全文获取类型
收费全文 | 4964篇 |
免费 | 483篇 |
国内免费 | 1460篇 |
专业分类
安全科学 | 69篇 |
废物处理 | 4篇 |
环保管理 | 1304篇 |
综合类 | 3394篇 |
基础理论 | 538篇 |
污染及防治 | 218篇 |
评价与监测 | 388篇 |
社会与环境 | 810篇 |
灾害及防治 | 182篇 |
出版年
2024年 | 39篇 |
2023年 | 113篇 |
2022年 | 225篇 |
2021年 | 226篇 |
2020年 | 230篇 |
2019年 | 230篇 |
2018年 | 195篇 |
2017年 | 235篇 |
2016年 | 278篇 |
2015年 | 354篇 |
2014年 | 239篇 |
2013年 | 351篇 |
2012年 | 393篇 |
2011年 | 399篇 |
2010年 | 275篇 |
2009年 | 282篇 |
2008年 | 260篇 |
2007年 | 304篇 |
2006年 | 324篇 |
2005年 | 262篇 |
2004年 | 213篇 |
2003年 | 188篇 |
2002年 | 194篇 |
2001年 | 132篇 |
2000年 | 151篇 |
1999年 | 132篇 |
1998年 | 93篇 |
1997年 | 84篇 |
1996年 | 61篇 |
1995年 | 69篇 |
1994年 | 54篇 |
1993年 | 40篇 |
1992年 | 28篇 |
1991年 | 26篇 |
1990年 | 28篇 |
1989年 | 9篇 |
1988年 | 15篇 |
1987年 | 16篇 |
1986年 | 11篇 |
1985年 | 7篇 |
1984年 | 10篇 |
1983年 | 12篇 |
1982年 | 15篇 |
1981年 | 12篇 |
1980年 | 19篇 |
1979年 | 16篇 |
1978年 | 8篇 |
1977年 | 8篇 |
1974年 | 9篇 |
1971年 | 10篇 |
排序方式: 共有6907条查询结果,搜索用时 15 毫秒
461.
462.
463.
黄河断流与黄河的水资源承载力 总被引:2,自引:0,他引:2
分析了黄河断流的时空特征、根源和危害,提出了水资源承载力的概念。黄河的水资源承载力即指在生态系统良性循环的条件下,黄河对人类取用水资源的最大承受能力。只有建立起水资源承载力的概念,人类才会谨慎地取用水资源,小心地保护水资源。 相似文献
464.
黄河三角洲地区东亚飞蝗灾害及防御对策 总被引:2,自引:1,他引:2
通过对黄河三角洲地区东亚飞蝗的调查研究,分析了其发育的气象和环境条件,提出了对东亚飞蝗灾害的防御对策。 相似文献
465.
466.
467.
Kellie B. Vach Joseph M. Eilers Mary V. Santelmann 《Journal of the American Water Resources Association》2002,38(3):773-787
ABSTRACT: Simulated water quality resulting from three alternative future land‐use scenarios for two agricultural watersheds in central Iowa was compared to water quality under current and historic land use/land cover to explore both the potential water quality impact of perpetuating current trends and potential benefits of major changes in agricultural practices in the U.S. Corn Belt. The Soil Water Assessment Tool (SWAT) was applied to evaluate the effect of management practices on surface water discharge and annual loads of sediment and nitrate in these watersheds. The agricultural practices comprising Scenario 1, which assumes perpetuation of current trends (conversion to conservation tillage, increase in farm size and land in production, use of currently‐employed Best Management Practices (BMPs)) result in simulated increased export of nitrate and decreased export of sediment relative to the present. However, simulations indicate that the substantial changes in agricultural practices envisioned in Scenarios 2 and 3 (conversion to conservation tillage, strip intercropping, rotational grazing, conservation set‐asides and greatly extended use of best management practices (BMPs) such as riparian buffers, engineered wetlands, grassed waterways, filter strips and field borders) could potentially reduce current loadings of sediment by 37 to 67 percent and nutrients by 54 to 75 percent. Results from the study indicate that major improvements in water quality in these agricultural watersheds could be achieved if such environmentally‐targeted agricultural practices were employed. Traditional approaches to water quality improvement through application of traditional BMPs will result in little or no change in nutrient export and minor decreases in sediment export from Corn Belt watersheds. 相似文献
468.
Philip W. Gassman Edward Osei Ali Saleh Larry M. Hauck 《Journal of the American Water Resources Association》2002,38(2):423-438
ABSTRACT: A National Pilot Project (NPP) on Livestock and the Environment was initiated in 1992 to help provide solutions to environmental problems associated with livestock production. A major development of the NPP was the Comprehensive Economic and Environmental Optimization Tool‐Livestock and Poultry (CEEOT‐LP), an integrated modeling system designed to produce economic and environmental indicators for alternative policy scenarios applied to intensive livestock production watersheds. The system consists of a farm‐level economic model (FEM) and two environmental models: the field‐scale APEX model and the watershed‐level SWAT model. To date, CEEOT‐LP has been applied to two watersheds in Texas and one in Iowa. Predicted reductions in P losses for two P‐based manure application rate scenarios, relative to baseline conditions, ranged from ?4 to ?54 percent across the three watersheds; however, N loss impacts ranged from a decrease of 34 percent to an increase of 79 percent. For five other alternative scenarios that were simulated for only one watershed, N and P loss impacts ranged between a reduction of 78 percent to an increase of 20 percent. Aggregate watershed‐level economic impacts of the seven scenarios spanned a spectrum of a 27 percent decrease to a 25 percent increase in profit, relative to the baseline. 相似文献
469.
Vinod Lohani David F. Kibler Jeffery Chanat 《Journal of the American Water Resources Association》2002,38(2):439-452
ABSTRACT: This paper describes the integration of a comprehensive hydrological model known as the Hydrological Simulation Program Fortran (HSPF) into a problem solving environment (PSE) for watershed management. The original PSE concept was a structure providing web‐based access to a suite of models, including HSPF and other models of in‐stream hydrodynamics, biological impacts and economic effects, for the watershed‐wide assessment of alternative land use scenarios. The present paper describes only the HSPF integration into the PSE program. Example applications to the 148 square kilometer (57 square mile) Back Creek subwatershed in the upper Roanoke River system (1,479 square kilometers or 571 square miles) in southwest Virginia are used to illustrate important concepts and linkages between land development and hydrological change using hypothetical' what if'scenarios. The features of HSPF and its limitations in this context are discussed. The paper as such is a proof‐of‐concept paper and not a completion report. It is intended to describe the PSE tool building process rather than analysis of the many possible simulation outcomes. However, the dominance of raw imperviousness as a contributor to hydrograph response is apparent in all the PSE simulations described in this paper. 相似文献
470.
Mark R. S. Johannes Kim D. Hyatt Josie K. Cleland Leila Hanslit Margot M. Stockwell 《Journal of the American Water Resources Association》2002,38(2):555-562
ABSTRACT: Watershed stewardship activities throughout North America have evolved into a process that requires more involvement in planning and decision making by community stakeholders. Active involvement of all stakeholders in the process of watershed stewardship is dependent on effective exchange of information among participants, and active involvement of a wide range of stakeholders from “communities of place” as well as those from “communities of interest.” We developed a map‐based stream narrative tool as a means to: (a) assemble a wealth of incompletely documented, “traditional” ecological or natural history observations for rivers or streams; and (b) promote a higher level of active involvement by community stakeholders in contributing to information‐based, watershed management. Creation of stream narratives is intended for use as a tool to actively engage local stakeholders in the development of a more comprehensive information system to improve management for multiple stewardship objectives in watersheds. Completion of map‐based stream narrative atlases provides a valuable supplement to other independent efforts to assemble observations and knowledge about land‐based natural resources covering entire watersheds. We are confident that completion of stream narrative projects will make a valuable addition to the information and decision making tools that are currently available to the public and resource agencies interested in advancing the cause of community‐based approaches to watershed and ecosystem management. 相似文献