全文获取类型
收费全文 | 24836篇 |
免费 | 337篇 |
国内免费 | 176篇 |
专业分类
安全科学 | 773篇 |
废物处理 | 1035篇 |
环保管理 | 3823篇 |
综合类 | 3864篇 |
基础理论 | 6933篇 |
环境理论 | 18篇 |
污染及防治 | 6140篇 |
评价与监测 | 1560篇 |
社会与环境 | 1020篇 |
灾害及防治 | 183篇 |
出版年
2022年 | 173篇 |
2021年 | 184篇 |
2020年 | 156篇 |
2019年 | 186篇 |
2018年 | 332篇 |
2017年 | 363篇 |
2016年 | 548篇 |
2015年 | 413篇 |
2014年 | 612篇 |
2013年 | 1953篇 |
2012年 | 767篇 |
2011年 | 1061篇 |
2010年 | 839篇 |
2009年 | 853篇 |
2008年 | 1051篇 |
2007年 | 1074篇 |
2006年 | 956篇 |
2005年 | 829篇 |
2004年 | 808篇 |
2003年 | 755篇 |
2002年 | 733篇 |
2001年 | 834篇 |
2000年 | 659篇 |
1999年 | 386篇 |
1998年 | 329篇 |
1997年 | 330篇 |
1996年 | 334篇 |
1995年 | 399篇 |
1994年 | 373篇 |
1993年 | 339篇 |
1992年 | 328篇 |
1991年 | 315篇 |
1990年 | 326篇 |
1989年 | 313篇 |
1988年 | 274篇 |
1987年 | 272篇 |
1986年 | 260篇 |
1985年 | 236篇 |
1984年 | 293篇 |
1983年 | 252篇 |
1982年 | 316篇 |
1981年 | 259篇 |
1980年 | 214篇 |
1979年 | 214篇 |
1978年 | 210篇 |
1977年 | 166篇 |
1974年 | 164篇 |
1973年 | 164篇 |
1972年 | 154篇 |
1971年 | 155篇 |
排序方式: 共有10000条查询结果,搜索用时 140 毫秒
831.
832.
833.
The ecosystem services (ES) concept is being increasingly incorporated into environmental policy formulation and management approaches. The Corporate Ecosystem Services Review (ESR) is a framework used to assess the dependence and impact that a business has on ES. The success of the corporate experience of ES assessment provides an opportunity for adaption for local authority decision making. In this paper, the ESR tool was adapted to the South African setting at a local government level, and tested at two sites in the Msunduzi Municipality, KwaZulu-Natal. In testing the tool and gathering feedback from key stakeholders, it was found that there are both opportunities and challenges to this approach. Overall, however, it provides an opportunity for the systematic inclusion of ES assessment into existing regulatory frameworks for land-use planning and Integrated Environmental Management, whether in a strategic application, at a broader spatial (municipal) scale or in a specific locale within the municipality. 相似文献
834.
835.
Recreational Diving Impacts on Coral Reefs and the Adoption of Environmentally Responsible Practices within the SCUBA Diving Industry 总被引:1,自引:0,他引:1
836.
837.
838.
Bison and cattle grazing management,bare ground coverage,and links to suspended sediment concentrations in grassland streams
下载免费PDF全文
![点击此处可从《Journal of the American Water Resources Association》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Bartosz P. Grudzinski Melinda D. Daniels Kyle Anibas David Spencer 《Journal of the American Water Resources Association》2016,52(1):16-30
This study quantified the impact of bison and cattle grazing management practices on bare ground coverage at the watershed, riparian, and forested riparian scales within the Flint Hills ecoregion in Kansas. We tested for correlations between bare ground coverage and fluvial suspended sediment concentrations during base‐flow and storm‐flow events. We used remotely sensed imagery combined with field surveys to classify ground cover and quantify the presence of bare ground. Base‐flow water samples were collected bi‐monthly during rain‐free periods and 24 h following precipitation events. Storm‐flow water samples were collected on the rising limb of the hydrograph, using single‐stage automatic samplers. Ungrazed treatments contained the lowest coverage of bare ground at the watershed, riparian, and forested riparian scales. Bison treatments contained the highest coverage of bare ground at the watershed scale, while high‐density cattle treatments contained the highest coverage of bare ground at the riparian and forested riparian scales. In bison and cattle‐grazed treatments, a majority of bare ground was located near fence lines, watershed boundaries, and third‐ and fourth‐order stream segments. Inorganic sediment concentrations at base flow were best predicted by riparian bare ground coverage, while storm‐flow sediment concentrations were best predicted by watershed scale bare ground coverage. 相似文献
839.
Benchmarking Optical/Thermal Satellite Imagery for Estimating Evapotranspiration and Soil Moisture in Decision Support Tools
下载免费PDF全文
![点击此处可从《Journal of the American Water Resources Association》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Jan M.H. Hendrickx Richard G. Allen Al Brower Aaron R. Byrd Sung‐ho Hong Fred L. Ogden Nawa Raj Pradhan Clarence W. Robison David Toll Ricardo Trezza Todd G. Umstot John L. Wilson 《Journal of the American Water Resources Association》2016,52(1):89-119
Generally, one expects evapotranspiration (ET) maps derived from optical/thermal Landsat and MODIS satellite imagery to improve decision support tools and lead to superior decisions regarding water resources management. However, there is lack of supportive evidence to accept or reject this expectation. We “benchmark” three existing hydrologic decision support tools with the following benchmarks: annual ET for the ET Toolbox developed by the United States Bureau of Reclamation, predicted rainfall‐runoff hydrographs for the Gridded Surface/Subsurface Hydrologic Analysis model developed by the U.S. Army Corps of Engineers, and the average annual groundwater recharge for the Distributed Parameter Watershed Model used by Daniel B. Stephens & Associates. The conclusion of this benchmark study is that the use of NASA/USGS optical/thermal satellite imagery can considerably improve hydrologic decision support tools compared to their traditional implementations. The benefits of improved decision making, resulting from more accurate results of hydrologic support systems using optical/thermal satellite imagery, should substantially exceed the costs for acquiring such imagery and implementing the remote sensing algorithms. In fact, the value of reduced error in estimating average annual groundwater recharge in the San Gabriel Mountains, California alone, in terms of value of water, may be as large as $1 billion, more than sufficient to pay for one new Landsat satellite. 相似文献
840.
Characterizing Drought in Irrigated Agricultural Systems: The Surface Water Delivery Index (SWDI)
下载免费PDF全文
![点击此处可从《Journal of the American Water Resources Association》网站下载免费的PDF全文](/ch/ext_images/free.gif)
David J. Hoekema Jae Hyeon Ryu 《Journal of the American Water Resources Association》2016,52(3):737-755
Quantifying surface water shortages in arid and semiarid agricultural regions is challenging because limited water supplies are distributed over long distances based on complex water management systems constrained by legal, economic, and social frameworks that evolve with time. In such regions, the water supply is often derived in a climate dramatically different from where the water is diverted to meet agricultural demand. The existing drought indices which rely on local climate do not portray the complexities of the economic and legal constraints on water delivery. Nor do these indices quantify the shortages that occur in drought. Therefore, this research proposes a methodological approach to define surface water shortages in irrigated agricultural systems using a newly developed index termed the Surface Water Delivery Index (SWDI). The SWDI can be used to uniformly quantify surface water deficits/shortages at the end of the irrigation season. Results from the SWDI clearly illustrate how water shortages in droughts identified by the existing indices (e.g., SPI and PDSI) vary strongly both within and between basins. Some surface water entities are much more prone to water shortages than other entities based both on their source of water supply and water right portfolios. 相似文献