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101.
Xiong X Xu W Eberlin LS Wiseman JM Fang X Jiang Y Huang Z Zhang Y Cooks RG Ouyang Z 《Journal of the American Society for Mass Spectrometry》2012,23(6):1147-1156
Data processing for three dimensional mass spectrometry (3D-MS) imaging was investigated, starting with a consideration of
the challenges in its practical implementation using a series of sections of a tissue volume. The technical issues related
to data reduction, 2D imaging data alignment, 3D visualization, and statistical data analysis were identified. Software solutions
for these tasks were developed using functions in MATLAB. Peak detection and peak alignment were applied to reduce the data
size, while retaining the mass accuracy. The main morphologic features of tissue sections were extracted using a classification
method for data alignment. Data insertion was performed to construct a 3D data set with spectral information that can be used
for generating 3D views and for data analysis. The imaging data previously obtained for a mouse brain using desorption electrospray
ionization mass spectrometry (DESI-MS) imaging have been used to test and demonstrate the new methodology. 相似文献
102.
Paul Wiseman Catherine A. Kennedy D. Gerrard Marangoni Ramamurthy Palepu 《Journal of solution chemistry》1998,27(3):217-233
A family of two-headed surfactants, the disodium 4-alkyl-3-sulfonatosuccinates, has been prepared by reacting maleic anhydride with the appropriate chain-length alcohol and subsequent addition of sodium bisulfite to the corresponding monoester. The properties of the micelles formed by these compounds in aqueous solution (aggregation numbers, degrees of counterion binding, and the cmc values) have been investigated as a function of temperature and surfactant chain length using viscosity, density, and conductance measurements. The critical micelle concentrations (cmc's) and the aggregation numbers appear to indicate that, in agreement with the earlier literature on other two-headed surfactants systems, these amphiphiles have higher cmc and lower aggregation numbers when compared to single-headed surfactants of comparable chain length. In addition, viscosity B coefficients and the thermodynamic parameters of activation of viscous flow have been determined. These results are interpreted in terms of the structure-making or -breaking properties of the surfactant amphiphiles below the cmc region. Finally, the thermodynamic properties of micelle formation have been estimated from the dependence of the cmc on the absolute temperature according to the charged pseudo-phase separation model of micelle formation. All these results are discussed in terms of how the addition of the second charged surfactant headgroup alters the micellar and solution properties of two-headed surfactants vs. their single-headed counterparts. 相似文献
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104.
Petersen NO Brown C Kaminski A Rocheleau J Srivastava M Wiseman PW 《Faraday discussions》1998,(111):289-305; discussion 331-43
Communication between cells invariably involves interactions of a signalling molecule with a receptor at the surface of the cell. Typically, the receptor is imbedded in the membrane and it is hypothesized that the binding of the signalling molecule causes a change in the state of aggregation of the receptor which, in turn, initiates a biochemical signal within the cell. Subsequently, many of the occupied receptors bind to membrane-associated structures, called coated pits, which invaginate and pinch off to form coated vesicles, thereby removing the receptors from the cell surface. The state of aggregation of membrane receptors is obviously in constant flux. Any useful approach to measuring the state of aggregation must, therefore, allow for dynamic measurements in living cells. It is possible to use fluorescently labelled signalling molecules or antibodies directed at the receptor of interest to visualize the receptor on the cell surface with a fluorescence microscope. By employing a laser confocal microscope, high resolution images can be produced in which the fluorescence intensity is quantitatively imaged as a function of position across the surface of the cell. Calculations of autocorrelation functions of these images provide direct and accurate measures of the density of fluorescent particles on the surface. Combined with the average intensity in the image, which reflects the total average number of molecules, it is possible to estimate the degree of aggregation of the receptor molecules. We refer to this analysis as image correlation spectroscopy (ICS). We show how ICS can be used to measure the density of several receptors on a variety of cells and how it can be used to measure the density of coated pits and the number of molecules per coated pit. We also show how the technique can be used to monitor fusion of virus particles to cell membranes. Further, we illustrate that, by calculating cross-correlation functions between pairs of images, we can extend the analysis to measurements of the distributions as a function of time, on the second timescale, as well as to measurements of the movement of the receptor aggregates on the surface. Finally, we illustrate that, by this approach, we can measure the extent of interaction between two different receptors as a function of time. This represents the most quantitative measurement of the extent of co-localization of receptors available and is independent of the spatial resolution of the confocal microscope. The theory of ICS and image cross-correlation spectroscopy (ICCS), focussing on the interpretation of the data in terms of the biological phenomenon being probed, is discussed. 相似文献
105.
Superparamagnetic clustering of data 总被引:2,自引:0,他引:2
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