全文获取类型
收费全文 | 2814篇 |
免费 | 181篇 |
国内免费 | 211篇 |
专业分类
安全科学 | 389篇 |
废物处理 | 40篇 |
环保管理 | 1111篇 |
综合类 | 650篇 |
基础理论 | 449篇 |
环境理论 | 3篇 |
污染及防治 | 215篇 |
评价与监测 | 154篇 |
社会与环境 | 100篇 |
灾害及防治 | 95篇 |
出版年
2023年 | 30篇 |
2022年 | 48篇 |
2021年 | 70篇 |
2020年 | 86篇 |
2019年 | 75篇 |
2018年 | 54篇 |
2017年 | 80篇 |
2016年 | 111篇 |
2015年 | 110篇 |
2014年 | 117篇 |
2013年 | 170篇 |
2012年 | 104篇 |
2011年 | 166篇 |
2010年 | 91篇 |
2009年 | 171篇 |
2008年 | 128篇 |
2007年 | 142篇 |
2006年 | 109篇 |
2005年 | 118篇 |
2004年 | 100篇 |
2003年 | 122篇 |
2002年 | 92篇 |
2001年 | 85篇 |
2000年 | 108篇 |
1999年 | 96篇 |
1998年 | 84篇 |
1997年 | 54篇 |
1996年 | 59篇 |
1995年 | 49篇 |
1994年 | 43篇 |
1993年 | 39篇 |
1992年 | 28篇 |
1991年 | 26篇 |
1990年 | 12篇 |
1989年 | 20篇 |
1988年 | 22篇 |
1987年 | 16篇 |
1986年 | 12篇 |
1985年 | 9篇 |
1984年 | 8篇 |
1983年 | 7篇 |
1982年 | 17篇 |
1981年 | 13篇 |
1980年 | 16篇 |
1979年 | 21篇 |
1978年 | 18篇 |
1977年 | 7篇 |
1972年 | 11篇 |
1971年 | 9篇 |
1970年 | 5篇 |
排序方式: 共有3206条查询结果,搜索用时 203 毫秒
821.
David W. York Benjamin C. Dysart Lawrence W. Gahan 《Journal of the American Water Resources Association》1977,13(2):283-298
ABSTRACT: The previous paper in this two-part series presented the basic information of a newly developed mathematical model of multiple-use in natural areas. The model is a unified system for the assessment of cases where development is proposed for relatively natural areas. This paper presents the results of an application of the model to a study of the proposed timber harvest in the Great Santec Swamp in South Carolina. This was done in an effort to demonstrate the utility of the model as a planning and assessment tool. Four potential uses of the Swamp were investigated: logging of hardwood saw timber, hunting, fishing, and nature observation. The model system proved to be extremely useful in the evaluation of potential management schemes and in the selection of the most promising or optimal management plan. 相似文献
822.
Joel A. Diemer Norman Wengert 《Journal of the American Water Resources Association》1977,13(5):885-894
ABSTRACT: The effects of energy development on the water resources of the Colorado River and Great Basin regions is expected to be substantial. Complex physical, economic and institutional interactions may be expected. Most research on these impacts appears single purpose, fragmented, uncoordinated, and often inaccessible to potential users - particularly those with responsibility for energy/water policy and program decisions. A comprehensive, integrative framework for assessing alternative water allocation decisions is outlined, taking a heuristic decision making model for evaluating impacts on maximization of gross (or net) regional product, and regional social welfare, and for assessing the region's contribution to national objectives. The suggested model provides a structure for application and integration of data of various kinds to a range of situations arising from possible impacts from energy proposals. The focus is on water and energy relationships but the model may provide a framework for comprehensive analysis of a variety of environmental actions and resulting system perturbations and effects. 相似文献
823.
Effects of different forest management policies on long-term vegetation development are incorporated into a computer simulation of a western Washington watershed. The response of a Rocky Mountain elk(Cervus canadensis nelsoni) population to these vegetation changes is simulated using information on their differential use of vegetation types. Simulations include: 1) a cessation of timber harvesting leading to an immediate decline in elk members resulting from a reduction in summer habitats; 2) a stable elk population, similar to the present one, resulting from a constant timber harvesting rate, and 3) initial increases in herd size, followed within 50 years by a sharp decrease, resulting from cutting all old growth timber within the next decade and then a cessation of timber harvestings. 相似文献
824.
David O. Cook James W. Demenkow Priya J. Wickramaratne John T. Hannigan 《Journal of the American Water Resources Association》1978,14(2):440-453
ABSTRACT: The town of Jamestown, Rhode Island, located on Conanicut Island in Narragansett Bay, is constructing a secondary treatment plant in order to comply with NPDES regulations. Twelve candidate sites for the plant and marine outfall were initially proposed, and ability to meet State water quality standards at these sites was evaluated using an EPA buoyant plume model. A final outfall site, Taylor Point, was selected by the Town from among the sites considered acceptable. Taylor Point was then subjected to field hydrographic studies including drogue tracking, current recordings, and tracer dye surveys. Results of the measurement program served as input to a two-dimensional effluent dispersion model which predicted excess BOD, coliform, and suspended solids resulting from effluent discharge off Taylor Point. The model predictions demonstrated that State water quality standards can be maintained outside the initial discharge plume. 相似文献
825.
826.
Robert C. Ward 《Journal of the American Water Resources Association》1979,15(2):369-380
ABSTRACT: Regulatory water quality monitoring has evolved to the point where it is a rather complex system encompassing many monitoring purposes and involving many monitoring activities. Lack of a system's perspective of regulatory monitoring hinders the development of effective and efficient monitoring programs to support water quality management. In this paper the regulatory water quality monitoring system is examined in a total systems context. The purposes of regulatory monitoring are reviewed and categorized according to their legal evolution. The activities of regulatory monitoring are categorized and organized into a system which follows the flow of information through the monitoring program. The monitoring purposes and activities are combined to form a monitoring system matrix - a framework within which the total regulatory water quality monitoring system is defined. The matrix, by defining the regulatory monitoring system and clarifying many interactions within the system, provides a basis upon which a more thorough approach to managing, evaluating, and eventually optimizing regulatory monitoring can be developed. 相似文献
827.
James A. Ryan 《Journal of the American Water Resources Association》1979,15(2):461-472
ABSTRACT: A growing concern for environmental quality paralleled with increasing demands on our forest resources has prompted the Washington State Department of Natural Resources to evaluate simulation modeling as a technique for analyzing management decisions in terms of their environmental effects. The evaluation focused on a system of integrated models developed at the University of Washington which simulate processes and activities within the forest ecosystem. A major part of the system is a hydrologic model which predicts changes in discharge, stream temperature, and concentrations of suspended sediment and dissolved oxygen based on information generated by other models representing intensive management practices. The evaluation consisted of applying the system to a 72,000 acre tract of forest land, validating the models with two years of discharge and water quality data from a 93,000 acre watershed, and determining the pertinence of hydrologic modeling for management purposes. Results show several potential uses of hydrologic modeling for forest management planning, especially for analyzing the effects of timber harvesting strategies on water quality. 相似文献
828.
Gert Aron John G. Collins David F. Kibler 《Journal of the American Water Resources Association》1979,15(6):1556-1564
ABSTRACT: It was found that the conventional weighting factor application to hyetograph ordinates results in artificially attenuated storm patterns. A modified weighting procedure is suggested which allows adjustments in the storm timing, peak intensity, and volume but conserves the storm pattern observed at the raingage nearest to the watershed point of interest. The systematic underestimation of peak flood flows, which result from conventional hyetograph weighting, can be avoided by conserving the hyetograph shape from the raingage nearest to any subarea of a modeled watershed and merely applying weighting factors to the rainfall volumes and temporal center of gravity of several hyetographs. 相似文献
829.
Wynn R. Walker Gaylord V. Skogerboe 《Journal of the American Water Resources Association》1975,11(4):751-758
ABSTRACT: The increased agricultural efficiency of the American farmer has been a substantial impetus to this nation's rapid urbanization. In many western regions where total water supplies are limited, urbanization has required the transfer of heretofore agricultural water rights to the urban use. A major problem in such transfers has been the value or price of the water. A management level model of a typical urban water system was developed to optimize water supply, distribution, and wastewater treatment alternatives. The values of agricultural transfers were determined as the cost advantages of increasing allowable reuse levels of urban effluents which imply the use of a downstream right. This procedure is justified by the economic theory of alternative cost. Results for a test application to the Denver, Colorado area indicate values on the order of $1,000 per acre-foot of transferable water depending on effluent water quality restrictions and operational policies. 相似文献
830.
William W. Doyel 《Journal of the American Water Resources Association》1974,10(4):710-718
ABSTRACT: One of the most significant changes m the field of hydrology in the past few years has been the increase m demand for basic data resulting from a new awareness on the part of planners, developers and managers of the essential nature of such data. For many years data collection has been an onerous, routine operation, following which the data were processed and stored - either in publications or file drawers - and the job considered completed. Two developments have changed that picture: the realization that we are drastically altering OUT environment, and the advent of the computer. The first forced us into a recognition of our need for accurate basic data and the second provided a new methodology for handling and using it. The change is evidenced m many ways and numerous activities are underway at both State and Federal level for all facets of the acquisition and handling of water data. The collection of basic data still involves hard routine work and a conscientious-effort to maintain a high level of quality. Hopefully, recognition of the absolutely essential nature of an adequate data base will result in the continued enhancement of the basic data collector and the concomitant increase in support of his activities. 相似文献