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   2783篇
  免费   149篇
  国内免费   13篇
电工技术   40篇
综合类   8篇
化学工业   574篇
金属工艺   80篇
机械仪表   169篇
建筑科学   72篇
矿业工程   5篇
能源动力   113篇
轻工业   204篇
水利工程   28篇
石油天然气   5篇
武器工业   1篇
无线电   437篇
一般工业技术   549篇
冶金工业   174篇
原子能技术   32篇
自动化技术   454篇
  2024年   2篇
  2023年   57篇
  2022年   82篇
  2021年   149篇
  2020年   100篇
  2019年   132篇
  2018年   102篇
  2017年   97篇
  2016年   126篇
  2015年   84篇
  2014年   152篇
  2013年   203篇
  2012年   185篇
  2011年   212篇
  2010年   133篇
  2009年   135篇
  2008年   126篇
  2007年   127篇
  2006年   97篇
  2005年   62篇
  2004年   64篇
  2003年   55篇
  2002年   30篇
  2001年   47篇
  2000年   33篇
  1999年   38篇
  1998年   63篇
  1997年   44篇
  1996年   35篇
  1995年   19篇
  1994年   18篇
  1993年   22篇
  1992年   21篇
  1991年   6篇
  1990年   9篇
  1989年   10篇
  1988年   7篇
  1987年   7篇
  1986年   4篇
  1985年   7篇
  1984年   2篇
  1983年   6篇
  1982年   2篇
  1981年   5篇
  1979年   2篇
  1977年   7篇
  1976年   3篇
  1975年   3篇
  1974年   2篇
  1973年   6篇
排序方式: 共有2945条查询结果,搜索用时 9 毫秒
31.
The preparation of uniform large‐area highly crystalline organic semiconductor thin films that show outstanding carrier mobilities remains a challenge in the field of organic electronics, including organic field‐effect transistors. Quantitative control over the drying speed during dip‐coating permits optimization of the organic semiconductor film formation, although the kinetics of crystallization at the air–solution–substrate contact line are still not well understood. Here, we report the facile one‐step growth of self‐aligning, highly crystalline soluble acene crystal arrays that exhibit excellent field‐effect mobilities (up to 1.5 cm V?1 s?1) via an optimized dip‐coating process. We discover that optimized acene crystals grew at a particular substrate lifting‐rate in the presence of low boiling point solvents, such as dichloromethane (b.p. of 40.0 °C) or chloroform (b.p. of 60.4 °C). Variable‐temperature dip‐coating experiments using various solvents and lift rates are performed to elucidate the crystallization behavior. This bottom‐up study of soluble acene crystal growth during dip‐coating provides conditions under which one may obtain uniform organic semiconductor crystal arrays with high crystallinity and mobilities over large substrate areas, regardless of the substrate geometry (wafer substrates or cylinder‐shaped substrates).  相似文献   
32.
33.
34.
This paper presents a novel ESD strategy for non-volatile memory (NVM) programming pin in a 0.13um/30V technology. Suggested scheme can provide not only a major current discharge path to protect the internal circuit from ESD damage but also a voltage clamping function to prevent the soft error of programmed data during the ESD event. It has been validated by TLP experiments and TCAD simulation.  相似文献   
35.
Carbon incorporation into GaAs epilayers has been performed by atmospheric pressure metalorganic chemical vapor deposition using CBr4. The electrical properties of CBr4-doped GaAs epilayers grown on the GaAs substrates with various surface crystallographic orientations between (100) and (111)A were investigated. The electrical properties of the epilayers showed a strong crystallographic orientation dependence. On increasing the surface offset angle, the hole concentration of CBr4-doped GaAs epilayers rapidly decreased with a hump at (311)A. The lower hole concentration at the high offset angle can be explained by its higher desorption rate than that of the (100) surface. This hole concentration dependence on the offset angle was not changed in spite of the growth temperature and the V/III ratio variation given in this work. The above behaviors indicate that the surface kinetics plays an important role in the C incorporation into the non-planar GaAs epilayers.  相似文献   
36.
A new design method for complex-valued two-channel finite impulse response (FIR) filter banks with both orthogonality and symmetry properties is developed. Based on a novel linear matrix inequality (LMI) characterization of trigonometric curves, the optimal design of perfect-reconstruction filter banks is cast into a semidefinite programming (SDP) problem. The dimension of the resulting SDP problem is further reduced by exploiting convex duality. Consequently, the globally optimal solution can be found for any practical filter length and desired regularity order.  相似文献   
37.
Three-dimensional imaging methods, based on parallaxes as their depth cues, can be classified into the stereoscopic providing binocular parallax only, and multiview providing both binocular and motion parallaxes. In these methods, the parallaxes are provided by creating a viewing zone with use of either a special optical eyeglasses or a special optical plate as their viewing zone-forming optics. For the stereoscopic image generations, either the eyeglasses or the optical plate can be employed, but for the multiview the optical plate or the eyeglasses with a tracking device. The stereoscopic image pair and the multiview images are presented either simultaneously or as a time sequence with use of projectors or display panels. For the case of multiview images, they can also be presented as two images at a time according to the viewer's movements. The presence of the viewing zone-forming optics often causes undesirable problems, such as appearance of moire/spl acute/ fringes, image quality deterioration, depth reversion, limiting viewing regions, low image brightness, image blurring, and inconveniences of wearing.  相似文献   
38.
An optimal constant-composition or constant-weight code of weight w has linear size if and only if its distance d is at least 2w-1. When d ? 2w, the determination of the exact size of such a constant-composition or constant-weight code is trivial, but the case of d=2w-1 has been solved previously only for binary and ternary constant-composition and constant-weight codes, and for some sporadic instances. This paper provides a construction for quasicyclic optimal constant-composition and constant-weight codes of weight w and distance 2w-1 based on a new generalization of difference triangle sets. As a result, the sizes of optimal constant-composition codes and optimal constant-weight codes of weight w and distance 2w-1 are determined for all such codes of sufficiently large lengths. This solves an open problem of Etzion. The sizes of optimal constant-composition codes of weight w and distance 2w-1 are also determined for all w ? 6, except in two cases.  相似文献   
39.
New families of protocol, based on communication over human-based side channels, permit secure pairing or group formation in ways such that no party has to prove its name. Rather, individuals are able to hook up devices in their possession to others that they can identify by context. We examine a model in which, to prove his or her identity to a party, the user first uses one of these “human-interactive security protocols” or HISPs to connect to it. Thus, when authenticating A to B, A first authenticates a channel she has to B: the reverse direction. This can be characterised as bootstrapping a secure connection using human trust. This provides new challenges to the formal modelling of trust and authentication.  相似文献   
40.
This paper presents a comprehensive cross-layer framework on the performance of transmission control protocol (TCP) over a free-space optical (FSO) link, which employs automatic repeat request (ARQ) and adaptive modulation and coding (AMC) schemes. Not similar to conventional works in the literature of FSO, we conduct a Markov error model to accurately capture effects of burst errors caused by atmospheric turbulence on cross-layer operations. From the framework, we quantify the impacts of different parameters/settings of ARQ, AMC, and the FSO link on TCP throughput performance. We also discuss several optimization aspects for TCP performance.  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