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   6459篇
  免费   251篇
  国内免费   44篇
电工技术   128篇
综合类   24篇
化学工业   781篇
金属工艺   110篇
机械仪表   198篇
建筑科学   345篇
矿业工程   3篇
能源动力   148篇
轻工业   297篇
水利工程   23篇
石油天然气   25篇
武器工业   3篇
无线电   1472篇
一般工业技术   1022篇
冶金工业   1118篇
原子能技术   33篇
自动化技术   1024篇
  2023年   37篇
  2022年   40篇
  2021年   88篇
  2020年   58篇
  2019年   70篇
  2018年   106篇
  2017年   81篇
  2016年   135篇
  2015年   112篇
  2014年   134篇
  2013年   319篇
  2012年   305篇
  2011年   322篇
  2010年   238篇
  2009年   297篇
  2008年   328篇
  2007年   317篇
  2006年   305篇
  2005年   253篇
  2004年   205篇
  2003年   213篇
  2002年   158篇
  2001年   171篇
  2000年   167篇
  1999年   189篇
  1998年   474篇
  1997年   273篇
  1996年   196篇
  1995年   173篇
  1994年   106篇
  1993年   126篇
  1992年   75篇
  1991年   61篇
  1990年   52篇
  1989年   48篇
  1988年   47篇
  1987年   41篇
  1986年   39篇
  1985年   60篇
  1984年   27篇
  1983年   24篇
  1982年   37篇
  1981年   34篇
  1980年   28篇
  1979年   24篇
  1978年   17篇
  1977年   22篇
  1976年   44篇
  1975年   17篇
  1973年   19篇
排序方式: 共有6754条查询结果,搜索用时 15 毫秒
71.
An implementation of the Pentium microprocessor architecture in 0.6 μm BiCMOS technology is described. Power dissipation is reduced and performance is enhanced over the previous generation. Processor features, implementation technology, and circuit techniques are discussed. An internal clock rate of 150 MHz is achieved at 3.7 V and -55°C  相似文献   
72.
This paper examines the detrimental effects of excess majority carriers and photons induced by impact ionization on the operation of neighboring pn junctions, bipolar transistors, MOS transistors, and circuits. The experimental results show that in addition to an increase in the substrate surface potential due to the excess majority carriers, photons can lower the barrier of a pn junction and, as a consequence, shift the Gummel plot of an npn bipolar transistor. As for the neighboring circuits, an example in which the speed of an NMOS ring oscillator is retarded by impact ionization in a neighboring NMOS transistor is presented  相似文献   
73.
Parasitic bipolar gain in fully depleted n-channel SOI MOSFET's   总被引:3,自引:0,他引:3  
Fully depleted SOI MOSFET's include an inherent parasitic lateral bipolar structure with a floating base. We present here the first complete physically based explanation of the bipolar gain mechanism, and its dependence on bias and technological parameters. A simple, one-dimensional physical model, with no fitting parameters, is constructed, and is shown to agree well with simulations and measurements performed on a new type of SOI MOSFET structure. It is shown that parameters which affect the gain, such as SOI layer thickness, body doping concentration and gate and drain voltages, do so primarily by affecting the concentration of holes in the body region. Thus, current gain falls dramatically with increasing drain voltage due to the associated impact ionization driven increase in the hole concentration. Gummel plots of this parasitic bipolar indicate an apparent ideality factor of 0.5 for the hole current, due to the body hole concentration's dependence on drain voltage  相似文献   
74.
High dielectric constant (high-k) polymer composites are of great interest for embedded capacitor applications. Previously, we demonstrated that epoxy—aluminum composites are promising for embedded capacitor applications, because they have a high dielectric constant and a low dielectric loss due to the core—shell structure of the self-passivated aluminum particles. In this work, to further understand the dielectric behavior of aluminum composites, lower-loss polymers such as silicone, polyimide, polynorbornene, and benzocyclobutene were explored as matrices for the aluminum composites. It is found that the polymer matrices can significantly change the dielectric properties of the aluminum composites. A polymer matrix with a lower dielectric constant generally results in a lower dielectric constant of its aluminum composites. In this regard, polymer—aluminum composites have a similar dielectric characteristic as polymer—ceramic composites. Thermomechanical properties of aluminum composites were characterized by a thermomechanical analyzer.  相似文献   
75.
Fuzzy rule-based systems have been very popular in many engineering applications. In mineral engineering, fuzzy rules are normally constructed using some fuzzy rule extraction techniques to establish the determination model in predicting the d50c of hydrocyclones. However, when generating fuzzy rules from the available information, it may result in a sparse fuzzy rule base. The use of more than one input variable is also common in hydrocyclone data analysis. This paper examines the application of fuzzy interpolation to resolve the problems using sparse fuzzy rule bases, and to perform analysis of fuzzy interpolation in multidimensional input spaces.  相似文献   
76.
Generally, isotropically conductive adhesive formulations include epoxy resin as the polymeric matrix. Although epoxy has superior adhesion capability, its drawbacks include the tendency to absorb moisture and lack of reworkability (thermosetting polymer). In this study, a thermoplastic polymer with low moisture absorption (0.28 wt%), called polyarylene ether (PAE2), is used in isotropically conductive adhesive (ICA) formulation. Previous research work by Lu et al. showed that the moisture absorbed into epoxy caused galvanic corrosion, which result in the formation of metal oxide . By using a polymer with low moisture absorption, the amount of water present in ICA will be small, and the corrosion rate and formation of metal oxide can be reduced. However, previous measurements of contact resistance stability of PAE2-based ICA showed that they are not stable on all surface finishes. It was determined that for thermoplastic-based ICA, poor adhesion was the main mechanism for unstable contact resistance. Two methods of adhesion improvement will be evaluated in this work. The first is to use coupling agents and the second is to blend the thermoplastic with epoxy. Both methods showed promise in improving the contact resistance stability of polyarylene ether based ICA.  相似文献   
77.
Real-time palmprint acquisition system design   总被引:1,自引:0,他引:1  
Capturing high quality palmprint images in a very short time period is a fundamental step in palmprint research. While a palmprint scanner capable of this function is especially important for developing a real-time online palmprint identification system, limited research effort has been put into designing and implementing palmprint acquisition systems. A novel palmprint acquisition system is presented, which is designed for various civilian applications such as access control, ATM, etc. The novel contactless design on the user interface prevents the distortion of the palm skin introduced by the traditional glass plate of a palm scanner. The system is designed to have the best performance at reasonable price. It has a resolution of 150 dpi that is able to obtain palmprint features, including the principal lines, wrinkles and ridge texture. The proposed system provides an important step for implementing a personal identification system using palmprint. Over 9,400 palmprint images were collected by the proposed system. An online palmprint identification system was then developed based on the proposed acquisition system.  相似文献   
78.
Laboratory-reared and wild adults of the melon fly,Dacus cucurbitae Coquillett, were tested for response to cue-lure at various ages. Virgin laboratory (4, 6, 8, 10, 12, and 14 days old) and wild (10, 12, 14, 16, 18, 20, and 22 days old) flies were released into outdoor field cages and trapped from 0800 until 1600 hr. Response of males to cue-lure increased with age and corresponded with sexual maturity for each strain. Females of both strains were relatively nonresponsive to cue-lure. Failure to eradicate in past male annihilation programs againstD. cucurbitae may be explained in part by the fact that only older males, which may have already mated with gravid females, respond to cue-lure.  相似文献   
79.
An encryption system with discretized skew tent map has been proposed recently by N. Masuda . However, there is a fundamental weakness with this chaotic cryptographic scheme. In this paper, a chosen plaintext attack requiring only two plaintexts is proposed. An improved version of this attack that narrows the key space need to be searched is also suggested. The test results demonstrate that this encryption cryptosystem is easily broken under the proposed chosen plaintext attack.  相似文献   
80.
Po  L.M. Tan  W.T. Wong  W.B. 《Electronics letters》1995,31(23):1988-1990
A new colour quantisation and quadtree based image compression scheme is proposed. The features of the new scheme are that colour palette ordering and requantisation of the decoded image for palette-based monitor displays are not required. Thus, fast decoding and displaying can be achieved  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