全文获取类型
收费全文 | 202511篇 |
免费 | 1967篇 |
国内免费 | 502篇 |
专业分类
化学 | 110728篇 |
晶体学 | 3652篇 |
力学 | 8000篇 |
综合类 | 11篇 |
数学 | 19204篇 |
物理学 | 63385篇 |
出版年
2020年 | 1730篇 |
2019年 | 1926篇 |
2018年 | 2242篇 |
2017年 | 2358篇 |
2016年 | 3526篇 |
2015年 | 2197篇 |
2014年 | 3554篇 |
2013年 | 9092篇 |
2012年 | 6512篇 |
2011年 | 8034篇 |
2010年 | 5703篇 |
2009年 | 5660篇 |
2008年 | 7171篇 |
2007年 | 7086篇 |
2006年 | 6711篇 |
2005年 | 6057篇 |
2004年 | 5523篇 |
2003年 | 5107篇 |
2002年 | 4877篇 |
2001年 | 6149篇 |
2000年 | 4626篇 |
1999年 | 3524篇 |
1998年 | 2749篇 |
1997年 | 2703篇 |
1996年 | 2595篇 |
1995年 | 2445篇 |
1994年 | 2333篇 |
1993年 | 2167篇 |
1992年 | 2828篇 |
1991年 | 2732篇 |
1990年 | 2672篇 |
1989年 | 2697篇 |
1988年 | 2718篇 |
1987年 | 2731篇 |
1986年 | 2594篇 |
1985年 | 3308篇 |
1984年 | 3319篇 |
1983年 | 2599篇 |
1982年 | 2709篇 |
1981年 | 2763篇 |
1980年 | 2533篇 |
1979年 | 2875篇 |
1978年 | 2860篇 |
1977年 | 2981篇 |
1976年 | 2816篇 |
1975年 | 2553篇 |
1974年 | 2510篇 |
1973年 | 2465篇 |
1972年 | 1702篇 |
1968年 | 1704篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
Franz H. Asthalter T. Dommach M. Ehnes A. Messel K. Sergueev I. 《Hyperfine Interactions》2002,141(1-4):131-134
The present status of the new nuclear resonance beamline PETRA 1 at HASYLAB, DESY, Hamburg is described. Besides an overview
of the experimental setup some examples of recent experiments are given. Those cover the main applications, i.e., inelastic
scattering from iron alloys and quasielastic scattering from glass-forming liquids.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
22.
M. Gorkunov M. Lapine E. Shamonina K.H. Ringhofer 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,28(3):263-269
Effective magnetic properties of a composite meta-material consisting of periodically arranged circular conductive elements
are studied theoretically. A general expression for the effective bulk permeability is obtained with mutual effects and lattice
ordering being taken into account. The resonance frequency of the permeability is found to be strongly dependent on the size
and shape of the unit cell. Frequency dispersion of the permeability is studied with special attention paid to the frequency
range, where negative values of the permeability are possible. Corresponding recommendations for optimisation of the meta-materials
with negative permeability are made. The results are confirmed by numerical simulations of the finite structure behaviour
in an external magnetic field.
Received 19 April 2002 Published online 31 July 2002 相似文献
23.
M. A. Augustyniak-Jabłokow K. Łukaszewicz A. Pietraszko V. E. Petrashen Yu. V. Yablokov 《Physics of the Solid State》2002,44(8):1480-1483
The EPR spectra evolution of Cs2Zn1?x Cux(ZrF6)2 · 6H2O (x=0.01, 0.6, 0.8, and 1.0) in the temperature range 4.2–330 K and the x-ray structure analysis of the compound with x=1.0 in the range 150–327 K show that the Jahn-Teller (JT) complex Cu(H2O)6 coordination sphere undergoes a plastic deformation. The observed effect is due to the combined influence of small lattice strains existing in the paraphase and a new one appearing as a result of a ferroelastic phase transition and increasing with decreasing temperature below T c . It is proved that both cooperative interactions between JT complexes and ferroelastic strain stabilize a certain JT configuration. The problem of instability of a JT configuration compressed at T ~ 265 K is discussed. 相似文献
24.
25.
In the present paper, we find a class of linear homogeneous differential equations of order n + 1 (n > 1) whose fundamental system of solutions is constructed from the fundamental system of solutions of a second-order differential
equation. The spectral properties of differential operators generated by these differential expressions are investigated.
In particular, sufficient conditions are obtained for the coefficients of a second-order differential equation under which
the case of maximal deficiency indices is realized.
Dedicated to the memory of B. M. Levitan 相似文献
26.
S. Meenakshi B.K. Godwal I. Orgzall S. Tkachev 《Journal of Physics and Chemistry of Solids》2006,67(8):1660-1667
We report the results of an X-ray diffraction study of CdAl2Se4 and of Raman studies of HgAl2Se4 and ZnAl2Se4 at room temperature, and of CdAl2S4 and CdAl2Se4 at 80 K at high pressure. The ambient pressure phase of CdAl2Se4 is stable up to a pressure of 9.1 GPa above which a phase transition to a disordered rock salt phase is observed. A fit of the volume pressure data to a Birch-Murnaghan type equation of state yields a bulk modulus of 52.1 GPa. The relative volume change at the phase transition at ∼9 GPa is about 10%. The analysis of the Raman data of HgAl2Se4 and ZnAl2Se4 reveals a general trend observed for different defect chalcopyrite materials. The line widths of the Raman peaks change at intermediate pressures between 4 and 6 GPa as an indication of the pressure induced two stage order-disorder transition observed in these materials. In addition, we include results of a low temperature Raman study of CdAl2S4 and CdAl2Se4, which shows a very weak temperature dependence of the Raman-active phonon modes. 相似文献
27.
Benjamin J. K. Evans Susan M. Scott Antony C. Searle 《General Relativity and Gravitation》2002,34(10):1675-1684
We have developed a new tool for numerical work in General Relativity: GRworkbench. We discuss how GRworkbench's implementation of a numerically-amenable analogue to Differential Geometry facilitates the development of robust and chart-independent numerical algorithms. We consider, as an example, geodesic tracing on two charts covering the exterior Schwarzschild space-time. 相似文献
28.
K. C. Shin 《Communications in Mathematical Physics》2002,229(3):543-564
We study the eigenvalue problem with the boundary conditions that decays to zero as z tends to infinity along the rays , where is a real polynomial and . We prove that if for some we have for all , then the eigenvalues are all positive real. We then sharpen this to a larger class of polynomial potentials.
In particular, this implies that the eigenvalues are all positive real for the potentials when with , and with the boundary conditions that decays to zero as z tends to infinity along the positive and negative real axes. This verifies a conjecture of Bessis and Zinn-Justin.
Received: 16 January 2002 / Accepted: 1 May 2002 Published online: 6 August 2002 相似文献
29.
K. Batra V. Prasad M. Mohan 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,20(2):191-198
The scattering of heavy ion with a multilevel Rydberg atom in the presence of an electromagnetic field is studied. The interaction
of Rydberg atom and the e.m field is explored using non-perturbative quasi-energy technique. Although the results are presented
for selected excitations but in actual calculations we have included many levels of the atom. The effect of various parameters
are shown on collisional excitation process. As an illustration detailed calculations are performed for the inelastic proton-Na
Rydberg atom collision accompanied by the transfer of photons and the effects of dressing due to the field are considered.
The emphasis of the present work is on collision induced transitions especially the case that involves change of orbital as
well as principal quantum number.
Received 26 December 2001 / Received in final form 8 April 2002 Published online 19 July 2002 相似文献
30.
V. K. Malyutenko A. I. Liptuga V. A. Botte V. I. Chernyakhovskii 《Journal of Applied Spectroscopy》1991,55(4):1024-1028
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 55, No. 4, pp. 624–629, October, 1991. 相似文献