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1.
《Tetrahedron》2003,59(34):6415-6422
The Nuclear Independent Chemical Shift of each ring, as a criterion of aromaticity, is used to explain the stability order of benzopyrrole, benzofuran and benzothiophene, and their isomers. The results indicate that the benzene ring is aromatic in all the systems. The five-membered rings of benzopyrrole, benzofuran and benzothiophene are also aromatic, whereas those of isobenzopyrrole, isobenzofuran and isobenzothiophene are non-aromatic. This could be an explanation of the stability of the former molecules. The molecular orbitals and the condensed Fukui functions derived from the electronic structure calculations are also reported. These reactivity indices explain the expected electrophilic substitution of these compounds. The theoretical structure, ionization energies, order of aromaticity, stability and reactivity are in good agreement with the experimental results. The usefulness of this approach to determine the reactivity is discussed since their stability and reactivity may be understood. The reactivity indices are useful to explain and confirm the experimental information, and for molecules with unknown reactive behavior, this approach could help to predict some of the reactions. 相似文献
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3.
Ana M. Piloto 《Tetrahedron》2006,62(39):9258-9267
Four carboxylic fused furans are presented as new fluorescent labels for the amino and hydroxyl functions of organic molecules. Various representative l-amino acids were chosen as models, labelled at their N-terminus and also at their side-chain. Fluorescent derivatives were obtained in high yields, and their absorption and emission properties were studied. 相似文献
4.
《Magnetic resonance in chemistry : MRC》2003,41(12):975-982
The reaction of 2,4‐pentanedione ( 1 ) with (R)‐(—)‐2‐phenylglycine methyl ester ( 2 ), (R)‐(—)‐2‐phenylglycinol ( 3 ) and the proteinogenic amino acids (2S,3R)‐(—)‐2‐amino‐3‐hydroxybutyric acid (L ‐threonine) ( 4 ) and (R)‐(—)‐2‐amino‐3‐mercaptopropionic acid (L ‐cysteine) ( 5 ) methyl esters was investigated. The corresponding enamines 6 , 7 and 8 were isolated and characterized spectroscopically whereas 9 , which is unstable, was transformed in situ into 13 . Treatment of 7 , 8 and 9 with boron trifluoride etherate afforded the new [1,4]oxazepines 10 , 11 and [1,4]thiazepine ( 12 ) as their BF3O? salts. The structures of the enamines and their corresponding seven‐membered heterocycles were assessed by 1D and 2D NMR spectroscopy. Variable‐temperature experiments revealed different molecular mobility behavior among these heterocycles. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
5.
Reaction of diethoxyphosphorylimine of methyl trifluoropyruvate with 1,3-C,N-and-N,N-binucleophiles led to a variety of N-phosphorylated fluorine-containing heterocycles, including the fused ones.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2176–2178, November, 2007. 相似文献
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M. G. Voronkov L. I. Larina Yu. I. Bolgova O. M. Trofimova N. F. Chernov V. A. Pestunovich 《Chemistry of Heterocyclic Compounds》2006,42(12):1585-1591
The 1H, 13C, 15N, and 29Si NMR, IR, and UV spectra of N-(1-silatranylmethyl) and N-(trimethoxysilylmethyl) derivatives of nitrogen heterocycles have
been studied. The dependence and interrelation of the chemical shifts of 29Si and 15N nuclei of the silatranyl group in the spectra of N-(1-silatranylmethyl)-substituted nitrogen heterocycles are determined
by the nature of the heterocyclic system.
__________
Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1857–1865, December, 2006. 相似文献
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Nilo Zanatta Darlene C. Flores Claudia C. Madruga Alex F.C. Flores Helio G. Bonacorso Marcos A.P. Martins 《Tetrahedron letters》2006,47(4):573-576
This work reports a two-step synthetic strategy to obtain a series of 6-methylenesubstituted-4-trichloromethyl-2-methylsulfanylpyrimidines from the cyclization of 5-bromo-4-methoxy-1,1,1-trichloro-pent-3-en-2-ones with 2-methyl-2-pseudothiourea sulfate, followed by nucleophilic substitution of 6-bromomethyl-4-trichloromethyl-2-methylsulfanylpyrimidine with a series of nucleophiles. Alternative strategies to obtain 6-halomethyl-4-trichloro[fluoro]methyl-2-methylsulfanyl pyrimidines have been addressed. 相似文献