全文获取类型
收费全文 | 6733篇 |
免费 | 476篇 |
国内免费 | 333篇 |
专业分类
化学 | 408篇 |
晶体学 | 6篇 |
力学 | 812篇 |
综合类 | 50篇 |
数学 | 1423篇 |
物理学 | 1931篇 |
综合类 | 2912篇 |
出版年
2024年 | 18篇 |
2023年 | 54篇 |
2022年 | 95篇 |
2021年 | 126篇 |
2020年 | 125篇 |
2019年 | 123篇 |
2018年 | 129篇 |
2017年 | 143篇 |
2016年 | 154篇 |
2015年 | 206篇 |
2014年 | 298篇 |
2013年 | 416篇 |
2012年 | 315篇 |
2011年 | 368篇 |
2010年 | 281篇 |
2009年 | 339篇 |
2008年 | 352篇 |
2007年 | 454篇 |
2006年 | 382篇 |
2005年 | 299篇 |
2004年 | 298篇 |
2003年 | 290篇 |
2002年 | 247篇 |
2001年 | 252篇 |
2000年 | 275篇 |
1999年 | 210篇 |
1998年 | 197篇 |
1997年 | 176篇 |
1996年 | 126篇 |
1995年 | 122篇 |
1994年 | 94篇 |
1993年 | 97篇 |
1992年 | 77篇 |
1991年 | 78篇 |
1990年 | 52篇 |
1989年 | 38篇 |
1988年 | 62篇 |
1987年 | 43篇 |
1986年 | 21篇 |
1985年 | 15篇 |
1984年 | 10篇 |
1983年 | 5篇 |
1982年 | 10篇 |
1981年 | 12篇 |
1980年 | 6篇 |
1979年 | 13篇 |
1977年 | 9篇 |
1973年 | 12篇 |
1972年 | 4篇 |
1969年 | 3篇 |
排序方式: 共有7542条查询结果,搜索用时 31 毫秒
71.
朱瑞英 《内蒙古大学学报(自然科学版)》1995,26(6):670-676
Friedman在[1]中给出了一般抛物型方程Cauchy问题解的概率表达式。在此基础上,给出了它的概率数值及其误差估计。 相似文献
72.
73.
D. Sornette 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,3(1):125-137
We propose a formulation of the term structure of interest rates in which the forward curve is seen as the deformation of
a string. We derive the general condition that the partial differential equations governing the motion of such string must
obey in order to account for the condition of absence of arbitrage opportunities. This condition takes a form similar to a
fluctuation-dissipation theorem, albeit on the same quantity (the forward rate), linking the bias to the covariance of variation
fluctuations. We provide the general structure of the models that obey this constraint in the framework of stochastic partial
(possibly non-linear) differential equations. We derive the general solution for the pricing and hedging of interest rate
derivatives within this framework, albeit for the linear case (we also provide in the appendix a simple and intuitive derivation
of the standard European option problem). We also show how the “string” formulation simplifies into a standard N-factor model under a Galerkin approximation.
Received: 30 January 1998 / Revised: 12 February 1998 / Accepted: 16 February 1998 相似文献
74.
S. Fumeron P. Ben-Abdallah 《Journal of Quantitative Spectroscopy & Radiative Transfer》2006,97(2):195-208
The aim of this paper is to present several features of the couplings occurring between radiative transfer and the kinetics of a moving dielectric. After determining how the velocity field affects the apparent thermo-optical properties of matter, the energy transport problem is investigated in instationary regime and the general form of transient radiative transfer equation inside a moving medium is built. Then, the model is applied to the particular case of turbulent flows: a system of two equations for mean and fluctuating radiative energies is presented, and the resolution of this system is finally carried out. 相似文献
75.
本文利用角动量作为Liapunov函数建立二维的圆形涡块及涡环在有限或无限区域上的(Liapunov)非线性稳定性. 相似文献
76.
A phase-only encryption scheme using phase-encoded exclusive-OR (XOR) rules in a Fourier plane and a single path decryption
system are presented. To generate phase-only encrypted data, a zero-padded original image, multiplied by a random phase image,
is Fourier transformed and its real-valued data is encrypted with key data by using phase-encoded XOR rules. Since the original
information is encrypted on the Fourier plane, the proposed encryption is more tolerant to loss of key information by scratching
or cutting than previous XOR encryption in a space domain. A decryption is simply performed based on 2-f setup with spatial
filter by Fourier transform for multiplication phase-only encrypted data with phase-only key data. Due to single path architecture
without a reference wave, the proposed system is resistant to mechanical vibrations and fluctuation. Numerical simulations
have confirmed the validity of the proposed encryption scheme and simple decryption architecture. 相似文献
77.
We consider a four-dimensional generalization of Hess–Appel’rot system and costruct its Lax pair. Both classical and algebro-geometric integration procedure are proceeded. The algebro-geometric integration is based on deep facts from geometry of Prym varieties such as the Mumford relation and Mumford-Dalalyan theory. The integration is similar to the integration of Lagrange bitop which has recetly been performed by the authors. 相似文献
78.
Peter Friz Nicolas Victoir 《Annales de l'Institut Henri Poincaré (B) Probabilités et Statistiques》2007,43(6):775-785
We study large deviation principles for Gaussian processes lifted to the free nilpotent group of step N. We apply this to a large class of Gaussian processes lifted to geometric rough paths. A large deviation principle for enhanced (fractional) Brownian motion, in Hölder- or modulus topology, appears as special case. 相似文献
79.
The Hamiltonian formulation of the usual complex quantum mechanics in the theory of generalized quantum dynamics is discussed.
After the total trace Lagrangian, total trace Hamiltonian and two kinds of Poisson brackets are introduced, both the equations
of motion of some total trace functionals which are expressed by total trace Poisson brackets and the equations of motion
of some operators which are expressed by the without-total-trace Poisson brackets are obtained. Then a set of basic equations
of motion of the usual complex quantum mechanics are obtained, which are also expressed by the Poisson brackets and total
trace Hamiltonian in the generalized quantum dynamics. The set of equations of motion are consistent with the corresponding
Heisenberg equations.
Project supported by Prof. T.D. Lee’s NNSC Grant, the National Natural Science Foundation of China, the Foundation of Ph.
D. Directing Programme of Chinese University, and the Chinese Academy of Sciences. 相似文献
80.
P. J. Forrester 《Journal of statistical physics》1988,51(3-4):457-479
The Coulomb system consisting of an equal number of positive and negative charged rods confined to a one-dimensional lattice is studied. The grand partition function can be calculated exactly at two values of the coupling constant=q
2/k
B
T (q denoting the magnitude of the charges). The exact results lead to the conjecture that in the complex scaled fugacity plane, all the zeros of the grand partition function lie on the negative real axis for<2, on the point=–1 for=2, and on the unit circle for>2. In addition, for>4, we conjecture in general and prove at=4 that the zeros pinch the real axis in the thermodynamic limit, with an essential singularity in the pressure at the reduced density 1/2. 相似文献