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排序方式: 共有112条查询结果,搜索用时 312 毫秒
101.
David McDonnell Brendan Redmond Deirdre M D'Arcy Anne Marie Healy Owen I Corrigan 《PAMM》2009,9(1):691-692
This paper applies boundary layer theory to the process of drug dissolution in the USP 24, Type 2 Apparatus. The mass transfer rate from the top flat surface of a compact in various positions within the device is evaluated by means of a Pohlhausen integral method. (© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
102.
103.
McDonnell MJ Stacey JP Webster SC Home JP Ramos A Lucas DM Stacey DN Steane AM 《Physical review letters》2004,93(15):153601
We propose and demonstrate experimentally the discrimination between two spin states of an atom purely on the basis of their angular momentum. The discrimination relies on angular momentum selection rules and does not require magnetic effects such as a magnetic dipole moment of the atom or an applied magnetic field. The central ingredient is to prevent by coherent population trapping an optical pumping process which would otherwise relax the spin state before a detectable signal could be obtained. We detected the presence or absence of a single quantum (h) of angular momentum in a trapped calcium ion in a single observation with success probability 0.86. As a practical technique, the method can be applied to read out some types of quantum computer. 相似文献
104.
Peaks in the secondary emission spectra not associated with Auger effects have been observed in various metals (particularly copper and cobalt). These peaks are suppressed at elevated temperature and appear to have amplitudes which are unique functions of temperature. They are characteristic of well ordered, and, particularly, clean surfaces, and are interpreted in terms of the diffraction of the emitted secondary electrons. 相似文献
105.
A pair of substituted oxetane mass spectral decompositions exhibit regioselective ring cracking, and single and double hydrogen rearrangement cleavages involving substituent methyl groups. Analysis of ion abundances as a function of ionizing energy provides estimates of relative activation energies and frequency factors for these fragmentations. 相似文献
106.
Taban IM Altelaar AF van der Burgt YE McDonnell LA Heeren RM Fuchser J Baykut G 《Journal of the American Society for Mass Spectrometry》2007,18(1):145-151
Analytical methods are pursued to measure the identity and location of biomolecules down to the subcellular (microm) level. Available mass spectrometric imaging methods either compromise localization accuracy or identification accuracy in their analysis of surface biomolecules. In this study, imaging FTICR-MS is applied for the spatially resolved mass analysis of rat brain tissue with the aim to optimize protein identification by the high mass accuracy and online MS/MS capabilities of the technique. Mass accuracies up to 6 ppm were obtained in the direct MALDI-analysis of the tissue together with a spatial resolution of 200 microm. The spatial distributions of biomolecules differing in mass by less than 0.1 Da could be resolved, and are shown to differ significantly. Online MS/MS analysis of selected ions was demonstrated. A comparison of the FTICR-MS imaging results with stigmatic TOF imaging on the same sample is presented. To reduce the extended measuring times involved, it is recommended to restrict the FTICR-MS analyses to areas of interest as can be preselected by other, faster imaging methods. 相似文献
107.
Smith DF Aizikov K Duursma MC Giskes F Spaanderman DJ McDonnell LA O'Connor PB Heeren RM 《Journal of the American Society for Mass Spectrometry》2011,22(1):130-137
We describe the construction and application of a new MALDI source for FT-ICR mass spectrometry imaging. The source includes a translational X-Y positioning stage with a 10×10 cm range of motion for analysis of large sample areas, a quadrupole for mass selection, and an external octopole ion trap with electrodes for the application of an axial potential gradient for controlled ion ejection. An off-line LC MALDI MS/MS run demonstrates the utility of the new source for data- and position-dependent experiments. A FT-ICR MS imaging experiment of a coronal rat brain section yields ~200 unique peaks from m/z 400-1100 with corresponding mass-selected images. Mass spectra from every pixel are internally calibrated with respect to polymer calibrants collected from an adjacent slide. 相似文献
108.
Umar Rashid Elarbi Chatir Leonardo Medrano Sandonas PA Sreelakshmi Arezoo Dianat Rafael Gutierrez Gianaurelio Cuniberti Saioa Cobo Veerabhadrarao Kaliginedi 《Angewandte Chemie (International ed. in English)》2023,62(16):e202218767
By employing a mechanically controllable break junction technique, we have realized an ideal single molecular linear actuator based on dithienylethene (DTE) based molecular architecture, which undergoes reversible photothermal isomerization when subjected to UV irradiation under ambient conditions. As a result, open form (compressed, UV OFF) and closed form (elongated, UV ON) of dithienylethene-based molecular junctions are achieved. Interestingly, the mechanical actuation is achieved without changing the conductance of the molecular junction around the Fermi level over several cycles, which is an essential property required for an ideal single molecular actuator. Our study demonstrates a unique example of achieving a perfect balance between tunneling width and barrier height change upon photothermal isomerization, resulting in no change in conductance but a change in the molecular length, which results in mechanical actuation at the single molecular level. 相似文献
109.
McDonnell U Kerchoffs JM Castineiras RP Hicks MR Hotze AC Hannon MJ Rodger A 《Dalton transactions (Cambridge, England : 2003)》2008,(5):667-675
Enantiopure dinuclear ruthenium polypyridyl complexes of the form [Ru(2)(LL)(4)L(1)](PF(6))(4) (LL = 2,2'-bipyridine (bpy) or 1,10-phenanthroline (phen); L(1)= C(25)H(20)N(4) a bis(pyridylimine) ligand containing a diphenylmethane spacer) have been synthesized using the chiral building blocks cis-[Ru(bpy)(2)(py)(2)](2+) and cis-[Ru(phen)(2)(py)(2)](2+). These dinuclear ruthenium complexes have been characterised using NMR, mass spectrometry, UV-visible absorbance, circular dichroism and linear dichroism. The compounds exhibit good photo and thermal stability. The extinction coefficient for the bpy complex at 478 nm is epsilon(478) = 15,700 mol(-1) cm(-1) dm(3) and for the phen complex is epsilon(478) = 24,900 mol(-1) cm(-1) dm(3). Both complexes have their longest wavelength (metal to ligand charge transfer) transition predominantly x/y (short axis)-polarised while the transitions at shorter wavelength are a mixture of x/y and z-polarisations, similar to both the copper helicate and iron triple helicate studied previously. Cytotoxicity studies reveal that the compounds are dramatically less active against cancer cell lines than the recently reported supramolecular cylinders prepared from the same bis(pyridylimine) ligand. 相似文献
110.
High Speed Data Processing for Imaging MS-Based Molecular Histology Using Graphical Processing Units
Jones EA van Zeijl RJ Andrén PE Deelder AM Wolters L McDonnell LA 《Journal of the American Society for Mass Spectrometry》2012,23(4):745-752
Imaging MS enables the distributions of hundreds of biomolecular ions to be determined directly from tissue samples. The application
of multivariate methods, to identify pixels possessing correlated MS profiles, is referred to as molecular histology as tissues
can be annotated on the basis of the MS profiles. The application of imaging MS-based molecular histology to larger tissue
series, for clinical applications, requires significantly increased computational capacity in order to efficiently analyze
the very large, highly dimensional datasets. Such datasets are highly suited to processing using graphical processor units,
a very cost-effective solution for high speed processing. Here we demonstrate up to 13× speed improvements for imaging MS-based
molecular histology using off-the-shelf components, and demonstrate equivalence with CPU based calculations. It is then discussed
how imaging MS investigations may be designed to fully exploit the high speed of graphical processor units. 相似文献