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1.
M. A. Levina M. V. Zabalov V. G. Krasheninnikov R. P. Tiger 《Polymer Science Series B》2017,59(5):497-505
The kinetic regularities and the mechanism of the catalytic action of 1,5,7-triazabicyclo[4.4.0]dec-5-ene, which is the most active of the known catalysts for the formation of hydroxyurethanes from cyclocarbonates and amines, were studied using the example of the n-butylaminolysis of ethylene carbonate. In contrast with the noncatalytic reaction, which proceeds via two parallel pathways that involve one and two molecules of amine, the catalytic reaction follows a single pathway: the second molecule of amine is replaced by a molecule of the catalyst that accelerates the process in accordance with the mechanism of bifunctional catalysis. Different reaction pathways were studied by quantum chemical calculations based on the density functional method. It was shown that the high activity of 1,5,7-triazabicyclo[4.4.0]dec-5-ene results from the formation of a planar cation-like form of the catalyst. Moreover, the low-energy transition between the cation and the initial 1,5,7-triazabicyclo[4.4.0]dec-5-ene enables the catalyst to simultaneously be a good donor and acceptor of protons. This study presents a new way for finding among bifunctional organic compounds the catalysts that are even more active in the reaction of cyclocarbonates with amines. 相似文献
2.
The results are given of a calculation of laminar flow in a channel of square section and the motion of a turbulent jet from a cruciform nozzle in an ambient flow. To calculate the secondary flows, the field of the transverse velocity is decomposed into irrotational and solenoidal components. The results of the calculation of the flow in the channel are compared with the calculations of other authors and experimental data. To calculate the flow in the turbulent jet, a one-parameter turbulence model is used, and the influence of the inhomogeneity of the distribution of the longitudinal component of the velocity on the components of the Reynolds stress tensor is taken into account. The results of calculation of the flow in the jet behind a cruciform nozzle are compared with experimental data.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 4, pp. 36–44, July–August, 1984. 相似文献
3.
The results of an experimental investigation of the flow created by a conical jet spreading from a narrow slit around the periphery of a suction intake are described. The reorganization of the jet flow associated with the resulting three-dimensional flow structure is investigated. A flow scheme is proposed.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 2, pp. 187–190, March–April, 1991. 相似文献
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S. V. Polschikov P. M. Nedorezova T. V. Monakhova A. N. Klyamkina A. N. Shchegolikhin V. G. Krasheninnikov V. E. Muradyan A. A. Popov A. L. Margolin 《Polymer Science Series B》2013,55(5-6):286-293
New composite materials based on isotactic PP and fullerene were prepared via in situ polymerization with the use of an isospecific metallocene catalytic system. The stress-strain properties, thermophysical characteristics, and reactivities of composites in reactions of high-temperature decomposition, oxidation, and chemiluminescence were studied. The appreciable effect of fullerene on the thermal oxidation and crystallization behavior of composites (an increase in the crystallization temperature by 10 K) was found. It was shown that the protective inhibitory effect of fullerene in PP oxidation reactions is due to the interaction of fullerene nanoparticles with peroxy macroradicals. 相似文献
7.
A. P. Korobko S. V. Krasheninnikov I. V. Levakova S. N. Drozd S. N. Chvalun V. V. Nikolaev M. A. Shcherbina S. V. Cherdyntseva 《Polymer Science Series A》2011,53(1):75-84
It is shown that the noncatalyzed chemical grafting of an epoxy oligomer onto the surface of montmorillonite platelets may
proceed via the reaction between the epoxy groups and the hydroxyl groups of the organic modifying agent of the layered aluminosilicate.
The effect of grafting on the structure and heat resistance of the cured epoxy nanocomposite is studied. Complete exfoliation
of montmorillonite particles into individual platelets is shown to be a necessary but insufficient condition for increasing
the glass-transition temperature of the nanocomposite relative to that of the initial matrix. A much higher contribution to
the increase in the glass-transition temperature is ensured by grafting of epoxy molecular chains onto the surface of aluminosilicate
platelets; i.e., strong covalent matrix-aluminosilicate bonds form in addition to physical bonds, a process that entails development
of a thicker three-dimensional network. 相似文献
8.
Gerardo Algara‐Siller Dr. Nikolai Severin Samantha Y. Chong Dr. Torbjörn Björkman Dr. Robert G. Palgrave Andrea Laybourn Prof. Dr. Markus Antonietti Prof. Yaroslav Z. Khimyak Dr. Arkady V. Krasheninnikov Prof. Dr. Jürgen P. Rabe Prof. Dr. Ute Kaiser Prof. Andrew I. Cooper Prof. Dr. Arne Thomas Dr. Michael J. Bojdys 《Angewandte Chemie (International ed. in English)》2014,53(29)
9.
T. M. Ushakova E. E. Starchak V. G. Krasheninnikov A. A. Samoilenko P. V. Ivchenko I. E. Nifant’ev L. A. Novokshonova 《Kinetics and Catalysis》2012,53(1):75-83
Ethylene polymerization and ethylene-1-hexene copolymerization in the presence of metallocene catalysts based on Cp2ZrCl2, rac-Et(Ind)2ZrCl2, rac-Me2Si(2-Me-4-Ph-Ind)2ZrCl2, and rac-Me2Si(2-Me-4-Ph-Ind)2HfCl2 been investigated. The catalysts have been immobilized on montmorillonite (MMT) containing methylaluminoxanes (MMT-H2O)/AlMe3 or isobutylaluminoxanes (MMT-H2O)/ Ali-Bu3 synthesized directly on the support surface. The immobilized catalysts, with the general formula (MMT-H2O)/AlR3/Zr(Hf)-cene, show a high activity comparable with the activity of the respective homogeneous systems, which depends on the
nature of the metal and on the metallocene composition and structure. The catalytic properties of the metallocene systems
depend strongly on the nature of the activator as a component of the catalytic complex. (MMT-H2O)/Ali-Bu3 is a more effective activator of the hafnocene precatalyst in the polymerization processes than oligomeric methylaluminoxane
or methylaluminoxane synthesized on the support. The immobilization of the metallocenes on (MMT-H2O)/AlR3 leads to an increase in the molar mass of polyethylene and ethylene-1-hexene copolymers relative to the molar mass of the
polymers synthesized using the respective homogeneous systems. The immobilized metallocene catalysts display high selectivity
toward the insertion of a higher α-olefin (1-hexene) into the polymer chain, retaining this important property of their homogeneous
counterparts. 相似文献
10.
O. I. Kudinova V. G. Krasheninnikov A. A. Samoilenko T. A. Ladygina L. A. Novokshonova E. S. Petrov L. F. Rybakova 《Kinetics and Catalysis》2013,54(5):566-571
The polymerization of 1-butene over the TiCl4/MgCl2 (TMC) catalyst with the use of substituted phosphine oxides R n P(O)(CH2OR′)3 ? n (R = alkyl, R′ = methyl or acyl, n = 0–2)—new external electron donors-has been investigated. The electron-donating (coordinating) centers in these compounds are the phosphoryl group (P=O) and the oxygen atoms of the substituents at the phosphorus atom. The dependence of the 1-butene polymerization activity of TMC on the nature of the substituents in the phosphine oxides has been studied. The microstructure, degree of crystallinity, molecular weight, and strain-strength characteristics of the synthesized polybutene-1 and the effect of hydrogen on these properties are reported. The most efficient external donor is Me2P(O)CH2OAc. 相似文献