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   116635篇
  免费   3256篇
  国内免费   439篇
电工技术   1025篇
综合类   2334篇
化学工业   18001篇
金属工艺   5432篇
机械仪表   3767篇
建筑科学   3092篇
矿业工程   640篇
能源动力   1733篇
轻工业   9159篇
水利工程   1554篇
石油天然气   463篇
武器工业   5篇
无线电   10617篇
一般工业技术   21928篇
冶金工业   10618篇
原子能技术   408篇
自动化技术   29554篇
  2023年   314篇
  2022年   329篇
  2021年   830篇
  2020年   722篇
  2019年   816篇
  2018年   15534篇
  2017年   14421篇
  2016年   11203篇
  2015年   1729篇
  2014年   1582篇
  2013年   3043篇
  2012年   5103篇
  2011年   11018篇
  2010年   9681篇
  2009年   6790篇
  2008年   7950篇
  2007年   8850篇
  2006年   927篇
  2005年   1891篇
  2004年   1766篇
  2003年   1750篇
  2002年   1116篇
  2001年   529篇
  2000年   588篇
  1999年   525篇
  1998年   2454篇
  1997年   1674篇
  1996年   1093篇
  1995年   644篇
  1994年   505篇
  1993年   592篇
  1992年   228篇
  1991年   238篇
  1990年   164篇
  1989年   175篇
  1988年   184篇
  1987年   149篇
  1986年   131篇
  1985年   162篇
  1984年   139篇
  1983年   107篇
  1982年   141篇
  1981年   169篇
  1980年   172篇
  1979年   93篇
  1978年   96篇
  1977年   294篇
  1976年   640篇
  1973年   78篇
  1954年   69篇
排序方式: 共有10000条查询结果,搜索用时 432 毫秒
51.
52.
53.
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   
54.
55.
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   
56.
57.
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   
58.
Understanding semantic word shifts in scientific domains is essential for facilitating interdisciplinary communication. Using a data set of published papers in the field of information retrieval (IR), this paper studies the semantic shifts of words in IR based on mining per-word topic distribution over time. We propose that semantic word shifts not only occur over time, but also over topics. The shifts are examined from two perspectives, the topic-level and the context-level. According to the over-time word-topic distribution, stable words and unstable words are recognized. The diverging and converging trends in the unstable type reveal characteristics of the topic evolution process. The context-level shifts are further detected by similarities between word vectors. Our work associates semantic word shifts with the evolving of topics, which facilitates a better understanding of semantic word shifts from both topics and contexts.  相似文献   
59.
Research funding has been seen as one of the most important resource in the reward system of science. And usage of publications denotes an interesting perspective of user behavior in scientific communication. This study aims to address the relationship between funding and Usage Count, which is a new metrics item established on the platform of Web of Science. Full records of 300,010 articles published in 2013 were downloaded in October 2015, and divided into six disciplines, including information science library science, education educational research, economics, computer science, materials science, and chemistry. Seven indicators were proposed to measure the impact, including Funding rate, Citation per paper, Usage rate, Usage per paper, Citation difference, Usage difference, and Conversion rate. It concluded funding has impact on usage and citation, and funded papers attract more usage, but varying in different disciplines. Usage Count can be used in the extension of citation metrics but with limits. This study originally engages with usage metrics and detected that there is positive correlation between usage and funding.  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