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71.
72.
Ourida Saidi A. John Blacker Stephen P. Marsden Robert J. Watson 《Tetrahedron letters》2010,51(44):5804-5806
Amines have been formylated using aqueous formaldehyde or paraformaldehyde and the iridium catalyst [Cp∗IrI2]2. Paraformaldehyde acts as both a formylating agent and an oxidant. 相似文献
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The perfluoronitrosocycloalkanes, heptafluoronitrosocyclobutane and nonafluoronitrosocyclopentane, are convenient precursors to a family of new perfluorocycloalkyl(aryl) diazenes. With aniline and o-aminobenzamide, FNNH and FNNC(O)NH2 (x = 2,3) are formed. Additionally, heptafluoronitrosocyclobutane gives FNNF and FNNNH2 with 2,3,5,6-tetrafluoroaniline and o-phenylenediamine 相似文献
76.
A linear synthesis of the glucuronide metabolite of ABT-751 was replaced with a convergent synthesis that features direct glycosidic coupling between the aglycone and a trichloroacetimidate glucuronyl donor. Structural elucidation of a unique and unexpected difluoroboron complex of the desired glycosidic coupling product along with optimization of the synthetic steps is described. 相似文献
77.
Stable isotope methods are potentially quite useful for validating natural or enhanced mineral degradation of contaminants. For this reason, a continuous flow gas chromatograph (GC), isotope ratio mass spectrometer (IRMS) has been coupled with a quadrupole mass selective detector (MSD) to allow simultaneous mass spectral and stable carbon isotope ratio data to be obtained from a single chromatographic analysis. This allows the target contaminant and any extra-cellular degradation intermediates to be both qualified and quantified. Previously acceptable limits of precision (0.3 parts per mil) are undesirable given the small fractionation observed during aerobic degradation. To further understand the fate of organic contaminants and to gain information about the metabolic degradative pathway employed by a microorganism, routine isotopic analyses on a range of analytes have been performed. Quantities of sample producing mass-44 ion beam signal (I(44)) of 2 x 10(-10) to 1 x 10(-8) A were analysed. When the IRMS was tuned for high sensitivity, ion source nonlinearities were overcome by peak height correction from an algorithm that was produced using known isotopic standards of varying concentrations. This led to sample accuracy of <0.01 per thousand and sample precision of 0.1 per thousand. Copyright 1999 John Wiley & Sons, Ltd. 相似文献
78.
KM Clauwaert Van Bocxlaer JF HJ Major JA Claereboudt WE Lambert Van den Eeckhout EM Van Peteghem CH De Leenheer AP 《Rapid communications in mass spectrometry : RCM》1999,13(14):1540-1545
This paper describes the investigation of the potential of a quadrupole orthogonal acceleration time-of-flight mass spectrometer (Q-TOF) equipped with an atmospheric pressure ionisation interface for quantitative measurements of small molecules separated by reversed phase liquid chromatography. To this end, the detection limits and linear dynamic range in particular were studied in an LC/MS/MS experiment using 3,4-methylenedioxymethamphetamine standards and 3,4-methylenedioxyethylamphetamine for internal standardisation. In a second phase, the experiment was repeated with real biological extracts (whole blood, serum, and vitreous humour). A calibration for 3,4-methylenedioxymethamphetamine and its metabolite 3,4-methylenedioxyamphetamine was prepared in each of these matrices again using 3,4-methylenedioxyethylamphetamine as internal standard. The resulting quantitative data were compared with those obtained by liquid chromatography with fluorescence detection for the same extracts. The Q-TOF results revealed excellent sensitivity and a linear dynamic range of nearly four decades (2-10 000 pg on-column, r(2) = 0.9998, 1/x weighting). Furthermore, all the calibration curves prepared in biological material were superimposable, LC/MS/MS and LC-fluorescence, and the quantitative results for actual samples compared very favourably. It was concluded that the Q-TOF achieves a linear dynamic range for quantitative LC/MS/MS work exceeding that of fluorescence detection and at much better absolute sensitivity. Copyright 1999 John Wiley & Sons, Ltd. 相似文献
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Marco Castrillón López Jerrold E. Marsden 《Annals of Global Analysis and Geometry》2008,34(3):263-285
Reduction for field theories with symmetry can be done either covariantly—that is, on spacetime—or dynamically—that is, after
spacetime is split into space and time. The purpose of this article is to show that these two reduction procedures are, in
an appropriate sense, equivalent for a class of field theories whose fields take values in a principal bundle. One can think
of this class of field theories as including examples such as a “sea of rigid bodies” with and appropriate interbody coupling
potential. 相似文献