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   31389篇
  免费   622篇
  国内免费   237篇
安全科学   921篇
废物处理   1129篇
环保管理   4268篇
综合类   5621篇
基础理论   8839篇
环境理论   22篇
污染及防治   8140篇
评价与监测   1791篇
社会与环境   1291篇
灾害及防治   226篇
  2023年   179篇
  2022年   284篇
  2021年   290篇
  2020年   249篇
  2019年   305篇
  2018年   435篇
  2017年   450篇
  2016年   628篇
  2015年   597篇
  2014年   798篇
  2013年   2284篇
  2012年   955篇
  2011年   1369篇
  2010年   1115篇
  2009年   1104篇
  2008年   1345篇
  2007年   1394篇
  2006年   1247篇
  2005年   1053篇
  2004年   1044篇
  2003年   979篇
  2002年   970篇
  2001年   1278篇
  2000年   902篇
  1999年   583篇
  1998年   459篇
  1997年   465篇
  1996年   471篇
  1995年   508篇
  1994年   457篇
  1993年   420篇
  1992年   427篇
  1991年   382篇
  1990年   390篇
  1989年   413篇
  1988年   347篇
  1987年   300篇
  1986年   277篇
  1985年   307篇
  1984年   286篇
  1983年   322篇
  1982年   322篇
  1981年   271篇
  1980年   244篇
  1979年   269篇
  1978年   229篇
  1977年   195篇
  1976年   200篇
  1975年   192篇
  1972年   198篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
191.
    
There is an increased interest in merging observations from local networks into larger national and international databases. However, the observations from different networks have typically been made using different equipment and applying different post‐processing of the values. These heterogeneities in recorded values between networks can lead to inconsistencies between different networks, and to discontinuities at the borders between regions if the observations are used as a source for interpolated maps of the process. Such discontinuities are undesirable, and could create difficulties in interpreting the maps by decision makers. In this paper, we present two variants of a method that can be used to identify and quantify differences between networks. The first variant deals with networks sharing the same region (usually multiple networks within a country) while the second variant deals with networks in neighbouring regions (usually networks in different countries). The estimated differences can be used to estimate individual biases for each network, which can be subtracted as a harmonization procedure. The method was applied to European gamma dose rate (GDR) measurements from May 2008 from the European Radiological Data Exchange Platform (EURDEP) database. Data from the Slovenian GDR network are used for an application of the first variant of the method whereas the complete dataset is used to illustrate the second variant. The results indicate that these two variants are able to identify and quantify biases reliably, and the interpolated maps after subtraction of the estimated biases appear more reliable than maps created on the basis of the recorded data. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   
192.
    
Some recent research on the properties of the probability density function for the concentration of a scalar dispersing in turbulent flow is summarized. It is concluded that the beta distribution may be a simple model consistent with these properties. This proposal is verified theoretically, and some preliminary data comparisons are very promising.  相似文献   
193.
    
The United States Environmental Protection Agency (EPA), in its recent risk assessment dealing with environmental tobacco smoke (ETS), estimated the annual number of lung cancer deaths in non-smokers (including both never-smokers and former-smokers who have quit smoking for at least five years) associated with ETS exposure to be between 2500 and 3300 in the United States. This estimate is based on a number of assumptions that are not supported by the existing data. Moreover, the range presented by EPA fails to take into account the uncertainties involved in this estimate. This paper discusses the significant assumptions that underlie any quantitation of lung cancer risks allegedly due to ETS exposure, and explores the uncertainties of each assumption and how each uncertainty affects the summary estimate. The author concludes that any range must encompass an estimate of zero deaths, and that the uncertainties are so great as to cast serious doubt on the use of any quantitative estimate.  相似文献   
194.
    
  相似文献   
195.
    
  相似文献   
196.
    
Calcium looping technology is a promising new technique for high‐temperature scrubbing of CO2 from flue gas and syngases. Current economic projections suggest it might be able to capture CO2 at costs of ∼$20/ton of avoided CO2. Nonetheless there are questions about the long‐term behavior of natural sorbents in such systems, and there is substantial R&D being done on this technology worldwide to answer questions about whether the performance of natural sorbents can be improved, or whether it would be better to use synthetic ones. The current period is particularly interesting as the first pilot plants and demonstration units capable of operating continuously are now coming on stream, and if successful these will lead to large‐scale industrial demonstrations of the technology in the next 10 to 15 years. © 2011 Society of Chemical Industry and John Wiley & Sons, Ltd  相似文献   
197.
Verhaltensversuche zur Funktion der Lorenzinischen Ampullen   总被引:1,自引:0,他引:1  
  相似文献   
198.
199.
    
  相似文献   
200.
Mine-drainage treatment wetland as habitat for herptofaunal wildlife   总被引:1,自引:0,他引:1  
Land reclamation techniques that incorporate habitat features for herptofaunal wildlife have received little attention. We assessed the suitability of a wetland, constructed for the treatment of mine-water drainage, for supporting herptofaunal wildlife from 1988 through 1990 using diurnal and nocturnal surveys. Natural wetlands within the surrounding watershed were also monitored for comparison. The treatment wetland supported the greatest abundance and species richness of herptofauna among the sites surveyed. Abundance was a function of the frog density, particularly green frogs (Rana clamitans) and pickerel frogs (R. palustris), while species richness was due to the number of snake species found. The rich mix of snake species present at the treatment wetland was believed due to a combination of an abundant frog prey base and an amply supply of den sites in rock debris left behind from earlier surface-mining activities. Nocturnal surveys of breeding male frogs demonstrated highest breeding activity at the treatment wetland, particularly for spring peepers (Hyla crucifer). Whole-body assays of green frog and bullfrog (R. catesbeiana) tissues showed no differences among sites in uptake of iron, aluminum, and zinc; managanese levels in samples from the treatment wetland were significantly lower than those from natural wetlands. These results suggest that wetlands established for water quality improvement can provide habitat for reptiles and amphibians, with the species composition dependent on the construction design, the proximity to source populations, and the degree of acidity and heavy-metal concentrations in drainage waters.  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