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101.
Michael R. Whittaker Carl N. Urbani Michael J. Monteiro 《Journal of polymer science. Part A, Polymer chemistry》2008,46(18):6346-6357
The new SET‐LRP (using Cu(0) powder for organic synthesis) was successfully used to produce well‐defined linear and star homo‐ and diblock‐copolymers of PMA, PSA, and P(MA‐b‐GA)n (where n = 1 or 4). The kinetic data showed that all SET‐LRP were first order and reached high conversions in a short period of time. The other advantage of using such a system is that the copper can easily be removed through filtration, allowing the production of highly pure polymer. The molecular weight distributions were well controlled with polydispersity indexes below 1.1 and the number‐average molecular weight close to theory, especially upon the addition of Cu(II)Br2/Me6‐TREN complex. The linear and star block copolymers were then hydrolyzed to produce the biocompatible amphiphilic P(MA‐b‐GA)n, where the glycerol side‐groups make the outer block hydrophilic. These blocks were micellized into water and found to have a Rg/RH equal to 0.8 and 1.59 for the liner and star blocks, respectively. This together with the TEM's supported that the linear blocks formed the classical core‐shell micelles, where as, the star blocks formed vesicles. We found direct support for the vesicle structure from a TEM where one vesicle squashed a second vesicle consistent with a hollow structure. Such vesicle structures have potential applications as delivery nanoscaled devices for drugs and other important biomolecules. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6346–6357, 2008 相似文献
102.
Sans résumé
Presented by A. Horn. 相似文献
103.
In this work, new glass compositions in the TeO2-GeO2-Nb2O5-K2O system have been prepared and studied. The germanotellurite glasses were prepared by melt-quenching and their density, refractive index and characteristic temperatures have been determined. The structure of these glasses has been studied by infrared and Raman spectroscopies.The progressive replacement of TeO2 by GeO2 led to an increase of the glass transition and crystallisation temperatures of the glasses and a simultaneous decrease of their density and refractive index. Typical density and refractive index values of these glasses ranged from 4.98 to 3.85 g cm− 3 and 2.08 to 1.79, respectively, with increasing GeO2 content. The infrared spectra are dominated by a band ~ 640 cm− 1 in the tellurite glass and ~ 800 cm− 1 in the germanate glass. The Raman spectra of the germanotellurite glasses present an intense boson peak between ~ 34 and 47 cm− 1, together with high frequency peaks at ~ 670 cm− 1 and ~ 470 cm− 1 for high tellurite and high germanate glass compositions, respectively. The vibrational spectra of these germanotellurite glasses indicate that the glass network consists basically of TeO4 and [TeO3]/[TeO3 + 1] units, mixed with GeO4 and NbO6 polyhedra. 相似文献
104.
In models with extra dimensions, a black hole evaporates both in the bulk and on the visible brane, where standard model fields live. The exact emissivities of each particle species are needed to determine how the black hole decay proceeds. We compute and discuss the absorption cross sections, the relative emissivities, and the total power output of all known fields in the evaporation phase. Graviton emissivity is highly enhanced as the spacetime dimensionality increases. Therefore, a black hole loses a significant fraction of its mass in the bulk. This result has important consequences for the phenomenology of black holes in models with extra dimensions and black hole detection in particle colliders. 相似文献
105.
Bruno SM Monteiro B Balula MS Lourenço C Valente AA Pillinger M Ribeiro-Claro P Gonçalves IS 《Molecules (Basel, Switzerland)》2006,11(4):298-308
The tetrahedral triphenylsiloxy complex MoO(2)(OSiPh(3))(2) (1) and its Lewis base adduct with 2,2'-bipyridine, MoO(2)(OSiPh(3))(2)(bpy) (2), were prepared and characterised by IR/Raman spectroscopy, and thermogravimetric analysis. Both compounds catalyse the epoxidation of cis-cyclooctene at 55 degrees C using tert-butylhydroperoxide (t-BuOOH) is decane as the oxidant, giving 1,2-epoxycyclooctane as the only product. The best results were obtained in the absence of a co-solvent (other than the decane) or in the presence of 1,2-dichloroethane, while much lower activities were obtained when hexane or acetonitrile were added. With no co-solvent, catalyst 1 (initial activity 272 mol x molMo(-1) x h(-1)for a catalyst:substrate: oxidant molar ratio of 1:100:150) is much more active than 2(initial activity 12 mol x molMo(-1) x h(-1)). The initial reaction rates showed first order dependence with respect to the initial concentration of olefin. With respect to the initial amount of oxidant, the rate order dependence for 1 (1.9) was higher than that for 2 (1.6).The dependence of the initial reaction rate on reaction temperature and initial amount of catalyst was also studied for both catalysts. The lower apparent activation energy of 1 (11 kcal x mol(-1)) as compared with 2 (20 kcal x mol(-1)) is in accordance with the higher activity of the former. 相似文献
106.
107.
108.
Transparent SiO2:Li2O:Nb2O5 glass doped with Tm3+ has been prepared by the sol–gel method, and heat-treated in air (HT) at temperatures between 500 and 800 °C. X-ray diffraction (XRD) patterns and Raman spectroscopy show SiO2 and LiNbO3 phases in samples HT above 650 °C, and a NbTmO4 phase for T > 750 °C. The XRD SEM analysis show increasing particle size and number with the increase of HT temperature. Intra-4f12 transitions due to Tm3+ ion dispersed in the matrix are observed in samples with T > 650 °C. The luminescence is dominated by the 1G4 → 3F4 (~650 nm), 1D2 → 3F3 (~780 nm), 3H4 → 3H6 (~800 nm), 3H5 → 3H6 (~1200 nm) and 3H4 → 3F4 (~1500 nm) transitions under resonant excitation to the ion levels. 相似文献
109.
Melissa D'Ascenzio Kathryn M. Pugh Rebecca Konietzny Georgina Berridge Cynthia Tallant Shaima Hashem Octovia Monteiro Jason R. Thomas Markus Schirle Stefan Knapp Brian Marsden Oleg Fedorov Chas Bountra Benedikt M. Kessler Paul E. Brennan 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(4):1019-1024
110.
Juan Manuel Cornejo Luiz F. Monteiro Hanamantagouda P. Sankappanavar Ignacio D. Viglizzo 《Mathematical Logic Quarterly》2020,66(4):409-417
We determine the number of non-isomorphic semi-Heyting algebras on an n-element chain, where n is a positive integer, using a recursive method. We then prove that the numbers obtained agree with those determined in [1]. We apply the formula to calculate the number of non-isomorphic semi-Heyting chains of a given size in some important subvarieties of the variety of semi-Heyting algebras that were introduced in [5]. We further exploit this recursive method to calculate the numbers of non-isomorphic semi-Heyting chains with n elements such that removing the mth element () we are left with a subalgebra. We also solve a related problem posed in [1] of determining the number of ways a semi-Heyting chain with elements can be extended to a n element semi-Heyting chain by adding a new element in the mth place. Finally we combine these results by finding a second way to calculate the numbers that provides some extra information. 相似文献