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21.
Geetha Rajappan 《Journal of Molecular Spectroscopy》2004,224(2):107-113
The rovibrational spectrum of 2ν9 band of CD3CCH is overlapped by two prominent hot bands identified as (2ν90+ν10±1)(E)←ν10±1(E) and 3ν9±1(E)←ν9±1(E), where ν10 and ν9 are the degenerate CCC and CCH bending fundamental vibrations, respectively. Assignment of lines to the transitions of these hot bands were carried out with the help of the high-resolution spectra recorded at ∼195 K and at room temperature. Molecular parameters for these hot bands have been obtained from the rotational analysis of the partially resolved K-structure lines. Only Q-head of the third hot band , originating from the lower 2ν10 state could be identified. 相似文献
22.
A theoretical model has been developed to account for certain features of both newly observed and previously reported CH3-bending subbands between 1450 and 1570 cm−1 in the high-resolution Fourier transform infrared spectrum of CH3OH [Can. J. Phys. 79 (2001) 435]. The features include (i) an apparent inversion of the rotationless E-A torsional splitting with respect to the ground state, i.e., the A state located above the E state, (ii) a pronounced upward slope in the K-reduced torsion-vibration energy pattern for the subband origins, and (iii) unexpected A1/A2 inversion of the K=2A and K=3AJ-rotational levels that led to ambiguity in identifying the vibrational mode as or . The model is an effective internal coordinate Hamiltonian constructed in G6 molecular symmetry with the CH3-bends coupled to each other and to torsion and including a- and γ-type Coriolis coupling. With this model, 33 out of 36 experimental upper-state K-term values for newly assigned , and ν10 subbands plus previous ν4 subbands have together been fitted successfully, employing 9 adjustable parameters and 17 fixed parameters to give a standard deviation of 0.14 cm−1. The Pγ Coriolis term appears to be the leading cause of the upward shift in the K-reduced energies. When J-dependence is introduced via a rotational Hamiltonian including b- and c-type Coriolis terms in addition to molecular asymmetry, the observed A1/A2 inversion of the K=2A and 3A rotational levels can also be reproduced. Predictions using the fitted K-rotation-torsion-vibration Hamiltonian show an interesting Coriolis-induced crossover and mixing of the ν5 and ν10 torsion-vibration energy patterns. These predictions played a role in identifying two of the new ν5 subbands in the crossing region, thereby helping to validate the model. 相似文献
23.
Summary Pressure broadening and shift parameters are measured for theJ=1−0 line of CH3C14N at 18.4 GHz, both for the three hyperfine components and for the single line which envelopes the hyperfine components, observed
at higher pressures (p≥40 mTorr). In agreement with theoretical predictions, these parameters are the same for all the observed lines: Γ
p
= (50 ± 5) MHz/Torr,s=(7±2) MHz/Torr. These values are compared with previous measurements, showing a large variance expecially for the shift parameter.
The measured broadening parameter is 40% lower than prediction of the Anderson theory.
Riassunto Sono stati misurati i parametri di allargamento e spostamento per pressione della rigaJ=1−0 del CH3C14N a 18.4 GHz. Tali misure sono state eseguite, sulle tre componenti iperfini e sul loro inviluppo osservato a pressionip≥40 mTorr. In accordo con le previsioni teoriche, questi parametri risultano gli stessi per tutte le righe osservate: Γ p = (50 ± 5) MHz/Torr,s=(7±2) MHz/Torr. Questi valori sono confrontati con quelli delle precedenti misure che mostrano una considerevole dispersione, specialmente per quanto riguarda il parametro di spostamento. L'allargamento per pressione è risultato piú basso di quello previsto dalla teoria di Anderson di circa il 40%.相似文献
24.
Riccardo Ricceri Alessandro Abbotto Antonio Facchetti Daniela Grando Gabriella Gabrielli Giorgio A. Pagani 《Colloids and surfaces. A, Physicochemical and engineering aspects》1999,150(1-3):289-296
We report on Langmuir-Blodgett (LB) films characterization of 4-[5-dicyanomethanido)thien-2-y1]-N-(n-hexadecyl)pyridinium (C16H33-PDCNT), and 1-(N-(n-hexadecy]-4-pyridinio)-2-[5-(dicyanomethanido)thien-2-yl]ethene (C16H33-PDCNTE); LB films of the pure compounds and of the mixtures of the two compounds were prepared at 291 K: UV-vis investigation revealed the presence of photobleachable absorption bands, the ones at about 530 nm and 640 nm were due to charge transfer transitions of the monomer of C16H33-PDCNT and C16H33-PDCNTE, respectively; the sharp, photobleachable ones shifted to shorter wavelengths were due to H-aggregates of the two compounds. By changing the molar ratios of the two compounds in the mixtures and in other cases by annealing the LB films, the absorption maxima of the sharp, photobleachable bands due to H-aggregates could be tuned in the range 415–467 nm. These LB films are thus very promising in view of optical data storage applications. 相似文献
25.
Summary The lattice dynamics of Li-intercalated FePS3 has been studied by means of a force constant model generated by a set of short-range two-body potentials. The intercalated
phases have been investigated for the three stoichiometric compositions: Li0.5FePS3, LiFePS3, Li1.5FePS3, with the aim of analysing the evolution of the host lattice normal modes as a function of the concentration, and of finding
the dispersion of the new phonon branches induced by lithium. The above special values of lithium concentration have been
chosen because the size of the unit cell keeps the same as in the host material. The force constants are fitted to the infrared
data and the phonon dispersion curves and the phonon energy densities have been calculated. A spectroscopic method for monitoring
lithium migration in the host material is proposed. 相似文献
26.
A.G. Andreev M. Georgiev M.S. Mladenova V. Krastev 《International journal of quantum chemistry》2002,89(4):371-376
Off‐center impurity ions in solids often perform rotations around their regular lattice sites. Unlike quasifree rotors with rotational line spectra subject to textbook attention in quantum mechanics, the off‐center species are hindered rotors with spectra quantized in rotational bands. These bands occur because of tunneling through barriers arising along the orbital path. For an off‐center ion rotating along a planar orbit, such as the Li+ impurity nearest‐neighboring an F center in alkali halide, the hindered rotation will give rise to specific magnetic moments that couple to and quantize external magnetic fields normal to the orbital plane. We present a simple theory and estimates of Li+ magnetic dipoles and rotational bands to find conditions for an experimental verification. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002 相似文献
27.
《中国物理 B》2021,30(6):66701-066701
Floquet theorem is widely used in the light-driven systems. But many 2 D-materials models under the radiation are investigated with the high-frequency approximation, which may not be suitable for the practical experiment. In this work,we employ the non-perturbative Floquet method to strictly investigate the photo-induced topological phase transitions and edge states properties of graphene nanoribbons under the light irradiation of different frequencies(including both low and high frequencies). By analyzing the Floquet energy bands of ribbon and bulk graphene, we find the cause of the phase transitions and its relation with edge states. Besides, we also find the size effect of the graphene nanoribbon on the band gap and edge states in the presence of the light. 相似文献
28.
The gas-phase Raman spectra of 1,3-butadiene and its 2,3-d2, 1,1,4,4-d4, and d6 isotopologues have been recorded with high sensitivity and resolution of 0.7 cm−1. Hot band series of fundamentals and combinations involving the ν13 torsional vibration of the s-trans rotamer have been observed for each of the isotopologues. Modes studied were ν10 (CH wag), ν12 (CH2 twist), ν10 + ν12, ν15 (CH2 wag) + ν16 (CH2 twist), and ν23 (CH2 rock) + ν24 (CCC deformation). The spacings of the quantum states of the torsional contribution were found to decrease with additional excitation of this mode (ν13) in the upper vibrational states except for the ν23 + ν24 combination state. 相似文献
29.
We consider Schrödinger operators with periodic potentials on periodic discrete graphs. The spectrum of the Schrödinger operator consists of an absolutely continuous part (a union of a finite number of non-degenerated bands) plus a finite number of flat bands, i.e., eigenvalues of infinite multiplicity. We obtain estimates of the Lebesgue measure of the spectrum in terms of geometric parameters of the graph and show that they become identities for some class of graphs. Moreover, we obtain stability estimates and show the existence and positions of large number of flat bands for specific graphs. The proof is based on the Floquet theory and the precise representation of fiber Schrödinger operators, constructed in the paper. 相似文献
30.
The pore size analysis of solids is widely applied in chemical industries, materials engineering, ceramic production, environmental engineering, catalysis, chromatography, nanotechnology, and many other fields. In spite of several new methods used for determining the pore size distribution of meso- and macropores [see IUPAC Recommendations of 1994], mercury porosimetry has remained one of the most popular methods employed for the characterisation of porous materials. In this paper, a new way is described for the estimation of certified pressure-volume curves from experimental curves measured by different laboratories in connection with the certification of new reference materials for a comparatively low-pressure range of mercury intrusion (<2 MPa). Simultaneous confidence and prediction bands for the certified pressure-volume curves are constructed by bootstrapping. 相似文献