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   125189篇
  免费   10744篇
  国内免费   5381篇
电工技术   7707篇
技术理论   7篇
综合类   8045篇
化学工业   21328篇
金属工艺   7041篇
机械仪表   7804篇
建筑科学   10336篇
矿业工程   3855篇
能源动力   3700篇
轻工业   8123篇
水利工程   2287篇
石油天然气   7790篇
武器工业   944篇
无线电   14080篇
一般工业技术   15052篇
冶金工业   5841篇
原子能技术   1377篇
自动化技术   15997篇
  2024年   634篇
  2023年   2244篇
  2022年   3912篇
  2021年   5408篇
  2020年   4084篇
  2019年   3396篇
  2018年   3674篇
  2017年   4196篇
  2016年   3578篇
  2015年   5034篇
  2014年   6105篇
  2013年   7190篇
  2012年   7888篇
  2011年   8484篇
  2010年   7402篇
  2009年   7008篇
  2008年   6799篇
  2007年   6406篇
  2006年   6694篇
  2005年   5768篇
  2004年   3930篇
  2003年   3444篇
  2002年   3219篇
  2001年   2913篇
  2000年   3078篇
  1999年   3343篇
  1998年   2756篇
  1997年   2364篇
  1996年   2166篇
  1995年   1890篇
  1994年   1518篇
  1993年   1082篇
  1992年   883篇
  1991年   697篇
  1990年   504篇
  1989年   449篇
  1988年   364篇
  1987年   251篇
  1986年   169篇
  1985年   102篇
  1984年   68篇
  1983年   49篇
  1982年   66篇
  1981年   39篇
  1980年   38篇
  1979年   13篇
  1978年   3篇
  1965年   3篇
  1959年   7篇
  1951年   2篇
排序方式: 共有10000条查询结果,搜索用时 10 毫秒
991.
徐胜波  王新梅 《电子学报》1998,26(1):102-104
本文提出了一种构造具有纠错能力的认证会议密钥分配方案和安全广播 有效方法,该方法不是采用传统的加密技术而是利用幻民错码技术,由该方法构造的两个方案不仅安全,而且可以提高通信的可靠性。  相似文献   
992.
In the present study, we have performed electrical characterization of oxides deposited via rapid thermal chemical vapor deposition using SiH4 and N2O. We have investigated the effect of temperature, pressure, and SiH4 to N2O ratio on the electrical and material properties of as-deposited films. We have found that as-deposited oxides deposited at low temperatures, low pressures, and with a low silane to nitrous oxide ratio of ~0.5% give good material and electrical properties. The as-deposited films are stoichiometric in nature and have high deposition rates. As-deposited films had very low Dit values, high breakdown fields, and excellent subthreshold swing. The leakage currents and metal oxide semiconductor field effect transistor current drive, although lower than thermal oxides, were found to be quite acceptable. We have also investigated the thickness dependence of the films and found that as the film thickness is reduced below 50Å, the reliability improves for all oxides including the silicon-rich deposited oxides.  相似文献   
993.
A new millimeter-wave omnidirectional dielectric rod metallic grating antenna is investigated theoretically and experimentally, in this paper. The radiation characteristics of the antenna are carefully investigated by a rigorous formulation for the TE01-mode and TM01-mode excitation in the Ka-band frequency range. Based on the analysis, an omnidirectional antenna excited by the TE01 mode is designed and measured. The measured results are compared with theoretical predictions and good agreement is found. Extensive numerical results are given to establish some useful guidelines for the design of the omnidirectional antenna  相似文献   
994.
Dynamic oxide voltage relaxation spectroscopy   总被引:3,自引:0,他引:3  
A new method for trap characterization of oxidized silicon is described. The Dynamic Oxide Voltage Relaxation Spectroscopy (DOVRS) is an improved version of the formerly proposed Oxide Voltage Relaxation Spectroscopy (OVRS) technique which applies a periodic long duration constant current for tunneling injection. It has been demonstrated that the new technique can be used not only to separate and identify the oxide trap from interface trap, but also to separate and determine the centroid from the oxide trap density generated in the MOS system by the tunneling current stress. In the pulse constant current mode, the OVRS measurement can be completed instead of using the double current-voltage technique. Thus the new method results in more accurate and quicker measurements of the oxide trap centroid. Analytical expressions for computing the paramaters of the interface and oxide traps are derived. The effect of the channel carrier mobility on the spectroscopy is also considered. Two types of oxide and two types of interface traps were observed at a pulse constant Fowler-Nordheim current stress by the new method of DOVRS  相似文献   
995.
Efficient iterative design method for cosine-modulated QMF banks   总被引:3,自引:0,他引:3  
An iterative algorithm for the design of multichannel cosine-modulated quadrature mirror-image filter (QMF) banks with near-perfect reconstruction is proposed. The objective function is formulated as a quadratic function in each step whose minimum point can be obtained using a closed-form solution. This approach has high design efficiency and leads to filter banks with high stopband attenuation and low aliasing and amplitude distortions. The proposed approach is then extended to the design of multichannel cosine-modulated QMF banks with low reconstruction delays, which are often required, especially in real-time applications. Several design examples are included to demonstrate the proposed algorithms, and some comparisons are made with existing designs  相似文献   
996.
提出一种用计算机设计制作的双闪耀光栅,是在闪耀光栅和双频光栅基础上发展起来的一种新型光学元件,是由微闪耀光栅列阵组成的、兼有闪耀光栅和双频光栅的优良特性。  相似文献   
997.
介绍应用CCD的机载激光报警仪的原理、结构及其主要技术指标,讨论了其中的技术关键及解决方法。  相似文献   
998.
本文证明了当m>4时(2m,2,m)非线性等重码不是最佳检错码。  相似文献   
999.
We assess the state-of-the-art technology in massively parallel processors (MPPs) and their variations in different architectural platforms. Architectural and programming issues are identified in using MPPs for time-critical applications such as adaptive radar signal processing. We review the enabling technologies. These include high-performance CPU chips and system interconnects, distributed memory architectures, and various latency hiding mechanisms. We characterize the concept of scalability in three areas: resources, applications, and technology. Scalable performance attributes are analytically defined. Then we compare MPPs with symmetric multiprocessors (SMPs) and clusters of workstations (COWs). The purpose is to reveal their capabilities, limits, and effectiveness in signal processing. We evaluate the IBM SP2 at MHPCC, the Intel Paragon at SDSC, the Gray T3D at Gray Eagan Center, and the Gray T3E and ASCI TeraFLOP system proposed by Intel. On the software and programming side, we evaluate existing parallel programming environments, including the models, languages, compilers, software tools, and operating systems. Some guidelines for program parallelization are provided. We examine data-parallel, shared-variable, message-passing, and implicit programming models. Communication functions and their performance overhead are discussed. Available software tools and communication libraries are also introduced  相似文献   
1000.
秸秆直燃生物质电厂动态发电成本分析   总被引:5,自引:0,他引:5  
结合火电厂成本研究方法,以月为单位建立生物质发电动态成本分析模型,根据机组容量与负荷特性分摊年固定成本,以生物质发电系统为研究对象计算不同秸秆价所对应发电成本的最大值和最小值,并对发电成本进行了敏感性分析.结果表明:燃料费的变化对生物质电厂发电成本的影响最大,折旧费和厂用电费的影响其次,燃料价格降低10%和20%时,发电成本分别降低5.09%和10.17%.  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