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31.
Jordan Geller Ivor Wharf Francine Blanger‐Garipy Anne‐Marie Lebuis Ian S. Butler Denis F. R. Gilson 《Acta Crystallographica. Section C, Structural Chemistry》2002,58(9):m466-m468
Chlorotris(2,4,6‐trimethylphenyl)tin(IV), crystallizes from ethanol as solvent‐free needles, [Sn(C9H11)3Cl], (I), and as the hemisolvate, [Sn(C9H11)3Cl]·0.5C2H6O, (II). The asymmetric unit in (I) has three independent molecules, whereas in (II), there are two [Sn(C9H11)3Cl] molecules together with one ethanol molecule. In the unit cell of (II), the ethanol molecules lie in channels between stacks of (Mes)3SnCl molecules (Mes is 2,4,6‐trimethylphenyl) and each ethanol molecule is disordered (0.50:0.50) over two positions. A comparison of the structures of the title compounds and other (Mes)3SnX (X = F, Br or I) systems with those of the triphenyltin analogues shows that the steric requirements of the o‐CH3 groups are met by a flattening of the SnC3 skeleton and increases in the average Sn—X and Sn—C values. Comparing Sn—X data for (Mes)3SnX (X = F, Cl, Br or I) systems with values for the tris(o‐methoxyphenyl)tin analogues suggests that the Sn—F distance of 1.961 Å in (Mes)3SnF may well be characteristic of sterically unhindered four‐coordinate Ar3SnF systems. 相似文献
32.
Dieter Seebach Miguel A. Maestro Michael Sefkow Axel Neidlein Francine Sternleld Geo Adam Thimo Sommerfeld 《Helvetica chimica acta》1991,74(8):2112-2118
The antibiotic myxovirescine M2 was synthesized from seven building blocks ( 1 – 7 , Scheme 1), with the following chiral starting materials being employed: (S)-malic acid, (+)-D -ribonolactone, (S)-2-(hydroxymethyl)butanoate, and (2R,4S)-5-hydroxy-2,4-dimethylpenLanoate. Three new nucleophilic reagents, 8 – 10 , for C-C bond formation have been used. The key steps of the synthesis are: a Suzuki coupling between an alkyl borane and a vinyl bromide ( 4 + 12e → 13 ), a Julia olefinalion ( 14 + 17 → 18 ), and a Yamaguchi macrolactonizalion to form the 28-membered lactone ( 18 → 19 ), This extremely convergenl synthetic approach will allow the preparation of a number of the 31 known myxovirescine molecules. 相似文献
33.
Roberta Pinalli Francine F. Nachtigall Franco Ugozzoli Enrico Dalcanale 《Angewandte Chemie (International ed. in English)》1999,38(16):2377-2380
Cooperativity between different noncovalent host–guest interactions is the key for the successful generation of selective supramolecular sensors. A new class of cavitands capable of synergistic CH⋅⋅⋅π interactions and hydrogen bonding has been designed and exploited for the detection of alcohol vapors using mass transducers (see schematic representation). 相似文献
34.
Joë l Merker Francine Meylan 《Proceedings of the American Mathematical Society》1999,127(4):1097-1102
In this article, we prove that smooth CR diffeomorphisms between two real analytic holomorphically nondegenerate hypersurfaces, one of which is rigid and polynomial, extend to be locally biholomorphic. It turns out that the result can be generalized to not totally degenerate mappings, in the sense of Baouendi and Rothschild.
35.
Bernard Boutevin Francine Guida‐Pietrasanta Amde Ratsimihety 《Journal of polymer science. Part A, Polymer chemistry》2000,38(20):3722-3728
The synthesis of photocrosslinkable fluorinated polydimethylsiloxanes was achieved through direct hydrosilylation with copoly(dimethyl)(methyl‐hydrogen) siloxane. First, the hydrosilylation of a fluorinated olefin allowed the introduction of a fluorinated group onto the polysiloxane. Then, a second hydrosilylation of allyl methyl methacrylate led to the polysiloxane bearing both fluorinated and photocrosslinkable groups. This method, compared with a previous method of copolycondensation, is shown to be easier and more efficient. All the new products synthesized were characterized by IR, 1H NMR, 19F NMR, and 29Si NMR. A formulation containing the fluorosilicone was crosslinked after being coated on a mesoporous membrane and was evaluated as a vapor permeation membrane. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 3722–3728, 2000 相似文献
36.
A geometric model for active contours in image processing 总被引:58,自引:0,他引:58
Summary We propose a new model for active contours based on a geometric partial differential equation. Our model is intrinsec, stable (satisfies the maximum principle) and permits a rigorous mathematical analysis. It enables us to extract smooth shapes (we cannot retrieve angles) and it can be adapted to find several contours simultaneously. Moreover, as a consequence of the stability, we can design robust algorithms which can be engineed with no parameters in applications. Numerical experiments are presented. 相似文献
37.
Hassane Assaaoudi Ian S. Butler Janusz Kozinski Francine Bélanger-Gariépy 《Journal of chemical crystallography》2005,35(1):1-4
Abstract
Index abstracts 相似文献38.
Francine Abeles 《Historia Mathematica》1976,3(2):183-184
In this note, we examine a Carrollian treatment of the base of a number system as it appears in Alice in Wonderland. 相似文献
39.
40.
Monnier V Libot F Aitken DJ Husson HP Lesage D Fournier F Tabet JC 《Rapid communications in mass spectrometry : RCM》2002,16(5):447-452
The title compound types are structural isomers. The absence of literature studies dealing with the mass spectrometric gas-phase behavior of such compounds prompted a search for the best conditions for differentiation between the two prototype examples (R,R)-5,10-diphenyl-1,6-diaza-3,8-dioxabi-cyclo[4.4.1]undecane and N,N'-methylenebis[(R)-4-phenyloxazolidine]. Attempts to differentiate between the isomers by NMR were inconclusive and X-ray crystallography had to be used. The best mass spectrometric results were obtained using gas-phase ionization techniques, particularly chemical ionization, whereby protonated molecules were observed. The fragmentation pathways were elucidated from MS/MS studies and from experiments performed on hexadeuterated samples of each compound. 相似文献