全文获取类型
收费全文 | 379562篇 |
免费 | 7379篇 |
国内免费 | 5261篇 |
专业分类
化学 | 190637篇 |
晶体学 | 5350篇 |
力学 | 19962篇 |
综合类 | 328篇 |
数学 | 56380篇 |
物理学 | 119545篇 |
出版年
2022年 | 2783篇 |
2021年 | 3565篇 |
2020年 | 3999篇 |
2019年 | 4438篇 |
2018年 | 12523篇 |
2017年 | 12943篇 |
2016年 | 10503篇 |
2015年 | 5154篇 |
2014年 | 6951篇 |
2013年 | 13592篇 |
2012年 | 14957篇 |
2011年 | 23430篇 |
2010年 | 15526篇 |
2009年 | 15593篇 |
2008年 | 20828篇 |
2007年 | 23634篇 |
2006年 | 11055篇 |
2005年 | 14995篇 |
2004年 | 11373篇 |
2003年 | 10854篇 |
2002年 | 9163篇 |
2001年 | 8231篇 |
2000年 | 6704篇 |
1999年 | 4948篇 |
1998年 | 4403篇 |
1997年 | 4193篇 |
1996年 | 4116篇 |
1995年 | 3388篇 |
1994年 | 3534篇 |
1993年 | 3501篇 |
1992年 | 3592篇 |
1991年 | 3700篇 |
1990年 | 3595篇 |
1989年 | 3524篇 |
1988年 | 3353篇 |
1987年 | 3288篇 |
1986年 | 3196篇 |
1985年 | 3896篇 |
1984年 | 4098篇 |
1983年 | 3357篇 |
1982年 | 3587篇 |
1981年 | 3379篇 |
1980年 | 3145篇 |
1979年 | 3472篇 |
1978年 | 3641篇 |
1977年 | 3568篇 |
1976年 | 3652篇 |
1975年 | 3432篇 |
1974年 | 3421篇 |
1973年 | 3605篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
211.
Xingxing Yu 《Journal of Graph Theory》2006,51(3):175-198
An infinite graph is 2‐indivisible if the deletion of any finite set of vertices from the graph results in exactly one infinite component. Let G be a 4‐connected, 2‐indivisible, infinite, plane graph. It is known that G contains a spanning 1‐way infinite path. In this paper, we prove a stronger result by showing that, for any vertex x and any edge e on a facial cycle of G, there is a spanning 1‐way infinite path in G from x and through e. Results will be used in two forthcoming papers to establish a conjecture of Nash‐Williams. © 2005 Wiley Periodicals, Inc. J Graph Theory 相似文献
212.
The steady motions of a vertical rotor balanced by two coupled perfectly rigid bodies (PRBs) are analyzed for stability. The rotor executes plane-parallel motions. The PRBs can rotate together about the rotor axis and about its transverse axes through equal angles but in opposite directions. It is established that when the mass of the PRBs is much less than that of the rotor and the rotor spins with a superresonant speed, only the basic steady motions, which are those of the best-balanced rotor, are asymptotically stable. 相似文献
213.
214.
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
215.
A. G. Artukh G. F. Gridnev M. Gruszecki F. Koscielniak A. G. Semchenkov O. V. Semchenkova Yu. M. Sereda J. Szmider Yu. G. Teterev 《Physics of Atomic Nuclei》2002,65(3):393-399
A systematic investigation of the forward-angle inclusive yields of 2≤Z≤11 isotopes produced in collisions of 18O projectile nuclei with a 9Be target in the Fermi energy region (35A MeV) is performed. The measurements were based on the use of the COMBAS double achromatic kinematical separator in the spectrometry mode at the Flerov Laboratory of Nuclear Reactions at the Joint Institute for Nuclear Research, FLNR (JINR, Dubna). The velocity, isotopic, and element distributions are presented. There is no unique mechanism that would explain the total set of results obtained in this experiment. A dominant role of low-energy reaction mechanisms is observed. The intensity of secondary beams of halolike nuclei 11Li, 12Be, and 14Be is determined. 相似文献
216.
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
217.
An analysis of events in the tunneling junction shows that the interaction of one-electron processes in a many-electron system may be a source of scale-invariant low-frequency fluctuations of conductivity (the interaction consists in that the quantum probability of an electron transition depends on fast random changes in the environment in the course of the transition, including the changes caused by analogous transitions). The theory relates flicker fluctuations in the tunneling conductivity to the discrete character of the spectrum of electron states and explains the nonlinearity of the noise-current characteristic observed in nanocomposites. 相似文献
218.
A method for stabilizing frequency based on using the soliton state of the Bose-Einstein condensate of alkali metal atoms as an atomic source was suggested. The critical total number of lithium condensate particles at which the existence of a quasi-one-dimensional soliton in the condensate was possible and the lifetime of such a soliton were estimated. The attainable accuracy of measuring reference transition frequencies in the suggested standard was shown to be substantially higher than with the known quantum frequency standards. 相似文献
219.
We consider Markov processes built from pasting together pieces of strong Markov processes which are killed at a position
dependent rate and connected via a transition kernel. We give necessary and sufficient conditions for local absolute continuity
of probability laws for such processes on a suitable path space and derive an explicit formula for the corresponding likelihood
ratio process. The main tool is the consideration of the process between successive jumps – what we call ‘elementary experiments’
– and criteria for absolute continuity of laws of the process there. We apply our results to systems of branching diffusions
with interactions and immigrations.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
220.
V. V. Kulagin 《Optics and Spectroscopy》2003,94(5):779-783
The generation of nonclassical states of light with specified frequency-dependent squeezing by way of introducing a correlation between the phase and amplitude of the input field is considered. Three schemes for measuring amplitude fluctuations of the input beam, based on a nondemolition measurement of the intensity in a nonlinear cubic crystal, the effect of light rectification in a quadratic optical crystal, and the use of a non-degenerate optical parametric oscillator, are proposed. The maximum possible value of noise suppression is estimated for each scheme. The prospects for practical realization of the proposed method for generation of frequency-dependent squeezed states are discussed. 相似文献