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   403875篇
  免费   4680篇
  国内免费   1367篇
电工技术   7565篇
综合类   317篇
化学工业   59868篇
金属工艺   16428篇
机械仪表   13491篇
建筑科学   8350篇
矿业工程   2157篇
能源动力   11543篇
轻工业   28452篇
水利工程   4268篇
石油天然气   7915篇
武器工业   17篇
无线电   49249篇
一般工业技术   83043篇
冶金工业   74963篇
原子能技术   9182篇
自动化技术   33114篇
  2022年   2566篇
  2021年   3897篇
  2020年   2948篇
  2019年   3805篇
  2018年   6485篇
  2017年   6477篇
  2016年   6930篇
  2015年   4319篇
  2014年   7150篇
  2013年   20049篇
  2012年   11417篇
  2011年   15276篇
  2010年   12147篇
  2009年   13717篇
  2008年   14061篇
  2007年   13822篇
  2006年   12421篇
  2005年   11119篇
  2004年   10507篇
  2003年   10419篇
  2002年   9827篇
  2001年   9735篇
  2000年   9135篇
  1999年   9520篇
  1998年   24325篇
  1997年   16708篇
  1996年   12797篇
  1995年   9517篇
  1994年   8362篇
  1993年   8379篇
  1992年   6054篇
  1991年   5694篇
  1990年   5679篇
  1989年   5318篇
  1988年   5044篇
  1987年   4419篇
  1986年   4299篇
  1985年   4812篇
  1984年   4421篇
  1983年   3994篇
  1982年   3654篇
  1981年   3730篇
  1980年   3429篇
  1979年   3326篇
  1978年   3334篇
  1977年   3750篇
  1976年   4847篇
  1975年   2850篇
  1974年   2663篇
  1973年   2730篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
131.
132.
133.
Some of the factors affecting cloud point determination of palm oleins are described. These are the type of container used, method of stirring, rate of stirring and bath temperature. The repeatability and reproducibility standard deviations of the method are determined from collaborative trials. Recommendations for the test are made to reduce the large variations among laboratories.  相似文献   
134.
135.
The impact of fouling on the operation of submerged membrane bioreactors (MBRs) is discussed. The discussion proceeds through a review of the impacts of fouling and fouling speciation, with correlations of filterability against candidate foulants being provided. There follows a brief comparison of hydraulic performance of the submerged and sidestream configurations: data is presented to demonstrate the efficacy of coarse bubble aeration in the submerged MBR. The critical flux concept is then discussed and its applicability to MBRs deliberated in view of recent publications demonstrating fouling under sub-critical flux conditions. Finally, the two most commercially important MBR products are briefly reviewed with specific reference to design and operation for fouling amelioration.  相似文献   
136.
137.
The biological decolorization of two industrial, spent textile reactive dyebaths was investigated using a suspended-growth, halophilic mixed culture fed with glucose. Dyebath I contained mainly Reactive Blue 19 (RB19), an anthraquinone dye, whereas dyebath II contained mainly Reactive Blue 21 (RB21), a phthalocyanine dye. Batch assays under anaerobic conditions with the two neutralized dyebaths resulted in 87 and 37% extent of decolorization for dyebaths I and II, respectively. The rate of glucose utilization and the extent of acetate production were impacted in the presence of each dyebath as compared to the control culture. However, dyebath decolorization occurred despite moderate culture inhibition. Reuse of a biologically renovated RB19-containing dyebath in the dyeing process resulted in reproducible but not identical cotton fabric shades as compared to a standard dyeing (i.e., control) using fresh water. This difference is attributed to a variable degree of RB19 aggregation during the dyeing process and is not related to the efficiency of the biodecolorization process. Further improvement of the redyeing efficiency will lead to the development of an in-plant, closed-loop decolorization system resulting in significant water conservation and minimization of textile pollutants such as salt and dyes.  相似文献   
138.
Ozone measurement based on the optical absorption of visible light at 603 nm using polymer optical fibres is investigated and tested. Comparisons with a commercial UV based sensor demonstrate the ability of the visible based sensor to measure high concentrations over a range 27-127 mg/litre. A resolution of 5 mg/litre is also demonstrated for this sensor.  相似文献   
139.
This paper is concerned with the use of optical-fiber and optoelectronic technology for the implementation of local area networks. For the purposes of this paper, we define a local area network as an information transport system which provides connectivity amongst distributed communicating entities within a structure (room, building); within a campus or an office complex; or within a geographical area about the size of a United States local access and transport area (LATA). This paper focuses on the subject of network protocols; i.e., how do we implement the orderly sharing of network resources.  相似文献   
140.
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