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排序方式: 共有1845条查询结果,搜索用时 31 毫秒
181.
Juan F. García‐Reyes Fabio Mazzoti Jason D. Harper Nicholas A. Charipar Sheran Oradu Zheng Ouyang Giovanni Sindona R. Graham Cooks 《Rapid communications in mass spectrometry : RCM》2009,23(19):3057-3062
A fast, reagentless, and direct method is presented for the mass spectrometric analysis of olive oil without any sample pretreatment whatsoever. An ambient ionization technique, the low‐temperature plasma (LTP) probe, based on dielectric barrier discharge, is used to detect both minor and trace components (free fatty acids, phenolics and volatiles) in raw untreated olive oil. The method allows the measurement of free fatty acids (the main quality control parameter used to grade olive oil according to quality classes), selected bioactive phenolic compounds, and volatiles. The advantages and limitations of the direct analysis of extremely complex mixtures by the ambient ionization/tandem mass spectrometry combination are discussed and illustrated. The data presage the possible large‐scale application of direct mass spectrometric analysis methods in the characterization of olive oil and other foodstuffs. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
182.
分析归纳了国际市场营销管理与信息的特征,把系统目标分解为三级,依此提出的国际市场营销管理与决策信息系统结构模式,充分考虑了计算机在企业管理中应用的优势与特点,同时又考虑到国情,便于企业开发实施。 相似文献
183.
Ouyang H Lin KW Liu CC Lo SC Tzeng YM Guo ZY van Lierop J 《Physical review letters》2007,98(9):097204
A Ni80Fe20/(Ni,Fe)O thin film exhibits a positive exchange bias when cooled in a zero field and a negative exchange bias when field cooled. With transmission electron microscopy and electron energy loss spectrometry, the composition and magnetic structure has been ascertained and a distribution of magnetization easy axes about the interface extrapolated. The results indicate that the positive exchange bias is from antiferromagnetic interface moments perpendicular to their ferromagnetic counterparts. With field cooling the alignment is put into a parallel configuration resulting in a negative exchange bias. 相似文献
184.
185.
利用NND有限差分格式,发展了一种新的完全隐式的有限体积数值方法,以求解与时间相关的N-S方程.对通过单元体界面的无粘流和粘性流通量均作隐式处理.对绕流钝锥体和不同攻角的气动辅助实验飞行器的高超声速粘性流和化学反应流获得了定常数值解.对流加热率和流场电子密度的计算值与实验数据进行了比较,符合较好,证实了本方法的精确性. 相似文献
186.
Rhodium(III)‐Catalyzed [3+2]/[5+2] Annulation of 4‐Aryl 1,2,3‐Triazoles with Internal Alkynes through Dual C(sp2)H Functionalization
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Yuan Yang Ming‐Bo Zhou Xuan‐Hui Ouyang Rui Pi Dr. Ren‐Jie Song Prof. Dr. Jin‐Heng Li 《Angewandte Chemie (International ed. in English)》2015,54(22):6595-6599
A rhodium(III)‐catalyzed [3+2]/[5+2] annulation of 4‐aryl 1‐tosyl‐1,2,3‐triazoles with internal alkynes is presented. This transformation provides straightforward access to indeno[1,7‐cd]azepine architectures through a sequence involving the formation of a rhodium(III) azavinyl carbene, dual C(sp2)? H functionalization, and [3+2]/[5+2] annulation. 相似文献
187.
Li Wang Yu-Qian Chi Wen-Bin Ouyang Zhen Zang Sheng-Xiong Huang 《Natural product research》2015,29(15):1406-1413
A new myrsinol-type diterpene polyester, 14-deoxo-3β-O-propinoyl-2α,5α,7β,15β-tetra-O-acetyl-14α-O-benzoyl-myrsinol (1), and its known analogue, 14-deoxo-3β-O-prorionyl-5α,15β-di-O-acetyl-7β-O-nicotinoyl-myrsinol-14β-acetate (2), together with a monoterpenoid, pubinernoid A (3), two indole alkaloids, neoechinulin A (4) and dihydroxyisoechinulin A (5), two benzene derivatives, siringin (6) and (3-methoxyphenyl) acetic acid (7), were isolated from the 70% acetone extract of the aerial parts of Euphorbia dracunculoides Lam. Their structures were elucidated on the basis of spectroscopic evidence and comparison with literature reports. The absolute configuration of 1 was deduced by comparing experimental and calculated ECD spectra. Among them, compounds 4 and 5 were first obtained from the plant source. In addition, the 13C NMR data of compound 2 was reported for the first time. 相似文献
188.
Yuan Yang Ming‐Bo Zhou Xuan‐Hui Ouyang Rui Pi Ren‐Jie Song Jin‐Heng Li 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2015,127(22):6695-6699
A rhodium(III)‐catalyzed [3+2]/[5+2] annulation of 4‐aryl 1‐tosyl‐1,2,3‐triazoles with internal alkynes is presented. This transformation provides straightforward access to indeno[1,7‐cd]azepine architectures through a sequence involving the formation of a rhodium(III) azavinyl carbene, dual C(sp2) H functionalization, and [3+2]/[5+2] annulation. 相似文献
189.
Wenfang Xiong Chaorong Qi Haitao He Lu Ouyang Min Zhang Huanfeng Jiang 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2015,127(10):3127-3130
A base‐promoted three‐component coupling of carbon dioxide, amines, and N‐tosylhydrazones has been developed. The reaction is suggested to proceed via a carbocation intermediate and constitutes an efficient and versatile approach for the synthesis of a wide range of organic carbamates. The advantages of this method include the use of readily available substrates, excellent functional group tolerance, wide substrate scope, and a facile work‐up procedure. 相似文献
190.