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   567085篇
  免费   6231篇
  国内免费   1004篇
电工技术   10509篇
综合类   466篇
化学工业   90071篇
金属工艺   23344篇
机械仪表   18509篇
建筑科学   12540篇
矿业工程   4312篇
能源动力   14435篇
轻工业   45798篇
水利工程   6943篇
石油天然气   14961篇
武器工业   39篇
无线电   60292篇
一般工业技术   116270篇
冶金工业   95706篇
原子能技术   14681篇
自动化技术   45444篇
  2021年   5482篇
  2019年   5271篇
  2018年   9202篇
  2017年   9411篇
  2016年   9833篇
  2015年   6027篇
  2014年   10244篇
  2013年   26114篇
  2012年   15780篇
  2011年   21100篇
  2010年   16981篇
  2009年   18823篇
  2008年   19080篇
  2007年   18774篇
  2006年   16296篇
  2005年   14748篇
  2004年   14007篇
  2003年   13694篇
  2002年   13252篇
  2001年   12859篇
  2000年   12334篇
  1999年   12017篇
  1998年   27696篇
  1997年   20055篇
  1996年   15644篇
  1995年   12018篇
  1994年   10873篇
  1993年   10621篇
  1992年   8334篇
  1991年   8106篇
  1990年   7993篇
  1989年   7766篇
  1988年   7481篇
  1987年   6755篇
  1986年   6540篇
  1985年   7394篇
  1984年   6706篇
  1983年   6443篇
  1982年   5781篇
  1981年   5899篇
  1980年   5638篇
  1979年   5736篇
  1978年   5666篇
  1977年   6182篇
  1976年   7697篇
  1975年   5111篇
  1974年   4903篇
  1973年   4981篇
  1972年   4282篇
  1971年   4041篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
Carboxyl-terminated butadiene-acrylonitrile-rubber decreases modulus and yield stress of the studied epoxy but increases fracture toughness. The addition of glass bead compensates for the loss in modulus but has little effect on yield stress. However, it significantly contributes to the fracture toughness by providing additional mechanisms for toughening of both the unmodified and rubber-modified epoxy. For the toughened epoxies studied, fracture surfaces gave only limited information on fracture mechanisms since significant energy absorption also occurs in the material below the fracture surface. Suggestions for suitable material compositions for fiber composite matrices are given.  相似文献   
72.
The technological process of cold forging applied for the first time in the production of the casing of the internal joint with races is described. The process operations of cold forging and the annealing and carburizing regimes for this part me described.  相似文献   
73.
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   
74.
Translated from Atomnaya Énergiya, Vol. 66, No. 6, pp. 423–424, June, 1989.  相似文献   
75.
Translated from Atomnaya Énergiya, Vol. 67, No. 3, pp. 215–216, September, 1989.  相似文献   
76.
An apparent decrease in total phosphorus concentrations of approximately 4.l μgP/L has been reported recently for the spring values of 1977 and 1978 in Lake Ontario. Investigation of the loading reduction for this period independent of sedimentation factors can account for only 10% of the change. The results indicate that changes in the sedimentation rate of total phosphorus during this period offer an explanation for the majority of the change in concentration.  相似文献   
77.
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   
78.
79.
80.
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