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51.
Hui JP Stuart Grossert J Cutler MJ Melanson JE 《Rapid communications in mass spectrometry : RCM》2012,26(3):345-354
A strategy to identify metabolites of a marine biotoxin, 13-desmethyl spirolide C, has been developed using liquid chromatography coupled to high-resolution mass spectrometry (LC/HRMS). Metabolites were generated in vitro through incubation with human liver microsomes. A list of metabolites was established by selecting precursor ions of a common fragment ion characteristic of the spirolide toxin which was known to contain a cyclic imine ring. Accurate mass measurements were subsequently used to confirm the molecular formula of each biotransformation product. Using this approach, a total of nine phase I metabolites was successfully identified with deviations of mass accuracy less than 2 ppm. The biotransformations observed included hydroxylation, dihydroxylation, oxidation of a quaternary methyl group to hydroxymethyl or carboxylic acid groups, dehydrogenation and hydroxylation, as well as demethylation and dihydroxylation reactions. In a second step, tandem mass spectrometry (MS/MS) was performed to elucidate structures of the metabolites. Using the unique fragment ions in the spectra, the structures of the three major metabolites, 13,19-didesmethyl-19-carboxy spirolide C, 13,19-didesmethyl-19-hydroxymethyl spirolide C and 13-desmethyl-17-hydroxy spirolide C, were assigned. Levels of 13-desmethyl spirolide C and its metabolites were monitored at selected time points over a 32-h incubation period with human liver microsomes. It was determined that 13,19-didesmethyl-19-carboxy spirolide C became the predominant metabolite after 2 h of incubation. The stability plot of 13-desmethyl spirolide C showed first-order kinetics for its metabolism and the intrinsic clearance was calculated to be 41 μL/min/mg, suggesting first-pass metabolism may contribute to limiting oral toxicity of 13-desmethyl spirolide C. 相似文献
52.
A historical perspective of the development of spherical nucleic acid (SNA) conjugates and other three-dimensional nucleic acid nanostructures is provided. This Perspective details the synthetic methods for preparing them, followed by a discussion of their unique properties and theoretical and experimental models for understanding them. Important examples of technological advances made possible by their fundamental properties spanning the fields of chemistry, molecular diagnostics, gene regulation, medicine, and materials science are also presented. 相似文献
53.
The kinematic approximation method has shown that the peak intensity and the full width at half maximum (FWHM) of stepped surfaces exhibit an oscillatory behavior for changing incident energy. This paper generalizes the kinematic approximation to an (N × 1) reconstructed surface with a distribution of various types of lateral displacements at a step. A particular solution of this model we call the fixed point solution, yields a clear intuitive understanding of these oscillations as well as an exact solution for the step density of any surface. The specific examples of (5 × 1) and (2 × 1) reconstruction are examined to show the striking differences between the reconstructed surface diffraction patterns. These differences make an examination of the half-maximum (HM) intensity position a powerful tool to determine the surface structure for any incommensurate stepped surface. 相似文献
54.
Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) is demonstrated to be a potentially
useful tool for the rapid identification of yeasts, the grouping of Candida albicans strains, and the monitoring of germ tube-specific markers. Co-crystallized with sinapinic acid as the MALDI matrix, intact
yeast cells yielded a sufficient number of medium-sized ions (4–15 kDa) in MALDI mass spectra to provide “mass signatures”
that were diagnostic of strain type. For most isolates, the mass signatures were affected by the growth medium, length of
incubation and the cell preparation method. While the overall past success of this methodology for fungal cells has been relatively
low compared to its application to bacteria, fixing the yeast cells in 50% methanol inactivated the cells, reduced cell aggregation
in aqueous suspension solution, and more importantly, it significantly improved the mass signature quality. This simple but
critical advance in sample treatment improved mass spectrometric signal-to-noise ratios and allowed the identification of
yeasts by a mass signature approach. Under optimized conditions, Candida species (C. albicans, C. glabrata, C. krusei, C. kefyr), Aspergillus species (A. terreus, A. fumigatus, A. syndowii) and other yeast genera (Cryptococcus neoformans, Saccharomyces cerevisiae and a Rhodotorula sp.) could be distinguished. Within the C. albicans species, several common ions in the m/z 5,000–10,000 range were apparent in the mass spectra of all tested strains. In addition to shared ions, the mass spectra
of individual C. albicans strains permitted grouping of the strains. Principal component analysis (PCA) was employed to confirm spectral reproducibility
and C. albicans strain grouping by mass signatures. Finally, C. albicans germ tubes produced MALDI-TOF mass signatures that differed from yeast forms of this species. This is a rapid, sensitive
and simple method for identifying yeasts, grouping strains and following the morphogenesis of C. albicans.
Figure 相似文献
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59.
Arindam Chatterjee Stephen J. Cutler Ikhlas A. Khan John S. Williamson 《Molecular diversity》2014,18(1):51-59
The first reported synthesis of potential kinase inhibitors, 4-oxo-4,5-dihydrothieno[3,2- $c$ ]quinoline-2-carboxylic acid derivatives starting from aniline is described. This efficient high yielding sequence was carried out in six steps without any chromatographic purification. A tandem nucleophilic aromatic substitution/cyclization reaction was used as a key step in the sequence. The versatile intermediate 2-carboxylic acid was used as a suitable precursor to access the functionalization of the C-ring, by convergent analog synthesis of several novel derivatives. 相似文献
60.
Akgun Z Engelbrecht H Fan KH Barnes CL Cutler CS Jurisson SS Lever SZ 《Dalton transactions (Cambridge, England : 2003)》2010,39(42):10169-10178
(103)Rhodium(III) complexes derived from seven acyclic tetradentate N(2)S(2) ligands (one diaminedithiol and six diaminedithioether ligands) have been synthesized and characterized. Structural variations in the ligand include the length of carbon backbone between the coordinating atoms (222; 232; 323; 333), the presence or absence of gem-dimethyl groups α to sulfur, and the nature of the organic moiety on the sulfurs (hydrogen, p-methoxybenzyl and methyl). For each ligand, the formation of cis and/or trans dichloro isomeric complexes was assessed. Two complexes have been further characterized by single crystal X-ray diffraction. Preparation of the (103)Rhodium(III) complexes was conducted and overall radiochemical yields, in vitro stability and log D(7.4) values were measured. From these studies, the ligand with the 232 chain length, gem-dimethyl groups and the methyl thioether (L4) emerged as a preferred ligand for formation of rhodium complexes with trans geometry and highest radiochemical yields. 相似文献