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排序方式: 共有127条查询结果,搜索用时 15 毫秒
1.
Devendrapratap U Singh 《Tetrahedron letters》2004,45(24):4805-4807
Fe-exchanged montmorillonite K10 catalyzes a highly efficient reaction between sterically and electronically diverse sulfonamides and carboxylic acid anhydrides to furnish N-acylsulfonamides in excellent yield and high selectivity. The catalyst can also be reused several times. 相似文献
2.
V. A. Al'fonsov I. A. Litvinov O. N. Kataeva D. A. Pudovik S. A. Katsyuba 《Russian Chemical Bulletin》1995,44(10):1897-1899
X-Ray study of (diethyldithiocarbomoyl)diphenylthiophosphinate was carried out. AZ-conformation of the diethyldithiocarbomoyl ligand, which results in a short nonvalent intramolecular P...S contact (3.315 Å), is realized in the molecule. Steric hindrances in the molecule increase the P-S-C bond angle to 106.39°.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1978–1980, October, 1995.The work was financially supported by the International Science Foundation (Gram RH1 000). 相似文献
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4.
Anirban Kar 《Tetrahedron》2005,61(22):5297-5302
Starting from citraconic anhydride (13), a simple multistep (9-10 steps) synthesis of naturally occurring butyrolactones maculalactone A (3), maculalactone B (1), maculalactone C (2) and nostoclide I (4) have been described with good overall yields via dibenzylmaleic anhydride (20) and benzylisopropylmaleic anhydride (27). The two anhydrides 20 and 27 were prepared by SN2′ coupling reactions of appropriate Grignard reagents with dimethyl bromomethylfumarate (14), LiOH-induced hydrolysis of esters to acids, bromination of carbon-carbon double bond, in situ dehydration followed by dehydrobromination and chemoselective allylic substitution of bromoatom in disubstituted anhydrides 19 and 26 with appropriate Grignard reagents. The NaBH4 reduction of these anhydrides 20 and 27 furnished the desired lactones 21 and 29, respectively. The lactone 21 on Knoevenagel condensation with benzaldehyde, furnished maculalactone B (1), which on isomerization gave maculalactone C (2). Selective catalytic hydrogenation of 1 gave maculalactone A (3). The conversion of lactone 29 to nostoclide I (4) is known. 相似文献
5.
(C6H5)3MX2 (M = As, Sb; X = OCOCF3 and M = Sb, Bi; X = SO3F, SO3CF3) compounds prepared by the interaction of triphenylmetal(V) substrates with (CF3CO)2O, (CF3SO2)2O and (FSO2)2O have been characterized by molecular weight determination, elemental and spectroscopic (IR, 1H and 19F NMR, mass) analyses. 相似文献
6.
Günter Eichberger Herfried Griengl Willibald Paar 《Monatshefte für Chemie / Chemical Monthly》1986,117(4):545-551
Reaction of 3-methyl-1,3-oxazolidine with phthalic anhydride in chloroform leads to ring opening and higher oligomers2 are formed. These are cleaved by addition of protic solvents and 2-methylaminoethyl hydrogenphthalate3 a is obtained. Other 1,3-oxazolidines and succinic anhydride behave similarly.
Herrn Prof. Dr. Dr. h. c.Karl Kratzl mit den besten Wünschen zum 70. Geburtstag gewidmet. 相似文献
7.
Umar Farid Maria Luisa Aiello Prof. Stephen J. Connon 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(43):10074-10079
A new catalytic methodology was developed to promote an efficient one-pot kinetic resolution of racemic aldehydes with selectivity (s*) of up to 91 (99:1 d.r., >99 % ee) in a cycloaddition reaction with enolizable anhydrides to afford dihydroisocoumarin products (a core prevalent in natural products and molecules of medicinal interest) containing three contiguous stereocentres. 相似文献
8.
Dzmitry M. Zubrytski Gbor Zoltn Elek Margus Lopp Dzmitry G. Kananovich 《Molecules (Basel, Switzerland)》2021,26(1)
Oxidative fragmentation of tertiary cyclopropanols with phenyliodine(III) dicarboxylates in aprotic solvents (dichloromethane, chloroform, toluene) produces mixed anhydrides. The fragmentation reaction is especially facile with phenyliodine(III) reagents bearing electron-withdrawing carboxylate ligands (trifluoroacetyl, 2,4,6-trichlorobenzoyl, 3-nitrobenzoyl), and affords 95−98% yields of the corresponding mixed anhydride products. The latter can be straightforwardly applied for the acylation of various nitrogen, oxygen and sulfur-centered nucleophiles (primary and secondary amines, hydroxylamines, primary alcohols, phenols, thiols). Intramolecular acylation yielding macrocyclic lactones can also be performed. The developed transformation has bolstered the synthetic utility of cyclopropanols as pluripotent intermediates in diversity-oriented synthesis of bioactive natural products and their synthetic congeners. For example, it was successfully applied for the last-stage modification of a cyclic peptide to produce a precursor of a known histone deacetylase inhibitor. 相似文献
9.
K. Diemert G. Hein A. Janssen W. Kuchen 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1-4):339-356
Abstract Aminophosphine des Typs Rn P(NR′2)3-n (n= 2, 1, 0; R = Ph, c-Hex, (-)Men, t-Bu; R′= Me, Et, n-Bu) reagieren mit 2, 4-Bis(aryl)-1, 3, 2, 4-dithiadiphosphetan-2, 4-disulfiden (ArPS2)2(Ar: Ph, 4-Methoxyphenyl = An, Naphthyl, Thienyl) unter formaler Insertion monomerer {ArPS2)-Einheiten in eine oder in zwei der λ3-P—N-Bindung zu chiralen Organophosphorverbindungen Ar(R′2N)P(S)—S—PRn (NR′2)2-n(n = 2, 1, 0) und [Ar(R′2N)P(S)—]2PR2(NR′2)1-n (n = 1.0). In diesen werden bei Raumtemperatur bevorzugt die λ3—P—N—und λ3—P—S-Bindungen durch H2O oder Methanol unter Bildung von Produktgemischen solvolysiert. Mit Chlorwasserstoff bildet sich aus An(Et2N)P(S)—S—PPh(NEt2) das An(Et2 N)P(S)—S—PPh(C1). Addition von Schwefel führt zu Ar(R′2N)P(S)—S—P(S)Rn (NR′)2-n (n=2, 1). Die Stereoisomerenbildung der neuen Verbindungen wird besprochen und ihre Struktur sowie die Zusammensetzung der Reaktionsmischungen aus den 31P-Spektren hergeleitet. Aminophosphines Rn P(NR′2)3-n (n = 2, 1, 0; R = Ph. c-Hex, (-)Men, t-Bu; R′= Me, Et, n-Bu) react with 2, 4-Bis(aryl)-1, 3, 2, 4-dithiadiphosphetane-2, 4-disulfides (ArPS2)2 (Ar: Ph, 4-Methoxyphenyl = An, Naphthyl, Thienyl) under formal insertion of monomeric {ArPS2)-units in one or in two of the λ3-P—N-bonds to yield chiral organophosphorus compounds Ar(R′2N)P(S)—S—]2PRn (NR′2)2 (n = 2, 1, 0) and [Ar(R′2N)P(S)—S—]2 PR2 (NR′2)2-n (n = 1, 0). At room temperature chiefly the A—P—N and A3—P—S-bonds in these products are solvolyzed by H, O or methanol with formation of mixtures of compounds. With hydrogen chloride An(Et2N)P(S)—S—PPh(NEt2) is converted into An(Et2N)P(S)—S—PPh(Cl). Addition of sulfur yields Ar(R′2N)P(S)—S P(S)Rn (NR′2)2-n (n = 2, 1). Stereoisomerism of the new compounds is discussed and their structures as well as the composition of reaction mixtures are deduced from “P-NMR-spectra”. 相似文献
10.
Chengye Yuan Shusen Li Zhiyi Cheng 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1-2):95-102
Abstract The mass spectra of 2-alkyl-2-oxo-1,3,2-dioxa-phosphorinane and-phosphepane showed that the ring opening was in competition with the cleavage of the P[sbnd]C bond. According to the fragmentation pathway, which was dependent on the structure of exocyclic substituents on phosphorus, the 2-alkyl-2-oxo-1,3,2-di-oxa-phosphorinanes can be classified in two categories. The main process in category A was the ring opening and/or C[sbnd]C bond cleavage. While in category B the cleavage of P[sbnd]C bond was predominant. However, for 2-alkyl-2-oxo-1,3,2-dioxa-phosphepane. no matter how the structure of 2-alkyl group was, the ring opening was a dominant process. 相似文献