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11.
Timokhin V. I. Zaborovskii A. B. Ferreri K. Chatgilialoglu C. 《Russian Journal of General Chemistry》2004,74(3):469-469
Russian Journal of General Chemistry - 相似文献
12.
Alabugin IV Timokhin VI Abrams JN Manoharan M Abrams R Ghiviriga I 《Journal of the American Chemical Society》2008,130(33):10984-10995
Despite being predicted to be stereoelectronically favorable by the Baldwin rules, efficient formation of a C-C bond through a 5-endo-dig radical cyclization remained unknown for more than 40 years. This work reports a remarkable increase in the efficiency of this process upon beta-Ts substitution, which led to the development of an expedient approach to densely functionalized cyclic 1,3-dienes. Good qualitative agreement between the increased efficiency and stereoselectivity for the 5-endo-dig cyclization of Ts-substituted vinyl radicals and the results of density functional theory analysis further confirms the utility of computational methods in the design of new radical processes. Although reactions of Br atoms generated through photochemical Ts-Br bond homolysis lead to the formation of cyclic dibromide side products, the yields of target bromosulfones in the photochemically induced reactions can be increased by recycling the dibromide byproduct into the target bromosulfones through a sequence of addition/elimination reactions at the exocyclic double bond. Discovery of a relatively efficient radical 5-endo-dig closure, accompanied by a C-C bond formation, provides further support to stereoelectronic considerations at the heart of the Baldwin rules and fills one of the last remaining gaps in the arsenal of radical cyclizations. 相似文献
13.
A mathematical model is proposed for layered crystals, based on a system of kinetic equations describing the change in charged relaxation oscillators with time. An analytical solution of this system is found and a theory constructed, which allows determination of the type and parameters of relaxation oscillators, as well as the properties of the crystals. A calculation of the thermostimulated depolarization current spectrum is confirmed by experiment.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 68–72, January, 1991. 相似文献
14.
Bertrand MP Escoubet S Gastaldi S Timokhin VI 《Chemical communications (Cambridge, England)》2002,(3):216-217
Thiyl radical promotes the isomerisation of allylic amines into enamines via two consecutive hydrogen atom abstraction steps, and the subsequent polar addition of the corresponding thiol to the enamine results in the cleavage of the C-N bond via a thioaminal intermediate: this reaction provides a mild, metal-free methodology for the deprotection of allylated primary and secondary amines. 相似文献
15.
Palladium(II)-catalyzed aerobic oxidative amination of styrene with oxazolidinone proceeds with catalyst-controlled regioselectivity: (CH3CN)2PdCl2 (1) and (Et3N)2PdCl2 (2) catalyze formation of the anti-Markovnikov and Markovnikov enecarbamate products, 3 and 4, respectively. Kinetic studies and deuterium kinetic isotope effects demonstrate that these two reactions possess different rate-limiting steps, and the data indicate that the product regiochemistry arises from the presence or absence of an effective Br?nsted base in the reaction. In the presence of a Br?nsted base such as triethylamine or acetate, the kinetically preferred Markovnikov aminopalladation adduct of styrene is trapped via rapid deprotonation of a zwitterionic intermediate and leads to formation of 4. In the absence of an effective Br?nsted base, however, slow deprotonation of this adduct enables aminopalladation to be reversible, and product formation proceeds through the thermodynamically preferred anti-Markovnikov aminopalladation adduct to yield 3. 相似文献
16.
A. B. Yakushev S. N. Timokhin M. V. Vedeneev Xu Honggui I. Zvara 《Journal of Radioanalytical and Nuclear Chemistry》1996,205(1):63-67
An isotope of element 106, namely263106, detected by its spontaneous fission, has been chemically isolated by thermochromatography of oxochlorides. The last one has been compared with short- and long-lived isotopes of Mo and W. Two chemical species were observed, presumably MO2Cl2 and MOCl4 (M=Mo,W). A kinetic dependence of these two species has been discussed and a chemical form [106]O2Cl2 has been described for the registered atoms of element 106. 相似文献
17.
The efficiency of model reduction via balancing for a multimass system with a nonlinear inertial link is demonstrated. As
an example, a three-mass dynamic system with a seismic damper is examined. The constraints of the seismic damper are assumed
to be ideal. The order of the system of differential equations is reduced by one. It is pointed out that the difference between
the numerically analyzed dynamic processes in the original and reduced systems is minor, which makes it possible to use the
method for justified simplification of nonlinear systems 相似文献
18.
I. V. Timokhin 《Computational Mathematics and Mathematical Physics》2018,58(4):621-630
The problem of solving a linear system with a Hankel or block-Hankel matrix, as well as Rissanen’s algorithm and its generalization to the block case, are considered. Modifications of these algorithms that use less memory (O(n) against O(n2)). 相似文献
19.
Kazantseva M. V. Timokhin B. V. Rokhin A. V. Blazhev D. G. Golubin A. I. Rybakova Ya. V. 《Russian Journal of General Chemistry》2001,71(8):1233-1235
The reaction of tertiary phosphine oxides with phosphorus oxychloride was found to give triorganylphosphonium dichlorophosphates R3PCl+PO2Cl2
- rather than phosphorylphosphonium salts R3P·OPOCl2. Mixtures of the reagents, called binary system, possess a considerable synthetic potential. They are capable of converting alcohols to the corresponding alkyl chlorides. 相似文献
20.
V. V. Dorokhova G. V. Ratovskii Yu. K. Maksyutin B. V. Timokhin E. F. Grechkin G. K. Semin 《Russian Physics Journal》1972,15(12):1751-1755
The mutual effect of atomic groups in acid chlorides of threeand four-coordination phosphorus was investigated by the nuclear quadrupole resonance of Cl35 (NQR Cl35) and Raman spectroscopy methods. On the basis of the NQR data it is suggested that in the ground state the interaction of unshared pairs of chlorine with the d orbitals of phosphorus is displayed weakly and the interaction of the indicated atoms is accomplished predominantly by an inductive mechanism. The integral intensities of the Raman lines of vibrations of the P-Cl and P=Cl bonds were measured. The Raman scattering data and the results of quantummechanical calculations by the molecular orbital method indicate some additional multiplicity of the P-Cl bond.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 12, pp. 75–80, December, 1972.The authors thank V. T. Aleksanyan and G. Kuz'yants for help in measuring the depolarization ratio. 相似文献