全文获取类型
收费全文 | 14328篇 |
免费 | 2723篇 |
国内免费 | 2490篇 |
专业分类
化学 | 11489篇 |
晶体学 | 241篇 |
力学 | 862篇 |
综合类 | 202篇 |
数学 | 1830篇 |
物理学 | 4917篇 |
出版年
2024年 | 33篇 |
2023年 | 241篇 |
2022年 | 383篇 |
2021年 | 498篇 |
2020年 | 582篇 |
2019年 | 637篇 |
2018年 | 547篇 |
2017年 | 512篇 |
2016年 | 737篇 |
2015年 | 863篇 |
2014年 | 936篇 |
2013年 | 1153篇 |
2012年 | 1300篇 |
2011年 | 1318篇 |
2010年 | 1060篇 |
2009年 | 1022篇 |
2008年 | 1029篇 |
2007年 | 860篇 |
2006年 | 769篇 |
2005年 | 692篇 |
2004年 | 604篇 |
2003年 | 525篇 |
2002年 | 642篇 |
2001年 | 520篇 |
2000年 | 370篇 |
1999年 | 282篇 |
1998年 | 219篇 |
1997年 | 161篇 |
1996年 | 151篇 |
1995年 | 146篇 |
1994年 | 107篇 |
1993年 | 98篇 |
1992年 | 83篇 |
1991年 | 68篇 |
1990年 | 60篇 |
1989年 | 45篇 |
1988年 | 36篇 |
1987年 | 31篇 |
1986年 | 20篇 |
1985年 | 17篇 |
1984年 | 23篇 |
1983年 | 16篇 |
1982年 | 11篇 |
1981年 | 15篇 |
1979年 | 11篇 |
1978年 | 8篇 |
1975年 | 11篇 |
1974年 | 14篇 |
1972年 | 12篇 |
1971年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 625 毫秒
991.
In this Letter, we study the scattering dynamics of a pair of solitary waves in the Fermi-Pasta-Ulam model with interaction potential V(x)=alphax(2)/2+x(4)/4 and establish a quantitative connection between the scattering property and the energy transport behavior. The energy and momentum conservation laws are obtained and the scattering rates of solitary waves are calculated. Our studies suggest that the anharmonic limit model with alpha=0 can be taken as a paradigm model for studying lattice solitary waves. 相似文献
992.
The decay rate gamma of an excited dipole molecule inside a waveguide is evaluated for the strongly coupled matter-field case near a cutoff frequency omegac without using perturbation analysis. Because of the singularity in the density of photon states at the cutoff frequency, we find that gamma depends nonanalytically on the coupling constant g as g4/3, which leads to a vast increase in the decay rate. 相似文献
993.
We report the first atomistic determination of the minimum energy path for a series of bond ruptures to advance a crack front. Saddle-point configurations on (111) cleavage planes in Si reveal a steplike distribution of atomic displacements, implying a kink mechanism which is known to control dislocation mobility. Manifestations of lattice trapping and directional cleavage anisotropy are further elucidated. 相似文献
994.
Filamentous viruses such as fd and M13 are highly charged rodlike polyelectrolytes. In this study, we employ fd virus to test the recent prediction of charge inversion [Nguyen, Rouzina, and Shklovskii, J. Chem. Phys. 112, 2562 (2000)]. Light scattering measurements show bundle formation and resolubilization of fd viruses when MgCl(2) was added from 0 to 600 mM. The effective charge of fd was studied by measuring their electrophoretic mobility using a filament tracking method uniquely suited for the system. Monte Carlo simulations were performed under canonical ensemble to predict the charge distribution around the rodlike virus. Charge inversion, which has been suggested theoretically to accompany with bundle resolubilization, was not observed in either experiments or simulations. A modified analysis of force balance is called upon to account for these new findings. 相似文献
995.
L.?Zhao X.?Wang B.?Wang W.?Wen T.-Y.?ZhangEmail author 《Applied physics. B, Lasers and optics》2004,78(6):769-774
Energy Dispersive X-ray Fluorescence Spectroscopy, X-ray diffraction and density measurements were conducted on undoped and ZnO-doped congruent LiNbO3 single crystals grown by the Czochralski method. Based on the experimental results, an intrinsic defect evolution model was proposed. When ZnO was doped into the congruent LN crystals, the Zn ions replaced first the Li ions and increased the density. Then, the Zn ions simultaneously replaced the Li ions and the antisite NbLis until all NbLi ions were replaced, which increased the density further. After that, the Zn ions substituted Nb ions in the Nb-sublattice sites with the reduction of the Li vacancies as self-compensation and thus reduced the density. When the Li vacancies disappeared completely, the Zn ions substituted simultaneously both Li ions in the Li-sublattice sites and Nb ions in the Nb-sublattice sites. The simultaneous substitution might finally lead to the generation of oxygen vacancies and decreased the density further. PACS 61.72.-y; 06.30.Dr; 61.10.-i 相似文献
996.
We present a detailed study of the transport and the efficiency of a ratchet system in a periodic potential in the presence of correlated noises. The current and the efficiency of the system are investigated. It is found that, when the potential is spatially symmetric, the correlation between the two noises can induce a net transport. The efficiency shows many interesting features as a function of the applied force, the noise intensity, the external load, etc. The efficiency can be maximized as a function of noise intensity (or temperature), which shows that the thermal fluctuation can facilitate the efficiency of energy transformation. 相似文献
997.
De-hua?Wen Wei?Chen Xian-ju?Wang Bao-quan?Ai Guo-tao?Liu Dong-qiao?Dong Liang-gang?LiuEmail author 《The European Physical Journal A - Hadrons and Nuclei》2004,21(2):349-354
The influence of rotation on the total masses and radii of neutron stars is calculated by Hartles slow-rotation formalism, while the equation of state is considered in a relativistic
-
model. As the changes of the mass and radius of a real neutron star caused by rotation are very small in comparison with the total mass and radius, one can see that Hartles approximate method is rational to deal with the rotating neutron stars. If three property values, mass, radius and period, are observed for the same neutron star, then the EOS of this neutron star could be decided entirely.Received: 7 November 2003, Revised: 17 February 2004, Published online: 31 August 2004PACS:
04.40.Dg Relativistic stars: structure, stability, and oscillations - 95.30.Sf Relativity and gravitation - 97.10.Kc Stellar rotation - 97.60.Jd Neutron stars 相似文献
998.
Bao-Quan?Ai Xian-Ju?Wang Guo-Tao?Liu Hui-Zhang?Xie De-Hua?Wen Wei?Chen Liang-Gang?LiuEmail author 《The European Physical Journal B - Condensed Matter and Complex Systems》2004,37(4):523-526
We present a study of the transport of a Brownian particle moving in a periodic symmetric potential in the presence of asymmetric unbiased fluctuations. The particle is considered to move in a medium with periodic space dependent friction. By tuning the parameters of the system, the direction of the current exhibits reversals, both as a function of temperature as well as the amplitude of rocking force. We found that the mutual interplay between the opposite driving factors is the necessary term for current reversals.Received: 11 October 2003, Published online: 9 April 2004PACS:
05.40.-a Fluctuation phenomena, random processes, noise, and Brownian motion - 02.50.Ey Stochastic processes - 87.10. + e General theory and mathematical aspects 相似文献
999.
An amperometric nitrite sensor based on a polymeric nikel tetraaminothphalocyanine (p-NiTAPc) film coated glassy carbon (GC) electrode was developed. The mechanism of catalysis on the surface of the electrode was discussed. The sensor exhibited fast respond towards nitrite with a detection limit of 1×10−7 M and a linear concentration range of 5×10−7 to 8×10−3 M. The possible interference from several common ions was tested. The proposed method was successfully applied in the detection of nitrite in real samples. 相似文献
1000.
The potential energy surfaces have been constructed for the 1A', 3A', and 3A" states of HBO by using the multireference perturbation theory with the basis set cc-pVTZ (6d,10f). Two stationary points and a transition state have been characterized on all the three surfaces, which are in good agreement with available experiments and previous calculations. The interconversion pathways from metastable boron hydroxide BOH to the considerably more stable HBO are expounded based on the nature of the surfaces. 相似文献