全文获取类型
收费全文 | 80224篇 |
免费 | 402篇 |
国内免费 | 391篇 |
专业分类
化学 | 25404篇 |
晶体学 | 814篇 |
力学 | 6862篇 |
数学 | 32227篇 |
物理学 | 15710篇 |
出版年
2022年 | 44篇 |
2021年 | 54篇 |
2020年 | 41篇 |
2019年 | 46篇 |
2018年 | 10445篇 |
2017年 | 10276篇 |
2016年 | 6093篇 |
2015年 | 897篇 |
2014年 | 370篇 |
2013年 | 434篇 |
2012年 | 3920篇 |
2011年 | 10653篇 |
2010年 | 5734篇 |
2009年 | 6132篇 |
2008年 | 6746篇 |
2007年 | 8857篇 |
2006年 | 349篇 |
2005年 | 1411篇 |
2004年 | 1613篇 |
2003年 | 2031篇 |
2002年 | 1088篇 |
2001年 | 306篇 |
2000年 | 350篇 |
1999年 | 187篇 |
1998年 | 223篇 |
1997年 | 164篇 |
1996年 | 237篇 |
1995年 | 150篇 |
1994年 | 109篇 |
1993年 | 132篇 |
1992年 | 82篇 |
1991年 | 98篇 |
1990年 | 71篇 |
1989年 | 77篇 |
1988年 | 82篇 |
1987年 | 73篇 |
1986年 | 72篇 |
1985年 | 65篇 |
1984年 | 61篇 |
1983年 | 57篇 |
1982年 | 57篇 |
1981年 | 48篇 |
1980年 | 51篇 |
1979年 | 54篇 |
1978年 | 45篇 |
1914年 | 45篇 |
1913年 | 40篇 |
1912年 | 40篇 |
1909年 | 41篇 |
1908年 | 40篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
951.
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
952.
Osamu Hatori Takeshi Miura Rumi Shindo Hiroyuki Takagi 《Rendiconti del Circolo Matematico di Palermo》2010,59(2):161-183
Let $
A
$
A
and ℬ be unital semisimple commutative Banach algebras. It is shown that if surjections S,T: $
A
$
A
→ ℬ with S(1)=T(1)= 1 and α ∈ ℂ \ {0} satisfy r(S(a)T(b) − α)= r(ab− α) for all a,b ∈ $
A
$
A
, then S=T and S is a real algebra isomorphism, where r(a) is the spectral radius of a. Let I be a nonempty set, A and B be uniform algebras. Let ρ, τ: I → A and S,T: I → B be maps satisfying σ
π
(S(p)T(q)) ⊂ σ
π
(ρ(p) τ(q)) for all p,q ∈ I, where σ
π
(f) is the peripheral spectrum of f. Suppose that the ranges ρ(I), τ(I) ⊂ A and S(I),T(I) ⊂ B are closed under multiplication in a sense, and contain peaking functions “enough”. There exists a homeomorphism ϕ: Ch(B)→Ch(A) such that S(p)(y)= ρ(p)(ϕ(y)) and T(p)(y)= τ(p)(ϕ(y)) for every p ∈ I and y ∈ Ch(B), where Ch(A) is the Choquet boundary of A. 相似文献
953.
Quadratic assignment problems (QAPs) are known to be among the hardest discrete optimization problems. Recent study shows
that even obtaining a strong lower bound for QAPs is a computational challenge. In this paper, we first discuss how to construct
new simple convex relaxations of QAPs based on various matrix splitting schemes. Then we introduce the so-called symmetric
mappings that can be used to derive strong cuts for the proposed relaxation model. We show that the bounds based on the new
models are comparable to some strong bounds in the literature. Promising experimental results based on the new relaxations
are reported. 相似文献
954.
Galina Irzhanovna Bizhanova 《Journal of Mathematical Sciences》2010,171(1):9-21
The first and second one-dimensional boundary-value problems for parabolic equations are investigated in the case where the conjugation conditions for all required orders are not satisfied. The existence and uniqueness are proved. Estimates of solutions in classical and weighted Hölder spaces are obtained. We prove that the violation of conjugation for the given functions on the boundary of the domain at the initial-time moment causes the appearance of singular solutions. The order of singularity (as a power of t) is found for the singular solutions for t = 0. 相似文献
955.
The operator norms of weighted Hardy operators on Morrey spaces are worked out. The other purpose of this paper is to establish
a sufficient and necessary condition on weight functions which ensures the boundedness of the commutators of weighted Hardy
operators (with symbols in BMO(ℝ
n
)) on Morrey spaces. 相似文献
956.
Finitary Markov processes are described in G. Morvai and B. Weiss, Prediction for discrete time series, Probability Theory and Related Fields 132 (2005), 1–12. The transition functions of finitary Markov processes are residually locally constant g-functions that can be extended by continuity to their maximal domain of definition. The study of their associated symbolic
dynamics leads one to the D-shifts as introduced in W. Krieger, On g-functions for subshifts, Institute of Mathematical Statistics Lecture Notes-Monograph Series, Vol. 48, Dynamics & Stochastics, arXiv:math.DS/0608259,
(2006), 306–316, We study the phenomena that can arise in residually locally constant and locally constant maximally defined
g-functions on D-shifts, Markov shifts and synchronizing systems with respect to future measures and g-measures 相似文献
957.
We investigate the relationship between the Gröbner-Shirshov bases in free associative algebras, free left modules and “double-free” left modules (that is, free modules over a free algebra). We first give Chibrikov’s Composition-Diamond lemma for modules and then we show that Kang-Lee’s Composition-Diamond lemma follows from it. We give the Gröbner-Shirshov bases for the following modules: the highest weight module over a Lie algebra sl 2, the Verma module over a Kac-Moody algebra, the Verma module over the Lie algebra of coefficients of a free conformal algebra, and a universal enveloping module for a Sabinin algebra. As applications, we also obtain linear bases for the above modules. 相似文献
958.
We consider the median regression with a LASSO-type penalty term for variable selection. With the fixed number of variables
in regression model, a two-stage method is proposed for simultaneous estimation and variable selection where the degree of
penalty is adaptively chosen. A Bayesian information criterion type approach is proposed and used to obtain a data-driven
procedure which is proved to automatically select asymptotically optimal tuning parameters. It is shown that the resultant
estimator achieves the so-called oracle property. The combination of the median regression and LASSO penalty is computationally
easy to implement via the standard linear programming. A random perturbation scheme can be made use of to get simple estimator
of the standard error. Simulation studies are conducted to assess the finite-sample performance of the proposed method. We
illustrate the methodology with a real example. 相似文献
959.
Branko Sarić 《Czechoslovak Mathematical Journal》2010,60(4):1043-1048
Let [a, b] be an interval in ℝ Rand let F be a real valued function defined at the endpoints of [a, b] and with a certain number of discontinuities within [a, b]. Assuming F to be differentiable on a set [a, b] | E to the derivative f, where E is a subset of [a, b] at whose points F can take values ±∞ or not be defined at all, we adopt the convention that F and f are equal to 0 at all points of E and show that KH-vt ∝
a
b
f = F(b) − F(a), where KH-vt denotes the total value of the Kurzweil-Henstock integral. The paper ends with a few examples that illustrate the theory. 相似文献
960.
Ivan Feshchenko Danylo Radchenko Lev Radzivilovsky Maksym Tantsiura 《Geometriae Dedicata》2010,145(1):159-168
Consider the set of all lengths of sides of an N-dimensional parallelepiped. If this set has no more than k elements, the parallelepiped will be called a bar (the definition of a bar depends on k). We prove that a parallelepiped can be dissected into a finite number of bars if and only if the lengths of its sides span
a linear space of dimension at most k over
\mathbb Q{{\mathbb Q}} . This extends and generalizes a well-known theorem of Max Dehn about the splitting of rectangles into squares. Several other
results about dissections of parallelepipeds are obtained. 相似文献