首页 | 官方网站   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   2390篇
  免费   45篇
  国内免费   18篇
工业技术   2453篇
  2023年   5篇
  2021年   28篇
  2020年   20篇
  2019年   17篇
  2018年   24篇
  2017年   29篇
  2016年   42篇
  2015年   23篇
  2014年   41篇
  2013年   58篇
  2012年   83篇
  2011年   94篇
  2010年   64篇
  2009年   69篇
  2008年   84篇
  2007年   87篇
  2006年   85篇
  2005年   68篇
  2004年   73篇
  2003年   77篇
  2002年   59篇
  2001年   51篇
  2000年   45篇
  1999年   65篇
  1998年   290篇
  1997年   155篇
  1996年   99篇
  1995年   65篇
  1994年   71篇
  1993年   81篇
  1992年   49篇
  1991年   27篇
  1990年   24篇
  1989年   27篇
  1988年   19篇
  1987年   24篇
  1986年   10篇
  1985年   27篇
  1984年   18篇
  1983年   14篇
  1982年   23篇
  1981年   20篇
  1980年   12篇
  1979年   10篇
  1978年   9篇
  1977年   14篇
  1976年   31篇
  1975年   8篇
  1974年   6篇
  1972年   7篇
排序方式: 共有2453条查询结果,搜索用时 15 毫秒
21.
A patient with subacute bacterial endocarditis and a peripheral mycotic aneurysm is presented. We used a combined multi-slice surface anatomy scanning (SAS) and contrast-enhanced MR angiography image to determine the exact location of the small lesion by applying a skin marker on the scalp and visualizing the relationship of the marker to the brain surface structures and to the lesion. This technique was useful for the removal of a small peripheral aneurysm using only a limited craniotomy.  相似文献   
22.
Cytogenin, 8-hydroxy-3-hydroxymethyl-6-methoxyisocoumarin, has low cytotoxicity on murine and human tumour cells in vitro. It augments or suppresses phagocytosis of macrophages and lymphocyte proliferation. It has been reported that cytogenin has a potent inhibitory effect clinically on adjuvant arthritis in Lewis rats and on type II collagen-induced arthritis in DBA/1J mice. Our experimental findings provide evidence that cytogenin has beneficial effects on spontaneous polyarthritis in MRL/1 mice and pristane-induced arthritis in DBA/1J mice. The results suggest that the mode of the anti-arthritic action of cytogenin is different from those of NSAIDs; although the precise mode of action remains unclear, cytogenin may become an excellent therapeutic agent for rheumatoid arthritis.  相似文献   
23.
Highly reliable telecommunication networks require new technologies, such as the reliability specification, design, and evaluation method used at NTT. This paper describes the basic concepts of this method, and the ARDES-NET (Availability Reliability Design and Evaluation System for NETworks) software tool is used to support the reliability design and evaluation. ARDESNET has a user-friendly interface and can be easily put into practice  相似文献   
24.
Some work is so complicated and unsteady that it is not possible to use automatic robots, such as FA robots. In such a case, a teleoperated manipulation system is applied. In this research, the authors aim at a reduction in the operator's physical and mental burdens. An artificially intelligent manipulator system has been developed with nonsymmetric and redundant master-slave. This system has five features: (1) a polar coordinates master arm; (2) a highly operational articulated slave arm with 7 degrees of freedom; (3) a nonsymmetric configuration and different degrees of freedom master-slave control; (4) an expert system; and (5) a new master-slave control motion, which makes the operator's task easier with automatic force/position control. The system was experimentally produced and its performance tested and evaluated. A qualitative evaluation was carried out by conducting a comparative test on the conventional master-slave control and the new master-slave control. It was found to be effective in reducing operating time, as well as work-induced fatigue.  相似文献   
25.
A numerical evaluation is conducted of electric field distributions, phase constants, and attenuation constants of the lowest eigenmode in the general class of uniformly bent circular hollow waveguides. The analysis is based on a scalar equation, and numerical results are compared with those of existing approximate theories. Normalized forms of attenuation constants are presented for the parallel and perpendicular polarizations to the bending plane by using structural and material parameters. For sharply bent waveguides, useful and simple expressions are derived for the attenuation constants of the TE and TM modes in the corresponding slab geometry with suitable weighting parameters  相似文献   
26.
The current status of high electron mobility transistor (HEMT) technology at Fujitsu for high-performance VLSI is presented, focusing on device performance in the submicrometer dimensional range and the HEMT LSIs implemented in supercomputer systems. The HEMT is a very promising device for ultrahigh-speed LSI/VLSI applications because of the high-mobility GaAs/AlGaAs heterojunction structure. A 1.1 K-gate bus-driver logic LSI has been developed to demonstrate the high-speed data transfer in a high-speed parallel processing system at room temperature, operating at 10.92 GFLOPS. A cryogenic 3.3 K-gate random number generator logic LSI with maximum clock frequency of 1.6 GHz has also been developed to demonstrate the high-clock-rate system operations at liquid-nitrogen temperature. For VLSI level complexity, a HEMT 64-kb static RAM with 1.2-ns access operation and a 45 K-gate gate array with 35-ps logic delay have been developed operating at room temperature, demonstrating the high performance required for future high-speed computer systems  相似文献   
27.
28.
一种PN码自适应捕获门限的改进算法   总被引:1,自引:0,他引:1  
刘震昆  黄顺吉 《信号处理》2006,22(4):458-461
文献[1]提出了一种用于直扩系统的PN码自适应门限算法。但该文献也指出,此算法对门限总数十分敏感。当门限总数设置不当时,系统的平均捕获时间将显著增加。这限制了该算法在实际中的应用。本文就此提出了改进,给出了算法及电路框图。仿真结果表明,与原方案相比,改进算法改善了对门限总数的敏感性,降低了PN码平均捕获时间。  相似文献   
29.
The off state current for polysilicon thin-film transistors for pixels in LCDs has been successfully reduced by introducing a polysilicon buffer layer between a polysilicon active layer fabricated by solid-phase-crystallisation (SPC) and a fused quartz substrate. Off-slate current of less than 1 pA under Vgs=-25 V at Vds=3 V was obtained for n-channel single-gate coplanar transistors using the buffer layer (400 Å)  相似文献   
30.
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-23

京公网安备 11010802026262号