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   245194篇
  免费   3026篇
  国内免费   1241篇
电工技术   4854篇
综合类   287篇
化学工业   35925篇
金属工艺   10915篇
机械仪表   7093篇
建筑科学   6366篇
矿业工程   485篇
能源动力   6318篇
轻工业   24354篇
水利工程   1841篇
石油天然气   1337篇
武器工业   3篇
无线电   31133篇
一般工业技术   45181篇
冶金工业   50219篇
原子能技术   3878篇
自动化技术   19272篇
  2021年   1629篇
  2019年   1462篇
  2018年   2364篇
  2017年   2254篇
  2016年   2494篇
  2015年   1964篇
  2014年   3228篇
  2013年   10862篇
  2012年   5546篇
  2011年   7891篇
  2010年   6385篇
  2009年   7037篇
  2008年   7627篇
  2007年   7720篇
  2006年   7093篇
  2005年   6568篇
  2004年   6287篇
  2003年   6285篇
  2002年   6281篇
  2001年   6402篇
  2000年   5827篇
  1999年   6444篇
  1998年   16587篇
  1997年   11625篇
  1996年   8965篇
  1995年   6716篇
  1994年   5922篇
  1993年   5742篇
  1992年   4071篇
  1991年   4007篇
  1990年   3597篇
  1989年   3519篇
  1988年   3449篇
  1987年   2918篇
  1986年   2849篇
  1985年   3423篇
  1984年   3067篇
  1983年   2750篇
  1982年   2556篇
  1981年   2580篇
  1980年   2441篇
  1979年   2280篇
  1978年   2255篇
  1977年   2820篇
  1976年   4181篇
  1975年   1908篇
  1974年   1816篇
  1973年   1791篇
  1972年   1462篇
  1971年   1323篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
71.
We have analyzed degradation of N-channel thin-film-transistor (TFT) under dynamic stress using a pico-second time-resolved emission microscope. We have successfully detected emission at pulse fall edge for the first time. Emission intensity increased with the decrease of pulse fall time. As the degradation depended on the pulse fall time, this dependence clearly illustrates that hot electrons are the dominant cause of the degradation under dynamic stress. Based on these dependences, we proposed a model considering electron traps in the poly-Si.  相似文献   
72.
Li  H. Rein  H.-M. Schwerd  M. 《Electronics letters》2003,39(18):1326-1327
VCOs fully integrated in an SiGe preproduction technology are presented. By cutting interconnection lines a wide frequency range can be covered, up to 88.4 GHz. Special effort has been made to meet the demands for 77 GHz automotive radar. In the corresponding tuning range from 75.3 to 79.6 GHz, an output power of about 11 dBm (with -2.2 dBm potential measurement uncertainty) was achieved for each of the two complementary outputs, i.e. in total 14 dBm. The phase noise is about -94 dBc/Hz at 1 MHz offset frequency.  相似文献   
73.
On the synergy between electrical and photonic switching   总被引:1,自引:0,他引:1  
This article focuses on the values of electrical switching vs. photonic switching in the context of telecom transport networks. In particular, we show that the requirement of providing agility at the optical layer in the face of traffic forecast uncertainties is served better through photonic switching. On the other hand, some of the network-level functions, such as fast protection, subwavelength aggregation, and flexible client connectivity, require electrical switching. We further argue that additional values are achieved with hybrid photonic and electrical switching, which do not exist when either of these options is used in isolation.  相似文献   
74.
In this letter, bandpass filters with one or two tunable transmission zeros are proposed. The reconfigurable transmission zeros are implemented through varactors in combination with tapped quarter-wavelength stubs. Based on mixed mode simulations including EM simulation and circuit simulation, the proposed filters were designed and fabricated on low-cost FR4 board. The measurement results verified the design concepts.  相似文献   
75.
Towards intelligent dressing   总被引:1,自引:0,他引:1  
The aim of this article is to state the principles of an intelligent monitoring and control system for the grinding machine, comprising the dressing process as well as grinding stability.  相似文献   
76.
77.
This paper presents a simple alternative for an electronic ballast operating in self-sustained oscillating mode with dimming capability for fluorescent lamps. A simple modification in one of the gate drivers side circuit allows the lamp to dim without compromising the simplicity, reliability, and low cost which characterize the self-oscillating electronic ballast (SOEB). A qualitative analysis is presented to explain the behavior of the proposed self-oscillating electronic ballast with dimming feature. In addition, the stability and the key equations for the design are derived using the extended Nyquist criterion and describing function method. Experimental results from two 40-W electronic ballasts are presented to demonstrate the performance and to validate the analysis carried out.  相似文献   
78.
Over the last five years, many activities have focused on the unexploited field of carrying out reactions on small scales. Due to the rapid development of new components, this paper deals with recent developments only in a compressed form. An important point is the analysis of possible plant concepts for microreactors and whether these are a sensible option. Due to the enormous difference in size between the microchannels and the fluid periphera of possible components this is not just a technical question. It touches on the microtechnology concept as a whole. The direction in which the field should be developed and which measures can be taken to influence its development are questions that are addressed here with respect to the big industrial interest in microreactors.  相似文献   
79.
80.
The damage imposed on SiO x deposited nylon 6 films as a result of abrasion with a cotton cloth and Gelboflex testing was examined by evaluating the rate at which copper plates, which were enveloped by the damaged films, were corroded by H2S. Abrasion with a cotton cloth caused some micro-cracking of the SiO x layer and the permeation rate of H2S approached that of the uncoated nylon 6 film. Damage to the SiO x layer by twisting and crushing progressed gradually with the number of Gelboflex test cycles and correspondingly the corrosion rate of the copper plates increased. Comparison of the corrosion rates of the copper plates kept in the pouches made of various commercial films with those obtained for the damaged SiO x deposited nylon 6 films showed a clear relationship between the H2 permeation rate of the films and the corrosion rate of the copper plates by H2S.  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