全文获取类型
收费全文 | 4858篇 |
免费 | 358篇 |
国内免费 | 353篇 |
专业分类
化学 | 165篇 |
晶体学 | 6篇 |
力学 | 431篇 |
综合类 | 64篇 |
数学 | 4170篇 |
物理学 | 733篇 |
出版年
2023年 | 34篇 |
2022年 | 43篇 |
2021年 | 60篇 |
2020年 | 108篇 |
2019年 | 101篇 |
2018年 | 106篇 |
2017年 | 104篇 |
2016年 | 123篇 |
2015年 | 54篇 |
2014年 | 146篇 |
2013年 | 360篇 |
2012年 | 136篇 |
2011年 | 198篇 |
2010年 | 179篇 |
2009年 | 264篇 |
2008年 | 300篇 |
2007年 | 286篇 |
2006年 | 268篇 |
2005年 | 239篇 |
2004年 | 208篇 |
2003年 | 216篇 |
2002年 | 244篇 |
2001年 | 184篇 |
2000年 | 174篇 |
1999年 | 195篇 |
1998年 | 158篇 |
1997年 | 148篇 |
1996年 | 109篇 |
1995年 | 82篇 |
1994年 | 87篇 |
1993年 | 35篇 |
1992年 | 56篇 |
1991年 | 70篇 |
1990年 | 47篇 |
1989年 | 34篇 |
1988年 | 36篇 |
1987年 | 43篇 |
1986年 | 30篇 |
1985年 | 49篇 |
1984年 | 37篇 |
1983年 | 27篇 |
1982年 | 25篇 |
1981年 | 23篇 |
1980年 | 18篇 |
1979年 | 24篇 |
1978年 | 24篇 |
1977年 | 23篇 |
1976年 | 12篇 |
1974年 | 12篇 |
1973年 | 13篇 |
排序方式: 共有5569条查询结果,搜索用时 15 毫秒
1.
Tomoyuki Nakatsuka 《Mathematische Nachrichten》2021,294(1):98-117
We study the existence of a time‐periodic solution with pointwise decay properties to the Navier–Stokes equation in the whole space. We show that if the time‐periodic external force is sufficiently small in an appropriate sense, then there exists a time‐periodic solution of the Navier–Stokes equation such that and uniformly in as . Our solution decays faster than the time‐periodic Stokes fundamental solution and the faster decay of its spatial derivatives of higher order is also described. 相似文献
2.
《Studies in Applied Mathematics》2018,141(3):399-417
We extend our previous results characterizing the loading properties of a diffusing passive scalar advected by a laminar shear flow in ducts and channels to more general cross‐sectional shapes, including regular polygons and smoothed corner ducts originating from deformations of ellipses. For the case of the triangle and localized, cross‐wise uniform initial distributions, short‐time skewness is calculated exactly to be positive, while long‐time asymptotics shows it to be negative. Monte Carlo simulations confirm these predictions, and document the timescale for sign change. The equilateral triangle appears to be the only regular polygon with this property—all others possess positive skewness at all times. Alternatively, closed‐form flow solutions can be constructed for smooth deformations of ellipses, and illustrate how both nonzero short‐time skewness and the possibility of multiple sign switching in time is unrelated to domain corners. Exact conditions relating the median and the skewness to the mean are developed which guarantee when the sign for the skewness implies front (more mass to the right of the mean) or back (more mass to the left of the mean) “loading” properties of the evolving tracer distribution along the pipe. Short‐ and long‐time asymptotics confirm this condition, and Monte Carlo simulations verify this at all times. The simulations are also used to examine the role of corners and boundaries on the distribution for short‐time evolution of point source , as opposed to cross‐wise uniform, initial data. 相似文献
4.
A fundamental question in random matrix theory is to quantify the optimal rate of convergence to universal laws. We take up this problem for the Laguerre β ensemble, characterized by the Dyson parameter β, and the Laguerre weight , in the hard edge limit. The latter relates to the eigenvalues in the vicinity of the origin in the scaled variable . Previous work has established the corresponding functional form of various statistical quantities—for example, the distribution of the smallest eigenvalue, provided that . We show, using the theory of multidimensional hypergeometric functions based on Jack polynomials, that with the modified hard edge scaling , the rate of convergence to the limiting distribution is , which is optimal. In the case , general the explicit functional form of the distribution of the smallest eigenvalue at this order can be computed, as it can for and general . An iterative scheme is presented to numerically approximate the functional form for general . 相似文献
5.
In a previous paper (Ref. 1), an exact solution of the optimal planar interception with fixed end conditions was derived in closed form. The optimal control was expressed as an explicit function of the state variables and two fixed parameters, obtained by solving a set of nonlinear algebraic equations involving elliptic integrals. In order to facilitate the optimal control implementation, the present paper derives a highly accurate simplified solution assuming that the ratio of the pursuer turning radius to the initial range is small. An asymptotic expansion further reduces the computational workload. Construction of a near-optimal open-loop control, based on the approximations, completes the present paper. 相似文献
6.
Lisa Lorentzen 《Numerical Algorithms》1995,10(1):69-111
Over the last 20 years a large number of algorithms has been published to improve the speed and domain of convergence of continued fractions. In this survey we show that these algorithms are strongly related. Actually, they essentially boil down to two main principles.We also prove some results on asymptotic expansions of tail values of limit periodic continued fractions.Dedicated to Luigi Gatteschi on his seventieth birthdayThis research was partially supported by The Norwegian Research Council and by the HMC project ROLLS, under contract CHRX-CT93-0416. 相似文献
7.
LIU Jixue ZHANG Sanguo & CHEN Xiru Department of Statistics Finance University of Science Technology of China Hefei China Department of Mathematics Graduate School of Chinese Academy of Sciences Beijing China 《中国科学A辑(英文版)》2006,49(6):752-769
This paper studies the linear EV model when replicate observations are made only on independent variables. We construct the estimates of regression coefficients and prove the consistency and asymptotic normality under some proper conditions. Results obtained reveal the difference between the case where the independent and dependent variables are observed repeatedly and simultaneously and the case studied in this article. 相似文献
8.
In this paper we study the Hankel convolution operators on the space of even and entire functions and on Schwartz distribution spaces. We characterize the Hankel convolution operators as those ones that commute with Hankel translations and with a Bessel operator. Also we prove that the Hankel convolution operators are hypercyclic and chaotic on the spaces under consideration. 相似文献
9.
《组合设计杂志》2002,10(5):283-293
An Orthogonal Double Cover (ODC) of the complete graph Kn by an almost‐hamiltonian cycle is a decomposition of 2Kn into cycles of length n?1 such that the intersection of any two of them is exactly one edge. We introduce a new class of such decompositions. If n is a prime, the special structure of such a decomposition allows to expand it to an ODC of Kn+1 by an almost‐hamiltonian cycle. This yields the existence of an ODC of Kp+1 by an almost‐hamiltonian cycle for primes p of order 3 mod 4 and its eventual existence for arbitrary primes p. © 2002 Wiley Periodicals, Inc. J Combin Designs 10: 283–293, 2002; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/jcd.10011 相似文献
10.
D. Yafaev 《Proceedings Mathematical Sciences》2002,112(1):245-255
We find an explicit function approximating at high energies the kernel of the scattering matrix with arbitrary accuracy. Moreover,
the same function gives all diagonal singularities of the kernel of the scattering matrix in the angular variables.
This paper is dedicated to Jean-Michel Combes on the occasion of his sixtieth birthday. 相似文献