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   365523篇
  免费   4507篇
  国内免费   1639篇
电工技术   7363篇
综合类   427篇
化学工业   54965篇
金属工艺   15126篇
机械仪表   10981篇
建筑科学   9929篇
矿业工程   810篇
能源动力   9414篇
轻工业   37634篇
水利工程   2715篇
石油天然气   1850篇
武器工业   8篇
无线电   47298篇
一般工业技术   67143篇
冶金工业   70270篇
原子能技术   5553篇
自动化技术   30183篇
  2021年   2210篇
  2019年   2119篇
  2018年   3183篇
  2017年   3123篇
  2016年   3445篇
  2015年   2760篇
  2014年   4556篇
  2013年   16160篇
  2012年   7900篇
  2011年   11381篇
  2010年   9081篇
  2009年   10204篇
  2008年   11191篇
  2007年   11444篇
  2006年   10431篇
  2005年   9748篇
  2004年   9364篇
  2003年   9317篇
  2002年   9326篇
  2001年   9469篇
  2000年   8754篇
  1999年   9344篇
  1998年   21891篇
  1997年   15805篇
  1996年   12551篇
  1995年   9692篇
  1994年   8651篇
  1993年   8336篇
  1992年   6336篇
  1991年   6201篇
  1990年   5723篇
  1989年   5652篇
  1988年   5447篇
  1987年   4683篇
  1986年   4596篇
  1985年   5552篇
  1984年   4969篇
  1983年   4604篇
  1982年   4290篇
  1981年   4204篇
  1980年   3963篇
  1979年   3834篇
  1978年   3675篇
  1977年   4512篇
  1976年   6284篇
  1975年   3221篇
  1974年   2998篇
  1973年   2970篇
  1972年   2444篇
  1971年   2226篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
51.
Communication network design is becoming increasingly complex, involving making networks more usable, affordable, and reliable. To help with this, we have proposed an expert network designer (END) for configuring, modeling, simulating, and evaluating large structured computer networks, employing artificial intelligence, knowledge representation, and network simulation tools. We present a neural network/knowledge acquisition machine-learning approach to improve the END's efficiency in solving the network design problem and to extend its scope to acquire new networking technologies, learn new network design techniques, and update the specifications of existing technologies  相似文献   
52.
A comprehensive survey of photosensitivity in silica glasses and optical fiber is reviewed. Recent work on understanding the mechanisms contributing to germanium or aluminum doped fiber photosensitivity is discussed within the framework of photoelastic densification models  相似文献   
53.
Two novel configurations for digitally tunable optical filters based on arrayed-waveguide grating (AWG) multiplexers are described in detail with emphasis on the connection of the AWG multiplexer and optical switches. Performance comparisons show that conventional configurations are disadvantaged by the switch size required and loss imbalance among the optical frequency-division-multiplexed (FDM) channels; the proposed configurations require only O(√(N)) switch elements to select one of N FDM channels, and the loss imbalance is lower by up to 75% in decibel  相似文献   
54.
A new lateral MOS-gated thyristor, called the Base-Current-Controlled Thyristor, is described. This device is designed so that most holes at the on-stage reach the P base through the floating P+ region adjacent to the P base and the on-state MOSFET. At the turn-off stage, the interruption of the hole current to the P base due to switching off the above MOSFET occurs simultaneously with the conventional turn-off operation. The concept of this device is verified experimentally by using the fabricated lateral device with the external MOSFET. This device exhibits a better trade-off relation between the on-state voltage and the turn-off time compared uith the conventional MOS-gated thyristor  相似文献   
55.
A novel monitoring method for plasma-charging damage is proposed. This method performs a quick and accurate evaluation using antenna PMOSFET. It was found that not only hot-carrier (HC) lifetime but transistor parameters such as initial gate current and substrate current were changed according to the degree of plasma-charging damage. However, the present work suggests that monitoring the shift of drain current after a few seconds of HC stress is a more accurate method to indicate plasma-charging damage. The monitoring method using the present test structure is demonstrated to be useful for realizing highly reliable devices  相似文献   
56.
The physical widths of reference features incorporated into electrical linewidth test structures patterned in films of monocrystalline silicon have been determined from Kelvin voltage measurements. The films in which the test structures are patterned are electrically insulated from the bulk-silicon substrate by a layer of silicon dioxide provided by SIMOX (Separation by the IMplantation of OXygen) processing. The motivation is to facilitate the development of linewidth reference materials for critical-dimension (CD) metrology-instrument calibration. The selection of the (110) orientation of the starting silicon and the orientation of the structures' features relative to the crystal lattice enable a lattice-plane-selective etch to generate reference-feature properties of rectangular cross section and atomically planar sidewalls. These properties are highly desirable for CD applications in which feature widths are certified with nanometer-level uncertainty for use by a diverse range of CD instruments. End applications include the development and calibration of new generations of CD instruments directed at controlling processes for manufacturing devices having sub-quarter-micrometer features  相似文献   
57.
A new commercially available diode model is described. This unified model is capable of simulating the widest range of diode technologies of any presently available. The emphasis of this paper is on describing the model's extensive features and flexibility in the different domains of operation and is of particular interest in power applications  相似文献   
58.
59.
60.
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