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   814353篇
  免费   11095篇
  国内免费   2453篇
电工技术   14831篇
综合类   825篇
化学工业   121957篇
金属工艺   29774篇
机械仪表   23156篇
建筑科学   21125篇
矿业工程   2936篇
能源动力   22228篇
轻工业   75110篇
水利工程   7358篇
石油天然气   10699篇
武器工业   49篇
无线电   97307篇
一般工业技术   153387篇
冶金工业   160428篇
原子能技术   14254篇
自动化技术   72477篇
  2021年   6664篇
  2020年   4827篇
  2019年   6135篇
  2018年   10304篇
  2017年   10127篇
  2016年   10734篇
  2015年   7877篇
  2014年   12925篇
  2013年   37895篇
  2012年   21097篇
  2011年   29596篇
  2010年   23193篇
  2009年   26076篇
  2008年   27145篇
  2007年   27055篇
  2006年   23944篇
  2005年   22006篇
  2004年   21209篇
  2003年   20912篇
  2002年   19971篇
  2001年   19973篇
  2000年   18546篇
  1999年   19786篇
  1998年   49603篇
  1997年   35219篇
  1996年   27200篇
  1995年   20787篇
  1994年   18230篇
  1993年   17801篇
  1992年   12867篇
  1991年   12275篇
  1990年   11807篇
  1989年   11460篇
  1988年   10802篇
  1987年   9403篇
  1986年   9251篇
  1985年   10819篇
  1984年   10116篇
  1983年   8879篇
  1982年   8315篇
  1981年   8394篇
  1980年   7940篇
  1979年   7746篇
  1978年   7343篇
  1977年   8906篇
  1976年   11997篇
  1975年   6293篇
  1974年   5999篇
  1973年   5984篇
  1972年   4877篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
For pt.I see ibid., p.42-55 (2003). The development of a comprehensive decision support system, GMCR II, for the systematic study of real-world interactive decision problems is presented. The companion paper (Part I), discusses how GMCR II elicits, stores, and manages conflict models; here (Part II), the focus is on GMCR IIs analysis and output interpretation subsystems. Specifically, this paper describes the powerful and efficient analysis engine contained in GMCR II, its informative output presentation and interpretation facilities, and a number of follow-up analyses. Furthermore, an illustrative case study is used to demonstrate how GMCR II can be conveniently applied in practice.  相似文献   
62.
The problem considered in this paper is the design and tuning of the control system of a power-split continuously variable transmission (CVT) used in high-power tractors. Power-split CVTs are characterized by the combination of a traditional mechanical transmission and by a continuously-variable transmission. This guarantees, at the same time, smooth variations of the transmission-ratio and high efficiency of the overall transmission system. The control architecture of an hydrostatic power-split CVT is constituted by three main parts: 1) servo-controller on the current of the valve which drives the hydraulic transmission; 2) a servo-controller on the hydraulic transmission-ratio; and 3) a synchronizer which coordinates the hydraulic and the mechanical parts of the CVT. In this work, these three controllers are fully developed, including: design, implementation, and evaluation on an experimental system.  相似文献   
63.
The current Internet and wireless networks are harsh environments for transporting high-bandwidth multimedia data. We examine the technical issues involved, and describe an end-to-end solution to support a Web-based learn-on-demand system that operates in a wireless campus environment.  相似文献   
64.
This paper describes a novel planar antenna sensor created for the purpose of noninvasive temperature measurements using microwave radiometry. In order to improve radiometric measurements in industrial applications, a new generation of sensors is introduced, composed of a metallic sheet. Simulations based upon the method of moments is used both to design and to determine their electromagnetic performances. This paper also describes a radiometric device using these sensors to measure and control the temperature of food products during deep freezing processes. The results and discussions are presented.  相似文献   
65.
This paper describes techniques for the on-chip measurement of high-frequency and/or high-bandwidth electrical phenomena in ultra large-scale integration environments. The techniques rely on the integration of multiple compact and robust electronic test devices, or cores, at various locations within an integrated circuit. The cores consist primarily of signal generators that approximate the output of a sigma-delta modulator using finite repetitious bit patterns and a small set of highly robust analog components. They are capable of digitizing on-chip signals at gigahertz rates even using low-cost manufacturing processes. Simple communication between the multiple cores enables the migration of many "board-level" type measurements down to the chip level.  相似文献   
66.
67.
68.
Gas/liquid mass transfer has been investigated using a stirred vessel gas/liquid contactor using non‐Newtonian media and carbon dioxide as absorbent and gas phase, respectively. The volumetric mass transfer coefficients at different operational variables have been determined. Non‐Newtonian media (liquid phase) were prepared as aqueous solutions of sodium carboxymethyl cellulose salt. The influence of the rheological properties, polymer concentration, stirring rate, and gas flow rate on mass transfer was studied for these liquid phases. Kinematic viscosity and density experimental data were used to calculate the average molecular weight corresponding to the polymer employed. The Ostwald model has been used to fit the rheological behavior of aqueous solutions of the polymer employed as absorbent phase. Reasonably good agreement was found between the predictions of the proposed models and the experimental data of mass transfer coefficients.  相似文献   
69.
This article investigates the asymptotic performance of single parity-check (SPC) product codes (PCs) from a decoding point of view. Specifically, the probability of bit error is bounded before and after the decoding of each dimension, similar to the analysis of "iterated codes" by Elias (1954). It is shown that the asymptotic probability of bit error can be driven to zero as the number of dimensions, and hence the block length, increases at signal-to-noise ratios (SNRs) within 2 dB of capacity over the additive white Gaussian noise (AWGN) channel.  相似文献   
70.
Long-range prediction of the mobile-radio fading envelope is an enabling technology for many fading compensation approaches. Because the fading envelope is well modeled as a bandlimited process, it has special predictability properties. In this paper, we find a linear predictor that is optimal in the mean-square sense when the predictor impulse response is energy constrained. This solution may be used to determine the minimum mean squared error of a prediction based on past values that are corrupted with estimation errors.  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