全文获取类型
收费全文 | 9451篇 |
免费 | 1797篇 |
国内免费 | 1030篇 |
专业分类
化学 | 6697篇 |
晶体学 | 85篇 |
力学 | 562篇 |
综合类 | 52篇 |
数学 | 1086篇 |
物理学 | 3796篇 |
出版年
2024年 | 30篇 |
2023年 | 224篇 |
2022年 | 228篇 |
2021年 | 365篇 |
2020年 | 395篇 |
2019年 | 371篇 |
2018年 | 359篇 |
2017年 | 293篇 |
2016年 | 512篇 |
2015年 | 436篇 |
2014年 | 558篇 |
2013年 | 750篇 |
2012年 | 923篇 |
2011年 | 898篇 |
2010年 | 617篇 |
2009年 | 604篇 |
2008年 | 621篇 |
2007年 | 531篇 |
2006年 | 497篇 |
2005年 | 403篇 |
2004年 | 310篇 |
2003年 | 232篇 |
2002年 | 198篇 |
2001年 | 172篇 |
2000年 | 202篇 |
1999年 | 219篇 |
1998年 | 171篇 |
1997年 | 161篇 |
1996年 | 183篇 |
1995年 | 143篇 |
1994年 | 119篇 |
1993年 | 91篇 |
1992年 | 99篇 |
1991年 | 56篇 |
1990年 | 73篇 |
1989年 | 54篇 |
1988年 | 26篇 |
1987年 | 28篇 |
1986年 | 37篇 |
1985年 | 38篇 |
1984年 | 13篇 |
1983年 | 16篇 |
1982年 | 6篇 |
1981年 | 4篇 |
1980年 | 6篇 |
1979年 | 2篇 |
1977年 | 1篇 |
1976年 | 2篇 |
1957年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 156 毫秒
31.
Study on the in—plane electrical resistivity and thermoelectric power in single crystals of La2—xBaxCuO4 下载免费PDF全文
The in-plane electrical resistivity and thermoelectric power have been measured on single crystals of La2-xBaxCuO4 at around x=0.125. The room temperature resistivity and thermopower have their maximum values at x=0.125, indicating that the carrier concentration is the minimum and the carriers are most strongly localized at x=0.125. The observed semiconductor-like behaviour can be well described by the weak-localized quasi-two-dimensional state. The steep rise in electric resistivity of the sample at x=0.125 below 70K is attributed to the formation of static stripe-order of holes and spins, which are pinned by the low-temperature tetragonal (LTT) structure, as discovered in La1.48Nd0.4Sr0.12CuO4. The temperature dependence of electric resistivity below 70K is still well described by the formula ρ∝ lnT. A definite change in the slope of thermopower is observed at the low-temperature orthorhombic-LTT structural phase transition temperature. The origin of the 1/8 anomaly is discussed in the text. 相似文献
32.
The classical perturbation theory is extended to the weighted Kronecker product linear systems W(A? B)Wx =h. Upper bounds are derived for the normwise condition number. 相似文献
33.
A novel type of corner reflector for the reflection of surface plasmon polariton (SPP) is proposed. The reflector consists
of two layers of compensatory media whose permittivity and permeability take opposite signs to that of the corresponding layer
of the SP waveguide. By rigorously solving Maxwell's equations, the reflected SPP is proved to exist. The transverse wave
vector of the reflected SPP is always antiparallel to that of the incident SPP and no phase retardation is introduced. 相似文献
34.
The behavior of a two-level entangled atom in an optical field with circular polarization is studied in this paper. The interaction of an optical field and one of the entangled atoms is analyzed in detail. A general solution of the SchrAo¨Gdinger equation about the motion of the entangled atom is obtained. The properties of the action are dependent on the initial state of the atom. By detecting the entangled atom out of the field, we can obtain the state of the other atom moving in the field. It is shown that the state of the atom out of the field will influence the energies of the split-levels of the atom in the field. 相似文献
35.
Wei-Yan Shao Ying-Nan Cao Wen-Jie Pan Xian-Zhang Bu Lin-Kun An Lian-Quan Gu Albert S.C. Chan 《Tetrahedron letters》2006,47(24):4085-4089
Seventeen unsymmetrical curcumin derivatives were synthesized in good yield and purity by a facile solid phase synthesis strategy. 相似文献
36.
In the present paper, a Lotka–Volterra type mutualism system with several delays is studied. Some new and interesting sufficient conditions are obtained for the global existence of positive periodic solutions of the mutualism system. Our method is based on Mawhin’s coincidence degree and novel estimation techniques for the a priori bounds of unknown solutions. Our results are different from the existing ones such as those in of Yang et al. [F. Yang, D. Jiang, A. Ying, Existence of positive solution of multidelays facultative mutualism system, J. Eng. Math. 3 (2002) 64–68] and Chen et al. [F. Chen, J. Shi, X. Chen, Periodicity in a Lotka–Volterra facultative mutualism system with several delays, J. Eng. Math. 21 (3) (2004) 403–409]. 相似文献
37.
Cao H. P. Chen G. Grechkoseeva M. A. Mazurov V. D. Shi W. J. Vasil'ev A. V. 《Siberian Mathematical Journal》2004,45(6):1031-1035
The spectrum of a finite group is the set of its element orders. A finite group G is said to be recognizable by spectrum, if every finite group with the same spectrum as G is isomorphic to G. The purpose of the paper is to prove that for every natural m the finite simple Chevalley group F
4(2
m
) is recognizable by spectrum. 相似文献
38.
Shui Cao ZHENG Huo Nan LIN Di He HU 《数学学报(英文版)》2005,21(5):1137-1148
In this paper, we investigate the Hausdorff measure for level sets of N-parameter Rd-valued stable processes, and develop a means of seeking the exact Hausdorff measure function for level sets of N-parameter Rd-valued stable processes. We show that the exact Hausdorff measure function of level sets of N-parameter Rd-valued symmetric stable processes of index α is Ф(r) = r^N-d/α (log log l/r)d/α when Nα 〉 d. In addition, we obtain a sharp lower bound for the Hausdorff measure of level sets of general (N, d, α) strictly stable processes. 相似文献
39.
40.
By introducing an imaginary space transform curvature ρs, a complex space called Riemannian space is constructed, in which the light propagating in free space has the trajectory
of straight line while propagating. Moreover, this curvature couples with that of the wave front of the paraxial beam ρw, and therefore a complex curvature ρc is constructed, which can be employed to investigate the behavior of the light transmission and to generalize the ABCD law.
Project supported by the National Hi-Tech Inertial Confinement Fusion Committee, the Guangdong Natural Science Foundation
the Postdoctoral Foundation of Guangdong and National Postdoctoral Foundation of China. 相似文献