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   73031篇
  免费   3006篇
  国内免费   205篇
电工技术   740篇
综合类   647篇
化学工业   10704篇
金属工艺   1170篇
机械仪表   1522篇
建筑科学   1719篇
矿业工程   458篇
能源动力   930篇
轻工业   7284篇
水利工程   879篇
石油天然气   162篇
武器工业   9篇
无线电   2982篇
一般工业技术   8719篇
冶金工业   28184篇
原子能技术   299篇
自动化技术   9834篇
  2023年   473篇
  2022年   403篇
  2021年   822篇
  2020年   663篇
  2019年   782篇
  2018年   1772篇
  2017年   1954篇
  2016年   2347篇
  2015年   1758篇
  2014年   1585篇
  2013年   2914篇
  2012年   3874篇
  2011年   4067篇
  2010年   2038篇
  2009年   1979篇
  2008年   1800篇
  2007年   1750篇
  2006年   1300篇
  2005年   3914篇
  2004年   3104篇
  2003年   2548篇
  2002年   1369篇
  2001年   1123篇
  2000年   640篇
  1999年   1010篇
  1998年   8147篇
  1997年   5156篇
  1996年   3372篇
  1995年   2001篇
  1994年   1483篇
  1993年   1593篇
  1992年   430篇
  1991年   494篇
  1990年   442篇
  1989年   415篇
  1988年   442篇
  1987年   351篇
  1986年   307篇
  1985年   299篇
  1984年   190篇
  1983年   170篇
  1982年   247篇
  1981年   314篇
  1980年   337篇
  1979年   134篇
  1978年   170篇
  1977年   863篇
  1976年   1889篇
  1975年   143篇
  1973年   107篇
排序方式: 共有10000条查询结果,搜索用时 187 毫秒
51.
The Journal of Supercomputing - Deadlock-free dynamic network reconfiguration process is usually studied from the routing algorithm restrictions and resource reservation perspective. The dynamic...  相似文献   
52.
53.
Abstract

In this work, a new g-C3N4-based Z-scheme with γ-Fe2O3 and β-Ag2Se both n-type semiconductors, and graphite to favor electron exchange is presented. The composite material was studied by XRD, FTIR, UV-Vis, TEM, XPS, TGA, DSC and TOF-SIMS, and the ability of this photocatalytic system to act as a photo-reductant was assessed using crystal violet (CV+) dye. Solar light driven photo-reduction of CV+ in the presence of tri-sodium citrate evidenced a synergistic enhancement of the activity of the composite toward reduction, with ~20 times higher conversion rates per unit of surface area than those of g-C3N4. Photo-oxidation experiments under Xe lamp irradiation in the presence of H2O2 also showed that the AgFeCN composite featured a higher activity (~8×) than g-C3N4. This Z-scheme may deserve further study as a photo-reductant to obtain hydrogen or hydrogenated compounds. Moreover, the use of CV+ may represent a facile procedure that can aid in the selection of new photocatalysts to be used in hydrogen production.  相似文献   
54.
55.
Personal and Ubiquitous Computing - This article presents a study concerning the evaluation of a smart home control system for elderly people with a sample of 10 users in a city in the interior of...  相似文献   
56.
57.
58.
The fission yeast Schizosaccharomyces pombe is an important model organism for the study of fundamental questions in eukaryotic cell and molecular biology. A plethora of cellular processes are membrane associated and/or dependent on the proper functioning of cellular membranes. Phospholipids are not only the basic building blocks of cellular membranes; they also serve as precursors to numerous signaling molecules. In this review, we describe the biosynthetic pathways leading to major S. pombe phospholipids, how these pathways are regulated, and what is known about degradation and turnover of fission yeast phospholipids. This review also addresses the synthesis, regulation and the role of water-soluble phospholipid precursors. The last chapter of the review is devoted to the use of S. pombe for the biotechnological production of value-added lipid molecules.  相似文献   
59.
60.
Lipases are hydrolytic enzymes that break the ester bonds of triglycerides, generating free fatty acids and glycerol. Extracellular lipase activity has been reported for the nonconventional yeast Kluyveromyces marxianus, grown in olive oil as a substrate, and the presence of at least eight putative lipases has been detected in its genome. However, to date, there is no experimental evidence on the physiological role of the putative lipases nor their structural and catalytic properties. In this study, a bioinformatic analysis of the genes of the putative lipases from K. marxianus L-2029 was performed, particularly identifying and characterizing the extracellular expected enzymes, due to their biotechnological relevance. The amino acid sequence of 10 putative lipases, obtained by in silico translation, ranged between 389 and 773 amino acids. Two of the analysed putative proteins showed a signal peptide, 25 and 33 amino acids long for KmYJR107Wp and KmLIP3p, and a molecular weight of 44.53 and 58.23 kDa, respectively. The amino acid alignment of KmLIP3p and KmYJR107Wp with the crystallized lipases from a patatin and the YlLip2 lipase from Yarrowia lipolytica, respectively, revealed the presence of the hydrolase characteristic motifs. From the 3D models of putative extracellular K. marxianus L-2029 lipases, the conserved pentapeptide of each was determined, being GTSMG for KmLIP3p and GHSLG for KmYJR107Wp; besides, the genes of these two enzymes (LIP3 and YJR107W) are apparently regulated by oleate response elements. The phylogenetic analysis of all K. marxianus lipases revealed evolutionary affinities with lipases from abH15.03, abH23.01, and abH23.02 families.  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