全文获取类型
收费全文 | 239356篇 |
免费 | 49288篇 |
国内免费 | 45943篇 |
专业分类
化学 | 113432篇 |
晶体学 | 3666篇 |
力学 | 11050篇 |
综合类 | 2174篇 |
数学 | 22448篇 |
物理学 | 91043篇 |
无线电 | 90774篇 |
出版年
2024年 | 1418篇 |
2023年 | 4299篇 |
2022年 | 6733篇 |
2021年 | 7281篇 |
2020年 | 6931篇 |
2019年 | 7305篇 |
2018年 | 6892篇 |
2017年 | 8787篇 |
2016年 | 9082篇 |
2015年 | 11366篇 |
2014年 | 12896篇 |
2013年 | 16176篇 |
2012年 | 18275篇 |
2011年 | 19220篇 |
2010年 | 21019篇 |
2009年 | 21251篇 |
2008年 | 15777篇 |
2007年 | 14661篇 |
2006年 | 13620篇 |
2005年 | 12078篇 |
2004年 | 10884篇 |
2003年 | 8182篇 |
2002年 | 7598篇 |
2001年 | 7443篇 |
2000年 | 6791篇 |
1999年 | 5412篇 |
1998年 | 4065篇 |
1997年 | 3561篇 |
1996年 | 3822篇 |
1995年 | 4066篇 |
1994年 | 3947篇 |
1993年 | 3941篇 |
1992年 | 3422篇 |
1991年 | 2942篇 |
1990年 | 2457篇 |
1989年 | 2447篇 |
1988年 | 2213篇 |
1987年 | 1463篇 |
1986年 | 1469篇 |
1985年 | 1086篇 |
1984年 | 1175篇 |
1983年 | 525篇 |
1982年 | 1010篇 |
1981年 | 837篇 |
1980年 | 851篇 |
1979年 | 620篇 |
1978年 | 573篇 |
1977年 | 664篇 |
1976年 | 1071篇 |
1972年 | 556篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
151.
Graham A. Jullien Wenzhe Luo Neil M. Wigley 《The Journal of VLSI Signal Processing》1996,14(2):207-220
This paper discusses strategies for implementing DSP systems using residue replication. The theory, recently introduced by two of the authors, uses formal polynomial ring mappings, from binary representations, to direct product ring implementation of integer processing arrays. The mapping produces completely independent computational arrays each computing over the same ring. This paper describes an architecture and processing array to implement, and take advantage of, the special computational ring structures that result from the mapping. A brief review of the theory and mapping techniques, is followed by the discussion of the architecture and VLSI design of an efficient inner product processing array using Fermat Primes. 相似文献
152.
Dynamic Programming (DP) applies to many signal and image processing applications including boundary following, the Viterbi algorithm, dynamic time warping, etc. This paper presents an array processor implementation of generic dynamic programming. Our architecture is a SIMD array attached to a host computer. The processing element of the architecture is based on an ASIC design opting for maximum speed-up. By adopting a torus interconnection network, a dual buffer structure, and a multilevel pipeline, the performance of the DP chip is expected to reach the order of several GOPS. The paper discusses both the dedicated hardware design and the data flow control of the DP chip and the total array.This work was supported in part by the NATO, Scientific and Environmental Affairs Division, Collaborative Research Grant SA.5-2-05(CRG.960201)424/96/JARC-501. 相似文献
153.
154.
In theory, both polarity and steric hindrance are basic factors which affect molecular interactions. To investigate the optical properties and steric structures of chiral compounds having different chiral moieties which affect the wavelength of light reflection in liquid crystal (LC) cells, a series of novel chiral compounds and azobenzene derivatives were synthesized. The liquid crystalline phases of the compounds were identified using small angle X-ray diffraction, differential scanning calorimetry and polarizing optical microscopy. Cholesteric LC cells with various synthesized chiral dopants which selectively reflect visible light were first prepared, the photochemical switching behaviour of colours was then investigated, with special reference to the change in transmittance in cholesteric LC cells containing an azobenzene derivative as a photoisomerizable guest molecule. Reversible isomerization of azobenzene molecules occurred in the cholesteric systems, resulting in a depression of TChI and a shift of the selectively reflected wavelength. We discuss the photochemically driven change in the helical pitch of the cholesteric LCs with respect to structural effects involving the chiral moieties. Molecular interactions caused by the added dopants, reliability and stability of the photoisomerization, and UV irradiation effects on the cholesteric LC cells were also investigated. A real image was recorded through a mask on a cholesteric LC cell fabricated in this investigation. 相似文献
155.
156.
The Mathematical Intelligencer encourages comments about the material in this issue. Letters to the editor should be sent
to either of the editors-in-chief, Chandler Davis or Marjorie Senechal. 相似文献
157.
MSTP在3G的应用 总被引:2,自引:0,他引:2
讨论了MSTP的技术特点,指出MSTP能高效可靠传输各种业务,并结合3G网络的业务发展以及3G传输关注的接口,提出采用引入ATM功能的MSTP技术解决3G传输网络的方案. 相似文献
158.
本文采用连续型Hopfield神经网络(HNN)模型应用于有限角CT图像重建,该重建算法将两种优化准则转化为模型的能量系数求取图像重建的最优解,通过数值模拟,考察了该重建算法和抗噪性能,均得到了良好的结果。 相似文献
159.
Q. Gong R. N tzel P.J. van Veldhoven T.J. Eijkemans J.H. Wolter 《Journal of Crystal Growth》2005,280(3-4):413-418
We report on the shape transition from InAs quantum dashes to quantum dots (QDs) on lattice-matched GaInAsP on InP(3 1 1)A substrates. InAs quantum dashes develop during chemical-beam epitaxy of 3.2 monolayers InAs, which transform into round InAs QDs by introducing a growth interruption without arsenic flux after InAs deposition. The shape transition is solely attributed to surface properties, i.e., increase of the surface energy and symmetry under arsenic deficient conditions. The round QD shape is maintained during subsequent GaInAsP overgrowth because the reversed shape transition from dot to dash is kinetically hindered by the decreased ad-atom diffusion under arsenic flux. 相似文献
160.