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   740832篇
  免费   8555篇
  国内免费   1735篇
电工技术   13834篇
综合类   784篇
化学工业   114922篇
金属工艺   29927篇
机械仪表   23485篇
建筑科学   17040篇
矿业工程   4931篇
能源动力   18982篇
轻工业   60928篇
水利工程   8503篇
石油天然气   16726篇
武器工业   98篇
无线电   83089篇
一般工业技术   148228篇
冶金工业   129630篇
原子能技术   17448篇
自动化技术   62567篇
  2021年   6643篇
  2019年   6358篇
  2018年   11018篇
  2017年   11229篇
  2016年   11783篇
  2015年   7455篇
  2014年   12585篇
  2013年   33790篇
  2012年   19628篇
  2011年   26715篇
  2010年   21373篇
  2009年   23932篇
  2008年   24527篇
  2007年   24300篇
  2006年   21374篇
  2005年   19421篇
  2004年   18524篇
  2003年   18260篇
  2002年   17533篇
  2001年   17112篇
  2000年   16409篇
  1999年   16274篇
  1998年   38009篇
  1997年   27416篇
  1996年   21548篇
  1995年   16600篇
  1994年   14902篇
  1993年   14659篇
  1992年   11549篇
  1991年   10955篇
  1990年   10793篇
  1989年   10400篇
  1988年   9962篇
  1987年   8978篇
  1986年   8717篇
  1985年   9950篇
  1984年   9066篇
  1983年   8573篇
  1982年   7865篇
  1981年   7988篇
  1980年   7555篇
  1979年   7580篇
  1978年   7381篇
  1977年   8303篇
  1976年   10366篇
  1975年   6678篇
  1974年   6520篇
  1973年   6639篇
  1972年   5529篇
  1971年   5181篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
92.
The process of combustion of homogeneous and heterogeneous nongasifying and slightly gasifying systems over the range of a number of parameters characterizing the reactive composition and the conditions for the arrangement of the combustion process is studied by using thermocouple and optical methods. The regions of the implementation of different combustion regimes, namely, steady, pulsating, multiple-point, and spin, are determined experimentally.Institute of Structural Macrokinetics, Russian Academy of Sciences, Chernogolovka. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 65, No. 4, pp. 407–411, October, 1993.  相似文献   
93.
An extended logistic model with a varying asymptotic upper bound for long-range peak demand forecasting is described. The model has been applied to a typical fast growing system, the Saudi Consolidated Electric Company. The forecasts are compared with actual demands and with those obtained from classical forecasting methods. The model gave relatively accurate peak demand forecasts compared with other classical methods. The model with a single load observation is capable of producing several peak demand forecasts corresponding to different levels of maximum temperature and various levels of social activity. The forecasts produced by the model were also stable irrespective of the length of the ex-post simulation period  相似文献   
94.
An experimental and theoretical analysis of the nonlinear coupling mechanism between the two solitary pulses circulating in a two-color femtosecond laser is presented. Two operation regimes; synchronized; and nonsynchronized; and a hysteresis of the transition between the two regimes are clearly observed; while independent modelocking and tunability of the output pulse trains is found in both regimes. Pulses in the range from 15 to 100 fs are synchronized with a timing jitter below 2 fs. The combined effects of cross-phase modulation and negative group velocity dispersion are shown to be responsible for the strong pulse correlation in the synchronized regime. Our experimental observations are in agreement with numerical simulations, thus confirming the theoretical model  相似文献   
95.
96.
97.
A systematic and straightforward procedure is developed for the synthesis and analysis of transformer-isolated power converters. The procedure can be used to determine the ranges of duty-ratio over which the transformer-isolated power converters of a given class can be operated without transformer saturation. The procedure can also be used to study the dependence of the power converter switch stresses on duty-ratios. This information is useful in the selection of the transformer-isolated power converter most suitable for a given application and in the design of this power converter with minimum switch stresses, high power density, and low cost  相似文献   
98.
Carboxyl-terminated butadiene-acrylonitrile-rubber decreases modulus and yield stress of the studied epoxy but increases fracture toughness. The addition of glass bead compensates for the loss in modulus but has little effect on yield stress. However, it significantly contributes to the fracture toughness by providing additional mechanisms for toughening of both the unmodified and rubber-modified epoxy. For the toughened epoxies studied, fracture surfaces gave only limited information on fracture mechanisms since significant energy absorption also occurs in the material below the fracture surface. Suggestions for suitable material compositions for fiber composite matrices are given.  相似文献   
99.
The technological process of cold forging applied for the first time in the production of the casing of the internal joint with races is described. The process operations of cold forging and the annealing and carburizing regimes for this part me described.  相似文献   
100.
Carey  D.H. 《Micro, IEEE》1993,13(2):19-27
The trends in high density interconnection (HDI) multichip module (MCM) techniques that have the potential to reduce interconnection cost and production time are described. The implementation in laminated dielectric (MCM-L) technology of a workstation processor core illustrates current substrate technology capabilities. The design, routing, layout and thermal management of the processor core are described. Thin-film deposited dielectric (MCM-D) technology is discussed as a cost-effective method for future interconnection applications  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