全文获取类型
收费全文 | 1721篇 |
免费 | 105篇 |
国内免费 | 96篇 |
专业分类
安全科学 | 95篇 |
废物处理 | 24篇 |
环保管理 | 478篇 |
综合类 | 600篇 |
基础理论 | 163篇 |
污染及防治 | 28篇 |
评价与监测 | 26篇 |
社会与环境 | 428篇 |
灾害及防治 | 80篇 |
出版年
2024年 | 5篇 |
2023年 | 26篇 |
2022年 | 27篇 |
2021年 | 45篇 |
2020年 | 38篇 |
2019年 | 35篇 |
2018年 | 27篇 |
2017年 | 70篇 |
2016年 | 73篇 |
2015年 | 63篇 |
2014年 | 44篇 |
2013年 | 85篇 |
2012年 | 125篇 |
2011年 | 145篇 |
2010年 | 107篇 |
2009年 | 78篇 |
2008年 | 60篇 |
2007年 | 100篇 |
2006年 | 103篇 |
2005年 | 80篇 |
2004年 | 68篇 |
2003年 | 56篇 |
2002年 | 64篇 |
2001年 | 39篇 |
2000年 | 39篇 |
1999年 | 32篇 |
1998年 | 39篇 |
1997年 | 32篇 |
1996年 | 18篇 |
1995年 | 29篇 |
1994年 | 19篇 |
1993年 | 19篇 |
1992年 | 21篇 |
1991年 | 8篇 |
1990年 | 13篇 |
1989年 | 3篇 |
1988年 | 9篇 |
1983年 | 5篇 |
1982年 | 12篇 |
1981年 | 2篇 |
1980年 | 8篇 |
1979年 | 9篇 |
1978年 | 4篇 |
1977年 | 5篇 |
1976年 | 4篇 |
1975年 | 3篇 |
1974年 | 6篇 |
1973年 | 4篇 |
1972年 | 3篇 |
1971年 | 7篇 |
排序方式: 共有1922条查询结果,搜索用时 390 毫秒
481.
482.
Akhter U. Ahmed Rajan K. Sampath 《Journal of the American Water Resources Association》1988,24(5):1057-1063
ABSTRACT: This paper investigates and estimates the welfare loss due to monopoly in tubewell irrigation water market in Bangladesh. In this context, an attempt has been made to evaluate the efficacy of the landless irrigation groups. Using cross-sectional data and regression analysis, cost and demand functions for irrigation water are estimated. The study demonstrates the relatively superior performance of the landless groups in terms of economic efficiency in shallow tubewell irrigation operation, in comparison to irrigation operation by the landowners. 相似文献
483.
The estimation of the value of recreation benefits resulting from improved water quality is required for many purposes. In particular, the Water Pollution Control Act of 1980 requires the consideration of the reasonableness of costs of reducing water pollution in relation to benefits to be derived from establishing effluent standards (Clean Water Act of 1977). Recreation is often the most important benefit resulting from water quality improvement. Current methods used to calculate recreation benefits are either not site-specific or are expensive and controversial. This paper presents a relatively simple, inexpensive, and less controversial method of calculating site-specific recreation benefits resulting from improved water quality. It does this by producing an upper bound estimate which often is adequate for the relevant decision. The upper bound estimates is based on two assumptions: 1) there are alternative equivalent substitute sites for the newly augmented water quality site, and 2) the new augmented recreation opportunities at the site will be used to their maximum supply capacity. Clearly, if an upper bound benefit estimate in a cost-benefit ratio does not produce a favorable ratio, no other benefit estimate will. In cases where this estimate produces an ambiguous result resort must be had to other more precise methods of estimation. 相似文献
484.
Burger J 《Environmental monitoring and assessment》2005,101(1-3):147-165
Considerable attention has been devoted to the concerns and perceptions of people residing around contaminated facilities, both brownfields in urban areas and others located in remote and lightly populated areas. This paper examines the concerns of recreationists and sportsmen residing near the Department of Energys (DOE) Brookhaven National Laboratory, in central Long Island, one of the most densely populated regions in the United States, where tourism is of prime importance. On an open-ended question, the greatest concern was pollution, followed by environmental health as a global concern, and human health as a concern for Brookhaven. Accidents/spills, loss of public health, and loss of ecological health were rated highest among a list of concerns, and change in property values was rated lowest. When asked to rank seven concerns, protecting human health was ranked the highest, and economic interests were ranked the lowest. For future land use at Brookhaven, recreational uses were rated the highest, while building houses and factories, and storage of nuclear material were rated the lowest. These data can be used by managers, decision and policy makers, and the general public to assess and manage local and regional environmental concerns and to consider future land uses for decommissioned lands, such as those at Brookhaven. 相似文献
485.
A whole forest optimisation model was employed to examine economic behaviour as it relates to long term, forest productivity decline in the boreal forests of Ontario, Canada. Our productivity investment model(PIM) incorporated a choice between productivity decline as representedby a drop in forest Site Class, and a fee to 'maintain' site productivity. Sensitivity analysis was used to determine the point at which these fees exceeded the value of the differential in timber volume between upper and lower site classes. By varying discount rate, 'productivity investment frontiers' were constructed, which highlight the effects of the magnitude in productivity decline, maintenance fees, and harvest flow constraints upon the occurrence and schedule of productivity declines. In presenting this simple approach to exploring the effects of economic choice upon forest productivity decline, the phenomena of 'natural capital divestment' within forestry is described. 相似文献
486.
Leaf area development, dry weight accumulation and solar energy conversion efficiencies of Phaseolus vulgaris L. cv GLP-2 under two soil moisture levels in two contrasting seasons near Nairobi, Kenya were investigated. The experiment confirms that dry weights and yields of Phaseolus vulgaris are limited by a drought induced decrease in leaf area, leading to less radiation interception as a source for assimilation. However, photosynthetic efficiency in Phaseolus vulgaris also appears to decrease and to contribute to these effects. Finally, an even larger decreases of economic efficiency as obtained in the second season, where stress lasted much later into the season, reveals that such a drought also limits considerably the partitioning and translocation of assimilates to the seeds of Phaseolus vulgaris. The efficiencies obtained are in line with the better literature data for other crops. 相似文献
487.
生态系统调节水量的价值评估——兴山实例 总被引:8,自引:0,他引:8
根据植被类型、坡度和土壤类型,分析了兴山县集水区内不同植被地块调节水量的能力。并且根据水能学的原理,分析了枯水期和洪峰期葛洲坝水电站的发电量与水流量的关系,建立了水流发电模拟模型。在上述分析的基础上,评估了兴山县境内生态系统调节香溪河等河流的水量,改善长江全年来水的均匀度,提高葛洲坝水电站发电效率的经济价值。 相似文献
488.
可持续发展这一概念的出现 ,标志着人类对自然资源利用的短期行为和意识正被维护环境的长期概念所取代。在这一概念的内涵中 ,加以维护并长期保持完好的环境不仅是实现自然环境平衡的需要 ,也是自然资源能够持续地应用于人类的保证。环境经济核算就是以货币化的方法揭示自然资源及环境与经济的特定关系 ,并为可持续发展的综合测度提供基本的数据依据。 相似文献
489.
指标计算法在环境经济损益分析中的应用 总被引:4,自引:0,他引:4
以上海市江桥和闸北2座生活垃圾焚烧厂建设项目为例,采用指标计算法对这2家在不同选址区的建设项目环境经济损益进行了分析。结果表明:江桥生活垃圾焚烧厂项目具有较好的环境经济效益,其环保年净效益为670.69万元,效费比达到1.10。闸北生活垃圾焚烧厂项目的环保年净效益为-764.48万元,效费比为0.64,说明其环境污染控制方案存在明显的不经济性。江桥生活垃圾焚烧厂已投入建设。指标法为2个项目的环境经济损益分析提供了货币量化。 相似文献
490.