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   310188篇
  免费   3569篇
  国内免费   1913篇
电工技术   6096篇
综合类   303篇
化学工业   45507篇
金属工艺   14050篇
机械仪表   9472篇
建筑科学   7725篇
矿业工程   965篇
能源动力   7911篇
轻工业   29547篇
水利工程   2619篇
石油天然气   3601篇
武器工业   44篇
无线电   37256篇
一般工业技术   59527篇
冶金工业   60895篇
原子能技术   6346篇
自动化技术   23806篇
  2021年   2398篇
  2019年   2151篇
  2018年   3791篇
  2017年   3691篇
  2016年   4111篇
  2015年   2796篇
  2014年   4610篇
  2013年   14050篇
  2012年   7587篇
  2011年   10306篇
  2010年   8440篇
  2009年   9335篇
  2008年   9886篇
  2007年   9939篇
  2006年   8971篇
  2005年   8216篇
  2004年   7869篇
  2003年   7819篇
  2002年   7750篇
  2001年   7827篇
  2000年   7265篇
  1999年   7774篇
  1998年   19580篇
  1997年   13755篇
  1996年   10587篇
  1995年   7965篇
  1994年   7027篇
  1993年   6904篇
  1992年   4937篇
  1991年   4933篇
  1990年   4565篇
  1989年   4455篇
  1988年   4283篇
  1987年   3710篇
  1986年   3655篇
  1985年   4249篇
  1984年   3757篇
  1983年   3430篇
  1982年   3144篇
  1981年   3203篇
  1980年   3034篇
  1979年   2858篇
  1978年   2797篇
  1977年   3515篇
  1976年   5016篇
  1975年   2450篇
  1974年   2316篇
  1973年   2281篇
  1972年   1904篇
  1971年   1725篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
Carey  D.H. 《Micro, IEEE》1993,13(2):19-27
The trends in high density interconnection (HDI) multichip module (MCM) techniques that have the potential to reduce interconnection cost and production time are described. The implementation in laminated dielectric (MCM-L) technology of a workstation processor core illustrates current substrate technology capabilities. The design, routing, layout and thermal management of the processor core are described. Thin-film deposited dielectric (MCM-D) technology is discussed as a cost-effective method for future interconnection applications  相似文献   
52.
Most divers and diving medicine specialists know that application of normobaric oxygen as first aid after a bubble disease incident is highly effective. However, as yet technical difficulties acted as a deterrent to using normobaric oxygen at the diving site. This can now be overcome by a newer technique. To be efficient, any therapy of bubble disease should follow three main principles: maximal partial pressure of inhaled oxygen (i.e. 100 kpa in normobaric, and 280 kpa in hyperbaric conditions); minimal partial pressure of inhaled nitrogen, which should ideally be near zero; immediate start of therapy, if possible at the diving site, but not later than 2 hours after the onset of the first symptoms. However, it has to be borne in mind that for an efficient normobaric oxygenation (100%), the standard apparatus design without oxygen reservoir is obsolete, for it offers at most 40% oxygen to the lungs. Currently the following technical approaches for an efficient normobaric oxygenation are available: open one-way systems with tightly fitting mask and oxygen reservoir bag (type Ambu or Leardal, etc.); open systems with on-demand regulation and tightly fitting mouth piece (type SCUBA, or Bird-respirator); closed systems with CO2 absorber (type oxygen rebreathing diving gear). The closed system is a genuine technical advance, because it needs 15 times less oxygen than open systems (about 90 liters oxygen for a 3-hours oxygenation run). Such an apparatus is thus of light weight, far less cumbersome, and nevertheless highly efficient. The therapy should start immediately at the site of the mishap and be maintained during the transport to the next HBO-unit (usually 3 to 6 hours).(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
53.
Given the enormous size of the genome and that there are potentially many other types of measurements we need to do to understand it, it has become necessary to pick and choose one's targets to measure because it is still impossible to evaluate the entire genome all at once. What has emerged is a need to have rapidly customizable microarrays. There are two dominant methods to accomplish custom microarray synthesis, Affymetrix-like microarrays manufactured using light projection rather than semiconductor-like masks used by Affymetrix to mass manufacture their GeneChip/sup TM/ arrays now, or the ink-jet printing method employed by Agilent. The manufacture of these custom Affymetrix-like microarrays can now be done on a digital optical chemistry (DOC) machine developed at the University of Texas Southwestern Medical Center, and this method offers much higher feature numbers and feature density than is possible with ink-jet printed arrays. On a microarray, each feature contains a single genetic measurement. The initial DOC prototype has been described in several publications, but that has now led to a second-generation machine. This machine reliably produces a number of arrays daily, has been deployed against a number of biomedical questions, is being used in new ways and has also led to a number of spin-off technologies.  相似文献   
54.
55.
56.
No generally accepted principles and guidelines currently exist to help engineers design local interaction mechanisms that result in a desired global behavior. However, several communities have developed ways of approaching this problem in the context of niched application areas. Because the ideas underlying these approaches are often obscured or underemphasized in technical papers, the authors review the role of self-organization in their work. They provide a better picture of the status of the emerging field of self-organizing systems or autonomic computing.  相似文献   
57.
58.
An all-optical multiplexing technique using wavelength division multiplexing (WDM)-time division multiplexing (TDM) conversion with an electroabsorption wavelength converter has been proposed and demonstrated. The effectiveness of this WDM-TDM conversion technique for various pulsewidth settings was experimentally investigated. The fluctuation of the signal performance, which was inevitably caused by the coherent crosstalk between adjacent pulses in the conventional optical time division multiplexing (OTDM) technique, were successfully suppressed, even in the case of wide pulse duration. High Q-factor performance has been maintained for a wide range of duty ration from 36% to 74%. By introducing this technique to the optical time division multiplexer, a highly stable and high-quality 40-Gb/s optical signal can be effectively produced without generating the short pulse or setting two tributaries at orthogonal polarization states, and without introducing high-speed electronics for signal multiplexing. The WDM-TDM conversion with an electroabsorption wavelength converter was extended to 60-Gb/s operation by using three 20-Gb/s tributaries. A clear eye opening was confirmed for a waveform after the WDM-TDM conversion of the 60-Gb/s signal  相似文献   
59.
A fast algorithm is proposed for estimating the auto- and cross-correlation functions of a large signal. The algorithm is based on the sectioning method by the fast Fourier transform. We determine the optimal length of the portion of data read from external memory into RAM which achieves Tmin—a minimum processing time. An estimate of Tmin is obtained.Translated from Kibernetika, No. 3, pp. 78–81, May–June, 1991.  相似文献   
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