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   16512篇
  免费   209篇
  国内免费   135篇
安全科学   488篇
废物处理   607篇
环保管理   2387篇
综合类   3125篇
基础理论   4112篇
环境理论   10篇
污染及防治   4011篇
评价与监测   1022篇
社会与环境   964篇
灾害及防治   130篇
  2022年   120篇
  2021年   128篇
  2020年   114篇
  2019年   140篇
  2018年   210篇
  2017年   252篇
  2016年   341篇
  2015年   295篇
  2014年   383篇
  2013年   1377篇
  2012年   489篇
  2011年   656篇
  2010年   526篇
  2009年   589篇
  2008年   675篇
  2007年   685篇
  2006年   661篇
  2005年   526篇
  2004年   514篇
  2003年   522篇
  2002年   446篇
  2001年   563篇
  2000年   444篇
  1999年   252篇
  1998年   202篇
  1997年   200篇
  1996年   217篇
  1995年   226篇
  1994年   218篇
  1993年   215篇
  1992年   223篇
  1991年   212篇
  1990年   210篇
  1989年   180篇
  1988年   156篇
  1987年   139篇
  1986年   163篇
  1985年   164篇
  1984年   167篇
  1983年   171篇
  1982年   164篇
  1981年   169篇
  1980年   157篇
  1979年   146篇
  1978年   114篇
  1977年   130篇
  1974年   109篇
  1973年   91篇
  1972年   109篇
  1971年   92篇
排序方式: 共有10000条查询结果,搜索用时 375 毫秒
61.
Benson C  Clay EJ 《Disasters》1986,10(4):303-316
This paper documents the rapid expansion and changes in food aid flows to Sub-Saharan Africa up to mid-1985. Trends for Sub-Saharan Africa as a whole and for the more seriously affected countries are examined, as are the comparative experiences of food aid of individual countries in the region. Table 11 lists the Sub-Saharan African countries and indicates the most seriously affected food-short countries, as defined by the WFP/FAO task force. It should be borne in mind that some practical problems exist in compiling data on food aid. These include lack of availability of reliable data, especially of most recent data; lack of common terminology and definitions; and different accounting systems. These data problems are sometimes a source of confusion. However, the basic facts are clear: food aid gradually emerged during the early 1980s as a resource too often of considerable significance to many countries of Sub-Saharan Africa. These trends were only accelerated with the crisis of 1984-1985. These facts provide a point of reference for further analysis of the sources of the crisis, its actual dimensions and consequences.  相似文献   
62.
Riebsame WE 《Disasters》1985,9(4):295-300
Three recent cases of climate extremes are studied to identify human impacts and response strategies and to identify common characteristics that may help illuminate the nature of climate hazards. The 1980 heat wave in the central United States, 1981 cold wave in Boston, Massachusetts, and recent flooding and lake level rise in northern Utah, illustrate several important aspects of climate hazards that separate them from the more traditional set of catastrophic events (e.g. tornadoes, hurricanes and earthquakes) usually dealt with by hazards research and management. Among those characteristics are an emphasis on health impacts rather than physical damage, accumulative effects rather than short shocks, a tendency for impacts to accrue to certain socio-economic classes, and relatively slow onset. The management and research implications of these hazard characteristics are explored.  相似文献   
63.
64.
65.
66.
Mitigation and Adaptation Strategies for Global Change - Direct air capture (DAC) is a developing technology for removing carbon dioxide (CO2) from the atmosphere or from low-CO2-containing...  相似文献   
67.

The combination of concentrated solar power–chemical looping air separation (CSP-CLAS) with an oxy-fuel combustion process for carbon dioxide (CO2) capture is a novel system to generate electricity from solar power and biomass while being able to store solar power efficiently. In this study, the computer program Advanced System for Process Engineering Plus (ASPEN Plus) was used to develop models to assess the process performance of such a process with manganese (Mn)-based oxygen carriers on alumina (Al2O3) support for a location in the region of Seville in Spain, using real solar beam irradiance and electricity demand data. It was shown that the utilisation of olive tree prunings (Olea europaea) as the fuel—an agricultural residue produced locally—results in negative CO2 emissions (a net removal of CO2 from the atmosphere). Furthermore, it was found that the process with an annual average electricity output of 18 MW would utilise 2.43% of Andalusia’s olive tree prunings, thereby capturing 260.5 k-tonnes of CO2, annually. Drawbacks of the system are its relatively high complexity, a significant energy penalty in the CLAS process associated with the steam requirements for the loop-seal fluidisation, and the gas storage requirements. Nevertheless, the utilisation of agricultural residues is highly promising, and given the large quantities produced globally (~?4 billion tonnes/year), it is suggested that other novel processes tailored to these fuels should be investigated, under consideration of a future price on CO2 emissions, integration potential with a likely electricity grid system, and based on the local conditions and real data.

  相似文献   
68.
69.
70.
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