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   6676篇
  免费   45篇
  国内免费   44篇
安全科学   175篇
废物处理   332篇
环保管理   777篇
综合类   940篇
基础理论   1641篇
环境理论   1篇
污染及防治   1657篇
评价与监测   458篇
社会与环境   749篇
灾害及防治   35篇
  2023年   47篇
  2022年   80篇
  2021年   67篇
  2020年   38篇
  2019年   53篇
  2018年   89篇
  2017年   102篇
  2016年   147篇
  2015年   94篇
  2014年   178篇
  2013年   556篇
  2012年   210篇
  2011年   280篇
  2010年   240篇
  2009年   260篇
  2008年   307篇
  2007年   305篇
  2006年   277篇
  2005年   246篇
  2004年   242篇
  2003年   263篇
  2002年   216篇
  2001年   292篇
  2000年   188篇
  1999年   120篇
  1998年   66篇
  1997年   69篇
  1996年   67篇
  1995年   70篇
  1994年   85篇
  1993年   74篇
  1992年   77篇
  1991年   77篇
  1990年   81篇
  1989年   68篇
  1988年   71篇
  1987年   64篇
  1986年   72篇
  1985年   57篇
  1984年   64篇
  1983年   71篇
  1982年   65篇
  1981年   40篇
  1980年   54篇
  1979年   44篇
  1978年   39篇
  1977年   36篇
  1976年   35篇
  1974年   33篇
  1973年   33篇
排序方式: 共有6765条查询结果,搜索用时 531 毫秒
681.
682.
683.
It is common practice to use the second highest value both in determining compliance with the once-per-year air quality standards (AQS) and as a measure of air quality in pollutant trend studies and rollback calculations. A study of the variation in the second highest 8 hr carbon monoxide concentration observed at the CAMP stations 1962-72 is presented. It is shown that, for a given annual average, the second highest value can differ by a factor of 2 due to random variation. The annual average is linearly related to the observed average of the second highest value and is shown to be a good predictor of the percent of time the carbon monoxide AQS is exceeded. It is concluded that the annual average, which is less variable and not as greatly influenced by erroneous measurements, is the preferred measure of air quality for trend studies and air quality projections.  相似文献   
684.
A study is presented on the distribution of 234U, 238U, 235U isotopes in surface water of the Llobregat river basin (Northeast Spain), from 2001 to 2006. Sixty-six superficial water samples were collected at 16 points distributed throughout the Llobregat river basin. Uranium isotopes were measured by alpha spectrometry (PIPS detectors). The test procedure was validated according to the quality requirements of the ISO17025 standard. The activity concentration for the total dissolved uranium ranges from 20 to 261 mBq L−1. The highest concentrations of uranium were detected in an area with formations of sedimentary rock, limestone and lignite. A high degree of radioactive disequilibrium was noted among the uranium isotopes. The 234U/238U activity ratio varied between 1.1 and 1.9 and the waters with the lowest uranium activity registered the highest level of 234U/238U activity ratio. Correlations between uranium activity in the tested water and chemical and physical characteristics of the aquifer were found.  相似文献   
685.
686.
Non-invasive prenatal screening (NIPS) has revolutionized the approach to prenatal fetal aneuploidy screening. Many commercial providers now offer analyses for sub-chromosomal copy number variations (CNVs). Here, we review the use of NIPS in the context of screening for microdeletions and microduplications, issues surrounding the choice of disorders tested for, and the advantages and disadvantages associated with the inclusion of microdeletions to current NIPS. Several studies have claimed benefits; however, we suggest that microdeletions have not demonstrated a low enough false positive rate to be deemed practical or ethically acceptable, especially considering their low positive predictive values. Because a positive NIPS result should be confirmed using diagnostic techniques, and false positive rates are as high as 90% for some microdeletions, diagnostic testing seems preferable when the goal is to maximize the detection of microdeletion or microduplication syndromes.  相似文献   
687.
I. Lewis  S. Newnam 《Safety Science》2011,49(10):1321-1330
This paper details the development of, and perceived role and effectiveness of an innovative intervention designed to ultimately improve the safety of a group of community care (CC) nurses while driving. Recruiting participants from an Australian CC nursing car fleet, qualitative responses from a series of open-ended questions were obtained from drivers (n = 36), supervisors (n = 22), and managers (n = 6). The findings supported the effectiveness of the intervention in reducing self-reported speeding and promoting greater insight into one’s behaviour on the road. This research has important practical implications in that it highlights the value of developing an intervention based on a sound theoretical framework and which is aligned with the needs and beliefs of personnel within a particular organisation.  相似文献   
688.
Evaluation of sustainability in various facets of life is gaining increasing importance. Traditionally, different multi-criteria decision-making methods have been used for sustainability assessment. “Sustainability” can be a qualitative concept, and as such several researchers have attempted fuzzy logic for the quantitative assessment of sustainability. This paper outlines a new evaluation model based on fuzzy multi-criteria decision-making. The model is tested for sustainability assessment of higher education institutions (HEIs). It is based on a driving force–pressure–state–exposure–effect–action (DPSEEA) framework and is called uncertainty-based DPSEEA-Sustainability index Model (uD-SiM). The uD-SiM is a causality-based model in which the sustainability index is an outcome of nonlinear impacts of sustainability indicators in different stages of DPSEEA. The percent contribution of driving forces on the sustainability index of HEI is investigated using sensitivity analysis. The study reveals that education in sustainability and global and local research trends are the major driving forces for achieving sustainability in HEI, followed by financial and economic growth rate, social equity, energy requirements rate, and institutional enhancement, in descending order. The results of uD-SiM were found to be more realistic and rational than our earlier proposed approach, D-SiM.  相似文献   
689.
690.
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