全文获取类型
收费全文 | 68803篇 |
免费 | 2135篇 |
国内免费 | 161篇 |
学科分类
数理化 | 71099篇 |
出版年
2023年 | 476篇 |
2022年 | 642篇 |
2021年 | 931篇 |
2020年 | 1034篇 |
2019年 | 1025篇 |
2018年 | 1702篇 |
2017年 | 1340篇 |
2016年 | 2146篇 |
2015年 | 1894篇 |
2014年 | 1996篇 |
2013年 | 4078篇 |
2012年 | 4485篇 |
2011年 | 4663篇 |
2010年 | 2880篇 |
2009年 | 2512篇 |
2008年 | 4025篇 |
2007年 | 3950篇 |
2006年 | 3579篇 |
2005年 | 3389篇 |
2004年 | 2893篇 |
2003年 | 2416篇 |
2002年 | 2081篇 |
2001年 | 1233篇 |
2000年 | 1120篇 |
1999年 | 789篇 |
1998年 | 607篇 |
1997年 | 571篇 |
1996年 | 685篇 |
1995年 | 454篇 |
1994年 | 533篇 |
1993年 | 490篇 |
1992年 | 519篇 |
1991年 | 471篇 |
1990年 | 458篇 |
1989年 | 428篇 |
1988年 | 360篇 |
1987年 | 358篇 |
1986年 | 314篇 |
1985年 | 508篇 |
1984年 | 506篇 |
1983年 | 336篇 |
1982年 | 454篇 |
1981年 | 427篇 |
1980年 | 390篇 |
1979年 | 369篇 |
1978年 | 374篇 |
1977年 | 315篇 |
1976年 | 363篇 |
1975年 | 316篇 |
1973年 | 308篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
81.
Details are given of a new method allowing an exact calculation of the spontaneous magnetization in the corner as well as along the edge at an arbitrary distance of the corner for a rectangular planar Ising ferromagnet. 相似文献
82.
83.
F. Grisch P. Bouchardy M. Péalat B. Chanetz T. Pot M. C. Coët 《Applied physics. B, Lasers and optics》1993,56(1):14-20
Rotational temperature and nitrogen number density are measured in the shock wave/boundary layer interaction region in the vicinity of a two-dimensional compression corner disposed in a low pressure, 55 K, Mach 10 hypersonic air flow. Spatially-resolved data are recorded using a nonlinear optical technique named dual-line coherent anti-Stokes Raman scattering (DLCARS). Averaged temperature and density profiles are compared with those predicted by a Navier-Stokes solver. Good agreement is found. 相似文献
84.
Summary. This paper introduces and analyzes the convergence properties of a method that computes an approximation to the invariant
subspace associated with a group of eigenvalues of a large not necessarily diagonalizable matrix. The method belongs to the
family of projection type methods. At each step, it refines the approximate invariant subspace using a linearized Riccati's
equation which turns out to be the block analogue of the correction used in the Jacobi-Davidson method. The analysis conducted
in this paper shows that the method converges at a rate quasi-quadratic provided that the approximate invariant subspace is
close to the exact one. The implementation of the method based on multigrid techniques is also discussed and numerical experiments
are reported.
Received June 15, 2000 / Revised version received January 22, 2001 / Published online October 17, 2001 相似文献
85.
Jesús M. Velásquez Bermúdez 《Annals of Operations Research》2002,117(1-4):21-31
This document presents theoretical considerations about the solution of dynamic optimization problems integrating the Benders Theory, the Dynamic Programming approach and the concepts of Control Theory. The so called Generalized Dual Dynamic Programming Theory (GDDP) can be considered as an extension of two previous approaches known as Dual Dynamic Programming (DDP): The first is the work developed by Pereira and Pinto [3–5], which was revised by Velásquez and others [8,9]. The second is the work developed by Read and others [2,6,7]. 相似文献
86.
Carmelo Nú¯nez 《Annali di Matematica Pura ed Applicata》1992,161(1):43-56
Summary Let K be a compact Hausdorff space and let E be a Banach space. We denote by C(K, E) the Banach space of all E-valued continuous functions defined on K, endowed with the supremum norm. We study in this paper Banach-Saks operators defined on C(K, E) spaces. We characterize these operators for a large class of compacts K (the scattered ones), or for a large class of Banach spaces E (the superreflexive ones). We also show by some examples that our theorems can not be extended directly.Partially supported by C.A.I.C.Y.T. grant 0338-84. The author wishes to thank Professor F.Bombal for his encouragement. 相似文献
87.
The n-dimensional cube Qn is the graph whose vertices are the subsets of {1,…n}, with two vertices adjacent if and only if their symmetric difference is a singleton. Clearly Qn has diameter and radious n. Write M = n2n-1 = e(Qn) for the size of Qn. Let Q = (Qt)oM be a random Qn-process. Thus Qt is a spanning subgraph of Qn of size t, and Qt is obtained from Qt–1 by the random addition of an edge of Qn not in Qt–1, Let t(k) = τ(Q;δ?k) be the hitting time of the property of having minimal degree at least k. We show that the diameter dt = diam (Qt) of Qt in almost every Q? behaves as follows: dt starts infinite and is first finite at time t(1), it equals n + 1 for t(1) ? t(2) and dt, = n for t ? t(2). We also show that the radius of Qt, is first finite for t = t(1), when it assumes the value n. These results are deduced from detailed theorems concerning the diameter and radius of the almost surely unique largest component of Qt, for t = Ω(M). © 1994 John Wiley & Sons, Inc. 相似文献
88.
89.
In the field of research on soluble conducting polymers, the poly(o-alkylanilines) are very interesting because we can expect them to give more soluble polymers and new properties. Like poly(o-propylaniline) (POP), which is more soluble than polyaniline (PANi), poly(o-hexylaniline) (POH) appears to be more soluble in organic solvents than POP because of the longer alkyl groups in the 2-position. The higher solubility confers better processability on this new polymer, and because of this solubility, an NMR study in solution became possible.The nitration of hexylbenzene and the reduction of the resulting product to o-hexylaniline were performed according to the literature. The chemical polymerization was easy and it is possible to produce this polymer in large quantities.The polymerization carried out in anhydrous NH4F, 2.35 HF medium and in 5 M perchloric acid gave a polymer with almost quantitative yield. The electrochemical behaviour of POH displayed faster electron transfers than PANi in organic solvents, depending on the acido-basicity level of the aqueous solutions. Unlike PANi, fractal growth was not observed. 相似文献
90.
We prove global existence of solutions to the continuous nonhomogeneous Smoluchowski equation for coagulation rates satisfying a more general structure condition than the Galkin–Tupchiev monotony hypothesis considered in (Ph. Laurençot, S. Mischler, Arch. Rational Mech. Anal. 162 (1) (2002) 45–99). The Smoluchowski coagulation rate fulfils this condition as well as some rates which vanish on the diagonal. Under the condition of positivity of the coagulation rate outside of the diagonal we prove that solutions tend to 0 in the large time asymptotic. These results depend on a new estimate from below for the dissipation rate of the Lp-norm, p>1. To cite this article: S. Mischler, M. Rodriguez Ricard, C. R. Acad. Sci. Paris, Ser. I 336 (2003). 相似文献