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   279020篇
  免费   19070篇
  国内免费   10986篇
电工技术   15159篇
技术理论   14篇
综合类   14720篇
化学工业   43008篇
金属工艺   15488篇
机械仪表   15538篇
建筑科学   17135篇
矿业工程   6652篇
能源动力   7686篇
轻工业   20669篇
水利工程   5098篇
石油天然气   13157篇
武器工业   2085篇
无线电   31438篇
一般工业技术   39652篇
冶金工业   22545篇
原子能技术   4949篇
自动化技术   34083篇
  2024年   920篇
  2023年   3178篇
  2022年   6283篇
  2021年   8941篇
  2020年   6842篇
  2019年   5794篇
  2018年   7171篇
  2017年   7885篇
  2016年   7777篇
  2015年   8987篇
  2014年   11668篇
  2013年   15495篇
  2012年   16290篇
  2011年   17799篇
  2010年   15551篇
  2009年   15239篇
  2008年   14960篇
  2007年   14272篇
  2006年   13686篇
  2005年   11578篇
  2004年   9040篇
  2003年   8168篇
  2002年   7850篇
  2001年   7171篇
  2000年   6433篇
  1999年   6347篇
  1998年   7540篇
  1997年   5836篇
  1996年   4917篇
  1995年   3972篇
  1994年   3435篇
  1993年   2806篇
  1992年   2095篇
  1991年   1923篇
  1990年   1765篇
  1989年   1656篇
  1988年   1395篇
  1987年   1196篇
  1986年   1121篇
  1985年   1091篇
  1984年   895篇
  1983年   856篇
  1982年   779篇
  1981年   755篇
  1980年   743篇
  1979年   682篇
  1978年   642篇
  1977年   796篇
  1976年   974篇
  1975年   598篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
Sampled-data feedback control for master-slave synchronization schemes that consist of identical chaotic Lur'e systems is studied. Sufficient conditions for global asymptotic synchronization of such chaotic Lur'e systems are obtained using the free-weighting matrix approach and expressed in terms of linear matrix inequalities (LMIs). With the help of the LMI solvers, the sampled-data feedback control law can easily be obtained to globally asymptotically synchronize Lur'e chaotic systems. The effectiveness of the proposed method is finally illustrated via numerical simulations of chaotic Chua's circuits.  相似文献   
62.
A tri-gate bulk MOSFET design utilizing a low-aspect-ratio channel is proposed to provide an evolutionary pathway for CMOS scaling to the end of the roadmap. 3-D device simulations indicate that this design offers the advantages of a multi-gate FET (reduced variability in performance and improved scalability) together with the advantages of a conventional planar MOSFET (low substrate cost and capability for dynamic threshold-voltage control).  相似文献   
63.
A wafer level packaging technique has been developed with an inherent advantage of good solder joint co-planarity suitable for wafer level testing. A suitable weak metallization scheme has also been established for the detachment process. During the fabrication process, the compliancy of the solder joint is enhanced through stretching to achieve a small shape factor. Thermal cycling reliability of these hourglass-shaped, stretch solder interconnections has been found to be considerably better than that of the conventional spherical-shaped solder bumps.  相似文献   
64.
Porous carbon nanofibers are synthesized by CVD method from acetylene with use of iron-containing catalysts. Activation of the nanofibers in melted potassium hydroxide results in increasing surface area from initial 300–400 m2 g−1 to 1700 m2 g−1. As follows from XRD data, activated nanofibers do not contain regular packages of graphene layers, but retain high electric conductivity. Deposition of copper improves electrochemical hydrogen storing characteristics of carbon nanofibers. Carbon nanomaterials obtained can be used as hydrogen storing materials in batteries instead of hydride forming metals.  相似文献   
65.
Many approaches have been proposed to enhance software productivity and reliability. These approaches typically fall into three categories: the engineering approach, the formal approach and the knowledge-based approach. But the optimal gain in software productivity cannot be obtained if one relies on only one of these approaches. This paper describes the work in knowledge-based software engineering conducted by the authors for the past 10 years. The final goal of the research is to develop a paradigm for software engineering which integrates the three approaches mentioned above. A knowledge-based tool which can support the whole process of software development is provided in this paper.  相似文献   
66.
大门小品建筑属多项目综合性工程。本文作者从管理者的角度 ,通过对公司大门及附属工程施工质量控制的总结 ,说明了质量控制应贯穿于工程施工的全过程  相似文献   
67.
The results of a computational experiment with a neural-net model simulating the effect of the chemical composition on the plastic properties of ÉP-450 steel are presented. It is shown that computer-aided development of reactor steel with prescribed properties is, in principle, possible.  相似文献   
68.
LaNiO3 was synthesized by sol-gel method in which lanthanum nitrate and nickel nitrate were used as start materials and citric acid was used as complex for gel formation.The precursor was dried and subsequently heated at elevated temperature to form the desired product.XRD analysis shows that pure LaNiO3 was synthesized.Electrical conductivity and electrochemical performance of the material were tested.The electrical conductivity decreases from 34.5that there are current peaks in the curve, which is the evidence of the electrochemical activity of LaNiO3.  相似文献   
69.
The dielectric and pyroelectric properties of Ge-doped (0.1 mol %) TlInS2 crystals are studied. The results demonstrate that TlInS2 is a ferroelectric relaxor. The experimental data are used to evaluate, using the Vogel–Fulcher relation, the activation energy (0.045 eV), preexponential factor (f 0 = 2 × 1013 Hz), and the dipole-freezing temperature (T F = 142 K) and to determine the temperature range of the stable relaxor (nanodomain) state and the temperature of the transition to the ferroelectric (macrodomain) state, accompanied by an anomaly in the temperature-dependent pyroelectric coefficient.  相似文献   
70.
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