全文获取类型
收费全文 | 87375篇 |
免费 | 335篇 |
国内免费 | 374篇 |
专业分类
化学 | 24184篇 |
晶体学 | 787篇 |
力学 | 6731篇 |
数学 | 32030篇 |
物理学 | 15103篇 |
无线电 | 9249篇 |
出版年
2021年 | 28篇 |
2018年 | 11829篇 |
2017年 | 11452篇 |
2016年 | 6962篇 |
2015年 | 907篇 |
2014年 | 362篇 |
2013年 | 345篇 |
2012年 | 4184篇 |
2011年 | 11656篇 |
2010年 | 6827篇 |
2009年 | 6775篇 |
2008年 | 7169篇 |
2007年 | 9626篇 |
2006年 | 223篇 |
2005年 | 1551篇 |
2004年 | 1737篇 |
2003年 | 2161篇 |
2002年 | 1069篇 |
2001年 | 245篇 |
2000年 | 289篇 |
1999年 | 153篇 |
1998年 | 189篇 |
1997年 | 143篇 |
1996年 | 198篇 |
1995年 | 120篇 |
1994年 | 75篇 |
1993年 | 93篇 |
1992年 | 53篇 |
1991年 | 67篇 |
1990年 | 49篇 |
1989年 | 61篇 |
1988年 | 58篇 |
1987年 | 57篇 |
1986年 | 59篇 |
1985年 | 49篇 |
1984年 | 42篇 |
1983年 | 36篇 |
1982年 | 43篇 |
1981年 | 39篇 |
1980年 | 48篇 |
1979年 | 47篇 |
1978年 | 35篇 |
1973年 | 27篇 |
1914年 | 45篇 |
1913年 | 40篇 |
1912年 | 40篇 |
1909年 | 41篇 |
1908年 | 40篇 |
1907年 | 32篇 |
1904年 | 28篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
281.
Stewart Baldwin 《Journal of Fixed Point Theory and Applications》2010,7(1):201-222
We construct abstract Julia sets homeomorphic to Julia sets for complex polynomials of the form f
c
(z) = z
2 + c, having an associated periodic kneading sequence of the form [`(a*)]{\overline{\alpha\ast}} which is not a period n-tupling. We show that there is a single simply-defined space of “itineraries” which contains homeomorphic copies of all such
Julia sets in a natural combinatorial way, with dynamical properties which are derivable directly from the combinatorics.
This also leads to a natural definition of abstract Julia sets even for those kneading sequences which are not realized by
any polynomial f
c
, with similar dynamical properties. 相似文献
282.
283.
With the application of the topological upgrade, more and more experts are interested in the problems concerning the mathematical
structure’s upgrade to its power set. This paper is a further study on the structure and interrelationship of a power group.
By revealing the nature of relationship between the power group and a regular one, the present paper proves some theorems
of the structure of the power group and constructs some theorems on its homomorphism and isomorphism as well, proposing an
expression form and isomorphism replacement construct methods of the power group. 相似文献
284.
Won Keun Min 《Acta Mathematica Hungarica》2010,129(4):350-356
We introduce the notion of (δ,δ′)-continuous functions on generalized topological spaces and investigate characterizations for such functions. We study the
relationship between (δ,δ′)-continuity and several types of continuity on generalized topological spaces. 相似文献
285.
Armin Lechleiter 《BIT Numerical Mathematics》2010,50(1):59-83
We consider imaging of periodic penetrable structures from measurements of scattered electromagnetic waves. The importance
of this problem stems from the decreasing size of periodic structures in photonic devices, together with an increasing demand
in fast non-destructive testing. This demand makes qualitative inverse scattering techniques particularly attractive since
they do not use time consuming optimization techniques for reconstruction but rather directly transform measured data into
a picture of the scattering object. We present the Factorization method as an algorithm for imaging of a special class of
periodic dielectric structures known as diffraction gratings. Our sampling method computes a picture of the shape of the periodic
structure from measured near-field data in a rapid way. We provide numerical examples illustrating this imaging technique. 相似文献
286.
A multi-objective mixed integer programming model for equity portfolio construction and selection is developed in this study,
in order to generate the Pareto optimal portfolios, using a novel version of the well known ε-constraint method. Subsequently, an interactive filtering process is also proposed to assist the decision maker in making
his/her final choice among the Pareto solutions. The proposed methodology is tested through an application in the Athens Stock
Exchange. 相似文献
287.
We prove that a real function is operator monotone (operator convex) if the corresponding monotonicity (convexity) inequalities
are valid for some normal state on the algebra of all bounded operators in an infinite-dimensional Hilbert space. We describe
the class of convex operator functions with respect to a given von Neumann algebra in dependence of types of direct summands
in this algebra. We prove that if a function from ℝ+ into ℝ+ is monotone with respect to a von Neumann algebra, then it is also operator monotone in the sense of the natural order on
the set of positive self-adjoint operators affiliated with this algebra. 相似文献
288.
The purpose of this paper is to describe the structures of the Möbius semigroup induced by the Möbius transformation group (?, SL(2,?)). In particular, we study stabilizer subsemigoups of Möbius semigroup via the triangle semigroup. In this work, we obtained a geometric interpretation of the least contraction coefficient function of the Möbius semigroup via the triangle semigroup and investigated an extension of stabilizer subsemigoups of the Möbius semigroup. Finally, we obtained a factorization of our stabilizer subsemigoups of the Möbius semigroup. 相似文献
289.
Using variational method and lower and upper solutions, we get a generalized quasilinearization method which construct an
iterative scheme converging uniformly to a solution of a nonlinear second-order impulsive differential equations involving
the p-Laplacian, and converging quadratically when p=2. 相似文献
290.
Tohru Nakashima 《Designs, Codes and Cryptography》2010,57(1):107-115
We discuss the properties of algebraic-geometric codes defined by a vector bundle on a curve X over a finite field. We investigate the correction capacities of the codes defined from vector bundles constructed by means
of finite coverings of X. 相似文献