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   226939篇
  免费   23668篇
  国内免费   14550篇
电工技术   19330篇
技术理论   8篇
综合类   18972篇
化学工业   30965篇
金属工艺   13969篇
机械仪表   15834篇
建筑科学   18846篇
矿业工程   7546篇
能源动力   6849篇
轻工业   17470篇
水利工程   6000篇
石油天然气   11127篇
武器工业   2800篇
无线电   27531篇
一般工业技术   22251篇
冶金工业   8916篇
原子能技术   2748篇
自动化技术   33995篇
  2024年   1156篇
  2023年   3683篇
  2022年   7453篇
  2021年   10202篇
  2020年   7708篇
  2019年   5933篇
  2018年   6700篇
  2017年   7896篇
  2016年   6899篇
  2015年   10403篇
  2014年   12994篇
  2013年   15314篇
  2012年   17923篇
  2011年   18826篇
  2010年   17324篇
  2009年   16234篇
  2008年   16302篇
  2007年   15436篇
  2006年   13785篇
  2005年   10872篇
  2004年   7542篇
  2003年   6107篇
  2002年   5814篇
  2001年   5086篇
  2000年   4102篇
  1999年   3187篇
  1998年   1995篇
  1997年   1607篇
  1996年   1480篇
  1995年   1281篇
  1994年   1023篇
  1993年   642篇
  1992年   519篇
  1991年   367篇
  1990年   291篇
  1989年   242篇
  1988年   172篇
  1987年   118篇
  1986年   102篇
  1985年   46篇
  1984年   40篇
  1983年   27篇
  1982年   35篇
  1981年   48篇
  1980年   57篇
  1979年   35篇
  1977年   10篇
  1976年   10篇
  1959年   17篇
  1951年   21篇
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
71.
A theoretical construction of one-to-many (OTM) and many-to-one (MTO) chaos synchronization communications using semiconductor lasers is presented. One center laser provides strong injections (strong link) to other side lasers, and the side lasers also provide weak injections (weak link) to the center one. Simulation results show that the side lasers synchronize with the center laser through injection-locking. In addition, messages transmitted via the strong links or the weak links experience strong chaos pass filtering, enabling us to realize OTM and MTO communications.  相似文献   
72.
In an anisotropic conductive adhesive (ACA) assembly, the electrical conduction is usually achieved with the conductive particles between the bumps of integrated circuit (IC) and corresponding conductive tracks on the glass substrate. Fully understanding of the mechanical and electrical characteristics of ACA particles can help to optimize the assembly process and improve the reliability of ACA interconnection. Most conductive particles used in the ACA assembly are with cracks in the metal coating of the particles after the ACA bonding. This paper introduced the fracture analysis by applying the cohesive elements in the numerical model of the nickel-coated polymer particle and further simulating the cracks initiation and propagation in the nickel coating during the ACA bonding. The simulation results showed that the stress distribution on the nickel-coated particle with cracks was significantly different from that on the nickel-coated particle without crack, indicating that the stress analysis by taking the crack into consideration is very important for the reliability assessment of the ACA interconnection. The stress analysis of cohesive elements indicated that the cracks initiated at the central area of the nickel coating and propagated to the polar area. Furthermore, by the introduction of a new parameter of the virtual resistance, a mathematical model was established to describe the electrical characteristics of the nickel-coated particle with cracks. The particle resistance of the nickel-coated particle with cracks was found to be much higher than that of the particle without crack in the optimized bonding pressure range, indicating that it is necessary to take the crack into consideration for the particle conduction analysis as well. Therefore, the fracture analysis on the conductive particle by taking the crack into consideration could accurately evaluate the reliability of ACA interconnection and avoid serious reliability issues.  相似文献   
73.
74.
水泥厂回转窑简体内砌筑了耐火砖隔热,但仍有部分热通过简体以辐射的形式散失到大气中,吸收利用这部分辐射热也是一项节能减排的举措.  相似文献   
75.
缺乏有力的监督和制约机制是我国行政判决执行难的重要原因之一.主张赋予检察机关时行政诉讼执行环节实施法律监督的权利.从而有效防止执行程序违法.抑制怠于执行和拖延执行现象的发生.阐述了由检察机关实施监督的法理依据,介绍了检察监督的方式.  相似文献   
76.
从关联分析法看如何改善沥青抗老化性能   总被引:1,自引:1,他引:0  
用灰色关联分析法研究了沥青抗老化性能与沥青化学组成之间的关联程度,结果表明,影响再生沥青性质的主要因素是沥青中的芳烃和胶质的含量。通过添加芳香组分能改善沥青四组分之间的配伍性,从而可以改善再生沥青的抗老化性能。并通过对再生剂进行富芳处理,验证了上述结论。  相似文献   
77.
78.
The main difficulty with EM algorithm for mixture model concerns the number of components, say g. This is the question of model selection, and the EM algorithm itself could not estimate g. On the contrary, the algorithm requires g to be specified before the remaining parameters can be estimated. To solve this problem, a new algorithm, which is called stepwise split-and-merge EM (SSMEM) algorithm, is proposed. The SSMEM algorithm alternately splits and merges components, estimating g and other parameters of components simultaneously. Also, two novel criteria are introduced to efficiently select the components for split or merge. Experimental results on simulated and real data demonstrate the effectivity of the proposed algorithm.  相似文献   
79.
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   
80.
李文涛  丁美新  何斌 《电子工程师》2004,30(2):61-63,74
利用CPLD芯片实现单片机与ISA总线接口之间的高速并行通信,给出系统的总体设计方法及程序框图。采用这种通信方式,在12MHz晶振的MCS51单片机控制的数据采集系统中,可以满足与PCI04 ISA总线接口实时通信的要求,通信速率达200khit/s。在开发工具MAX plusⅡ下,完成了整个设计的输入、编译和仿真,达到了预期效果。本设计方案能够推广应用到计算机的高速并行通信中。  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