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   89130篇
  免费   8325篇
  国内免费   5051篇
电工技术   6382篇
技术理论   5篇
综合类   6916篇
化学工业   13629篇
金属工艺   5262篇
机械仪表   5473篇
建筑科学   6844篇
矿业工程   2479篇
能源动力   2565篇
轻工业   8983篇
水利工程   1935篇
石油天然气   4158篇
武器工业   894篇
无线电   10196篇
一般工业技术   9398篇
冶金工业   3873篇
原子能技术   1037篇
自动化技术   12477篇
  2024年   414篇
  2023年   1451篇
  2022年   2886篇
  2021年   3819篇
  2020年   2862篇
  2019年   2329篇
  2018年   2593篇
  2017年   2943篇
  2016年   2733篇
  2015年   3882篇
  2014年   4818篇
  2013年   5825篇
  2012年   6630篇
  2011年   7165篇
  2010年   6351篇
  2009年   6127篇
  2008年   6133篇
  2007年   5626篇
  2006年   5214篇
  2005年   4244篇
  2004年   3082篇
  2003年   2603篇
  2002年   2534篇
  2001年   2049篇
  2000年   1574篇
  1999年   1351篇
  1998年   1034篇
  1997年   848篇
  1996年   739篇
  1995年   596篇
  1994年   459篇
  1993年   327篇
  1992年   264篇
  1991年   211篇
  1990年   166篇
  1989年   111篇
  1988年   112篇
  1987年   68篇
  1986年   66篇
  1985年   33篇
  1984年   42篇
  1983年   23篇
  1982年   31篇
  1981年   22篇
  1980年   31篇
  1979年   20篇
  1976年   13篇
  1975年   6篇
  1973年   6篇
  1959年   9篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
131.
The mathematical theory of evidence is a generalization of the Bayesian theory of probability. It is one of the primary tools for knowledge representation and uncertainty and probabilistic reasoning and has found many applications. Using this theory to solve a specific problem is critically dependent on the availability of a mass function (or basic belief assignment). In this paper, we consider the important problem of how to systematically derive mass functions from the common multivariate data spaces and also the ensuing problem of how to compute the various forms of belief function efficiently. We also consider how such a systematic approach can be used in practical pattern recognition problems. More specifically, we propose a novel method in which a mass function can be systematically derived from multivariate data and present new methods that exploit the algebraic structure of a multivariate data space to compute various belief functions including the belief, plausibility, and commonality functions in polynomial-time. We further consider the use of commonality as an equality check. We also develop a plausibility-based classifier. Experiments show that the equality checker and the classifier are comparable to state-of-the-art algorithms.  相似文献   
132.
A Regression Approach to Music Emotion Recognition   总被引:3,自引:0,他引:3  
Content-based retrieval has emerged in the face of content explosion as a promising approach to information access. In this paper, we focus on the challenging issue of recognizing the emotion content of music signals, or music emotion recognition (MER). Specifically, we formulate MER as a regression problem to predict the arousal and valence values (AV values) of each music sample directly. Associated with the AV values, each music sample becomes a point in the arousal-valence plane, so the users can efficiently retrieve the music sample by specifying a desired point in the emotion plane. Because no categorical taxonomy is used, the regression approach is free of the ambiguity inherent to conventional categorical approaches. To improve the performance, we apply principal component analysis to reduce the correlation between arousal and valence, and RReliefF to select important features. An extensive performance study is conducted to evaluate the accuracy of the regression approach for predicting AV values. The best performance evaluated in terms of the R 2 statistics reaches 58.3% for arousal and 28.1% for valence by employing support vector machine as the regressor. We also apply the regression approach to detect the emotion variation within a music selection and find the prediction accuracy superior to existing works. A group-wise MER scheme is also developed to address the subjectivity issue of emotion perception.  相似文献   
133.
基于Windows Media的网络媒体服务系统的实现   总被引:6,自引:0,他引:6  
介绍了Windows Media系统的体系结构和通信协议,构建了采用Windows Media技术的网络媒体服务系统,详细叙述了系统的连接、配置和技术要点,以较低的代价实现了媒体服务系统的应用。  相似文献   
134.
Published online: 25 July 2001  相似文献   
135.
ProxyServer中Cache的管理和使用   总被引:1,自引:0,他引:1  
使用Cache可以减少Brower的等待时间和降低代理服务器和Internet的通信量,本文主要介绍了Proxy对Cache管理和使用。  相似文献   
136.
Metal-semiconductor field effect transistors (MESFETs) were fabricated on H-terminated polycrystalline diamond.The DC characteristics of the p-channel MESFET showed a maximum drain current density of 204 mA/mm at a gate-source voltage of 6 V,and a maximum transconductance of 20 mS/mm at a gate-source voltage of 1.5 V.The small signal S-parameters of MESFET with 2 100 m gate width and 2 m gate length were measured.An extrinsic cut-off frequency (fT) of 1.7 GHz and the maximum oscillation frequency (fmax) of 2.5 GHz were obtained,which was the first report on diamond MESFETs with RF characteristics in China.  相似文献   
137.
基于改进免疫遗传算法的电网故障诊断研究   总被引:1,自引:0,他引:1  
针对电网故障的特点,应用一种改进的免疫遗传算法对电网故障进行研究。该算法能够较好地解决传统遗传算法的不足。通过引入新的交叉和变异率,更多考虑了种群的全局特征,采用动态自适应方式提取疫苗,避免了传统遗传算法收敛速度较慢的缺点。改进的算法本着优胜劣汰的思想,删除适值较低的抗体群,取而代之的是随机生成的部分新抗体,保持种群的多样性。建立一个新的目标函数,通过对一个电网的分析,验证了方法的有效性。  相似文献   
138.
Due to the nature of distribution and self-organization, mobile ad hoc networks rely on cooperation between nodes to transfer information. One of the key factors to ensure high communication quality is an efficient assessment scheme for risks and trust of choosing next potential cooperative nodes. Trust model, an abstract psychological cognitive process, is one of the most complex concepts in social relationships, involving factors such as assumptions, expectations and behaviors. All of the above make it difficult to quantify and forecast trust accurately. In this paper, based on the theories of fuzzy recognition with feedback, SCGM(1, 1) model and Markov chain, we present a pattern of prediction making. The analysis and experimental computation show that this scheme is efficient in trust prediction for ad hoc networks.  相似文献   
139.
140.
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