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   36188篇
  免费   2391篇
  国内免费   36篇
电工技术   281篇
综合类   20篇
化学工业   7271篇
金属工艺   743篇
机械仪表   800篇
建筑科学   1005篇
矿业工程   90篇
能源动力   641篇
轻工业   5898篇
水利工程   333篇
石油天然气   127篇
武器工业   5篇
无线电   1619篇
一般工业技术   6461篇
冶金工业   8052篇
原子能技术   143篇
自动化技术   5126篇
  2024年   87篇
  2023年   327篇
  2022年   333篇
  2021年   864篇
  2020年   768篇
  2019年   854篇
  2018年   1527篇
  2017年   1493篇
  2016年   1553篇
  2015年   1188篇
  2014年   1385篇
  2013年   2949篇
  2012年   2115篇
  2011年   1944篇
  2010年   1606篇
  2009年   1438篇
  2008年   1372篇
  2007年   1265篇
  2006年   834篇
  2005年   737篇
  2004年   694篇
  2003年   621篇
  2002年   606篇
  2001年   447篇
  2000年   428篇
  1999年   478篇
  1998年   2400篇
  1997年   1652篇
  1996年   1059篇
  1995年   643篇
  1994年   507篇
  1993年   586篇
  1992年   224篇
  1991年   228篇
  1990年   167篇
  1989年   176篇
  1988年   178篇
  1987年   153篇
  1986年   137篇
  1985年   165篇
  1984年   156篇
  1983年   119篇
  1982年   155篇
  1981年   168篇
  1980年   173篇
  1979年   105篇
  1978年   105篇
  1977年   297篇
  1976年   648篇
  1973年   88篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
52.
The efficient substitution of sucrose by a sweetener in beverages requires the application of some sensory techniques. First, one must determine the concentrations of the sweeteners under study, equivalent in sweetness to the ideal sucrose concentration. In addition, it is fundamental to determine which is most similar to sucrose. The objectives of this study were to determine the ideal sweetness for espresso coffee and the equivalent concentrations in sweetness of different sweeteners, as well as characterise the time–intensity profile of each sweetener in relation to sweetness. The sweeteners evaluated were sucralose, aspartame, neotame, a cyclamate/saccharin mixture (2:1) and stevia. The sucrose concentration considered ideal by consumers was 12.5% (w/v), and the equivalent concentrations of the sweeteners were 0.0159% for sucralose, 0.0549% for aspartame, 0.0016% for neotame, 0.0359% for the cyclamate/saccharin mixture and 0.0998% for stevia. The time–intensity analysis indicated that possibly the sweeteners neotame, aspartame and sucralose would be the best substitutes for sucrose.  相似文献   
53.
54.
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   
55.
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   
56.
57.
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   
58.
59.
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   
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