全文获取类型
收费全文 | 24879篇 |
免费 | 688篇 |
国内免费 | 775篇 |
专业分类
化学 | 4466篇 |
晶体学 | 867篇 |
力学 | 490篇 |
综合类 | 75篇 |
数学 | 17518篇 |
物理学 | 2926篇 |
出版年
2023年 | 92篇 |
2022年 | 219篇 |
2021年 | 185篇 |
2020年 | 209篇 |
2019年 | 605篇 |
2018年 | 626篇 |
2017年 | 434篇 |
2016年 | 428篇 |
2015年 | 386篇 |
2014年 | 745篇 |
2013年 | 1372篇 |
2012年 | 746篇 |
2011年 | 1561篇 |
2010年 | 1583篇 |
2009年 | 1813篇 |
2008年 | 1924篇 |
2007年 | 1885篇 |
2006年 | 1486篇 |
2005年 | 1099篇 |
2004年 | 1047篇 |
2003年 | 858篇 |
2002年 | 699篇 |
2001年 | 522篇 |
2000年 | 459篇 |
1999年 | 495篇 |
1998年 | 453篇 |
1997年 | 370篇 |
1996年 | 526篇 |
1995年 | 444篇 |
1994年 | 438篇 |
1993年 | 387篇 |
1992年 | 305篇 |
1991年 | 194篇 |
1990年 | 179篇 |
1989年 | 181篇 |
1988年 | 123篇 |
1987年 | 125篇 |
1986年 | 133篇 |
1985年 | 179篇 |
1984年 | 117篇 |
1983年 | 88篇 |
1982年 | 115篇 |
1981年 | 104篇 |
1980年 | 88篇 |
1979年 | 55篇 |
1978年 | 69篇 |
1977年 | 69篇 |
1976年 | 61篇 |
1975年 | 17篇 |
1974年 | 22篇 |
排序方式: 共有10000条查询结果,搜索用时 18 毫秒
41.
Sisto Baldo Giandomenico Orlandi 《Calculus of Variations and Partial Differential Equations》1996,4(4):369-384
We define a class
p
(M,N) of Sobolev maps from a manifoldM into a manifoldN, in such a way that each mapu
p
(M, N) has a well defined [p]-homotopy type, providedN satisfies a topological hypothesis. Using this, we prove the existence of minimizers in [p]-homotopy classes for some polyconvex variational problems. 相似文献
42.
V. Suresh 《K-Theory》1996,10(6):597-610
Let X be a smooth projective surface over a number field k. Let (CH0(X)) denote the Chow group of zero-cyles modulo rational equivalence on X. Let CH0(X) be the subgroup of CH
0(X) consisting of classes which vanish when going over to an arbitrary completion of k. Bloch put forward a conjecture asserting that this group is isomorphic to the Tate-Shafarevich group of a certain Galois module atttached to X. In this paper, we disprove this general conjecture. We produce a conic bundle X over an elliptic curve, for which the group (CH0(X) is not zero, but the Galois-theoretic Tate-Shafarevich group vanishes. 相似文献
43.
Yong Zhang 《Order》1996,13(4):365-367
G. Grätzer, H. Lakser, and E. T. Schmidt proved that every distributive lattice with n join-irreducible elements can be represented as the congruence lattice of a small lattice L, that is, a lattice L with O(n
2
) elements. G. Grätzer, I. Rival, and N. Zaguia proved that, for any <2, O(n
2
) can not be improved to O(n
). In this note we show that the theorem about small representation can be improved further to get a more delicate result. 相似文献
44.
Huzihiro Araki 《Letters in Mathematical Physics》1996,38(4):399-410
Continuing the earlier work on soliton sectors, we determine all finite energy representations of the XY model for almost all parameter values. In the interior of unique vacuum regions of parameters (i.e. the large external magnetic field region ||>1), the unique irreducible vacuum representation is the only finite energy representation.At the critical values of the parameters (||=1 as well as theXY symmetric case =0, ||1), there is an infinite number of mutually nonequivalent irreducible finite energy representations. Apart from the unique irreducible ground state representation and another associated irreducible representation, these infinite number of representations arise from an infinite number of nearly zero energy excitations of the ground state with a finite total energy and may be called infrared representations.In the remaining cases, as have been studied earlier, there are two additional irreducible finite energy representations besides two irreducible ground state representations and they are topological soliton sectors with different ground state limits in positive and negative spatial infinity. (For two exceptional values of parameters (, )=(0, ±1), they also become ground state representations.) 相似文献
45.
We consider a class of vertex models describing directed lines on a lattice in arbitraryd dimensions, and solve the model exactly for the Cartesian lattice and in the case that each loop of lines carries a fugacity - 1. Our analysis, which can be carried out for arbitrary lattices, is based on an equivalence of the vertex model with a dimer problem. The dimer problem is, in turn, solved using the method of Pfaffians. It is found that the system is frozen below a critical temperatureT
cwith the critical exponent = (3 –d)/2. 相似文献
46.
The property of self-adjointness of the operatorQ =a
+ +a
- in three types ofq-oscillator algebras is considered. Spectral measures and generalized eigenfunctions ofQ are found in the cases when this operator is bounded. Generalized eigenvectors are expressed in terms ofq-Hermite polynomials. If the operatorQ is unbounded, then its closure
is not self-adjoint. However, in this case,
admits self-adjoint extensions. Deficiency subspaces are one-dimensional. These subspaces are explicitly found. 相似文献
47.
Robert D. Skeel 《BIT Numerical Mathematics》1993,33(1):172-175
For fixed step-sizeh the Störmer method is stable for the standard test equationÿ=
2
y,>0, if and only ifh<2. We show that for variable step sizeh
n there does not exist a (positive) limit onh which ensures stability. Nor can we guarantee stability if, in addition, we limit the step size ratioh
n/h
n–1.This work was supported in part by National Science Foundation Grant DMS 90 15533. 相似文献
48.
The stability and convergence of the solutions of perturbed and regularized variational inequality to the solutions of the primary (unstable a priori) variational inequality with proper monotone operator are investigated. All the objects of inequality: the operatorA, the right-hand partf and the set of constrains are to be perturbed. At the same time no assumptions of boundedness and smoothness of the operatorA are used. The connection between the parameters of perturbations, which guarantees strong convergence of approximate solutions, is established. It is proved that the existence of the solution to the unperturbed variational inequality is necessary and sufficient condition for convergence of the regularized perturbed inequality solutions.This research was supported in part by the Ministry of Science Grant 3481-1-91 and by the Ministry of Absorption Center for Absorption in Science. 相似文献
49.
Riddhi Shah 《Monatshefte für Mathematik》1993,115(3):191-213
For any locally compact groupG, we show that any locally tight homomorphism from a real directed semigroup intoM
1
(G) (semigroup of probability measures onG) has a shift which extends to a continuous one-parameter semigroup. IfG is ap-adic algebraic group then the above holds even iff is not locally tight. These results are applied to give sufficient conditions for embeddability of some translate of limits of sequences of the form {v
n
kn
} and M
1
(G) such that ()=
M
, for somek>1 and AutG (cf. Theorems 2.1, 2.4, 3.7). 相似文献
50.
Israel Gohberg Naum Krupnik Ilya Spitkovsky 《Integral Equations and Operator Theory》1993,17(3):322-337
The Banach algebra generated by one-dimensional linear singular integral operators with matrix valued piecewise continuous coefficients in the spaceL
p
(,) with an arbitrary weight is studied. The contour consists of a finite number of closed curves and open arcs with satisfy the Carleson condition. The contour may have a finite number of points of selfintersection. The symbol calculus in this algebra is the main result of the paper. 相似文献