全文获取类型
收费全文 | 211篇 |
免费 | 6篇 |
国内免费 | 7篇 |
专业分类
224篇 |
出版年
2023年 | 3篇 |
2022年 | 2篇 |
2021年 | 2篇 |
2020年 | 3篇 |
2019年 | 8篇 |
2018年 | 2篇 |
2017年 | 8篇 |
2016年 | 3篇 |
2015年 | 4篇 |
2014年 | 2篇 |
2013年 | 12篇 |
2012年 | 1篇 |
2011年 | 10篇 |
2010年 | 3篇 |
2009年 | 10篇 |
2008年 | 3篇 |
2007年 | 10篇 |
2006年 | 16篇 |
2005年 | 11篇 |
2004年 | 5篇 |
2003年 | 3篇 |
2002年 | 2篇 |
2001年 | 3篇 |
1999年 | 1篇 |
1998年 | 1篇 |
1997年 | 2篇 |
1996年 | 1篇 |
1993年 | 1篇 |
1991年 | 1篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 6篇 |
1984年 | 7篇 |
1983年 | 4篇 |
1982年 | 9篇 |
1981年 | 5篇 |
1980年 | 9篇 |
1979年 | 4篇 |
1978年 | 11篇 |
1977年 | 7篇 |
1976年 | 10篇 |
1975年 | 4篇 |
1974年 | 5篇 |
1973年 | 8篇 |
排序方式: 共有224条查询结果,搜索用时 9 毫秒
31.
The constitution of bacogenin-A1, obtained from the acid hydrolysate of bacoside-A, has been established as 3,18-dihydroxy-20 → 25-epoxy-22(or 23)-methyl-24-nor-dammar-22-en-16-one. The treatment of di-O-acetylbacogenin-A1 with RuO4 led to a diol instead of the usual dioxo product. 相似文献
32.
The structure of gymnospermin (1), a new diterpene triol isolated from a collection of Gymnosperma glutinosa (Compositae) from Mexico, has been determined to be (?)-7β,8α,15-trihydroxy-labdan. 相似文献
33.
34.
红花绿绒蒿的非生物碱成分 总被引:6,自引:0,他引:6
本文对红花绿绒蒿的非生物碱成分进行了研究。分离并用波谱法鉴定了的其中6个成分为:21α-羟基熊果酸(1),肉豆蔻酸2,3-二羟基丙酯(2),豆甾醇(3),β-香树精(4),熊果酸(5)及胡萝卜甙(6)。 相似文献
35.
Derek J. Baisted 《Phytochemistry》1979,18(10):1639-1641
Label appeared in several cell fractions isolated from the cotyledons of pea seeds germinated for 48 hr with mevalonate-[2-14C]. The major radioactive metabolite in each fraction was amyrin. In a similar experiment, a fraction sedimenting between 1000 and 25 000 g and a microsomal pellet were labeled with 3H from mevalonate-[2-3H]. Each of these tritiated fractions on incubation with UDP-glucose-[U-14C] yielded CHCl3-MeOH-soluble material bearing 14C and 3H. TLC of the extracts gave a compound chromatographically identical with a glucoside and bearing the two isotopes. Acid hydrolysis of this compound gave an ether-soluble material carrying 3H alone. On TLC it co-chromatographed with amyrin. Of the two tritiated cotyledon fractions, the microsomal pellet had the lower glucosyltransferase activity. The labeled amyrin residing in this fraction served as an acceptor for glucose from UDP-glucose in the presence of a glucosyltransferase from pea seedling axis tissue. In such a mixed preparation, the axis tissue transferase suffers a marked inhibition by the cotyledon preparation. 相似文献
36.
Flowers of Calendula officinalis were incubated with mevalonic acid doubly labelled with 14C in position 2 and 3H in positions 2R, 2S, 4R or 5R,S and the [3H/14C] ratios determined in squalene and pentacylic mono- and dihydroxy-triterpene alcohols and also in some derivatives prepared from the triterpene alcohols. 3H atoms were located in positions 3, 12, 16, 21, 29, 30 of the ursane skeleton, positions 3, 12, 29, 30 of the lupane skeleton and positions 3, 11, 12, 18 of the oleanane skeleton. Stabilization of α- and β-Amyrins, ω-taraxasterol and lupeol occurs with the elimination of a proton from positions 12, 21 and 29 (or 30) respectively. In addition, during hydroxylation of triterpene monols to the corresponding diols a proton is substituted by the hydroxyl group. 相似文献
37.
38.
39.
Piptadenin,a Novel 3,4‐Secooleanane Triterpene and Piptadenamide,a New Ceramide from the Stem Bark of Piptadeniastrum africanum (Hook.f.) Brenan
下载免费PDF全文
![点击此处可从《化学与生物多样性》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Amadou Dawé Marius Mbiantcha Yannick Fongang William Yosseu Nana Fawai Yakai Gilbert Ateufack Muhammad Ali Shaiq Iqbal Lubna Mehreen Lateef Bonaventure Tchaleu Ngadjui 《化学与生物多样性》2017,14(2)
Piptadenin ( 1 ), a new triterpene along with piptadenamide ( 10 ), a new ceramide, have been isolated from the AcOEt‐soluble fraction of the MeOH extract of the stem bark of Piptadeniastrum africanum along with nine known compounds, 1‐O‐[(3β,22β)‐3,22‐dihydroxy‐28‐oxoolean‐12‐en‐28‐yl]‐β‐d ‐glucopyranose ( 2 ), 22β‐hydroxyoleanic acid ( 3 ), oleanic acid ( 4 ), lupeol ( 5 ), betulinic acid ( 6 ), 5α‐stigmasta‐7,22‐dien‐3β‐ol ( 7 ), 5α‐stigmasta‐7,22‐dien‐3‐one ( 8 ), (3β)‐stigmast‐5‐en‐3‐yl β‐d ‐glucopyranoside ( 9 ) and 2,3‐dihydroxypropyl hexacosanoate ( 11 ). Except for compound 11 , all the isolated compounds are reported for the first time from this plant. The structures of the isolated compounds were elucidated by spectroscopic data including 1D and 2D NMR. The pure compounds 1 – 11 were subjected to the pharmacological screening and compounds 2 , 5 – 7 and 9 exhibited potent urease inhibitory activity with IC50 value of 25.8, 28.9, 30.1, 31.8 and 32.7 μm , respectively, whereas compound 1 showed moderate activity (IC50 = 98.7 μm ). The potent urease inhibitory activity supplemented the previous literature reports and medicinal uses of this plant. 相似文献
40.