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81.
K. L. Sandhya Yu. P. Panarin V. P. Panov J. K. Vij R. Dabrowski 《The European physical journal. E, Soft matter》2008,27(4):397-405
Results of the experimental study on different antiferroelectric liquid crystal (AFLC) materials are presented using a number
of techniques such as the optical birefringence, electro-optics and the measurements of optical thickness of free-standing
films. Despite differences in the molecular structures of the various AFLC materials studied, these are found to exhibit a
de Vries type of smecticA* (SmA
*) properties in a temperature range higher than SmC
* . This correlation leads to the conclusion that these two classes of liquid crystals are related to each other. Furthermore,
we suggest that these arise from the same physical mechanism, namely the existence of the weak synclinic (or reduced anticlinic)
correlations between the neighbouring molecular tilt directions. 相似文献
82.
We report measurements of the molecular tilt angle of a ferroelectric liquid crystal mixture (ZLI 3654), using infra-red spectroscopy, and of the optical tilt angle using polarizing microscopy. The molecular tilt angle is found to be approximately the same for different molecular vibrations. The second rank orientational order parameter for the axis of molecular vibrations of different groups of the molecule for homogeneously aligned samples have been determined as a function of temperature. The order parameter depends slightly on the sample thickness and is about 8 per cent higher for a lower thickness (∼ 7 μm) compared to a higher thickness (∼ 12 μm). The order parameter does not change significantly at the SC*-SA transition. The order parameter of SC* is found to be unaffected by the application of a constant electric field. The order parameter for the alkyl chain is found to be about three times lower than for the molecular core. 相似文献
83.
Prakash GK Etzkorn M Olah GA Christe KO Schneider S Vij A 《Chemical communications (Cambridge, England)》2002,(16):1712-1713
The conversion of ketones into geminal bis(difluoramines) can be achieved under mild two-phase reaction conditions by employing triphenylmethyldifluoramine as an in situ source of difluoramine. 相似文献
84.
The submillimetre spectra of several intensely absorbing liquids have been measured with a tunable submillimetre laser at several spot frequencies in the range from about 20 to 200cm?1. The spot frequency measurements enable us to check the accuracy of broadband power absorption spectra obtained by Michelson interferometry under a range of conditions and for several different types of heavily absorbing liquids, including aqueous solutions of current interest. 相似文献
85.
86.
Korlacki R Steiner M Meixner AJ Vij JK Hird M Goodby JW 《The Journal of chemical physics》2007,126(22):224904
The authors have investigated the conformational structure of the ferroelectric liquid crystal compound 4-3-methyl-2-chloropentanoyloxy-4"-hexyloxy-biphenyl also known under the abbreviations 3M2CPHOB and C6 using vibrational (IR and Raman) spectroscopy. The measured spectra exhibit two bands corresponding to the C=O stretching vibration that are separated by 20 cm(-1). In contrast, the molecular structure comprises only one such group. They assigned the two bands to different conformers that coexist in a temperature range between 25 and 65 degrees C covering the entire mesophase of this material. This assignment is strongly confirmed by calculated vibrational spectra based on the density functional theory. 相似文献
87.
To gain insight into the effects of liquid-liquid phase separation on molecular relaxation behavior we have studied an apparently homogeneous mixture of 5-methyl-2-hexanol and isoamylbromide by dielectric spectroscopy over a broad temperature range. It shows two relaxation regions, widely separated in frequency and temperature, with the low-frequency relaxation due to the alcohol and the high-frequency relaxation due to the halide. In the mixture, the equilibrium dielectric permittivity epsilon(s) of the alcohol is 41% of the pure state at 155.7 K and epsilon(s) of isoamylbromide is approximately 86% of the pure state at 128.7 K. The difference decreases for the alcohol component with decreasing temperature and increases for the isoamylbromide component. The relaxation time tau of 5-methyl-2-hexanol in the mixture at 155.7 K is over five orders of magnitude less than in the pure state, and this difference increases with decreasing temperature, but tau of isoamylbromide in the mixture is marginally higher than in the pure liquid. This shows that the mixture would have two T(g)'s corresponding to its tau of 10(3) s, with values of approximately 121 K for its 5-methyl-2-hexanol component and approximately 108 K for its isoamylbromide component. It is concluded that the mixture phase separates in submicron or nanometer-size aggregates of the alcohol in isoamylbromide, without affecting the latter's relaxation kinetics, while its own epsilon(s) and tau decrease markedly. 相似文献
88.
Stefan Schneider Ashwani Vij Jeffrey A. Sheehy Fook S. Tham Thorsten Schroer Karl O. Christe Karl O. Christe Karl O. Christe 《无机化学与普通化学杂志》2001,627(4):631-637
The reaction of KPO2F2 with the strong Lewis acid SbF5 was studied as a potential pathway to the unknown PO2+ cation. The resulting product has the desired PO2SbF6 composition but consists of an eight‐membered, antimony‐oxygen‐phosphorus‐bridged ring that was characterized by vibrational and NMR spectroscopy, ab initio methods, and a single crystal x‐ray diffraction study. The preferred formation of the ring and its mechanism are discussed. 相似文献
89.
90.
Kavita Kumari Ankush Vij K. H. Chae Mohd. Hashim Rezq Naji Aljawfi P. A. Alvi 《辐射效应与固体损伤》2017,172(11-12):985-994
Ni-doped CeO2 nanoparticles were prepared by using the co-precipitation method. The prepared nanoparticles were characterized using X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy, field emission scanning electron microscopy (FE-SEM) and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. The XRD results infer that Ni-doped CeO2 nanoparticles have single phase nature similar to that of pure CeO2 nanoparticles. We have calculated lattice parameters using Powder-X software, particle size using Scherer’s formula and strain using the Williamson-Hall method for all the synthesized samples. We have observed a systematic decrease in the lattice parameters, particle size and strain with an increase in Ni doping in CeO2. The FE-SEM micrographs also confirm that Ni-doped CeO2 have nanocrystalline behavior and particles are spherical shaped. From the Raman spectra, it is observed that the intensity of classical CeO2 vibration modes first increases then decreases with Ni doping. The NEXAFS spectra measured at Ce M4,5 and Ni L3,2 edges clearly indicate that Ce ions are in the +4 valence state and Ni ions are in the +2 valence state. 相似文献