全文获取类型
收费全文 | 9271篇 |
免费 | 278篇 |
国内免费 | 243篇 |
专业分类
化学 | 1185篇 |
晶体学 | 65篇 |
力学 | 58篇 |
综合类 | 30篇 |
数学 | 5819篇 |
物理学 | 847篇 |
综合类 | 1788篇 |
出版年
2023年 | 27篇 |
2022年 | 70篇 |
2021年 | 53篇 |
2020年 | 59篇 |
2019年 | 173篇 |
2018年 | 190篇 |
2017年 | 111篇 |
2016年 | 109篇 |
2015年 | 125篇 |
2014年 | 270篇 |
2013年 | 507篇 |
2012年 | 326篇 |
2011年 | 632篇 |
2010年 | 455篇 |
2009年 | 543篇 |
2008年 | 644篇 |
2007年 | 691篇 |
2006年 | 560篇 |
2005年 | 485篇 |
2004年 | 424篇 |
2003年 | 405篇 |
2002年 | 331篇 |
2001年 | 269篇 |
2000年 | 240篇 |
1999年 | 231篇 |
1998年 | 222篇 |
1997年 | 147篇 |
1996年 | 167篇 |
1995年 | 178篇 |
1994年 | 156篇 |
1993年 | 135篇 |
1992年 | 111篇 |
1991年 | 78篇 |
1990年 | 98篇 |
1989年 | 63篇 |
1988年 | 55篇 |
1987年 | 50篇 |
1986年 | 30篇 |
1985年 | 67篇 |
1984年 | 47篇 |
1983年 | 38篇 |
1982年 | 49篇 |
1981年 | 45篇 |
1980年 | 26篇 |
1979年 | 13篇 |
1978年 | 23篇 |
1977年 | 21篇 |
1976年 | 17篇 |
1975年 | 9篇 |
1974年 | 7篇 |
排序方式: 共有9792条查询结果,搜索用时 328 毫秒
41.
42.
Teruhisa Tsuda 《Letters in Mathematical Physics》2006,77(1):21-30
Starting from certain point sets in the projective plane, we construct a tropical (or subtraction-free birational) representation of Weyl groups over the field of τ-functions. In particular, our construction includes E
8
(1)
, E
7
(1)
, E
6
(1)
and D
5
(1)
as affine cases; each of them gives rise to the q-difference Painlevé equation. 相似文献
43.
We prove a conjecture by F. Ferrari. Let X be the total space of a nonlinear deformation of a rank two holomorphic vector bundle on a smooth rational curve, such that X has trivial canonical bundle and has sections. Then the normal bundle to such sections is computed in terms of the rank of the Hessian of a suitably defined superpotential at its critical points. 相似文献
44.
New criteria are provided for determining whether an integral representation of a stable process is minimal. These criteria are based on various nonminimal sets and their projections, and have several advantages over and shed light on already available criteria. In particular, they naturally lead from a nonminimal representation to the one which is minimal. Several known examples are considered to illustrate the main results. The general approach is also adapted to show that the so-called mixed moving averages have a minimal integral representation of the mixed moving average type. 相似文献
45.
Hirofumi Tsumura 《Journal of Number Theory》2004,106(1):155-168
In this paper, we define the multiple Euler numbers and consider some multiple harmonic series of Mordell-Tornheim's type, which is a partial sum of the Mordell-Tornheim zeta series defined by Matsumoto. Indeed, we prove a certain reducibility of these series as well as the multiple zeta values. 相似文献
46.
Kan Hachiya 《Journal of Non》2003,321(3):217-224
First-principles calculations of the electronic structures of the wrong bonds were performed for amorphous germanium sulphides in order to explain their compositional dependence. Model cluster calculations of the density of states using a set of geometry similar to the crystalline-GeS2 coordination can reproduce the peak structure of the experimental valence band photoemission spectra. The bonding and anti-bonding states of the covalent Ge-S bonds form valence and conduction band respectively, and the top of the valence band is occupied with S 3p lone-pair states. The bonding states are modified by S-S bonds and the anti-bonding states are modified by Ge-Ge bonds, mainly through their hybridization with the wrong-bond states between p-orbitals. The lone-pair states do not interact either of them to form a different band, and obscure the modification induced by the S-S wrong bonds. Therefore, we can conclude that the narrowing of the bandgap with increasing Ge content from GeS2 composition is due to that of the conduction-band bottom with increasing germanium wrong bonds, though the narrowing with increasing S content is moderate due to the presence of the lone-pair states at the valence-band top. 相似文献
47.
R. Weidmann 《Archiv der Mathematik》2003,81(5):589-595
We describe a family of graph manifolds that have 2-generated
fundamental group but do not admit a Heegaard splitting of genus 2. They are
closely related to the examples provided by Boileau and Zieschang if these are
considered as (non-proper) graph manifolds.Received: 14 August 2002 相似文献
48.
Rashmi 《Solid State Communications》2005,134(3):217-222
A detailed analysis of nonlinear effects-electron switching and rectification, in InAlAs/InGaAs based Y-branch junction (YBJ) devices is presented to investigate the potential of YBJ for high frequency applications at 300 K. Results based on semi-classical simulations yield good qualitative agreement with measurements and previously reported theoretical and experimental results. The nonlinear parabolic behaviour of our device is attributed to device geometry and space charge effects. RF analysis shows that the YBJ has tremendous intrinsic potential to function as a frequency doubler and microwave rectifier when operated in the parabolic regime. The present analysis serves as a tool to optimize the bias conditions for RF measurements and to estimate the effect of interconnects and parasitic elements on the RF performance of real devices. 相似文献
49.
Yasufumi Hashimoto 《Journal of Number Theory》2007,122(2):324-335
In [P. Sarnak, Class numbers of indefinite binary quadratic forms, J. Number Theory 15 (1982) 229-247], it was proved that the Selberg zeta function for SL2(Z) is expressed in terms of the fundamental units and the class numbers of the primitive indefinite binary quadratic forms. The aim of this paper is to obtain similar arithmetic expressions of the logarithmic derivatives of the Selberg zeta functions for congruence subgroups of SL2(Z). As applications, we study the Brun-Titchmarsh type prime geodesic theorem and the asymptotic formula of the sum of the class number. 相似文献
50.
Summary.
This paper is concerned with a high order convergent
discretization for the semilinear reaction-diffusion problem:
,
for , subject to ,
where .
We assume that on
, which
guarantees uniqueness of a solution to
the problem. Asymptotic properties of
this solution are discussed. We consider a
polynomial-based three-point
difference scheme on a simple piecewise
equidistant mesh of Shishkin type.
Existence and local uniqueness of a solution
to the scheme are analysed. We
prove that the scheme is almost fourth order
accurate in the discrete maximum
norm, uniformly in the perturbation parameter
. We present numerical
results in support of this result.
Received February 25, 1994 相似文献