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71.
A straightforward synthesis of 8-azabicyclo[3.2.1]octane-1-carboxylic acid, a new proline analogue with a bicyclic structure, is described. The procedure makes use of readily available starting materials and involves simple, high-yielding transformations. 相似文献
72.
Stephen C. Bergmeier Steven J. Katz Junfeng Huang Howard McPherson Patrick J. Donoghue Damon D. Reed 《Tetrahedron letters》2004,45(26):5011-5014
We have found that aziridines will react with a variety of π-nucleophiles in intramolecular cyclization reactions to produce nitrogen containing core structures found in a variety of bioactive molecules. These cyclizations are more general and facile than corresponding intermolecular reactions. We have examined the effects of ring size, π-nucleophile identity and substitution on this reaction. 相似文献
73.
Divya Agrawal 《Tetrahedron letters》2006,47(43):7615-7618
A concise and enantiospecific route to the 2,6-dioxabicyclo[3.3.0]octan-3-one ring system from commercially available (R)-(+)- and (S)-(−)-glycidols is described. The key features involve ring closing metathesis to construct the 7-substituted-4,5-dehydro-2-oxepanone and its base-catalyzed single-step rearrangement into the 2,6-dioxabicyclo[3.3.0]octan-3-one skeleton. Using this strategy, formal total syntheses of (7R)-cis-Hagen’s gland lactones and (+)- and (−)-trans-kumausynes have been achieved. 相似文献
74.
As shown by synthesis and enantioselective gas chromatography, males and females of the caddisfly species Potamophylax latipennis and Potamophylax cingulatus produce (1R,3S,5S,7S)-1-ethyl-3,5,7-trimethyl-2,8-dioxabicyclo[3.2.1]octane, while Glyphotaelius pellucidus produces 1,3-diethyl-4,6-dimethyl-2,7-dioxabicyclo[2.2.1]heptane, having either the (1S,3S,4R,6S) or (1R,3R,4S,6S)-configuration. As shown by electrophysiological investigations, the compounds are perceived by the antennae of both sexes. 相似文献
75.
Jubi John 《Tetrahedron letters》2007,48(40):7225-7227
Azabicyclic olefins undergo facile palladium-catalyzed ring opening with organoindium reagents affording trans-3,4-disubstituted hydrazinocyclopentenes in good to excellent yields. 相似文献
76.
Xiao-jun Wang Li Zhang Yibo Xu Dhileepkumar Krishnamurthy Richard Varsolona Laurence Nummy Sherry Shen Rogelio P. Frutos Denis Byrne J.C. Chung Vittorio Farina Chris H. Senanayake 《Tetrahedron letters》2005,46(2):273-276
An efficient and chromatography-free approach for synthesis of a new class of LFA-1 inhibitors was developed. A copper(I) chloride-promoted intramolecular cyclization of thiohydantoins 7a-b serves as a key step to highly functionalized bicyclic guanidines 5a-b, that were subsequently converted to 1H-imidazo[1,2-a]imidazol-2-one LFA-1 inhibitors. This process has been successfully implemented in the pilot plant to produce multikilogram quantities of LFA-1 inhibitors such as 1a-b. 相似文献
77.
Ashim Roy 《Tetrahedron letters》2004,45(30):5811-5814
The [3+2] intramolecular nitrone cycloaddition (INC) reaction on appropriately designed olefinic nitrones derived from d-glucose, having the nitrone at C-1 and α,β-unsaturated ester functionalities at C-5 of the sugar backbone, afforded the isoxazolidine fused carbocycles 11-13, which were subsequently transformed into the chiral, tetrahydroxylated cis-azabicyclo[3.3.0]octanones 14-18 in good yields. 相似文献
78.
Dr. Yuyan Zhang Dr. Sami El Sayed Dr. Liqun Kang M. Sc. Matthew Sanger Prof. Dr. Thomas Wiegand Prof. Dr. Philip G. Jessop Prof. Dr. Serena DeBeer Dr. Alexis Bordet Prof. Dr. Walter Leitner 《Angewandte Chemie (International ed. in English)》2023,62(48):e202311427
Ruthenium nanoparticles (NPs) immobilized on an amine-functionalized polymer-grafted silica support act as adaptive catalysts for the hydrogenation of bicyclic heteroaromatics. Whereas full hydrogenation of benzofuran and quinoline derivatives is achieved under pure H2, introducing CO2 into the H2 gas phase leads to an effective shutdown of the arene hydrogenation while preserving the activity for the hydrogenation of the heteroaromatic part. The selectivity switch originates from the generation of ammonium formate species on the surface of the materials by catalytic hydrogenation of CO2. The CO2 hydrogenation is fully reversible, resulting in a robust and rapid switch between the two states of the catalyst adapting its performance in response to the feed gas composition. A variety of benzofuran and quinoline derivatives were hydrogenated to fully or partially saturated products in high selectivity and yields simply by altering the composition of the feed gas from H2 to H2/CO2. The adaptive catalytic system thus provides controlled access to valuable products using a single catalyst rather than two specific and distinct catalysts with static reactivity. 相似文献
79.
4-Aryl/alkyl-6-methyl-3,4-dihydropyrimidin-2(1H)-one ester derivatives readily undergo metalation at the C6 methyl (vinylogous ester) position along with two acidic NHs upon treatment with n-butyllithium at −10 °C. The trianion of DHPMs thus obtained react smoothly with various terminal dibromoalkanes to afford N1, C6-linked bicyclic DHPM derivatives, which represent key structural features of the medicinally potent marine alkaloids such as batzelladine A and crambescin A. 相似文献
80.
Carles Isart 《Tetrahedron letters》2008,49(37):5414-5418
Seebach’s proline-derived oxazolidinone 2d overcomes (S)-proline and is at least as efficient as (S)-5-(pyrrolidin-2-yl)tetrazole in several organocatalytic aldol reactions examined. A quick exchange takes place between 2d and carbonyl compounds that gives new bicyclic oxazolidinones, in equilibrium with the very minor active species (enamines). Maximum yields of the aldols (β-hydroxy ketones) were achieved after 1-4 h when, with proline, they are attained after 30-48 h. 相似文献