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   98141篇
  免费   1238篇
  国内免费   1135篇
安全科学   3875篇
废物处理   3612篇
环保管理   14864篇
综合类   21457篇
基础理论   27494篇
环境理论   73篇
污染及防治   18388篇
评价与监测   5862篇
社会与环境   4256篇
灾害及防治   633篇
  2022年   825篇
  2021年   821篇
  2020年   663篇
  2019年   879篇
  2018年   1258篇
  2017年   1309篇
  2016年   2268篇
  2015年   1863篇
  2014年   2611篇
  2013年   9307篇
  2012年   2518篇
  2011年   3092篇
  2010年   3450篇
  2009年   3557篇
  2008年   2669篇
  2007年   2603篇
  2006年   2798篇
  2005年   2654篇
  2004年   2966篇
  2003年   2812篇
  2002年   2365篇
  2001年   2865篇
  2000年   2305篇
  1999年   1643篇
  1998年   1415篇
  1997年   1411篇
  1996年   1539篇
  1995年   1628篇
  1994年   1525篇
  1993年   1377篇
  1992年   1374篇
  1991年   1346篇
  1990年   1282篇
  1989年   1268篇
  1988年   1108篇
  1987年   1023篇
  1986年   1007篇
  1985年   1084篇
  1984年   1181篇
  1983年   1189篇
  1982年   1185篇
  1981年   1111篇
  1980年   958篇
  1979年   950篇
  1978年   836篇
  1977年   735篇
  1976年   662篇
  1974年   644篇
  1973年   668篇
  1972年   686篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
111.
Five local ecological types based on vegetative communities and two landscape types based on groups of communities, were identified by integrating landform, soil, and vegetation components using multivariate techniques. Elevation and several topographic and soil variables were highly correlated with types of both scales. Landscape ecological types based only on landform and soil variables without vegetation did not correspond with types developed using vegetation. Models developed from these relationships could allow classification and mapping of extensive areas using geographic information systems.  相似文献   
112.
Odorous gases emitted from refuse wastes were scrubbed through activated carbon columns until odor breakthrough occured. Refuse air samples were collected at the influent and effluent ports of the columns for analysis on a gas chromatograph-mass spectrometric system and for odor determination by dynamic olfactometry. Chromatographic profiles of the gases emitted from refuse material were obtained and volatiles identified included carboxylic acids and some sulphur compounds. Organoleptic tests with a dynamic olfactometer revealed that the odor concentration of refuse air averaged about 50 sou m–3. The adsorption capacities of four commercial grades of activated carbon for refuse odor were evaluated and compared. Results indicated that chemically impregnated activated carbons that are commonly used for odor control at sewerage facilities were less cost effective than non-chemically impregnated carbons.  相似文献   
113.
114.
115.
Summary As stated at the beginning of this paper conclusions reached thus far cannot be discussed in this paper. However, a great deal of information is available for examination.EPA displayed its ability to coordinate widely separated laboratories, both Federal and private, into a smooth working team in a very short period of time. A very comprehensive study plan was also developed and implemented quickly. EPA was fortunate to have already had GCA under contract when the emergency arose. In no small part the success of the field effort was due to the managerial and technical abilities of the GCA team.Within a period of 6 weeks a plan was developed, a prime contractor retained, subcontractors hired, and field activities begun. Within a period of 3 months in excess of 8600 field samples were collected and over 12,000 field and QC samples were analyzed. During this same period 2 major data systems were developed, debugged, and placed into operation.In short this EPA project was probably the most comprehensive multimedia field project ever attempted by EPA and certainly the data is being subjected to the most strenuous quality control measures ever imposed by this Agency. The entire program is presently under peer review and the results are being prepared for publication by EPA Headquarters.Note. Originally intended to be published as part of the special issue on Exposure Monitoring: An International Workshop (Las Vegas, Nevada, October 19–22, 1981).  相似文献   
116.
117.
This article reviews the literatureon the use of mosses for monitoring atmospheric metalpollution. It discusses the nature of mosses, themechanisms for moss uptake of metals from the air andwet precipitation, the various forms in which mossesare used for this purpose, and cases in which mosseshave been used for monitoring local hot spots ofpollution, and regional patterns of metal pollution.Also highlighted are the questions of uptake of metalsfrom the substrates, interspecies differences, and acomparison of the effectiveness of mosses with otherindicator materials, among other issues.  相似文献   
118.
Following the decision of the European Parliament and of the Council of 22 December 1998, The European Commission has launched its Fifth Framework Programme for Research, Technological Development and Demonstration (RTD) which will run from 1999 to 2002. The activities will be carried out in the frame of four thematic programmes and three horizontal ones. The first calls for proposals were published in March 1999. Detailed information on the work programme of each activity is available through the Internet at the following address http://www.cordis.lu/fp5 and through direct contact with the programme's help-desks. The present summary gives an outline of environment-related research activities covered by 5th FWP.  相似文献   
119.
The concepts of accuracy and traceability as applied to environmental analysis are still prone to misunderstandings. While accuracy refers to the closeness of analytical values to "true values" (trueness) and among various repetitions (precision), the term traceability implies a link of data obtained to established references through an unbroken chain of comparisons all with stated uncertainties. These misunderstandings, possibly occurring among the analytical community, may have consequences on environmental data interpretation. Recent discussions in the field of environmental speciation analysis illustrated that accuracy and traceability issues are still not firmly established within the environmental chemistry community. This paper discusses this issue, taking methylmercury as a case study.  相似文献   
120.
A number of methods has been proposed for dealing with single-factor or factorial experiments when the requirements for performing the normal theory analysis of variance procedure are not satisfied. This paper suggests the use of the likelihood ratio statistic for testing the main effects and the interaction between the factors in two-way layout of count data following negative binomial distributions with a common dispersion parameter. The likelihood ratio statistic for testing the equality of the dispersion parameters of several groups of count data is also derived. The methods is illustrated by an example concerning the study of spatial and temporal variation of bacterial counts.  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