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51.
Jun Nakagawa Koichi Yamada Manfred Bester Gisbert Winnewisser 《Journal of Molecular Spectroscopy》1985,110(1):74-85
Rotational transitions of CH3CCSiH3 have been observed in the millimeter-wave region using a computer-controlled source-frequency modulation spectrometer with a 1.8-m-long free space absorption cell. The observed spectrum clearly showed the effect of internal rotation with a small potential barrier. It has been analyzed by calculating the torsion-rotation energies on the basis of torsional wave functions obtained by diagonalizing the torsional part of the Hamiltonian. The least-squares analysis has yielded the rotational constant B = 2068.2817(4) MHz and a few centrifugal distortion constants. The barrier height to internal rotation has been determined to be 3.77(70) cm?1 from the contour map of the standard deviation. Also, the A rotational constant of the silyl group around the symmetry axis has been estimated by fixing the A constant of the methyl group to the value of CH3CCH. 相似文献
52.
The determination of a precise vibrational energy level scheme for the two-dimensional bending mode of tricarbon oxide sulfide (3-thioxo-1,2-propadiene-1-one), OCCCS, has been carried out by relative intensity measurements of rotational transitions up to the seventh excited vibrational state of ν7. The harmonic wavenumber ω7 was determined to be 84.50 ± 0.63 cm?1 while the anharmonicity constant χ77 was found to be ?0.62 ± 0.11 cm?1, respectively. A linear dependence of the expectation value of the electric dipole moment on the vibrational quantum number υ7 was found. All results confirm that in O CCCS the potential function describing the two-dimensional oscillator of ν7 is very harmonic without a perturbing barrier to linearity as was found in the case of OCCCO. 相似文献
53.
The microwave spectrum of tricarbon oxide sulphide (3-thioxo-1,2-propadiene-1-one), OCCCS, is shown to be that of a linear molecule with Bo = 1413.898 MHz and Do = 0.046 kHz. The dipole moment was determined to be 0.634 debye. As a five-atomic linear molecule C3OS has three degenerate bending modes, ν5, ν6, and ν7. The l-type doubling constant for each of these modes was determined, and the vibrational frequencies have been estimated from these values and from relative intensity measurements. 相似文献
54.
The rotational spectra of formaldehyde, H212C16O and its isotopic species H213C16O, H212C18O, and H213C18O have been investigated in the ground vibrational state in the frequency region between 8 and 460 GHz. For most cases in which measurements of the a-type R- and Q-branch transitions already existed the accuracy of the line position has been improved to about 10 kHz. For H212C16O and H213C16O a large number of ΔKa = ±2 transitions were measured with similar accuracy. These new data when combined with all other available data and appropriate weightings lead to a set of ground state parameters which for the first time are compatible with infrared and ultraviolet data. The rotational constants (and 3σ standard deviations) obtained using Watson's A-reduced Hamiltonian are:
相似文献
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55.
E. Michael F. Lewen R. Gendriesch J. Stutzki G. Winnewisser 《International Journal of Infrared and Millimeter Waves》1999,20(6):1073-1083
We report an automatic frequency control (AFC) for an optically pumped far infrared (FIR) ring laser applicable for high resolution THz sideband spectroscopy by mixing a fraction of the laser power and a harmonic of a phase-locked synthesizer on a planar Schottky diode. We achieve a relative frequency accuracy of about 0.5 kHz rms at 803 GHz (
15
NH
3
) and about 1 kHz rms at 1626.6 GHz (CH
2
F
2
) over hours of lock time. The absolute frequency accuracy is estimated to be about 5 kHz at 1626.6 GHz. 相似文献
56.
Infrared-to-visible wave-length conversion in the Yb3+−Er3+ doped phosphors system has been described by a simple three level model based on two ions mechanism. The excitation in the
range of 900–1000 nm of an IR-photon is first absorbed by Yb3+ ion as a sensitizer attributed to the resonant energy transition in Er3+ ion from 4
I
3/2 → 4
S
15/2 and 1
F
9/2 → 4
I
15/2, respectively for green and red emission. The essential energy transfer processes in this system i.e. upconversion from 4
I
11/2 and 1
I
13/2, cross-relaxation from 4
S
3/2 and 1
F
9/2 are taken into account. The limitations of the rate-equation approach are examined with a focus on the underlying dynamics
of this rare-earth system. 相似文献
57.
Walsh MS Xu LH Lees RM Mukhopadhyay I Moruzzi G Winnewisser BP Albert S Butler RA DeLucia FC 《Journal of Molecular Spectroscopy》2000,204(1):60-71
New millimeter-wave and microwave measurements for CH(3)OD have been combined with previous literature data and with an extended body of Fourier transform far-infrared observations in a full global analysis of the first two torsional states (v(t) = 0 and 1) of the ground vibrational state. The fitted CH(3)OD data set contained 564 microwave and millimeter-wave lines and 4664 far-infrared lines, representing the most recent available information in the quantum number ranges J = 20 and K = 15. A 53-parameter converged global fit was achieved with an overall weighted standard deviation of 1.060, essentially to within the assigned measurement uncertainties of +/-100 kHz for almost all of the microwave and millimeter-wave lines and +/-6 MHz for the far-infrared lines. The new parameters for CH(3)OD are compared to previous results obtained for the (12)CH(3)OH, (13)CH(3)OH, and CD(3)OH isotopomers over the same quantum number ranges using the identical fitting program. Strong asymmetry-induced coupling between the accidentally near-degenerate 0E and -1E v(t) = 0 substates is successfully modeled by the fit. Copyright 2000 Academic Press. 相似文献
58.
In the microwave and millimeter wave spectra of HNCO, the b-type transitions between the Ka = 0 and 1 levels in the lowest excited vibrational state have been observed. Because of strong a-type Coriolis resonances among the three bending excited states the energy difference between the levels for Ka = 0 and 1 is much smaller in the lowest excited state than in the ground state. The subband origin of these b-type transitions has been found in the millimeter wave region at 275 697.309 MHz (9.1963 cm?1). The effect of the Coriolis resonances is discussed in relation to the molecular quasi-linearity and is compared with the case of HNCS. 相似文献
59.
The bending vibrations of linear, quasilinear, and bent molecules are qualitatively different phenomena. Each of these cases has been fully described by quantum mechanical formulations in the last half century, but important two-dimensional aspects of all three cases as well as the relationship between the three types of bending behavior remain difficult to visualize. Simple two-dimensional figures can help to provide an introduction to basic spatial and mathematical aspects of the bending problem. 相似文献
60.
G. Winnewisser R.A. Cornet F.W. Birss R.M. Gordon D.A. Ramsay S.M. Till 《Journal of Molecular Spectroscopy》1979,74(2):327-329
The two isotopic species CH2DCOOH and CH2DCOOD of acetic acid have been investigated with microwave spectroscopy in order to determine the equilibrium configuration of the methyl group, which was found to be eclipsed with respect to the carbonyl group. Centrifugal distortion constants free from internal rotation effects have been determined. A rs structure for the four hydrogens and a partial r0 structure for the whole molecule are given. 相似文献