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   109482篇
  免费   8537篇
  国内免费   2997篇
电工技术   4213篇
技术理论   10篇
综合类   4538篇
化学工业   21114篇
金属工艺   4323篇
机械仪表   4750篇
建筑科学   6759篇
矿业工程   1894篇
能源动力   3028篇
轻工业   12749篇
水利工程   1717篇
石油天然气   3827篇
武器工业   527篇
无线电   10052篇
一般工业技术   15110篇
冶金工业   10226篇
原子能技术   902篇
自动化技术   15277篇
  2024年   376篇
  2023年   1542篇
  2022年   2962篇
  2021年   4178篇
  2020年   3219篇
  2019年   2867篇
  2018年   3789篇
  2017年   3787篇
  2016年   3799篇
  2015年   3973篇
  2014年   4995篇
  2013年   7130篇
  2012年   6900篇
  2011年   7381篇
  2010年   5912篇
  2009年   5615篇
  2008年   5538篇
  2007年   5130篇
  2006年   4527篇
  2005年   3888篇
  2004年   3030篇
  2003年   2744篇
  2002年   2488篇
  2001年   2108篇
  2000年   2180篇
  1999年   2506篇
  1998年   4104篇
  1997年   2933篇
  1996年   2375篇
  1995年   1716篇
  1994年   1438篇
  1993年   1142篇
  1992年   690篇
  1991年   540篇
  1990年   456篇
  1989年   423篇
  1988年   348篇
  1987年   265篇
  1986年   215篇
  1985年   200篇
  1984年   157篇
  1983年   117篇
  1982年   137篇
  1981年   141篇
  1980年   135篇
  1979年   67篇
  1978年   75篇
  1977年   154篇
  1976年   281篇
  1973年   70篇
排序方式: 共有10000条查询结果,搜索用时 500 毫秒
101.
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   
102.
103.
Abstract

Preparation condition can affect the structure and the properties of nanofiber membrane. In order to explore suitable conditions to prepare the Fe3O4/PVDF nanofiber membrane with good hydrophobicity, the hydrophobicity of Fe3O4/PVDF nanofiber membranes obtained by electrospinning was investigated by changing preparation conditions like weight percentage of Fe3O4 nanoparticles, blending quality concentration of poly (vinylidene fluoride) (PVDF) and Fe3O4 nanoparticles, and positive voltage. And the variations of hydrophobicity of Fe3O4/PVDF nanofiber membranes modified by 1H, 1H, 2H, 2H-perfluorodecyl trimethoxysilane were studied. The results show that the hydrophobicity of Fe3O4/PVDF nanofiber membranes has changed under different preparation conditions. The contact angles of samples increased after a modification by 1H, 1H, 2H, 2H-perfluorodecyl trimethoxysilane, which indicates that the hydrophobicity of Fe3O4/PVDF nanofiber membranes has been enhanced.  相似文献   
104.
105.
106.
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   
107.
Neural Computing and Applications - The goal of this paper is to introduce a novel hybrid model called multi-fuzzy N-soft set, and to design an adjustable decision-making methodology for solving...  相似文献   
108.
109.
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   
110.
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   
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