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   328823篇
  免费   3596篇
  国内免费   875篇
电工技术   6660篇
综合类   416篇
化学工业   45864篇
金属工艺   16461篇
机械仪表   13655篇
建筑科学   7400篇
矿业工程   1801篇
能源动力   7018篇
轻工业   23924篇
水利工程   3605篇
石油天然气   5179篇
武器工业   68篇
无线电   41060篇
一般工业技术   68178篇
冶金工业   51697篇
原子能技术   6362篇
自动化技术   33946篇
  2021年   2036篇
  2019年   2033篇
  2018年   11266篇
  2017年   11896篇
  2016年   8171篇
  2015年   2811篇
  2014年   4132篇
  2013年   11333篇
  2012年   8994篇
  2011年   16745篇
  2010年   14579篇
  2009年   14328篇
  2008年   14865篇
  2007年   16769篇
  2006年   7866篇
  2005年   10539篇
  2004年   8760篇
  2003年   8263篇
  2002年   7004篇
  2001年   6530篇
  2000年   6297篇
  1999年   6272篇
  1998年   14244篇
  1997年   10270篇
  1996年   8124篇
  1995年   6418篇
  1994年   5733篇
  1993年   5603篇
  1992年   4563篇
  1991年   4231篇
  1990年   4048篇
  1989年   3779篇
  1988年   3629篇
  1987年   3170篇
  1986年   3065篇
  1985年   3610篇
  1984年   3382篇
  1983年   3031篇
  1982年   2850篇
  1981年   2951篇
  1980年   2760篇
  1979年   2648篇
  1978年   2499篇
  1977年   2945篇
  1976年   3554篇
  1975年   2316篇
  1974年   2312篇
  1973年   2318篇
  1972年   1849篇
  1971年   1745篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
101.
The Raman spectrum of water adsorbed on a metallic silver surface reveals an anomalously large shift of the vibrational frequency as compared to that in the bulk. The results are compared to data reported by other researchers, and possible interpretations of the observed phenomenon are discussed.  相似文献   
102.
The behavior of a superelastic Cu?14.2% Al?4%Ni single crystal in the case of high reversible strains under a longitudinal bending force was investigated. The effect of strain confinement along the crystal length was revealed and studied. The highest reversible strains (up to 10%) were shown to be confined within the central part of the bent crystal.  相似文献   
103.
X-ray diffraction analysis has been used to study the structure of the α-Zr matrix phase and the precipitation of β-Nb particles upon the annealing of a Zr–2.5% Nb deformed alloy. It has been found that the process of the precipitation of the strengthening β-Nb particles in the alloy is accompanied by the appearance of fields of elastic interphase deformations in the matrix α phase of the alloy due to the difference in the specific atomic volumes of the crystal structures of the matrix and precipitated phases. It has been shown experimentally that, as a result of the presence of interphase deformations in the alloy, the bcc crystal structure of the precipitating β-Nb particles undergoes monoclinic distortions.  相似文献   
104.
105.
106.
Russian Engineering Research - The theoretically possible reconfigurable parallel mechanisms are classified, in terms of the layout of guides on the base. Formulas are derived for the...  相似文献   
107.
108.
109.
We show that in the presence of magnetic field, two superconducting phases with the center-of-mass momentum of Cooper pair parallel to the magnetic field are induced in Dresselhaus spin–orbit-coupled superconductor. Specifically, at small magnetic field, the center-of-mass momentum is induced due to the energy-spectrum distortion and no unpairing region with vanishing singlet correlation appears. We refer to this superconducting state as the drift-BCS state. By further increasing the magnetic field, the superconducting state falls into the Fulde–Ferrell state with the emergence of the unpairing regions. The observed abrupt enhancement of the center-of-mass momenta and suppression on the order parameters during the transition indicate the occurrence of a first-order phase transition. Enhanced Pauli limit and hence enlarged magnetic-field regime of the Fulde–Ferrell state, due to the spin-flip terms of the spin–orbit coupling, are revealed. We also address the triplet correlations induced by the spin–orbit coupling, and show that the Cooper-pair spin polarizations, generated by the magnetic field and center-of-mass momentum with the triplet correlations exhibit totally different magnetic-field dependences between the drift-BCS and Fulde–Ferrell states.  相似文献   
110.
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   
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