全文获取类型
收费全文 | 289篇 |
免费 | 27篇 |
国内免费 | 19篇 |
专业分类
化学 | 283篇 |
数学 | 2篇 |
物理学 | 50篇 |
出版年
2023年 | 12篇 |
2022年 | 17篇 |
2021年 | 6篇 |
2020年 | 5篇 |
2019年 | 8篇 |
2018年 | 5篇 |
2017年 | 14篇 |
2016年 | 10篇 |
2015年 | 21篇 |
2014年 | 12篇 |
2013年 | 11篇 |
2012年 | 29篇 |
2011年 | 24篇 |
2010年 | 29篇 |
2009年 | 31篇 |
2008年 | 20篇 |
2007年 | 23篇 |
2006年 | 11篇 |
2005年 | 7篇 |
2004年 | 6篇 |
2003年 | 5篇 |
2002年 | 8篇 |
2001年 | 4篇 |
2000年 | 6篇 |
1999年 | 2篇 |
1998年 | 1篇 |
1997年 | 3篇 |
1996年 | 3篇 |
1994年 | 1篇 |
1993年 | 1篇 |
排序方式: 共有335条查询结果,搜索用时 15 毫秒
71.
中药含有丰富的无机元素,特别是人体必需的无机元素含量较高。在样品中加入混酸,再用微波消解技术消化样品,采用火焰原子吸收光谱法对五种不同品种郁金(温郁金、姜黄、广西莪术、蓬莪术和川郁金)所含有的八种具有重要生理功能的无机元素——钾、钙、钠、镁、锌、铁、铜和锰的含量进行了测定。结果显示郁金类中药材含有相近的元素成分,不同来源的品种在个别元素含量上存在差异。基于各样品所含无机元素采用聚类分析进行相关性分析,药典所收载四种郁金(温郁金、姜黄、广西莪术和蓬莪术)聚为一类,与非正品川郁金有所区别,该聚类结果与依据形态特征的传统分类学结果一致。测定结果可为郁金中无机元素与其药效的相关性提供科学依据。 相似文献
72.
基于微量热法的板蓝根提取方法和活性部位挑选 总被引:2,自引:0,他引:2
应用TAM Air微量热系统, 采用微量热法, 考察不同提取方法的板蓝根水煎液及其化学萃取部位在37 ℃时, 对大肠杆菌生长代谢的影响. 结合中医药理论, 分析板蓝根水煎液及其化学萃取部分的药效作用及其差异, 挑选板蓝根药材最佳的提取方法和抑菌最强的活性部位, 并采用试管稀释法求出抑菌活性最强部位的最小抑菌浓度(MIC). 结果表明微量热法可用于常用中药——板蓝根的提取方法和活性部位的挑选, 为进一步研究中药的药性基础提供了一种新的、快速灵敏的技术和方法. 相似文献
73.
《Journal of separation science》2003,26(17):1533-1540
In the move towards the elimination of organic solvents in the extraction process in botanicals, a new method combining surfactant and pressurized hot water extraction (PWHE) with an applied temperature below the boiling point and lower pressure from 10 to 20 bar was developed for the analysis of marker compounds that are reasonably hydrophobic such as tetradeca‐4E,12E‐diene‐8,10‐diyne‐1,6,7‐triol and tetradeca‐4E,12E‐diene‐8,10‐diyne‐1,6,7‐triol‐O‐β‐D‐glucoside in Radix Codonopsis pilosula (DangShen). Because reference substances for the proposed botanicals were not available, a method was developed to isolate the marker compounds in Radix Codonopsis pilosula. Other than surfactant‐assisted PHWE, the marker compounds present in Radix Codonopsis pilosula were extracted using pressurized liquid extraction (PLE) with methanol and PHWE with a mixture of water/ethanol (80:20). The extracts were analyzed using liquid chromatography and liquid chromatography/electrospray ionization mass spectrometry. With surfactant‐assisted PHWE, the effects of different added surfactants such as sodium dodecyl sulfate and Triton X‐100 was studied. Surfactant assisted PHWE with Triton X‐100 proved to be at least equivalent or better compared to Soxhlet extraction in terms of quantitative analysis of marker compounds in Radix Codonopsis pilosula. The method precision was less than 8% (RSD, n = 6). The presence of surfactants in PHWE was found to enhance the solubility of target compounds naturally occurring in medicinal plants. 相似文献
74.
‘Fufang Danshen tablet’ (FDT), made from Radix salvia miltiorrhiza and Panax notoginseng, is a widely used botanical drug derived from traditional Chinese medicine. Quantification of the active components of Radix salvia miltiorrhiza and Panax notoginseng is very important for regulation of FDT products. In this study HPLC hyphenated with ultraviolet (UV) detection and evaporative
light-scattering detection (ELSD) was used for simultaneous determination of nine active components (three salvianolic acids,
three tanshinones, and three saponins) of FDT products. Separation was performed on a 250 mm × 4.6 mm i.d., 5.0 μm particle-size,
C18 column with linear gradient elution. UV detection at 280 and 254 nm was used for detection of the three salvianolic acids
and the three tanshinones, respectively. ELSD was used for detection of the three saponins, which were difficult to analyze
by use of UV detection. The linearity of the calibration plots was excellent over the concentration ranges investigated (values
of R
2 were >0.99 for all the analytes) and recovery measured at three concentrations was between 92.2 and 107.7%. The validated
method was successfully used for simultaneous determination of these components in FDT products. 相似文献
75.
A LC-MS/MS method was developed for the separation and simultaneous determination of phenolic components including danshensu, protocatechuic acid, protocatechuic aldehyde and caffeic acid as well as tanshinones including cryptotanshinone, tanshinone I and tanshinone IIA in samples of Radix Salviae Miltiorrhizae and Salviae Miltiorrhizae tablet. Triple quadrupole mass spectrometry was optimized in both positive and negative ion multiple reaction monitoring modes for the simultaneous quantitative analysis of the two different types of active components by using a time-segment program. The method gave recoveries of 85.4-106.4% with relative standard deviations of 2.4-8.0% for the spiked herb samples. The limits of detection were 0.30-0.83 μg/g for the analysis of 1.0 g Radix Salviae Miltiorrhizae or tablet samples. 相似文献
76.
77.
Separation and determination of two sesquiterpene lactones in Radix inulae and Liuwei Anxian San by microemulsion electrokinetic chromatography 总被引:1,自引:0,他引:1
A novel microemulsion electrokinetic chromatography (MEEKC) method for separating and determining two sesquoterpene lactones, alantolactone (AL) and isoalantolactone (IAL), in Radix inulae and Liuwei Anxian San has been developed. The effects of several important factors such as internal organic phases, concentration of microemulsion, concentration of acetonitrile, injection time and running voltage were systematically investigated to determine the optimum conditions. The optimum microemulsion system was composed of n-hexane (0.32% w/w), SDS (1.24% w/w), 1-butanol (2.64% w/w), acetonitrile (10% w/w) and 10 mm sodium tetraborate buffer (85.80% w/w, pH 9.2). The applied voltage was 20 kV. The analytes were detected at 214 nm. Regression equations revealed linear relationships (correlation coefficients 0.9950 for AL and 0.9946 for IAL) between the peak area of each analyte and the concentration. The limits of detection (defined as a signal-to-noise ratio of about 3) were approximately 0.45 microg/mL for AL and 0.56 microg/mL for IAL. The levels of the analytes were successfully determined with recoveries ranging from 98.2 to 104.3%. Furthermore, a simple and effective extraction method, with methanol in an ultrasonic water bath for 60 min, was used for sample preparing. Also, MEEKC was compared with micellar electrokinetic chromatography (MEKC) and shown better separation results. 相似文献
78.
Zunfeng Liu Xueping Liu Dongping Liu Jun Chen Ruimin Sun Ping Jiang Zhirong Huang Fangxing Li 《Chemistry of Natural Compounds》2007,43(1):29-33
In this paper a novel method for extraction and separation of total flavones and total astragalosides from Radix astragali using a resin method is suggested. Ethanol is used as the extractant, the macroporous absorption resin modeled H-107 is used
to enrich the astragalus extract, and the macroporous strong base anion resin D-280 is used to separate the total flavones
and the total astragalosides. This method allows a good yield of total flavones of 600 mg/100 g Radix astragali, a purity of 94.2%, and a yield of total astragalosides of 28 mg/100 g Radix astragali.
Published in Khimiya Prirodnykh Soedinenii, No. 1, pp. 26–29, January–February, 2007. 相似文献
79.
黄芩药材中铅的测定及其水煎过程中铅的浸出率研究 总被引:1,自引:0,他引:1
测定了黄芩药材中有害元素铅的含量,并研究了黄芩水煎过程中铅的浸出率。 相似文献
80.
A simple and effective high-performance liquid chromatographic (HPLC) method has been developed for simultaneous quantification
of three phenolic acids (3,4-dihydroxyphenyllactic acid (Chinese name danshensu), protocatechuic aldehyde, and salvianolic
acid B) and four diterpenes (dihydrotanshinone I, cryptotanshinone, tanshinone I, and tanshinone IIA) in radix salviae miltiorrhizae. Chromatography was performed on a 250 mm × 4.6 mm i.d., 5-μm particle size, C18 column. The mobile phase was a linear gradient prepared from 0.1% (v/v) aqueous formic acid and acetonitrile at a flow-rate of 1.0 mL min−1. All the target components were well separated with high resolution and without interference. Good linearity (R
2 > 0.999) was observed over the concentration ranges investigated, and intra-day and inter-day precision were high. Temperature-controlled
ultrasound-assisted extraction was used to prevent hydrolysis of thermally unstable components during the sample-extraction
procedure, and the extraction conditions were carefully optimized. Recovery of the seven components was from 98.45 to 100.63%
and relative standard deviations were always <1.5%. The validated method was successfully used for simultaneous quantification
of the three phenolic acids and the four diterpenes in radix salviae miltiorrhizae of different geographic origins. 相似文献