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   12591篇
  免费   1007篇
  国内免费   454篇
电工技术   648篇
综合类   809篇
化学工业   2173篇
金属工艺   742篇
机械仪表   762篇
建筑科学   1015篇
矿业工程   357篇
能源动力   324篇
轻工业   591篇
水利工程   190篇
石油天然气   806篇
武器工业   73篇
无线电   1436篇
一般工业技术   1714篇
冶金工业   693篇
原子能技术   119篇
自动化技术   1600篇
  2024年   68篇
  2023年   273篇
  2022年   337篇
  2021年   501篇
  2020年   413篇
  2019年   327篇
  2018年   415篇
  2017年   436篇
  2016年   409篇
  2015年   449篇
  2014年   590篇
  2013年   675篇
  2012年   753篇
  2011年   823篇
  2010年   672篇
  2009年   676篇
  2008年   692篇
  2007年   617篇
  2006年   678篇
  2005年   622篇
  2004年   419篇
  2003年   356篇
  2002年   330篇
  2001年   249篇
  2000年   287篇
  1999年   336篇
  1998年   282篇
  1997年   272篇
  1996年   231篇
  1995年   177篇
  1994年   164篇
  1993年   125篇
  1992年   99篇
  1991年   72篇
  1990年   77篇
  1989年   31篇
  1988年   38篇
  1987年   24篇
  1986年   19篇
  1985年   5篇
  1984年   7篇
  1983年   8篇
  1982年   6篇
  1981年   4篇
  1980年   4篇
  1979年   4篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
191.
A directed searching optimization algorithm (DSO) is proposed to solve constrained optimization problems in this paper. The proposed algorithm includes two important operations — position updating and genetic mutation. Position updating enables the non-best solution vectors to mimic the best one, which is beneficial to the convergence of the DSO; genetic mutation can increase the diversity of individuals, which is beneficial to preventing the premature convergence of the DSO. In addition, we adopt the penalty function method to balance objective and constraint violations. We can obtain satisfactory solutions for constrained optimization problems by combining the DSO and the penalty function method. Experimental results indicate that the proposed algorithm can be an efficient alternative on solving constrained optimization problems.  相似文献   
192.
A structured-based neural network (NN) with backpropagation through structure (BPTS) algorithm is conducted for image classification in organizing a large image database, which is a challenging problem under investigation. Many factors can affect the results of image classification. One of the most important factors is the architecture of a NN, which consists of input layer, hidden layer and output layer. In this study, only the numbers of nodes in hidden layer (hidden nodes) of a NN are considered. Other factors are kept unchanged. Two groups of experiments including 2,940 images in each group are used for the analysis. The assessment of the effects for the first group is carried out with features described by image intensities, and, the second group uses features described by wavelet coefficients. Experimental results demonstrate that the effects of the numbers of hidden nodes on the reliability of classification are significant and non-linear. When the number of hidden nodes is 17, the classification rate on training set is up to 95%, and arrives at 90% on the testing set. The results indicate that 17 is an appropriate choice for the number of hidden nodes for the image classification when a structured-based NN with BPTS algorithm is applied.  相似文献   
193.
磁盘的随机I/O延时制约了存储系统的性能提高,具备高性能随机I/O特性的固态盘(solid state disk,SSD)逐渐成为关注的热点.分析了磁盘、Flash型SSD以及DRAM型SSD三类设备不同的性能特点,讨论了SSD存储加速技术的研究现状,提出了一种面向Lustre文件系统的固态盘存储加速系统架构,介绍和分析了各模块的构成与原理,提出了对象迁移策略.  相似文献   
194.
The profile of the nano-mold can also influence the replication precision of the final 2D polymer nanochannels. In the present work, the aspect ratio of the nano-mold, the duty ratio of the nano-mold, and the thickness ratio were investigated by numerical simulation method. The replication precision of the 2D polymer nanochannels is evaluated by imprinting ratio. The simulation results show that the lower aspect ratio and duty ratio is associated with higher imprinting ratio. However, the imprinting ratio increases with the thickness ratio at beginning and then keeps nearly unchanged as the thickness ratio continuously increases. The proper thickness ratio is two. The imprinting temperature and pressure were also optimized according the imprinting ratio. The simulation results show that the optimal imprinting temperature and pressure were 120 °C and 1.5 MPa, respectively.  相似文献   
195.
Lu  Gui-Fu  Zou  Jian  Wang  Yong  Wang  Zhongqun 《Multimedia Tools and Applications》2017,76(14):15801-15816
Multimedia Tools and Applications - Null space based linear discriminant analysis (NSLDA) is a well-known feature extraction method, which can make use of the most discriminant information in the...  相似文献   
196.
A broadcasting multiple blind signature scheme based on quantum GHZ entanglement has been presented recently. It is said that the scheme’s unconditional security is guaranteed by adopting quantum key preparation, quantum encryption algorithm and quantum entanglement. In this paper, we prove that each signatory can get the signed message just by an intercept–resend attack. Then, we show there still exist some participant attacks and external attacks. Specifically, we verify the message sender Alice can impersonate each signatory to sign the message at will, and so is the signature collector Charlie. Also, we demonstrate that the receiver Bob can forge the signature successfully, and with respect to the external attacks, the eavesdropper Eve can modify the signature at random. Besides, we discover Eve can change the signed message at random, and Eve can impersonate Alice as the message sender without being discovered. In particular, we propose an improved scheme based on the original one and show that it is secure against not only the attacks mentioned above but also some collusion attacks.  相似文献   
197.
This paper studies the mean square quadratic (MSQ) detectability for multi-output networked systems over finite-state digital block-fading channels. The packet-loss rate of each digital fading channel depends on the channel power gain, as well as packet length and power level used for transmission. A finite-state random process is introduced to model time-varying fading channels, which characterizes various configurations of physical communication environment and/or different channel fading amplitudes. Necessary and sufficient conditions for MSQ detectability over finite-state Markov digital block-fading channels are given in the form of algebraic Riccati equations or linear matrix inequalities (LMIs). The estimation gain is given as a function of estimated/observed channel state. In addition, explicit conditions on network for MSQ detectability over finite-state independent identically distributed (i.i.d.) digital block-fading channels are presented in terms of the unstable poles of the multi-output plant. Finally, an application to Gilbert-Elliott channels (GECs) is provided to demonstrate the derived results.  相似文献   
198.
International Journal of Control, Automation and Systems - This paper concerns the attitude control problem of a 3D rigid pendulum based on dynamic T-S fuzzy neural model. A generalized 3D rigid...  相似文献   
199.
针对现有的感兴趣区域(ROI)提取方法边缘不清晰、区域不完整等问题,提出一种ROI提取方法.首先采用颜色局部特征的信息量大小衡量兴趣度的大小,然后融合颜色特征信息量图获得图像的显著图(SM),再进行阈值分割,得到显著值大的区域,即ROI.实验结果表明,该方法能有效地提取出感兴趣的对象,SM中目标区域的显著值均匀、边缘清晰;与人工标记的ROI比较,该方法召回率为79.71%,精度为78.53%,优于已有的ROI提取方法.  相似文献   
200.
为了提高教学效率,使优秀的教学资源和信息能够在更大范围、短时间内迅速传播,采用Dreamweaver工具和ASP技术开发了网络教学平台.教学网站前台采用动态网页设计,后台使用SQL Server 2005数据库以满足大用户量的需求.网站实现了在线答疑、讨论、课件上传下载、教学管理及用户管理等功能,并通过了测试和试运行.该网站的实现为教师和学生提供了一个高效、方便的网络教学环境.  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