全文获取类型
收费全文 | 89篇 |
免费 | 13篇 |
国内免费 | 13篇 |
专业分类
化学 | 94篇 |
综合类 | 1篇 |
数学 | 3篇 |
物理学 | 17篇 |
出版年
2023年 | 4篇 |
2022年 | 7篇 |
2021年 | 12篇 |
2020年 | 6篇 |
2019年 | 1篇 |
2018年 | 1篇 |
2017年 | 3篇 |
2016年 | 11篇 |
2015年 | 10篇 |
2014年 | 3篇 |
2013年 | 7篇 |
2012年 | 6篇 |
2011年 | 2篇 |
2010年 | 7篇 |
2009年 | 8篇 |
2008年 | 2篇 |
2007年 | 3篇 |
2006年 | 5篇 |
2005年 | 3篇 |
2004年 | 2篇 |
2003年 | 1篇 |
2002年 | 1篇 |
1999年 | 1篇 |
1997年 | 1篇 |
1996年 | 1篇 |
1993年 | 3篇 |
1992年 | 2篇 |
1988年 | 1篇 |
1978年 | 1篇 |
排序方式: 共有115条查询结果,搜索用时 31 毫秒
31.
32.
Afef Ghouili Ameni Brahmia Rached Ben Hassen 《Acta Crystallographica. Section C, Structural Chemistry》2015,71(10):873-877
A new polymorph (denoted polymorph II) of 3‐acetyl‐4‐hydroxy‐2H‐chromen‐2‐one, C11H8O4, was obtained unexpectedly during an attempt to recrystallize the compound from salt–melted ice, and the structure is compared with that of the original polymorph (denoted polymorph I) [Lyssenko & Antipin (2001). Russ. Chem. Bull. 50 , 418–431]. Strong intramolecular O—H...O hydrogen bonds are observed equally in the two polymorphs [O...O = 2.4263 (13) Å in polymorph II and 2.442 (1) Å in polymorph I], with a slight delocalization of the hydroxy H atom towards the ketonic O atom in polymorph II [H...O = 1.32 (2) Å in polymorph II and 1.45 (3) Å in polymorph I]. In both crystal structures, the packing of the molecules is dominated and stabilized by weak intermolecular C—H...O hydrogen bonds. Additional π–π stacking interactions between the keto–enol hydrogen‐bonded rings stabilize polymorph I [the centres are separated by 3.28 (1) Å], while polymorph II is stabilized by interactions between α‐pyrone rings, which are parallel to one another and separated by 3.670 (5) Å. 相似文献
33.
34.
中国的中药微量元素研究I.微量元素:一切中药的基本成分 总被引:2,自引:0,他引:2
上世纪80年代开始,在中国开展了大规模的中药微量元素研究活动。30多年来的实践证明,微量元素是一切中药的基本成分;微量元素是中药有效药成分的核心组分;微量元素是中药性效量化的物质基础;微量元素是沟通中药传统理论与现代化学物理理论的桥梁。从中药微量元素含量的测定及中药微量元素与中药药效关系初探两个方面论述微量元素是一切中药的基本成分。 相似文献
35.
Christian Chapuis Carole Cantatore Peter Fankhauser René Challand Jean‐Jacques Riedhauser 《Helvetica chimica acta》2009,92(9):1782-1799
The synthesis of various D‐labeled perfume ingredients (orris‐like, sandalwood‐like, musky, and amber‐like) is presented. These substances, possessing practically identical H2O/solid and solid/gas partition coefficients as their unlabeled analogues, are used as internal standards for the validation of a new analytical GC/MS method for the determination of low residual concentrations in H2O after biodegradability tests. 相似文献
36.
37.
Identification of chemical ingredients of peanut stems and leaves extracts using UPLC‐QTOF‐MS coupled with novel informatics UNIFI platform
下载免费PDF全文
![点击此处可从《Journal of mass spectrometry : JMS》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Lei Deng Ai‐Min Shi Hong‐Zhi Liu Naren Meruva Li Liu Hui Hu Ying Yang Chun Huang Peng Li Qiang Wang 《Journal of mass spectrometry : JMS》2016,51(12):1157-1167
Peanut stems and leaves have been used traditionally as both herbal medicines and special food in Asia. In this study, the main functional compounds of peanut stems and leaves extracts were identified using UPLC separation coupled to high resolution mass spectrometry (QTOF‐MS), and a traditional medicine library. Three different extraction solvents (ethyl acetate, petroleum ether and n‐butanol) were evaluated to prepare the extracts of peanut stems and leaves. A total of 283 chemical compounds were identified in peanut stems and leaves extracts, of which 207 compounds are tentatively new identifications in Genus Arachis. The integration of data acquisition and processing with the traditional medicine library provides a simple, efficient process to effectively facilitate the identification of chemical ingredients in complex natural product extracts. The integrated workflow for separation, detection and identification of functional compounds in natural products using UPLC/QTOF‐MS greatly improves productivity for development of traditional herbal medicines. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
38.
Qualitative screening of absorbed indoloquinazoline alkaloids and their metabolites in rat plasma after the oral administration of Wu‐Zhu‐Yu decoction by high‐resolution mass spectrometry with multiple data mining algorithms
下载免费PDF全文
![点击此处可从《Journal of separation science》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Huarong Xu Yajing Geng Ran Liu Ziyue Yuan Xujia Liu Qing Li Kaishun Bi 《Journal of separation science》2016,39(16):3260-3266
A rapid and sensitive liquid chromatography with high‐resolution mass spectrometry method with multiple data processing algorithms was developed and applied for the metabolite profiling of evodiamine and its analogous alkaloids in rat plasma after the administration of Wu‐Zhu‐Yu decoction. All samples were purified using hydrophilic‐lipophilic balanced solid‐phase extraction cartridges and analyzed by a Sciex TripleTOF 5600+ mass spectrometer with a 35 min liquid chromatography gradient elution. High‐resolution full‐scan mass spectrometry and information‐dependent acquisition tandem mass spectrometry data were analyzed using multiple data processing approaches. The results indicated that the detected eight prototype alkaloids could be metabolized to 58 metabolites through both phase I and phase II reactions. Oxidation was demonstrated to be the principle metabolic pathway of the parent compounds. The study contributes to the understanding of the absorption and metabolism of the alkaloids in Wu‐Zhu‐Yu decoction and provides a detailed analysis of scientific data. 相似文献
39.
Amanda R. Buist Alan R. Kennedy 《Acta Crystallographica. Section C, Structural Chemistry》2016,72(2):155-160
Carbamazepine (CBZ) is well known as a model active pharmaceutical ingredient used in the study of polymorphism and the generation and comparison of cocrystal forms. The pharmaceutical amide dihydrocarbamazepine (DCBZ) is a less well known material and is largely of interest here as a structural congener of CBZ. Reaction of DCBZ with strong acids results in protonation of the amide functionality at the O atom and gives the salt forms dihydrocarbamazepine hydrochloride {systematic name: [(10,11‐dihydro‐5H‐dibenzo[b,f]azepin‐5‐yl)(hydroxy)methylidene]azanium chloride, C15H15N2O+·Cl−}, dihydrocarbamazepine hydrochloride monohydrate {systematic name: [(10,11‐dihydro‐5H‐dibenzo[b,f]azepin‐5‐yl)(hydroxy)methylidene]azanium chloride monohydrate, C15H15N2O+·Cl−·H2O} and dihydrocarbamazepine hydrobromide monohydrate {systematic name: [(10,11‐dihydro‐5H‐dibenzo[b,f]azepin‐5‐yl)(hydroxy)methylidene]azanium bromide monohydrate, C15H15N2O+·Br−·H2O}. The anhydrous hydrochloride has a structure with two crystallographically independent ion pairs (Z′ = 2), wherein both cations adopt syn conformations, whilst the two hydrated species are mutually isostructural and have cations with anti conformations. Compared to neutral dihydrocarbamazepine structures, protonation of the amide group is shown to cause changes to both the molecular (C=O bond lengthening and C—N bond shortening) and the supramolecular structures. The amide‐to‐amide and dimeric hydrogen‐bonding motifs seen for neutral polymorphs and cocrystalline species are replaced here by one‐dimensional polymeric constructs with no direct amide‐to‐amide bonds. The structures are also compared with, and shown to be closely related to, those of the salt forms of the structurally similar pharmaceutical carbamazepine. 相似文献
40.
In this work, a green extraction technique, subcritical water extraction (SBWE), was employed to extract active pharmaceutical ingredients (APIs) from an important Chinese medicinal herb, Salvia miltiorrhiza (danshen), at various temperatures. The APIs included tanshinone I, tanshinone IIA, protocatechualdehyde, caffeic acid, and ferulic acid. Traditional herbal decoction (THD) of Salvia miltiorrhiza was also carried out for comparison purposes. Reproduction assay of herbal extracts obtained by both SBWE and THD were then conducted on Caenorhabditis elegans so that SBWE conditions could be optimized for the purpose of developing efficacious herbal medicine from Salvia miltiorrhiza. The extraction efficiency was mostly enhanced with increasing extraction temperature. The quantity of tanshinone I in the herbal extract obtained by SBWE at 150 °C was 370-fold higher than that achieved by THD extraction. Reproduction evaluation revealed that the worm reproduction rate decreased and the reproduction inhibition rate increased with elevated SBWE temperatures. Most importantly, the reproduction inhibition rate of the SBWE herbal extracts obtained at all four temperatures investigated was higher than that of traditional herbal decoction extracts. The results of this work show that there are several benefits of subcritical water extraction of medicinal herbs over other existing herbal medicine preparation techniques. Compared to THD, the thousand-year-old and yet still popular herbal preparation method used in herbal medicine, subcritical water extraction is conducted in a closed system where no loss of volatile active pharmaceutical ingredients occurs, although analyte degradation may happen at higher temperatures. Temperature optimization in SBWE makes it possible to be more efficient in extracting APIs from medicinal herbs than the THD method. Compared to other industrial processes of producing herbal medicine, subcritical water extraction eliminates toxic organic solvents. Thus, subcritical water extraction is not only environmentally friendly but also produces safer herbal medicine for patients. 相似文献