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排序方式: 共有129条查询结果,搜索用时 15 毫秒
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An enantioselective two-stage off-line assay has been developed for the analysis of hydroxychloroquine and its three major metabolites in biological fluids. The first non-stereoselective stage of the assay (PRP-1 column) separates and quantitates parent drug and metabolites. Fractions containing hydroxychloroquine and each of the metabolites are collected manually, evaporated, reconstituted in mobile phase and re-injected onto an alpha 1-acid glycoprotein column to separate and determine proportions of individual enantiomers. Preliminary results from patients samples indicate that the disposition of hydroxychloroquine and its major metabolites is enantioselective. p6 相似文献
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Vojinović K McLachlan LJ Hinchley SL Rankin DW Mitzel NW 《Chemistry (Weinheim an der Bergstrasse, Germany)》2004,10(12):3033-3042
The simple silylhydrazines F(3)SiN(Me)NMe(2) (1), F(2)Si(N(Me)NMe(2))(2) (2), and F(3)SiN(SiMe(3))NMe(2) (3) have been prepared by reaction of SiF(4) with LiN(Me)NMe(2) and LiN(SiMe(3))NMe(2), while F(3)SiN(SnMe(3))NMe(2) (4) was prepared from SiF(4) and (Me(3)Sn)(2)NNMe(2) (5). The compounds were characterized by gas-phase IR and multinuclear NMR spectroscopy ((1)H, (13)C, (14/15)N, (19)F, (29)Si, (119)Sn), as well as by mass spectrometry. The crystal structures of compounds 1-5 were determined by X-ray crystallography. The structures of free molecules 1 and 3 were determined by gas-phase electron diffraction. The structures of 1, 2, and 4 were also determined by ab initio calculations at the MP2/6-311+G** level of theory. These structural studies constitute the first experimental proof for the presence of strong Si.N beta-donor-acceptor bonds between the SiF(3) and geminal NMe(2) groups in silylhydrazines. The strength of these non-classical Si.N interactions is strongly dependent on the nature of the substituent at the alpha-nitrogen atom of the SiNN unit, and has the order 3>4>1. The valence angles at these extremely deformed alpha-nitrogen atoms, and the Si.N distances are (crystal/gas): 1 104.2(1)/106.5(4) degrees, 2.438(1)/2.510(6) A; 3 83.6(1)/84.9(4) degrees, 2.102(1)/2.135(9) A; 4 89.6(1) degrees, 2.204(2) A. 相似文献
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Two oxidation waves are observed at mercury electrodes for tetraphenyllead in dichloromethane. The mechanisms of the oxidation processes have been investigated by dc and differential pulse polarography. The first wave is a broad two-electron step and represents the summation of a number of processes related to mercury exchange and halide abstraction. The exchange reactions are as follows: 2 Φ4Pb + Hg→2Φ3Pb+ + Φ2Hg+2e? 2 Φ3Pb+ + Hg→2Φ2Pb2+ + Φ2Hg+2e? Dichloroethane and HgCl2 are identified as products of controlled potential electrolysis experiments as well as Φ2Hg and Φ2PbCl2 implying that the coordinatively unsaturated Φ3Pb+ and/or Φ2Pb2+ react with the solvent dichloromethane and abstract chloride. The second oxidation process is the two electron step. Φ2Hg+Hg→2 ΦHg+ + 2e?Tetraalkyllead compounds (tetramethyl, tetraethyl, tetrabutyl) also give rise to related electrode processes at mercury electrodes and polarographic techniques may form the basis of a method for their analytical determination if separated chromatographically prior to detection. 相似文献
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We show that the decreased light absorption and the anomalous optical rotatory dispersion in helical polynucleotides and polypeptides may be interpreted purely as a local field effect. The electric field of the incident light wave is screened off from each residue by the induced electric dipoles in the others. Quantum-mechanical calculations based on time-dependent Hartree theory and this local field picture correspond precisely with the formulae derived in Tinoco's, Rhodes's, and Moffitt's exciton theories, provided that the Coulomb interactions are small. The degenerate exciton waves in our theory correspond to normal modes of a set of coupled oscillators, and the rotational strengths and oscillator strengths are conserved. There is no conflict between Tinoco's theory of hypochromism and the ones proposed by Bolton and Weiss and by Nesbet. One new conclusion is that the energy shifts accompanying hypochromism should not vary much when the exciton coupling changes from the strong to the weak coupling limits. 相似文献