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排序方式: 共有159条查询结果,搜索用时 15 毫秒
1.
Wojciech Bocian Jarosław Jaźwínski Lech Stefaniak Graham A. Webb 《Chemistry of Heterocyclic Compounds》1995,31(9):1103-1107
1H,13C,14N and15N NMR measurements are reported for four mesoionic 1-oxa-2, 3, 4-triazoles containing exocyclic nitrogenous groups. The NMR signal assignments are discussed and compared with those previously published for some corresponding oxatriazoles. The results obtained support the proposed cyclic mesoionic structures for the compounds studied. The questions of possible charge delocalization and valence tautomerism are addressed. Compound with N– H as a exocyclic group (Fig. 1) is found to be relatively unstable, this is attributed to proton migration in the corresponding non-cyclic form of this molecule.Published in Khimiya Geterotsikiicheskikh Soedinenii, No. 9, pp. 1260–1263, September, 1995. 相似文献
2.
J. R. Conder 《Journal of separation science》1984,7(11):615-619
The original plate model of chromatography is extended to the sorption process occurring at the column inlet and the desorption process at the column exit. At the column inlet it is shown that sufficiently wide feed bands undergo no change in concentration but a fall in band width, i.e., the volume of mobile phase occupied by the solute band is reduced. The reduction factor is (1 + k) where k is the mass distribution ratio (capacity factor). Narrower bands suffer partial reduction in both band width and concentration. On desorption at the outlet, however, the change is always in band width and not concentration. A perfect detector registers the true concentration-time profile of the band in the column if the solute mass fraction in the stationary phase is below 10?3 at the column outlet. The risks of stripping the stationary phase at high solute concentrations in analytical and preparative or production gas chromatography are compared. 相似文献
3.
Three-dimensional quantum mechanical calculations for vibrational predissociation of HeI2(B) van der Waals molecules are presented using the time-dependent wave packet technique within the golden rule approxima tion.The total and partial decay widths,lifetimes,rates and their dependence on initial vibrational states were obtained for HeI2 at low initial vibrational excited levels.Our calculations show that the calculated tota decay widths,lifetimes and rates agree well with those extrapolated from experimental data available The predicted total decay widths as a function of initial vibrational states exhibit highly nonlinear behavior.The very short propagation time (less.than 1 ps) required in the golden rule wave packet calculation is determined by the duration time of the final state inter-action between the fragments on the vibrationally deexcited adiabatic potential surface.The final state interaction between the fragments is shown to play an important role in determining the final rotational distri 相似文献
4.
Tamar Goldzak 《Molecular physics》2019,117(15-16):2179-2187
Interatomic coulomb decay (ICD) is a decay process relying on the Coulombic interaction between neighbouring atoms, molecules or nanostructures. Due to this process, an electron is emitted into the continuum. We study the ICD process in a system of the double quantum well heterostructure and investigate how we can manipulate the structure's parameters such that a better detection of the ICD's emitted electron is achieved. For this purpose, we calculated the partial widths (PWs) and branching ratios (BRs) of the ICD's emitted electron to the left and right asymptotes of the heterostructure; these will give an estimation of the detection current. We manipulated the structure's parameters and took into account the repulsion from the electron in the ground state located in the left well. By introducing two small barriers in the vicinity of the right QW, we observed a BR three times larger than in the structure without the barriers. We also investigate the effect of repulsion due to the second electron. This work gives a better understanding of the dynamics of the scattered ICD's electron, and realisation of better design rules for future experimental observation of ICD in nanostructures. 相似文献
5.
The di-gamma and di-gluon decay widths of P-wave cc mesons are computed in nonrelativistic phenomenological quark-antiquark potential of the type V (r) =-4 3 α s r+ Ar ν with different choices of ν using spectroscopic parameters.The numerically obtained radial solutions are employed to obtain the di-gamma and di-gluon decay widths.The computed decay widths are consistent with other model predictions as well as with the known experimental values in the range of potential index 0.7 ≤ν≤ 1.1. 相似文献
6.
Ch. Lisdat N. Vanhaecke D. Comparat P. Pillet 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,21(3):299-309
Two-photon photoassociation spectra in a Λ-type excitation scheme are analysed under the systematically varied experimental conditions of frequency detunings and laser
intensities. Line shape fits are presented as well as the investigation of intensity and detuning dependent line shifts. From
both we determine the attained spectroscopic precision, that is corrected for a systematic line shift due to the thermal distribution
of atoms in the trap. An energy correction for this effect is given. Information about the feasibility of generating translationally
cold molecules in a well defined rotational and vibrational level by the photoassociation process is derived from the analysis.
Received 21 May 2002 Published online 15 October 2002
RID="a"
ID="a"Current address e-mail: christian.lisdat@ptb.de
RID="b"
ID="b"e-mail: pierre.pillet@lac.u-psud.fr 相似文献
7.
激光金等离子体中Au~(49+)能级寿命的相对论多组态计算 总被引:1,自引:0,他引:1
根据扩展的相对论多组态Dirac Fock理论,采用"多功能相对论原子结构程序",计算了类锌Au49+的能级寿命、能级宽度和光谱跃迁波长。计算所得的波长值与实验结果符合较好;能级寿命与能级宽度的大小关系符合海森堡的能量与时间测不准原理。 相似文献
8.
The rf pulse response of I=3/2 spin system experiencing first order quadrupolar splitting is studied using density matrix approach. A general expression is derived in terms of spin populations, quadrupole splitting and duration and amplitude of the rf pulse for calculating the NMR signal arising due to the centre line and satellite resonances for the situation where the impressed rf pulse excites the resonances selectively as well as non-selectively. The necessary 4×4 transformation matrix obtained analytically by diagonalyzing the Hamiltonian are used to get the expression for the centre line response. The satellite signals are obtained in the same way but by using the numerical values of the roots of the related quartics. The widths of the corresponding π/2-pulses are calculated for different initial spin populations. The variations of this pulse-width and the corresponding signal amplitude as a function of satellite splitting are studied. 相似文献
9.
Z. T. Alwahabi J. Zetterberg Z. S. Li M. Aldén 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,42(1):41-47
High resolution Infrared Polarisation Spectroscopy (IRPS) and Infrared Laser
Induced Fluorescence (IRLIF) techniques were used to probe CO2/N2
binary gas mixture at atmospheric pressure and ambient temperature. The
probed CO2 molecules were prepared by laser excitation to an overtone
and combination ro-vibrational state (1201, J=15) of CO2, centred
at 4988.6612 cm-1. IRPS and IRLIF line profiles were recorded for
several CO2/N2 binary mixtures. The observed IRLIF line shapes
have the expected Lorentzian form while the observed IRPS line shapes are
narrower by a factor of two than those recorded with the IRLIF and appear to
have a Lorentzian-cubed profile. The recorded line profiles provide
measurements of the pressure-broadening coefficient directly at atmospheric
pressure. The Full-Width-Half-Maxima (FWHM) pressure broadening coefficients
are measured, based on IRLIF, to be 0.2174±0.0092 cm-1atm-1 and 0.1327
±0.0077 cm-1atm-1 for self- and N2 collision broadening,
respectively. The broadening coefficients obtained based on IRPS were
measured to be ~8% larger than those obtained with IRLIF. 相似文献
10.