全文获取类型
收费全文 | 7392篇 |
免费 | 749篇 |
国内免费 | 388篇 |
专业分类
化学 | 2122篇 |
晶体学 | 64篇 |
力学 | 1162篇 |
综合类 | 79篇 |
数学 | 1877篇 |
物理学 | 3225篇 |
出版年
2024年 | 10篇 |
2023年 | 49篇 |
2022年 | 120篇 |
2021年 | 155篇 |
2020年 | 173篇 |
2019年 | 164篇 |
2018年 | 164篇 |
2017年 | 183篇 |
2016年 | 238篇 |
2015年 | 215篇 |
2014年 | 314篇 |
2013年 | 595篇 |
2012年 | 338篇 |
2011年 | 379篇 |
2010年 | 305篇 |
2009年 | 385篇 |
2008年 | 477篇 |
2007年 | 487篇 |
2006年 | 403篇 |
2005年 | 353篇 |
2004年 | 323篇 |
2003年 | 331篇 |
2002年 | 247篇 |
2001年 | 248篇 |
2000年 | 269篇 |
1999年 | 253篇 |
1998年 | 191篇 |
1997年 | 165篇 |
1996年 | 104篇 |
1995年 | 125篇 |
1994年 | 91篇 |
1993年 | 101篇 |
1992年 | 89篇 |
1991年 | 71篇 |
1990年 | 44篇 |
1989年 | 36篇 |
1988年 | 51篇 |
1987年 | 41篇 |
1986年 | 31篇 |
1985年 | 29篇 |
1984年 | 22篇 |
1983年 | 11篇 |
1982年 | 23篇 |
1981年 | 25篇 |
1980年 | 19篇 |
1979年 | 17篇 |
1978年 | 8篇 |
1977年 | 20篇 |
1974年 | 6篇 |
1973年 | 14篇 |
排序方式: 共有8529条查询结果,搜索用时 62 毫秒
81.
Let R be a local ring and let (x
1, …, x
r) be part of a system of parameters of a finitely generated R-module M, where r < dimR
M. We will show that if (y
1, …, y
r) is part of a reducing system of parameters of M with (y
1, …, y
r) M = (x
1, …, x
r) M then (x
1, …, x
r) is already reducing. Moreover, there is such a part of a reducing system of parameters of M iff for all primes P ε Supp M ∩ V
R(x
1, …, x
r) with dimR
R/P = dimR
M − r the localization M
P of M at P is an r-dimensional Cohen-Macaulay module over R
P.
Furthermore, we will show that M is a Cohen-Macaulay module iff y
d is a non zero divisor on M/(y
1, …, y
d−1) M, where (y
1, …, y
d) is a reducing system of parameters of M (d:= dimR
M). 相似文献
82.
Dong Sheng WU Yi Min XIAO 《数学学报(英文版)》2007,23(4):613-622
Let B^α = {B^α(t),t E R^N} be an (N,d)-fractional Brownian motion with Hurst index α∈ (0, 1). By applying the strong local nondeterminism of B^α, we prove certain forms of uniform Hausdorff dimension results for the images of B^α when N 〉 αd. Our results extend those of Kaufman for one-dimensional Brownian motion. 相似文献
83.
Since 1945, Foldy’s method has been used to predict velocity and attenuation for various types of scatterers. In this paper, it is shown that Foldy’s method also yields predictions of reflection and transmission of scalar waves by a random distribution of point or line scatterers contained in a slab. Results are given in two and three dimensions, and for normal and oblique incidences. Formulae are also obtained for the reflection and transmission of longitudinal waves by point or line scatterers distributed in an elastic (non-viscous) fluid. Energy equations are derived, and expressions are obtained for the energy dissipated in the slab on average over one period. Curves for the reflection and transmission coefficients are presented in the case of solid cylindrical bars immersed in a fluid. The results obtained in this paper are expected to be valid for a low density of scatterers. Potential applications of this work occur in ultrasonic evaluation of materials, seismic exploration and medical ultrasonics, where reflected (or backscattered) data are used to construct maps or images of the materials (metals, composites, earth subsurface, tissue). The formulae of this work are expected to provide useful tools for better and more efficient mapping or imaging. 相似文献
84.
Consider a queueing system where customers arrive at a circle according to a homogeneous Poisson process. After choosing their positions on the circle, according to a uniform distribution, they wait for a single server who travels on the circle. The server's movement is modelled by a Brownian motion with drift. Whenever the server encounters a customer, he stops and serves this customer. The service times are independent, but arbitrarily distributed. The model generalizes the continuous cyclic polling system (the diffusion coefficient of the Brownian motion is zero in this case) and can be interpreted as a continuous version of a Markov polling system. Using Tweedie's lemma for positive recurrence of Markov chains with general state space, we show that the system is stable if and only if the traffic intensity is less than one. Moreover, we derive a stochastic decomposition result which leads to equilibrium equations for the stationary configuration of customers on the circle. Steady-state performance characteristics are determined, in particular the expected number of customers in the system as seen by a travelling server and at an arbitrary point in time. 相似文献
85.
A multiparameter boundary-value problem of fresh infiltration water seepage in a drained fringe above quiescent saline water is solved in the direct statement and studied in detail. 相似文献
86.
87.
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
88.
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
89.
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
90.
N. B. Brusnikina A. V. Lotov 《Computational Mathematics and Mathematical Physics》2007,47(11):1779-1787
A method is proposed for approximating the reachable set of a dynamic system with a state space dimension no higher than six-eight considered on a finite time interval. The system is governed by linear differential equations with piecewise constant coefficients and impulse actions specified at prescribed times. The method is based on guaranteed-accuracy polyhedral approximations of reachable sets at researcher-specified times. Every approximation is constructed using the preceding one. A procedure is described for choosing parameters of the method that ensure the required accuracy with close-to-minimal time costs. 相似文献