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   32883篇
  免费   1180篇
  国内免费   1034篇
电工技术   807篇
综合类   428篇
化学工业   4125篇
金属工艺   2753篇
机械仪表   1558篇
建筑科学   971篇
矿业工程   217篇
能源动力   1174篇
轻工业   1601篇
水利工程   301篇
石油天然气   665篇
武器工业   35篇
无线电   4171篇
一般工业技术   8146篇
冶金工业   4733篇
原子能技术   398篇
自动化技术   3014篇
  2024年   47篇
  2023年   181篇
  2022年   376篇
  2021年   519篇
  2020年   404篇
  2019年   514篇
  2018年   675篇
  2017年   651篇
  2016年   705篇
  2015年   696篇
  2014年   968篇
  2013年   2113篇
  2012年   1443篇
  2011年   1974篇
  2010年   1570篇
  2009年   1783篇
  2008年   1737篇
  2007年   1738篇
  2006年   1530篇
  2005年   1424篇
  2004年   1121篇
  2003年   1058篇
  2002年   1007篇
  2001年   975篇
  2000年   904篇
  1999年   989篇
  1998年   1737篇
  1997年   1263篇
  1996年   1081篇
  1995年   724篇
  1994年   591篇
  1993年   478篇
  1992年   332篇
  1991年   324篇
  1990年   216篇
  1989年   236篇
  1988年   176篇
  1987年   132篇
  1986年   95篇
  1985年   101篇
  1984年   68篇
  1983年   53篇
  1982年   61篇
  1981年   55篇
  1980年   33篇
  1979年   22篇
  1977年   28篇
  1976年   38篇
  1974年   26篇
  1973年   24篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
5.
Spinel LiSr0·1Cr0·1Mn1·8O4 was synthesised by high temperature solid state method in order to enhance the electrochemical performance. The LiSr0·1Cr0·1Mn1·8O4 (LSCMO) materials were characterised by X-ray diffraction (XRD), scanning electron microscopy (SEM) and electrochemical tests. The XRD and SEM studies confirm that LSCMO had spinel crystal structure with a space group of Fd3m, and the particle of LSCMO shows irregular shape. The cyclic voltammetry data illustrated that the heavy current charge–discharge performance of LMO was improved by Sr2+ and Cr3+ doping. The galvanostatic charge–discharge of LSCMO cathode materials was measured at 1, 5, 10 and 20 C. The results indicated that LSCMO improved the capacity retention.  相似文献   
6.
Tian  J. Y.  Xu  G.  Hu  H. J.  Zhou  M. X. 《Strength of Materials》2019,51(3):439-449
Strength of Materials - A metallographic method, dilatometry, and X-ray diffraction were applied to investigate the effects of undercooling and holding time on bainitic transformation,...  相似文献   
7.
8.
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   
9.
Based on the phase transformation theories, especially the T0 concept of bainite transformation, alloy optimisation of bainitic steel with carbides has been carried out aiming at the produce of plastic mould with large cross-section. The effect of manganese and silicon on proeutectoid ferrite and bainite transformation is explored by dilatometric analysis, XRD and different microscopy techniques. The results show that after the alloy optimisation, the transformation of proeutectoid ferrite is suppressed and when the cooling rate is lower than 0·1°C?s??1, the new lower bainite transformation appears by decreasing carbon capacity of austenite and promoting carbide precipitation. Industrial production proves that the optimised alloy SDP1 can meet the demand for the plastic mould with the thickness of 1050?mm.  相似文献   
10.
A new constitutive equation of thermoelasticity for crystals is presented based on the interatomic potential and solid mechanics at finite temperature. Using the new constitutive equation, the calculations for crystal copper and graphene are carried out under different loading paths at different temperatures. The calculated results are in good agreement with those of the previous thermoelasticity constitutive equation based on quantum mechanics, which clearly indicates that our new constitutive equation of thermoelasticity is correct. A lot of comparisons also show that the present theory is more concise and efficient than the previous thermal stress theory in the practical application.  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