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   34684篇
  免费   2313篇
  国内免费   30篇
电工技术   254篇
综合类   19篇
化学工业   7285篇
金属工艺   674篇
机械仪表   732篇
建筑科学   963篇
矿业工程   79篇
能源动力   607篇
轻工业   5799篇
水利工程   324篇
石油天然气   126篇
武器工业   5篇
无线电   1304篇
一般工业技术   5985篇
冶金工业   8025篇
原子能技术   124篇
自动化技术   4722篇
  2024年   64篇
  2023年   311篇
  2022年   367篇
  2021年   944篇
  2020年   726篇
  2019年   826篇
  2018年   1444篇
  2017年   1377篇
  2016年   1444篇
  2015年   1128篇
  2014年   1340篇
  2013年   2820篇
  2012年   2025篇
  2011年   1845篇
  2010年   1544篇
  2009年   1385篇
  2008年   1345篇
  2007年   1224篇
  2006年   846篇
  2005年   723篇
  2004年   677篇
  2003年   588篇
  2002年   589篇
  2001年   430篇
  2000年   399篇
  1999年   443篇
  1998年   2378篇
  1997年   1621篇
  1996年   1045篇
  1995年   624篇
  1994年   472篇
  1993年   567篇
  1992年   210篇
  1991年   214篇
  1990年   155篇
  1989年   161篇
  1988年   165篇
  1987年   140篇
  1986年   127篇
  1985年   146篇
  1984年   132篇
  1983年   107篇
  1982年   134篇
  1981年   157篇
  1980年   159篇
  1979年   83篇
  1978年   85篇
  1977年   281篇
  1976年   626篇
  1973年   66篇
排序方式: 共有10000条查询结果,搜索用时 359 毫秒
51.
A novel glass-ceramic material based on albite type Na-rich feldspar has been synthesized by conventional ceramic process. High crystallinity, >94%?Vol.% is obtained by fast sintering which allows energy saving processing. Albite is the main crystalline phase and tetragonal SiO2 is a secondary phase. Electrical properties were examined by complex impedance, DC measurements, and dielectric breakdown test. Dielectric characterization shows a non-Debye type dielectric behavior with low dielectric constant, 4.6 at 1?MHz, low dielectric losses, (~10?3 at 1?MHz, and a large dielectric strength, ~60?kV/mm), that it is the largest value reported in ceramic insulators. Those dielectric properties are attained by the low glassy phase content in the samples and their unique micro-nanostructure. All these properties make this novel material a very promising candidate in the market of ceramic electrical insulator, highlighting for high-voltage applications.  相似文献   
52.
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   
53.
54.
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   
55.
56.
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   
57.
58.
59.
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   
60.
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