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排序方式: 共有425条查询结果,搜索用时 15 毫秒
1.
J. M. Kumpula J. Saramäki K. Kaski J. Kertész 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,56(1):41-45
According to Fortunato and Barthélemy, modularity-based community detection
algorithms have a resolution threshold such that small communities in a large
network are invisible. Here we generalize their work and show that the q-state
Potts community detection method introduced by Reichardt and Bornholdt
also has a resolution threshold. The model contains a parameter by which this threshold can be tuned, but no a priori principle
is known to select the proper value.
Single global optimization criteria do not seem capable for detecting all
communities if their size distribution is broad. 相似文献
2.
Kazuhiro Yamamoto Haruhiko Ito Kouki Totsuka Tomohiro Sato 《Optics Communications》2006,265(2):692-695
We consider a new scheme of optically ionizing atoms with 10-nm-order spatial resolution. In this method, two-color near-field lights are generated on a narrow slit illuminated by two-color evanescent lights via total-internal reflection of two-wavelength light beams. In order to illustrate the feasibility, we first obtain the ionization cross section from two-step photionization of cold Rb atoms by two-color evanescent lights on a plane surface of a prism. Then, we numerically estimate the ionization efficiency as a function of the slit width using Bethe formula. The scheme is useful for detecting ground-state atoms under less perturbation by scattered light. 相似文献
3.
We present theS
1 Raman spectra of 1,4-DiPhenyl-1,3-Butadiene (DPB) in a series of linear alkanes (pentane, hexane, heptane, octane, decane, and dodecane). Bands assignable to both the 11
B
u
and 21
A
g
states are present, suggesting that the state we are observing in solution is a mixed state with both 11
B
u
and 21
A
g
character. The relative intensities of several bands associated with CoCo stretching motions in the 21
A
g
and 11
B
u
states change systematically through the solvent series. The relative intensity changes reflect a changing distribution ofs-trans conformers inS
1 DPB as the solvent is varied. We suggest that the distribution ofs-trans conformers inS
1 DPB controls the nature of the mixing between the 21
A
g
and 11
B
u
states and that the distribution of conformers is controlled by the solvent viscosity. Changes in the peak position and bandwidth of the phenyl C=C stretch with delay reflect vibrational relaxation processes inS
1 DPB. We observe anomolous behavior in pentane that we attribute to the effect of the solvent structure on the ability of DPB to exchange energy with pentane. 相似文献
4.
W. Clauss A. A. Il'yukhin D. N. Kozlov V. V. Smirnov O. M. Stel'makh K. A. Vereschagin 《Applied physics. B, Lasers and optics》1996,62(3):279-285
In this work, we present the results of two-wavelength (2)-CARS thermometry of hydrogen at temperatures from 300–1200 K. The choice of the pair of spectral lines for the 2-CARS thermometer with respect to optimal temperature sensitivity within a given temperature range was analysed. Software was developed to process the experimental data and calculate the temperature. In the experiments, temperature and density were measured in a heated cell using single-shot and averaged CARS intensities in the pure rotationalS branch. The accuracy achieved and its dependence on measured temperature values and on the number of averaged shots was analysed.The sponsoring of this work by the Stabsabteilung Internationale Beziehungen at the Kernforschungszentrum Karlsruhe under project number RUS 222.12 is gratefully acknowledged 相似文献
5.
Using atomic beam technique, a combination of collisional and laser excitation, and photoion detection, autoionizing Cu I states in the region of the ionization limits Cu II 3d
9 4s(3,1
D) were investigated. In spite of the complicated structure of the signals due to the four different ionization limits3
D
3,3
D
2,3
D
1 and1
D
2 and the large number of possible (LSJ)-states, which can be reached by this experimental technique, the majority of the signals could be attributed to definite Rydberg series 3d
9 4s(3
D
3,3
D
2,3
D
1,1
D
2)nl (LSJ). Perturbations were analyzed by the three- and four-channel quantum defect theory and by Hartree-Fock calculations. General formulas for the calculation of the photoionization cross section by the four-channel quantum defect theory in the case of two closed and two open channels are given. 相似文献
6.
F. Offi L. Avaldi R. Camilloni G. Dawber G.C. King G. Stefani 《Journal of Electron Spectroscopy and Related Phenomena》2007
Threshold photoemission spectroscopy (TPES) is used to measure the Fe 2p spectrum of a stainless steel sample. The obtained spectrum is compared with analogous spectra measured by X-ray photoemission and absorption spectroscopies. The results of this comparison suggest that resonant two-electron autoionization processes, rather than direct photoemission from the core level, are the main mechanisms contributing to the signal. Limits and applicability of this experimental approach to investigate bulk electronic properties in solids are discussed. 相似文献
7.
A new method to prepare photoions with the polarized nuclear spin is proposed. Selected total electron momentum state |J,mJ〉 is excited by short (pico- or (sub)nanosecond) spectrally broad laser pulse which does not resolve a hyperfine structure thus preparing a superposition of all sublevels of the total angular momentum F of an atom. Initially unpolarized nuclear spin state becomes highly polarized in a course of subsequent free quantum evolution, and at appropriate time an atom is ionized by another short laser pulse. For the case of nuclear spin I=1/2, absorption of only one polarized photon is needed to achieve 100% nuclear polarization. 相似文献
8.
J. Seres J. Klebniczki E. Seres J. Hebling 《Applied physics. B, Lasers and optics》1998,67(5):569-572
Received: 1 April 1998/Revised version: 20 April 1998 相似文献
9.
S. Cohen 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1998,4(1):31-38
Approximate analytical formulae describing the energy variation of line intensities, autoionization widths and lineshape asymmetries,
are derived for a Phase-Shifted Multichannel Quantum Defect Theory model composed of two closed interacting channels coupled
to two effective continua. This is accomplished by putting the two compatibility equation solutions, for the common phase
shifts of the two open channels, in such a form so the resonant behavior is attributed to one of them, the other accounting
for an energy dependent background. Then, the well-known procedures for the simpler case where only one continuum is considered
are applied, using only the resonant solution. The method is quite general and applicable to any MQDT model with two or more
open channels. The resulting analytical formulae are tested on experimental spectra of Sr, Ba and Cu and it is shown that
they are valid as long as: i) The resonances are non-overlapping, ii) The direct closed channel coupling is much stronger
than the indirect one through the continua and (when excitation matrix elements are involved) iii) The open channels excitation
strength is smaller or at least comparable to the closed channels one.
Received: 26 May 1998 / Accepted: 1st July 1998 相似文献
10.
V. N. Bagratashvili Yu. G. Vainer V. S. Doljikov S. F. Koliakov A. A. Makarov L. P. Malyavkin E. A. Ryabov E. G. Silkis V. D. Titov 《Applied Physics A: Materials Science & Processing》1980,22(1):101-105
The method of spectroscopy of spontaneous Raman scattering (RS) with time resolution has been applied for the first time to
diagnose the process of multiphoton ir molecular excitation (MPE). Some aspects of RS diagnostics of MPE processes are being
analyzed. It has been shown experimentally on SF6 and CF3I molecules that it is possible to study such important characteristics of excitation process as the fraction of molecules
involved in the process of excitation, vibrational energy distribution of molecules, stochastization of inner molecular energy. 相似文献