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   36327篇
  免费   3440篇
  国内免费   1877篇
电工技术   2505篇
技术理论   2篇
综合类   2434篇
化学工业   5816篇
金属工艺   1975篇
机械仪表   2415篇
建筑科学   3531篇
矿业工程   1025篇
能源动力   1015篇
轻工业   2779篇
水利工程   687篇
石油天然气   1727篇
武器工业   323篇
无线电   4427篇
一般工业技术   4205篇
冶金工业   1452篇
原子能技术   493篇
自动化技术   4833篇
  2024年   198篇
  2023年   726篇
  2022年   1331篇
  2021年   1799篇
  2020年   1316篇
  2019年   1056篇
  2018年   1114篇
  2017年   1238篇
  2016年   1207篇
  2015年   1516篇
  2014年   1962篇
  2013年   2177篇
  2012年   2440篇
  2011年   2602篇
  2010年   2390篇
  2009年   2211篇
  2008年   2076篇
  2007年   1921篇
  2006年   1886篇
  2005年   1583篇
  2004年   1054篇
  2003年   988篇
  2002年   924篇
  2001年   847篇
  2000年   785篇
  1999年   810篇
  1998年   582篇
  1997年   540篇
  1996年   520篇
  1995年   424篇
  1994年   356篇
  1993年   220篇
  1992年   183篇
  1991年   130篇
  1990年   87篇
  1989年   89篇
  1988年   67篇
  1987年   47篇
  1986年   36篇
  1985年   26篇
  1984年   14篇
  1983年   15篇
  1982年   12篇
  1981年   8篇
  1980年   10篇
  1979年   10篇
  1962年   42篇
  1961年   39篇
  1960年   16篇
  1951年   5篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
嵌入式触摸屏在汽车实验记录仪中的应用   总被引:1,自引:1,他引:0  
如今流行的汽车实验记录仪多为键盘控制,通过对基于S3C2410芯片的触摸屏应用于汽车实验记录仪的研究,阐述了触摸屏的工作原理、硬件电路结构和相关的驱动程序;为了与其他的处理器兼容,没有采用S3C2410芯片内部的A/D通道,而是采用外扩控制器ADS7846的方式,同时介绍了触摸屏接口芯片ADS7846的功能和使用方法,并对一些源代码进行了分析,数据之间通过SPI总线进行通信,电路结构简单;该触摸屏应用于汽车实验记录仪中,具有良好的人机界面、直观的操作、精度高的优点.  相似文献   
42.
Brownfield redevelopment (BR) is an ongoing issue for governments, communities, and consultants around the world. It is also an increasingly popular research topic in several academic fields. Strategic decision support that is now available for BR is surveyed and assessed. Then a dominance-based rough-set approach is developed and used to classify cities facing BR issues according to the level of two characteristics, BR effectiveness and BR future needs. The data for the classification are based on the widely available results of a survey of US cities. The unique features of the method are its reduced requirement for preference information, its ability to handle missing information effectively, and the easily understood linguistic decision rules that it generates, based on a training classification provided by experts. The resulting classification should be a valuable aid to cities and governments as they plan their BR projects and budgets.  相似文献   
43.
提出一种基于费歇尔方法的人脸识算法。分别论述了特征脸和费歇尔脸方法用于人脸识别的基本原理,给出了详细的算法过程。最后在ORL人脸数据库对算法进行了验证,采用三阶近邻分类器对测试图像进行了分类识别,比较了两种算法的识别效率。实验表明,费歇尔方法方法要优于特征脸方法。  相似文献   
44.
针对通信保密装备可靠性建模难度大的问题,提出了一种新的适用于复杂系统的可靠性建模方法一最小通路法。通过在系统拓扑结构图上搜索出所有能够使系统正常工作的最小通路,建立系统的可靠性模型。该方法基于广义的网络拓扑结构,因此网络的源节点和目标节点不必局限于严格的定义,可以随意指定,具有很大的灵活性。实例证明,该方法可行有效。  相似文献   
45.
Rolling texture and its effect on tensile properties of Ti60 alloy plates were investigated in the present study. The plates wereβ-rolled at 1070℃ and(α+β)-rolled at 980℃, using uni-directionally rolling(UDR) and cross-directionally rolling(CDR) processes, respectively.β-rolled plates exhibited weak textures, which were attributed to the dispersive orientations of secondary α during the β→α phase transformation. Strong deformation textures formed in(α+β)-rolled plates as a result of slipping mechanisms: the strong T-type texture in UDR plate was related to {10 1 0}[11 2 0] slipping, while the B-type texture in CDR plate was relevant with {0001}[11 2 0] slip. Strong T-type textures led to anisotropic tensile properties. B-type textures would decrease such an anisotropy. The(α+β)-CDR process was found to be a candidate process for reducing anisotropy of Ti60 alloy plates.  相似文献   
46.
Zhang  Ye  Guo  Jiangna  Xu  Dan  Sun  Yi  Yan  Feng 《Nano Research》2018,11(7):3899-3910
Nano Research - Copper nanowires (CuNWs) are becoming an indispensable item for next-generation transparent optical devices due to their excellent conductivity and transparency. In this work,...  相似文献   
47.
Origami-based metamaterials have widespread application prospects in various industries including aerospace, automotive, flexible electronics, and civil engineering structures. Among the wide range of origami patterns, the fourfold tessellation known as Miura-ori is of particular attraction to engineers and designers. More specifically, researchers have proposed different 3D structures and metamaterials based on the geometric characteristics of this classic origami pattern. Herein, a computational modeling approach for the design and evaluation of 3D cellular solids with the Miura-ori metamaterial geometry which can be of zero or nonzero thicknesses is presented. To this end, first, a range of design alternatives generated based on a numerical parametric model is designed. Next, their mechanical properties and failure behavior under quasistatic axial compressive loads along three perpendicular directions are analyzed. Then, the effects of various geometric parameters on their energy absorption behavior under compression in the most appropriate direction are investigated. The findings of this study provide a basis for future experimental investigations and the potential application of such cellular solids for energy-absorbing purposes.  相似文献   
48.
This article presents a mathematical model of the shock-free unsteady nonisothermal turbulent flow of a viscous nonideal chemically inert multicomponent gas mix in the offshore circular cross-section gas pipeline with a rigid multilayer coating. The calculations of flow characteristics are given for the problem of the pipeline’s shift to the periodic condition under a periodic change of the consumption rate at the right end.  相似文献   
49.
企业办公自动化系统的应用十分广泛,随着互联网的高速发展,WEB应用成为主流,OA系统在互联网上的延伸成为大趋势,本文阐述在WEB应用中如何保障数据和系统安全的手段和方法。  相似文献   
50.
Understanding the TCP congestion control mechanism from a global optimization point of view is not only important in its own right, but also crucial to the design of other transport layer traffic control protocols with provable properties. In this paper, we derive a global utility function and the corresponding optimal control law, known as TCP control law, which maximizes the global utility. The TCP control law captures the essential behaviors of TCP, including slow start, congestion avoidance, and the binary nature of congestion feedback in TCP. We find that the utility function of TCP is linear in the slow start phase and is proportional to the additive increase rate and approaches the well-known logarithm function as the data rate becomes large in the congestion avoidance phase. We also find that understanding the slow start phase with a fixed threshold is critical to the design of new transport layer control protocols to enable quality of service features. Finally, as an application, we design a Minimum Rate Guaranteed (MRG) traffic control law that shares the same utility function as the TCP control law. Our simulation study of the MRG control law indicates that it is indeed TCP friendly and can provide minimum rate guarantee as long as the percentage of network resource consumed by the MRG flows is moderately small.  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