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   115篇
  免费   1篇
  国内免费   1篇
安全科学   16篇
废物处理   2篇
环保管理   33篇
综合类   16篇
基础理论   18篇
污染及防治   18篇
评价与监测   10篇
社会与环境   3篇
灾害及防治   1篇
  2023年   1篇
  2021年   1篇
  2020年   1篇
  2019年   2篇
  2018年   1篇
  2017年   3篇
  2016年   4篇
  2015年   2篇
  2014年   4篇
  2013年   14篇
  2011年   4篇
  2010年   3篇
  2009年   7篇
  2008年   7篇
  2007年   7篇
  2006年   2篇
  2005年   1篇
  2004年   9篇
  2003年   6篇
  2002年   2篇
  2001年   4篇
  2000年   3篇
  1999年   4篇
  1998年   2篇
  1997年   2篇
  1996年   1篇
  1995年   2篇
  1994年   2篇
  1993年   3篇
  1992年   1篇
  1990年   4篇
  1989年   1篇
  1985年   2篇
  1983年   2篇
  1982年   1篇
  1981年   1篇
  1980年   1篇
排序方式: 共有117条查询结果,搜索用时 843 毫秒
1.
ABSTRACT: Increasing demands on western water are causing a mounting need for the conjunctive management of surface water and ground water resources. Under western water law, the senior water rights holder has priority over the junior water rights holder in times of water shortage. Water managers have been reluctant to conjunctively manage surface water and ground water resources because of the difficulty of quantification of the impacts to surface water resources from ground water stresses. Impacts from ground water use can take years to propagate through an aquifer system. Prediction of the degree of impact to surface water resources over time and the spatial distribution of impacts is very difficult. Response functions mathematically describe the relationship between a unit ground water stress applied at a specific location and stream depletion or aquifer water level change elsewhere in the system. Response functions can be used to help quantify the spatial and temporal impacts to surface water resources caused by ground water pumping. This paper describes the theory of response functions and presents an application of transient response functions in the Snake River Plain, Idaho. Transient response functions can be used to facilitate the conjunctive management of surface and ground water not only in the eastern Snake River Plain basin, but also in similar basins throughout the western United States.  相似文献   
2.
Use of impervious cover is transitioning from an indicator of surface water condition to one that also guides and informs watershed planning and management, including Clean Water Act (33 U.S.C. §1251 et seq.) reporting. Whether it is for understanding surface water condition or planning and management, impervious cover is most commonly expressed as summary measurement (e.g., percentage watershed in impervious cover). We use the National Land Cover Database to estimate impervious cover in the vicinity of surface waters for three time periods (2001, 2006, 2011). We also compare impervious cover in the vicinity of surface waters to watershed summary estimates of impervious cover for classifying the spatial pattern of impervious cover. Between 2001 and 2011, surface water shorelines (streams and water bodies) in the vicinity of impervious cover increased nearly 10,000 km. Across all time periods, approximately 27% of the watersheds in the continental United States had proximally distributed impervious cover, i.e., the percentage of impervious cover in the vicinity of surface waters was higher than its watershed summary expression. We discuss how impervious cover spatial pattern can be used to inform watershed planning and management, including reporting under the Clean Water Act.  相似文献   
3.
Abstract

Large-scale studies like the Southeast Michigan Ozone Study (SEMOS) have focused attention on quantifying and spedating inventories for volatile organic compounds (VOCs). One approach for evaluating the accuracy of a VOC emission inventory is the development of a chemical mass balance (CMB) receptor model for ambient non-methane organic compound (NMOC) measurements. CMB evaluations of ambient hydrocarbon data provide a sample-specific allocation of emissions to individual source categories. This study summarizes the results of an application of the CMB model to the NMOC data from the SEMOS study. Comparison of CMB results with emission inventory values for the Detroit area show that vehicle emissions are well represented by the inventory, as are architectural coatings and coke ovens. Estimated emissions from petroleum refineries and graphic arts industries are much lower in the inventory than determined from the receptor allocation. Under-reporting of fugitive VOC emissions from petroleum refineries is an ongoing problem. Emissions from graphic arts industries are underestimated in the inventory partly because of the broad characterization of the emission factor (i.e., mass emitted/capita), which may be less useful when specific locations and days are under consideration. This study also demonstrates the effectiveness of the CMB approach when used prospectively to track the implementation of emission control strategies. While vehicle emission concentrations were unchanged from 1988 to 1993, measurement-based CMB results suggest a decrease in evaporative emissions during this time period resulting from Reid vapor pressure (RVP) reductions (from 11.0 psi in 1988 to 8.6 psi in 1993) and fleet turnover. Changes in emissions from coke plants and petroleum refineries were also seen in the CMB allocations for these sources.  相似文献   
4.
Governments differ significantly in their attempts to mitigate the effects of mining disturbance. The approaches of Australia, Canada and the United States are reviewed here, relative to coal-mining reclamation. State and provincial examples (Queensland, Alberta and Montana) are used to illustrate legislation and planning below the national level. This paper explores three main issues that contribute to coal-mining reclamation: governmental level of legislation and planning; legislative scope; and inter-governmental co-ordination. The legislative histories vary, but are young and evolving. All require the submission of a reclamation plan before granting mining permits, enforce reclamation standards by security deposits and contain provisions for non-compliance. Australia and Canada are only beginning to address reclamation planning at the national level, whereas the United States has done so since 1977. The relationship to the environmental impact assessment process is uneven across the three nations. The United States and Canada have a larger percentage of their mined landscapes in a reclamation process, due partly to more stringent regulation. Reclamation effectiveness seems to centre less on centralization versus decentralization, and more on comprehensive scope, preventive approaches and multi-level governmental co-ordination.  相似文献   
5.
Three bench-scale rock filters containing 0.6 m of gravel were used in this investigation. Two of the filters were planted withSagittaria Iancifolia andScirpus validus, while the third filter was an unvegetated control filter. The wastewater directed through these systems was a synthetic mixture containing nutrient broth as the carbon source. An 80-day experiment was run on the filters using eight combinations of two flow rates and four influent biochemical oxygen demand (BOD5) concentrations, each combination remaining constant for ten days. These combinations resulted in BOD5 surface loadings from 4.63–30.96 g/day/m2. From other studies of batch and continuous flow rock-plant filter systems, the first-order BOD5 reaction rate constant was found to decrease exponentially with detention time. In this study, however, little correlation was found between BOD5 loading rate and removal percentages, which averaged 69%, 57%, and 47% for theScirpus, Sagittaria, and control systems, respectively. This is probably due to the relatively small change in detention times studied and the short time period of each loading rate. Oxidation/reduction potential (ORP) and dissolved oxygen (DO) measurements within these systems indicated that no free oxygen was available at any depth. Total Kjeldahl nitrogen (TKN) removal was higher in the plant systems relative to the control, with theScirpus system achieving a higher overall removal than theSagittaria system.  相似文献   
6.
Remote sensing and geographical information systems are used to analyze landscapes important to species of conservation concern. The accuracy of the methods depends on how closely habitat mapping classes are linked to population demography. Habitat use by Florida Scrub Jays ( Aphelocoma c. coemlescens ) was quantified using circular plots. Habitat variation was mapped using high-resolution aerial photography on a site where all Florida Scrub Jays were color-banded. Nest site selection, nest success, yearling production, and breeder survival were measured within Florida Scrub Jay territories. Habitat use was lowest in areas without scrub oaks or areas within 136 m from forests. Open oak, dominated by scrub oaks and open sandy areas, had the highest use and nest success among habitats. Open oak occurred as narrow patches ( <20 m wide) in landscapes dominated by matrix habitat (palmetto-lyonia and swale marshes). Most wide patches (>50 m) of open oak were potential population sources, where reproduction exceeded mortality. Areas with patches of open oak of less than 1 ha were usually population sinks. Open oak occurred as less flammable patches in a landscape subject to frequent fires. Population sources varied temporally and spatially with fires and site potential to support scrub oaks (soils). Analyses of landscape patterns and dynamics indicated that habitat mapping should not only include patches of currently optimal habitat but should also include landscapes associated with open oak. The influences of landscape patterns on habitat use, reproductive success, survival, and territory size can be quantified at different scales starting with attributes associated with habitat patches, nest sites, and territories. Potential mapping errors occur, however, when habitats are used to quantify the areal extent of sources and sinks and similar population attributes important for species persistence.  相似文献   
7.
Abstract: Water right transfers are one of the basic means of implementing changes in water use in the highly appropriated water resource systems of the western United States. Many of these systems are governed by the Prior Appropriation Doctrine, which was not originally intended for application to ground‐water pumping and the conjunctive management of ground water and surface water, and thus creates an administrative challenge. That challenge results from the fact that ground‐water pumping can affect all interconnected surface‐water bodies and the effects may be immeasurably small relative to surface water discharge and greatly attenuated in time. Although we may have the ability to calculate the effects of ground‐water pumping and transfers of pumping location on surface‐water bodies, mitigating for all the impacts of each individual transfer is sufficiently inefficient that it impedes the transfer process, frustrates water users, and consequently inhibits economic development. A more holistic approach to ground‐water right transfers, such as a ground‐water accounting or banking scheme, may adequately control transfer third‐party effects while reducing mitigation requirements on individual transfers. Acceptance of an accounting scheme can accelerate the transfer process, and possibly reduce the administrative burden.  相似文献   
8.
The integration of non-continuous processes such as a milk powder plant presents a challenge for existing process integration techniques. Current techniques are generally based on steady and continuous operation which for some industries is not the case. Milk production varies considerably during the year as dairy cows in New Zealand are grazed on pasture. In this paper the potential for indirect heat transfer between the several plants using a heat recovery loop and stratified tank at a typical New Zealand dairy factory is investigated. The maximum amount of heat recovery is calculated for a range of recirculation loop temperatures. The maximum amount of heat recovery can be increased considerably if the temperature of the hot fluid in the recirculation loop is varied depending on which condition the site is operating under.  相似文献   
9.
This paper describes the development and evaluation of the Pedestrian Surface (PS) priority indicator (PS priority indicator). This tool was developed to comply with Australian Standard AS 4360: 2004 (Risk Management). Pedestrian surfaces should be evaluated to identify hazards and assess the level of risk calculated in order to ensure that the surfaces do not have a significant level of risk. If a significant level of risk is present, then control measures should be implemented. Pedestrian surfaces for the purposes of this research are classified as same level surfaces (excluding stairways) where pedestrians on foot (or by wheelchair) travel from one place to another.  相似文献   
10.
The Environmental Monitoring and Assessment Program (EMAP) is proposing an ambitious agenda to assess the status of streams and estuaries in a 12-State area of the western United States by the end of 2003. Additionally, EMAP is proposing to access landscape conditions as they relate to stream and estuary conditions across the west. The goal of this landscape project is to develop a landscape model that can be used to identify the relative risks of streams and estuaries to potential declines due to watershed-scale, landscape conditions across the west. To do so, requires an understanding of quantitative relationships between landscape composition and pattern metrics and parameters of stream and estuary conditions. This paper describes a strategic approach for evaluating the degree to which landscape composition and pattern influence stream and estuary condition, and the development and implementation of a spatially-distributed, landscape analysis approach.  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