全文获取类型
收费全文 | 458216篇 |
免费 | 3786篇 |
国内免费 | 1396篇 |
专业分类
化学 | 216473篇 |
晶体学 | 6887篇 |
力学 | 24533篇 |
综合类 | 8篇 |
数学 | 75607篇 |
物理学 | 139890篇 |
出版年
2021年 | 3673篇 |
2020年 | 3907篇 |
2019年 | 4448篇 |
2018年 | 16020篇 |
2017年 | 16086篇 |
2016年 | 14383篇 |
2015年 | 5623篇 |
2014年 | 8426篇 |
2013年 | 18453篇 |
2012年 | 17789篇 |
2011年 | 26785篇 |
2010年 | 18016篇 |
2009年 | 18459篇 |
2008年 | 21465篇 |
2007年 | 23344篇 |
2006年 | 14242篇 |
2005年 | 13408篇 |
2004年 | 12797篇 |
2003年 | 12002篇 |
2002年 | 11130篇 |
2001年 | 12161篇 |
2000年 | 9093篇 |
1999年 | 7031篇 |
1998年 | 5960篇 |
1997年 | 5707篇 |
1996年 | 5330篇 |
1995年 | 4598篇 |
1994年 | 4512篇 |
1993年 | 4422篇 |
1992年 | 4787篇 |
1991年 | 5065篇 |
1990年 | 4783篇 |
1989年 | 4727篇 |
1988年 | 4429篇 |
1987年 | 4518篇 |
1986年 | 4282篇 |
1985年 | 5302篇 |
1984年 | 5464篇 |
1983年 | 4537篇 |
1982年 | 4673篇 |
1981年 | 4307篇 |
1980年 | 4227篇 |
1979年 | 4509篇 |
1978年 | 4646篇 |
1977年 | 4633篇 |
1976年 | 4492篇 |
1975年 | 4290篇 |
1974年 | 4246篇 |
1973年 | 4262篇 |
1972年 | 3068篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
81.
S. G. Kadmensky 《Physics of Atomic Nuclei》2002,65(8):1390-1402
The angular distributions of fragments originating from the binary decay of oriented spherical and deformed nuclei are investigated with allowance for correct transformation properties of wave functions under time inversion. It is shown that, as in the case of protonic decay, the adiabatic approximation for collective rotational degrees of freedom of the systems under investigation is inapplicable in describing the angular distributions of fragments of the deep-subbarrier alpha and cluster decays of nuclei. It is demonstrated that this approximation is justified in describing spontaneous and induced low-energy nuclear fission. The dependence of partial fission widths on the orientation of intrinsic axes, spins, and projections of spins and relative orbital angular momenta of fission fragments is analyzed by using the formalism of the unified theory of nuclear reactions and the theory of open Fermi systems. It is shown that the adiabatic approximation leads to the coherent interference between the wave functions for the relative motion of fragments, whereby the universal angular distributions of fission fragments of oriented nuclei is formed. Deviations from the A. Bohr formula are investigated for these distributions. 相似文献
82.
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
83.
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
84.
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
85.
86.
S. V. Prants 《JETP Letters》2002,75(12):651-658
A semiclassical study is carried out of the nonlinear interaction dynamics between two-level atoms and a standing-wave field in a high-finesse cavity. As a result of atomic movement or wave amplitude modulation, a dynamic local instability occurs in a strongly coupled atom-field system. The appearance of dynamical Hamiltonian chaos, fractals, and Lévy flights is demonstrated for the models of two experimental devices: a (micro)maser with thermal Rydberg atoms and a microlaser with cold atoms. Numerical simulation showed that the manifestations of classical chaos, atomic fractals, and flights can be observed in the appropriate real experiments. Attention is drawn to the prospects provided by work on the atom-field systems in the coupling-modulated high-finesse cavities for further investigation of the quantum-classical correspondence, quantum chaos, and decoherence. 相似文献
87.
It is explicitly shown that if phase transition occurs at the core of a newborn neutron star with moderately strong magnetic
field strength, which populates only the electron’s Landau levels, then in the β -equilibrium condition, the quark core is
energetically much more unstable than the neutron matter of identical physical condition. 相似文献
88.
X-ray diffraction patterns of nanocrystalline Fe-Cu-Nb-Si-B (FINEMET) alloys reveal that bcc α-Fe/α-FeSi crystallites with
the average grain size of 20(5) nm are dispersed in amorphous matrix. Enhanced electron—electron interaction (EEI) and quantum
interference (QI) effects as well as electron-magnon (and/or electron-spin fluctuation) scattering turn out to be the main
mechanisms that govern the temperature dependence of resistivity. Of all the inelastic scattering processes, inelastic electron-phonon
scattering is the most effective mechanism to destroy phase coherence of electron wave functions. The diffusion constant,
density of states at the Fermi level and the inelastic scattering time have been estimated, for the first time, for the alloys
in question
Article presented at the International Symposium on Advances in Superconductivity and Magnetism: Materials, Mechanisms and
Devices, ASMM2D-2001, 25–28 September 2001, Mangalore, India. 相似文献
89.
Hellweg T. Schemmel S. Rother G. Brlet A. Eckerlebe H. Findenegg G.H. 《The European physical journal. E, Soft matter》2003,12(1):1-4
The European Physical Journal E - The temperature-induced microphase separation of the binary liquid system iso-butyric acid+heavy water (iBA + D2O) in a mesoporous silica glass (CPG-10-75) of... 相似文献
90.
M. Uleysky L. Konkov S. Prants 《Communications in Nonlinear Science & Numerical Simulation》2003,8(3-4):329
We study the coupled translational, electronic, and field dynamics of the combined system “a two-level atom + a single-mode quantized field + a standing-wave ideal cavity”. In the semiclassical approximation with a point-like atom, interacting with the classical field, the dynamics is described by the Heisenberg equations for the atomic and field expectation values which are known to produce semiclassical chaos under appropriate conditions. We derive Hamilton–Schrödinger equations for probability amplitudes and averaged position and momentum of a point-like atom interacting with the quantized field in a standing-wave cavity. They constitute, in general, an infinite-dimensional set of equations with an infinite number of integrals of motion which may be reduced to a dynamical system with four degrees of freedom if the quantized field is supposed to be initially prepared in a Fock state. This system is found to produce semiquantum chaos with positive values of the maximal Lyapunov exponent. At exact resonance, the semiquantum dynamics is regular. At large values of detuning |δ|1, the Rabi atomic oscillations are usually shallow, and the dynamics is found to be almost regular. The Doppler–Rabi resonance, deep Rabi oscillations that may occur at any large value of |δ| to be equal to |αp0|, is found numerically and described analytically (with α to be the normalized recoil frequency and p0 the initial atomic momentum). Two gedanken experiments are proposed to detect manifestations of semiquantum chaos in real experiments. It is shown that in the chaotic regime values of the population inversion zout, measured with atoms after transversing a cavity, are so sensitive to small changes in the initial inversion zin that the probability of detecting any value of zout in the admissible interval [−1,1] becomes almost unity in a short time. Chaotic wandering of a two-level atom in a quantized Fock field is shown to be fractal. Fractal-like structures, typical with chaotic scattering, are numerically found in the dependence of the time of exit of atoms from the cavity on their initial momenta. 相似文献