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   3462篇
  免费   19篇
  国内免费   41篇
安全科学   85篇
废物处理   171篇
环保管理   392篇
综合类   475篇
基础理论   1244篇
环境理论   1篇
污染及防治   691篇
评价与监测   226篇
社会与环境   220篇
灾害及防治   17篇
  2023年   12篇
  2022年   10篇
  2021年   21篇
  2020年   23篇
  2019年   13篇
  2018年   143篇
  2017年   134篇
  2016年   203篇
  2015年   71篇
  2014年   24篇
  2013年   71篇
  2012年   449篇
  2011年   247篇
  2010年   51篇
  2009年   62篇
  2008年   68篇
  2007年   89篇
  2006年   88篇
  2005年   413篇
  2004年   539篇
  2003年   421篇
  2002年   71篇
  2001年   44篇
  2000年   22篇
  1999年   39篇
  1998年   7篇
  1997年   15篇
  1996年   8篇
  1995年   17篇
  1994年   7篇
  1993年   6篇
  1992年   10篇
  1991年   10篇
  1990年   11篇
  1989年   15篇
  1988年   6篇
  1987年   3篇
  1986年   10篇
  1985年   5篇
  1984年   3篇
  1983年   4篇
  1982年   4篇
  1981年   4篇
  1980年   4篇
  1979年   3篇
  1975年   3篇
  1972年   4篇
  1966年   4篇
  1957年   2篇
  1931年   2篇
排序方式: 共有3522条查询结果,搜索用时 31 毫秒
941.
In this study, the prevalence of different enteric viruses in commercial mussels was evaluated at the retail level in three European countries (Finland, Greece and Spain). A total of 153 mussel samples from different origins were analysed for human norovirus (NoV) genogroups I and II, hepatitis A virus (HAV) and hepatitis E virus (HEV). Human adenovirus (HAdV) was also tested as an indicator of human faecal contamination. A full set of controls (such as sample process control, internal amplification controls, and positive and negative controls) were implemented during the process. The use of a sample process control allowed us to calculate the efficiencies of extraction, which ranged from 79 to 0.5?%, with an average value of 10?%. Samples were positive in 41?% of cases, with HAdV being the most prevalent virus detected (36?%), but no significant correlation was found between the presence of HAdV and human NoV, HAV and HEV. The prevalences of human norovirus genogroup II, HEV and human NoV genogroup I were 16, 3 and 0.7?%, respectively, and HAV was not detected. The estimated number of PCR detectable units varied between 24 and 1.4?×?103?g?1 of digestive tract. Interestingly, there appeared to be a significant association between the type of mussel species (M. galloprovincialis) and the positive result of samples, although a complete overlap between country and species examined required this finding to be confirmed including samples of both species from all possible countries of origin.  相似文献   
942.
943.
Regional Environmental Change - Plausible scenarios of future land use derived from model projections may differ substantially from what is actually desired by society, and identifying such...  相似文献   
944.
945.
Degradation of biochanin A, 400 μg (1.41 μmol) per gram of dry soil, was studied and the initial degradation products, dihydrobiochanin A, pratensein and genistein were identified and quantified. The maximum concentrations of these compounds were determined as 166 pmol/g dry soil after 2 days of incubation, 175 pmol/g dry soil after 1 day and 1,236 pmol/g dry soil after 1 day, respectively. Biochanin A and the initially formed products degrade too fast to be responsible for clover soil sickness (DT90 <20 days), but could be precursors for the responsible compounds. The immediate degradation products from biochanin A are all biologically active and are the prime candidates for a reduction of weed pressure caused by clover.  相似文献   
946.
947.
Darwinian studies of collective human behaviour, which deal fluently with change and are grounded in the details of social influence among individuals, have much to offer “social” models from the physical sciences which have elegant statistical regularities. Although Darwinian evolution is often associated with selection and adaptation, “neutral” models of drift are equally relevant. Building on established neutral models, we present a general, yet highly parsimonious, stochastic model, which generates an entire family of real-world, right-skew socio-economic distributions, including exponential, winner-take-all, power law tails of varying exponents, and power laws across the whole data. The widely used Barabási and Albert (1999) Science 286: 509-512 “B-A” model of preferential attachment is a special case of this general model. In addition, the model produces the continuous turnover observed empirically within these distributions. Previous preferential attachment models have generated specific distributions with turnover using arbitrary add-on rules, but turnover is an inherent feature of our model. The model also replicates an intriguing new relationship, observed across a range of empirical studies, between the power law exponent and the proportion of data represented in the distribution.  相似文献   
948.
949.
950.
Known conceptual and technical limitations of mainstream environmental health data analysis have directed research to new avenues. The goal is to deal more efficiently with the inherent uncertainty and composite space-time heterogeneity of key attributes, account for multi-sourced knowledge bases (health models, survey data, empirical relationships etc.), and generate more accurate predictions across space-time. Based on a versatile, knowledge synthesis methodological framework, we introduce new space-time covariance functions built by integrating epidemic propagation models and we apply them in the analysis of existing flu datasets. Within the knowledge synthesis framework, the Bayesian maximum entropy theory is our method of choice for the spatiotemporal prediction of the ratio of new infectives (RNI) for a case study of flu in France. The space-time analysis is based on observations during a period of 15 weeks in 1998–1999. We present general features of the proposed covariance functions, and use these functions to explore the composite space-time RNI dependency. We then implement the findings to generate sufficiently detailed and informative maps of the RNI patterns across space and time. The predicted distributions of RNI suggest substantive relationships in accordance with the typical physiographic and climatologic features of the country.  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