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   166篇
  免费   4篇
  国内免费   2篇
  2023年   2篇
  2022年   2篇
  2021年   2篇
  2020年   3篇
  2019年   1篇
  2018年   1篇
  2017年   2篇
  2016年   3篇
  2015年   3篇
  2014年   6篇
  2013年   9篇
  2012年   2篇
  2011年   6篇
  2010年   3篇
  2009年   6篇
  2008年   11篇
  2007年   3篇
  2006年   13篇
  2005年   6篇
  2004年   11篇
  2003年   9篇
  2002年   5篇
  2001年   5篇
  2000年   1篇
  1999年   5篇
  1998年   1篇
  1997年   3篇
  1996年   1篇
  1995年   1篇
  1994年   2篇
  1992年   1篇
  1988年   1篇
  1986年   1篇
  1985年   8篇
  1984年   6篇
  1983年   3篇
  1982年   2篇
  1981年   5篇
  1980年   2篇
  1979年   1篇
  1978年   1篇
  1977年   3篇
  1976年   1篇
  1975年   2篇
  1974年   1篇
  1973年   4篇
  1972年   2篇
排序方式: 共有172条查询结果,搜索用时 15 毫秒
1.
2.
Azadirachtin, a triterpenoid of Azadirachta indica with feeding and growth disruptive effects on certain insects, has been found in Melia azedarach.  相似文献   
3.
Four new chromone alkaloids, chrotacumines G–J (14), have been isolated from the barks of Dysoxylum acutangulum. Their structures and absolute configurations were elucidated on the basis of NMR and CD data. Chrotacumines G and J (1 and 4) showed osteoclast differentiation inhibitory activity in a dose dependent manner.  相似文献   
4.
The seeds of Trichilia welwitschii C.DC. (Meliaceae) yielded three limonoids, dregeanin DM4 (1), reported here from a natural source for the first time, the known rohituka 3 (2) and trichilia lactone D5 (3). The bark yielded 28,29-dinorcycloart-24-ene-3,4,6-triol (4), sitosterol-3-O-β-d-glucoside, 4-hydroxy-N-methyl-l-proline, stigmasterol and sitosterol.  相似文献   
5.
6.
大叶山楝根化学成分与细胞毒活性的研究   总被引:1,自引:1,他引:0  
为了解大叶山楝(Aphanamixis grandifolia Bl.)根中的抗肿瘤活性成分,利用各种色谱技术从其95% 乙醇提取物中分离得到9 个化合物,经波谱分析分别鉴定为:7-hydroxycadalene (1)、dregeana-1 (2)、4-oxopinoresinol (3)、4-ketopinoresinol (4)、6-deoxyjacareubin (5)、schleicheol 1 (6)、豆甾醇 (7)、β-谷甾醇 (8)和胡萝卜苷 (9).其中化合物1~6 为首次从山楝属植物中分离得到,并首次报道了化合物1的碳谱数据.生物活性测试结果表明,化合物15对慢性髓原白血病细胞K562 有生长抑制活性,化合物156 对人胃癌细胞SGC-7901 有生长抑制活性.  相似文献   
7.
8.
The stem of Cabralea canjerana (Vell.) Mart. yielded three new dammarane triterpenes 20S,24S-epoxy-7β,25-dihydroxy-3,4-secodammar-4(28)-en-3-oic acid, 20S,24S-epoxy-7β,15α,25-trihydroxy-3,4-secodammar-4(28)-en-3-oic acid and 20S,24R-epoxy-7β,22ξ,25-trihydroxy-3,4-secodammar-4(28)-en-3-oic acid, which were identified on the basis of spectroscopic methods. The known dammarane triterpenes ocotillone, eichlerianic acid, shoreic acid and the sterols sitosterol, campesterol, stigmasterol, sitostenone and stigmast-5-en-3-one were also isolated and identified. The branches yielded the above three known dammaranes and eichlerialactone. The dammaranes in C. canjerana display strong similarities with Trichilieae tribe, which contains several dammaranes. The data reported herein thus provide firm support for placing Cabralea within the subfamily Melioideae, Trichilieae tribe.  相似文献   
9.
Two new limonoids aphanamolides C (1) and D (2), together with two known limonoids aphanamolide A (3) and aphapolynin A (4), were isolated from the fruits of Aphanamixis grandifolia. Their structures were assigned on the basis of spectroscopic data, with the absolute configurations of 1 and 2 being established by electronic circular dichroism (ECD) spectroscopic analyses. Those limonoids varied in the ring A: aphanamolide C featured two oxygenated bridges, and aphanamolide D was the second example containing β-hydroxy-α,β:γ,δ-dienoate moiety. The cytotoxic activities were also evaluated in vitro against four human cancer cell lines (MCF-7, A549, SMMC-7721, and HL-60).  相似文献   
10.
Studies to determine mite species richness in natural environments are still scarce, and have been conducted mainly in tropical ecosystems. The aim of this study was to determine the species richness of mites on two common native plants in fragments of the semideciduous seasonal forest in the Northwest of São Paulo State, Brazil. In each of eight fragments, 10 specimens of Actinostemon communis (Euphorbiaceae) and 10 of Trichilia casaretti (Meliaceae) were selected and marked. In total, 124 species of mites belonging to 21 families were found on the two plants. Tarsonemidae had the highest diversity (34 species), followed by Phytoseiidae (31), Tetranychidae (9) and Tenuipalpidae (8). Species accumulation curves for the two sampled plants did not reach an asymptote, even with the large sampling effort. Hence, it is estimated that a greater sampling effort may lead to an increase in species richness compared with what was found in this study. The richness of this mite fauna suggests that preservation of these plant species is important to maintain the mite diversity in these forest fragments.  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