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Roger D. Farrant John C. Hollerton Sean M. Lynn Stefano Provera Philip J. Sidebottom Richard J. Upton 《Magnetic resonance in chemistry : MRC》2010,48(10):753-762
We have developed QUANTAS (QUANTification by Artificial Signal), which is a software‐based protocol for concentration measurement by NMR. QUANTAS is an absolute intensity external standard method for quantification by NMR that compensates for various experimental parameters. It is applicable to all nuclei and modern spectrometers. QUANTAS is demonstrated here for 1H and 19F NMR, enabling heteronuclear integrals to be compared. It can be applied using fixed probe tuning, matching and pulse length, for samples with the same effective loading on the probe coil as the appropriate reference spectrum. Otherwise, an optimised tuning and matching approach is adopted for every sample together with explicit PULCON (PUlse Length‐based CONcentration measurements) absolute intensity corrections. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
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Alexey Suvorov David S. Coburn Alessandro Cunsolo Jeffrey W. Keister Mary H. Upton Yong Q. Cai 《Journal of synchrotron radiation》2014,21(3):473-478
The L‐shaped laterally graded multilayer mirror is a vital part of the ultrahigh‐energy and momentum‐resolution inelastic X‐ray scattering spectrometer at the National Synchrotron Light Source II. This mirror was designed and implemented as a two‐dimensional collimating optic for the analyzer system. Its performance was characterized using a secondary large‐divergence source at the 30‐ID beamline of the Advanced Photon Source, which yielded an integrated reflectivity of 47% and a collimated beam divergence of 78 µrad with a source size of 10 µm. Numerical simulations of the mirror performance in tandem with the analyzer crystal optics provided details on the acceptance sample volume in forward scattering and defined the technical requirements on the mirror stability and positioning precision. It was shown that the mirror spatial and angular stability must be in the range <8.4 µm and <21.4 µrad, respectively, for reliable operation of the analyzer. 相似文献
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The isotope content of ethane formed by pyrolysis of the complex (Me2PPh)2PtMe3I and its deuterated derivatives shows that the reaction is both intramolecular and first order with respect to substrate and gives the activation parameter ΔH3 = 129 ± 5 kJ · mol?1. 相似文献
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Jack E. Baldwin Timothy D. W. Claridge Andrew J. Culshaw Florian A. Heupel Victor Lee David R. Spring Roger C. Whitehead Robert J. Boughtflower Ian M. Mutton Richard J. Upton 《Angewandte Chemie (International ed. in English)》1998,37(19):2661-2663
The biomimetic synthesis of a pentacyclic alkaloid (keramaphidin B, 1 ), an intermediate in the biogenetic pathway to the manzamine alkaloids, has been achieved. Compound 1 was formed by an intramolecular Diels–Alder reaction of macrocycle 2 in buffer followed by reduction with NaBH4. This reaction provides the first direct expeimental evidence for the authors' biosynthetic hypothesis. 相似文献
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Sree V. Chintapalli Boon K. Yew Christopher J. R. Illingworth Graham J. G. Upton Philip J. Reeves Kevin E. B. Parkes Christopher R. Snell Christopher A. Reynolds 《Journal of computational chemistry》2010,31(15):2689-2701
Nonoverlapping closed loops of around 25–35 amino acids formed via nonlocal interactions at the loop ends have been proposed as an important unit of protein structure. This hypothesis is significant as such short loops can fold quickly and so would not be bound by the Leventhal paradox, giving insight into the possible nature of the funnel in protein folding. Previously, these closed loops have been identified either by sequence analysis (conservation and autocorrelation) or studies of the geometry of individual proteins. Given the potential significance of the closed loop hypothesis, we have explored a new strategy for determining closed loops from the insertions identified by the structural alignment of proteins sharing the same overall fold. We determined the locations of the closed loops in 37 pairs of proteins and obtained excellent agreement with previously published closed loops. The relevance of NMR structures to closed loop determination is briefly discussed. For cytochrome c, cytochrome b562 and triosephophate isomerase, independent folding units have been determined on the basis of hydrogen exchange experiments and misincorporation proton‐alkyl exchange experiments. The correspondence between these experimentally derived foldons and the theoretically derived closed loops indicates that the closed loop hypothesis may provide a useful framework for analyzing such experimental data. © 2010 Wiley Periodicals, Inc. J Comput Chem, 2010 相似文献