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   171271篇
  免费   12665篇
  国内免费   6348篇
电工技术   9155篇
技术理论   11篇
综合类   8999篇
化学工业   28209篇
金属工艺   10242篇
机械仪表   10383篇
建筑科学   10168篇
矿业工程   4052篇
能源动力   3774篇
轻工业   9830篇
水利工程   3249篇
石油天然气   9843篇
武器工业   1098篇
无线电   18010篇
一般工业技术   27249篇
冶金工业   11212篇
原子能技术   4890篇
自动化技术   19910篇
  2024年   754篇
  2023年   2427篇
  2022年   4830篇
  2021年   6484篇
  2020年   4862篇
  2019年   4158篇
  2018年   5281篇
  2017年   5778篇
  2016年   5352篇
  2015年   5964篇
  2014年   7633篇
  2013年   9218篇
  2012年   9848篇
  2011年   10576篇
  2010年   8985篇
  2009年   8824篇
  2008年   8697篇
  2007年   8164篇
  2006年   7560篇
  2005年   6439篇
  2004年   4889篇
  2003年   4825篇
  2002年   4819篇
  2001年   4408篇
  2000年   3809篇
  1999年   3405篇
  1998年   2696篇
  1997年   2277篇
  1996年   2017篇
  1995年   1761篇
  1994年   1493篇
  1993年   1261篇
  1992年   1234篇
  1991年   1081篇
  1990年   1098篇
  1989年   1014篇
  1988年   901篇
  1987年   842篇
  1986年   764篇
  1985年   718篇
  1984年   702篇
  1981年   668篇
  1979年   736篇
  1978年   777篇
  1977年   739篇
  1976年   755篇
  1975年   713篇
  1974年   719篇
  1973年   723篇
  1972年   705篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
51.
52.
Technical Physics Letters - Possible designs of a terahertz laser that use the effect of Bloch oscillations in SiC natural superlattices have been considered. It has been proposed to use as a...  相似文献   
53.
Specifications require that all the welds in 12-m-diam. decomposers with a capacity of 3600 m3 be subjected to high-temperature tempering before going into service in order to alleviate the stresses from the welding operation. Specialists at the organizations VNIIPTkhimnefteapparatury and VNIImontazhspetsstroi have proposed out-of-furnace volumetric (complete) of the assembled decomposer with the use of special heaters. The use of this heating method has shortened assembly operations while providing the welds with a highquality heat treatment and reducing the stresses overall (including welding stresses, stresses from assembly of the decomposer, etc.) The technology ensures uniform heating of the housing of the decomposer and provides for close control over the process. The experience gained in heat-treating decomposers can also be used in the construction of other containers that come into contact with corrosive media. __________ Translated from Metallurg, No. 3, pp. 61–64, March, 2006.  相似文献   
54.
Paving-and roofing-grade asphalts were obtained at LUKOIL-Permnefteorgsintez Ltd. by mixing peroxidized asphalt and a number of high-boiling unoxidized petroleum products in certain ratios. The asphalts obtained have improved performance characteristics: high plasticity and low brittleness temperature. __________ Translated from Khimiya i Tekhnologiya Topliv i Masel, No. 2, pp. 26–28, May–June, 2006.  相似文献   
55.
The paper discusses optimal control of ecosystem state for observation of a generalized monotonically varying random parameter. A model is proposed for the controlled vector random process, whose components are assigned acceptable ranges and the observations are performed discretely. __________ Translated from Khimicheskoe i Neftegazovoe Mashinostroenie, No. 6, pp. 40–44, June, 2006.  相似文献   
56.
The basic methods of verifying continuous automatic belt weighers are described. A comparative analysis of these methods on the basis of experimental studies is made and ways of implementing the results in industry are recommended.  相似文献   
57.
The effect of crystal orientation on the photogeneration of free charge carriers was studied for C60 single crystals in a weak magnetic field. The photoconductivity sharply depends on the orientation of magnetic field with respect to the crystallographic directions, showing a 5–8% increase for seven axes of the C60 crystal.  相似文献   
58.
邵虞 《电子产品世界》2006,(7S):24-24,25,26,28,30
世界经济东移已成共识,20世纪是美国的世纪。21世纪是亚洲世纪。历史告诉我们:20世纪的标志性产业之一无疑是LSI。LSI是电子设备的心脏,正是它领导了电子工业的前进,当然地成了美国的重要战略产业。21世纪是视图时代,新世纪引领电子工业发展的是FPD,它是人与电子设备鲜活的界面,是提高和改善人类生活的重要一环,肯定是新世纪的标志性产业之一。事实证明,它已成为今天亚洲国家或地区的重要战略产业。 针对我国实际,作者2004年便提出了我国电子产业要由大变强,必需LSI与FPD“双业并举,共同发展”,不能再走先LSI后FPD的老路。为此,本刊不断发表文章,大力呼吁,愿智者垂听,愿读者赐教。[编者按]  相似文献   
59.
Mechanical behavior of a two-dimensional elastoplastic solid with rectilinear cracks is investigated. Plastic strip model is used to reduce plasticity problem to the equivalent linear elasticity formulation. Two realizations of the mixed mode plastic strip model are considered: in-line plastic strips as proposed by Becker and Gross [Int. J. Fract. 37 (1988) 163], and inclined plastic strips of Panasyuk and Savruk [Appl. Mech. Rev. 47 (1994) 151]. The effective mechanical response predictions are based on the procedure presented in Kachanov et al., [Appl. Mech. Rev. 47 (1994) 151]. Stress-strain relations are obtained for parallel and randomly oriented non-interacting cracks. Results are compared with known elastic solutions.  相似文献   
60.
Amphiphilic magnetic microspheres ranging in diameter from 5 to 100 µm were prepared by dispersion copolymerization of styrene and poly(ethylene oxide) vinylbenzyl (PEO‐VB) macromonomer (MPEO) in the presence of Fe3O4 magnetic fluid. The effects of various polymerization parameters on the average particle size were systematically investigated. The average particle size was found to increase with increasing styrene concentration and initiator concentration. It also increased with decreasing stabilizer concentration and molecular weight of MPEO. The content of the hydroxyl groups localized in the microspheres ranged from 0.01 to 0.2 mmol g?1. © 2003 Society of Chemical Industry  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