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71.
72.
Recently available differential cross section and density matrix information on π?p → B?p at 4 GeV/c are successfully described in terms of t channel exchanges and s channel absorptive effects. The s channel helicity amplitude which is dominant at small |t| (zero net helicity flip ω exchange) is found to have a zero at ?t = 0.2 GeV2. SU(3) and higher symmetries are used to predict cross sections for further axial vector meson production processes, in particular non-diffractive A1 production. The importance of these processes with regard to Regge phenomenology and meson spectroscopy is emphasized. 相似文献
73.
Prompted by some unusual features of the np charge-exchange cross sections recently measured at Fermilab, we study this process over the entire energy range in an attempt to clarify its exchange amplitude structure. Comparison with all the other two-body processes so far measured at Fermilab (π?p → π0n, νn, ω0n and elastic scattering) allows one to draw useful conclusions concerning the required J-plane structure of Regge cut models. We show that the shrinkage properties and helicity dependence of Regge cuts must be more complicated than current models suggest. We also present evidence that the Williams (or “poor man's absorption”) model for π exchange is incorrect at high energies. 相似文献
74.
The reactions have been studied at 52 MeV. Angular distributions have been taken and spectroscopic factors have been extracted by means of a DWBA analysis for states with excitation energies up to typically 10 MeV. Analog relations are proposed for mass-39 and mass-43 nuclei. A discussion of proton occupation numbers for various shells above and below the Fermi surface shows a substantial and about equal core excitation for 42Ca and 44Ca. Typically 70 % of the hole strengths have been located. The corresponding energy averaged strength distributions show quasihole structures whose widths are dominated by phonon-hole coupling to the first 2+ state in the target nucleus. 相似文献
75.
A.C. Irving 《Nuclear Physics B》1975,101(1):263-270
Recent polarisation data for pp and pn elastic scattering within the momentum range 6 to 45 GeV/c are economically described by a simple Regge model. A crucial feature of the model is the inclusion of a non-factorising pomeron which couples both to helicity flip and to non-flip. This allows an understanding of the observed t-dependent structure and rapid energy dependence of the pp polarisation. Predictions are made for pp and pn polarisation measurements at higher momenta. Fragmentary data on elastic polarisation are compared to predictions. 相似文献
76.
77.
78.
Solutions of the nonlinear Ginzburg-Landau equations in cylindrical symmetry have been computed for a type I superconductor. From these solutions the behaviour of a circular cylinder of infinite length in a magnetic field parallel to its axis has been deduced. For a series of values of the magnetic field solutions are given in two cases. The first case was calculated with the assumption of no fluxoid frozen in (fluxoid quantum number n=0), whereas in the second case a vortex with fluxoid quantum numbern=1 was assumed on the axis of the cylinder. For both series of solutions investigation of the thermodynamic stability was carried out. This and further thermodynamic considerations led to the result that in a gedankenexperiment the transition from the normal to the superconducting state and vice versa can be performed in a reversible manner. The expulsion of the magnetic field from the sample during the reversible transition to the superconducting state (Meissner-Effect) is also described by the solutions. Further results are the existence of a supercooled state down to a magnetic fieldH c2=κ√2Hcb and of a superheated state up to a fieldH c1>H cb. The value ofH c1 depends on the radius of the cylinder. If a condensation to the superconducting state takes place at a fieldH 0 whereH c2<H 0<H cb, condensation withn=0 seems to be preferred in comparison to that withn=1. 相似文献
79.
A.C. Irving 《Nuclear Physics B》1975,86(1):125-141
Pho-, photo- and electroproduction are compared and contrasted from a t-channel exchange point of view. A common exchange mechanism is evident. Systematic differences associated with the variable mass of the vector particle are found - in particular, the mass dependence of the non-pole-like contributions is reminiscent of that seen in higher mass resonance production. Naive vector meson dominance arguments which do not allow for these mass-dependent effects are shown to disagree both qualitatively and quantitatively with the data. We emphasize the implications of this, and similar studies, for an understanding of absorption effects in two-body scattering. 相似文献
80.