全文获取类型
收费全文 | 101篇 |
免费 | 0篇 |
国内免费 | 2篇 |
专业分类
环保管理 | 86篇 |
综合类 | 5篇 |
基础理论 | 5篇 |
污染及防治 | 5篇 |
评价与监测 | 2篇 |
出版年
2017年 | 2篇 |
2016年 | 2篇 |
2015年 | 1篇 |
2011年 | 1篇 |
2010年 | 1篇 |
2009年 | 10篇 |
2008年 | 8篇 |
2007年 | 8篇 |
2006年 | 10篇 |
2005年 | 5篇 |
2004年 | 4篇 |
2003年 | 5篇 |
2002年 | 8篇 |
2001年 | 4篇 |
2000年 | 4篇 |
1999年 | 3篇 |
1998年 | 1篇 |
1997年 | 2篇 |
1996年 | 1篇 |
1995年 | 4篇 |
1994年 | 3篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1990年 | 3篇 |
1988年 | 3篇 |
1987年 | 4篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1982年 | 1篇 |
排序方式: 共有103条查询结果,搜索用时 15 毫秒
101.
Wetland ecosystems are profoundly affected by altered nutrient and sediment loads received from anthropogenic activity in
their surrounding watersheds. Our objective was to compare a gradient of agricultural and urban land cover history during
the period from 1949 to 1997, with plant and soil nutrient concentrations in, and sediment deposition to, riparian wetlands
in a rapidly urbanizing landscape. We observed that recent agricultural land cover was associated with increases in Nitrogen
(N) and Phosphorus (P) concentrations in a native wetland plant species. Conversely, recent urban land cover appeared to alter
receiving wetland environmental conditions by increasing the relative availability of P versus N, as reflected in an invasive,
but not a native, plant species. In addition, increases in surface soil Fe content suggests recent inputs of terrestrial sediments
associated specifically with increasing urban land cover. The observed correlation between urban land cover and riparian wetland
plant tissue and surface soil nutrient concentrations and sediment deposition, suggest that urbanization specifically enhances
the suitability of riparian wetland habitats for the invasive species Japanese stiltgrass [Microstegium vimenium (Trinius) A. Camus]. 相似文献
102.
Thomas Hruby 《Environmental management》2009,43(6):1219-1243
Regulators protecting riparian areas need to understand the integrity, health, beneficial uses, functions, and values of this
resource. Up to now most methods providing information about riparian areas are based on analyzing condition or integrity.
These methods, however, provide little information about functions and values. Different methods are needed that specifically
address this aspect of riparian areas. In addition to information on functions and values, regulators have very specific needs
that include: an analysis at the site scale, low cost, usability, and inclusion of policy interpretations. To meet these needs
a rapid method has been developed that uses a multi-criteria decision matrix to categorize riparian areas in Washington State,
USA. Indicators are used to identify the potential of the site to provide a function, the potential of the landscape to support
the function, and the value the function provides to society. To meet legal needs fixed boundaries for assessment units are
established based on geomorphology, the distance from “Ordinary High Water Mark” and different categories of land uses. Assessment
units are first classified based on ecoregions, geomorphic characteristics, and land uses. This simplifies the data that need
to be collected at a site, but it requires developing and calibrating a separate model for each “class.” The approach to developing
methods is adaptable to other locations as its basic structure is not dependent on local conditions. 相似文献
103.
We investigated whether fish assemblage structure in southern Appalachian streams differed with historical and contemporary
forest cover. We compared fish assemblages in 2nd–4th order streams draining watersheds that had increased forest cover between 1950 and 1993 (i.e., reforesting watersheds). We sampled fish in 50 m reaches during August 2001 and calculated catch-per-unit-effort (CPUE)
by taxonomic, distributional, trophic, reproductive, and thermal metrics. We assigned streams to reforestation categories
based on cluster analysis of years 1950 and 1993 near-stream forest cover. The relationship between forest cover and assemblage
structure was assessed using analysis of variance to identify differences in fish CPUE in five forest cover categories. Streams
contained 23 fish species representing six families, and taxa richness ranged from 1 to 13 at 30 stream sites. Streams with
relatively low near-stream forest cover were different from streams having moderate to high near-stream forest cover in 1950
and 1993. Fish assemblages in streams having the lowest amount of forest cover (53–75%) were characterized by higher cosmopolitan,
brood hider, detritivore/herbivore, intermediate habitat breadths, run-pool dweller, and warm water tolerant fish CPUE compared
to streams with higher riparian forest cover. Our results suggest that fish assemblage’s structural and functional diversity
and/or richness may be lower in streams having lower recent or past riparian forest cover compared to assemblages in streams
having a high degree of near-stream forest cover. 相似文献