述了输电线路与一般线形建设项目水土保持方案的不同之处,提出了输电线路水土保持方案编制的程序、内容及方法.  相似文献   
63.
介绍了等离子点火技术在浙江长兴电厂3号炉上的应用.自电厂进行等离子点火装置改造并正式投运以来,取得了良好的经济效益和节能效果,环境效益也十分显著,实现了低负荷断油燃烧,节油率达90%左右,1台300 MW机组可节约燃油成本180 万元/a.  相似文献   
64.
在燃煤电厂建设运行的同时,将引起一系列的水土流失问题.以四川国电金堂电厂二期扩建工程为例,简要说明项目区水土流失预测的内容和方法,并在其基础上对可能产生的水土流失和危害进行了分析,同时介绍了建设期和运行期采取的综合防治措施,为类似工程的水土保持提供借鉴.  相似文献   
65.
ABSTRACT: Historically ephemeral washes in the Las Vegas Valley have become perennial streams in the urbanized area, and the primary source of these perennial flows appears to be the overirrigation of ornamental landscaping and turf. Overirrigation produces direct runoff to the washes via the streets and results in high ground water levels in some areas. Elevated ground water levels result in discharge to the washes because of changes in the natural balance of the hydrologic system and construction site and foundation dewatering. In recognition of the resource potential of these flows within the Las Vegas Valley, of the potential for dry weather flows to convey pollutants from the Valley to Lake Mead, and of the need to characterize dry weather flows under the stormwater discharge permit program, the quantity and quality of dry weather flow in Flamingo Wash was investigated during the period September 1990 through May 1993. This paper focuses on the resource potential of the flow (quantity and quality) as it relates to the interception and use of this water within the Valley. Economic and legal issues associated with the interception and use of this resource are not considered here.  相似文献   
66.
This study analysed 14 management plans and guidelines from a 25-year period to understand trends in conservation planning. A Rosetta Stone Analysis was used for the systematic comparison of plans and guidelines. Management plans incorporated management philosophies, management scenarios, opportunities for infrastructure, and plans for data collection by 2000. As of 2010, they incorporated ecosystem services, stakeholders’ objectives and methods for storing and analysing data. The results demonstrate the complex nature of management plans, with an important workload for site managers. Recommendations for future planning include adjustments in planning timeframes and a better identification of conservation targets from initial stages.  相似文献   
67.
The Platte River Basin consists of tributaries largely in Wyoming, Colorado and Western Nebraska, with the main stem in Central Nebraska. Critical wildlife habitat on the main stem requires additional in-stream flows. The watershed is one hosting multiple resources, a variety of users, and managed by an array of state and federal agencies. This study proposes a basis for securing in-stream flows for the Platte River. Candidate water supply mechanisms are suggested based on the way in which Casper, Wyoming secured water for its municipal needs. Canal lining is compared to a dam project, increasing reservoir storage, and purchasing water rights, with consideration also made for water pricing to reduce municipal use. Comparisons are based on economic efficiency, potential water conservation, and property rights criteria. Canal lining, coupled with demand management, is shown to conserve water best, given the set of efficiency and cost criteria for in-stream flow enhancement. The approach offers an opportunity to organize the water supply choice context in a transboundary watershed when quantitative information is limited.  相似文献   
68.
    
We propose a method for the appropriate assessment of adverse effects of roads in compliance with the European Union Habitats Directive. The method incorporates an analysis of ecological risk of edge effects by the proposed roads with the related increase in accessibility. The method was tested on 30 km of planned forest roads inside an 8,000-ha reserve included in two Natura 2000 sites. As a result, the cumulative effect of 19 road segments was judged as not significantly affecting the integrity of the sites, although they made accessible an extra 314 ha. On the basis of the accessibility calculation, 20 ha of land were set aside from forest exploitation as a mandatory mitigation measure. The method objectively determined the cumulative adverse effects, enabled comparison of plan revisions and alternatives and proved to measure direct and indirect significant effects with a realistic effort in terms of field survey and geographic information system processing.  相似文献   
69.
ABSTRACT: The present energy and environmental crises are due to increasing per capita demands as well as increasing populations. The role that traditional pricing policies have played in promoting these demands is discussed. The reduction or stabilizing of per capita demands is advocated through the use of Conservational Pricing mechanisms which charge higher average prices for high consumption. An example of the effect of Conservational Pricing in the water supply industry is given.  相似文献   
70.
    
Recent studies reveal the use of tree cavities by wild honeybee colonies in European forests. This highlights the conservation potential of forests for a highly threatened component of the native entomofauna in Europe, but currently no estimate of potential wild honeybee population sizes exists. Here, we analyzed the tree cavity densities of 106 forest areas across Europe and inferred an expected population size of wild honeybees. Both forest and management types affected the density of tree cavities. Accordingly, we estimated that more than 80,000 wild honeybee colonies could be sustained in European forests. As expected, potential conservation hotspots were identified in unmanaged forests, and, surprisingly, also in other large forest areas across Europe. Our results contribute to the EU policy strategy to halt pollinator declines and reveal the potential of forest areas for the conservation of so far neglected wild honeybee populations in Europe.  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