全文获取类型
收费全文 | 11722篇 |
免费 | 294篇 |
国内免费 | 285篇 |
专业分类
化学 | 1962篇 |
晶体学 | 79篇 |
力学 | 68篇 |
综合类 | 21篇 |
数学 | 9197篇 |
物理学 | 974篇 |
出版年
2023年 | 44篇 |
2022年 | 66篇 |
2021年 | 72篇 |
2020年 | 99篇 |
2019年 | 281篇 |
2018年 | 275篇 |
2017年 | 138篇 |
2016年 | 130篇 |
2015年 | 150篇 |
2014年 | 338篇 |
2013年 | 646篇 |
2012年 | 358篇 |
2011年 | 761篇 |
2010年 | 671篇 |
2009年 | 740篇 |
2008年 | 824篇 |
2007年 | 880篇 |
2006年 | 699篇 |
2005年 | 472篇 |
2004年 | 405篇 |
2003年 | 379篇 |
2002年 | 299篇 |
2001年 | 245篇 |
2000年 | 230篇 |
1999年 | 286篇 |
1998年 | 285篇 |
1997年 | 227篇 |
1996年 | 242篇 |
1995年 | 275篇 |
1994年 | 230篇 |
1993年 | 226篇 |
1992年 | 189篇 |
1991年 | 108篇 |
1990年 | 123篇 |
1989年 | 126篇 |
1988年 | 81篇 |
1987年 | 62篇 |
1986年 | 61篇 |
1985年 | 90篇 |
1984年 | 86篇 |
1983年 | 60篇 |
1982年 | 76篇 |
1981年 | 50篇 |
1980年 | 43篇 |
1979年 | 51篇 |
1978年 | 43篇 |
1977年 | 21篇 |
1976年 | 19篇 |
1975年 | 14篇 |
1974年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
51.
Consider the problem of three point vortices (also called Helmholtz’ vortices) on a plane, with arbitrarily given vorticities.
The interaction between vortices is proportional to 1/r, where r is the distance between two vortices. The problem has 2 equilateral and at most 3 collinear normalized relative equilibria.
This 3 is the optimal upper bound. Our main result is that the above standard statements remain unchanged if we consider an
interaction proportional to r
b, for any b < 0. For 0 < b < 1, the optimal upper bound becomes 5. For positive vorticities and any b < 1, there are exactly 3 collinear normalized relative equilibria. The case b = −2 of this last statement is the well-known theorem due to Euler: in the Newtonian 3-body problem, for any choice of the
3 masses, there are 3 Euler configurations (also known as the 3 Euler points). These small upper bounds strengthen the belief
of Kushnirenko and Khovanskii [18]: real varieties defined by simple systems should have a simple topology. We indicate some
hard conjectures about the configurations of relative equilibrium and suggest they could be attacked within the quasi-polynomial
framework. 相似文献
52.
Piet Borst 《Topology and its Applications》2007,154(3):665-674
We comment on the definition of C-spaces in [D.F. Addis, J.H. Gresham, A class of infinite-dimensional spaces. Part I: Dimension theory and Alexandroff's Problem, Fund. Math. 101 (1978) 195-205] and [W.E. Haver, A covering property for metric spaces, in: Topology Conference at Virginia Polytechnic Institute 1973, in: Lecture Notes in Math., vol. 375, 1974, pp. 108-113]. Furthermore we introduce two types of ‘finite’ C-spaces one of which gives an internal characterization of all spaces having a metrizable compactification satisfying property C. We also introduce a transfinite dimension function for those finite C-spaces. Several questions arise that are related to Alexandrov's problem. 相似文献
53.
In a structural measurement error model the structural quasi-score (SQS) estimator is based on the distribution of the latent regressor variable. If this distribution is misspecified, the SQS estimator is (asymptotically) biased. Two types of misspecification are considered. Both assume that the statistician erroneously adopts a normal distribution as his model for the regressor distribution. In the first type of misspecification, the true model consists of a mixture of normal distributions which cluster around a single normal distribution, in the second type, the true distribution is a normal distribution admixed with a second normal distribution of low weight. In both cases of misspecification, the bias, of course, tends to zero when the size of misspecification tends to zero. However, in the first case the bias goes to zero in a flat way so that small deviations from the true model lead to a negligible bias, whereas in the second case the bias is noticeable even for small deviations from the true model. 相似文献
54.
Oliver Lorscheid 《Archiv der Mathematik》2007,88(4):344-348
This paper shows that for a local field K, a subfield k ⊂ K and a variety X over k, X is complete if and only if for every finite field extension Kʹ | K, the set X(Kʹ) is compact in its strong topology.
The author likes to thank Florian Pop, Jakob Stix, Stefan Wewers, Gunther Cornelissen and his own parents for their support.
Received: 13 April 2006 相似文献
55.
The large deviation theorems, exponential inequalities and a non-uniform estimate of the Berry–Esséen theorem in a discounted version are proved.Dedicated to Professor Vytautas Statulevičius on the occasion of his 75th birthday. 相似文献
56.
Zhijun Yi Tingyu LiuQiren Zhang Yuanyuan Sun 《Journal of Electron Spectroscopy and Related Phenomena》2006
The electronic structures of PbWO4 crystals containing F type color centers with the lattice structure optimized are studied within the framework of the fully relativistic self-consistent Direc–Slater theory, using a numerically discrete variational (DV-Xα) method. The calculated results show that F and F+ centers have donor energy level in forbidden band. Their optical transition energy are 1.84 eV, 2.21 eV, respectively, which corresponds to the 680 nm, 550 nm absorption bands. It predicts that the 680 nm, 550 nm absorption bands originate form the F and F+ centers in PbWO4 crystals. 相似文献
57.
58.
Single Qubit and Its Universal Logic Gate Made of a Heisenberg Spin Cluster with Five Particles
下载免费PDF全文
![点击此处可从《中国物理快报》网站下载免费的PDF全文](/ch/ext_images/free.gif)
We investigate an anisotropic Heisenberg spin cluster with five particles controlled by a time-dependent magnetic field. With the algebraic dynamical method, we obtain the exact analytical solution to the time dependent Schr6dinger equation. Based on the analytical solution, it is shown that the system can be used as a universal single qubit logic gate controlled by the strength and frequency of the magnetic field, and the six special single qubit logic gates can be realized physically. We also discuss the anti-decoherence property of the qubit and its logic gates resulted from particle coupling effect and collectivity of the cluster. 相似文献
59.
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
60.
Jan P. Boroński 《Topology and its Applications》2007,154(18):3156-3166
A set (or a collection of sets) contained in the Euclidean space Rm is symmetric if it is invariant under the antipodal map. Given a symmetric unicoherent polyhedron X (like an n-dimensional cube or a sphere) and an odd real function f defined on vertices of a certain symmetric triangulation of X, we algorithmically construct a connected symmetric separator of X by choosing a subcollection of the triangulation. Each element of the subcollection contains the vertices v and u such that f(v)f(u)?0. 相似文献