全文获取类型
收费全文 | 58篇 |
免费 | 0篇 |
国内免费 | 6篇 |
专业分类
化学 | 63篇 |
晶体学 | 1篇 |
出版年
2023年 | 1篇 |
2022年 | 5篇 |
2021年 | 2篇 |
2020年 | 3篇 |
2017年 | 1篇 |
2016年 | 1篇 |
2015年 | 2篇 |
2014年 | 1篇 |
2012年 | 3篇 |
2011年 | 1篇 |
2010年 | 2篇 |
2009年 | 4篇 |
2008年 | 2篇 |
2007年 | 4篇 |
2006年 | 3篇 |
2005年 | 2篇 |
2004年 | 2篇 |
2003年 | 6篇 |
2002年 | 4篇 |
2001年 | 3篇 |
2000年 | 5篇 |
1999年 | 1篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1989年 | 1篇 |
1978年 | 1篇 |
排序方式: 共有64条查询结果,搜索用时 0 毫秒
11.
Dynamic Variation of Amino Acid Contents and Identification of Sterols in Xinyang Mao Jian Green Tea
Meng Sun Fangfang Yang Wanying Hou Shuangfeng Jiang Runqi Yang Wei Zhang Mingjie Chen Yuhang Yan Yuxin Tian Hongyu Yuan 《Molecules (Basel, Switzerland)》2022,27(11)
As important biomolecules in Camellia sinensis L., amino acids (AAs) are considered to contribute to the overall green tea sensory quality and undergo dynamic changes during growth. However, limited by analytical capacity, detailed AAs composition in different growth stages remains unclear. To address this question, we analyzed the dynamic changes of 23 AAs during leaf growth in Xinyang Mao Jian (XYMJ) green tea. Using amino acid analyzer, we demonstrated that most AAs are abundant on Pure Brightness Day and Grain Rain Day. After Grain Rain, 23 AAs decreased significantly. Further analysis shows that theanine has a high level on the day before Spring Equinox and Grain Rain, accounting for 44–61% of the total free AAs content in tea leaves. Glu, Pro, and Asp are the second most abundant AAs. Additionally, spinasterol and 22,23-dihydrospinasterol are first purified and identified in ethanol extract of XYMJ by silica gel column chromatography method. This study reveals the relationship between plucking days and the dynamic changes of AAs during the growth stage and proves the rationality of the traditional plucking days of XYMJ green tea. 相似文献
12.
Kyoko TakahashiKenichiro Hashimoto Ayako FujiyamaJunko Yamada Noriko KobayashiMasuo Morisaki Sayaka NakanoNoriyuki Hara Yoshinori Fujimoto 《Tetrahedron letters》2003,44(2):341-344
Feeding of the chemically prepared [24-13C, 24-2H]desmosterol to cell-free systems derived from rat liver and silkworm gut and to cultured cells of Oryza sativa followed by deuterium-decoupled 1H, 13C shift correlation NMR analysis of the biosynthesized cholesterol revealed the stereospecific incorporation of hydrogen atoms from the re-face of the C-24 position of desmosterol. 相似文献
13.
Ana C. S. Veríssimo Mrio Pacheco Artur M. S. Silva Diana C. G. A. Pinto 《Molecules (Basel, Switzerland)》2021,26(14)
The development of novel anticancer agents is essential to finding new ways to treat this disease, one of the deadliest diseases. Some marine organisms have proved to be important producers of chemically active compounds with valuable bioactive properties, including anticancer. Thus, the ocean has proved to be a huge source of bioactive compounds, making the discovery and study of these compounds a growing area. In the last few years, several compounds of marine origin, which include algae, corals, and sea urchins, have been isolated, studied, and demonstrated to possess anticancer properties. These compounds, mainly from securamines and sterols families, have been tested for cytotoxic/antiproliferative activity in different cell lines. Bioactive compounds isolated from marine organisms in the past 5 years that have shown anticancer activity, emphasizing the ones that showed the highest cytotoxic activity, such as securamines H and I, cholest-3β,5α,6β-triol, (E)-24-methylcholest-22-ene-3β,5α,6β-triol, 24-methylenecholesta-3β,5α,6β-triol, and 24-methylcholesta-3β,5α,6β-triol, will be discussed in this review. These studies reveal the possibility of new compounds of marine origin being used as new therapeutic agents or as a source of inspiration to develop new therapeutic agents. 相似文献
14.
M. P. Marsan I. Muller A. Milon W. Warnock Y. Nakatani G. Ourisson J. Jaud 《Journal of chemical crystallography》1995,25(11):783-786
Synthesis of sterols with varying side chains, including deuterium labeled stigmasterol and sitosterol may be performed via the Wittig-Horner coupling of a 22 aldehyde derived from stigmasterol and a suitable sulfoxide derivative of the side chain. The X-ray structure determination of this synthon have been performed since it is a crucial step in order to know the absolute configuration of the chiral carbon atoms. Crystallographic data were as follows:a=7.437(2),b=10.103(4),c=10.274(3)Å, =100.32(6)o,
=759.4 Å3, space group P21 (No.4),Z=2,D
c=1.239 g cm–3. 相似文献
15.
Wen Li Xu Xu Zhuoshi Tang Yina Guo Dongqing Fei Na Yan Fangdi Hu 《Journal of separation science》2023,46(8):2200835
Recently, we confirmed that the 95% ethanol-extracted fraction of Codonopsis Radix, which contains several triterpenoids and sterols, possesses pharmacological activities. However, due to the low content and diverse types of triterpenoids and sterols, their similar structures, lack of ultraviolet absorption, and difficulty in obtaining controls, few studies have so far assessed their contents in Codonopsis Radix. We accordingly constructed an ultra-high-performance liquid chromatography-quadrupole-time-of-flight mass spectrometry technique for the simultaneous quantitative determination of 14 terpenoids and sterols. Separation was performed on the Waters Acquity UPLC HSS T3 C18 column (100 × 2.1 mm, 1.8 μm) with 0.1% formic acid (A) and 0.1% formic acid in methanol (B) as mobile phase under gradient elution. The determination coefficients for each of the matrix calibration curves were ≥0.9925. The average recovery ranged from 81.25% to 118.05%, with relative standard deviations of <4%. The contents of 14 components in 23 batches were quantified and further analyzed through chemometrics. Linear discriminant analysis can distinguish sample varieties. The quantitative analysis method can accurately determine the contents of 14 components and thereby provide the chemical basis for the quality control of Codonopsis Radix. It also could be a valuable approach for the classification of different Codonopsis Radix varieties. 相似文献
16.
本文对生长在中国南海的细长裂江珧 (PinnaattenuateReeve)乙酸乙酯提取物进行化学成分分析。用柱层析和GC MS从中分离鉴定出 5种甾醇和游离的 3种脂肪酸 ,它们分别是麦角甾-2 6,2 7-双降 -5.2 2 -二烯 -3 β -醇 ;胆甾 -5.2 2 -二烯 -3 β -醇 ;胆甾醇 ;麦角甾 -5.2 2 -二烯 -3 β -醇 ;β -谷甾醇 ;十六酸 ;十七酸和十八酸 相似文献
17.
《Analytical letters》2012,45(4):811-825
ABSTRACT The interference of triglycerides in the analysis of sterols and their esters in fats can be eliminated by transesterification of the sample dissolved in n-hexane with a solution of sodium hydroxide 2 mol/L. Since the analytes are distributed equally in n-hexane and in methanol, better results can be obtained by accurate measurements of the volumes, and processing the standards as the samples. Triglycerides and steryl esters are transesterified quantitatively by a solution of sodium hydroxide 2 mol/L using diethyl ether as solvent. At 40°C, ten minutes are sufficient to complete the reaction. The sterols are determined in fats using a mass spectrometer detector, at concentrations as low as 5 mg/Kg. Using FID, it was possible to analyze sterols present in concentrations higher than 100 mg/Kg. 相似文献
18.
《Analytical letters》2012,45(11):1650-1661
This article has been retracted 相似文献
19.
N. Azcan M. Kara D. T. Asilbekova T. Ozek K. H. C. Baser 《Chemistry of Natural Compounds》2000,36(2):132-136
Neutral lipids, glycolipids, phospholipids, pigments, and essential oil of the above-ground part ofOriganum onites L. (Lamiaceae) are isolated and characterized for the first time. The fatty-acid composition of the lipids and the components of the hydrocarbons, sterols, and essential oil are determined by GC/MS. Linolenic and palmitic acids dominate in the acids of the lipids. The main components of the hydrocarbons are nonacosane; of the sterols, \-sitosterol; of the pigments, chlorophylls a and b. A total of 54 components are identified in the essential oil.Presented at the IIIrd International Symposium on the Chemistry of Natural Compounds, Bukhara, Uzbekistan, 19–22 December, 1998.Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 106–109, March–April, 2000. 相似文献
20.
Keiko OkuzumiNoriyuki Hara Yoshinori Fujimoto Junko YamadaAtsuko Nakamura Kyoko TakahashiMasuo Morisaki 《Tetrahedron letters》2003,44(2):323-326
Feeding studies of six 13C-labeled sterols, including clerosterol, to hairy roots of Ajugareptans var. atropurpurea have established that clerosterol is a precursor of three phytoecdysteroids, cyasterone, isocyasterone and 29-norcyasterone. 相似文献