全文获取类型
收费全文 | 5785篇 |
免费 | 170篇 |
国内免费 | 106篇 |
专业分类
化学 | 692篇 |
晶体学 | 44篇 |
力学 | 64篇 |
综合类 | 16篇 |
数学 | 3401篇 |
物理学 | 1199篇 |
综合类 | 645篇 |
出版年
2023年 | 14篇 |
2022年 | 25篇 |
2021年 | 27篇 |
2020年 | 28篇 |
2019年 | 68篇 |
2018年 | 74篇 |
2017年 | 51篇 |
2016年 | 44篇 |
2015年 | 60篇 |
2014年 | 119篇 |
2013年 | 320篇 |
2012年 | 149篇 |
2011年 | 225篇 |
2010年 | 223篇 |
2009年 | 395篇 |
2008年 | 412篇 |
2007年 | 406篇 |
2006年 | 316篇 |
2005年 | 248篇 |
2004年 | 272篇 |
2003年 | 254篇 |
2002年 | 182篇 |
2001年 | 148篇 |
2000年 | 141篇 |
1999年 | 268篇 |
1998年 | 128篇 |
1997年 | 106篇 |
1996年 | 124篇 |
1995年 | 98篇 |
1994年 | 134篇 |
1993年 | 118篇 |
1992年 | 105篇 |
1991年 | 87篇 |
1990年 | 57篇 |
1989年 | 60篇 |
1988年 | 48篇 |
1987年 | 53篇 |
1986年 | 44篇 |
1985年 | 70篇 |
1984年 | 47篇 |
1983年 | 37篇 |
1982年 | 49篇 |
1981年 | 42篇 |
1980年 | 42篇 |
1979年 | 23篇 |
1978年 | 28篇 |
1977年 | 29篇 |
1976年 | 33篇 |
1975年 | 9篇 |
1973年 | 8篇 |
排序方式: 共有6061条查询结果,搜索用时 31 毫秒
31.
Qingrong Zheng Gang Su Jian Wang Hong Guo 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,25(2):233-238
We report a theoretical analysis of the phonon thermal conductance, κ(T), for single wall carbon nanotubes (SWCN). In a range of low temperatues up to 100 K, κ(T) of perfect SWCN is found to increase with temperature, approximately, in a parabolic fashion. This is qualitatively consistent
with recent experimental measurements where the tube-tube interactions are negligibly weak. When the carbon-carbon bond length
is slightly varied, κ(T) is found to be qualitatively unaltered which implies that the anharmonic effect does not change the qualitative behavior
of κ(T).
Received 12 June 2001 相似文献
32.
For a general K3 surface S of genus g, with 2 ≤ g ≤ 10, we prove that the intermediate Jacobians of the family of prime Fano threefolds of genus g containing S as a hyperplane section, form generically an algebraic completely integrable Hamiltonian system.
The first author is partially supported by grant MI1503/2005 of the Bulgarian Foundation for Scientific Research. 相似文献
33.
ZHANGZHAOJI 《高校应用数学学报(英文版)》1995,10(3):357-359
This paper solves an open problem of Vaserstein. The main result is: the equation x^m y^m=z^m has a solution in SL2z if and only if m is not divisible by 4 or 6 and m is not congruent to 3 modulo 6. 相似文献
34.
T. Charitat B. Fourcade 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,1(3):333-336
An o-ring takes spontaneously the shape of a chair when strong enough torsion is applied in its tangent plane. This state
is metastable, since work has to be done on the o-ring to return to the circular shape. We show that this metastable state
exists in a Hamiltonian where curvature and torsion are coupled via an intrinsic curvature term. If the o-ring is constrained to be planar (2d case), this metastable state displays a kink-anti-kink
pair. This state is metastable if the ratio is less than , where C and A are the torsion and the bending elastic constants [#!landau!#]. In three dimensions, our variational approach shows that
. This model can be generalized to the case where the bend is induced by a concentration field which follows the variations
of the curvature.
Received: 27 August 1997 / Revised: 23 October 1997 / Accepted: 12 November 1997 相似文献
35.
关于非齐次m阶马氏信源的渐近均分割性 总被引:4,自引:0,他引:4
本文研究非齐次m阶马氏信源的渐近均分割性,首先我们得到关于此种信源m 1元函数的一类强极限定理,作为推论,得到关于任意非齐次m阶马氏信源状态和熵密度的几个极限定理,最后得到一类非齐次m阶马氏信源的渐近均分割性。 相似文献
36.
We develop a lattice-dynamical model based on the screw symmetry of single-walled carbon nanotubes that allows for reducing the size of the dynamical matrix to six, for all tube chiralities. The model uses force constants derived from fitting to the phonon dispersion of 2D graphite. We present the calculation procedure in a clear and transparent way, making the model easier to follow. We calculate the phonon dispersions of a number of nanotubes of different chiralities. The splitting of two highest Raman active modes and the radial breathing mode frequency are studied by changing the tube diameter and chirality. 相似文献
37.
Brian A. Hagler 《Linear algebra and its applications》2007,422(1):100-118
Definitions, theorems and examples are established for a general model of Laurent polynomial spaces and ordered orthogonal Laurent polynomial sequences, ordered with respect to ordered bases and orthogonal with respect to inner products ·=L°⊙ decomposed into transition functional ⊙ and strong moment functional, or, more generally, sample functional L couplings. Under this formulation that is shown to subsume those in the existing literature, new fundamental results are produced, including necessary and sufficient conditions for ordered OLPS to be sequences of nth numerators of continued fractions, in contrast to the classical result concerning nth denominators which is shown to hold only in special cases. 相似文献
38.
A.V. Arhangel'skii 《Topology and its Applications》2007,154(3):625-634
We introduce a new cardinal invariant, core of a space, defined for any locally compact Hausdorff space X and denoted by cor(X). Locally compact spaces of countable core generalize locally compact σ-compact spaces in a way that is slightly exotic, but still quite natural. We show in Section 1 that under a broad range of conditions locally compact spaces of countable core must be σ-compact. In particular, normal locally compact spaces of countable core and realcompact locally compact spaces of countable core are σ-compact. Perfect mappings preserve the class of spaces of countable core in both directions (Section 2). The Alexandroff compactification aX is weakly first countable at the Alexandroff point a if and only if cor(X)=ω (Section 3). Two examples of non-σ-compact locally compact spaces of countable core are discussed in Section 3. We also extend the well-known theorem of Alexandroff and Urysohn on the cardinality of perfectly normal compacta to compacta satisfying a weak version of perfect normality. Several open problems are formulated. 相似文献
39.
Abdelhadi Es-Sarhir 《Journal of Differential Equations》2007,233(1):87-104
This paper deals with perturbations of the Ornstein-Uhlenbeck operator on L2-spaces with respect to a Gaussian measure μ. We perturb the generator of the Ornstein-Uhlenbeck semigroup by a certain unbounded, non-linear drift, and show various properties of the perturbed semigroup such as compactness and positivity. Strong Feller property, existence and uniqueness of an invariant measure are discussed as well. 相似文献
40.