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   206478篇
  免费   15472篇
  国内免费   7843篇
电工技术   11303篇
技术理论   14篇
综合类   11274篇
化学工业   35868篇
金属工艺   10562篇
机械仪表   12040篇
建筑科学   16502篇
矿业工程   4980篇
能源动力   5870篇
轻工业   12750篇
水利工程   3250篇
石油天然气   11122篇
武器工业   1348篇
无线电   25527篇
一般工业技术   26788篇
冶金工业   10956篇
原子能技术   2118篇
自动化技术   27521篇
  2024年   889篇
  2023年   3276篇
  2022年   5876篇
  2021年   7974篇
  2020年   5822篇
  2019年   5032篇
  2018年   5439篇
  2017年   6238篇
  2016年   5728篇
  2015年   7329篇
  2014年   9561篇
  2013年   12311篇
  2012年   12282篇
  2011年   13926篇
  2010年   11663篇
  2009年   11514篇
  2008年   10938篇
  2007年   10497篇
  2006年   10893篇
  2005年   9649篇
  2004年   6586篇
  2003年   5789篇
  2002年   5261篇
  2001年   4734篇
  2000年   4882篇
  1999年   5649篇
  1998年   5301篇
  1997年   4361篇
  1996年   3960篇
  1995年   3311篇
  1994年   2772篇
  1993年   2188篇
  1992年   1702篇
  1991年   1279篇
  1990年   1018篇
  1989年   878篇
  1988年   682篇
  1987年   496篇
  1986年   394篇
  1985年   334篇
  1984年   212篇
  1983年   198篇
  1982年   163篇
  1981年   145篇
  1980年   131篇
  1979年   97篇
  1978年   63篇
  1977年   63篇
  1976年   77篇
  1975年   38篇
排序方式: 共有10000条查询结果,搜索用时 8 毫秒
991.
This paper presents an innovative neural network-based quality prediction system for a plastic injection molding process. A self-organizing map plus a back-propagation neural network (SOM-BPNN) model is proposed for creating a dynamic quality predictor. Three SOM-based dynamic extraction parameters with six manufacturing process parameters and one level of product quality were dedicated to training and testing the proposed system. In addition, Taguchi’s parameter design method was also applied to enhance the neural network performance. For comparison, an additional back-propagation neural network (BPNN) model was constructed for which six process parameters were used for training and testing. The training and testing data for the two models respectively consisted of 120 and 40 samples. Experimental results showed that such a SOM-BPNN-based model can accurately predict the product quality (weight) and can likely be used for various practical applications.  相似文献   
992.
Intelligent adaptive control for MIMO uncertain nonlinear systems   总被引:3,自引:1,他引:2  
This paper investigates an intelligent adaptive control system for multiple-input–multiple-output (MIMO) uncertain nonlinear systems. This control system is comprised of a recurrent-cerebellar-model-articulation-controller (RCMAC) and an auxiliary compensation controller. RCMAC is utilized to approximate a perfect controller, and the parameters of RCMAC are on-line tuned by the derived adaptive laws based on a Lyapunov function. The auxiliary compensation controller is designed to suppress the influence of residual approximation error between the perfect controller and RCMAC. Finally, two MIMO uncertain nonlinear systems, a mass–spring–damper mechanical system and a Chua’s chaotic circuit, are performed to verify the effectiveness of the proposed control scheme. The simulation results confirm that the proposed intelligent adaptive control system can achieve favorable tracking performance with desired robustness.  相似文献   
993.
In practical electro-pneumatic or hydraulic servo mechanism, there is usually an unavoidable operating delay time in the solenoid valves. This may sometimes cause closed-loop instability if the time delay is not treated carefully in the control system designs. Furthermore, pneumatic actuators can offer high performance at low cost, but are often suffered from external disturbances depending on the operating conditions. This paper proposes a non-model-based design approach for pneumatic actuating systems. In the proposed control system, a gain scheduled fuzzy-PID controller ensures tracking performance an adaptable wavelet neuro compensator compensates for time-delay of the control valve, and a disturbance rejecter diminishes influence from load changes. A condition ensuring the closed-loop stability is derived. The proposed design is experimentally verified to show its effectiveness.  相似文献   
994.
Providing context-aware Web services is an adaptive process of delivering contextually matched Web services to meet service requesters’ needs. We define the term “context” from two perspectives: one from service requesters; and the other from Web services. From the former perspective, context is defined as the surrounding environment affecting requesters’ services discovery and access, such as requesters’ preferences, locations, activities, and accessible network and devices. From the latter perspective, context is defined as the surrounding environment affecting Web services delivery and execution, such as networks and protocols for service binding, devices and platforms for service execution, and so on. This paper presents a Java Expert System Shell (JESS)-enabled context elicitation system featuring an ontology-based context model that formally describes and acquires contextual information pertaining to service requesters and Web services. Based on the context elicitation system, we present a context-aware services-oriented architecture for providing context-aware Web service request, publication, and discovery. Implementation details of the context elicitation system and the evaluation results of context-aware service provision are also reported.  相似文献   
995.
Feature selection is about finding useful (relevant) features to describe an application domain. Selecting relevant and enough features to effectively represent and index the given dataset is an important task to solve the classification and clustering problems intelligently. This task is, however, quite difficult to carry out since it usually needs a very time-consuming search to get the features desired. This paper proposes a bit-based feature selection method to find the smallest feature set to represent the indexes of a given dataset. The proposed approach originates from the bitmap indexing and rough set techniques. It consists of two-phases. In the first phase, the given dataset is transformed into a bitmap indexing matrix with some additional data information. In the second phase, a set of relevant and enough features are selected and used to represent the classification indexes of the given dataset. After the relevant and enough features are selected, they can be judged by the domain expertise and the final feature set of the given dataset is thus proposed. Finally, the experimental results on different data sets also show the efficiency and accuracy of the proposed approach.  相似文献   
996.
矩阵已作为一种常用的数学表示方法被普遍地运用在三维动画领域中,然而大多数线性代数书籍中关于矩阵的描述都是基于普遍性的数学概念的介绍,这种矩阵对于很多三维动画从业人员来说,还较难理解.旨在通过使用Maya,对矩阵这个数学概念在三维动画中担当的角色以及其作用进行简单说明,以提供给三维动画制作者一个易懂易用的参考.  相似文献   
997.
最大团问题MCP(Maximum Clique Problem)在国外得到了广泛的研究,在国内刚起步,是一类NP完全问题。传统的确定性算法不能有效地进行求解。定义了MCP;介绍了使用启发式算法求解MCP的研究进展;综述了几种典型的智能搜索算法;分析了使用这些典型算法求解MCP的基本思想;研究了这些智能算法在求解MCP时的特点及性能。  相似文献   
998.
分析了早期无线局域网测试方法的特点,从面向应用的角度,提出了一种全面综合的测试分析方法,并在此基础上设计了无线局域网测试系统体系结构模型及应包含的功能模块,实现了基于PDA的无线局域网测试系统.  相似文献   
999.
基于COM的Delphi和Matlab接口编程研究   总被引:3,自引:0,他引:3  
简要介绍了Delphi与Matlab各自的优缺点,较为全面地列举和分析了二者接口编程的几种方式,重点讨论了Delphi调用Matlab编译生成的COM组件的方法和原理,实现二者的无缝集成.提供的实现过程和应用实例均说明了该方法简便、可操作性强.通过Delphi和Matlab的整合,可以根据实际需要,开发功能强大而且界面友好的软件.  相似文献   
1000.
基于WAP的校园无线门户网站设计与实现   总被引:3,自引:0,他引:3  
WAP(Wireless Application Protocol)是Internet与移动网络有机结合的技术,为无线数据应用提供了平台.通过详细介绍WAP技术的原理与编程开发模型,根据校园门户网站的新需求,将JSP(Java Server Pages)技术与WAP技术相结合,设计和开发了校园无线门户网站,提出了在开发过程中出现的关键技术问题,并给出相应的解决方案.  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