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   160篇
  免费   5篇
  国内免费   1篇
安全科学   4篇
废物处理   9篇
环保管理   38篇
综合类   8篇
基础理论   39篇
污染及防治   35篇
评价与监测   24篇
社会与环境   6篇
灾害及防治   3篇
  2023年   1篇
  2022年   2篇
  2021年   3篇
  2020年   2篇
  2019年   1篇
  2018年   5篇
  2017年   8篇
  2016年   9篇
  2015年   5篇
  2014年   3篇
  2013年   11篇
  2012年   13篇
  2011年   15篇
  2010年   7篇
  2009年   9篇
  2008年   7篇
  2007年   7篇
  2006年   8篇
  2005年   3篇
  2004年   6篇
  2003年   4篇
  2002年   6篇
  2001年   3篇
  2000年   1篇
  1999年   2篇
  1998年   1篇
  1997年   2篇
  1996年   2篇
  1995年   1篇
  1994年   2篇
  1993年   1篇
  1991年   2篇
  1990年   1篇
  1986年   7篇
  1984年   1篇
  1983年   1篇
  1982年   2篇
  1981年   1篇
  1973年   1篇
排序方式: 共有166条查询结果,搜索用时 0 毫秒
161.
The number of MPAs has increased sharply, from just 118 in 1970 to well over 6,300 today. This growth in numbers has also been accompanied by a voluminous growth in the academic literature on the theme, with writers employing ecologic, economic and governance lenses (or a combination thereof) to both support the case for MPA creation, and to evaluate just how successfully (or not) existing MPAs match up to their promises. Research suggests effective management of such protected areas is vital if desired outcomes are to be achieved within the allotted time period. This Special Feature on MPAs therefore seeks to address two key questions derived from the management effectiveness framework of Hockings and others (2000), namely: ‘How appropriate are the management systems and processes in place?’ and ‘Were the desired Objectives achieved—and if so, why?’ Fourteen articles, drawing on different disciplinary perspectives relating to MPA experiences from across the globe, offers insights into these questions by considering, inter alia, how: are MPA sites selected?; is ‘buy-in’ to the process from the various stakeholders achieved?; are these stakeholder’s views reflected in the management systems that evolve?, and what monitoring and evaluation mechanisms are in place? Bringing these perspectives and approaches together through the medium of this Special Feature is thus intended to further our understanding of the different issues that may confront both planners and managers of Marine Protected Areas.  相似文献   
162.
As a follow-up to our first paper in this journal, this paper discusses projects involving intensive and multiple use of space recently completed or still being developed around railway stations in London (Broadgate and Canary Wharf), Paris (Seine Rive Gauche and La Défense) and Amsterdam (Zuidas and Bijlmer). The cases were compared on the basis of spatial, functional and environmental indicators, as treated in our first paper. The environmental performance of each of the cases was determined through comparison with a theoretic reference project for an equal number of users, yet with average West-European urban values for spatial, functional and environmental properties. The case studies revealed that a high floor space index is easily achievable in urban plans, implying efficient use of land and preservation of green area outside the city. For a mono-functional office area it is easier to achieve a high FSI than for a functionally diverse area with, e.g. apartments and shops. Therefore, with respect to a reference functionally equal to the cases, the predominant office character of Canary Wharf, Broadgate and La Défense results in good environmental performance. However, on the basis of a functionally diverse reference, for which monofunctional cases were enlarged with additional area for housing and amenities, the varied areas of Zuidas and Seine Rive Gauche perform best. With respect to average urban plans, the cases achieved environmental improvement of factor 1.5. This performance is restricted by the energy consumption of buildings, which has by far the most influence on the end result. The impact of stacking on the use of building materials and energy consumption of buildings is limited, and specific sustainability measures on the building scale were not involved in the calculations. The environmental benefits of intensive and multiple use of space are mainly demonstrated by the great improvement factors for the green area preserved and transport fuel consumption. The environmental costs used for these parameters were however relatively low, leading to a limited influence on the end results. Additional effective improvements to the environmental performance of dense and functionally diverse urban plans are sustainable building design and an integrated approach to urban utilities based on sustainable technologies.  相似文献   
163.
ABSTRACT: The purpose of this study was to evaluate the Better Assessment Science Integrating Point and Nonpoint Sources (BASINS) watershed management system. BASINS data were used with the NPSM model to predict discharge and sediment concentrations at the outlet of a 103 km2 Ohio watershed. It was concluded that the NPSM model should always be calibrated but only a few of the parameters provided with BASINS needed to be calibrated. For a three‐year study period, there was a 2 percent underestimation of discharge using area weighted precipitation values and a 25 percent overestimation using the single station data in BASINS. A comparison of observed and predicted monthly discharge resulted in an r2 of 0.86 with area‐weighted precipitation and an r2 of 0.74 with the single station data. Calibrating the model to substantially improve sediment predictions was unsuccessful and we concluded that a calibration period of one year was too short. For the three‐year study period, the r2 for sediment was 0.36 with a slope of 0.37 and an intercept of 18.8 mg/l. The mean observed and predicted sediment concentrations were 27.1 mg/l and 22.6 mg/l, respectively.  相似文献   
164.
In this paper, we evaluate relationships between in-stream habitat, water chemistry, spatial distribution within a predominantly agricultural Midwestern watershed and geomorphic features and fish assemblage attributes and abundances. Our specific objectives were to: (1) identify and quantify key environmental variables at reach and system wide (watershed) scales; and (2) evaluate the relative influence of those environmental factors in structuring and explaining fish assemblage attributes at reach scales to help prioritize stream monitoring efforts and better incorporate all factors that influence aquatic biology in watershed management programs. The original combined data set consisted of 31 variables measured at 32 sites, which was reduced to 9 variables through correlation and linear regression analysis: stream order, percent wooded riparian zone, drainage area, in-stream cover quality, substrate quality, gradient, cross-sectional area, width of the flood prone area, and average substrate size. Canonical correspondence analysis (CCA) and variance partitioning were used to relate environmental variables to fish species abundance and assemblage attributes. Fish assemblages and abundances were explained best by stream size, gradient, substrate size and quality, and percent wooded riparian zone. Further data are needed to investigate why water chemistry variables had insignificant relationships with IBI scores. Results suggest that more quantifiable variables and consideration of spatial location of a stream reach within a watershed system should be standard data incorporated into stream monitoring programs to identify impairments that, while biologically limiting, are not fully captured or elucidated using current bioassessment methods.  相似文献   
165.
Since the 1950s afforestation of degraded land has been the principal means of combatting erosion in a seasonally arid area of central Spain. In the 1970s tree planting of steep hillsides and gully sides was preceded by bench terracing. Experimental sites have been established to monitor runoff and soil losses under mature Pinus forest, 12-year-old Pinus forest, and Cistus matorral. The experiment is being conducted at three scales: large gully or small watershed (c. 3.5 ha), runoff erosion plot (10–21.5 m2), and rainfall simulation plot (1 m2). Monitoring began in October 1992. Discharge was recorded continuously, while sediment loss and soil moisture content were measured on a storm basis. The paper presents summary data on runoff and soil erosion for the three scales and comments on relationships between land management, site characteristics, and these losses. We stress the crucial role of vegetation and its interrelationship with soil properties such as structure and aggregate stability. Matorral was effective in combatting water and soil loss, but we question the practice of afforesting seasonally arid, steeply sided areas that have highly erodible soils.  相似文献   
166.
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