全文获取类型
收费全文 | 31093篇 |
免费 | 4779篇 |
国内免费 | 2692篇 |
专业分类
化学 | 3839篇 |
晶体学 | 85篇 |
力学 | 4518篇 |
综合类 | 636篇 |
数学 | 15983篇 |
物理学 | 13503篇 |
出版年
2024年 | 55篇 |
2023年 | 290篇 |
2022年 | 538篇 |
2021年 | 599篇 |
2020年 | 750篇 |
2019年 | 714篇 |
2018年 | 749篇 |
2017年 | 934篇 |
2016年 | 1036篇 |
2015年 | 813篇 |
2014年 | 1612篇 |
2013年 | 2016篇 |
2012年 | 1697篇 |
2011年 | 2067篇 |
2010年 | 1776篇 |
2009年 | 2052篇 |
2008年 | 2087篇 |
2007年 | 2189篇 |
2006年 | 1969篇 |
2005年 | 1889篇 |
2004年 | 1649篇 |
2003年 | 1519篇 |
2002年 | 1236篇 |
2001年 | 1154篇 |
2000年 | 1030篇 |
1999年 | 874篇 |
1998年 | 815篇 |
1997年 | 717篇 |
1996年 | 545篇 |
1995年 | 469篇 |
1994年 | 391篇 |
1993年 | 325篇 |
1992年 | 279篇 |
1991年 | 245篇 |
1990年 | 218篇 |
1989年 | 172篇 |
1988年 | 155篇 |
1987年 | 126篇 |
1986年 | 96篇 |
1985年 | 111篇 |
1984年 | 93篇 |
1983年 | 61篇 |
1982年 | 85篇 |
1981年 | 77篇 |
1980年 | 51篇 |
1979年 | 47篇 |
1978年 | 35篇 |
1977年 | 30篇 |
1976年 | 31篇 |
1973年 | 27篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Veli B. Shakhmurov 《Journal of Mathematical Analysis and Applications》2007,327(2):1182-1201
The nonlocal boundary value problems for anisotropic partial differential-operator equations with a dependent coefficients are studied. The principal parts of the appropriate generated differential operators are nonself-adjoint. Several conditions for the maximal regularity and the fredholmness in Banach-valued Lp-spaces of these problems are given. These results permit us to establish that the inverse of corresponding differential operators belongs to Schatten q-class. Some spectral properties of the operators are investigated. In applications, the nonlocal BVP's for quasielliptic partial differential equations and for systems of quasielliptic equations on cylindrical domain are studied. 相似文献
102.
Fluorescence line narrowing (FLN) spectroscopy was used to study the role of the polypeptide chain in influencing the spectrum of Zn-substituted cytochrome c (Zn cyt c) and metal-free cyt c (porphyrin cyt c). For both derivatives the spectra show characteristics of relaxed fluorescence from an inhomogeneously broadened sample. Zero phonon lines and phonon wings can be clearly distinguished, and vibrational frequencies of the ground and excited states were identified. The inhomogeneous distribution width for porphyrin cyt c is slightly wider than that of Zn cyt c and a second population of molecules was apparent in the porphyrin cyt c. The phonon coupling was greater for Zn cyt c than for porphyrin cyt c, which may be due to the extra coupling to the polypeptide chain by metal ligation.This work has been done in partial fulfillment of the requirements for the Doctor of Philosophy degree. 相似文献
103.
104.
A. Gerasimov 《Journal of statistical physics》1993,70(3-4):939-948
The analysis is carried out of the response of the center of gravity (dipole moment) of the distribution of noninteracting thermalized nonlinear oscillators to a sinusoidal driving force. Heat bath coupling is modeled by damping and noise. The driving is weak, but the frequency is resonant, so that there is a nonlinear resonance in the phase space. The response has a linear part that can be obtained from the perturbation analysis and a small nonlinear correction that is specific for the resonant structure. 相似文献
105.
106.
Shayesteh S. Farjami B. Soltani M. A. Solimany 《International Journal of Infrared and Millimeter Waves》2002,23(12):1691-1697
We present and discuss infrared magnetoplasma reflectivity and surface polariton modes in Ga1–xNxAs. It assumed that the sample is characterized by a magnetoplasma dielectric tensor. Surface polariton dispersion for two component magnetoplasma was calculated from reflectivity spectra data. We detect transverse optic phonon of GaN sublattice in 470 cm-1. The origin of sharp feature in p-polarization reflectivity about 300 cm–1 as well as LO phonon frequency of GaAs sublattice is due to Brewster mode. An interesting feature of surface modes in Voigt geometry is nonreciprocalicity, which means that the frequency changes when the direction of propagation is reversed. Also, the infrared magnetoplasma reflectivity of GaNAs should be providing determination of the electrons and heavy holes effective mass and carrier's concentration. 相似文献
107.
Laser gas-assisted material processing finds wide application in industry. The modelling of heating, elastic response of the substrate material, and the wave analysis gives insight into the laser workpiece interaction. In the present study, laser gas-assisted heating of steel is considered. The normal component of the thermal stress is taken as the source of load for the flexural wave generation in the material. The flexural wave generated is simulated and the wave characteristics are analyzed at four locations at the workpiece surface. The numerical scheme employing a control volume approach is introduced when solving the governing equations of flow and heat transfer while finite element and spectran element methods are used when solving the stress and wave equations. It is found that the normal component of the stress is tensile. The dispersion effect of the workpiece material, interference of the reflected beam, and partial overlapping of second mode of the travelling wave enable to identify a unique pattern in the travelling wave in the substrate. 相似文献
108.
CLIFFORDMARTINGALESΦ-EQUIVALENCEBETWEENS(f)ANDf¥LONGRULIN;QIANTAO(InstituteofMathematics,AcademiaSinica,Beijing100080,China.)... 相似文献
109.
110.