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   3172篇
  免费   30篇
  国内免费   1篇
电工技术   83篇
化学工业   342篇
金属工艺   1564篇
机械仪表   28篇
建筑科学   15篇
矿业工程   1篇
能源动力   51篇
轻工业   65篇
水利工程   2篇
石油天然气   1篇
无线电   259篇
一般工业技术   248篇
冶金工业   422篇
原子能技术   39篇
自动化技术   83篇
  2023年   7篇
  2022年   16篇
  2021年   14篇
  2020年   12篇
  2019年   9篇
  2018年   13篇
  2017年   12篇
  2016年   30篇
  2015年   10篇
  2014年   37篇
  2013年   100篇
  2012年   87篇
  2011年   83篇
  2010年   52篇
  2009年   92篇
  2008年   111篇
  2007年   99篇
  2006年   90篇
  2005年   75篇
  2004年   66篇
  2003年   101篇
  2002年   121篇
  2001年   121篇
  2000年   96篇
  1999年   121篇
  1998年   241篇
  1997年   207篇
  1996年   157篇
  1995年   99篇
  1994年   101篇
  1993年   158篇
  1992年   151篇
  1991年   135篇
  1990年   50篇
  1989年   37篇
  1988年   30篇
  1987年   29篇
  1986年   35篇
  1985年   32篇
  1984年   40篇
  1983年   23篇
  1982年   14篇
  1981年   16篇
  1980年   13篇
  1979年   15篇
  1978年   9篇
  1977年   4篇
  1976年   15篇
  1974年   4篇
  1973年   5篇
排序方式: 共有3203条查询结果,搜索用时 15 毫秒
11.
In order to produce highly concentrated bioethanol by pervaporation using an ethanol‐permselective silicalite membrane, techniques to suppress adsorption of succinic acid, which is a chief by‐product of ethanol fermentation and causes the deterioration in pervaporation performance, onto the silicalite crystals was investigated. The amount adsorbed increased as the pH of the aqueous succinic acid solution decreased. The pervaporation performance also decreased with decreasing pH when the ternary mixtures of ethanol/water/succinic acid were separated. Using silicalite membranes individually coated with two types of silicone rubber, pervaporation performance was significantly improved in the pH range of 5 to 7, when compared with that of non‐coated silicalite membranes in ternary mixtures of ethanol/water/succinic acid. Moreover, when using a silicalite membrane double‐coated with the two types of silicone rubber, pervaporation performance was stabilized at lower pH values. In the separation of bioethanol by pervaporation using the double‐coated silicalite membrane, removal of accumulated substances having an ultraviolet absorption maximum at approximately 260 nm from the fermentation broth proved to be vital for efficient pervaporation. Copyright © 2005 Society of Chemical Industry  相似文献   
12.
13.
14.
15.
The recent increase in the demand for power in urban areas has caused changes in the way power is supplied. Underground distribution systems have been introduced for convenience in urban areas and to prevent injuries in case of a crisis. As a result, many new types of power cables are being used. One type, XPLE cables (also called CV cables) have been rapidly taking the place of conventional cables such as OF or SL cables since the 1960s because of their relatively easy installation and maintainability. However, distribution cables used under severe environmental conditions deteriorate rapidly (due mainly to water treeing), and some cables experience insulation breakdown. Therefore, many diagnostic methods have been developed, though they have not been very effective. By combining methods, a high reliability can be achieved in comparison to the use of a single method. However, processing the data is difficult for on-site personnel, so many experts are required. But there is a lack of qualified experts, hence we have turned to the development of expert systems.  相似文献   
16.
APP is a transmembrane precursor of beta-amyloid. In dominantly inherited familial Alzheimer's disease (FAD), point mutations V6421, V642F and V642G have been discovered in APP695. Here we show that expression of these mutants (FAD-APPs) causes a clone of COS cells to undergo apoptosis associated with DNA fragmentation. Apoptosis by the three FAD-APPs was the highest among all possible V642 mutants; normal APP695 had no effect on apoptosis, suggesting that apoptosis by APP mutants in this system is phenotypically linked to the FAD trait. FAD-APP-induced apoptosis was sensitive to bcl-2 and most probably mediated by heteromeric G proteins. This study presents a model system allowing analysis of the mechanism for FAD-APP-induced cytotoxicity.  相似文献   
17.
18.
19.
20.
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