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   178842篇
  免费   2161篇
  国内免费   704篇
电工技术   3322篇
综合类   103篇
化学工业   28048篇
金属工艺   7800篇
机械仪表   5156篇
建筑科学   4510篇
矿业工程   880篇
能源动力   4714篇
轻工业   16502篇
水利工程   1730篇
石油天然气   3133篇
武器工业   2篇
无线电   19975篇
一般工业技术   33559篇
冶金工业   33890篇
原子能技术   4311篇
自动化技术   14072篇
  2021年   1328篇
  2019年   1260篇
  2018年   2112篇
  2017年   2092篇
  2016年   2203篇
  2015年   1589篇
  2014年   2751篇
  2013年   7894篇
  2012年   4589篇
  2011年   6413篇
  2010年   5076篇
  2009年   5919篇
  2008年   5912篇
  2007年   5899篇
  2006年   5068篇
  2005年   4731篇
  2004年   4526篇
  2003年   4181篇
  2002年   4155篇
  2001年   4158篇
  2000年   3958篇
  1999年   4099篇
  1998年   10554篇
  1997年   7516篇
  1996年   5749篇
  1995年   4348篇
  1994年   3667篇
  1993年   3612篇
  1992年   2641篇
  1991年   2566篇
  1990年   2441篇
  1989年   2473篇
  1988年   2407篇
  1987年   2149篇
  1986年   2088篇
  1985年   2399篇
  1984年   2200篇
  1983年   2027篇
  1982年   1901篇
  1981年   1971篇
  1980年   1813篇
  1979年   1830篇
  1978年   1789篇
  1977年   2144篇
  1976年   2723篇
  1975年   1565篇
  1974年   1556篇
  1973年   1621篇
  1972年   1362篇
  1971年   1270篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
81.
82.
Lenin Dnepropetrovsk Pipe Plant. Translated from Metallurg, No. 8, p. 39, August, 1989.  相似文献   
83.
Depending on the spectal width of the source illuminating an interferometer, measurement procedures can utilize either the whole interferogram, or only the fringe envelope, or only the fringe quick oscillations. With an ultraband spectrum source, a simplified adaptation of the methods of Fourier transform spectroscopy yields the variations of the test-fiber propagation constant over the whole wavelength-interval of the source. Chromatic dispersion can then be computed from a single interferogram. With narrower spectrum sources, only the fringe envelopes are utilized and yield measurements of mode delay, with application to chromatic and polarization mode dispersion. In this case, however, interferograms at several wavelengths are necessary. With even narrower spectrum sources, the fringe quick oscillations provide measurements of phase shifts, related to changes in the mode propagation constant, when outside perturbations are applied to the test fiber. A direct method for measuring the third-order nonlinear susceptibilities is discussed. In this case the outside perturbation is an intense pump laser field  相似文献   
84.
The aim of this paper is the comparison of the axial flux (AF) structures versus the conventional radial flux (RF) structures for permanent-magnet synchronous motors. The comparison procedure is based on simple thermal considerations. Two motor typologies are chosen and compared in terms of delivered electromagnetic torque. The comparison is developed for different motor dimensions and the pole number influence is put into evidence. The paper reports the complete comparison procedure and the related results analysis. The obtained results show that, when the axial length is very short and the pole number is high, the AF motors can be an attractive alternative to the conventional RF solutions.  相似文献   
85.
86.
87.
88.
Incremental transmission loss analysis has been used for decades, but recent interest in its application to loss allocation calls for new in-depth results. This paper demonstrates that, for incremental methods to be applied correctly in loss allocation, it is first necessary to specify the load distribution and loss supply strategies. Incremental loss allocation among bus power injections is shown to be arbitrary and, therefore, open to challenge as discriminatory. Loss allocation is possible among incremental loads and/or generators, but the proportion of the total losses assigned to either one is arbitrary. Unique, nonarbitrary incremental loss allocations are however possible among the "equivalent" incremental bilateral exchanges between generators and loads. From these basic components it is possible then to calculate the allocation among generators or loads in any specified proportion. The main results, although developed initially for small increments, are extended to large variations. Finally, a general incremental loss allocation algorithm is developed and tested  相似文献   
89.
The equal-channel angular extrusion (ECAE) technique has been applied to a powder metallurgy (P/M) source Be alloy. Extrusions have been successfully completed on Ni-canned billets of Be at approximately 425°C. No cracking was observed in the billets, and significant grain refinement was achieved. In this article, microstructural features and dislocation structures are discussed for a singlepass extrusion, including evidence of <c> and <c+a> dislocations. Significant crystallographic texture developed during ECAE, which is discussed in terms of this unique deformation processing technique and the underlying physical processes which sustain the deformation. S.R. AGNEW, formerly with the Oak Ridge National Laboratory, Oak Ridge, TN 37831-6115 This article is based on a presentation made in the symposium entitled “Defect Properties and Mechanical Behavior of HCP Metals and Alloys” at the TMS Annual Meeting, February 11–15, 2001, in New Orleans, Louisiana, under the auspices of the following ASM committees: Materials Science Critical Technology Sector, Structural Materials Division, Electronic, Magnetic & Photonic Materials Division, Chemistry & Physics of Materials Committee, Joint Nuclear Materials Committee, and Titanium Committee.  相似文献   
90.
The article presents the results of experimental investigations of critical (limit) heat fluxes upon evaporation on porous coatings, and it substantiates the physical model of the process.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 49, No. 4, pp. 607–614, October, 1985.  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