全文获取类型
收费全文 | 12067篇 |
免费 | 109篇 |
国内免费 | 91篇 |
专业分类
安全科学 | 347篇 |
废物处理 | 457篇 |
环保管理 | 1658篇 |
综合类 | 2125篇 |
基础理论 | 3158篇 |
环境理论 | 8篇 |
污染及防治 | 3035篇 |
评价与监测 | 759篇 |
社会与环境 | 635篇 |
灾害及防治 | 85篇 |
出版年
2022年 | 120篇 |
2021年 | 111篇 |
2020年 | 90篇 |
2019年 | 99篇 |
2018年 | 171篇 |
2017年 | 154篇 |
2016年 | 231篇 |
2015年 | 200篇 |
2014年 | 273篇 |
2013年 | 918篇 |
2012年 | 366篇 |
2011年 | 503篇 |
2010年 | 413篇 |
2009年 | 481篇 |
2008年 | 533篇 |
2007年 | 523篇 |
2006年 | 457篇 |
2005年 | 421篇 |
2004年 | 356篇 |
2003年 | 368篇 |
2002年 | 352篇 |
2001年 | 472篇 |
2000年 | 346篇 |
1999年 | 209篇 |
1998年 | 133篇 |
1997年 | 160篇 |
1996年 | 163篇 |
1995年 | 191篇 |
1994年 | 192篇 |
1993年 | 160篇 |
1992年 | 132篇 |
1991年 | 169篇 |
1990年 | 163篇 |
1989年 | 157篇 |
1988年 | 115篇 |
1987年 | 114篇 |
1986年 | 118篇 |
1985年 | 91篇 |
1984年 | 108篇 |
1983年 | 111篇 |
1982年 | 119篇 |
1981年 | 108篇 |
1980年 | 96篇 |
1979年 | 112篇 |
1978年 | 73篇 |
1977年 | 76篇 |
1975年 | 77篇 |
1973年 | 72篇 |
1972年 | 65篇 |
1967年 | 66篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
Robert B. Olshansky 《Journal of Environmental Planning and Management》1996,39(3):371-386
Landslides continue to be an expensive problem in the U nited States. This paper explores the difficult problem of how to pay for reducing existing landslide risks. The paper examines a hierarchy of methods to cover repair and long term maintenance of unstable areas: assessment districts; homeowner associations; and insurance. It looks at several examples, and finds that costs in all but the worst cases average about $5000 to $15 000 per property. Landslide insurance is shown to be feasible and could be designed so as to encourage mitigation. The paper concludes that an optimal approach for mitigation and compensation would combine insurance with assessment districts. 相似文献
992.
David R. Breininger Vickie L. Larson Brean W. Duncan Rebecca B. Smith Donna M. Oddy Michael F. Goodchild 《Conservation biology》1995,9(6):1442-1453
Remote sensing and geographical information systems are used to analyze landscapes important to species of conservation concern. The accuracy of the methods depends on how closely habitat mapping classes are linked to population demography. Habitat use by Florida Scrub Jays ( Aphelocoma c. coemlescens ) was quantified using circular plots. Habitat variation was mapped using high-resolution aerial photography on a site where all Florida Scrub Jays were color-banded. Nest site selection, nest success, yearling production, and breeder survival were measured within Florida Scrub Jay territories. Habitat use was lowest in areas without scrub oaks or areas within 136 m from forests. Open oak, dominated by scrub oaks and open sandy areas, had the highest use and nest success among habitats. Open oak occurred as narrow patches ( <20 m wide) in landscapes dominated by matrix habitat (palmetto-lyonia and swale marshes). Most wide patches (>50 m) of open oak were potential population sources, where reproduction exceeded mortality. Areas with patches of open oak of less than 1 ha were usually population sinks. Open oak occurred as less flammable patches in a landscape subject to frequent fires. Population sources varied temporally and spatially with fires and site potential to support scrub oaks (soils). Analyses of landscape patterns and dynamics indicated that habitat mapping should not only include patches of currently optimal habitat but should also include landscapes associated with open oak. The influences of landscape patterns on habitat use, reproductive success, survival, and territory size can be quantified at different scales starting with attributes associated with habitat patches, nest sites, and territories. Potential mapping errors occur, however, when habitats are used to quantify the areal extent of sources and sinks and similar population attributes important for species persistence. 相似文献
993.
994.
Duane B. Oyen Jerald R. Barnard 《Journal of the American Water Resources Association》1975,11(3):483-490
ABSTRACT: This study examines agricultural land use change in the flood plain of the Iowa River as a result of building the Coralville Dam. Estimates of land use change and the benefits realized from the project are compared to the original project study benefits estimated by the Corps of Engineers. An analysis of the factors affecting land use change is carried out through a regression model to determine those variables that explain observed land use change. 相似文献
995.
996.
997.
998.
999.
The Science of Nature - 相似文献
1000.
The effects of predominant currents on the morphology of coral reefs has been studied in the leeward patch reefs of Anegada, British Virgin Islands. Measurements of current velocity and direction and sediment characteristics together with mapping of approximately 31 patch reefs within a 2 km2 area suggest that even under relatively low but constant current velocities (surface current 20 cm sec-1) the major reef-building corals show definite distribution patterns on the reef. The currents also appear to be responsible, in part, for marked orientation and elongation of patch reefs in a north-west/ south-east direction and for a gradation of patch-reef type across the study area. 相似文献