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   905926篇
  免费   10372篇
  国内免费   2473篇
电工技术   16043篇
综合类   2998篇
化学工业   137282篇
金属工艺   37542篇
机械仪表   29339篇
建筑科学   20545篇
矿业工程   5940篇
能源动力   23493篇
轻工业   67672篇
水利工程   10660篇
石油天然气   18497篇
武器工业   46篇
无线电   101463篇
一般工业技术   181818篇
冶金工业   152159篇
原子能技术   19324篇
自动化技术   93950篇
  2021年   7672篇
  2020年   5782篇
  2019年   7375篇
  2018年   25676篇
  2017年   24743篇
  2016年   22459篇
  2015年   9104篇
  2014年   14487篇
  2013年   39316篇
  2012年   25273篇
  2011年   39053篇
  2010年   31878篇
  2009年   32491篇
  2008年   34130篇
  2007年   34553篇
  2006年   24342篇
  2005年   22929篇
  2004年   21858篇
  2003年   21695篇
  2002年   20138篇
  2001年   19362篇
  2000年   18447篇
  1999年   18617篇
  1998年   45465篇
  1997年   32229篇
  1996年   25038篇
  1995年   18908篇
  1994年   16921篇
  1993年   16716篇
  1992年   12506篇
  1991年   11917篇
  1990年   11757篇
  1989年   11344篇
  1988年   10787篇
  1987年   9731篇
  1986年   9370篇
  1985年   10697篇
  1984年   9732篇
  1983年   9100篇
  1982年   8276篇
  1981年   8446篇
  1980年   7886篇
  1979年   7955篇
  1978年   7792篇
  1977年   8792篇
  1976年   11174篇
  1975年   6899篇
  1974年   6620篇
  1973年   6725篇
  1972年   5684篇
排序方式: 共有10000条查询结果,搜索用时 158 毫秒
41.
The design of a sylphon bellows sensor and the basic circuits of an LC-generator and of a microprocessor unit are presented. An analytical pressure–frequency conversion function and a special method of adjusting the sensor ensure an error of less than 0.05%. The dynamic range is up to 105. The instruments developed cover the ranges 103, 104, and 105 Pa.  相似文献   
42.
Essential work of fracture methodology was used to determine plane-stress ductile fracture toughness of high impact polystyrene film of thickness 0.26 mm. Results obtained indicated that specific essential work of fracture, w e, is independent of loading rate, and for certain specimen sizes, independent of both gauge length and width of the specimen. On the other hand, w e was found to be affected by the temperature, molecular anisotropy and the geometry of the test specimens. Reasonable estimate of w e was obtained via crack opening displacement value.  相似文献   
43.
This paper proposes a method for designing a robust full-order observer for vector-controlled induction motors taking core loss into account. Although conventional research focuses on parameter identification, global stability of the identification remains questionable. Therefore, robustness against some parameters is required. This paper describes the design of a robust full-order observer which takes core loss into account, using both the gain-scheduled H/sub /spl infin// control and the linear matrix inequality technique. This design always results in a stable controller. The robustness of the proposed method against variations of resistances is evaluated by experiments.  相似文献   
44.
Ho  Y. S.  Chiu  C. H.  Tseng  T. M.  Chiu  W. T. 《Scientometrics》2003,57(3):369-376
Honour Index (HoI), a method to evaluate research performance within different research fields, was derived from the impact factor (IF). It can be used to rate and compare different categories of journals. HoI was used in this study to determine the scientific productivity of stem cell research in the Asian Four Dragons (Hong Kong, Singapore, South Korea and Taiwan) from 1981 to 2001. The methodology applied in this study represents a synthesis of universal indicator studies and bibliometric analyses of subfields at the micro-level. We discuss several comparisons, and conclude the developmental trend in stem cell research for two decades. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   
45.
46.
Chloride doped polyaniline conducting polymer films have been prepared in a protic acid medium (HCl) by potentiodynamic method in an electrochemical cell and studied by cyclic voltammetry and FTIR techniques. The FTIR spectra confirmed Cl- ion doping in the polymers. The polymerization rate was found to increase with increasing concentration of aniline monomer. But the films obtained at high monomer concentration were rough having a nonuniform flaky polyaniline distribution. Results showed that the polymerization rate did not increase beyond a critical HCl concentration. Cyclic voltammetry suggested that, the oxidation-reduction current increased with an increase in scan rate and that the undoped polyaniline films were not hygroscopic whereas chloride doped polyaniline films were found to be highly hygroscopic.  相似文献   
47.
A redundant multivalued logic is proposed for high-speed communication ICs. In this logic, serial binary data are received and converted into parallel redundant multivalued data. Then they are restored into parallel binary data. Because of the multivalued data conversion, this logic makes it possible to achieve higher operating speeds than that of a conventional binary logic. Using this logic, a 1:4 demultiplexer (DEMUX, serial-parallel converter) IC was fabricated using a 0.18-/spl mu/m CMOS process. The IC achieved an operating speed of 10 Gb/s with a supply voltage of only 1.3 V and with power consumption of 38 mW. This logic may achieve CMOS communication ICs with an operating speed several times greater than 10 Gb/s.  相似文献   
48.
Reducing CIC filter complexity   总被引:1,自引:0,他引:1  
This paper provides several tricks to reduce the complexity and enhance the usefulness of cascaded integrator-comb (CIC) filters. The first trick shows a way to reduce the number of adders and delay elements in a multi-stage CIC interpolation filter. The result is a multiplierless scheme that performs high-order linear interpolation using CIC filters. The second trick shows a way to eliminate the integrators from CIC decimation filters. The benefit is the elimination of unpleasant data word growth problems.  相似文献   
49.
This paper presents a hand-held microsystem based on new fully integrated magnetoresistive biochips for biomolecular recognition (DNA hybridization, antibody antigen interaction, etc.). Magnetoresistive chip surfaces are chemically treated, enabling the immobilization of probe biomolecules such as DNA or antibodies. Fluid handling is also integrated in the biochip. The proposed microsystem not only integrates the biochip, which is an array of 16times16 magnetoresistive sensors, but it also provides all the electronic circuitry for addressing and reading out each transducer. The proposed architecture and circuits were specifically designed for achieving a compact, programmable and portable microsystem. The microsystem also integrates a hand-held analyzer connected through a wireless channel. A prototype of the system was already developed and detection of magnetic nanoparticles was obtained. This indicates that the system may be used for magnetic label based bioassays  相似文献   
50.
This paper presents a novel power-driven multiplication instruction-set design method for application-specific instruction-set processors (ASIPs). Based on a dual-and-configurable-multiplier structure, our proposed method devises a multiplication instruction set for low-power ASIPs. Our method exploits the execution sequences of multiplication instructions and effective bit widths of variables to reduce power consumed by redundant multiplication bits while minimizing the multiplication execution time. Experimental results on a set of DSP programs demonstrate that our proposed method achieves significant power reduction (up to 18.53%) and execution time improvement (up to 10.43%) with 18% area overhead.  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