全文获取类型
收费全文 | 6721篇 |
免费 | 1216篇 |
国内免费 | 570篇 |
专业分类
化学 | 2092篇 |
晶体学 | 44篇 |
力学 | 524篇 |
综合类 | 47篇 |
数学 | 162篇 |
物理学 | 5638篇 |
出版年
2024年 | 2篇 |
2023年 | 37篇 |
2022年 | 130篇 |
2021年 | 136篇 |
2020年 | 150篇 |
2019年 | 99篇 |
2018年 | 139篇 |
2017年 | 251篇 |
2016年 | 288篇 |
2015年 | 253篇 |
2014年 | 476篇 |
2013年 | 535篇 |
2012年 | 390篇 |
2011年 | 469篇 |
2010年 | 332篇 |
2009年 | 447篇 |
2008年 | 523篇 |
2007年 | 475篇 |
2006年 | 422篇 |
2005年 | 417篇 |
2004年 | 382篇 |
2003年 | 334篇 |
2002年 | 281篇 |
2001年 | 243篇 |
2000年 | 234篇 |
1999年 | 195篇 |
1998年 | 165篇 |
1997年 | 155篇 |
1996年 | 117篇 |
1995年 | 110篇 |
1994年 | 76篇 |
1993年 | 46篇 |
1992年 | 53篇 |
1991年 | 48篇 |
1990年 | 26篇 |
1989年 | 20篇 |
1988年 | 11篇 |
1987年 | 12篇 |
1986年 | 7篇 |
1985年 | 3篇 |
1984年 | 5篇 |
1983年 | 3篇 |
1982年 | 1篇 |
1981年 | 5篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1957年 | 2篇 |
排序方式: 共有8507条查询结果,搜索用时 15 毫秒
61.
62.
63.
HU Yun & SHEN Yuliang Department of Mathematics Suzhou University Suzhou China 《中国科学A辑(英文版)》2006,(7)
We will be mainly concerned with some important fiber spaces over Teichmuller spaces, including the Bers fiber space and Teichmuller curve, establishing an isomorphism theorem between "punctured" Teichmuller curves and determining the biholomorphic isomorphisms of these fiber spaces. 相似文献
64.
65.
By introducing a four-layer step-index waveguide modeling, the characteristics of long-period fiber grating (LPFG) with an nm-thick film overlay, which has higher refractive index than that of fiber cladding are investigated in detail. The influence of both the overlay thickness and refractive index on the tuning ability of LPFG is analyzed. The numerical results demonstrate that spectral response of LPFG is divided into three distinct regions as the overlay deposition increases and the shift of resonant wavelength is drastic in some special thickness range. In conjunction with higher-order cladding mode coupling and fiber cladding etching, the sensitivity of LPFG to the overlay refractive index is enhanced significantly and over 120 nm resonant wavelength tunable range is achieved. 相似文献
66.
Dieter Petrak 《Particle & Particle Systems Characterization》2002,19(6):391-400
The objective of this study was to compare the measuring results of a fiber‐optical probe based on a modified spatial filtering technique with given size distributions of different test powders and also with particle velocity values of laser Doppler measurements. Fiber‐optical spatial filtering velocimetry was modified by fiber‐optical spot scanning in order to determine simultaneously the size and the velocity of particles. The fiber‐optical probe system can be used as an in‐line measuring device for sizing of particles in different technical applications. Spherical test particles were narrow‐sized glass beads in the range 30–100 μm and irregularly shaped test particles were limestone particles in the range 10–600 μm. Particles were dispersed by a brush disperser and the measurements were carried out at a fixed position in a free particle‐laden air stream. Owing to the measurement of chord lengths and to the influence of diffraction and divergent angle, the probe results show differences from the given test particle sizes. Owing to the particle‐probe collisions, the mean velocity determined by the probe is smaller than the laser Doppler mean velocity. 相似文献
67.
68.
An acoustic pulse propagating on a two-mode fiber can act as a beam splitter in a scanning interferometer. When this device
is employed in white-light interferometry, the effects of distributed coupling and dispersive interferometer arms need to
be considered. A theory suitable for treating acousto-optic interaction of partially coherent light in a moving interaction
region was developed. It was found that differential optical dispersion should be negligible and the acoustic pulse length
short. Also the coherence time should be short but long compared to the intermodal group delay difference over a pulse length.
Experiments with long acoustic pulses were performed, and fairly good agreement with theory was obtained. 相似文献
69.
时分复用倍乘光脉冲重复率的新型光纤耦合器环状连接法分析 总被引:2,自引:0,他引:2
提出并详细分析了一种基于时分复用技术倍乘光脉冲重复率的方法:在2×2光纤耦合器的一个输入口与一个输出口间,接入时延为脉冲列半周期奇数倍的一段光纤使之形成环状连接循环耦合,而在另一输出口获得光脉冲。详细分析了该系统中光纤耦合器耦合比、插入损耗、时延光纤长度的要求,偏差的影响及其调节法,给出了理论公式、结果的计算机模拟与实验介绍;与经典的马赫陈德尔干涉仪接法及近年提出的Sagnac环接法进行了比较。该方法特别适用于对窄脉冲列进行串接复用实现重复率的多次倍乘,从而得到数千兆赫至上百千兆赫的高重复率光脉冲 相似文献
70.
Kiyoshi Kurosawa 《Optical Review》1997,4(1):A38-A44
This paper describes development of the optical current transducers using flint glass fiber as the Faraday effect sensing
element. Excellent polarization properties of the fiber with low birefringence are described, and the design and test data
of a current transducer using the fiber manufactured for use in electric power facilities are reviewed. Experimental results
on flexible characteristics of a scheme with round trip light transmission in the fiber is also reported. 相似文献