全文获取类型
收费全文 | 22107篇 |
免费 | 1549篇 |
国内免费 | 3265篇 |
专业分类
安全科学 | 2469篇 |
废物处理 | 398篇 |
环保管理 | 6755篇 |
综合类 | 10181篇 |
基础理论 | 2402篇 |
环境理论 | 54篇 |
污染及防治 | 1326篇 |
评价与监测 | 1523篇 |
社会与环境 | 1286篇 |
灾害及防治 | 527篇 |
出版年
2024年 | 49篇 |
2023年 | 278篇 |
2022年 | 417篇 |
2021年 | 520篇 |
2020年 | 665篇 |
2019年 | 571篇 |
2018年 | 518篇 |
2017年 | 766篇 |
2016年 | 928篇 |
2015年 | 936篇 |
2014年 | 994篇 |
2013年 | 1429篇 |
2012年 | 1455篇 |
2011年 | 1675篇 |
2010年 | 1155篇 |
2009年 | 1315篇 |
2008年 | 970篇 |
2007年 | 1447篇 |
2006年 | 1414篇 |
2005年 | 1108篇 |
2004年 | 1019篇 |
2003年 | 929篇 |
2002年 | 834篇 |
2001年 | 731篇 |
2000年 | 713篇 |
1999年 | 569篇 |
1998年 | 394篇 |
1997年 | 370篇 |
1996年 | 329篇 |
1995年 | 288篇 |
1994年 | 222篇 |
1993年 | 230篇 |
1992年 | 170篇 |
1991年 | 138篇 |
1990年 | 107篇 |
1989年 | 102篇 |
1988年 | 97篇 |
1987年 | 94篇 |
1986年 | 69篇 |
1985年 | 60篇 |
1984年 | 71篇 |
1983年 | 65篇 |
1982年 | 70篇 |
1981年 | 83篇 |
1980年 | 92篇 |
1979年 | 88篇 |
1978年 | 64篇 |
1977年 | 52篇 |
1972年 | 46篇 |
1971年 | 61篇 |
排序方式: 共有10000条查询结果,搜索用时 93 毫秒
81.
In this paper, the problem of optimal timing, when to adopt an environmental policy in a strategic framework is considered. Using real options theory and some basic tools of game theory, we show that, under certain assumptions, a country behaving strategically should wait longer before adopting such a policy than if it behaves unstrategically or within a larger entity. Such a postponed decision is sub-optimal as regards to the environment protection. 相似文献
82.
83.
84.
85.
86.
Selecting Socio-Economic Metrics for Watershed Management 总被引:1,自引:0,他引:1
The selection of social and economic metrics to document baseline conditions and analyze the dynamic relationships between
ecosystems and human communities are important decisions for scientists, managers, and watershed citizens. A large variety
of social and economic data is available but these have limited use without theoretical frameworks. In this paper, several
frameworks for reviewing social-ecosystem relations are offered, namely social sanctions, sense of place, civic structure,
and cultural differences. Underlying all of these frameworks are attitudes, beliefs, values, and norms that affect which questions
are asked and which indicators are chosen. Much work and significant challenges remain in developing a standard set of spatially
based socio-economic metrics for watershed management. 相似文献
87.
88.
A simple, sensitive, convenient and low cost spectrofluorometric technique for determination of quinalphos is described. Quinalphos is decomposed with sodium ethoxide. Resultant sodium diethyl thiophosphate (Na-DETP) is extracted with a cationic fluorescein as ion pair complex into 1-chloro-2-nitrobenzene. The fluorescence of the ion pair, fluorescein-DETP is measured at 530 nm after excitation at 490 nm. This technique is applicable for the determination of quinalphos in water, food grains and vegetable samples up to ng level with Amberlite XAD-4. 相似文献
89.
Mehaffey MH Nash MS Wade TG Ebert DW Jones KB Rager A 《Environmental monitoring and assessment》2005,107(1-3):29-44
The Catskill/Delaware reservoirs supply 90% of New York City’s drinking water. The City has implemented a series of watershed protection measures, including land acquisition, aimed at preserving water quality in the Catskill/Delaware watersheds. The objective of this study was to examine how relationships between landscape and surface water measurements change between years. Thirty-two drainage areas delineated from surface water sample points (total nitrogen, total phosphorus, and fecal coliform bacteria concentrations) were used in step-wise regression analyses to test landscape and surface-water quality relationships. Two measurements of land use, percent agriculture and percent urban development, were positively related to water quality and consistently present in all regression models. Together these two land uses explained 25 to 75% of the regression model variation. However, the contribution of agriculture to water quality condition showed a decreasing trend with time as overall agricultural land cover decreased. Results from this study demonstrate that relationships between land cover and surface water concentrations of total nitrogen, total phosphorus, and fecal coliform bacteria counts over a large area can be evaluated using a relatively simple geographic information system method. Land managers may find this method useful for targeting resources in relation to a particular water quality concern, focusing best management efforts, and maximizing benefits to water quality with minimal costs.The United States Environmental Protection Agency through its Office of Research and Development funded and managed the research described here. It has been subjected to Agency’s administrative review and approved for publication as an EPA document. 相似文献
90.
The increasing use of the landscape by humans has led to important diminutions of natural surfaces. The remaining patches
of wild habitat are small and isolated from each other among a matrix of inhospitable land-uses. This habitat fragmentation,
by disabling population movements and stopping their spread to new habitats, is a major threat to the survival of numerous
plant and animal species. We developed a general model, adaptable for specific species, capable of identifying suitable habitat
patches within fragmented landscapes and investigating the capacity of populations to move between these patches. This approach
combines GIS analysis of a landscape, with spatial dynamic modeling. Suitable habitat is identified using a threshold area
to perimeter ratio. Potential movement pathways of species between habitat patches are modeled using a cellular automaton.
Habitat connectivity is estimated by overlaying habitat patches with movement pathways. The maximum potential population is
calculated within and between connected habitat patches and potential risk of inbreeding within meta-populations is considered.
The model was tested on a sample map and applied to scenario maps of predicted land-use change in the Peoria Tri-county region
(IL). It (1) showed area of natural area alone was insufficient to estimate the consequences on animal populations; (2) underscored
the necessity to use approaches investigating the effect of land-use change spatially through the landscape and the importance
of considering species-specific life history characteristics; and (3) highlighted the model's potential utility as an indicator
of species likelihood to be affected negatively by land-use scenarios and therefore requiring detailed investigation. 相似文献