全文获取类型
收费全文 | 809篇 |
免费 | 171篇 |
国内免费 | 25篇 |
专业分类
安全科学 | 111篇 |
废物处理 | 15篇 |
环保管理 | 134篇 |
综合类 | 376篇 |
基础理论 | 161篇 |
环境理论 | 2篇 |
污染及防治 | 94篇 |
评价与监测 | 8篇 |
社会与环境 | 71篇 |
灾害及防治 | 33篇 |
出版年
2025年 | 7篇 |
2024年 | 27篇 |
2023年 | 22篇 |
2022年 | 37篇 |
2021年 | 37篇 |
2020年 | 26篇 |
2019年 | 39篇 |
2018年 | 37篇 |
2017年 | 38篇 |
2016年 | 46篇 |
2015年 | 37篇 |
2014年 | 24篇 |
2013年 | 53篇 |
2012年 | 67篇 |
2011年 | 45篇 |
2010年 | 30篇 |
2009年 | 32篇 |
2008年 | 43篇 |
2007年 | 51篇 |
2006年 | 33篇 |
2005年 | 45篇 |
2004年 | 39篇 |
2003年 | 28篇 |
2002年 | 26篇 |
2001年 | 21篇 |
2000年 | 23篇 |
1999年 | 16篇 |
1998年 | 13篇 |
1997年 | 8篇 |
1996年 | 10篇 |
1995年 | 16篇 |
1994年 | 7篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1991年 | 2篇 |
1990年 | 4篇 |
1988年 | 3篇 |
1987年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1977年 | 2篇 |
1974年 | 1篇 |
1971年 | 1篇 |
排序方式: 共有1005条查询结果,搜索用时 15 毫秒
781.
粉煤灰膏体充填是目前最为有效的建筑物下采煤技术,料浆运送是实现充填开采的重要环节。结合数学和弹塑性力学对粉煤灰膏体流变特性进行了理论推导,完成了实验研究,从粒径、比重、颗粒形状和膏体浓度等方面对输送机理进行探讨,结果可为粉煤灰膏体充填开采技术应用提供重要技术支撑。 相似文献
782.
Most conservation and development initiatives assume that rules limiting resource extraction are necessary for ecological sustainability. While this is often true, in some social–ecological systems, unpredictable ecosystem dynamics and limited exploitation technology make it unlikely that people will overstep the ecological threshold, precluding the need for management rules. Here, two kinds of systems can emerge: open access systems in which individuals can meet their needs without cooperating with others, and a cooperative open access system in which social rules are required though management rules are not, because individuals need to cooperate to survive and to prevent erosion of cooperation by free-riders. We provide three brief case studies illustrating cooperative open access: Pantaneiro fishers, Agta hunter-gatherers, and Maasai pastoralists. We conclude that understanding these exceptions is pivotal for a better theoretical understanding of social–ecological systems, and can be valuable in building a strategic approach to conservation. 相似文献
783.
The introduction of formal collective property rights to forest lands appears to have improved both environmental and economic outcomes, but there is limited evidence on how these reforms affect cooperative behavior among local resource users. We propose that when national governments issue collective land rights, they strengthen the collective psychological ownership among coowners and produce increased levels of cooperative behavior. Analyzing data from 213 forest user groups in 10 countries, and a framed field experiment in a subset of sites, we find that collective land titling is associated with significantly higher levels of cooperative behavior including increased levels of trust, more frequent interpersonal interactions related to both forestry and nonforestry activities, more self-governing institutions, and greater equality in resource extraction patterns. 相似文献
784.
生物多样性保护领域中的国际条约设有知识产权条款,知识产权条款发挥鼓励创新的基本功能。现有生物多样性利用中存在的知识产权问题集中在获取和惠益分享、遗传资源公开和利用知识产权产生的利益三方面。随着数字开源运动和数据库的大量兴起,协调型知识产权规则因缺乏强制力,使知识产权条款发挥的效力大打折扣。加之知识产权的专有属性和产业化,使得知识产权和多样性保护之间的冲突加剧。中国积极参与生物多样性保护全球治理,由被动参与者转换为积极推动者,确认和实施知识产权规则,关注数字序列信息的发展并加强农民权利的表达。 相似文献
785.
Xunhong Chen 《Journal of the American Water Resources Association》1998,34(3):603-616
ABSTRACT: A method is presented to analyze time-drawdown data from one or more observation wells for the calculation of four hydraulic parameters for unconfined aquifers: vertical hydraulic conductivity, horizontal hydraulic conductivity, storage coefficient, and specific yield. The hydraulic parameter results are further analyzed for reliability and the possible ranges of the actual parameter values. After verification using a theoretical example, the method was used to analyze pumping test data from 22 observation wells in an unconfined alluvial aquifer near Grand Island, Nebraska. Results indicate that this method can be used to efficiently calculate the four hydraulic parameters in this type of aquifer. The method can also identify the impact of measurement errors on the parameter estimates, and provide ranges of the actual parameter values. The parameter values calculated using this method were compared to those determined using other theories. It is found that this method is very useful for calculating the hydraulic properties from pumping test data and for analyzing the parameter reliability. 相似文献
786.
W. Douglas Morgan 《Journal of the American Water Resources Association》1977,13(4):775-781
ABSTRACT: The property rights theory of the firm is evaluated by comparing the cost structures of a sample of water agencies under two alternative modes of ownership - public and investor owned. On the basis of the sample, investor owned water agencies appear to have lower cost structures. 相似文献
787.
788.
Some believe that provision of private property rights in wildlife on private land provides a powerful economic incentive for nature conservation because it enables property owners to market such wildlife or its attributes. If such marketing is profitable, private landholders will conserve the wildlife concerned and its required habitat. But land is not always most profitably used for exploitation of wildlife, and many economic values of wildlife (such as non-use economic values) cannot be marketed. The mobility of some wildlife adds to the limitations of the private-property approach. While some species may be conserved by this approach, it is suboptimal as a single policy approach to nature conservation. Nevertheless, it is being experimented with, in the Northern Territory of Australia where landholders had a possibility of harvesting on their properties a quota of eggs and chicks of red-tailed black cockatoos for commercial sale. This scheme was expected to provide an incentive to private landholders to retain hollow trees essential for the nesting of these birds but failed. This case and others are analysed. Despite private-property failures, the long-term survival of some wildlife species depends on their ability to use private lands without severe harassment, either for their migration or to supplement their available resources, for example, the Asian elephant. Nature conservation on private land is often a useful, if not essential, supplement to conservation on public lands. Community and public incentives for such conservation are outlined. 相似文献
789.
Relation of Lake Acidification and Recovery to Fish,Common Loon and Common Merganser Occurrence in Algoma Lakes 总被引:3,自引:0,他引:3
Models are needed that predict both spatial and temporal improvements to ecosystems following reductions of acidifying emissions that produce `acid rain'. Logistic regression models were developed for the occurrence of fish and two fish-eatingbirds, common loons (Gavia immer) and common mergansers(Mergus merganser), using monitoring data collected onlakes across Ontario. These models were applied in the Algomaregion, including the Turkey Lakes Watershed (TLW). Using theWaterfowl Acidification Response Modeling System (WARMS), severalSO2 emission reduction scenarios were simulated, i.e. thosecontributing to measured 1982–1986 sulphate deposition levels, 1994levels (corresponding to full implementation of Canadian SO2emission reductions as stipulated in the 1991 Canada/U.S. AirQuality Agreement), 2010 levels (1994 plus full U.S. reductions),and both a 50% and a 75% further reduction beyond 2010 levels. Some habitat improvements in Algoma were predicted under the 2010scenario for all biota, but substantial increases in habitatquality, especially for mergansers, would occur only under further reductions. The TLW showed little change in chemistry orbiota, while lakes near the Montreal River were predicted toimprove substantially. 相似文献
790.
环境利益是人类从环境中获取的维持生命延续与自我发展的效用,以及能动地利用自然环境所形成的各种利益。在环境问题与环境危机的影响下,环境利益的实现必定受到阻碍。《物权法》规定了自然资源物权和环境保护相邻权,却忽视环境利益保护的理念,在物权客体范围与相邻关系等方面亦存在明显局限。应将\"环境利益\"纳入民事立法,尤其是《物权法》中,通过确立环境物权,丰富环境容量使用权、环境保护相邻权的相关内容,实现对《物权法》的完善,促进环境利益的民事法律保护与救济。 相似文献