全文获取类型
收费全文 | 246篇 |
免费 | 9篇 |
国内免费 | 12篇 |
专业分类
化学 | 68篇 |
晶体学 | 1篇 |
综合类 | 2篇 |
物理学 | 16篇 |
综合类 | 180篇 |
出版年
2023年 | 4篇 |
2022年 | 6篇 |
2021年 | 5篇 |
2020年 | 5篇 |
2019年 | 3篇 |
2017年 | 5篇 |
2016年 | 4篇 |
2015年 | 7篇 |
2014年 | 7篇 |
2013年 | 5篇 |
2012年 | 6篇 |
2011年 | 12篇 |
2010年 | 9篇 |
2009年 | 11篇 |
2008年 | 9篇 |
2007年 | 13篇 |
2006年 | 17篇 |
2005年 | 15篇 |
2004年 | 11篇 |
2003年 | 15篇 |
2002年 | 14篇 |
2001年 | 19篇 |
2000年 | 14篇 |
1999年 | 17篇 |
1998年 | 8篇 |
1997年 | 7篇 |
1996年 | 4篇 |
1995年 | 4篇 |
1993年 | 2篇 |
1991年 | 3篇 |
1990年 | 1篇 |
1988年 | 4篇 |
1986年 | 1篇 |
排序方式: 共有267条查询结果,搜索用时 0 毫秒
101.
102.
采用RACE方法从曼地亚红豆衫中成功克隆到Tm13AH基因.该基因包含一个1455bp的开放阅读框,编码一个具有485个氨基酸,大小为54.6kD,等电点为pH8.81的蛋白质.序列同源性比对表明:它与其他种的羟化酶具有较高的同源性,为P450羟化酶家族的成员.组织特异性表达分析结果表明:Tm13AH在叶中表达量高,在茎中表达量低,在果实中无表达.Tm13AH基因的克隆和分析为进一步在分子水平上研究其在紫杉醇代谢途径中的功能奠定了基础. 相似文献
103.
104.
The structure of a novel 3,8-seco-bicyclic taxanoid metabolite, isolated from the methanol extract of seeds of the Chinese yew, Taxus mairei, was established as (11αH)-3,8-seco-taxa-3E,7E,12(18)-triene-2α,6α,9β-triol (1) on the basis of spectral analysis including 1H NMR, 13C NMR, HMQC, HMBC, NOESY and HR-FABMS. 相似文献
105.
Xuefei Lei Guoshun Shan Fan Zhang Pengpeng Liu Li Meng 《Natural product research》2020,34(9):1337-1340
AbstractPhellodendri Chinensis Cortex is widely used in the clinic of traditional Chinese medicine. In order to enlarge the range of application, it is necessary to processed with honey, salt-water, and rice-wine, respectively. We hope to elucidate the connotation of processing, an UPLC-QqQ-MS method was used for determination and comparison the tissue distribution of alkaloids and triterpenes after oral administration water-extracts of crude and processed products. The results showed that the berberine, phellodendrine, magnoflorine, limonin, and obacunone in crude and processed products were distributed in all tissues, especially in the small intestine and stomach. In this study, we can provide a scientific basis for explaining the processing connotation of Phellodendri Chinensis Cortex processed with salt-water and rice-wine, respectively. 相似文献
106.
Taxayuntin I, a new 11 (15->l)abeotaxane, was isolated from the leaves and stems of Taxus yunnanensis. Its structure was elucidated on the basis of spectroscopic data. 相似文献
107.
《科学通报(英文版)》1993,38(13):1129-1129
108.
Reactive oxygen species, cell growth, and taxol production of Taxus cuspidata cells immobilized on polyurethane foam 总被引:1,自引:0,他引:1
Dynamic changes in reactive oxygen species (ROS) of Taxus cuspidata cells immobilized on polyurethane foam were investigated and the relation between ROS content and taxol production was discussed.
Immobilization shortened the lag period of cell growth and moderately increased H2O2 and O2
−• contents inside the microenvironment within the first 15 d. After 20 d, excessive production of H2O2 and O2
−• was observed accompanied by marked increases in membrane lipid peroxidation and cell membrane permeability. The taxol content
of immobilized cells was fourfold that of suspended cells at d 35. The addition of exogenous H2O2 barely affected malondialdehyde content and cell membrane permeability but led to an obvious accumulation of taxol. It is
inferred that the intracellular and extracellular H2O2 inside the microenvironment might be one factor promoting taxol biosynthesis under the immobilization stress. 相似文献
109.
Two-liquid-phase plant cell cultures employ the use of a partitioning system to redirect extracellular product into a second
phase. After the addition of organic solvent, in order to understand the defense system of Taxus cuspidata cells to organic solvent in two-liquid-phase suspension cultures, we investigated cells' antioxidant metabolism. The results
showed that T. cuspidata cells responded to oleic acid with oxidative bursts in both intracellular H2O2 and extracellular O2
− production. Inhibition studies with diphenylene iodonium suggested that the key enzyme responsible for oxidative bursts was
primarily NADPH oxidase. Investigation of the relationship between reactive oxygen species (ROS) and defense responses induced
by oleic acid indicated that 4% (v/v) oleic acid increased the levels of antioxidant enzymes of superoxide dismutase, ascorbate
peroxidase, and catalase and the antioxidant capacity of reduced ascorbate and glutathione. However, when oleic acid content
reached a critical value (6% [v/v]), no further increase in antioxidant enzymes and antioxidant capacity was observed, indicating
that the defense responses played a role in a certain range of oleic acid content, beyond which the overall ROS scavenging
machinery was not induced and the peroxidation of membrane lipids emerged. 相似文献
110.
Md. Nurullah Zakiya Usmani Sheeraz Ahmad Bibhu Prasad Panda Saima Amin Showkat Rasool Mir 《Journal of separation science》2023,46(6):2200841
Taxol and 10-Deacetyl baccatin III are major taxanes in the bark, needles, and endophytes of Taxus baccata. The current study aimed to develop a process for their separation from different matrices. Crude taxoid was prepared by extraction of samples with methanol, followed by partitioning with dichloromethane and precipitation with hexane. Analytical high-performance liquid chromatography involved isocratic elution on C18 column (4.6 × 250 mm, 5 μm) with methanol-water (70:30 v/v) at a flow rate of 1 ml/min. Injection volume was 20 μl and detection was carried out at 227 nm. The content of Taxol and 10-Deacetyl baccatin III in bark, needles and endophytic culture broth was 11.19 and 1.75 μg/mg; 11.19 and 1.75 μg/mg; and 2.80 and 0.22 μg/L, respectively. Preparative high-performance liquid chromatography was done on C18 column (10 × 250 mm, 5 μm) at a flow rate of 10 ml/min. About 20 g crude taxoid was processed in < 3 h with a recovery of about 90% for both the analytes. The purity of recovered Taxol and 10-Deacetyl baccatin III determined by ultra-high-performance liquid chromatography-mass spectrometry was found to be 95.78 ± 3.63% and 99.72 ± 0.18%, respectively. The structure of recovered Taxol was confirmed by nuclear magnetic resonance. The method can find use in biotransformation studies. 相似文献