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排序方式: 共有119条查询结果,搜索用时 186 毫秒
1.
Lightly cross-linked anisotropic networks with uniaxial and π/2 twisted orientations were produced by photopolymerization of monotropic mixtures containing liquid crystal mono and diacrylates. In this way the polymer backbone was immobilized and became decoupled from the motion of the mesogenic side groups. The networks showed very good reversibility and even after becoming isotropic, upon cooling, the initial orientation was recovered. In the same way, in the presence of electric fields the mesogenic groups could be reoriented in the direction of the electric field, reverting back to the initial orientation on removal of the field at a rate comparable with those observed in the monomeric state. Combining viscoelastic measurements with the dielectric behaviour of the monomeric liquid crystal and the anisotropic network, a comparison between the internal and bulk rotational viscosities was also made. 相似文献
2.
H Yurtseven I E Caglar 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2002,58(1):55-65
We calculate here the Brillouin frequencies of the L-mode [010], [001] and [100] of NaNO2 for the phase transitions from the paraelectric phase to the sinusoidal anti-ferroelectric phase near the Neel temperature (TN = 437.7 K) and to the ferroelectric phase near the critical temperature (TC = 436.3 K) in this crystalline system. For calculating the frequencies. we use the thermal expansivity data for the phase regions considered, under the assumption that the mode Gruneisen parameter determined for each mode remains constant across the phase transitions. Our calculated frequencies agree well with the observed frequencies for the modes studied in NaNO2. 相似文献
3.
The surface area of kaolinite-benzamide (K-Bz)6.62 m2 g–1, whichis noticeably lower than that of kaolinite-dimethyl sulphoxide (K-DMSO) 14.61m2 g–1, the co-perturbationof the inner-surface hydroxyl features at 3697 and 3650 cm–1,and the increase of d(001) value by 7.44 Å are all related to the benzamidespecies inserted into the kaolinite structure through the replacement of theK-DMSO composites. Disappearance of the DMSO reflections and emergence ofwell-defined features at 6.04(2θ) and 11.16(2θ), 001 and 002 reflectionswith d values of 14.62 and 7.92 Å, respectively point out that the DMSOspecies were substituted efficiently by benzamide molecules. The thermal stabilityof the K-Bz derivative up to 300°C can be attributed to the slightly tiltedaromatic ring keying into the gibbsitic sheets via the –NH2groups. 相似文献
4.
Anthracene Substituted Co (II) and Cu (II) phthalocyanines; Preparations,Investigation of Catalytical and Electrochemical Behaviors 下载免费PDF全文
An approach to investigation of catalytical behaviors of Co (II) and Cu (II) phthalocyanines is reported that is based on changing any parameter to effect these behaviors. Towards this end, new anthracene substituted Co (II) and Cu (II) phthalocyanines were prepared and characterized spectroscopic methods. New cobalt (II) and copper (II) phthalocyanines were used as catalyst for oxidation of different phenolic compounds (such as 2,3‐dichlorophenol, 4‐methoxyphenol, 4‐nitrophenol, 2,3,6‐trimethylphenol) with different oxidants. Then, electrochemical characterization of cobalt (II) and copper (II) phthallocyanines were determined by using cyclic voltammetry (CV) and square wave voltammetry (SWV) techniques. Although copper (II) phthalocyanine showed similar Pc based electron transfer processes, cobalt (II) phthalocyanine showed metal and ligand based reduction reactions as expected. 相似文献
5.
Abstract The dielectric relaxation of the liquid crystal 4-n-pentyl-4′-cyanobiphenyl (K15) in the presence of an anisotropic network has been studied. Anisotropic networks containing K15 molecules were prepared by in situ polymerisation of liquid-crystalline diacrylate molecules in a mixture containing K15. By changing the network concentration, the effect of the network molecules on the behaviour of the K15 molecules, which were not chemically attached to the network, was investigated. With increasing network concentration it was found that the mean relaxation times of K15 molecules shifted to lower temperatures and that their distribution became broader. The activation energy associated with the relaxation, however, remained almost constant before showing some increase at high network concentrations. 相似文献
6.
R. A. M. Hikmet 《Liquid crystals》2013,40(11-12):1407-1418
A Commentary on the paper “Anisotropic gels and plasticized networks formed by liquid crystal molecules”, by R. A. M. Hikmet. First published in Liquid Crystals, 9, 405–416 (1991). 相似文献
7.
Koruyucu Elif Ekici Selcuk Karakoc T. Hikmet 《Journal of Thermal Analysis and Calorimetry》2021,145(3):1303-1315
Journal of Thermal Analysis and Calorimetry - This study presents determining performance parameters as well as thermodynamic analysis through certain design parameters of a two-spool turbojet... 相似文献
8.
The synthesis of chiral liquid crystalline diacrylates is described. By mixing one of them with non-chiral liquid crystalline diacrylates. cholesteric phases are obtained of which the wavelength of reflection can be chosen by the composition of the mixture. After isothermal photopolymerization of the mixture a crosslinked network is obtained with thermally stable properties. 相似文献
9.
Yasemin Caglar Saliha Ilican Mujdat Caglar Fahrettin Yakuphanoglu 《Journal of Sol-Gel Science and Technology》2010,53(2):372-377
Undoped and manganese doped ZnO (ZnO:Mn) films were prepared by sol gel method using spin coating technique. The effect of
Mn incorporation on the structural and optical properties of the ZnO film has been investigated. The crystalline structure
and orientation of the films have been investigated by using their X-ray diffraction spectra. The films exhibit a polycrystalline
structure. Mn incorporation led to substantial changes in the structural characteristics of the ZnO film. The scanning electron
microscopy (SEM) images of the films showed that the surface morphology of the ZnO film was affected by the Mn incorporation.
The transparency of the ZnO film decreased with the Mn incorporation. The optical band gap and Urbach energy values of the
ZnO and ZnO:Mn films were found to be 3.22, 3.19 eV and 0.10, 0.23 eV, respectively. The optical constants of these films,
such as refractive index, extinction coefficient and optical dielectric constants were determined using transmittance and
reflectance spectra. The refractive index dispersion curve of the films obeys the single oscillator model with dispersion
parameters. The oscillator energy, E
o
, and dispersion energy, E
d, of the films were determined 5.30 and 16.26 eV for ZnO film and 5.80 and 12.14 eV for ZnO:Mn film, respectively. 相似文献
10.
Christian Hammer Benjamin Walther Hikmet Karabulut Manuel M. Lohrengel 《Journal of Solid State Electrochemistry》2011,15(9):1885-1891
Anodic Ta oxide films are said to inhibit oxygen evolution. In industry, however, large amounts of gas are evolved during
the anodization of tantalum anodes for electrolytic capacitor fabrication. We quantified the oxygen by fluorescence quenching
in a flow-through cuvette and found that 4% of the anodic charge are consumed for oxygen evolution. In wires or sheets, this
oxygen is removed by diffusion without bubble formation and, thus, not recognized. Due to the large inner area of the sintered
Ta anodes, the oxygen evolution causes strong oscillations of the current density and bubble formation. The amount of oxygen
is proportional to the oxide amount formed in parallel. This is explained by a model where mobile ions during oxide growth
form interband states which allow electron tunneling. Accordingly, stationary no oxygen evolution is observed. 相似文献