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   24篇
  免费   2篇
  国内免费   6篇
化学   27篇
物理学   5篇
  2023年   1篇
  2021年   1篇
  2020年   2篇
  2019年   1篇
  2017年   1篇
  2016年   1篇
  2015年   1篇
  2014年   1篇
  2013年   1篇
  2012年   3篇
  2011年   2篇
  2010年   2篇
  2009年   2篇
  2008年   1篇
  2006年   3篇
  2004年   3篇
  2003年   2篇
  2001年   1篇
  2000年   1篇
  1998年   1篇
  1997年   1篇
排序方式: 共有32条查询结果,搜索用时 46 毫秒
1.
Triterpene acids were extracted from the epidermis of Poria cocos (Schw.) Wolf. These acids were found to inhibit the growth of lung cancer cells in vitro and in vivo. An efficient method for the preparative separation of antitumor triterpene acids was established that involves the combination of pH‐zone‐refining counter‐current chromatography and conventional high‐speed counter‐current chromatography. We used pH‐zone‐refining counter‐current chromatography to concentrate the triterpene acids using a two‐phase solvent system composed of petroleum ether/ethyl acetate/methanol/water (3:7:5:5, v/v/v/v), trifluoroacetic acid (10 mM) was added to the upper phase as a retainer, and ammonia (10 mM) was added to the lower phase as an eluter. As a result, 200 mg concentrate of triterpene acids was obtained from 1.0 g of crude extract. The concentrate was further separated by conventional high‐speed counter‐current chromatography using a solvent system composed of petroleum ether/ethyl acetate/methanol/water (0.8:1.2:1.2:0.9, v/v), yielding 50 mg of poricoic acid A and 5 mg of poricoic acid B from 120 mg concentrate, respectively. The inhibitory activity of the major compound on lung A549 cells was examined and poricoic acid A was found to significantly inhibit the growth of A 549 cells.  相似文献   
2.
赖鹤鋆  衷明华 《光谱实验室》2011,28(4):1866-1868
用硝酸-高氯酸的混合酸对车前草、泽泻、乌元参、茯苓4种药材进行处理,用火焰原子吸收光谱法测定其中Ca、Mg、Fe、Zn、Mn、Co 6种微量元素。样品加标回收率在96.0%—103.5%之间,相对标准偏差(RSD)小于3.2%,该方法测量简便、准确,结果可靠。  相似文献   
3.
In this work, influence of molecular weight and periodate modification ofβ-D-glucans isolated from Poria cocos sclerotium on the antitumor activities against Sar-coma 180 and Ehrlich ascites carcinoma (EAC) tumor was studied. The results show thattwo glucans PC3 (linear β-(1→3)-D-glucan) and PC4 [β-(1→3)-D-glucan with a fewof branches and glucuronic acid] are devoid of antitumor activity. However, when theglucans were modified by periodate oxidation, borohydride reduction and mild hydrolysisor partially hydrolysis, the derivatives have obvious antitumor activities. The decreasein molecular weight of glucans after periodate modification hardly affects their antitumoractions, but on the other hand, the decrease of molecular weight without periodate modi-fication could lead to an enhancement of the antitumor activities. Moreover, the glucansand these derivatives have much higher enhancement ratios of body weight of mice thanthat of 5-Fluorouracil (5-Fu), suggesting that they are less toxic than 5-Fu.  相似文献   
4.
High purity polysaccharide of pachyman was isolated from the powder of Poria cocos sclerotium with an yield of 77.8%. The intrinsic viscosity of polysaccharide was found to be 78.95 mL/g in DMSO solution at 25℃. The isolated polysaccharide was reacted with chlorosulfonic acid to obtain pachyman sulfate using the improved Wolfrom method. The results of the orthogonality experiment on the sulfation reaction identified that the effectiveness of the reaction conditions on the degree of sulfation and the value of intrinsic viscosity is in the following order: molar ratio of chlorosulfonic acid to glucoside (3-5) > reaction temperature (60-80℃) > reaction time (1-2 h). The kinetic studies of the pachyman sulfationindicated that the hydrolysis is accompanied with the sulfation process. The decrease in intrinsic viscosity of the sulfated pachyman is proportional to the increase in the degree of sulfation under the mild reaction conditions of < 80℃,chlorosulfonic acid/glucoside mole ratio < 5, and reaction time < 2 h. Beyond the above reaction conditions, excessive loss of -OH group occurs during hydrolysis. The NMR results indicated a complete sulfation on C-6 and a partial sulfation on the C-2 and C-4 of glucoside.  相似文献   
5.
6.
Abstract

Poria cocos is an edible medicinal mushroom with the effects of inducing diuresis, excreting dampness, invigorating the spleen and tranquilizing the mind. The triterpenoids of Poria cocos as the main active ingredients have shown health benefits of the central nervous system of the human body. Accordingly, this study aimed at further understanding the antidepressant-like effect and a potential mechanism of the triterpenoids extracts from Poria cocos (TPC). As a result, the TPC significantly ameliorated depression-like behaviors on chronic unpredictable mild stress (CUMS) rats, and restored the levels of brain-derived neurotrophic factor and nerve growth factor in the hippocampus of rats. Gut microiota analysis revealed that TPC could increase the biodiversity and markedly regulate the relative abundance of [Prevotella], Allobaculum and Ochrobactrum of CUMS rats. The cecal contents metabolomics pointed to thirteen biomarkers associated with TPC antidepressant effect, which involved in primary bile acid biosynthesis, taurine and hypotaurine metabolism, arginine and proline metabolism. Correlation analysis further showed that there was a strong correlation relationship between the gut microbiota and the cecal contents metabolites, especially compounds involved in energy metabolism, inflammation and immunity. In conclusion, TPC showed a potential antidepressant effect, which was possibly mediated the gut microbiota and cecal contents metabolism.  相似文献   
7.
A new epidioxy-tetracyclic triterpenoid, 3-(2-hydroxyacetoxy)-5α, 8α-peroxydehydrotumulosic acid (10), along with nine known compounds were isolated from Poria cocos Wolf (Polyporaceae). Their structures were determined by extensive spectroscopic analyses and comparison with literature data. The cytotoxicity of these compounds against human cancer cell lines MNK-45 was evaluated by MTT method.  相似文献   
8.
不同产地茯苓皮药材红外光谱的识别   总被引:2,自引:0,他引:2  
采用红外光谱、二阶导数光谱和二维相关红外光谱对大别山地区和云南省两大道地主产区的茯苓皮进行鉴别分析。结果表明,不同产地茯苓皮的红外光谱都有1 149,1 079和1 036cm-1等表征糖类成分的特征吸收峰,其中大别山产区(湖北省、安徽省)的茯苓皮中1 619,1 315和780cm-1等表征草酸钙的特征吸收峰比较显著,云南产区的茯苓皮中797,779,537和470cm-1等表征硅酸盐的特征吸收峰更加明显。比较450~1 650cm-1波数范围内的二阶导数红外光谱可知,两个产区茯苓皮所含糖类物质有所不同。在二维相关红外光谱中,不同产地茯苓皮所含糖类物质的差异更加直观显著。红外光谱法直观、简单、方便、快速,可以作为鉴别不同产地茯苓皮,诠释产地与药效之间关联性的一种有效准确的新方法。  相似文献   
9.
治疗冠心病中药的微量元素测定   总被引:10,自引:0,他引:10  
对治疗冠心病中药丹参、降香、红花、茯苓及复方丹参注射液中铜、锌、铅、镉的含量 进行了测定。结果表明,其中必需微量元素铜、锌含量均比有害元素铅、镉的含量要高出1-2个数量级,其铜/锌比值与正常人血清铜/锌比值能较好地吻合,镉/锌比值较低。  相似文献   
10.
为研究草酸钙(CaC2O4)晶体成核、生长和聚集,探讨降解茯苓多糖(PCP)的抑制作用,采用X射线衍射、FT-IR、扫描电镜、拉曼光谱、ζ电位仪和紫外分光光度计等方法对不同条件下形成的CaC2O4晶体进行表征。结果表明,在低过饱和度(RS≤26.6)时,主要生成一水草酸钙(COM)晶体;至RS为37.6和46.0时分别生成了11.6%和38.3%的二水草酸钙(COD)晶体,且高RS时晶体的聚集程度增加。在RS相同时,随着Ca2+/Ox2-(Ox2-=C2O42-)化学计量比(nCa2+/nOx2-)增大,晶体中COD比例增加。降解PCP的加入可增加体系中可溶性Ca2+浓度,减少生成的CaC2O4晶体质量,增加晶体表面ζ电位绝对值,这些均有利于抑制CaC...  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