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   568篇
  免费   20篇
  国内免费   7篇
化学   8篇
力学   4篇
综合类   1篇
数学   112篇
物理学   40篇
无线电   430篇
  2023年   7篇
  2022年   8篇
  2021年   8篇
  2020年   12篇
  2019年   13篇
  2018年   4篇
  2017年   14篇
  2016年   30篇
  2015年   17篇
  2014年   34篇
  2013年   45篇
  2012年   25篇
  2011年   33篇
  2010年   28篇
  2009年   23篇
  2008年   35篇
  2007年   32篇
  2006年   29篇
  2005年   15篇
  2004年   22篇
  2003年   17篇
  2002年   21篇
  2001年   9篇
  2000年   12篇
  1999年   10篇
  1998年   25篇
  1997年   11篇
  1996年   9篇
  1995年   6篇
  1994年   2篇
  1993年   7篇
  1992年   6篇
  1991年   5篇
  1990年   5篇
  1989年   5篇
  1988年   5篇
  1987年   1篇
  1986年   1篇
  1984年   2篇
  1982年   1篇
  1974年   1篇
排序方式: 共有595条查询结果,搜索用时 0 毫秒
101.
Block matching has been used for motion estimation and motion compensation in the Audio and Video Standard (AVS) for years. While having an acceptable performance in describing motion between frames, it requires quite a few bits to represent the motion vectors. In certain circumstances, the use of global motion estimation and compensation would perform equally well or even better than the block matching in terms of motion accuracy, while it results in the coding of global motion model parameters. In this letter, we modify an AVS coder by adding (1) six global motion model parameters to the frame header, and (2) mode selection among INTRA, SKIP, INTER-16×16, INTER-16×8, INTER-8×16, INTER-8×8, and Global Motion Compensation (GMC) modes by Lagrange optimal rate-distortion criteria. Simulation results demonstrate that over 0.1dB improvement in PSNR is obtained compared to the AVS coder for an average coded P-frame with the same bitrate.  相似文献   
102.
Exploring new synaptic electronic devices that combine computing and memory is a promising strategy that fundamentally approaches intelligent machines. In this study, the multilevel resistive switching and synaptic behaviors of a MnO-based device is studied. The device is composed of Al/MnO/Ni sandwich structure, has stable resistance switching characteristics, has continuous nonvolatile memory state, can be used as electrically programmable and erasable analog memory. The gradual conductance modulation is realized by changing the compliance current and the maximum scanning voltage. The Al/MnO/Ni devices successfully mimic the basic functions of synapses, including the paired-pulse facilitation, spike-rate-dependent plasticity, excitatory postsynaptic current, short-term plasticity, long-term plasticity, and sike-timing-dependent plasticity.  相似文献   
103.
High Efficiency Video Coding (HEVC) surpasses its predecessors in encoding efficiency by introducing new coding tools at the cost of an increased encoding time-complexity. The Coding Tree Unit (CTU) is the main building block used in HEVC. In the HEVC standard, frames are divided into CTUs with the predetermined size of up to 64 × 64 pixels. Each CTU is then divided recursively into a number of equally sized square areas, known as Coding Units (CUs). Although this diversity of frame partitioning increases encoding efficiency, it also causes an increase in the time complexity due to the increased number of ways to find the optimal partitioning. To address this complexity, numerous algorithms have been proposed to eliminate unnecessary searches during partitioning CTUs by exploiting the correlation in the video. In this paper, existing CTU depth decision algorithms for HEVC are surveyed. These algorithms are categorized into two groups, namely statistics and machine learning approaches. Statistics approaches are further subdivided into neighboring and inherent approaches. Neighboring approaches exploit the similarity between adjacent CTUs to limit the depth range of the current CTU, while inherent approaches use only the available information within the current CTU. Machine learning approaches try to extract and exploit similarities implicitly. Traditional methods like support vector machines or random forests use manually selected features, while recently proposed deep learning methods extract features during training. Finally, this paper discusses extending these methods to more recent video coding formats such as Versatile Video Coding (VVC) and AOMedia Video 1(AV1).  相似文献   
104.
The Wyner-Ziv distributed video coding scheme is characterized for its intraframe encoder and interframe decoder which can also approach the efficiency of an interframe encoder-decoder system. In Wyner-Ziv residual coding of video, the residual of a frame with respect to a reference frame is Wyner-Ziv encoded, which can reduces the input entropy and leads to a higher coding efficiency than directly encoding the original frame. In this paper, we propose a new approach of residual coding combined with Region Of Interest (ROI) extraction. Experimental results show that, the proposed scheme achieves better rate-distortion performance compared to conventional Wyner-Ziv coding scheme.  相似文献   
105.
In this paper, we outline the foundations of a general global optimisation strategy for the solution of multilevel hierarchical and general decentralised multilevel problems, based on our recent developments on multi-parametric programming and control theory. The core idea is to recast each optimisation subproblem, present in the hierarchy, as a multi-parametric programming problem, with parameters being the optimisation variables belonging to the remaining subproblems. This then transforms the multilevel problem into single-level linear/convex optimisation problems. For decentralised systems, where more than one optimisation problem is present at each level of the hierarchy, Nash equilibrium is considered. A three person dynamic optimisation problem is presented to illustrate the mathematical developments.  相似文献   
106.
We had presented a simple technique, which is based on the theory of Diophantine equation, for parametrization of popular biorthogonal wavelet filter banks (BWFBs) having the linear phase and arbitrary multiplicity of vanishing moments (VMs), and constructed a type of parametric BWFBs with one free parameter [15]. Here we generalize this technique to the case of two parameters, and construct a type of parametric BWFBs with two free parameters. The closed-form parameter expressions of the BWFBs are derived, with which any two-parameter family of BWFBs having preassigned VMs can be constructed, and six families, i.e., 9/11, 10/10, 13/11, 10/14, 17/11, and 10/18 families, are considered here. Two parameters provide two degrees of freedom to optimize the resulting BWFBs with respect to other criteria. In particular, in each family, three specific rational-coefficient BWFBs with attractive features are obtained by adjusting the parameters: the first is not only very close to a quadrature mirror filter (QMF) bank, but has optimum coding gain; the second possesses characteristics that are close to the irrational BWFB with maximum VMs by Cohen et al.; and the last which has binary coefficients can realize a multiplication-free discrete wavelet transform. In addition, two BWFBs are systematically verified to exhibit performance competitive to several state-of-the-art BWFBs for image compression, and yet require lower computational costs. This work was supported by the Natural Science Foundation of Jiangsu province, China under Grant 07KJD520005.  相似文献   
107.
Fake pharmaceuticals inflicts severely upon people(?)~-s health through its circulation in markets.To strengthen the supervision of the pharmaceutical market,China is improving and is perfecting its national coding system in the field of pharmaceuticals. Bar-code tag and IC tag are available to the coding system.This paper summarizes the significance of IC tag to the supervision of pharmaceuticals and gives us a strategically general prospect of pharmaceutical supervision.  相似文献   
108.
面向无线体域网(WBAN)传输环境,该文主要论述信道编码与联合信源信道编码系统的码字设计。针对物理层的低功耗和高可靠传输需求,从低密度奇偶校验(LDPC)码的优化设计角度展开,主要在信道模型分类、传输系统构建、技术挑战与解决方案、信道适配性编码设计这4个层面进行梳理和总结。最后,对WBAN环境下LDPC码优化设计的未来研究工作进行展望,为构建下一代通信技术提供参考。  相似文献   
109.
Data in social and behavioral sciences are often hierarchically organized. Special statistical procedures have been developed to analyze such data while taking into account the resulting dependence of observations. Most of these developments require a multivariate normality distribution assumption. It is important to know whether normal theory-based inference can still be valid when applied to nonnormal hierarchical data sets. Using an analytical approach for balanced data and numerical illustrations for unbalanced data, this paper shows that the likelihood ratio statistic based on the normality assumption is asymptotically robust for many nonnormal distributions. The result extends the scope of asymptotic robustness theory that has been established in different contexts.  相似文献   
110.
We show that there are no complete 44-caps in AG(5, 3). We then use this result to prove that the maximal size for a cap in AG(6, 3) is equal to 112, and that the 112-caps in AG(6, 3) are unique up to affine equivalence.   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