全文获取类型
收费全文 | 2637篇 |
免费 | 74篇 |
国内免费 | 7篇 |
专业分类
化学 | 1665篇 |
晶体学 | 29篇 |
力学 | 80篇 |
数学 | 278篇 |
物理学 | 666篇 |
出版年
2021年 | 16篇 |
2020年 | 25篇 |
2019年 | 25篇 |
2018年 | 19篇 |
2016年 | 39篇 |
2015年 | 51篇 |
2014年 | 40篇 |
2013年 | 94篇 |
2012年 | 128篇 |
2011年 | 160篇 |
2010年 | 78篇 |
2009年 | 53篇 |
2008年 | 132篇 |
2007年 | 130篇 |
2006年 | 137篇 |
2005年 | 132篇 |
2004年 | 88篇 |
2003年 | 91篇 |
2002年 | 90篇 |
2001年 | 62篇 |
2000年 | 55篇 |
1999年 | 44篇 |
1998年 | 34篇 |
1997年 | 30篇 |
1996年 | 43篇 |
1995年 | 27篇 |
1994年 | 31篇 |
1993年 | 38篇 |
1992年 | 33篇 |
1991年 | 32篇 |
1990年 | 21篇 |
1989年 | 30篇 |
1988年 | 29篇 |
1987年 | 32篇 |
1986年 | 37篇 |
1985年 | 45篇 |
1984年 | 46篇 |
1983年 | 28篇 |
1982年 | 34篇 |
1981年 | 31篇 |
1980年 | 28篇 |
1979年 | 34篇 |
1978年 | 34篇 |
1977年 | 30篇 |
1976年 | 29篇 |
1975年 | 31篇 |
1974年 | 30篇 |
1973年 | 24篇 |
1971年 | 20篇 |
1967年 | 17篇 |
排序方式: 共有2718条查询结果,搜索用时 15 毫秒
31.
We consider an Ising model with Kac potential dK(¦x¦) which may have arbitrary sign, and show, following Gates and Penrose, that the free energy in the classical limit0+ can be obtained from a variational principle. When the Fourier transform of the potential has its maximum atp=0 one recovers the usual mean-field theory of magnetism. When the maximum occurs forp
00, however, one obtains an oscillatory or helicoidal phase in which the magnetization near the critical point oscillates with period 2/¦p
0¦. An example with a potential possessing parameter-dependent oscillations is shown to exhibit crossover phenomena and a multicritical Lifshitz point in the classical limit. 相似文献
32.
33.
34.
35.
36.
N. Angelescu M. Bundaru G. Costache C. J. Thompson 《Journal of statistical physics》1986,43(1-2):33-49
A generalizedO(n) matrix version of the classical Heisenberg model, introduced by Fuller and Lenard as a classical limit of a quantum model, is solved exactly in one dimension. The free energy is analytic and the pair correlation functions decay exponentially for all finite temperatures. It is shown, however, that even for a finite number of spins the model has a phase transition in then limit. The transition features a specific heat jump, zero long-range order at all temperatures, and zero correlation length at the critical point. The Curie-Weiss version of the model is also solved exactly and shown to have standard mean-field type behavior for all finiten and to differ from the one-dimensional results in then limit. 相似文献
37.
Svilen Bobev Paul H. Tobash Joe D. Thompson John L. Sarrao 《Journal of solid state chemistry》2005,178(6):2091-2103
A number of rare-earth alumo-silicides (R-Al-Si) have been synthesized from the corresponding elements by high-temperature reactions, carried out in excess of aluminum to serve as a flux. Under these experimental conditions, large single crystals of all R-Al-Si ternary phases were readily produced. The crystal structures these ternaries adopt were studied by means of powder and single-crystal X-ray diffraction and were classified as follows: (1) the early rare-earths (R=La, Ce, Pr, Nd, Sm, Gd) yield RAlxSi2−x, x∼1, non-stoichiometric ternary derivatives of the body-centered α-ThSi2-type; (2) the late rare-earths (R=Tb, Dy, Ho, Er, Tm) form stoichiometric R2Al3Si2 compounds that crystallize in the C-centered monoclinic Y2Al3Si2-type; (3) the divalent Eu and Yb produce EuAl2Si2 and YbAl2Si2 with the trigonal CaAl2Si2-type, whereas the last lanthanide element, Lu, forms LuAlSi with C-centered orthorhombic YAlGe-type. These structural trends are reviewed, and the evolution of the basic physical properties such as magnetism, heat capacity and electrical resistivity when moving across the series is described in detail. 相似文献
38.
Illumination of a p-type semiconductor—NH3 interface (or heterojunction) with photons of energy greater than the semiconductor band gap causes electrons to be injected into the NH3. There is no hole injection at a n-type electrode. Suggestions are made for the required energy levels in the liquid. 相似文献
39.
Razak J. Al-Essa Richard J. Puddephatt Charles F.H. Tipper Peter J. Thompson 《Journal of organometallic chemistry》1978,157(2):C40-C42
The platinacyclobutane complexes PtCl2L2(C3H5Me)], L pyridine, CD3CN, or tetrahydrofuran, exist as mixtures of isomers containing PH2 or P groups in rapid equilibrium. Decomposition occurs in some cases to give [PtCl2L(CH3CH2CHCH2)]. Stereospecific skeletal isomerisation also occurs in metallocyclobutanes containing the groups PH2 PHR, when R aryl further decomposition gives ν-allylplatinum complexes. 相似文献
40.
Several research groups have reported the presence of nanometer-sized particles (nanoslabs) in clear solutions, which precipitate the crystalline MFI (ZSM-5) structure. Debate about the growth mechanism for Al-free ZSM-5 (silicalite-1) has revolved around growth by small silicate units (monomers, dimers, etc.) from solution vs growth by nanoslab addition. A model developed for precipitation of uniform sized colloids by addition of sub-colloidal precursor units has been adapted for this zeolite synthesis system. Parameter values were adjusted for the simulation results to match experimental observations from work reported previously, at least to the extent possible. The model involved the simultaneous solution of up to 6000 ordinary differential equations, and required computation times of up to 24 h. The results shed light on the crystal growth mechanism, but pose questions for further investigations of the nucleation mechanism. 相似文献