全文获取类型
收费全文 | 6669篇 |
免费 | 527篇 |
国内免费 | 877篇 |
专业分类
化学 | 2710篇 |
晶体学 | 69篇 |
力学 | 135篇 |
综合类 | 73篇 |
数学 | 1132篇 |
物理学 | 1634篇 |
综合类 | 2320篇 |
出版年
2024年 | 6篇 |
2023年 | 47篇 |
2022年 | 81篇 |
2021年 | 96篇 |
2020年 | 121篇 |
2019年 | 126篇 |
2018年 | 124篇 |
2017年 | 165篇 |
2016年 | 176篇 |
2015年 | 141篇 |
2014年 | 248篇 |
2013年 | 375篇 |
2012年 | 358篇 |
2011年 | 395篇 |
2010年 | 277篇 |
2009年 | 366篇 |
2008年 | 380篇 |
2007年 | 448篇 |
2006年 | 388篇 |
2005年 | 367篇 |
2004年 | 326篇 |
2003年 | 317篇 |
2002年 | 278篇 |
2001年 | 254篇 |
2000年 | 237篇 |
1999年 | 213篇 |
1998年 | 189篇 |
1997年 | 186篇 |
1996年 | 187篇 |
1995年 | 162篇 |
1994年 | 147篇 |
1993年 | 101篇 |
1992年 | 130篇 |
1991年 | 132篇 |
1990年 | 100篇 |
1989年 | 99篇 |
1988年 | 83篇 |
1987年 | 56篇 |
1986年 | 40篇 |
1985年 | 25篇 |
1984年 | 20篇 |
1983年 | 10篇 |
1982年 | 19篇 |
1981年 | 18篇 |
1980年 | 11篇 |
1979年 | 12篇 |
1978年 | 8篇 |
1977年 | 6篇 |
1976年 | 9篇 |
1973年 | 6篇 |
排序方式: 共有8073条查询结果,搜索用时 15 毫秒
31.
We give a number of characterizations of bodies of constant width in arbitrary dimension. As an application, we describe a way to construct a body of constant width in dimension n, one of its (n – 1)‐dimensional projection being given. We give a number of examples, like a four‐dimensional body of constant width whose 3D‐projection is the classical Meissner's body. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
32.
We study the generalization of the Willmore functional for surfaces in the three-dimensional Heisenberg group. Its construction is based on the spectral theory of the Dirac operator entering into theWeierstrass representation of surfaces in this group. Using the surfaces of revolution we demonstrate that the generalization resembles the Willmore functional for the surfaces in the Euclidean space in many geometrical aspects. We also observe the relation of these functionals to the isoperimetric problem. 相似文献
33.
根据对一些学生的日常阅读情况的观察和阅读理论最新的研究成果 ,以及心理学的相关理论的分析 ,提出应该加强捷效寻读技能的教学 ,从理论和实践上提出了相应的方法。 相似文献
34.
Titius—Bode定则的发展,天体量子论和泛量子理论 总被引:14,自引:5,他引:9
张一方 《云南大学学报(自然科学版)》1993,15(4):297-303
太阳系的Titius-Bode定则可以发展为r_n=an~2,令α_1=0.042,n=3,4,5,6是类地行星;令α_2=1.2,n=2,3,4,5,6是类木行星。此时海王星、冥王星都是规则的,且适用于大多数卫星。由此可以完全类比于玻尔原子模型,并得出太阳系量子常数H=(αGM_⊙)~(1/2)和天体薛定谔方程。这样距离规则是行星演化时统计性的结果,宇宙中应普遍存在波粒二象性和形式相似而量子常数各不相同的泛量子理论。 相似文献
35.
Attapol Kaewkhao 《Journal of Mathematical Analysis and Applications》2007,333(2):950-958
We give some sufficient conditions for the Domínguez-Lorenzo condition in terms of the James constant, the Jordan-von Neumann constant, and the coefficient of weak orthogonality. As a consequence, we obtain fixed point theorems for multivalued nonexpansive mappings. 相似文献
36.
Considering external electric field as well as third- and fourth-order phonon anharmonic interaction terms in the pseudospin-lattice
coupled mode (PLCM) model Hamiltonian for KDP-type ferroelectrics, expressions for field-dependent shift, width, renormalized
soft mode frequency, Curie temperature, dielectric constant and dielectric loss are evaluated. For the calculation, method
of statistical double-time temperature-dependent Green’s function has been used. By fitting model values of physical quantities,
temperature and electric field dependences of soft mode frequency, dielectric constant and loss have been calculated which
compare well with experimental results of Baumgartner [8] and Choi and Lockwood [9]. Both dielectric constant and loss decrease
with electric field. 相似文献
37.
B. G. Sidharth 《Foundations of Physics Letters》2006,19(6):611-617
In this note we consider a variable G cosmology which is consistent with observation and which had successfully predicted an ever expanding accelerating universe
with a small cosmological constant amongst other things. Three further tests are proposed in this note: First, the inexplicable
anomalous accelerations of the Pioneer spacecrafts can be explained. It is then shown that the observed shortening of the
orbital periods of binary pulsars is in good agreement with this model. Finally, more general changes in orbital parameters
are deduced, which may be observed in the future. 相似文献
38.
In this note we study constant mean curvature surfaces in asymptotically flat 3-manifolds. We prove that, outside a given compact subset in an asymptotically flat 3-manifold with positive mass, stable spheres of given constant mean curvature are unique. Therefore we are able to conclude that the foliation of stable spheres of constant mean curvature in an asymptotically flat 3-manifold with positive mass outside a given compact subset is unique.
39.
Given a constant of motion for the one-dimensional harmonic oscillator with linear dissipation in the velocity, the problem to get the Hamiltonian for this system is pointed out, and the quantization up to second order in the perturbation approach is used to determine the modification on the eigenvalues when dissipation is taken into consideration. This quantization is realized using the constant of motion instead of the Hamiltonian.
PACS: 03.20.+i, 03.30.+p, 03.65.−w,03.65.Ca 相似文献
40.
A. S. Belenky 《Mathematical and Computer Modelling》2002,36(11-13)
Two games of interacting between a coalition of players in a marketplace and the residual players acting there are discussed, along with two approaches to fair imputation of gains of coalitions in cooperative games that are based on the concepts of the Shapley vector and core of a cooperative game. In the first game, which is an antagonistic one, the residual players try to minimize the coalition's gain, whereas in the second game, which is a noncooperative one, they try to maximize their own gain as a coalition. A meaningful interpretation of possible relations between gains and Nash equilibrium strategies in both games considered as those played between a coalition of firms and its surrounding in a particular marketplace in the framework of two classes of n-person games is presented. A particular class of games of choosing partners and forming coalitions in which models of firms operating in the marketplace are those with linear constraints and utility functions being sums of linear and bilinear functions of two corresponding vector arguments is analyzed, and a set of maximin problems on polyhedral sets of connected strategies which the problem of choosing a coalition for a particular firm is reducible to are formulated based on the firm models of the considered kind. 相似文献