全文获取类型
收费全文 | 2723篇 |
免费 | 76篇 |
国内免费 | 23篇 |
专业分类
安全科学 | 124篇 |
废物处理 | 112篇 |
环保管理 | 833篇 |
综合类 | 264篇 |
基础理论 | 635篇 |
环境理论 | 1篇 |
污染及防治 | 580篇 |
评价与监测 | 158篇 |
社会与环境 | 80篇 |
灾害及防治 | 35篇 |
出版年
2023年 | 14篇 |
2022年 | 20篇 |
2021年 | 29篇 |
2020年 | 20篇 |
2019年 | 32篇 |
2018年 | 50篇 |
2017年 | 46篇 |
2016年 | 62篇 |
2015年 | 53篇 |
2014年 | 54篇 |
2013年 | 289篇 |
2012年 | 108篇 |
2011年 | 137篇 |
2010年 | 114篇 |
2009年 | 119篇 |
2008年 | 158篇 |
2007年 | 144篇 |
2006年 | 127篇 |
2005年 | 97篇 |
2004年 | 77篇 |
2003年 | 98篇 |
2002年 | 87篇 |
2001年 | 57篇 |
2000年 | 45篇 |
1999年 | 25篇 |
1998年 | 43篇 |
1997年 | 28篇 |
1996年 | 38篇 |
1995年 | 47篇 |
1994年 | 32篇 |
1993年 | 44篇 |
1992年 | 37篇 |
1991年 | 16篇 |
1990年 | 25篇 |
1989年 | 17篇 |
1988年 | 24篇 |
1987年 | 16篇 |
1986年 | 22篇 |
1985年 | 29篇 |
1984年 | 31篇 |
1983年 | 28篇 |
1982年 | 38篇 |
1981年 | 35篇 |
1980年 | 32篇 |
1979年 | 22篇 |
1978年 | 23篇 |
1977年 | 11篇 |
1976年 | 8篇 |
1974年 | 7篇 |
1972年 | 9篇 |
排序方式: 共有2822条查询结果,搜索用时 156 毫秒
291.
Incorporating Geological Effects in Modeling of Revegetation Strategies for Salt-Affected Landscapes 总被引:1,自引:0,他引:1
Christopher J. Clarke Richard W. Bell Richard J. Hobbs Richard J. George 《Environmental management》1999,24(1):99-109
The work highlights the difficulties of using standard sampling and statistical techniques to investigate regional phenomena
and presents an integrated approach combining small-scale sampling with broad-scale observations to provide input into a modeling
exercise. It is suggested that such approaches are vital if landscape- and regional-scale processes are to be understood and
managed. The way in which the problem is perceived (holistically or piecemeal) affects the way treatments are designed and
their effectiveness: past approaches have failed to integrate the various scales and processes involved. Effective solutions
require an integrated holistic response. 相似文献
292.
293.
Richard B. Alexander Elizabeth W. Boyer Richard A. Smith Gregory E. Schwarz Richard B. Moore 《Journal of the American Water Resources Association》2007,43(1):41-59
Abstract: Knowledge of headwater influences on the water‐quality and flow conditions of downstream waters is essential to water‐resource management at all governmental levels; this includes recent court decisions on the jurisdiction of the Federal Clean Water Act (CWA) over upland areas that contribute to larger downstream water bodies. We review current watershed research and use a water‐quality model to investigate headwater influences on downstream receiving waters. Our evaluations demonstrate the intrinsic connections of headwaters to landscape processes and downstream waters through their influence on the supply, transport, and fate of water and solutes in watersheds. Hydrological processes in headwater catchments control the recharge of subsurface water stores, flow paths, and residence times of water throughout landscapes. The dynamic coupling of hydrological and biogeochemical processes in upland streams further controls the chemical form, timing, and longitudinal distances of solute transport to downstream waters. We apply the spatially explicit, mass‐balance watershed model SPARROW to consider transport and transformations of water and nutrients throughout stream networks in the northeastern United States. We simulate fluxes of nitrogen, a primary nutrient that is a water‐quality concern for acidification of streams and lakes and eutrophication of coastal waters, and refine the model structure to include literature observations of nitrogen removal in streams and lakes. We quantify nitrogen transport from headwaters to downstream navigable waters, where headwaters are defined within the model as first‐order, perennial streams that include flow and nitrogen contributions from smaller, intermittent and ephemeral streams. We find that first‐order headwaters contribute approximately 70% of the mean‐annual water volume and 65% of the nitrogen flux in second‐order streams. Their contributions to mean water volume and nitrogen flux decline only marginally to about 55% and 40% in fourth‐ and higher‐order rivers that include navigable waters and their tributaries. These results underscore the profound influence that headwater areas have on shaping downstream water quantity and water quality. The results have relevance to water‐resource management and regulatory decisions and potentially broaden understanding of the spatial extent of Federal CWA jurisdiction in U.S. waters. 相似文献
294.
An Integrated Model of Two Fire Regimes 总被引:1,自引:0,他引:1
Richard A. Minnich 《Conservation biology》2001,15(6):1549-1553
295.
296.
297.
Challenges companies face and tools they use to identify and reduce their environmental footprints across their supply chains 相似文献
298.
Coexistence between People and Elephants in African Savannas 总被引:3,自引:0,他引:3
Abstract: The decline in the range and numbers of elephants as a result of expanding human activity in Africa is recognized as one of the continent's more serious conservation problems. Understanding the relationship between human settlement patterns and elephant abundance is fundamental to predicting the viability of elephant populations. The prevailing model of human-elephant interaction predicts a negative linear relationship between rising human density and declining elephant density at a coarse (national or subcontinental) scale. Using observed elephant densities and human population data, we tested this prediction in a study area of 15,000 km2 in northwestern Zimbabwe. The results did not fit a linear model. Elephant and human coexistence occurs at various levels of human density, up to a threshold of human density beyond which elephant populations disappear. This threshold seems to be related to a particular stage in the process of agriculturally transformed land becoming spatially dominant over the natural woodland that constitutes elephant habitat. Within the contexts of conservation and sustainable development in African savannas, investigating spatial relationships between elephant and human abundance should be a priority topic for future research. 相似文献
299.
300.
Laura E Ellison Thomas J O'Shea Daniel J Neubaum Richard A Bowen 《Ecological applications》2007,17(2):620-627
We investigated movements of female big brown bats (Eptesicus fuscus) roosting in maternity colonies in buildings in Fort Collins, Colorado (USA), during the summers of 2002, 2003, and 2005. This behavior can be of public health concern where bats that may carry diseases (e.g., rabies) move among buildings occupied by people. We used passive integrated transponders (PIT tags) to mark individual bats and hoop PIT readers at emergence points to passively monitor the use of building roosts by marked adult females on a daily basis during the lactation phase of reproduction. Multi-strata models were used to examine movements among roosts in relation to ambient temperatures and ectoparasite loads. Our results suggest that high ambient temperatures influence movements. Numbers of mites (Steatonyssus occidentalis) did not appear to influence movements of female bats among building roosts. In an urban landscape, periods with unusually hot conditions are accompanied by shifting of bats to different buildings or segments of buildings, and this behavior may increase the potential for contact with people in settings where, in comparison to their more regularly used buildings, the bats may be more likely to be of public concern as nuisances or health risks. 相似文献