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排序方式: 共有1360条查询结果,搜索用时 26 毫秒
1.
Chemistry of Heterocyclic Compounds - This microreview presents the current state of research on functionalization of α-mangostin, a natural hydroxyxanthone. Examples of transformations are... 相似文献
2.
E. S. Filatov S. V. Sysoev Ludmila N. Zelenina Tamara P. Chusova V. A. Logvinenko P. P. Semyannikov I. K. Igumenov 《Journal of Thermal Analysis and Calorimetry》2006,86(2):537-539
Thermal behaviour
of a series of lithium β-diketonates: Li(dpm) (dpm=dipivaloylmethanate
(2,2,6,6-tetramethylheptane-3,5- dionate)), Li(pta) (pta=pivaloyltrifluoracetonate
(2,2-dimethyl-6,6,6-trifluoro-3,5-hexanedionate)), Li(tfa) (tfa=trifluoracetylacetonate
(1,1,1-trifluoro-2,4-pentandionate)), Li(hfa) (hfa=hexafluoracetylacetonate
(1,1,1,5,5,5-hexafluoro-2,4-pentandionate)) has been investigated. Gas phase
composition of these complexes has been established. Temperature dependences
of vapor pressure of lithium compounds were obtained by static and dynamic
methods, and thermodynamic parameters were calculated. Dependence of compound
volatility on ligand structure is shown. For Li(dpm) detailed investigation
has been done by differential scanning calorimetry (DSC). 相似文献
3.
4.
Ginzburg B. M. Smirnov A. S. Filatov S. K. Shibaev L. A. Melenevskaya E. Yu. Novoselova A. V. Shepelevskii A. A. 《Russian Journal of Applied Chemistry》2003,76(3):457-459
The structure of aggregates of fullerene C6
0 introduced into films of radical polymethyl methacrylate in the stage of solution preparation was studied by wide-angle X-ray diffraction. 相似文献
5.
6.
We study the aggregation of oxygen dipoles well dispersed in a CaF2 crystal upon annealing at temperatures ranging from 370 to 420 K. The concentration of oxygen dipoles is monitored by measuring the intensity of the ionic thermocurrent peak as well as by absorption and luminescence spectroscopies. Results from three methods agree within experimental error and yield an activation energy of (1.2±0.1) eV for the diffusion of isolated oxygen centres in the crystal. 相似文献
7.
Philippe Boyer Gilles Renversez Evgeny Popov Michel Nevière 《Optical and Quantum Electronics》2006,38(1-3):217-230
The present work adapts a recent grating theory called “Fast Fourier factorization” to cylindrical coordinates in order to study microstructured optical fibers (MOFs). Compared with the classical differential method, this new differential method takes into account the truncation of Fourier series and the discontinuities of the fields across the diffracting surface with the help of new factorization rules. The main advantage of this method is that the directrix of the diffracting cylindrical surface is arbitrary and permits anisotropic and inhomogeneous media although its numerical application needs longer computation time, compared with other well-known numerical methods. The S-propagation algorithm is used to avoid numerical contaminations. The numerical results are validated and compared with the well-established Multipole method in the case of a MOF with six circular cylinders. Further, a new cross-sectional profile (with sectorial inclusions) that the Multipole method cannot consider is studied. 相似文献
8.
9.
K. Dzilinski G. N. Synyakov A. M. Shulga I. V. Filatov G. P. Gurinovich 《Radiation Physics and Chemistry》1995,45(6):923-928
Radical anions of Zn-chlorin, Zn-octaethylchlorin complexes and their 15N and deuterium substituted analogues have been studied by EPR spectroscopy and the INDO molecular orbital method in the unrestricted Hartree-Fock procedure. Parameters of experimental spectra, determined by using the iterative least-squares fitting method, have been compared with those calculated on the basis of spin density distribution. A satisfactory agreement between the experimental hyperfine coupling constants and theoretical ones for the systems studied has been obtained. 相似文献
10.
Yellowish crystals of K2[(UO2)As2O7] ( 1 ) have been synthesized by solid‐state reactions method. The structure of 1 [orthorhombic, Pmmn, a = 12.601(2), b = 13.242(2), c = 5.621(1) Å, V = 937.9(3) Å3, Z = 4] has been solved by direct methods and refined to R1 = 0.049, wR2 = 0.1060 for 1059 observed reflections. The structure of 1 is based upon [(UO2)As2O7]2? sheets formed by corner sharing between [UO6]6? distorted octahedra and [As2O7]4? polyarsenate groups. The K+ cations are either in eightfold or tenfold coordination and are located between the sheets. The topology of the uranyl arsenate sheet is related to silicate minerals of the melilite group and related synthetic silicate, aluminate and germanate compounds. 相似文献