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   91038篇
  免费   1218篇
  国内免费   1087篇
安全科学   3751篇
废物处理   3325篇
环保管理   14055篇
综合类   21114篇
基础理论   26399篇
环境理论   73篇
污染及防治   15055篇
评价与监测   5440篇
社会与环境   3579篇
灾害及防治   552篇
  2022年   805篇
  2021年   794篇
  2020年   647篇
  2019年   859篇
  2018年   1118篇
  2017年   1160篇
  2016年   2160篇
  2015年   1833篇
  2014年   2565篇
  2013年   9231篇
  2012年   2207篇
  2011年   2467篇
  2010年   3265篇
  2009年   3394篇
  2008年   2022篇
  2007年   1866篇
  2006年   2300篇
  2005年   2283篇
  2004年   2582篇
  2003年   2423篇
  2002年   2001篇
  2001年   2301篇
  2000年   2019篇
  1999年   1498篇
  1998年   1369篇
  1997年   1361篇
  1996年   1489篇
  1995年   1586篇
  1994年   1475篇
  1993年   1342篇
  1992年   1322篇
  1991年   1295篇
  1990年   1250篇
  1989年   1225篇
  1988年   1059篇
  1987年   990篇
  1986年   991篇
  1985年   1071篇
  1984年   1165篇
  1983年   1171篇
  1982年   1176篇
  1981年   1106篇
  1980年   944篇
  1979年   933篇
  1978年   827篇
  1977年   717篇
  1976年   651篇
  1975年   626篇
  1973年   658篇
  1972年   655篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
111.
112.
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   
113.
114.
115.
116.
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   
117.
Graphical methods can play an important role in the reliable assessment of trends in typically ill behaved river quality data series both as diagnostic tools and as visual corroborative evidence when assumptions required for formal statistical tests are not met. Robust, graphically-oriented trend diagnosis procedures are presented for data series characterized by nonnormal populations, uneven time spacing, nonmonotonic trend and other factors which can create serious problems for standard parametric time series methods. Cleveland's robust locally weighted regression (RLWR) developed for investigating nonlinearity in x-y scatterplots is adapted as a robust/resistant smoothing filter for the analysis of irregular time series comprising quantitative observations. Low powered RLWR trend lines reveal temporally local phenomena, e.g. abrupt jumps (often associated with point source impacts) and periodicities, while higher powered RLWR yields smooth lines characterizing medium and longer term trends. Simple variants of Tukey smoothing concepts are developed for series with censored observations. Applications to Ontario river quality series reveal that graphical evidence is frequently sufficient to obviate the need for formal trend testing. The methods are generally applicable to most time series.  相似文献   
118.
Information needed for the resolution of environmental problems is a commodity with an economic value. The minimum necessary information implies minimal costs. The formulation of the information is considered for the case of biocides that can disrupt marine ecosystems.  相似文献   
119.
Several recent court decisions add to the growing body of law concerning the responsibility of Government in radiation matters and the quantum of proof needed to show causation between radiation exposures and certain types of cancer and leukemia. The courts have also been addressing a wide range of compensation claims for exposures to toxic chemicals with demonstration of causation being a particularly difficult task. Meanwhile, the Congress has been attempting to legislate a far reaching administrative and judicial framework for compensating toxic victims, including an easing of burden-of-proof requirements for demonstrating causation and a broadening of the basis for admissibility of scientific evidence. Drawing parallels between radiation and toxic exposure problems can be both instructive and misleading. Some of the technical issues are quite similar, including the importance of person-specific exposure estimates and of epidemiological studies. However, the uncertainties associated with toxic exposures are usually far greater, and the scientific data base for relating exposures and effects is much more uncertain.  相似文献   
120.
Research on biological indicators of soil pollution is hampered by soil variability and temporal and spatial fluctuations of numbers of soil animals. These characters on the other hand promote a high biological diversity in the soil. A high diversity combined with persistent soil pollutants increases the chance to select good indicators. However research on these topics is still limited. Examples of specific indicators are the changed arthropod species patterns due to pesticide influence and the changed soil enzyme activity under the influence of specific heavy metals. Another approach is to look for organisms that give a general indication of soil pollution. In this respect the earthworm species Allolobophora caliginosa proved to be sensitive for different types of manure especially pig manure with copper, for sewage sludge, for municipal waste compost and for fly ash. A third way of indication is by organisms accumulating pollutants. For some heavy metals (Cd, Zn), earthworms are very efficient accumulators. More research is needed especially on the specific relation between biological responses and abiotic soil characteristics.  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