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   44858篇
  免费   511篇
  国内免费   544篇
安全科学   1355篇
废物处理   2022篇
环保管理   5761篇
综合类   7590篇
基础理论   12052篇
环境理论   28篇
污染及防治   11613篇
评价与监测   2905篇
社会与环境   2300篇
灾害及防治   287篇
  2022年   405篇
  2021年   406篇
  2020年   303篇
  2019年   376篇
  2018年   627篇
  2017年   658篇
  2016年   1016篇
  2015年   765篇
  2014年   1172篇
  2013年   3543篇
  2012年   1441篇
  2011年   1976篇
  2010年   1613篇
  2009年   1635篇
  2008年   1973篇
  2007年   2050篇
  2006年   1795篇
  2005年   1522篇
  2004年   1425篇
  2003年   1499篇
  2002年   1347篇
  2001年   1727篇
  2000年   1212篇
  1999年   742篇
  1998年   537篇
  1997年   557篇
  1996年   560篇
  1995年   658篇
  1994年   646篇
  1993年   551篇
  1992年   571篇
  1991年   545篇
  1990年   593篇
  1989年   549篇
  1988年   473篇
  1987年   450篇
  1986年   398篇
  1985年   406篇
  1984年   470篇
  1983年   412篇
  1982年   446篇
  1981年   387篇
  1980年   321篇
  1979年   343篇
  1978年   318篇
  1977年   250篇
  1975年   259篇
  1974年   250篇
  1972年   248篇
  1971年   248篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
51.
  1. The Air Polluttion Monitoring System has got a significant development of late, which is in direct relation with a considerable extention and improvement of the observation network in cities and industrial areas, with creation of a new network for assessing regional and global background of the atmosphere pollution, as well as with the wide involvement of meteorologists to monitoring organization.
  2. While developing a new global monitoring system, it is necessary to take into account its relationship with the local monitoring within the region of air pollution sources, i.e. at the \lsimpact\rs level. The need in such an account is dictated first of all by the physics of pollutant spreading that states: changes in air pollution over large territories must be in a certain agreement with greater changes in the vicinity of emission sources. Methods applied in the global and local monitoring have also a number of common peculiarities. White organizing regional network for observations of the background pollution of the atmosphere twin stations (one of the pair of stations located outside the city boundaries in a small community, and the other, in the nearest city with the population of 200–400 thousand inhabitants) were established in the U.S.S.R. and in a number of socialist countries in Europe.
  3. Implementation of the twin-station principles in the U.S.S.R. has contributed to data interpretation and representativity assessment as well as to correction of the station location. Observation results from the Soviet background stations and those abroad have been compared by now according to a number of indices.
  4. The correlation of monitoring systems of various scales tells positively both on mutual improvement and completion of observational methods. The methods of obtaining integral characteristics of air pollution were used for the global monitoring, in particular spectral actinometric observations and chemical analysis of the precipitation composition. Now they find still wider employment. Thus methods of spectral actinometric measurements and data processing were used to estimate the degree of aerosol pollution of a number of industrial centres. The theory of solar radiation spreading and aerosol contents determination in urban atmosphere has also been developed. It is a generalization of an earlier developed theory, used to estimate global atmosphere pollution basing on actinometric data. The organization of precipitation collection and analysis on a network of stations around Leningrad and in Donbass area enables us to compare the admixture content in precipitations falling in industrial and agricultural areas.
  5. A considerable increase of possibilities to measure microconcentrations of sulphur dioxide, nitrogen oxides and of a number of other pollutants is connected with the use of solid solvents for sampling. Their use will allow to avoid establishment of special laboratories at background stations and only send samples by post for their analysis in centralized laboratories.
They will also allow to considerably increase precision and accuracy of measurements. The international comparisons of methods of air pollution measurements on the background level allow to judge about the effiency of these methods.  相似文献   
52.
Determination of biomass burning emission factors: Methods and results   总被引:3,自引:0,他引:3  
Biomass burning, in a broad sense, encompasses different burning practices, including open and confined burnings, and different types of vegetation. Emission factors of gaseous or particulate trace compounds are directly dependent both on the fuel type and the combustion process. Emission factors are generally calculated by stoichiometric considerations using the carbon mass balance method, applied either to combustion chamber experiments or to field experiments based on ground-level measurements or aircraft sampling in smoke plumes. There have been a number of experimental studies in the last 10 years to investigate wildfires in tropical, temperate, or boreal regions. This article presents an overview of measurement methods and experimental data on emission factors of reactive or radiatively active trace compounds, including trace gases and particles. It focuses on fires in tropical regions, that is, forest and savanna fires, agricultural burns, charcoal production, use of fuelwood, and charcoal combustion.  相似文献   
53.
54.
55.
56.
57.
58.
59.
60.
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