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   642篇
  免费   17篇
  国内免费   7篇
安全科学   29篇
废物处理   31篇
环保管理   103篇
综合类   91篇
基础理论   161篇
环境理论   1篇
污染及防治   142篇
评价与监测   43篇
社会与环境   48篇
灾害及防治   17篇
  2023年   12篇
  2022年   8篇
  2021年   15篇
  2020年   22篇
  2019年   11篇
  2018年   33篇
  2017年   18篇
  2016年   25篇
  2015年   23篇
  2014年   12篇
  2013年   52篇
  2012年   29篇
  2011年   40篇
  2010年   27篇
  2009年   33篇
  2008年   22篇
  2007年   28篇
  2006年   24篇
  2005年   22篇
  2004年   13篇
  2003年   21篇
  2002年   28篇
  2001年   5篇
  2000年   4篇
  1999年   9篇
  1998年   3篇
  1997年   7篇
  1996年   5篇
  1995年   7篇
  1994年   3篇
  1993年   4篇
  1992年   7篇
  1991年   3篇
  1990年   7篇
  1989年   11篇
  1988年   6篇
  1987年   3篇
  1986年   10篇
  1985年   5篇
  1984年   3篇
  1983年   4篇
  1982年   4篇
  1981年   4篇
  1980年   4篇
  1979年   3篇
  1978年   2篇
  1972年   2篇
  1966年   2篇
  1965年   2篇
  1931年   2篇
排序方式: 共有666条查询结果,搜索用时 15 毫秒
161.
Biomolecules are vitally important elements in nanoscale science and also in future nanotechnology. Their shape and their chemical and physical functionality can give them a big advantage over inorganic and organic substances. While this becomes most obvious in proteins and peptides, with their complicated, but easily controlled chemistry, other biomolecular substances such as DNA, lipids and carbohydrates can also be important. In this review, the emphasis is on one-dimensional molecules and on molecules that self-assemble into linear structures, and on their potential applications. An important aspect is that biomolecules can act as templates, i.e. their shape and chemical properties can be employed to arrange inorganic substances – such as metals or metal compounds – on the nanometre scale. In particular, rod- and tube-like nanostructures can show physical properties that are different from those of the bulk material, and thus these structures are likely to be a basis for new technology.  相似文献   
162.
We describe a collection of aquatic and wetland habitats in an inland landscape, and their occurrence within a terrestrial matrix, as a “freshwater ecosystem mosaic” (FEM). Aquatic and wetland habitats in any FEM can vary widely, from permanently ponded lakes, to ephemerally ponded wetlands, to groundwater‐fed springs, to flowing rivers and streams. The terrestrial matrix can also vary, including in its influence on flows of energy, materials, and organisms among ecosystems. Biota occurring in a specific region are adapted to the unique opportunities and challenges presented by spatial and temporal patterns of habitat types inherent to each FEM. To persist in any given landscape, most species move to recolonize habitats and maintain mixtures of genetic materials. Species also connect habitats through time if they possess needed morphological, physiological, or behavioral traits to persist in a habitat through periods of unfavorable environmental conditions. By examining key spatial and temporal patterns underlying FEMs, and species‐specific adaptations to these patterns, a better understanding of the structural and functional connectivity of a landscape can be obtained. Fully including aquatic, wetland, and terrestrial habitats in FEMs facilitates adoption of the next generation of individual‐based models that integrate the principles of population, community, and ecosystem ecology.  相似文献   
163.
While the exceptional drought in California ended in 2017, the state is expected to experience similar droughts in the future. Understanding how individuals perceive the causes and consequences of drought will help frame future communication and planning efforts. We surveyed a panel of Californian residents about their perceptions of the 2012–2017 drought. We found a major disconnect in how our respondents perceived drought and water use. Respondents perceived the drought as being caused primarily by climatic factors and underestimated the role human water use, particularly agricultural use, had in exacerbating drought. Comparing our respondents across the state and across socio‐demographics, there were few differences in concern about drought but several differences in how residents thought drought should be managed. Such research can help water managers communicate about the specific concerns the public has about future droughts, as well as address misperceptions about the relationship between drought and water use.  相似文献   
164.
Adaptive management (AM) is a rigorous approach to implementing, monitoring, and evaluating actions, so as to learn and adjust those actions. Existing AM projects are at risk from climate change, and current AM guidance does not provide adequate methods to deal with this risk. Climate change adaptation (CCA) is an approach to plan and implement actions to reduce risks from climate variability and climate change, and to exploit beneficial opportunities. AM projects could be made more resilient to extreme climate events by applying the principles and procedures of CCA. To test this idea, we analyze the effects of extreme climatic events on five existing AM projects focused on ecosystem restoration and species recovery, in the Russian, Trinity, Okanagan, Platte, and Missouri River Basins. We examine these five case studies together to generate insights on how integrating CCA principles and practices into their design and implementation could improve their sustainability, despite significant technical and institutional challenges, particularly at larger scales. Although climate change brings substantial risks to AM projects, it may also provide opportunities, including creating new habitats, increasing the ability to quickly test flow‐habitat hypotheses, stimulating improvements in watershed management and water conservation, expanding the use of real‐time tools for flow management, and catalyzing creative application of CCA principles and procedures.  相似文献   
165.
Alexander D 《Disasters》1989,13(3):228-236
The nature of small, historic settlements in Apennine Italy is described and options for reconstructing them are discussed. Villages and towns are disproportionately vulnerable to damage by even small earthquakes, which can cause substantial changes to their distinctive character. Responses to such events are outlined, including various strategies of evacuation and the process of developing standardized methods for post-disaster architectural survey. Rationales for demolishing damaged buildings, and their role in causing decentralization of the settlements, are discussed. The effects of temporary shelter and contemporary reconstruction plans are evaluated in terms of their impact on the changing urban landscape of such towns. Finally, inconsistencies in government reconstruction funding are shown to be responsible for much of the variability of post-disaster recovery in Italy. Hence, existing theoretical models are of little use in predicting the course of reconstruction.  相似文献   
166.
167.
168.
169.
170.
Objective: Driving under the influence of alcohol is a crime that places the lives of all motorists in danger. Though it is a largely preventable act, impaired driving has accounted for 31 to 38% of fatal crashes across the country over the last decade. When an impaired operator crashes his or her vehicle, there is often a second unit, of which the operator is not impaired, involved in the crash.

Methods: This research looks at approximately 14,000 2-unit crashes involving an impaired operator in the State of Ohio from 2008 through 2012. The research is focused on determining the effects of crash and operator characteristics in 2-unit alcohol-related crashes through the use of 2 mixed logit models.

Results: It is found that several factors have similar effects on the injury severities of both the impaired and nonimpaired operators, including head-on crashes, the use of seat belts, and the deployment of airbags. There are, however, several factors that affect the 2 operators differently. It is found that the impaired operator's injury severity is based on the type and, more important, the size of the vehicle he or she is driving, the roadway geometry, and the speed of the vehicle driven by the nonimpaired operator. The nonimpaired operator is equally affected by the speed of the impaired vehicle as much as his or her own speed, and the nonimpaired operator's injury severity is virtually independent of the type of vehicle being driven.

Conclusions: Researchers may disseminate the results to community groups such as Mothers Against Drunk Driving and Safe Communities to increase awareness of the dangers of drunk driving in an effort to reduce the number of alcohol-related crashes.  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