全文获取类型
收费全文 | 128642篇 |
免费 | 12576篇 |
国内免费 | 7040篇 |
学科分类
工业技术 | 148258篇 |
出版年
2024年 | 449篇 |
2023年 | 2113篇 |
2022年 | 4015篇 |
2021年 | 5885篇 |
2020年 | 4418篇 |
2019年 | 3435篇 |
2018年 | 3892篇 |
2017年 | 4184篇 |
2016年 | 3922篇 |
2015年 | 5553篇 |
2014年 | 6840篇 |
2013年 | 8046篇 |
2012年 | 9358篇 |
2011年 | 9942篇 |
2010年 | 8623篇 |
2009年 | 8258篇 |
2008年 | 8079篇 |
2007年 | 7389篇 |
2006年 | 6962篇 |
2005年 | 5979篇 |
2004年 | 4188篇 |
2003年 | 3252篇 |
2002年 | 3006篇 |
2001年 | 2647篇 |
2000年 | 2683篇 |
1999年 | 2785篇 |
1998年 | 2167篇 |
1997年 | 1799篇 |
1996年 | 1754篇 |
1995年 | 1487篇 |
1994年 | 1227篇 |
1993年 | 881篇 |
1992年 | 710篇 |
1991年 | 489篇 |
1990年 | 422篇 |
1989年 | 355篇 |
1988年 | 266篇 |
1987年 | 180篇 |
1986年 | 134篇 |
1985年 | 88篇 |
1984年 | 66篇 |
1983年 | 46篇 |
1982年 | 58篇 |
1981年 | 46篇 |
1980年 | 44篇 |
1979年 | 17篇 |
1976年 | 16篇 |
1974年 | 13篇 |
1973年 | 11篇 |
1959年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
A simple and elegant tracking algorithm called Centroid Iteration algorithm is proposed. It employs a new Background-Weighted
similarity measure which can greatly reduce the influence from the pixels shared by the target template and background on
localization. Experiments demonstrated the Background-Weighted measure performs much better than the other similarity measures
like Kullback–Leibler divergence, Bhattacharyya coefficient and so on. It has been proved that this measure can compute the
similarity value contribution of each pixel in the target candidate, based on which, a new target search method called Centroid
Iteration is constructed. The convergence of the method has been demonstrated. Theory analysis and visual experiments both
validated the new algorithm. 相似文献
992.
Faa‐Jeng Lin Jonq‐Chin Hwang Kuang‐Hsiung Tan Zong‐Han Lu Yung‐Ruei Chang 《Asian journal of control》2012,14(3):768-783
An intelligent control for a stand‐alone doubly‐fed induction generator (DFIG) system using a proportional‐integral‐derivative neural network (PIDNN) is proposed in this study. This system can be applied as a stand‐alone power supply system or as the emergency power system when the electricity grid fails for all sub‐synchronous, synchronous, and super‐synchronous conditions. The rotor side converter is controlled using field‐oriented control to produce 3‐phase stator voltages with constant magnitude and frequency at different rotor speeds. Moreover, the grid side converter, which is also controlled using field‐oriented control, is primarily implemented to maintain the magnitude of the DC‐link voltage. Furthermore, the intelligent PIDNN controller is proposed for both the rotor and grid side converters to improve the transient and steady‐state responses of the DFIG system for different operating conditions. Both the network structure and online learning algorithm are introduced in detail. Finally, the feasibility of the proposed control scheme is verified through experimentation. Copyright © 2011 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society 相似文献
993.
Qishi Wu Mengxia Zhu Yi Gu Patrick Brown Xukang Lu Wuyin Lin Yangang Liu 《Journal of Grid Computing》2012,10(3):367-393
Next-generation scientific applications feature complex workflows comprised of many computing modules with intricate inter-module dependencies. Supporting such scientific workflows in wide-area networks especially Grids and optimizing their performance are crucial to the success of collaborative scientific discovery. We develop a Scientific Workflow Automation and Management Platform (SWAMP), which enables scientists to conveniently assemble, execute, monitor, control, and steer computing workflows in distributed environments via a unified web-based user interface. The SWAMP architecture is built entirely on a seamless composition of web services: the functionalities of its own are provided and its interactions with other tools or systems are enabled through web services for easy access over standard Internet protocols while being independent of different platforms and programming languages. SWAMP also incorporates a class of efficient workflow mapping schemes to achieve optimal end-to-end performance based on rigorous performance modeling and algorithm design. The performance superiority of SWAMP over existing workflow mapping schemes is justified by extensive simulations, and the system efficacy is illustrated by large-scale experiments on real-life scientific workflows for climate modeling through effective system implementation, deployment, and testing on the Open Science Grid. 相似文献
994.
Wei Qian Shen Cong Tao Li Shumin Fei 《International Journal of Control, Automation and Systems》2012,10(6):1146-1152
The paper is concerned with the stability of linear systems with interval time-varying delay. Through constructing a new augmented Lyapunov-Krasovskii functional (LKF) which contains some quadruple-integral terms and estimating the time derivative of the LKF less conservatively, new stability criteria are derived without introducing any free matrices. Moreover, by proving the positive definiteness of the LKF with some integral inequalities, the constraints on some functional parameters are relaxed and the conservatism of the obtained results are further reduced. Numerical examples are also given to demonstrate the effectiveness and reduced conservatism of the obtained results. 相似文献
995.
以耐火粘土、高矾土及滑石为原料研制了堇青石基陶瓷材料,并对其组织和性能尤其是抗热震性进行了研究。结果表明,堇青石基上分布着针状莫来石的材料具有更高的抗热震性。对评价换热器用陶瓷材料抗热震性参数进行了讨论,指出抗热震损伤参数R″″更适合于作为优选陶瓷换热器用材质的指标。 相似文献
996.
A twin-plane re-entrant corner effect (TPRE) in growth of chemical vapour deposited (CVD) -SiC is described by the film and particles of gas-phase homogeneous nucleation. The structural morphology has been characterized by scanning electron microscopy and transmission electron microscopy. Morphological characteristics of the deposited crystals, such as triangularity, hexagons or facets have been explained in terms of the re-entrant corner effect at twin junctions, which were proposed as preferential growth sites for perfect crystals. For real deposits, screw dislocations and/or the re-entrant corner effect are not expected to be compatible. The majority of chemical vapour deposited SiC crystals have a high defect density comprised of {111} twins and dislocations associated with the process variables. Infrared transmission spectra and electron spectroscopy of chemical analysis indicated that the major chemical bonds of CVD -SiC were Si-C and C-H bonds. The positions of the 1s or 2p corelevel peaks for deposits are described. 相似文献
997.
998.
999.
1000.
随着数字图像处理和模式识别技术的发展,字符识别技术得到了广泛的应用。二值化技术作为字符预处理的一个重要环节,对后续的字符分割和特征提取有着很大的影响。本文针对字符图像的特点,提出了一种改进的基于直方图特征和形态学处理的Otsu二值化算法。仿真表明,该算法在减少运算量的同时,可以有效处理字符笔划残缺造成的干扰,并增强字符的连通性。 相似文献