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   636876篇
  免费   8506篇
  国内免费   1915篇
电工技术   12046篇
综合类   878篇
化学工业   95794篇
金属工艺   21923篇
机械仪表   18054篇
建筑科学   17331篇
矿业工程   1577篇
能源动力   17314篇
轻工业   63681篇
水利工程   5153篇
石油天然气   5162篇
武器工业   21篇
无线电   81519篇
一般工业技术   117915篇
冶金工业   120597篇
原子能技术   9433篇
自动化技术   58899篇
  2021年   4445篇
  2019年   4102篇
  2018年   6696篇
  2017年   6601篇
  2016年   6935篇
  2015年   5405篇
  2014年   8998篇
  2013年   29889篇
  2012年   15507篇
  2011年   22030篇
  2010年   17091篇
  2009年   19456篇
  2008年   20720篇
  2007年   20865篇
  2006年   18681篇
  2005年   17300篇
  2004年   16838篇
  2003年   16406篇
  2002年   15898篇
  2001年   16055篇
  2000年   15115篇
  1999年   16027篇
  1998年   37335篇
  1997年   27081篇
  1996年   21344篇
  1995年   16603篇
  1994年   14952篇
  1993年   14345篇
  1992年   10715篇
  1991年   10296篇
  1990年   9833篇
  1989年   9482篇
  1988年   9133篇
  1987年   7674篇
  1986年   7763篇
  1985年   9275篇
  1984年   8559篇
  1983年   7729篇
  1982年   7129篇
  1981年   7197篇
  1980年   6756篇
  1979年   6522篇
  1978年   6099篇
  1977年   7416篇
  1976年   9898篇
  1975年   5228篇
  1974年   5004篇
  1973年   4924篇
  1972年   3972篇
  1971年   3489篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
111.
Many current implementations of protocols such as the Transmission Control Protocol/Internet Protocol (TCP/IP) are inefficient because data are often accessed more frequently than necessary. Three techniques that reduce the need for memory bandwidth are proposed. The techniques are copy-on-write, page remapping, and single-copy. Afterburner, a network-independent card that provides the services that are necessary for a single-copy protocol stack, is described. The card has 1 MByte of local buffers and provides a simple interface to a variety of network link adapters, including HIPPI and asynchronous transfer mode (ATM). Afterburner can support transfers to and from the link adapter card at rates up to 1 Gbit/s. An implementation of TCP/IP that uses the features provided by Afterburner to reduce the movement of data to a single copy is discussed. Measurements of the end-to-end performance of Afterburner and the single-copy implementation of TCP/IP are presented  相似文献   
112.
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   
113.
114.
Functional Properties and Food Applications of Rapeseed Protein Concentrate   总被引:1,自引:0,他引:1  
Rapeseed protein concentrate (RC), prepared with 2% hexameta-phosphate, was tested for its functionality and performance in some foods. The RC had good nitrogen solubility, fat absorption, emulsification, and whipping capacities but poor water absorption and gelling properties. It increased the emulsion stability, and protein but lowered the fat content of wieners. It also increased the cooking yield, reduced the shrinkage and tenderized meat patties. Results were similar to soybean isolate except for the poorer color and flavor. The cooking yield of RC supplemented wieners was less than the all-meat control and soybean-supplemented wieners. A 9% RC dispersion mixed with an equal volume of eggwhite produced a meringue of comparable stability and texture to that of eggwhite alone.  相似文献   
115.
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   
116.
J. Perahia comments on the paper by J. S. Hsu (see ibid., vol.16, p.192-7, 2001) and expands on the case of a two stator three phase squirrel cage induction machine where one stator housing is stationary and other stator housing is mounted on a worm gear assembly. The original author replies to the comments  相似文献   
117.
118.
An investigation into the effects of pressure (helium gas) on the isothermal fluid behavior includes: (1) the effect of pressure on the rate of melting and coking as evidenced by the rate constants k(melt) and k(coke); (2) the effect of pressure on the energies of activation of melting and coking; (3) the effects of pressure on the characteristic times; (4) the effects of pressure on the maximum isothermal fluidity. Results from the effects of pressure on k(melt) revealed that it was generally the high total sulfur, low nitrogen, low reactives/mineral matter ratio, medium rank coals which show the greatest increase in k(melt), whereas the highest rank coals show the least decrease in k(coke). The energies of activation of melting and coking were not significantly affected by pressure. The investigation also reveals increases or decreases in the respective times of softening, maximum fluidity, resolidification and total time of fluid behavior under isothermal pressurized conditions. There appears the possibility that these shifts may be rank dependent. Additionally, the lower rank coals show the largest relative increase in their fluidities when subjected to pressure. Empirical relationships were derived in order to quantitatively predict the maximum isothermal fluidity for most (fluid) coals at a given pressure.  相似文献   
119.
120.
This paper demonstrates the use of computer simulation for topological design and performance engineering of transparent wavelength-division multiplexing metropolitan-area networks. Engineering of these networks involves the study of various transport-layer impairments such as amplifier noise, component ripple, chirp/dispersion, optical crosstalk, waveform distortion due to filter concatenation, fiber nonlinearities, and polarization effects. A computer simulation methodology composed of three main simulation steps is derived and implemented. This methodology obtains performance estimations by applying efficient wavelength-domain simulations on the entire network topology, followed by time-/frequency-domain simulations on selected paths of the network and finally Q-budgeting on an identified worst case path. The above technique provides an efficient tool for topological design and network performance engineering. Accurate simulation models are presented for each of the performance impairments, and the computer simulation methodology is used for the design and engineering of a number of actual metro network architectures  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