首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   1535篇
  免费   81篇
  国内免费   77篇
安全科学   69篇
废物处理   7篇
环保管理   491篇
综合类   444篇
基础理论   392篇
污染及防治   82篇
评价与监测   62篇
社会与环境   133篇
灾害及防治   13篇
  2024年   3篇
  2023年   11篇
  2022年   16篇
  2021年   35篇
  2020年   34篇
  2019年   23篇
  2018年   22篇
  2017年   32篇
  2016年   43篇
  2015年   41篇
  2014年   43篇
  2013年   70篇
  2012年   50篇
  2011年   107篇
  2010年   92篇
  2009年   123篇
  2008年   103篇
  2007年   101篇
  2006年   103篇
  2005年   88篇
  2004年   69篇
  2003年   73篇
  2002年   61篇
  2001年   61篇
  2000年   62篇
  1999年   27篇
  1998年   26篇
  1997年   27篇
  1996年   14篇
  1995年   24篇
  1994年   14篇
  1993年   11篇
  1992年   13篇
  1991年   8篇
  1990年   10篇
  1989年   6篇
  1988年   13篇
  1987年   6篇
  1986年   3篇
  1985年   6篇
  1984年   5篇
  1983年   2篇
  1981年   2篇
  1980年   2篇
  1978年   1篇
  1975年   1篇
  1973年   1篇
  1972年   2篇
  1971年   1篇
  1970年   1篇
排序方式: 共有1693条查询结果,搜索用时 671 毫秒
771.
Knowledge of the nature conservation value of agricultural land provides a useful input to land-use planning. However, the scarcity of suitable data causes this component to rarely play a role. The paper proposes a methodology based on commonly available data to assess the nature conservation value of agricultural landscapes, and to generate cartographic results to be used as decision variables in planning. The approach relies on landscape ecological indicators and on the application of multicriteria analysis in a Geographical Information System (GIS) context. Four criteria were selected: the agricultural landscape type, the cover of vegetation remnants and marginal features, the length of forest-agriculture ecotones, and the proximity to nature reserves. These criteria were assessed directly or by means of specific indicators, generating maps that were subsequently aggregated through spatial multicriteria analysis. The approach was tested in an alpine area located in Trentino (northern Italy).  相似文献   
772.
This paper develops a comprehensive and objective picture of bird distributions relative to habitats across Britain. Bird species presence/absence data from an extensive field survey and habitat data from the remotely sensed UK Land Cover Map 2000 were analysed in 36,920 tetrads (2 kmx2 km) across Britain (a 65% sample of Britain's c. 240,000 km2). Cluster analysis linked birds to generalised landscapes based on distinctive habitat assemblages. Maps of the clusters showed strong regional patterns associated with the habitat assemblages. Cluster centroid coordinates for each bird species and each habitat were combined across clusters to derive individualised bird-habitat preference indices and examine the importance of individual habitats for each bird species. Even rare species and scarce habitats showed successful linkages. Results were assessed against published accounts of bird-habitat relations. Objective corroboration strongly supported the associations. Relatively scarce coastal and wetland habitats proved particularly important for many birds. However, extensive arable farmland and woodland habitats were also favoured by many species, despite reported declines in bird numbers in these habitats. The fact that habitat-specialists do not or cannot move habitat is perhaps a reason for declining numbers where habitats have become unsuitable. This study showed that there are unifying principles determining bird-habitat relations which apply and can be quantified at the national scale, and which corroborate and complement the cumulative knowledge of many and varied surveys and ecological studies. This 'generality' suggests that we may be able, reliably and objectively, to integrate and scale up such disparate studies to the national scale, using this generalised framework. It also suggests the potential for a landscape ecology approach to bird-habitat analyses. Such developments will be important steps in building models to develop and test the sustainable management of landscapes for birds.  相似文献   
773.
The data on the biological diversity, bioecological features, and geographic variations of segetal plants in the Middle Urals are presented for the first time. It has been shown that apophytic and anthropophytic groups are equally represented among them. Each group is characterized, and the phytocoenotic activity of segetal plants is considered.  相似文献   
774.
Industrial ecology: engineered representation of sustainability   总被引:1,自引:0,他引:1  
Industrial ecology is a relatively new field of research and academic study and is well established in North America and in several Asian countries. However, it has not yet received the attention it deserves in some other important parts of the industrialized world, including Germany. This paper may contribute to a better appreciation of industrial ecology as a tool in the process of sustainable development of economies, social systems, and of aquatic and terrestrial biotopes under the pressure of rapidly changing conditions triggered by global warming and urban growth. For this reason, methods are needed to quantify the successful application of industrial ecology measures. The “Integrated Sustainability Triangle” is introduced as a promising new possibility of quantification and monitoring. It enables justification of the contributions industrial ecology can make to sustainable development. The aggregation of individual economic contributions is assumed to create an overall impetus to the entire industrial sector including the sector of environmental engineering. Thus, the potential of industrial ecology is discussed from the macro-economic and the engineering perspective using the concept of sustainable development as a guiding principle. But the authors come to the conclusion that finding solutions to the pressing problems of our time requires more than collaboration of economy and engineering. It requires joint efforts of the whole spectrum of scientific disciplines in close collaboration with industrial and political stakeholders.  相似文献   
775.
Watson, Tara K., Dorothy Q. Kellogg, Kelly Addy, Arthur J. Gold, Mark H. Stolt, Sean W. Donohue, and Peter M. Groffman, 2010. Groundwater Denitrification Capacity of Riparian Zones in Suburban and Agricultural Watersheds. Journal of the American Water Resources Association (JAWRA) 46(2):237-245. DOI: 10.1111/j.1752-1688.2010.00418.x Abstract: We evaluated the relationship of dominant watershed land use to the structure and nitrogen (N) sink function of riparian zones. We focused on groundwater denitrification capacity, water table dynamics, and the presence and pattern of organically enriched deposits. We used the push-pull method (measurement of 15N-enriched denitrification gases derived from an introduced groundwater plume of 15N-enriched nitrate) to evaluate groundwater denitrification capacity on nine forested wetland riparian sites developed in alluvial or outwash parent materials in southern New England. Three replicate sites were located in each of the three watershed types, those with substantial (1) irrigated agriculture, (2) suburban development, and (3) forest. Soil morphology and water table dynamics were assessed at each site. We found significantly lower mean annual water tables at sites within watersheds with substantial irrigated agriculture or suburban development than forested watersheds. Water table dynamics were more variable at sites within suburban watersheds, especially during the summer. Groundwater denitrification capacity was significantly greater at sites within forested watersheds than in watersheds with substantial irrigated agriculture. Because of the high degree of variability observed in riparian sites within suburban watersheds, groundwater denitrification capacity was not significantly different from either forested or agricultural watersheds. The highly variable patterns of organically enriched deposits and water tables at sites within suburban watersheds suggests that depositional events are irregular, limiting the predictability of groundwater N dynamics in these riparian zones. The variability of riparian N removal in watersheds with extensive suburbia or irrigated agriculture argues for N management strategies emphasizing effective N source controls in these settings.  相似文献   
776.
森林公园旅游开发是区域开发的一种常见类型,其环境影响评价蕴含着丰富、复杂和值得深入研究的内容。本文着重探讨了评价指导思想、技术路线选择、评价指标体系、评价技术方法等几个关键问题,并以山东药乡国家森林公园旅游开发环境影响评价为例,进一步探讨了有关问题的具体解决办法。  相似文献   
777.
Biodiversity and Saving the Earth   总被引:1,自引:0,他引:1  
The challenges for reversing course in our stewardship of the earth's ecosystems has never been greater. Biodiversity is in decline on an unprecedented scale and it is tempting to use this as an indicator of the health of the earth's ecosystems. In fact it is one of a number of indicators that collectively provides information on trends in the condition of ecosystems. But the larger problem is the lack of integration between the social and natural sciences. Mainstream scientists continue to reject the notion that solving environmental problems requires an integration of values and processes. A conceptual model shows how these facets may be brought together. A holistic vision requires the integration of natural, social and health sciences. From this perspective the linkage between biodiversity, ecosystem resilience and management options is more clearly articulated.  相似文献   
778.
环境库兹涅茨曲线的虚幻性及其对可持续发展的现实影响   总被引:11,自引:1,他引:10  
生态环境质量真的能够随着经济发展而改善吗?“先污染、后治理”真的是普遍的发展规律吗?既有的理论一般认为.随着经济的发展.生态环境的质量在经过一个时期的恶化之后,将在一定的发展阶段出现好转.其变化过程呈“倒U曲线”状态.这就是环境Kuznets曲线。作者认为这是一个貌似真实的虚幻.生态环境随着经济发展而好转只可能是局部的、而不可能是整体性的.经济发展与生态维护的双赢目标也同样是难以企及的,经济发展与生态维护只能是基于各种利益关系的权衡。文章还对中国长期推行的几种宏观经济政策的生态环境影响进行了分析,并提出了经济利益与生态利益相权衡的现实主张。  相似文献   
779.
Despite the importance of riparian buffers in providing aquatic functions to forested streams, few studies have sought to capture key differences in ecological and geomorphic processes between buffered sites and forested conditions. This study examines post‐harvest buffer conditions from 20 randomly selected harvest sites within a managed tree farm in the Cascade Mountains of western Washington. Post‐harvest wind derived treefall rates in buffers up to three years post‐harvest averaged 268 trees/km/year, 26 times greater than competition‐induced mortality rate estimates. Treefall rates and stem breakage were strongly tied to tree species and relatively unaffected by stream direction. Observed treefall direction is strongly biased toward the channel, irrespective of channel or buffer orientation. Fall direction bias can deliver significantly more wood recruitment relative to randomly directed treefall, suggesting that models that utilize the random fall assumption will significantly underpredict recruitment. A simple estimate of post‐harvest wood recruitment from buffers can be obtained from species specific treefall and breakage rates, combined with bias corrected recruitment probability as a function of source distance from the channel. Post‐harvest wind effects may reduce the standing density of trees enough to significantly reduce or eliminate competition mortality and thus indirectly alter bank erosion rates, resulting in substantially different wood recruitment dynamics from buffers as compared to unmanaged forests.  相似文献   
780.
Abstract: The capacity of a watershed to urbanize without changing its hydrologic response and the relationship between that response and the spatial configuration of the developed areas was studied. The study was conducted in the Whiteoak Bayou watershed (223 km2), located northwest of Houston, Texas, over an analysis period from 1949 to 2000. Annual development data were derived from parcel data collected by the Harris County Appraisal District. Using these data, measures of the spatial configuration of the watershed urban areas were calculated for each year. Based on regression models, it was determined that the annual runoff depths and annual peak flows depended on the annual precipitation depth, the developed area and the maximum 12‐h precipitation depth on the day and day before the peak flow took place. It was found that, since the early 1970s, when the watershed reached a 10% impervious area, annual runoff depths and peak flows have increased by 146% and 159%, respectively. However, urbanization is responsible for only 77% and 32% of the increase, respectively, while precipitation changes are responsible for the remaining 39% and 96%, respectively. Likewise, an analysis of the development data showed that, starting in the early 1970s, urbanization in the watershed consisted more of connecting already developed areas than of creating new ones, which increases the watershed’s conveyance capacity and explains the change in its response. Before generalizing conclusions, though, further research on other urban watersheds with different urbanization models appears to be necessary.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号