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61.
62.
We study the relative modular classes of Lie algebroids, and we determine their relationship with the modular classes of Lie algebroids with a twisted Poisson structure. To cite this article: Y. Kosmann-Schwarzbach, A. Weinstein, C. R. Acad. Sci. Paris, Ser. I 341 (2005). 相似文献
63.
Cacile Marivingt-Mounir Yvette Mettey Jean-Michel Vierfond 《Journal of heterocyclic chemistry》1998,35(4):843-845
A one-pot synthesis of 1, 3 and 4-cyanophenothiazines and a two-step approach to 2-cyanoisomer have been developed. The condensation of 2-aminobenzenethiol and 2,3 or 3,4-dihalogenobenzonitriles followed by Smiles rearrangement or by intramolecular aromatic substitution gave the desired ring systmes. 相似文献
64.
Bongjin Simon Mun Kai Chen Youngchul Leem Catherine Dejoie Nobumichi Tamura Martin Kunz Zhi Liu Michael E. Grass Changwoo Park Joonseok Yoon Y. Yvette Lee Honglyoul Ju 《固体物理学:研究快报》2011,5(3):107-109
VO2 single crystals with unprecedented quality, exhibiting a first‐order metal–insulator transition (MIT) at 67.8 °C and an insulator –insulator transition (IIT) at ~49 °C, are grown using a self‐flux evaporation method. Using synchrotron‐based X‐ray microdiffraction analysis, it is shown that the IIT is related to a structural phase transition (SPT) from the monoclinic M2 phase to the M1 phase upon heating while the MIT occurs together with a SPT of M1 to the rutile R phase. All previous reports have shown that VO2 exists in the M1 phase at room temperature in contrast to the M2 phase observed in this work. We suggest that internal strain inside single crystal VO2 may generate the previously unobserved IIT and the unusual room temperature structure. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
65.
66.
Hervé Cousin Valérie Peulon-Agasse Jean-Claude Combret Pascal Cardinael 《Chromatographia》2009,69(9-10):911-922
This work deals with the evaluation of three monohydroxy methylated β-cyclodextrin isomers as chiral selectors for capillary gas chromatography. Chromatographic properties of these stationary phases have been investigated in terms of efficiency, inertness and polarity. Injections of homologous series of hydantoin derivatives and 1-phenylethan-1-ol have highlighted the predominant influence of hydroxyl groups in 2 or 3 positions on chiral discrimination. By contrast, presence of hydroxyl groups in 6-O-position did not significantly influence the enantioseparation ability. Moreover, T iso calculated on TRIMEB-2-OH in OV1701-OH and on pure TRIMEB-2-OH for 5-methyl-5-alkyl hydantoin derivatives were notably different indicating that polysiloxan–selector interactions could not be neglected. 相似文献
67.
The action of phenyllithium on pyrazine, 2-methyl pyrazine and acetonyl pyrazine gave mono- or di-addition products with azomethines bonds of pyrazine. The adducts can be condensed with methyl benzoate to give C or N condensed derivatives. No product with initial metalation of methyl or acetonyl groups was observed. 相似文献
68.
Van Eeckhaut A Detaevernier MR Crommen J Michotte Y 《Journal of separation science》2004,27(1-2):21-27
Methanol enhances the enantioresolution of dimetindene enantiomers with carboxymethyl-beta-cyclodextrin (CMCD) as chiral selector at a concentration below its optimal value. The same effect was observed with ethanol (EtOH), although less pronounced. On the other hand, the addition of isopropanol (IP) or acetonitrile (ACN) decreases the enantioseparation. To elucidate the underlying mechanisms of these observed effects, other neutral (beta-CD, hydroxypropyl-beta-CD, and trimethyl-beta-CD) as well as chargeable (carboxyethyl-beta-CD and succinyl-beta-CD) CD derivatives were also tested with MeOH as organic modifier. It can be concluded that the increased enantioresolution of dimetindene enantiomers was only noted with CMCD as chiral selector and a short-chain organic modifier containing an alcohol function. The slight deprotonation of CMCD at pH 3.0 was only partly responsible for the high enantioselectivity and the 'favourable' effect of MeOH or EtOH. An important feature that can be concluded from these results is that for this particular analyte approximately the same resolution can be obtained with a lower CMCD concentration and the addition of some MeOH, compared to a MeOH free buffer. 相似文献
69.
Ngono-Ravache Y Corbin D Gaté C Mélot M Balanzat E 《The journal of physical chemistry. B》2007,111(11):2813-2819
In this article, we focus on the influence of side groups on terminal alkyne creation, in aliphatic polymers submitted to swift heavy ions, under vacuum. Terminal alkyne creation was compared in polyethylene and in substituted polymers. We selected two classes of side groups: alkyl groups, which differed in their length (polypropylene and polybutene) and allyl groups, which were linear (EPDMh) or cyclic (EPDMn). Irradiated samples were analyzed using Fourier transform IR spectroscopy, in the transmission mode, at room temperature. Alkynes are created when the electronic stopping power, (dE/dx)e, exceeds a threshold value. This threshold value was moderately influenced by the presence of an alkyl side chain but was clearly reduced in the presence of C=C bonds on the side chain. Nevertheless, in all-saturated polymers, below the (dE/dx)e threshold, terminal alkyne formation is observed after a latent dose, rather independently of the side-chain length and directly related to the formation of radiation-induced double bonds prior to alkyne formation. Under S ion irradiation, the radiation chemical yield G0 value obtained in EPDMh was 4 times the value of G0 in PE. This effect is understandable only if important energy transfers, from the backbone to C=C double bonds, are considered. 相似文献
70.
We have synthesised a library of phosphite-oxazoline ligands derived from readily available D-glucosamine. These ligands have been successfully screened in the palladium-catalysed Heck reaction of several substrates with high regio- (up to 99 %) and enantioselectivities (ee's up to 99 %) as well as with improved activities under standard thermal conditions. The results indicate that the catalytic performance is highly affected by the oxazoline and biarylphosphite substituents and the axial chirality of the biaryl moiety of the ligand. The Heck reactions were also performed under microwave irradiation conditions, allowing a considerably shorter reaction time (full conversion in minutes) maintaining the excellent regio- and enantioselectivities. 相似文献