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   60677篇
  免费   6553篇
  国内免费   3836篇
电工技术   4120篇
技术理论   3篇
综合类   5126篇
化学工业   9737篇
金属工艺   3320篇
机械仪表   3417篇
建筑科学   5380篇
矿业工程   1778篇
能源动力   1886篇
轻工业   5095篇
水利工程   1297篇
石油天然气   2959篇
武器工业   463篇
无线电   7121篇
一般工业技术   6768篇
冶金工业   2478篇
原子能技术   810篇
自动化技术   9308篇
  2024年   367篇
  2023年   1232篇
  2022年   2141篇
  2021年   2909篇
  2020年   2204篇
  2019年   2046篇
  2018年   2096篇
  2017年   2248篇
  2016年   1929篇
  2015年   2675篇
  2014年   3197篇
  2013年   3586篇
  2012年   3805篇
  2011年   3999篇
  2010年   3700篇
  2009年   3401篇
  2008年   3304篇
  2007年   3051篇
  2006年   2952篇
  2005年   2394篇
  2004年   2091篇
  2003年   2555篇
  2002年   3432篇
  2001年   2871篇
  2000年   1543篇
  1999年   1266篇
  1998年   728篇
  1997年   659篇
  1996年   634篇
  1995年   498篇
  1994年   390篇
  1993年   276篇
  1992年   231篇
  1991年   138篇
  1990年   125篇
  1989年   89篇
  1988年   80篇
  1987年   39篇
  1986年   45篇
  1985年   34篇
  1984年   25篇
  1983年   17篇
  1982年   14篇
  1981年   11篇
  1980年   16篇
  1979年   8篇
  1976年   1篇
  1965年   1篇
  1959年   7篇
  1951年   6篇
排序方式: 共有10000条查询结果,搜索用时 27 毫秒
51.
Cover Image     
The cover image is based on the Research Article Observer‐Based Cooperative Distributed Fault‐tolerant Model Predictive Control with Imperfect Network Communication and Asynchronous Measurements by Guannan Xiao and Fei Liu, https://doi.org/10.1002/rnc.4994 .

  相似文献   

52.
The high cost of noble metal catalysts has been a great bottleneck for the catalyst industry. Using the noble metal at a single-atom level for catalytic applications could dramatically decrease the cost. The impacts of single Pt atoms on the photocatalytic performance of Ag3VO4 have been investigated and reported. In this report, single Pt atoms were anchored on the surface of Ag3VO4 (AVO) as a cocatalyst, and the resultant composite photocatalyst has been studied for photocatalytic H2 production from water driven by visible light. The as-prepared AVO particles are hollow nanospheres in the monoclinic phase with a bandgap of 2.20 eV. The light absorption edge of AVO/Pt is slightly red-shifted compared to that of the pristine AVO, indicating more visible light absorption of AVO/Pt. The XPS peaks of Ag, V, and Pt exhibit a significant shift after AVO and Pt get into contact, suggesting the strong interaction between the surface Ag and V atoms, and single Pt atoms. After 3-h illumination, the photocatalytic H2 evolution amount from AVO/Pt is improved up to 1400 μmol, which is 2.8 times that on the bare AVO. Such efficient photocatalytic H2 evolution on AVO/Pt is still maintained after five reaction cycles. The better photocatalytic performance of AVO/Pt has been attributed to the more efficient visible light utilization and the lower interfacial charge transfer resistance, as demonstrated in the DRS and EIS spectra. The presence of the surface Pt atoms also leads to a higher amount of reactive radicals, which could efficiently promote the surface redox reactions.  相似文献   
53.
54.
The titanium carbides are potential candidates to achieve both high hardness and refractory property. We carried out a structural search for titanium carbides at three pressures of 0 GPa, 30 GPa and 50 GPa. A phase diagram of the Ti-C system at 0 K was obtained by elucidating formation enthalpies as a function of compositions, and their mechanical and metallic properties of titanium carbides were investigated systematically. We also discussed the relation of titanium concentration to the both mechanical and metallic properties of titanium carbides. It has been found that the average valence electron density and tractility improved at higher concentrations of titanium, while the degree of covalent bonding directionality decreased. To this effect, the hardness of titanium carbide decreases as the content of titanium increases. Our results indicated that the titanium content significantly affected the metallic properties of the Ti-C system.  相似文献   
55.
Al2O3陶瓷激光铣削试验研究   总被引:9,自引:1,他引:8  
袁根福  曾晓雁 《中国激光》2003,30(5):467-470
采用Nd∶YAG脉冲激光器对Al2 O3陶瓷进行铣削加工试验。系统研究了工艺参数对铣削量和铣削面质量的影响规律 ,并利用优化的铣削工艺对Al2 O3陶瓷进行多种形状的铣削加工。  相似文献   
56.
肖前香  金小艳 《通信技术》2003,(12):117-119
概述了Windows2000即插即用系统组成及其实现过程,结合实例介绍了Windows2000设备驱动程序如何支持用户即插即用的功能。  相似文献   
57.
Amphiphilic magnetic microspheres ranging in diameter from 5 to 100 µm were prepared by dispersion copolymerization of styrene and poly(ethylene oxide) vinylbenzyl (PEO‐VB) macromonomer (MPEO) in the presence of Fe3O4 magnetic fluid. The effects of various polymerization parameters on the average particle size were systematically investigated. The average particle size was found to increase with increasing styrene concentration and initiator concentration. It also increased with decreasing stabilizer concentration and molecular weight of MPEO. The content of the hydroxyl groups localized in the microspheres ranged from 0.01 to 0.2 mmol g?1. © 2003 Society of Chemical Industry  相似文献   
58.
新会计准则对会计准则质量的影响   总被引:4,自引:0,他引:4  
年初,国家财政部发布了新的会计准则,这是中国会计准则建设史上的重大事件。新会计准则体现出会计准则质量的几个重要标准,提高了中国会计准则的质量。同时,分析新会计准则质量方面仍存在的一些不足。  相似文献   
59.
论文提出利用用户提供的个性化信息来随机产生关联大素数,保证了素数选取的随机化、个性化,提高了RSA算法的安全性。  相似文献   
60.
In this letter, we investigate the iterative detection/decoding algorithms for two-track partial response channels. We first describe the iterative algorithm as an iterative message-passing/processing algorithm over a high-level normal graph and then propose two trellis-based detection algorithms. The natural one is based on a joint trellis, which can be implemented for low-order channels. For moderate-order channels, we propose a separated detection, which is based on two single-track trellises. Compared with the joint detection, the separated detection is simpler in most cases. Simulation results show that, for two-track EPR4 channels with minor intertrack interferences, the separated detection causes only marginal degradation in 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