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   15577篇
  免费   138篇
  国内免费   101篇
安全科学   375篇
废物处理   683篇
环保管理   1868篇
综合类   2711篇
基础理论   3874篇
环境理论   11篇
污染及防治   4274篇
评价与监测   1085篇
社会与环境   842篇
灾害及防治   93篇
  2023年   100篇
  2022年   218篇
  2021年   209篇
  2020年   124篇
  2019年   140篇
  2018年   302篇
  2017年   236篇
  2016年   411篇
  2015年   289篇
  2014年   473篇
  2013年   1252篇
  2012年   588篇
  2011年   720篇
  2010年   587篇
  2009年   604篇
  2008年   739篇
  2007年   732篇
  2006年   645篇
  2005年   544篇
  2004年   456篇
  2003年   467篇
  2002年   432篇
  2001年   524篇
  2000年   387篇
  1999年   235篇
  1998年   144篇
  1997年   168篇
  1996年   170篇
  1995年   212篇
  1994年   206篇
  1993年   167篇
  1992年   139篇
  1991年   175篇
  1990年   171篇
  1989年   164篇
  1988年   119篇
  1987年   119篇
  1986年   121篇
  1985年   97篇
  1984年   108篇
  1983年   112篇
  1982年   122篇
  1981年   108篇
  1980年   98篇
  1979年   115篇
  1978年   73篇
  1977年   78篇
  1975年   81篇
  1973年   72篇
  1967年   73篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
101.
The paper focuses upon the organization of a federal state-funded pollution prevention project in the Styrian industry. The project includes 13 companies from the textile, pulp and paper, machine building, wood working and printed circuit board manufacturing industries, covering most of the sectors and sizes in the Styrian industry. It started in January 1994 and will last for one year. It will demonstrate the possibilities of pollution prevention and the need for further research work. This project will make use of the methods and tools that were refined in the Austrian Prepare project. As a first step, a systematic balance of all the inputs and outputs of a company is made, after which the weak points and inefficiencies of material and energy use are identified and the options for improvements, both economical and ecological, are defined. Consequently, modifications in products and production lead to a situation with less waste and emissions. The preliminary lessons from these projects are presented: as a rule, the utilities (consumption of process materials and water, cleaning, energy, preparatory and finishing steps) are treated as black boxes and usually represent a considerable optimization potential. In these areas especially there is usually a lack of information and coordination as well as a need for a systematic and comprehensive approach. Leadership in the company and creative consultants are needed for starting lasting successful pollution prevention projects.  相似文献   
102.
Forchhammer  K.  Böck  A. 《Die Naturwissenschaften》1991,78(11):497-504
The importance of selenium as an essential trace element has progressively emerged during the last years due to the analysis of selenium deficiency diseases and to the identification and characterization of a number of selenoenzymes. Selenium is incorporated in the catalytic site of the enzymes as an integral selenocysteine residue. The pathway of selenocysteine biosynthesis and incorporation has been elucidated recently for Escherichia coli. This article presents an overview on these subjects and describes the mechanisms which confer selenocysteine specificity in the framework of protein biosynthesis. In addition, some considerations concerning the phylogeny of selenocysteine incorporation are presented and a model for the evolution of the selenocysteine pathway is proposed.  相似文献   
103.
104.
105.
106.
107.
108.
109.
110.
Forty-two open neural tube defects (NTDs) were identified in our series of 7440 amniocenteses tested between 11 and 15 weeks of gestation. Using a cut-off of ≥2.0 MOM, the detection rate for open NTDs was 95 per cent; 100 per cent each for anencephaly and spina bifida; and 78 per cent for encephalocele. Two encephaloceles had AFP levels less than 2.0 MOM and negative AChEs. Thirty-four (81 per cent) of these NTDs were tested between 13 and 15 weeks and 8 (19 per cent) before 13 weeks. There were 0.6 per cent false positives by AFP (excluding serious abnormalities and fetal death) and 0.1 per cent after AChE. The likelihood of an open NTD after an elevated AFP (≥2.0 MOM) was 24 and 77 per cent for any serious abnormality. These results, when combined with an earlier study, indicate that amniotic fluid AFP appears to be as sensitive a test for open NTDs between 13 and 15 weeks as between 16 and 20 weeks. Additional experience is necessary to determine this before 13 weeks.  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