全文获取类型
收费全文 | 13796篇 |
免费 | 1341篇 |
国内免费 | 868篇 |
专业分类
化学 | 3438篇 |
晶体学 | 163篇 |
力学 | 574篇 |
综合类 | 51篇 |
数学 | 213篇 |
物理学 | 11566篇 |
出版年
2024年 | 7篇 |
2023年 | 80篇 |
2022年 | 171篇 |
2021年 | 167篇 |
2020年 | 225篇 |
2019年 | 197篇 |
2018年 | 255篇 |
2017年 | 422篇 |
2016年 | 525篇 |
2015年 | 451篇 |
2014年 | 1069篇 |
2013年 | 971篇 |
2012年 | 683篇 |
2011年 | 1185篇 |
2010年 | 798篇 |
2009年 | 992篇 |
2008年 | 1021篇 |
2007年 | 1025篇 |
2006年 | 822篇 |
2005年 | 693篇 |
2004年 | 631篇 |
2003年 | 552篇 |
2002年 | 480篇 |
2001年 | 453篇 |
2000年 | 367篇 |
1999年 | 349篇 |
1998年 | 310篇 |
1997年 | 223篇 |
1996年 | 187篇 |
1995年 | 146篇 |
1994年 | 102篇 |
1993年 | 76篇 |
1992年 | 68篇 |
1991年 | 63篇 |
1990年 | 51篇 |
1989年 | 36篇 |
1988年 | 26篇 |
1987年 | 32篇 |
1986年 | 15篇 |
1985年 | 9篇 |
1984年 | 18篇 |
1983年 | 8篇 |
1982年 | 4篇 |
1981年 | 8篇 |
1980年 | 7篇 |
1979年 | 4篇 |
1978年 | 4篇 |
1974年 | 3篇 |
1973年 | 5篇 |
1957年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
121.
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
122.
M.A.C. Potenza M.D. Alaimo D. Pescini D. Magatti F. Ferri M. Giglio 《Optics and Lasers in Engineering》2006,44(7):722
We show that the time evolution of near-field scattering speckles, originated by a fluid suspension of particles, provides information about the velocity field in the fluid. This information can be extracted from a statistical analysis of speckle fields taken at different times, either by measuring their cross-correlation function or by recovering the power spectrum corresponding to the difference between the two speckle fields. Experimental data are in accordance to the expected behaviors. The results are independent of the scatterer's size, allowing one to exploit the technique also with sub-wavelength tracking particles. 相似文献
123.
124.
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
125.
126.
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
127.
Kefu Fu Kevin Henbest Yufen J. Zhang Shane Valentin Ya-Ping Sun 《Journal of photochemistry and photobiology. A, Chemistry》2002,150(1-3):143-152
Dimeric fullerene macromolecules were prepared via the complexation of two fullerenylated 2,2′:6′,2″-terpyridine ligands with Fe(II) and Co(II) ions. The solubility of these macromolecules in some organic solvents allowed both their structural characterization and a study of their optical properties. The electronic absorption and emission of the macromolecules in solution were evaluated; and the results indicated no meaningful ground-state and excited singlet state intramolecular charge transfer interactions. However, the laser flash photolysis results could be explained in terms of the electron transfer quenching of the excited triplet methanofullerene moiety by the center metal–ligand complex in the macromolecules. The optical limiting properties of the macromolecules in solution were also investigated in comparison with those of the ligands for an evaluation of the complexation effects. 相似文献
128.
光学光刻是目前超大规模集成电路(VLSI)制备中主要的微米和亚微米的图形加工技术,这一技术将继续保持其主导地位成为90年代VLSI发展的关键。本文综述了近年来光学光刻工艺的发展,主要介绍了G线(436nm)、Ⅰ线(365nm)和准分子激光光刻的现状,并对实现高的光学光刻分辨率所必须解决的透镜设计、套准精度和像场面积等问题作了详细描述。最后展望了发展方向、 相似文献
129.
130.
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