全文获取类型
收费全文 | 890篇 |
免费 | 49篇 |
国内免费 | 139篇 |
专业分类
安全科学 | 26篇 |
废物处理 | 4篇 |
环保管理 | 202篇 |
综合类 | 471篇 |
基础理论 | 77篇 |
污染及防治 | 32篇 |
评价与监测 | 67篇 |
社会与环境 | 143篇 |
灾害及防治 | 56篇 |
出版年
2023年 | 16篇 |
2022年 | 42篇 |
2021年 | 29篇 |
2020年 | 24篇 |
2019年 | 15篇 |
2018年 | 33篇 |
2017年 | 36篇 |
2016年 | 46篇 |
2015年 | 47篇 |
2014年 | 47篇 |
2013年 | 51篇 |
2012年 | 65篇 |
2011年 | 66篇 |
2010年 | 55篇 |
2009年 | 59篇 |
2008年 | 40篇 |
2007年 | 42篇 |
2006年 | 47篇 |
2005年 | 39篇 |
2004年 | 30篇 |
2003年 | 37篇 |
2002年 | 33篇 |
2001年 | 16篇 |
2000年 | 18篇 |
1999年 | 15篇 |
1998年 | 11篇 |
1997年 | 8篇 |
1996年 | 10篇 |
1995年 | 8篇 |
1994年 | 6篇 |
1993年 | 11篇 |
1992年 | 12篇 |
1991年 | 5篇 |
1990年 | 10篇 |
1989年 | 2篇 |
1988年 | 4篇 |
1987年 | 4篇 |
1986年 | 2篇 |
1985年 | 2篇 |
1982年 | 3篇 |
1981年 | 4篇 |
1980年 | 4篇 |
1979年 | 4篇 |
1977年 | 1篇 |
1975年 | 2篇 |
1974年 | 1篇 |
1973年 | 2篇 |
1972年 | 7篇 |
1971年 | 3篇 |
1969年 | 1篇 |
排序方式: 共有1078条查询结果,搜索用时 250 毫秒
521.
长江是中国经济的主动脉,长江流域融汇了我国东、中、西三大地带,汇集了多种经济成分,是中国经济腾飞和向中西部扩展的基地,长江流域的长治久安事关国计民生的大局.但是进入20世纪90年代以来,长江流域洪灾次数呈上升趋势,灾害损失越来越大.为了达到减轻长江洪灾损失的目的,需要对影响长江防洪的一些重要问题进行认真反思,诸如长江防洪规划及治水方针是否需要修正?水土流失对长江防洪究竟有多大影响?何时才能做到人与洪水各得其所?蓄滞洪区如何才能发挥其作用?以及为使长江安澜是否需要制订"长江防洪减灾法"?这些问题都需要认真研究和解决,通过多方研究论证制定出科学的长江防洪规划和治水方针,并以国法的形式确定下来,确保长期实施,不得随意更改,长江才能得以长治久安. 相似文献
522.
A. V. Krusche F. P. de Garvaiho J. M. de Moraes P. B. de Camargo M. V. R. Ballester S. Hornink L. A. Martinelli R. L. Victoria 《Journal of the American Water Resources Association》1997,33(5):1117-1123
ABSTRACT: The spatial and temporal variability of dissolved oxygen (DO), biochemical oxygen demand (BOD), nitrate concentration and total coliform (TC) were investigated at nine sampling stations distributed along the main rivers of the Piracicaba River Basin, a 12,400 km2 catchment located in São Paulo State, one of the most developed regions of Brazil. Spatially, a downstream impoverishment of water quality conditions was observed, as seen by the decrease of DO, and increase of BOD, nitrate, and TC. These changes were probably caused by accumulating downstream discharge of domestic and industrial sewage. Temporal evaluation of 18 years of data showed that DO decreased with time for the majority of the sampling stations, while BOD, nitrate, and TC increased. A law, approved at the end of 1991, proposed a new water tax for river water extraction for industrial and agricultural use. The amount of this tax is determined according to the water quality of the extracted water. Therefore, the evaluation of the water quality status in this basin is a first step to help resources managers to determine the values for this tax. 相似文献
523.
结合大量的实际调查资料,筛选出影响水土流失的因子,建立了预测水土流失的灰色状态模型;并以此分析了气田开发对水土流失的影响,最后作出了影响预测,并提出了相应的措施与对策。 相似文献
524.
How integrated is river basin management? 总被引:2,自引:0,他引:2
Land and water management is increasingly focused upon the drainage basin. Thirty-six terms recently used for schemes of “integrated
basin management” include reference to the subject or area and to the aims of integrated river basin management, often without
allusion to the multiobjective nature. Diversity in usage of terms has occurred because of the involvement of different disciplines,
of the increasing coherence of the drainage basin approach, and the problems posed in particular parts of the world. The components
included in 21 different approaches are analyzed, and, in addition to showing that components related broadly to water supply,
river channel, land, and leisure aspects, it is concluded that there are essentially five interrelated facets of integrated
basin management that involved water, channel, land, ecology, and human activity. Two aspects not fully included in many previous
schemes concern river channel changes and the dynamic integrity of the fluvial system. To clarify the terminology used, it
is suggested that the termcomprehensive river basin management should be used where a wide range of components is involved, whereasintegrated basin management can signify the interactions of components and the dominance of certain components in the particular area.Holistic river basin management is advocated as a term representing an approach that is both fully comprehensive and integrated but also embraces the energetics
of the river system and consideration of changes of river channels and of human impacts throughout the river system. The paradigm
of working with the river can be extended to one of working with the river in the holistic basin context. 相似文献
525.
Kenneth M. Strzepek David H. Marks 《Journal of the American Water Resources Association》1981,17(1):10-15
ABSTRACT: Simulation models constructed to estimate the physical and economic performance of alternative river basin development configurations have been widely used since the start of the Harvard Water Program in the early 1960's. These models have proved useful in choosing from among several potential river basin configurations, since they can rapidly evaluate each configuration's expected performance. However, when dealing with large scale river basin development projects, in which over 50 or 100 alternative reservoirs, irrigation areas, and other components must be considered, it is sometimes quite difficult to effectively use a simulation model to rapidly identify those combinations of projects which best satisfy the development objectives. The purpose of this paper is to describe how a simulation model was used in the analysis of a complex river basin development project in Eastern Europe, and how the problems of scale were confronted and solved. The author's experience on this projet is used to derive a set of general guidelines which may be helpful in other simulation studies. 相似文献
526.
Adrian H. Griffin James C. Wade William E. Martin 《Journal of the American Water Resources Association》1980,16(5):849-855
ABSTRACT: The ground water in the Tucson basin is being drawn faster than it is replenished by nature. The water table is falling, giving rise to several conflicts between water users in the basin. At present, several lawsuits are in progress, including an action by the Papago Tribe against some of the major water users in the basin. Largely because of these difficulties, the State Legislature has established a commission to make proposals for the reform of Arizona's ground water law. The pattern of water use in the basin will undoubtedly be changed by the outcome of the present litigation and the coming reform of Arizona's ground water law. This paper describes how water use in the basin might be affected by changes in the availability of water and gives an account of the effects that these changes in water use could have on the region's economy. The paper concludes that the water problems of the Tucson basin will have little effect on the region at large and that these problems are simply a matter for the Indians and the other water users in the basin to sort out amongst themselves. 相似文献
527.
Michael B. Sonnen Larry C. Davis 《Journal of the American Water Resources Association》1979,15(2):404-419
ABSTRACT: Two analytical methods are presented and demonstrated for evaluating the monetary and nonmonetary benefits of wild rivers. In the traditional benefit-cost context special techniques are required to show that any wild river is worthy of preservation. The methods presented allow for the possibility of low development levels in river basins to be optimal, although advanced development can also be shown to be most efficient in some circumstances. That is, the methods are not directed to the wild condition only but to the entire spectrum of development possibilities. The applications of the methods to two adjacent subbasins in the State of Washington each showed that the currently undeveloped basin should be left in its wild condition, while the partially developed basin next door should be developed even more fully. 相似文献
528.
根据对1998年嫩江、松花江特大洪水的详细调查资料,分析了洪水形成过程和特点。并阐述了洪涝灾害对主要受灾区黑龙江省的国民经济和粮食生产、工业交通、水利设施和人民生活等方面的影响。 相似文献
529.
Philip B. Bedient Wayne C. Huber James P. Heaney 《Journal of the American Water Resources Association》1975,11(3):469-482
ABSTRACT: An environmental simulation model of the Upper St. Johns River Basin, Florida, has been developed in order to predict hydrologic responses under proposed management plans. Land use projections for each of 19 hydrologic planning units are provided by a linear programming analysis of agricultural activities. Inputs to the model include rainfall, runoff, evapotranspiration (ET), aquifer properties, topography, soil types, and vegetative patterns. A water balance is developed in the uplands based on infiltration, ET, surface runoff, and groundwater flow. Valley continuity is based on stage-volume relationship for inflows and outflows and a variable roughness coefficient dependent on vegetative patterns. Land use changes form the basis for predicting hydroperiod variation under alternative management schemes. Plans are ranked according to two criteria, deviation from a natural hydroperiod and flood or drought control provided. Results indicate that (1) a single reservoir without irrigation and (2) floodplain preservation plans are superior to (3) multiple reservoir with irrigation and (4) uncontrolled floodplain plans with regard to both criteria. 相似文献
530.
Otis W. Tempter 《Journal of the American Water Resources Association》1973,9(2):273-283
ABSTRACT Scientists usually regard all water as merely passing through, but in different phases of, the endless hydrologic cycle. The law divides water in the cycle into several different classes. Each is treated separately and generally without consideration of interconnections existing within the cycle. Different rules of law have arisen concerning the ownership and use of each legal class. Under Texas law several classes of surface and ground water are recognized, and weather modification efforts bring yet another class, atmospheric moisture, under consideration. It is instructive to follow water moving through the hydrologic cycle in the Nueces River basin, Texas, as a framework for discussing the substantial interconnections between the various legal classes of water and the difficulties that arise from attempts to apply different rules of law to each class. Strictures imposed by Texas water law can seriously interfer with coordinated, efficient use and management of water resources, as evidenced by the Nueces River basin. Well-recognized, existing water rights in the several phases of the hydrologic cycle make change of these institutional constraints difficult to achieve. 相似文献