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91.
92.
93.
A 3,4‐trans‐Fused Cyclic Protecting Group Facilitates α‐Selective Catalytic Synthesis of 2‐Deoxyglycosides
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Dr. Edward I. Balmond Dr. David Benito‐Alifonso Dr. Diane M. Coe Prof. Roger W. Alder Dr. Eoghan M. McGarrigle Dr. M. Carmen Galan 《Angewandte Chemie (International ed. in English)》2014,53(31):8190-8194
A practical approach has been developed to convert glucals and rhamnals into disaccharides or glycoconjugates with high α‐selectivity and yields (77–97 %) using a trans‐fused cyclic 3,4‐O‐disiloxane protecting group and TsOH?H2O (1 mol %) as a catalyst. Control of the anomeric selectivity arises from conformational locking of the intermediate oxacarbenium cation. Glucals outperform rhamnals because the C6 side‐chain conformation augments the selectivity. 相似文献
94.
Pelevin N. A. Markovich Yu. D. Nazarov G. V. Galan S. E. Kudryavtseva T. N. Brylev M. I. 《Russian Chemical Bulletin》2011,60(3):590-592
The kinetic regularities of cyclization of 2′- and 4′-substituted diphenylamine-2-carboxylic acids in sulfuric acid were determined.
The rate of cyclization of diphenylamine-2-carboxylic acids is linearly dependent on the nature of substituents in the meta-position relative to the reaction site in accordance with the two-parameter Hammett equation. 相似文献
95.
96.
Galan BR Schöffel J Linehan JC Seu C Appel AM Roberts JA Helm ML Kilgore UJ Yang JY DuBois DL Kubiak CP 《Journal of the American Chemical Society》2011,133(32):12767-12779
[Ni(P(R)(2)N(R')(2))(2)(CH(3)CN)](2+) complexes with R = Ph, R' = 4-MeOPh or R = Cy, R' = Ph , and a mixed-ligand [Ni(P(R)(2)N(R')(2))(P(R'(2))N(R'(2)))(CH(3)CN)](2+) with R = Cy, R' = Ph, R' = Ph, have been synthesized and characterized by single-crystal X-ray crystallography. These and previously reported complexes are shown to be electrocatalysts for the oxidation of formate in solution to produce CO(2), protons, and electrons, with rates that are first-order in catalyst and formate at formate concentrations below ~0.04 M (34 equiv). At concentrations above ~0.06 M formate (52 equiv), catalytic rates become nearly independent of formate concentration. For the catalysts studied, maximum observed turnover frequencies vary from <1.1 to 15.8 s(-1) at room temperature, which are the highest rates yet reported for formate oxidation by homogeneous catalysts. These catalysts are the only base-metal electrocatalysts as well as the only homogeneous electrocatalysts reported to date for the oxidation of formate. An acetate complex demonstrating an η(1)-OC(O)CH(3) binding mode to nickel has also been synthesized and characterized by single-crystal X-ray crystallography. Based on this structure and the electrochemical and spectroscopic data, a mechanistic scheme for electrocatalytic formate oxidation is proposed which involves formate binding followed by a rate-limiting proton and two-electron transfer step accompanied by CO(2) liberation. The pendant amines have been demonstrated to be essential for electrocatalysis, as no activity toward formate oxidation was observed for the similar [Ni(depe)(2)](2+) (depe = 1,2-bis(diethylphosphino)ethane) complex. 相似文献
97.
Lee Cameron Aswin Rajagopalan Laura Abad Galan Rene Z.H. Phe Brian W. Skelton Massimiliano Massi 《Supramolecular chemistry》2019,31(7):466-472
The tetrazole-functionalised calixdiquinone 5,17-di-tert-butyl-26,28-bis-(1H-tetrazole-5-ylmethoxy)-calix[4]-25,27-diquinone Q was synthesised by chemical oxidation of the bis-tetrazole calix[4]arene precursor using PbO2/HClO4. The single crystal X-ray structure determination of Q confirmed the structure and showed binding of a water molecule in the solid state. Chemical reduction of Q to the dihydroquinone QR was achieved using N,N-diethylhydroxylamine. Comparison of the solution phase photophysical properties of Q or QR in the presence of terbium ions showed significant excitation only with QR, suggesting redox switching of the photophysical response may be possible with this or similar receptor. 相似文献
98.
Recently in Romania the use of high power ultrasonics in electrically conductive solid media has increased. Consequently more severe conditions have been imposed on inductive transducers regarding their sensitivity and selectivity for measuring acoustic field amplitudes. In view of this the authors carried out theoretical and experimental studies on inductive transducers. Parameters that influence the back emf in an idealized physical model, can be particularized for every practical case. By reducing the magnetic reluctance of the air closed field lines, transducers with a sensitivity of about 400 mV/μm have been built. These transducers may possibly be used at higher frequencies. Also, selective transducers for longitudinal and transverse vibrations were made by altering the geometry and position of their constituent elements. 相似文献
99.
P. Galan 《Czechoslovak Journal of Physics》1972,22(6):468-475
The ground states of odd-odd nuclei160Tb,182Ta and182Re and the isomeric state182mRe are interpreted in terms of the Nilsson nuclear model. The conclusions about the structure of these states were drawn from the experimental results obtained in the study of their decay to the neighbouring even-even nuclei as well from the systematics of single-particle proton and neutron states in neighbouring odd-mass nuclei. The agreement between experimental and calculated values of the moments of inertia of these states is demonstrated.Dúbravská cesta, Bratislava, Czechoslovakia. 相似文献
100.
Galan MC Venot AP Glushka J Imberty A Boons GJ 《Organic & biomolecular chemistry》2003,1(22):3891-3899
N-Acetyllactosamine derivative 4, which has a methylene amide tether between C-6 and C-2', was enzymatically glycosylated using rat liver alpha-2,6-sialyltransferase (ST6GalI) or recombinant human fucosyltransferase V (FucT-V) to give conformationally constrained trisaccharides 5 and 6, respectively. The methylene amide linker of 4 was installed by a two-step procedure, which involved acylation of a C-6 amino function of a LacNAc derivative with chloroacetic anhydride followed by macrocyclization by nucleophilic displacement of the chloride by a C-2' hydroxyl. The conformational properties of 4 were determined by a combination of NOE and trans-glycosidic heteronuclear coupling constant measurements and molecular mechanics simulations and these studies established that the glycosidic linkage of 4 is conformationally constrained and resides in only one of the several energy minima accessible to LacNAc. The apparent kinetic parameters of transfer to LacNAc and conformationally constrained saccharides 3 and 4 indicates that fucosyltransferase V recognize LacNAc in its A-conformer whereas alpha-2,6-sialyltransferase recognizes the B-conformer of LacNAc. 相似文献