全文获取类型
收费全文 | 475202篇 |
免费 | 4085篇 |
国内免费 | 1929篇 |
专业分类
化学 | 241674篇 |
晶体学 | 6805篇 |
力学 | 22263篇 |
综合类 | 67篇 |
数学 | 66980篇 |
物理学 | 143427篇 |
出版年
2020年 | 3407篇 |
2019年 | 3776篇 |
2018年 | 11862篇 |
2017年 | 12513篇 |
2016年 | 10437篇 |
2015年 | 5059篇 |
2014年 | 6867篇 |
2013年 | 16852篇 |
2012年 | 16719篇 |
2011年 | 26012篇 |
2010年 | 17084篇 |
2009年 | 16970篇 |
2008年 | 23670篇 |
2007年 | 26633篇 |
2006年 | 14735篇 |
2005年 | 18293篇 |
2004年 | 14500篇 |
2003年 | 13424篇 |
2002年 | 11578篇 |
2001年 | 11438篇 |
2000年 | 9096篇 |
1999年 | 6537篇 |
1998年 | 5526篇 |
1997年 | 5532篇 |
1996年 | 5492篇 |
1995年 | 4654篇 |
1994年 | 4780篇 |
1993年 | 4656篇 |
1992年 | 5040篇 |
1991年 | 5128篇 |
1990年 | 4875篇 |
1989年 | 4799篇 |
1988年 | 4667篇 |
1987年 | 4602篇 |
1986年 | 4547篇 |
1985年 | 5909篇 |
1984年 | 6129篇 |
1983年 | 5020篇 |
1982年 | 5457篇 |
1981年 | 5177篇 |
1980年 | 4796篇 |
1979年 | 5180篇 |
1978年 | 5457篇 |
1977年 | 5424篇 |
1976年 | 5469篇 |
1975年 | 5066篇 |
1974年 | 5198篇 |
1973年 | 5379篇 |
1972年 | 3931篇 |
1967年 | 3258篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
121.
An implicit quasi-monotone second-order accurate method is proposed for analyzing the spiral Couette flow of a rarefied gas between coaxial cylinders. The basic advantages of the method over the conventional method of stationry iterations are that the former is conservative with respect to the collision integral, has a simple software implementation for any types of boundary conditions, and applies to a wide range of Knudsen numbers. 相似文献
122.
A Modified Quasi-Newton Method for Structured Optimization with Partial Information on the Hessian 总被引:2,自引:0,他引:2
This paper develops a modified quasi-Newton method for structured unconstrained optimization with partial information on the
Hessian, based on a better approximation to the Hessian in current search direction. The new approximation is decided by both
function values and gradients at the last two iterations unlike the original one which only uses the gradients at the last
two iterations. The modified method owns local and superlinear convergence. Numerical experiments show that the proposed method
is encouraging comparing with the methods proposed in [4] for structured unconstrained optimization
Presented at the 6th International Conference on Optimization: Techniques and Applications, Ballarat, Australia, December
9–11, 2004 相似文献
123.
We investigate the conjecture that every circulant graph X admits a k‐isofactorization for every k dividing |E(X)|. We obtain partial results with an emphasis on small values of k. © 2006 Wiley Periodicals, Inc. J Combin Designs 14: 406–414, 2006 相似文献
124.
The purpose of this paper is to investigate problems of the Navier-Stokes approximation to kinetic equations in terms of the
so-called Chapman-Enskog projection. One considers properties of the Chapman-Enskog projection for the Cauchy problem for
moment approximations of the kinetic equation and primarily the Chapman-Enskog projection for the Boltzmann-Peierls kinetic
equation. The existence of the Chapman-Enskog projection for the Cauchy problem is proved for the phase space of conservative
variables (phenomena of nonlinear diffusion) and for the phase space of physical variables (the second sound projection).
__________
Translated from Trudy Seminara imeni I. G. Petrovskogo, No. 25, pp. 184–225, 2005. 相似文献
125.
C Falugi A Diaspro C Angelini M L Pedrotti M Raimondo M Robello 《Micron (Oxford, England : 1993)》2002,33(3):233-239
Confocal laser scanning microscopy (CLSM) was used to examine molecules related to the cholinergic neurotransmission system and detected at all the larval stages of Paracentrotus lividus, by histochemical and immunohistochemical methods. CLSM, providing spatial resolution of the cells located both at the larval surface and at depth, allows a complete mapping in a three-dimensional volumetric frame. At early larval stages acetylcholinesterase- as well as choline acetyltransferase-like molecules were found mainly in the gut wall cells, and along the ciliary bands of the arms, together with muscarinic acetylcholine receptors. At perimetamorphic stages, cholinergic molecules were present in the ciliate strands along the arms, in the larval body and in the rudiment. At metamorphosis, positivity to cholinergic molecules translocated to the juvenile, where a high frequency of mAChR- and ChAT-like positive cells was found. 相似文献
126.
127.
J. Gasser M.A. Ivanov E. Lipartia M. Mojzis A. Rusetsky 《The European Physical Journal C - Particles and Fields》2002,26(1):13-34
We investigate the ground-state energy of the atom (pionic hydrogen) in the framework of QCD + QED. In particular, we evaluate the strong energy-level shift. We perform
the calculation at next-to-leading order in the low-energy expansion in the framework of the relevant effective field theory.
The result provides a relation between the strong energy shift and the pion-nucleon S-wave scattering lengths - evaluated in pure QCD - at next-to-leading order in isospin-breaking and in the low-energy expansion.
We compare our result with available model calculations.
Received: 11 June 2002 / Published online: 9 October 2002 相似文献
128.
V. I. Vettegren V. A. Marikhin V. B. Kulik L. S. Titenkov 《Physics of the Solid State》2002,44(12):2341-2346
The temperature dependence of the expansion ?C of trans conformers of the carbon skeleton of macromolecules in crystallized and amorphous poly(ethylene terephthalate) (PET) due to zero-point and thermal atomic vibrations is investigated by IR spectroscopy. It is found that the thermal expansion coefficient βC jumpwise increases at the characteristic temperatures T t and T b. This increase is associated with the crossover from the quantum to classical statistics of torsional and bending vibration modes. The quantum and classical contributions to the expansion ?C are determined for each mode. The quantum and classical contributions of the torsional vibrational mode in the amorphous polymer are approximately 1.5 times larger than those in the crystallized polymer. This effect is caused by an increase in the anharmonicity of torsional vibrations in the amorphous polymer. 相似文献
129.
O. Kortner M.P. Locher V.E. Markushin P. Weber O. Wigger 《The European Physical Journal C - Particles and Fields》2002,25(3):353-360
We study correlations in the exclusive reaction at rest with complete reconstruction of the kinematics for each event. The inclusive distribution is fairly flat at small
invariant mass of the pion pair while a small enhancement in the double differential distribution is observed for small invariant
masses of both pion pairs. Dynamical models with resonances in the final state are shown to be consistent with the data while
the stochastic HBT mechanism is not supported by the present findings.
Received: 26 February 2002 / Revised version: 22 July 2002 / Published online: 30 August 2002 相似文献
130.
Z. V. Golubenko A. S. Kamzin L. P. Ol’khovik M. M. Khvorov Z. I. Sizova V. P. Shabatin 《Physics of the Solid State》2002,44(9):1698-1702
Magnetization and remagnetization processes in a close-packed nanodispersed barium hexaferrite powder sample in the magnetically stable state were analyzed. Reversibility effects were discussed in terms of interparticle interaction. Judging from the magnetization curve and the parameters characterizing remagnetization irreversibility, the sample under study is a model system of small Stoner-Wohlfarth particles. 相似文献