首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   34篇
  免费   1篇
  国内免费   5篇
化学   34篇
物理学   6篇
  2022年   2篇
  2021年   3篇
  2019年   2篇
  2018年   2篇
  2017年   4篇
  2016年   4篇
  2015年   2篇
  2014年   1篇
  2011年   1篇
  2010年   3篇
  2009年   4篇
  2008年   2篇
  2006年   1篇
  2004年   2篇
  2002年   2篇
  2001年   1篇
  1998年   1篇
  1995年   1篇
  1991年   1篇
  1984年   1篇
排序方式: 共有40条查询结果,搜索用时 93 毫秒
1.
We describe identification of seven components from Antrodia cinnamomea. Their structures were determined on the basis of spectral analysis and comparison with authentic samples. These compounds include two steroids (1, 2) (β-sitosterol and eburicol), two new steroids (3, 4) [methyl-4α-methylergost-8,24(28)-dien-3,7,11-trion-26-oate and methyl-4α-methylergost-8,24(28)-dien-3,11-dion-26-oate], two lignans (5, 6) [(+)-sesamin and 4-hydroxysesamin], and one long chain methyl ester (7) (methyl oleate). Among them, compounds 3 and 4 are first isolated from nature.  相似文献   
2.
Cinnamon bark (Rou Gui in Chinese), cinnamon twig (Gui Zhi) and shaved cinnamon bark (Gui Sin) have been widely used as spices and in traditional Chinese medicine since ancient times. On‐going issues related to quality and authenticity necessitate the development of analytical methods capable of providing an objective evaluation of samples. In this study, chemical fingerprints of cinnamon bark, cinnamon twigs and shaved cinnamon bark were established using liquid chromatography quadruple time‐of‐flight mass spectrometry in conjunction with principal component analysis (PCA). From 125 samples of cinnamon, we identified the following eight compounds and their the detection ratios: coumarin, cinnamaldehyde, cinnamyl alcohol, cinnamic acid, 2‐hydroxycinnamaldehyde, 2‐hydroxycinnamic acid, 2‐methoxycinnamaldehyde and 4‐methoxycinnamaldehyde. Of these, 4‐methoxycinnamaldehyde presented the largest variations in detection ratio, making up 64.0, 97.4 and 50.0% in cinnamon bark, cinnamon twig, and shaved cinnamon bark, respectively. The quantities of cinnamyl alcohol, coumarin and cinnamaldehyde also varied between the three parts of the plant. Chemical fingerprints of the three cinnamon samples were established using principal component analysis, the results of which indicate that cinnamon bark and shaved cinnamon bark could be easily differentiated, despite a marked similarity in outward appearance. Cinnamon twig was also shown to depart from the other clusters. The proposed method provides a fast and efficient means of identifying cinnamon herbs for quality control purposes. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   
3.
植物源防腐剂因其环保、广谱、高效等特点越来越受到木材防腐行业的重视,从微观层面探索香樟提取物影响木材腐朽的机理是发展利用植物源防腐剂的重要基础。试验采用香樟木质部的四种溶剂提取物、ACQ及樟脑配制成防腐剂进行防腐试验,结果表明:10%浓度的香樟木质部甲醇提取物以及4%浓度的ACQ处理试件均达到I级强耐腐水平,4%樟脑、10%香樟乙酸乙酯和10%丙酮提取物处理的试件达到Ⅱ级耐腐水平。通过XRD对比发现结晶区2θ衍射强度由大到小的顺序为:10%蒸馏水提取物处理材、马尾松素样、10%丙酮提取物处理材、10%甲醇提取物处理材、10%乙酸乙酯提取物处理材,四种香樟木质部提取物的防腐效果与相对结晶度大小呈正相关。通过FTIR研究发现表征纤维素和半纤维素的特征峰值越低,则被降解的量也越大,相对应的防腐剂防腐效果越差。处理试件中表征木质素的一系列特征峰峰高与未处理材相比有所升高。香樟甲醇提取物以及ACQ处理试件的I1 510/I1 738,I1 510/I1 374,I1 510/I1 160的比值最小,证明褐腐菌对其综纤维素的降解能力最弱,防腐效果最好。  相似文献   
4.
川桂皮挥发油的化学组成   总被引:3,自引:0,他引:3  
采用GC-MS技术分析了川桂(Cinnamomum wilsonii)皮挥发油的化学组成,共确定了其中42种化学成分与相对含量,占总组分相对含量的94.14%,其中有40种为萜类或其衍生物;研究结果显示,川桂皮油的主要成分为桉油素(11.02%),1(10),4-杜松二烯(10.21%),乙酸异龙脑酯(6.30%),杜松醇(5.53%),桉叶油醇(5.34%)等,与该植物叶和同属药用植物肉桂皮挥发油的主要组成均差别较大。  相似文献   
5.
香桂叶油合成胡椒基丁醚   总被引:5,自引:0,他引:5  
胡椒基丁醚 (PB)是一种可用于贮藏粮食的除虫菊酯类农药的杀虫增效剂[1 ] 。它通过抑制昆虫的多功能氧化酶 ,防止昆虫产生抗药性 ,从而增加杀虫效果。PB的市场需求量每年约 2 0 0 0吨左右。为了生产绿色农产品 ,用于农田害虫防治 ,单是国内每年就需要PB数万吨。国外用黄樟油催化加氢制成二氢黄樟油素 (DHS) ,再氯甲基化生产氯甲基二氢黄樟油素 (CMDHS) ,醚化生成PB。以黄樟树根为原料生产黄樟油严重破坏植被和资源 ,造成自然生态环境的恶化。以黄樟树根为原料生产的黄樟油已经面临全球性的资源枯竭。重庆嘉顿公司 (四川省日…  相似文献   
6.
采用水蒸汽蒸馏和乙醚萃取收集小叶香樟新鲜树叶挥发油,经气质联用分析鉴定出49个化合物,占峰面积的95.9%,挥发油得率为1.73%。主要化合物的类型为单萜(86.4%)、倍半萜(10.0%)、芳香族(1.41%)和脂肪族(1.13%)。其中质量分数最高的为L-芳樟醇(45.9%),其次为樟脑(28.5%)和橙花叔醇(4.66%)。  相似文献   
7.
The adsorption property of C. camphora fallen leaves powder (CFLP) to methyl violet (MV) from aqueous solution was studied in this work. The results showed that the CFLP has considerable adsorption property to MV. The percentage adsorption reached 91% in 50?mg?L?1 of MV solution at dosage 0.6?mg?g?1. The adsorption kinetics for MV on the CFLP follow a pseudo-second-order pathway, and the adsorption equilibrium data can be described well by the Langmuir isotherm model compared to Freundlich isotherm model. Intra-particle diffusion is not the only rate-controlling step and combination of mechanisms was involved in the entire adsorption process for MV on the CFLP; the adsorption process is endothermic, spontaneous and random. Therefore, the CFLP can be used as low-cost adsorbent for refractory cationic organic dye in wastewater.  相似文献   
8.
A novel, biochemical, and eco-friendly method has been developed for the synthesis of Ag nanopar-ticles using an aqueous leaf extract of readily accessibleCinnamomum tamala as reducing and stabi-lizing agents. These Ag nanoparticles were used to catalyze the synthesis of pyranopyrazoles. The green nature and ease of recovery and reusability of the catalyst, together with high yields of prod-ucts, make this protocol attractive and useful.  相似文献   
9.
Camphor tree (Cinnamomum camphora) is an ornamental plant that has been cultivated for a long time to obtain wood or camphor. Furthermore, its essential oil can be used as an alternative medicine and is an important source of perfume. Camphor obtained from camphor trees has long been used as a treatment for various symptoms such as inflammation, infection, congestion, muscle pain, and irritation in various regions. The purpose of this literature review is to provide knowledge of the well-established, wide, and extensive applications of camphor both in traditional and modern applications. Despite many studies focused on the essential oil of the camphor tree, there is a lack of systematic studies of its extraction or separation. Besides, various components of camphor are not fully understood, and further research is needed on the medicinal effects of individual components of C. camphor. The genus Cinnamomum has crucial economic value and theoretical significance. However, further systematic reviews and investigative studies based on existing research are needed to promote the modernization process of traditional applications of camphor. For proper use of the essential oil of C. camphora, it is imperative to consider its possible effects on humans and the environment.  相似文献   
10.
The present study aimed to assess metabolites heterogeneity among four major Cinnamomum species, including true cinnamon (Cinnamomum verum) and less explored species (C. cassia, C. iners, and C. tamala). UPLC-MS led to the annotation of 74 secondary metabolites belonging to different classes, including phenolic acids, tannins, flavonoids, and lignans. A new proanthocyanidin was identified for the first time in C. tamala, along with several glycosylated flavonoid and dicarboxylic fatty acids reported for the first time in cinnamon. Multivariate data analyses revealed, for cinnamates, an abundance in C. verum versus procyandins, dihydro-coumaroylglycosides, and coumarin in C. cassia. A total of 51 primary metabolites were detected using GC-MS analysis encompassing different classes, viz. sugars, fatty acids, and sugar alcohols, with true cinnamon from Malaysia suggested as a good sugar source for diabetic patients. Glycerol in C. tamala, erythritol in C. iners, and glucose and fructose in C. verum from Malaysia were major metabolites contributing to the discrimination among species.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号