全文获取类型
收费全文 | 20291篇 |
免费 | 3757篇 |
国内免费 | 2537篇 |
专业分类
电工技术 | 1025篇 |
综合类 | 2066篇 |
化学工业 | 986篇 |
金属工艺 | 361篇 |
机械仪表 | 1186篇 |
建筑科学 | 206篇 |
矿业工程 | 217篇 |
能源动力 | 90篇 |
轻工业 | 343篇 |
水利工程 | 102篇 |
石油天然气 | 386篇 |
武器工业 | 284篇 |
无线电 | 4237篇 |
一般工业技术 | 1193篇 |
冶金工业 | 950篇 |
原子能技术 | 41篇 |
自动化技术 | 12912篇 |
出版年
2024年 | 171篇 |
2023年 | 434篇 |
2022年 | 905篇 |
2021年 | 1028篇 |
2020年 | 1017篇 |
2019年 | 731篇 |
2018年 | 617篇 |
2017年 | 740篇 |
2016年 | 839篇 |
2015年 | 893篇 |
2014年 | 1299篇 |
2013年 | 1157篇 |
2012年 | 1471篇 |
2011年 | 1585篇 |
2010年 | 1293篇 |
2009年 | 1329篇 |
2008年 | 1389篇 |
2007年 | 1519篇 |
2006年 | 1339篇 |
2005年 | 1140篇 |
2004年 | 934篇 |
2003年 | 864篇 |
2002年 | 708篇 |
2001年 | 483篇 |
2000年 | 412篇 |
1999年 | 379篇 |
1998年 | 312篇 |
1997年 | 242篇 |
1996年 | 185篇 |
1995年 | 177篇 |
1994年 | 138篇 |
1993年 | 135篇 |
1992年 | 109篇 |
1991年 | 52篇 |
1990年 | 48篇 |
1989年 | 67篇 |
1988年 | 42篇 |
1987年 | 25篇 |
1986年 | 23篇 |
1985年 | 33篇 |
1984年 | 33篇 |
1983年 | 43篇 |
1982年 | 38篇 |
1981年 | 33篇 |
1980年 | 27篇 |
1979年 | 22篇 |
1978年 | 23篇 |
1977年 | 26篇 |
1976年 | 23篇 |
1974年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
31.
32.
The goal of face recognition is to distinguish persons via their facial images. Each person's images form a cluster, and a new image is recognized by assigning it to the correct cluster. Since the images are very high-dimensional, it is necessary to reduce their dimension. Linear discriminant analysis (LDA) has been shown to be effective at dimension reduction while preserving the cluster structure of the data. It is classically defined as an optimization problem involving covariance matrices that represent the scatter within and between clusters. The requirement that one of these matrices be nonsingular restricts its application to datasets in which the dimension of the data does not exceed the sample size. For face recognition, however, the dimension typically exceeds the number of images in the database, resulting in what is referred to as the small sample size problem. Recently, the applicability of LDA has been extended by using the generalized singular value decomposition (GSVD) to circumvent the nonsingularity requirement, thus making LDA directly applicable to face recognition data. Our experiments confirm that LDA/GSVD solves the small sample size problem very effectively as compared with other current methods. 相似文献
33.
Why are human observers particularly sensitive to human movement? Seven experiments examined the roles of visual experience and motor processes in human movement perception by comparing visual sensitivities to point-light displays of familiar, unusual, and impossible gaits across gait-speed and identity discrimination tasks. In both tasks, visual sensitivity to physically possible gaits was superior to visual sensitivity to physically impossible gaits, supporting perception-action coupling theories of human movement perception. Visual experience influenced walker-identity perception but not gait-speed discrimination. Thus, both motor experience and visual experience define visual sensitivity to human movement. An ecological perspective can be used to define the conditions necessary for experience-dependent sensitivity to human movement. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
34.
介绍了一种基于人工神经网络(ANN)的声目标识别系统,概述了用MATLAB专用工具箱对神经网络权值进行训练及仿真的过程,叙述了ANN目标识别系统的数字信号处理器(DSP)实时实现过程,并着重分析定点实现过程中程序变量的定标、非线性运算的实现、溢出的处理等关键步骤.对不同字长的识别结果进行比较表明,基于定点实时实现的系统数据保持很高的精度,可以得到与浮点处理相同的识别率. 相似文献
35.
36.
37.
Berrin-Wasserman Stacy; Winnick Wilma A.; Borod Joan C. 《Canadian Metallurgical Quarterly》2003,17(3):429
Does sentence generation and/or stimulus emotionality enhance verbal memory in patients with neurological impairment? This question was addressed by testing 40 patients with unilateral stroke (20 with left-brain and 20 with right-brain damage) and 20 healthy control participants for recall and recognition of 48 target words. During encoding, emotional and nonemotional words were either presented in sentences (read condition) or used to form sentences (generate condition). Both word emotionality and generative processing improved memory performance in all groups. The authors suggest that a similar influence (i.e., cognitive activation) underlies both of these memory-enhancing effects, although the putative origins of the 2 effects are quite different. Neuropsychological underpinnings and clinical implications of these phenomena are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
38.
In this article, we describe a knowledge-based controlled platform using program supervision techniques. This platform eases
the creation and the configuration of video surveillance systems. Several issues need to be addressed to provide a correct
system configuration: (1) to choose, among a library of programs, those which are best satisfying a given user request, (2)
to assign a correct value for each program parameter, (3) to evaluate performances and to guarantee a performance rate which
is satisfactory regarding end-user requirements. This platform is composed of three main components: the library of programs,
the knowledge base and the control component. The knowledge is either given by experts or learnt by the system. The control
is generic in the sense that it is independent of any application. To validate this platform, we have built and evaluated
six video surveillance systems which are featured with three properties: adaptability, reliability and real-time processing. 相似文献
39.
40.
把由非谐振环和凸面全反射镜构成的自滤波非稳腔应用于撞脉冲锁模Nd:YAG激光器,改善了光束的空间质量和输出稳定性,获得发散角为2倍衍射极限,能量50mJ,脉宽10ps的锁模脉冲,并与未加滤波小孔的CPM非稳腔的输出性能进行实验比较。, 相似文献