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   73277篇
  免费   3007篇
  国内免费   202篇
电工技术   734篇
综合类   646篇
化学工业   10830篇
金属工艺   1180篇
机械仪表   1530篇
建筑科学   1729篇
矿业工程   456篇
能源动力   932篇
轻工业   7336篇
水利工程   878篇
石油天然气   165篇
武器工业   9篇
无线电   2983篇
一般工业技术   8730篇
冶金工业   28188篇
原子能技术   300篇
自动化技术   9860篇
  2023年   475篇
  2022年   407篇
  2021年   811篇
  2020年   671篇
  2019年   788篇
  2018年   1781篇
  2017年   1961篇
  2016年   2352篇
  2015年   1763篇
  2014年   1596篇
  2013年   2927篇
  2012年   3881篇
  2011年   4085篇
  2010年   2052篇
  2009年   1986篇
  2008年   1815篇
  2007年   1763篇
  2006年   1307篇
  2005年   3922篇
  2004年   3110篇
  2003年   2556篇
  2002年   1378篇
  2001年   1127篇
  2000年   642篇
  1999年   1015篇
  1998年   8152篇
  1997年   5161篇
  1996年   3375篇
  1995年   2005篇
  1994年   1487篇
  1993年   1593篇
  1992年   431篇
  1991年   496篇
  1990年   443篇
  1989年   416篇
  1988年   446篇
  1987年   356篇
  1986年   310篇
  1985年   300篇
  1984年   194篇
  1983年   174篇
  1982年   253篇
  1981年   315篇
  1980年   338篇
  1979年   135篇
  1978年   170篇
  1977年   863篇
  1976年   1891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 15 毫秒
51.
52.
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   
53.
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   
54.
55.
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   
56.
57.
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   
58.
59.
60.
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   
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