全文获取类型
收费全文 | 15714篇 |
免费 | 2182篇 |
国内免费 | 1990篇 |
专业分类
化学 | 6201篇 |
晶体学 | 282篇 |
力学 | 301篇 |
综合类 | 93篇 |
数学 | 1301篇 |
物理学 | 11708篇 |
出版年
2024年 | 32篇 |
2023年 | 124篇 |
2022年 | 372篇 |
2021年 | 406篇 |
2020年 | 306篇 |
2019年 | 388篇 |
2018年 | 373篇 |
2017年 | 497篇 |
2016年 | 704篇 |
2015年 | 652篇 |
2014年 | 884篇 |
2013年 | 1537篇 |
2012年 | 999篇 |
2011年 | 1153篇 |
2010年 | 907篇 |
2009年 | 1120篇 |
2008年 | 1044篇 |
2007年 | 1130篇 |
2006年 | 920篇 |
2005年 | 868篇 |
2004年 | 676篇 |
2003年 | 629篇 |
2002年 | 543篇 |
2001年 | 478篇 |
2000年 | 470篇 |
1999年 | 426篇 |
1998年 | 304篇 |
1997年 | 310篇 |
1996年 | 286篇 |
1995年 | 227篇 |
1994年 | 174篇 |
1993年 | 171篇 |
1992年 | 181篇 |
1991年 | 98篇 |
1990年 | 78篇 |
1989年 | 82篇 |
1988年 | 78篇 |
1987年 | 44篇 |
1986年 | 26篇 |
1985年 | 30篇 |
1984年 | 21篇 |
1983年 | 15篇 |
1982年 | 19篇 |
1981年 | 16篇 |
1980年 | 14篇 |
1979年 | 17篇 |
1976年 | 7篇 |
1975年 | 7篇 |
1974年 | 9篇 |
1973年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
A complete study of the spectrum of a finite-dimensional Bose operator is carried out in the paper. The cases in which the
spectrum is discrete or continuous are studied.
Translated fromMatematicheskie Zametki, Vol. 61, No. 6, pp. 835–854, June, 1997.
Translated by A. M. Chebotarev 相似文献
22.
谱任意的符号模式矩阵 总被引:1,自引:0,他引:1
一个n阶符号模式矩阵A称为是谱任意的,如果对任意的实系数n次首1多项式r(x),在A的定性矩阵类Q(A)中至少存在一个实矩阵B,使得B的特征多项式是r(x),文中证明了当n为奇数时n阶谱任意符号模式矩阵是存在的。 相似文献
23.
The refractive indices (n) of eight standard oils from Physikalisch Technische Bundesanstalt, Germany were determined with an accuracy of ±1×10−4 by using Abbe Refractometer. The measurements were performed at temperature 20°C in the spectral range 0.4–0.7 μm. The experimental data were fitted to the simple Cauchy dispersion formula and the results were found to be consistent within the limits of experimental error. In all cases, the refractive index decreased monotonically with increasing wavelength. The refractive indices (n) of these oils have been measured as a function of the temperature t (20°C up to 50°C) at λ=0.589 μm and were found to have linear temperature dependencies. The refractive indices of the studied oils and the uncertainty in their values are calculated at λ=0.589. The Lorentz–Lorenz (L–L) formula has been tested and it was found to be valid with a maximum deviation of 0.4% and was used to calculate the molecular polarizability θ. 相似文献
24.
3d-metal antimonides: Fe1+x Sb, N+x Sb, Co+x Sb and the (Ni1?y Fe y )Sb solid solution have been studied by the Mössbauer effect method at 57Fe and 119Sn. It was found that the quadrupole interactions at the Fe and Sn nucleus in 3d-metal antimonides are very sensitive to the filling of different crystallographic sites with metal atoms. The metal atoms in trigonal-bipyramidal sites have a strong effect on the quadrupole splitting of 119Sn. They are nearest to anions (Sb or Sn) with the typical axial ratio of c/a = 1.25. The QS(x) dependence of 119 Sn in 3d-metal antimonides in the 0 ≤ x ≤ 0.1 concentration range can be used to determine x – the concentration of transition metal excess relative to the stoichiometric composition. 相似文献
25.
We employ an agent‐based model to show that memory and the absence of an a priori best strategy are sufficient for self‐segregation and clustering to emerge in a complex adaptive system with discrete agents that do not compete over a limited resource nor contend in a winner‐take‐all scenario. An agent starts from a corner of a two‐dimensional lattice and aims to reach a randomly selected site in the opposite side within the shortest possible time. The agent is isolated during the course of its journey and does not interact with other agents. Time‐bound obstacles appear at random lattice locations and the agent must decide whether to challenge or evade any obstacle blocking its path. The agent is capable of adapting a strategy in dealing with an obstacle. We analyze the dependence of strategy‐retention time with strategy for both memory‐based and memory‐less agents. We derive the equality spectrum to establish the environmental conditions that favor the existence of an a priori best strategy. We found that memory‐less agents do not polarize into two opposite strategy‐retention time distributions nor cluster toward a center distribution. © 2004 Wiley Periodicals, Inc. Complexity 9: 41–46, 2004 相似文献
26.
27.
单壁碳纳米管的SERS研究 总被引:2,自引:2,他引:0
本文通过改进实验方法,将单壁碳纳米管的乙醇溶液与金胶混合并制作成固体薄膜,使单壁碳纳米管夹裹在金纳米粒子之间,保证了吸附的紧密性,获得了高质量的单壁碳纳米管SERS光谱。不但观测到文献中报道的径向呼吸振动模(RBM)和C-C正切拉伸模(GM)的增强,还在1100-1500cm-1区域观测到一组新峰,其峰形完整并有相当的强度。这些峰在现有的文献中几乎没有报导。文章对这组新峰的出现进行了初步的分析。 相似文献
28.
M. I. Gil' 《Proceedings of the American Mathematical Society》2003,131(12):3737-3746
A linear operator in a separable Hilbert space is called a quasinormal one if it is a sum of a normal operator and a compact one. In the paper, bounds for the spectrum of quasinormal operators are established. In addition, the lower estimate for the spectral radius is derived. Under some restrictions, that estimate improves the well-known results. Applications to integral operators and matrices are discussed. Our results are new even in the finite-dimensional case.
29.
30.