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   181113篇
  免费   2291篇
  国内免费   709篇
电工技术   3311篇
综合类   109篇
化学工业   29015篇
金属工艺   7818篇
机械仪表   5162篇
建筑科学   4592篇
矿业工程   888篇
能源动力   4742篇
轻工业   17072篇
水利工程   1729篇
石油天然气   3135篇
武器工业   2篇
无线电   19960篇
一般工业技术   33781篇
冶金工业   34139篇
原子能技术   4315篇
自动化技术   14343篇
  2021年   1509篇
  2019年   1342篇
  2018年   2202篇
  2017年   2160篇
  2016年   2283篇
  2015年   1661篇
  2014年   2847篇
  2013年   8026篇
  2012年   4720篇
  2011年   6579篇
  2010年   5217篇
  2009年   6032篇
  2008年   6064篇
  2007年   6021篇
  2006年   5150篇
  2005年   4806篇
  2004年   4583篇
  2003年   4236篇
  2002年   4220篇
  2001年   4195篇
  2000年   3987篇
  1999年   4139篇
  1998年   10457篇
  1997年   7439篇
  1996年   5725篇
  1995年   4328篇
  1994年   3671篇
  1993年   3616篇
  1992年   2662篇
  1991年   2552篇
  1990年   2463篇
  1989年   2502篇
  1988年   2420篇
  1987年   2174篇
  1986年   2117篇
  1985年   2415篇
  1984年   2238篇
  1983年   2054篇
  1982年   1908篇
  1981年   1989篇
  1980年   1823篇
  1979年   1835篇
  1978年   1798篇
  1977年   2130篇
  1976年   2716篇
  1975年   1579篇
  1974年   1565篇
  1973年   1622篇
  1972年   1360篇
  1971年   1270篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
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   
102.
Determined the specific type of sexual functioning deficits and the relationship between global sexual satisfaction and adjustment in 2 related life areas (marital relationship and body image) for 2 groups of cancer patients at high risk for sexual difficulties. The 2 groups included 16 27–67 yr old females with Stage 2 breast cancer and 16 31–65 yr old females with gynecologic cancer. These Ss were compared to 16 healthy female outpatients (controls). Measures included the Sexual Activities scale from the Derogatis Sexual Functioning Inventory, a modified version of the Dyadic Assessment Scale (marital adjustment), a global sexual evaluation, and a body-image scale. Analyses revealed that the aspects of sexual functioning for breast-cancer and gynecologic-cancer Ss that differed from those of controls were the frequency of sexual behaviors and the level of sexual arousal. Whereas Ss' evaluations of their current sexual life had no relationship to their marital-adjustment ratings, analyses suggested that body-image disruption may be a prevalent problem for gynecologic cancer patients. Data suggest that cancer diagnosis and treatment are instrumental in producing reductions in sexual activity and arousability. (34 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
103.
104.
105.
106.
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   
107.
Shevchenko  V. P.  Nagaev  I. Yu.  Myasoedov  N. F. 《Radiochemistry》2002,44(4):380-383
Androstenedione labeled with tritium at positions 1 and 2 was prepared. The molar radioactivity of the sample prepared using homogeneous catalysts was as high as 1.4-1.5 PBq mol- 1. [1,2-3H]Androst-4-ene-3,17-dione can be converted into the [1-3H]steroid with the molar radioactivity of 0.9 PBq mol- 1.  相似文献   
108.
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   
109.
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   
110.
Using a flow method, we have measured the vapor pressure of tellurium tetraiodide, an attractive reagent for chemical vapor deposition technology. The results, combined with earlier tensimetric data, have been used to evaluate the basic thermodynamic functions of TeI4 and its thermolysis products.  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