全文获取类型
收费全文 | 3714篇 |
免费 | 89篇 |
国内免费 | 130篇 |
专业分类
化学 | 720篇 |
晶体学 | 15篇 |
力学 | 9篇 |
综合类 | 4篇 |
数学 | 2985篇 |
物理学 | 200篇 |
出版年
2024年 | 1篇 |
2023年 | 11篇 |
2022年 | 21篇 |
2021年 | 19篇 |
2020年 | 26篇 |
2019年 | 65篇 |
2018年 | 72篇 |
2017年 | 35篇 |
2016年 | 44篇 |
2015年 | 40篇 |
2014年 | 88篇 |
2013年 | 211篇 |
2012年 | 88篇 |
2011年 | 214篇 |
2010年 | 223篇 |
2009年 | 270篇 |
2008年 | 356篇 |
2007年 | 338篇 |
2006年 | 298篇 |
2005年 | 196篇 |
2004年 | 199篇 |
2003年 | 162篇 |
2002年 | 109篇 |
2001年 | 83篇 |
2000年 | 94篇 |
1999年 | 111篇 |
1998年 | 99篇 |
1997年 | 51篇 |
1996年 | 74篇 |
1995年 | 70篇 |
1994年 | 70篇 |
1993年 | 52篇 |
1992年 | 29篇 |
1991年 | 13篇 |
1990年 | 22篇 |
1989年 | 11篇 |
1988年 | 15篇 |
1987年 | 9篇 |
1986年 | 4篇 |
1985年 | 4篇 |
1984年 | 7篇 |
1982年 | 3篇 |
1981年 | 4篇 |
1980年 | 3篇 |
1979年 | 10篇 |
1978年 | 1篇 |
1977年 | 3篇 |
1976年 | 2篇 |
1975年 | 3篇 |
排序方式: 共有3933条查询结果,搜索用时 15 毫秒
101.
István Gyöngy 《Acta Appl Math》1994,35(1-2):165-177
We coasider a partially observable diffusion process (x
t,yt)t0 whose unobservable componentx
t lives on a submanifold M ofR
n
. We present some general conditions under which the conditional law ofx
t, given the observationsy
s
,s [0,t], admits a density w.r.t. a given measure on M. We characterize the analytical properties of this density by using appropriate Sobolev spaces.Research supported by the Hungarian National Foundation of Scientific Research No. 2290. 相似文献
102.
The papers of R. Ramer and S. Kusuoka investigate conditions under which the probability measure induced by a nonlinear transformation on abstract Wiener space(,H,B) is absolutely continuous with respect to the abstract Wiener measure. These conditions reveal the importance of the underlying Hilbert spaceH but involve the spaceB in an essential way. The present paper gives conditions solely based onH and takes as its starting point, a nonlinear transformationT=I+F onH. New sufficient conditions for absolute continuity are given which do not seem easily comparable with those of Kusuoka or Ramer but are more general than those of Buckdahn and Enchev. The Ramer-Itô integral occurring in the expression for the Radon-Nikodym derivative is studied in some detail and, in the general context of white noise theory it is shown to be an anticipative stochastic integral which, under a stronger condition on the weak Gateaux derivative of F is directly related to the Ogawa integral.Research supported by the National Science Foundation and the Air Force Office of Scientific Research Grant No. F49620 92 J 0154 and the Army Research Office Grant No. DAAL 03 92 G 0008. 相似文献
103.
Vsevolod F. Lev 《Combinatorica》1996,16(4):587-590
In this note the method of [5] and a result from [3] are combined to treat the following classical problem: Given a finite setA and an infinite sequenceS (both inZ), what is the minimal number of elements ofA whose sum lies inS? We obtain an upper bound depending only on the densities ofA andS (but not on their arithmetic nature). 相似文献
104.
This paper considers the prescribed scalar curvature problem onS
n
forn>-3. We consider the limits of solutions of the regularization obtained by decreasing the critical exponent. We characterize those subcritical solutions which blow up at the least possible energy level, determining the points at which they can concentrate, and their Morse indices. We then show that forn=3 this is the only blow up which can occur for solutions. We use this in combination with the Morse inequalities for the subcritical problem to obtain a general existence theorem for the prescribed scalar curvature problem onS
3.This article was processed by the author using the
style filepljourlm from Springer-Verlag. 相似文献
105.
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
106.
Jürgen Bokowski António Guedes de Oliviera Ulrich Thiemann António Veloso da Costa 《Geometriae Dedicata》1996,63(1):25-43
We prove a conjecture of Las Vergnas in dimensions d7: The matroid of the d-dimensional cube C
d
has a unique reorientation class. This extends a result of Las Vergnas, Roudneff and Salaün in dimension 4. Moreover, we determine the automorphism group G
d
of the matroid of the d-cube C
d
for arbitrary dimension d, and we discuss its relation to the Coxeter group of C
d
. We introduce matroid facets of the matroid of the d-cube in order to evaluate the order of G
d
. These matroid facets turn out to be arbitrary pairs of parallel subfacets of the cube. We show that the Euclidean automorphism group W
d
is a proper subgroup of the group G
d
of all matroid symmetries of the d-cube by describing genuine matroid symmetries for each Euclidean facet. A main theorem asserts that any one of these matroid symmetries together with the Euclidean Coxeter symmetries generate the full automorphism group G
d
. For the proof of Las Vergnas' conjecture we use essentially these symmetry results together with the fact that the reorientation class of an oriented matroid is determined by the labeled lower rank contractions of the oriented matroid. We also describe the Folkman-Lawrence representation of the vertex figure of the d-cube and a contraction of it. Finally, we apply our method of proof to show a result of Las Vergnas, Roudneff, and Salaün that the matroid of the 24-cell has a unique reorientation class, too. 相似文献
107.
R. Balasubramanian M. Langevin T. N. Shorey M. Waldschmidt 《Monatshefte für Mathematik》1996,121(4):295-307
In this paper we consider an analogue of the problem of Erds and Woods for arithmetic progressions. A positive answer follows from theabc conjecture. Partial results are obtained unconditionally. 相似文献
108.
J. C. Lagarias 《Monatshefte für Mathematik》1993,115(4):299-328
Given a vector of real numbers=(1,...
d
)
d
, the Jacobi-Perron algorithm and related algorithms, such as Brun's algorithm and Selmer's algorithm, produce a sequence of (d+1)×(d+1) convergent matrices {C(n)():n1} whose rows provide Diophantine approximations to . Such algorithms are specified by two mapsT:[0, 1]
d
[0, 1]
d
and A:[0,1]
d
GL(d+1,), which compute convergent matrices C(n)())...A(T())A(). The quality of the Diophantine approximations these algorithms find can be measured in two ways. The best approximation exponent is the upper bound of those values of for which there is some row of the convergent matrices such that for infinitely many values ofn that row of C(n)() has
. The uniform approximation exponent is the upper bound of those values of such that for all sufficiently large values ofn and all rows of C(n)() one has
. The paper applies Oseledec's multiplicative ergodic theorem to show that for a large class of such algorithms and take constant values and on a set of Lebesgue measure one. It establishes the formula where are the two largest Lyapunov exponents attached by Oseledec's multiplicative ergodic theorem to the skew-product (T, A,d), whered is aT-invariant measure, absolutely continuous with respect to Lebesgue measure. We conjecture that holds for a large class of such algorithms. These results apply to thed-dimensional Jacobi-Perron algorithm and Selmer's algorithm. We show that; experimental evidence of Baldwin (1992) indicates (nonrigorously) that. We conjecture that holds for alld2. 相似文献
109.
Martin Goldstern 《Monatshefte für Mathematik》1993,116(3-4):237-243
IfC is a Polish probability space,
a Borel set whose sectionsW
x ( have measure one and are decreasing
, then we show that the set
x
W
x
has measure one. We give two proofs of this theorem—one in the language of set theory, the other in the language of probability theory, and we apply the theorem to a question on completely uniformly distributed sequences.Supported by DFG grant Ko 490/7-1. 相似文献
110.
This paper studies the complexity of computing (or approximating, or bounding) the various inner and outer radii of ann-dimensional convex polytope in the space
n
equipped with an
p
norm or a polytopal norm. The polytopeP is assumed to be presented as the convex hull of finitely many points with rational coordinates (V-presented) or as the intersection of finitely many closed halfspaces defined by linear inequalities with rational coefficients (-presented). The innerj-radius ofP is the radius of a largestj-ball contained inP; it isP's inradius whenj = n and half ofP's diameter whenj = 1. The outerj-radius measures how wellP can be approximated, in a minimax sense, by an (n — j)-flat; it isP's circumradius whenj = n and half ofP's width whenj = 1. The binary (Turing machine) model of computation is employed. The primary concern is not with finding optimal algorithms, but with establishing polynomial-time computability or NP-hardness. Special attention is paid to the case in whichP is centrally symmetric. When the dimensionn is permitted to vary, the situation is roughly as follows: (a) for general -presented polytopes in
p
spaces with 1
相似文献