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   23336篇
  免费   3833篇
  国内免费   2496篇
电工技术   2496篇
综合类   2802篇
化学工业   1368篇
金属工艺   168篇
机械仪表   1163篇
建筑科学   593篇
矿业工程   251篇
能源动力   429篇
轻工业   700篇
水利工程   292篇
石油天然气   331篇
武器工业   463篇
无线电   6180篇
一般工业技术   1796篇
冶金工业   274篇
原子能技术   154篇
自动化技术   10205篇
  2024年   201篇
  2023年   448篇
  2022年   678篇
  2021年   798篇
  2020年   881篇
  2019年   864篇
  2018年   811篇
  2017年   1077篇
  2016年   1143篇
  2015年   1162篇
  2014年   1568篇
  2013年   1786篇
  2012年   1741篇
  2011年   1970篇
  2010年   1459篇
  2009年   1482篇
  2008年   1611篇
  2007年   1739篇
  2006年   1337篇
  2005年   1165篇
  2004年   900篇
  2003年   771篇
  2002年   644篇
  2001年   493篇
  2000年   398篇
  1999年   386篇
  1998年   297篇
  1997年   288篇
  1996年   231篇
  1995年   223篇
  1994年   194篇
  1993年   132篇
  1992年   147篇
  1991年   101篇
  1990年   95篇
  1989年   66篇
  1988年   47篇
  1987年   37篇
  1986年   27篇
  1985年   34篇
  1984年   50篇
  1983年   22篇
  1982年   38篇
  1981年   35篇
  1980年   24篇
  1979年   14篇
  1978年   13篇
  1977年   15篇
  1959年   3篇
  1956年   3篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
141.
1Introduction Orthogonal Frequency Division Multiplexing(OFDM) has become a popular technique for transmis-sion of signals over wireless channels . OFDMhas beenadoptedinseveral wireless standards such as Digital Au-dio Broadcasting ( DAB) , Digital Video Broadcasting(DVB-T) ,the IEEE 802 .11a[1]Local Area Network(LAN) standard and high performance LAN type 2(HIPERLAN/2)[2]standard. OFDMis also being pur-sued for Dedicated Short-Range Communications(DSRC) for road side to …  相似文献   
142.
A generalisation of the Burg algorithm to vector spaces is described. This can be used to subsample time series that have narrow frequency bandwidth, thereby reducing the computation time and the complexity of the autoregressive model required. The technique is preferable to conventional subsampling.  相似文献   
143.
基于Legendre多项式的随机连续系统的Markov参数估计   总被引:3,自引:3,他引:0  
赵明旺 《控制与决策》1994,9(5):372-374,378
本文在讨论连续Wisenr过程的Legendre多项式逼近值的相关性和Wiener过程扰动下连续线性系统基于该正交多项的最小二乘估计有偏性后,提出了无偏一致的且数估计误差方差最小的Markov估计(最小方差估计)算法,并给出本文方法的仿真结果。  相似文献   
144.
145.
The techniques for image analysis and classification generally consider the image sample labels fixed and without uncertainties. The rank regression problem studied in this paper is based on the training samples with uncertain labels, which often is the case for the manual estimated image labels. A core ranking model is designed first as the bilinear fusing of multiple candidate kernels. Then, the parameters for feature selection and kernel selection are learned simultaneously by maximum a posteriori for given samples and uncertain labels. The provable convergency Expectation Maximization (EM) method is used for inferring these parameters in an iterative manner. The effectiveness of the proposed algorithm is finally validated by the extensive experiments on age ranking task and human tracking task. The popular FG-NET and the large scale Yamaha aging database are used for the age estimation experiments, and our algorithm outperforms those state-of-the-art algorithms ever reported by other interrelated literatures significantly. The experiment result of human tracking task also validates its advantage over conventional linear regression algorithm. A short version of this paper appeared in ICME07.  相似文献   
146.
This paper presents a project undertaken for the European Space Agency (ESA). The project is developing a knowledge based system for planning and scheduling of activities for spacecraft assembly, integration and verification (AIV). The system extends to the monitoring of plan execution and the plan repair phases.

The objectives of the contract are to develop an operational kernel of a planning, scheduling and plan repair tool, called OPTIMUM-AIV, and to provide facilities which will allow individual projects to customize the kernel to suit its specific needs. The kernel shall consist of a set of software functionalities for assistance in the initial specification of the AIV plan, in the verification and generation of valid plans and schedules for the AIV activities, and in interactive monitoring and execution problem recovery for the detailed AIV plans. Embedded in OPTIMUM-AIV are external interfaces which allow integration with alternative scheduling systems and project databases.

The current status of the OPTIMUM-AIV project, as of May 1991, is that the architectural design of the system has been agreed on by ESTEC/ESA and detailed design and implementation is now underway, expecting a final delivery in October of 1991.  相似文献   

147.
注塑件/模具成本评估方法研究综述   总被引:5,自引:0,他引:5  
对注塑模成本评估领域的主要研究方法进行了分析 ,指出了相关的几个成本评估流派。着重对成本评估的CEF方法进行了总结 ,并对当前国际上流行的派别的优缺点进行了总结。文末 ,给出了我们的研究思路大体概述  相似文献   
148.
149.
Abstract. Large sample properties of the least‐squares and weighted least‐squares estimates of the autoregressive parameter of the explosive random‐coefficient AR(1) process are discussed. It is shown that, contrary to the standard AR(1) case, the least‐squares estimator is inconsistent whereas the weighted least‐squares estimator is consistent and asymptotically normal even when the error process is not necessarily Gaussian. Conditional asymptotics on the event that a certain limiting random variable is non‐zero is also discussed.  相似文献   
150.
Abstract— The ACPD-method was used to measure crack growth in low cycle fatigue tests at elevated temperature. The material which was investigated at T = 550°C was the ferritic steel 2.25Cr–1Mo. Characteristic values of representative hysteresis loops were determined. The crack growth data were correlated with the effective part of the fracture mechanics parameter Δ J. A new method for the calculation of Δ J is proposed.  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