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   217篇
  免费   20篇
  国内免费   36篇
安全科学   1篇
环保管理   72篇
综合类   104篇
基础理论   55篇
污染及防治   4篇
评价与监测   18篇
社会与环境   15篇
灾害及防治   4篇
  2023年   4篇
  2022年   3篇
  2021年   6篇
  2020年   8篇
  2019年   10篇
  2018年   8篇
  2017年   7篇
  2016年   11篇
  2015年   8篇
  2014年   7篇
  2013年   14篇
  2012年   11篇
  2011年   10篇
  2010年   9篇
  2009年   12篇
  2008年   12篇
  2007年   12篇
  2006年   12篇
  2005年   2篇
  2004年   17篇
  2003年   17篇
  2002年   12篇
  2001年   11篇
  2000年   6篇
  1999年   6篇
  1998年   6篇
  1997年   3篇
  1996年   4篇
  1995年   1篇
  1994年   5篇
  1993年   1篇
  1992年   2篇
  1991年   4篇
  1990年   4篇
  1989年   1篇
  1988年   3篇
  1986年   1篇
  1985年   1篇
  1972年   1篇
  1970年   1篇
排序方式: 共有273条查询结果,搜索用时 31 毫秒
71.
Offset schemes help avoid or revert habitat loss through protection of existing habitat (avoided deforestation), through the restoration of degraded areas (natural regrowth), or both. The spatial scale of an offset scheme may influence which of these 2 outcomes is favored and is an important aspect of the scheme's design. However, how spatial scale influences the trade-offs between the preservation of existing habitat and restoration of degraded areas is poorly understood. We used the largest forest offset scheme in the world, which is part of the Brazilian Forest Code, to explore how implementation at different spatial scales may affect the outcome in terms of the area of avoided deforestation and area of regrowth. We employed a numerical simulation of trade between buyers (i.e., those who need to offset past deforestation) and sellers (i.e., landowners with exceeding native vegetation) in the Brazilian Amazon to estimate potential avoided deforestation and regrowth at different spatial scales of implementation. Allowing offsets over large spatial scales led to an area of avoided deforestation 12 times greater than regrowth, whereas restricting offsets to small spatial scales led to an area of regrowth twice as large as avoided deforestation. The greatest total area (avoided deforestation and regrowth combined) was conserved when the spatial scale of the scheme was small, especially in locations that were highly deforested. To maximize conservation gains from avoided deforestation and regrowth, the design of the Brazilian forest-offset scheme should focus on restricting the spatial scale in which offsets occur. Such a strategy could help ensure conservation benefits are localized and promote the recovery of degraded areas in the most threatened forest landscapes.  相似文献   
72.
Wildlife corridors aim to promote species’ persistence by connecting habitat patches across fragmented landscapes. Their implementation is limited by patterns of land ownership and complicated by differences in the jurisdictional and regulatory authorities under which lands are managed. Terrestrial corridor conservation requires coordination across jurisdictions and sectors subject to site-specific overlapping sources of legal authority. Mapping spatial patterns of legal authority concurrent with habitat condition can illustrate opportunities to build or leverage capacity for connectivity conservation. Streamside areas provide pragmatic opportunities to leverage existing policy mechanisms for riverine and terrestrial habitat connectivity across boundaries. Conservation planners and practitioners can make use of these opportunities by harmonizing actions for multiple conservation outcomes. We formulated an integrative, data-driven method for mapping multiple sources of legal authority weighted by capacity for coordinating terrestrial habitat conservation along streams. We generated a map of capacity to coordinate streamside corridor protections across a wildlife habitat gap to demonstrate this approach. We combined values representing coordination capacity and naturalness to generate an integrated legal-ecological resistance map for connectivity modeling. We then computed least-cost corridors across the integrated map, masking the terrestrial landscape to focus on streamside areas. Streamside least-cost corridors in the integrated, local-scale model diverged (∼25 km) from national-scale least-cost corridors based on naturalness. Spatial categories comparing legal- and naturalness-based resistance values by stream reach highlighted potential locations for building or leveraging existing capacity through spatial coordination of policy mechanisms or restoration actions. Agencies or nongovernmental organizations intending to restore or maintain habitat connectivity across fragmented landscapes can use this approach to inform spatial prioritization and build coordination capacity. Article impact statement: Combined mapping of legal authority and habitat condition reveals capacity to coordinate actions along streams for clean water and wildlife.  相似文献   
73.
Valley sediments samples collected from the major and minor valleys of Al-Karak catchment area (southern Jordan) were leached with hot dilute HCl and analysed for their heavy metals content. The results of leachable metal concentrations indicated the absence of anomalous values for metal occurrences. However, appreciable contamination of the sediments with Cu, Zn, Pb, Cd and Cr was observed. Using an index of pollution the extent of contamination was better delineated. The geographical distribution of the samples showed higher Cu, Zn, Pb, Cd and Cr concentrations mainly around heavily inhabited areas indicating an anthropogenic source of contamination. Lithological influence indicated from the anomalies of Fe and Mn was found to be very low.  相似文献   
74.
以往的环境功能区划将城市或某一区域作为整个目标范围的功能区划,这种方法划分环境功能区不是过细就是过笼统,使保护目标定的过高或过低。环境功能区划模糊,无法从整体上解决城市结构性污染和布局不合理的现象,达不到“分级管理、分类保护、分区防治”的环境管理目的。针对新疆特殊绿洲环境特征,本文提出新的区划方法,重新对全疆各地环境功能进行特殊环境功能区划,以期明确各类特殊环境功能区的主要特点、主要问题、主导功能和建设要求,在今后的可持续发展过程中,为国民经济和社会发展提供科学的决策依据,将对新疆社会经济的快速、稳定、持续发展具有十分现实和深远的意义。  相似文献   
75.
Many “natural” areas are exposed to military or recreational off-road vehicles. The interactive effects of different types of vehicular disturbance on vegetation have rarely been examined, and it has been proposed that some vegetation types are less susceptible to vehicular disturbance than others. At Fort Riley, Kansas, we experimentally tested how different plant community types changed after disturbance from an M1A1 Abrams tank driven at different speeds and turning angles during different seasons. The greatest vegetation change was observed because of driving in the spring in wet soils and the interaction of turning while driving fast (vegetation change was measured with Bray-Curtis dissimilarity). We found that less vegetation change occurred in communities with high amounts of native prairie vegetation than in communities with high amounts of introduced C3 grasses, which is the first experimental evidence we are aware of that suggests plant communities dominated by introduced C3 grasses changed more because of vehicular disturbance than communities dominated by native prairie grasses. We also found that vegetation changed linearly with vehicular disturbance intensity, suggesting that at least initially there was no catastrophic shift in vegetation beyond a certain disturbance intensity threshold. Overall, the intensity of vehicular disturbance appeared to play the greatest role in vegetation change, but the plant community type also played a strong role and this should be considered in land use planning. The reasons for greater vegetation change in introduced C3 grass dominated areas deserve further study.  相似文献   
76.
ABSTRACT

This paper is about mining under communal ownership which makes this kind of mining a new mining frontier. The newness of the frontier is that it has introduced a series of institutional complexities that is uncommon to artisanal and large-scale mining. Mining companies have to negotiate deals with communities and their leaders to be able to prospect for mineral resources. We also argue that the state’s environmental legislation is poorly harmonised with the prevalent conditions in communal areas where mining is gaining greater importance. Legislation remains silent on the rights of those living on communal land. These rights remain in a state of confusion with often negative effects on the local communities who are exposed to a number of duplicating development programmes and legislative structures. The aim of this paper is to explore the dynamics communal mining in the Kunene Region in north-western Namibia.  相似文献   
77.
Abstract: As nearly all of Texas’ rural lands are privately owned, landowner associations for the management of white‐tailed deer and ground‐water have become increasingly popular. Deer are a common‐pool resource with transboundary characteristics, requiring landowner cooperation for effective management. Ground‐water reserves are economically important to landowners, but are governed by the “rule of capture” whereby property rights are not defined. One ground‐water association and four wildlife management associations (WMAs) were surveyed to characterize their member demographics, land use priorities, attitudes, and social capital. Members of the ground‐water cooperative were part of a much larger, more heterogeneous, and more recently formed group than members of WMAs. They also placed greater importance on utilitarian aspects of their properties, as opposed to land stewardship for conservation as practiced by members of WMAs. If ground‐water association members could be more locally organized with more frequent meetings, social capital and information sharing may be enhanced and lead to land stewardship practices for improved hydrologic functions and sustained ground‐water supply. This, coupled with pumping rules assigned by the local ground‐water district, could yield an effective strategy that is ecologically and hydrologicaly sound, and that allows rural provision of water supply to urban consumers.  相似文献   
78.
IntroductionOneofthemajordrawbacksofalleycroppingsystemsinsemiaridlowfertilityconditionsiscompetitionforavailablewaterandnutrients.Competitionistobeexpectedifthetreeandthecrophaveoverlappingactiverootsystemsinspaceandtime.Aknowledgeofthespatialdistr…  相似文献   
79.
The methodology of operations research is judged in relation to its utility to water resource management in an urbanized arid environment and to the study of worth of data for such management. Conditions for existence of a managerial problem are reviewed as is the multilevel structure of the decision process, including decisions on social goals for Western water use. Worth of data can only be judged in relation to a particular use to meet a social or managerial objective. The role of data uncertainty on the decision process is reviewed in the light of past water decisions and present and future problems.  相似文献   
80.
干旱区油田采油污水的处理及综合利用   总被引:1,自引:0,他引:1  
我国西部干旱地区的塔里木盆地,有许多深居欧亚大陆腹地的大型油田,都地处水资源极其匮乏的地区,在油田的开发过程中的用水量和产水量都比较大,本文就采油过程中产生的采油污水的处理和综合利用问题作了探讨。  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