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   2442篇
  免费   78篇
  国内免费   430篇
安全科学   90篇
废物处理   145篇
环保管理   222篇
综合类   729篇
基础理论   457篇
环境理论   3篇
污染及防治   926篇
评价与监测   193篇
社会与环境   142篇
灾害及防治   43篇
  2024年   3篇
  2023年   24篇
  2022年   82篇
  2021年   74篇
  2020年   46篇
  2019年   68篇
  2018年   53篇
  2017年   76篇
  2016年   102篇
  2015年   133篇
  2014年   181篇
  2013年   264篇
  2012年   201篇
  2011年   188篇
  2010年   139篇
  2009年   132篇
  2008年   188篇
  2007年   149篇
  2006年   136篇
  2005年   98篇
  2004年   92篇
  2003年   81篇
  2002年   87篇
  2001年   53篇
  2000年   34篇
  1999年   40篇
  1998年   35篇
  1997年   27篇
  1996年   32篇
  1995年   22篇
  1994年   21篇
  1993年   19篇
  1992年   15篇
  1991年   13篇
  1990年   8篇
  1989年   4篇
  1988年   5篇
  1986年   3篇
  1985年   3篇
  1983年   3篇
  1982年   3篇
  1981年   2篇
  1977年   2篇
  1975年   1篇
  1973年   1篇
  1966年   1篇
  1965年   1篇
  1964年   1篇
  1958年   1篇
  1956年   1篇
排序方式: 共有2950条查询结果,搜索用时 468 毫秒
991.
992.
993.
994.
Forest fires represent a major driver of change at the ecosystem and landscape levels in the Mediterranean region. Environmental features and vegetation are key factors to estimate the ecological vulnerability to fire; defined as the degree to which an ecosystem is susceptible to, and unable to cope with, adverse effects of fire (provided a fire occurs). Given the predicted climatic changes for the region, it is urgent to validate spatially explicit tools for assessing this vulnerability in order to support the design of new fire prevention and restoration strategies. This work presents an innovative GIS-based modelling approach to evaluate the ecological vulnerability to fire of an ecosystem, considering its main components (soil and vegetation) and different time scales. The evaluation was structured in three stages: short-term (focussed on soil degradation risk), medium-term (focussed on changes in vegetation), and coupling of the short- and medium-term vulnerabilities. The model was implemented in two regions: Aragón (inland North-eastern Spain) and Valencia (eastern Spain). Maps of the ecological vulnerability to fire were produced at a regional scale. We partially validated the model in a study site combining two complementary approaches that focused on testing the adequacy of model’s predictions in three ecosystems, all very common in fire-prone landscapes of eastern Spain: two shrublands and a pine forest. Both approaches were based on the comparison of model’s predictions with values of NDVI (Normalized Difference Vegetation Index), which is considered a good proxy for green biomass. Both methods showed that the model’s performance is satisfactory when applied to the three selected vegetation types.  相似文献   
995.
996.
997.

The purpose of this article is to analyze the challenges to, and opportunities for, increasing sustainable development (SD) co-benefits delivered by clean development mechanism (CDM) wind power projects in northeastern Brazil and the resulting implications for climate and energy policies. Five methodological phases were met: First, a documentary research was conducted in the main CDM database; second was a literature review, creating the analytical framework and a survey questionnaire needed to assess the SD co-benefits from the projects; third, documentary research was used to enable ex-ante analysis of the SD co-benefits proposed in the CDM Project Design Documents (PDDs); fourth, survey allowed for the analysis of SD co-benefits perceived by project entrepreneurs (ex-post analysis); and finally, a comparison between the ex-ante and ex-post analyses was completed. The results show the importance of carrying out SD co-benefit studies after the implementation of CDM projects in order to learn lessons for new mechanisms of climate governance. The lowest SD co-benefits were water management improvement in the project influence area, soil pollution prevention, health and safety improvements and technology transfer. The greatest opportunities for increasing SD co-benefits come from the environmental licensing process and the strengthening of Corporate Social Responsibility. The greatest challenges are new technology development, stakeholders’ engagement and SD co-benefit audits. We conclude that the improvement of multi-level climate and energy governance plays a key role in increasing SD co-benefits.

  相似文献   
998.
999.
1000.
The contribution of fugitive dust from traffic to air pollution can no longer be ignored in China. In order to obtain the road dust loadings and to understand the chemical characteristics of PM10 and PM2.5 from typical road dust, different paved roads in eight districts of Beijing were selected for dust collection during the four seasons of 2005. Ninety-eight samples from 28 roads were obtained. The samples were resuspended using equipment assembled to simulate the rising process of road dust caused by the wind or wheels in order to obtain the PM10 and PM2.5 filter samples. The average road dust loading was 3.82 g m − 2, with the highest of 24.22 g m − 2 being in Hutongs in the rural–urban continuum during winter. The road dust loadings on higher-grade roads were lower than those on lower-grade roads. Attention should be paid to the pollution in the rural–urban continuum areas. The sums of element abundances measured were 16.17% and 18.50% for PM10 and PM2.5 in road dust. The average abundances of OC and EC in PM10 and PM2.5 in road dust were 11.52%, 2.01% and 12.50%, 2.06%, respectively. The abundance of elements, water-soluble ions, and OC, EC in PM10 and PM2.5 resuspended from road dust did not change greatly with seasons and road types. The soil dust, construction dust, dust emitted from burning coal, vehicle exhaust, and deposition of particles in the air were the main sources of road dust in Beijing. Affected by the application of snow-melting agents in Beijing during winter, the amount of Cl −  and Na +  was much higher during that time than in the other seasons. This will have a certain influence on roads, bridges, vegetations, and groundwater.  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