全文获取类型
收费全文 | 144655篇 |
免费 | 21538篇 |
国内免费 | 16431篇 |
专业分类
化学 | 77071篇 |
晶体学 | 1241篇 |
力学 | 6312篇 |
综合类 | 714篇 |
数学 | 13744篇 |
物理学 | 41908篇 |
无线电 | 41634篇 |
出版年
2024年 | 576篇 |
2023年 | 3322篇 |
2022年 | 4449篇 |
2021年 | 5429篇 |
2020年 | 5463篇 |
2019年 | 4961篇 |
2018年 | 4666篇 |
2017年 | 4416篇 |
2016年 | 6260篇 |
2015年 | 6645篇 |
2014年 | 8191篇 |
2013年 | 10387篇 |
2012年 | 12207篇 |
2011年 | 12410篇 |
2010年 | 9142篇 |
2009年 | 9039篇 |
2008年 | 9403篇 |
2007年 | 8454篇 |
2006年 | 8084篇 |
2005年 | 7065篇 |
2004年 | 5217篇 |
2003年 | 4347篇 |
2002年 | 3943篇 |
2001年 | 3338篇 |
2000年 | 2985篇 |
1999年 | 3171篇 |
1998年 | 2678篇 |
1997年 | 2296篇 |
1996年 | 2281篇 |
1995年 | 2055篇 |
1994年 | 1742篇 |
1993年 | 1423篇 |
1992年 | 1255篇 |
1991年 | 1063篇 |
1990年 | 905篇 |
1989年 | 648篇 |
1988年 | 495篇 |
1987年 | 404篇 |
1986年 | 416篇 |
1985年 | 309篇 |
1984年 | 244篇 |
1983年 | 210篇 |
1982年 | 154篇 |
1981年 | 99篇 |
1980年 | 71篇 |
1979年 | 37篇 |
1978年 | 32篇 |
1976年 | 30篇 |
1975年 | 29篇 |
1957年 | 27篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
961.
GPRS全称通用分组无线业务,它在改进了现有GSM系统后能实现高速的数据传输。首先对GPRS系统做了简单介绍,然后在此基础上详细介绍了GPRS的板间切换在CPX8216硬件平台上的实现方法。 相似文献
962.
963.
964.
Wang Yongqian Liao Xianbo Diao Hongwei Cheng Wenchao Li Guohua Chen Changyong Zhang Shibin Xu Yanyue Chen Weide Kong Guanglin 《中国科学A辑(英文版)》2002,45(10):1320-1328
A set of a-SiOx:H (0.52 <x< 1.58) films are fabricated by plasma-enhanced-chemical-vapor-deposition (PECVD) method at the substrate temperature
of 250°C. The microstructure and local bonding configurations of the films are investigated in detail using micro-Raman scattering,
X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR). It is found that the films are
structural inhomogeneous, with five phases of Si, Si2O:H, SiO:H, Si2O3:H and SiO2 that coexist. The phase of Si is composed of nonhydrogenated amorphous silicon (a-Si) clusters that are spatially isolated.
The average size of the clusters decreases with the increasing oxygen concentration x in the films. The results indicate that
the structure of the present films can be described by a multi-shell model, which suggests that a-Si cluster is surrounded
in turn by the subshells of Si2O:H, SiO:H, Si2O3:H, and SiO2. 相似文献
965.
966.
967.
This paper discusses a kind of optimization problem with linear complementarity constraints, and presents a sequential quadratic
programming (SQP) algorithm for solving a stationary point of the problem. The algorithm is a modification of the SQP algorithm
proposed by Fukushima et al. [Computational Optimization and Applications, 10 (1998),
5-34], and is based on a reformulation of complementarity condition as a system of linear equations. At each iteration,
one quadratic programming and one system of equations needs to be solved, and a curve search is used to yield the step size.
Under some appropriate assumptions, including the lower-level strict complementarity, but without the upper-level strict
complementarity for the inequality constraints, the algorithm is proved to possess strong convergence and superlinear convergence.
Some preliminary numerical results are reported. 相似文献
968.
Hui-Ling Li De-Jiang Qi Qing-Quan Jiang Shu-Zheng Yang 《International Journal of Theoretical Physics》2006,45(12):2428-2436
An extension of the Parikh-Wilczek's semi-classical quantum tunneling method, the tunneling radiation of the charged particle from a torus-like black hole is investigated. Difference from the uncharged mass-less particle, the geodesics of the charged massive particle tunneling from the black hole is not light-like, but determined by the phase velocity. The derived result shows that the tunneling rate depends on the emitted particle's energy and electric charge, and takes the same functional form as uncharged particle. It proves also that the exact emission spectrum is not strictly pure thermal, but is consistent with the underlying unitary theory.
PACS Numbers: 04.70.Dy, 97.60.Lf, 05.30.Ch. 相似文献
969.
970.
研究了支撑矢量机的分类机理,并利用支撑矢量机对雷达目标一维像进行了识别.识别的结果表明了该方法的优越性,并显示它可以对残缺不全的样本进行识别. 相似文献