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431.
利用在北京谱仪上获取的1.27×106ψ(2S)事例研究了末态为矢量介子与赝标量分子的ψ(2S)两体衰变过程,ψ(2S)→ρπ及KK,得到它们的衰变分支比上限在90%置信度下分别为3.6×10-5(ρπ),2.5×10-5(K+K-+C.C.)(C.C.代表电荷共轭态)及1.2×10-4(K0K0+C.C.).这些结果在新的实验灵敏度水平上证实了ψ(2S)相对于J/ψ强衰变中的反常压制现象的存在. 相似文献
432.
M. Vergote M. Van Schoor Y. Xu S. Jachmich R. Weynants M. Hron J. Stöckel 《Czechoslovak Journal of Physics》2005,55(3):389-400
To obtain a good confinement, mandatory in a fusion reactor, the understanding of the formation of transport barriers in the edge plasma of a tokamak is essential. Turbulence, the major candidate to explain anomalous transport, can be quenched by sheared flows in the edge which rip the convective cells apart, thus forming a barrier. Experimental evidence from the Chinese HT-6M tokamak [Y.H. Xu et al.: Phys. Rev. Lett. 84 (2000) 3867], points to the fact that momentum transfer from the turbulence can create these sheared flows via the Reynolds stresses. A new 1-D fluid model for the generation of the poloidal flow, has been developed taking into account the driving force of the Reynolds stress and the friction forces due to neutrals and parallel viscosity. Special attention has been dedicated to the computation of the flux-surface-averaging for the various terms. This model has been confronted with the experimental results obtained in the HT-6M tokamak, where Reynolds stresses were generated by application of a turbulent heating pulse. If the model is applied in cylindrical geometry, the calculated Reynolds stress-induced flow agrees well with the measured poloidal velocity in the plasma edge. However, when the full toroidal geometry is taken into account, it seems that the Reynolds stresses are too small to explain the observed rotation. This indicates that the role of the Reynolds stresses in inducing macroscopic flow in the torus is weakened. A combined system of probes allowing to measure the Reynolds stress and the rotation velocity simultaneously, has been developed and installed on the CASTOR tokamak (Prague). We report here on the first results obtained.Presented at the Workshop Electric Fields Structures and Relaxation in Edge Plasmas, Nice, France, October 26–27, 2004. 相似文献
433.
We first review the 20-year-old results of Letaw on stationary vacuum radiation patterns originating from world lines defined as Frenet–Serret curves. The corresponding body of literature as well as the experimental proposals that have been suggested to detect quantum vacuum field radiation patterns, are shortly presented and some related topics, such as the anomalous Doppler effect and the decay of accelerated protons are also included. 相似文献
434.
The transfer of information and signal velocity in an anomalous dispersion medium are studied. We propose that the discontinuous points in the envelop and its derivatives of any order are the information carried by a pulse different from others. The signal velocity will not exceed the speed of the shift of these discontinuous points. We study the propagation of pulses with a triangle envelop and with the envelop made up by three pieces of quadratic curve in dilute, anomalous dispersion gas with double gain lines. The discontinuous points of the envelop, its first derivative, and its second derivative are shown to propagate with vacuum speed of light c in the medium. A criterion has been suggested to determine theoretically whether the distortion of a pulse can be ignored. 相似文献
435.
Total attenuation cross sections of copper and silver have been measured in the energy range 5 to 85 keV in a narrow beam
good geometry set up using X- andγ-rays emitted from radio isotopes, by employing a high resolution hyper pure germanium detector. From the measured values,
the photoeffect cross-sections have been derived by subtracting a small contribution of the sum of the theoretical coherent
and incoherent scattering cross sections. The photoeffect cross-sections so obtained are found to be in better agreement with
the unrenormalized values of Scofield [10]. These photoeffect cross-sections have been used to evaluate the dispersion corrections
(also called anomalous scattering factors)f
+ andf″ for the forward Rayleigh scattering amplitude by a numerical evaluation of the dispersion integral that relates them at the
energies at which the cross-sections have been measured. To thef
+ values so obtained, the relativistic corrections proposed by different investigators are included separately and the valuesf′ so obtained are compared with the available data and discussed. Possible conclusions are drawn from the present study. 相似文献
436.
As a deepening and extension of Theory of Unified Representation of Gravitational Field~([1]), this paper covers two aspects as follows: in theory, we go into the fundamental structure of the internal problem and put emphasis on seeking the solution of the disturbing potential in spectral domain and establishing a spectral structure form of anomalous density; and in application, according to the given form we try to take a look at the distribution charateristics of anomalous densities of lithosphere about 30—40 km deep in the continent of China in illustration of evaluating practical trustworthiness of the present theory. Calculations done here are based on earth gravity model DQM84D~([2]) and show that this theory seems to be convincing. 相似文献
437.
B V B Sarkissian A K Grover G Balakrishnan Ravi Kumar P L Paulose R Vijayaraghavan V Sankaranarayanan C K Subramanian 《Pramana》1992,38(6):641-667
The results of experimental studies on hysteresis in magnetization, thermomagnetic history effects, anomalous variations in
magnetic hysteresis curves and the decay rates of magnetization obtained under different thermomagnetic histories in specimens
of conventional and high temperature superconductors are presented. The Bean’s critical state model is considered adequate
to explain magnetic behaviour in conventional hard superconductors. The similarity in the general features of the results
of different experiments on specimens of the two families of superconductors underscores the efficacy of the said model to
understand some aspects of the macroscopic magnetic response of high temperature superconductors as well. For instance, the
isothermal magnetization hysteresis loop which comprises of magnetization curves along forward (−H
max to +H
max) and reverse (+H
max to −H
max) paths define an envelop within which all isothermal magnetization data along different thermomagnetic histories lie. There
exist inequality relationship between various field values identified asH
peak,H
I,H
II etc. in isothermal magnetization hysteresis as well as magnetic relaxation data. The entire field span of an isothermal magnetization
hysteresis data set can be considered to comprise of three parts corresponding to (M
rem(H)−M
FC(H)+M
ZFC(H)) being equal to, less than or greater than zero, whereM
rem(H) are the remanent magnetization values obtained on reducing field to zero after having the specimen in different applied
field (H) values. There are, however some situations amongst thermomagnetic history effects in specimens which show incomplete flux
trapping on field cooling, where the critical state model has been found inadequate. 相似文献
438.
Malcolm H. Mac Gregor 《Foundations of Physics Letters》1992,5(1):15-23
High-energy scattering experiments mandate a point-like charge on the electron. However, the spectroscopic properties of the electron suggest an overall Compton-sized geometry. Adopting the model of a Compton-sized electron or positron that has a equatorial point charge, we use detailed computer calculations of classical Coulomb scattering off atomic nuclei to delineate the boundaries of a narrow energy window, in the KeV range, in which finite-size effects should be observable. Some experimental evidence for these finite-size effects can be found in the published literature.1. This work was performed under the auspices of the U. S. Department of Energy by the Lawrence Livermore National Laboratory under contract No. W-7405-ENG-48.2. The impact parameters shown in Fig. 1 were obtained by numerical integration of point-particle trajectories, with relativistic effects and nuclear screening included.3. When rotational and recoil effects are set equal to zero, the calculated large-positron elastic differential cross sections are accurately point-like at all incident energies.4. The calculations shown here required more than 10,000 hours of computer time on a network of seven Sun SPARC 1 and SPARC 2 computers. 相似文献
439.
Rosario Nunzio Mantegna 《Journal of statistical physics》1993,70(3-4):721-736
We perform a detailed study of the time evolution of the probability distribution for two processes displaying enhanced diffusion: a stochastic process named the Lévy walk and a deterministic chaotic process, the amplified climbing-sine map. The time evolution of the probability distribution differs in the two cases and carries information which is peculiar to the investigated process. 相似文献
440.