全文获取类型
收费全文 | 40032篇 |
免费 | 1395篇 |
国内免费 | 1464篇 |
专业分类
化学 | 10645篇 |
晶体学 | 210篇 |
力学 | 715篇 |
综合类 | 90篇 |
数学 | 26484篇 |
物理学 | 4747篇 |
出版年
2024年 | 42篇 |
2023年 | 392篇 |
2022年 | 371篇 |
2021年 | 374篇 |
2020年 | 526篇 |
2019年 | 1013篇 |
2018年 | 1050篇 |
2017年 | 634篇 |
2016年 | 671篇 |
2015年 | 776篇 |
2014年 | 1311篇 |
2013年 | 2389篇 |
2012年 | 1522篇 |
2011年 | 2706篇 |
2010年 | 2201篇 |
2009年 | 2845篇 |
2008年 | 3090篇 |
2007年 | 2913篇 |
2006年 | 2199篇 |
2005年 | 1599篇 |
2004年 | 1427篇 |
2003年 | 1299篇 |
2002年 | 1388篇 |
2001年 | 805篇 |
2000年 | 795篇 |
1999年 | 907篇 |
1998年 | 753篇 |
1997年 | 603篇 |
1996年 | 715篇 |
1995年 | 740篇 |
1994年 | 671篇 |
1993年 | 533篇 |
1992年 | 465篇 |
1991年 | 337篇 |
1990年 | 267篇 |
1989年 | 296篇 |
1988年 | 199篇 |
1987年 | 206篇 |
1986年 | 176篇 |
1985年 | 263篇 |
1984年 | 223篇 |
1983年 | 140篇 |
1982年 | 214篇 |
1981年 | 196篇 |
1980年 | 130篇 |
1979年 | 101篇 |
1978年 | 121篇 |
1977年 | 98篇 |
1976年 | 74篇 |
1974年 | 28篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
William Kerby 《Aequationes Mathematicae》1991,41(1):187-191
Summary Nearfields of rank 2 over their kernel which are not Dickson nearfields have recently been constructed by H. Zassenhaus. Here it is shown that KT-nearfields of rank 2 over their kernels and of characteristic 2 are necessarily Dickson nearfields which are coupled to quadratic field extensions and their Dickson group is isomorphic to 2. Using results of Gröger one obtains all KT-nearfields of rank 2 over the field of rational numbers. 相似文献
92.
Kazimierz Nikodem 《Aequationes Mathematicae》1991,42(1):182-189
Summary LetX be a real vector space,D a convex subset ofX and (Y, K) an order complete ordered vector space. The following sandwich theorem holds: Iff: D Y is midconvex,g: D Y {– } is midconcave andg f onD, then there exists a Jensen mappingh: D Y {– } such thatg h f onD. Using this theorem we show that a mappingf: D Y is midconvex if and only if it has Jensen support at every point ofD. Moreover, ifX is a Baire topological vector space and (Y, K) is an ordered topological vector space satisfying some additional conditions, then a mappingf: D Y is continuous whenever it has continuous Jensen support at every point ofD. As an application of these results we obtain the equality of some set-classes connected with additive and midconvex operators.Dedicated to the memory of Alexander M. Ostrowski on the occasion of the 100th anniversary of his birth 相似文献
93.
Summary We consider the two-dimensional Helmholtz equation u+u=0 inD with the boundary conditionsu=0 on D. D is the Swiss Cross — a region consisting of five unit squares. A method based on the concept of Coherence is utilized to determine an approximation for the first eigenvalue=
1 more accurate than calculated by classical difference methods. The numerical result is used to illustrate isoperimetric upper and lower bounds for
1, and to test some conjectures on its relations with torsional rigidity.Dedicated to the memory of Professor Lathar Collatz 相似文献
94.
K. Mørken 《Constructive Approximation》1991,7(1):195-208
In this paper it is shown how the algebraic product of two spline functions, each represented in terms of B-splines, can again be represented as a linear combination of suitable B-splines. As a corollary to this result we obtain an explicit representation of a given B-spline function in terms of B-splines of some arbitrary higher degree. This generalizes some known results for raising the degree by one. Recurrence relations for both products and degree raising are established that may be useful for computation.Communicated by Larry L. Schumaker. 相似文献
95.
In order to illustrate the class of conservative dynamical systems for which a Boltzmann entropy can be obtained under finite coarse-graining [2], we consider dynamical systems defined by the shift transformation on K
, where K is any finite set of integers. We give a class of non-Markovian invariant measures that verify the Chapman-Kolmogorov equation (equivalent to a Boltzmann entropy) for any positive stochastic matrix and that are ergodic but not weakly mixing. 相似文献
96.
Differential calculus on quantized simple lie groups 总被引:1,自引:0,他引:1
Branislav Jurčo 《Letters in Mathematical Physics》1991,22(3):177-186
Differential calculi, generalizations of Woronowicz's four-dimensional calculus on SU
q
(2), are introduced for quantized classical simple Lie groups in a constructive way. For this purpose, the approach of Faddeev and his collaborators to quantum groups was used. An equivalence of Woronowicz's enveloping algebra generated by the dual space to the left-invariant differential forms and the corresponding quantized universal enveloping algebra, is obtained for our differential calculi. Real forms for q are also discussed. 相似文献
97.
Jie Shen 《Numerische Mathematik》1992,62(1):49-73
Summary This paper is a continuation of our previous work [10] on projection methods. We study first existing higher order projection schemes in the semidiscretized form for the Navier-Stokes equations. One error analysis suggests that the precision of these schemes is most likely plagued by the inconsistent Neumann boundary condition satisfied by the pressure approximations. We then propose a penalty-projection scheme for which we obtain improved error estimates.This work is partially supported by NSF grant MS-8802596. 相似文献
98.
Janusz Matkowski 《Aequationes Mathematicae》1992,43(2-3):219-224
Summary In the present note we prove that every functionf: (0, ) [0, ) satisfying the inequalityaf(s) + bf(t) f(as + bt), s, t > 0, for somea andb such that 0 <a < 1 <a + b must be of the formf(t) = f(1)t, (t > 0). This improves our recent result in [2], where the inequality is assumed to hold for alls, t 0, and gives a positive answer to the question raised there.An analogue for functions of several real variables of the above result characterizes concave functions. Conjugate functions and some relations to Hölder's and Minkowski's inequalities are mentioned. 相似文献
99.
Alexander Pott 《Combinatorica》1992,12(1):89-93
In this paper we develop a new method to obtain identities in a group algebraGF(p)G if an abelian difference set of ordern0 (modp) exists inG. We give an explicit formula ifp
2 orp
3 is the exactp-power dividingn. This generalizes the approach of Wilbrink, Arasu and the author. The proof presented here uses some knowledge about field extensions of thep-adic numbers. 相似文献
100.
Enno Mammen 《Probability Theory and Related Fields》1992,93(4):439-455
Summary We show for an i.i.d. sample that bootstrap estimates consistently the distribution of a linear statistic if and only if the normal approximation with estimated variance works. An asymptotic approach is used where everything may depend onn. The result is extended to the case of independent, but not necessarily identically distributed random variables. Furthermore it is shown that wild bootstrap works under the same conditions as bootstrap.This work has been supported by the Deutsche Forschungsgemeinschaft, Sonderforschungsbereich 123 Stochastische Mathematische Modelle 相似文献