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1.
In fields such as food and nutrition science or plant physiology, interest in untargeted profiling of flavonoids continues to expand. The group of flavonoids encompasses several thousands of chemically distinguishable compounds, among which are a number of isobaric compounds with the same elemental composition. Thus, the mass spectrometric identification of these compounds is challenging, especially when reference standards are not available to support their identification. Many different types of isomers of flavonoid glycoconjugates are known, i.e. compounds that differ in their glycosylation position, glycan sequence or type of interglycosidic linkage. This work focuses on the mass spectrometric identification of flavonoid glycoconjugate isomers possessing the same glycan mass and differing only in their aglycone core. A non‐targeted HPLC‐ESI‐MS/MS profiling method using a triple quadrupole MS is presented herein, which utilizes in‐source fragmentation and a pseudo‐MS3 approach for the selective analysis of flavonoid glycoconjugates with isomeric/isobaric aglycones. A selective MRM‐based identification of the in‐source formed isobaric aglycone fragments was established. Additionally, utilizing the precursor scanning capability of the employed triple quadrupole instrument, the developed method enabled the determination of the molecular weight of the studied intact flavonoid glycoconjugate. The versatility of the method was proven with various types of flavonoid aglycones, i.e. anthocyanins, flavonols, flavones, flavanones and isoflavones, along with their representative glycoconjugates. The developed method was also successfully applied to a commercially available sour cherry sample, in which 16 different glycoconjugates of pelargonidin, genistein, cyanidin, kaempferol and quercetin could be tentatively identified, including a number of compounds containing isomeric/isobaric aglycones. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
2.
Journal of Thermal Analysis and Calorimetry - The most critical part and barrier of phase change material (PCM) applications are the accuracy of simulations and the control of the process. The... 相似文献
3.
Mohácsi-Farkas Cs. Farkas J. Mészáros L. Reichart O. Andrássy É. 《Journal of Thermal Analysis and Calorimetry》1999,57(2):409-414
Thermal stability of vegetative cells of Listeria monocytogenes, Escherichia coli and Lactobacillus plantarum was studied by counting viable fractions and determining DSC curves of their suspensions. DSC curves in the 5–99°C range showed a series of endothermic transitions between 50 and 60°C, where the heat destruction of cells occurred. Heat denaturation of DNA required a higher temperature than cell killing. Thermal death was strongly influenced by the pH, composition and NaCl content of the suspending buffer. A mathematical model developed by us enabled comparison of DSC peak temperatures and temperatures required for loss of viability.This revised version was published online in November 2005 with corrections to the Cover Date. 相似文献
4.
The distance function \({\varrho(p, q) ({\rm or} d(p, q))}\) of a distance space (general metric space) is not differentiable in general. We investigate such distance spaces over \({\mathbb{R}^n}\), whose distance functions are differentiable like in case of Finsler spaces. These spaces have several good properties, yet they are not Finsler spaces (which are special distance spaces). They are situated between general metric spaces (distance spaces) and Finsler spaces. We will investigate such curves of differentiable distance spaces, which possess the same properties as geodesics do in Finsler spaces. So these curves can be considered as forerunners of Finsler geodesics. They are in greater plenitude than Finsler geodesics, but they become geodesics in a Finsler space. We show some properties of these curves, as well as some relations between differentiable distance spaces and Finsler spaces. We arrive to these curves and to our results by using distance spheres, and using no variational calculus. We often apply direct geometric considerations. 相似文献
5.
The possible approaches to realising a link to the SI system and the status of primary direct methods in the traceability chain of chemical measurements are discussed. Some results obtained with the new coulometric standard system are presented.
相似文献6.
7.
M. Bokor T. Marek K. Süvegh K. Tompa A. Vértes Zs. Nemes-vetéssy K. Burger 《Journal of Radioanalytical and Nuclear Chemistry》1996,211(1):247-253
The complexes [Zn(1-propyltetraole)6](BF4)2 (Zn-ptz) and [Fe(methyltetrazole)6](BF4)2 (Fe-mtz) were investigated by positron annihilation and solid-state NMR spectroscopy. For Zn-ptz signs of structural rearrangements were found between 70 and 145 K. For the spin-crossover complex Fe-mtz a transition affecting the high-spin stat Fe2+ ions at lattice site B occurs below 15 K. 相似文献
8.
The structure and properties of non-pyrophoric skeleton catalysts prepared from NiSi, NiAlSi, NiMg and NiZn alloys have been studied—apart from other thermal methods—by means of the derivatograph.Our experimental results have contributed to the explanation of the non-pyrophoric behaviour of these catalysts. We demonstrated that the desorption of the hydrogen content in our catalysts is not accompanied by the oxidation of active nickel. This oxidation takes place only at higher temperatures, above 200°C, at a rate proportional to the amount of active nickel.Other constituents of the catalysts (adsorbed water, hydroxide content) were also determined from the experimental data. The outstandingly high Mg(OH)2 content of the NiMg catalyst indicates that its structure is dissimilar: Mg(OH)2 also acts as support for the catalyst. 相似文献
9.
10.
A. Perjéssy 《Tetrahedron》1973,29(20):3207-3212
The use of the improved Seth-Paul-Van Duyse equation (SPVDE) provides a new statistically significant method for determination of transmissive factors of polar effects for various bridge groups. The method was applied to the CO stretching frequencies of s-cis and s-trans conformers of 98 R1CHCHCOR2 compounds. The transmissive factors for CHCH group in both conformations s-cis and s-trans have been calculated with an accuracy about of one order higher than found by using the methods described earlier. The applicability of the improved SPVDE to the 137 CO stretching frequencies of various R1CHCHCOR2 compounds has been proved. 相似文献