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   15700篇
  免费   2396篇
  国内免费   1085篇
电工技术   1911篇
综合类   1688篇
化学工业   1683篇
金属工艺   368篇
机械仪表   1503篇
建筑科学   852篇
矿业工程   391篇
能源动力   354篇
轻工业   1909篇
水利工程   364篇
石油天然气   570篇
武器工业   111篇
无线电   1915篇
一般工业技术   2378篇
冶金工业   238篇
原子能技术   313篇
自动化技术   2633篇
  2024年   80篇
  2023年   316篇
  2022年   565篇
  2021年   676篇
  2020年   651篇
  2019年   621篇
  2018年   639篇
  2017年   714篇
  2016年   789篇
  2015年   785篇
  2014年   1079篇
  2013年   1139篇
  2012年   1225篇
  2011年   1281篇
  2010年   846篇
  2009年   832篇
  2008年   878篇
  2007年   949篇
  2006年   798篇
  2005年   667篇
  2004年   581篇
  2003年   537篇
  2002年   365篇
  2001年   311篇
  2000年   321篇
  1999年   228篇
  1998年   179篇
  1997年   200篇
  1996年   170篇
  1995年   115篇
  1994年   117篇
  1993年   87篇
  1992年   82篇
  1991年   70篇
  1990年   48篇
  1989年   38篇
  1988年   33篇
  1987年   27篇
  1986年   16篇
  1985年   28篇
  1984年   21篇
  1983年   20篇
  1982年   30篇
  1981年   3篇
  1980年   6篇
  1979年   6篇
  1961年   2篇
  1960年   1篇
  1959年   2篇
  1955年   2篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
3.
This paper deals with the problem of designing a robust static output feedback controller for polytopic systems. The current research that tackled this problem is mainly based on LMI method, which is conservative by nature. In this paper, a novel approach is proposed, which considers the design space of the controller parameters and iteratively partitions the space to small simplexes. Then, by assessing the stability in each simplex, the solution space for design parameters is directly determined. It has been theoretically proved that, if there exists a feasible solution in the design space, the algorithm can find it. To validate the result of the proposed approach, comparative simulation examples are given to illustrate the performance of the design methodology as compared to those of previous approaches.  相似文献   
4.
The selenol group of selenocysteine is much more nucleophilic than the thiol group of cysteine. Selenocysteine residues in proteins thus offer reactive points for rapid post-translational modification. Herein, we show that selenoproteins can be expressed in high yield and purity by cell-free protein synthesis by global substitution of cysteine by selenocysteine. Complete alkylation of solvent-exposed selenocysteine residues was achieved in 10 minutes with 4-chloromethylene dipicolinic acid (4Cl-MDPA) under conditions that left cysteine residues unchanged even after overnight incubation. GdIII−GdIII distances measured by double electron–electron resonance (DEER) experiments of maltose binding protein (MBP) containing two selenocysteine residues tagged with 4Cl-MDPA-GdIII were indistinguishable from GdIII−GdIII distances measured of MBP containing cysteine reacted with 4Br-MDPA tags.  相似文献   
5.
Protective coatings from diethylphosphatoethyltriethoxysilane (DEPETS) have been deposited on different polymer substrates in a plasma discharge operated at atmospheric pressure. Plasma polymer chemistry and structure were characterized by means of Fourier transform infrared spectroscopy (FTIR), laser desorption ionization-mass spectrometry (LDI-MS), nuclear magnetic resonance (NMR) and scanning electron microscopy (SEM). A chemical structure of the plasma polymer has been proposed based on the coating molecular characterization. Coatings were deposited on polycarbonate (PC) and polyamide 6 (PA6) substrates. The flame retardant properties of coated substrate samples were assessed using cone calorimetry and compared to those of bare substrates. A significant increase in the time to ignition (TTI), up to +143%, was recorded after coating deposition due to the formation of a high-performance barrier layer at the surface of both polymer substrates.  相似文献   
6.
7.
In the early design stage, automotive modeling should both meet the requirements of aesthetics and engineering. Therefore, a vehicle CAD (computer aided design) model that can be easily adjusted by feedbacks is necessary. Based on CE-Bézier surface, this paper presents a set of algorithms for parametric segmentation and fairing surface generation in a car model. This model is defined by a simplified automotive template and relevant control points, shape parameters and segmentation parameters, which can be modified to alter the car form efficiently. With this model and the corresponding adjustment method, more than fifty various vehicle models are established in this research according to different parameters. And two methods for calculating similarity index between car models are constructed, which are suitable for brand design trend analysis and modelling design decisionmaking.  相似文献   
8.
9.
BaTiO3基Au纳米颗粒复合薄膜的制备及其光学性质研究   总被引:1,自引:1,他引:0  
采用溶胶-凝胶(sol-gel)方法,成功的将高体积面分比的Au纳米颗粒复合到BaTiO3的非晶薄膜中,并对其光学性质进行了研究。用XRD、TEM、椭偏仪、吸收光谱、光克尔效应OKE(Optical Kerr Effcet)方法对薄膜进行了表征和测试。从吸收光谱观察到表面等离子体共振SPR(Surface Plasma Resonance)峰随热处理温度升高而红移的现象。光学非线性测试表明薄膜具有高的三阶非线性极化率Χ^(3)和超快的响应时间。  相似文献   
10.
讨论了主因素分析法以及神经网络法在等离子体刻蚀工艺中的应用.结果表明主元素分析法可以实现对数据的压缩,而神经网络算法则显示出比传统的统计过程控制算法更好的准确性.  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