全文获取类型
收费全文 | 92篇 |
免费 | 0篇 |
专业分类
化学 | 84篇 |
物理学 | 8篇 |
出版年
2022年 | 9篇 |
2021年 | 13篇 |
2020年 | 11篇 |
2019年 | 6篇 |
2018年 | 1篇 |
2017年 | 2篇 |
2016年 | 2篇 |
2015年 | 2篇 |
2013年 | 6篇 |
2012年 | 2篇 |
2011年 | 3篇 |
2009年 | 2篇 |
2008年 | 2篇 |
2007年 | 5篇 |
2006年 | 2篇 |
2005年 | 3篇 |
2003年 | 4篇 |
2002年 | 1篇 |
2000年 | 1篇 |
1998年 | 3篇 |
1997年 | 1篇 |
1995年 | 1篇 |
1990年 | 1篇 |
1989年 | 3篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1984年 | 1篇 |
1976年 | 1篇 |
1966年 | 1篇 |
排序方式: 共有92条查询结果,搜索用时 15 毫秒
21.
El-Ansari Mohamed A. Abdel-Latif Rasha R. Baczek Katarzyana Awad Hanem M. Sharaf Mohamed 《Chemistry of Natural Compounds》2022,58(3):433-437
Chemistry of Natural Compounds - From the methanolic extract of the flowers of Filipendula vulgaris, a new dimeric flavonol is isolated and identified as quercetinyl... 相似文献
22.
Ahmed M. Mustafa Simone Angeloni Franks Kamgang Nzekoue Doaa Abouelenein Gianni Sagratini Giovanni Caprioli Elisabetta Torregiani 《Molecules (Basel, Switzerland)》2020,25(24)
Truffles are underground edible fungi that grow symbiotically with plant roots. They have been globally considered as one of the most expensive foods because of their rarity, unique aroma, and high nutritional value as antioxidant, anti-inflammatory, antiviral, hepatoprotective, anti-mutagenic, antituberculoid immunomodulatory, antitumor, antimicrobial, and aphrodisiac. The unique flavor and fragrance of truffles is one of the main reasons to get worldwide attraction as a food product. So, the aim of this review was to summarize the relevant literature with particular attention to the active aroma components as well as the various sample preparation and analytical techniques used to identify them. The major analytical methods used for the determination of volatile organic compounds (VOC) in truffles are gas chromatography (GC), proton-transfer-reaction mass spectrometry (PTR-MS), and electronic nose sensing (EN). In addition, factors influencing truffle aroma are also highlighted. For this reason, this review can be considered a good reference for research concerning aroma profiles of different species of truffles to deepen the knowledge about a complex odor of various truffles. 相似文献
23.
Xiaoming Wang Erik Rytting Doaa R. Abdelrahman Tatiana N. Nanovskaya Gary D.V. Hankins Mahmoud S. Ahmed 《Biomedical chromatography : BMC》2013,27(7):866-873
Liquid chromatography with electrospray ionization mass spectrometry for the quantitative determination of famotidine in human urine, maternal and umbilical cord plasma was developed and validated. The plasma samples were alkalized with ammonium hydroxide and extracted twice with ethyl acetate. The extraction recovery of famotidine in maternal and umbilical cord plasma ranged from 53 to 64% and 72 to 79%, respectively. Urine samples were directly diluted with the initial mobile phase then injected into the HPLC system. Chromatographic separation of famotidine was achieved by using a Phenomenex Synergi? Hydro‐RP? column with a gradient elution of acetonitrile and 10 mm ammonium acetate aqueous solution (pH 8.3, adjusted with ammonium hydroxide). Mass spectrometric detection of famotidine was set in the positive mode and used a selected ion monitoring method. Carbon‐13‐labeled famotidine was used as internal standard. The calibration curves were linear (r2 > 0.99) in the concentration ranges of 0.631–252 ng/mL for umbilical and maternal plasma samples and 0.075–30.0 µg/mL for urine samples. The relative deviation of method was <14% for intra‐ and inter‐day assays, and the accuracy ranged between 93 and 110%. The matrix effect of famotidine in human urine, maternal and umbilical cord plasma was less than 17%. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
24.
Simone Angeloni Ahmed M. Mustafa Doaa Abouelenein Laura Alessandroni Laura Acquaticci Franks Kamgang Nzekoue Riccardo Petrelli Gianni Sagratini Sauro Vittori Elisabetta Torregiani Giovanni Caprioli 《Molecules (Basel, Switzerland)》2021,26(13)
Espresso coffee (EC) is a common coffee preparation technique that nowadays is broadly widespread all over the globe. Its popularity is in part attributed to the intense aroma and pleasant flavor. Many researchers have studied and reviewed the aroma of the coffee, but there is a lack of specific review focused on EC aroma profile even if it is intensively investigated. Thus, the objective of the current review was to summarize the aroma profile of EC and how different preparation variables can affect EC flavor. Moreover, a collection of diverse analytical procedures for volatile analysis was also reported. The findings of this survey showed that the volatile fraction of EC is extremely complex, but just some compounds are responsible for the characteristic aroma of the coffee, such as some aldehyde, ketones, furanones, furans, sulfur compounds, pyrazines, etc. In addition, during preparation, some variables, e.g., temperature and pressure of water, granulometry of the coffee particle, and brew ratio, can also modify the aroma profile of this beverage, and therefore its quality. A better understanding of the aroma fraction of EC and how the preparation variables should be adjusted according to desired EC would assist coffee workers in obtaining a higher quality product. 相似文献
25.
26.
27.
Alaa S. Abd‐El‐Aziz Amani A. Abdelghani Ebtehal G. El‐Ghezlani Doaa Abou El‐ezz Laila H. Abdel‐Rahman 《Macromolecular bioscience》2021,21(1)
The synthesis of a novel and attractive class of nonsteroidal anti‐inflammatory and antimicrobial organoiron dendrimers attached to the well‐known drug ibuprofen is achieved. The structures of these dendrimers are established by spectroscopic and analytical techniques. The antimicrobial activity of these dendrimers is investigated and tested against five human pathogenic Gram‐positive and Gram‐negative bacteria, and minimum inhibitory concentrations are reported. Some of these synthesized dendrimers exhibit higher inhibitory activity against methicillin‐resistant Staphylococcus aureus, vancomycin‐resistant Enterococcus faecium, and Staphylococcus warneri compare to the reference drugs. As well, the in vitro and in vivo anti‐inflammatory activities of these dendrimers are evaluated. The results of in vivo anti‐inflammatory activity and histopathology of inflamed paws show that all dendrimers display considerable anti‐inflammatory activity; however, second‐generation dendrimer ( G2‐D6 ) shows the best anti‐inflammatory activity, which is more potent than the commercial drug ibuprofen at the same tested dose. Results of the toxicity study reveal that G2‐D6 is the safest drug on biological tissues. 相似文献
28.
Alaa A. Hassan Fathy F. Abdel-Latif Mohamed Abdel Aziz Sara M. Mostafa Stefan Br se Martin Nieger 《中国化学快报》2015,26(9):1183-1186
2-(Hydrazinecarbothioyl)-N-substituted hydrazinecarbothioamides react with 2,3,5,6-tetrachloro-1,4-benzoquinone in high yields in a novel fast and facile method to give 5-unsubstituted-1,3,4-thiadiazole-2-amine derivatives. The synthesized compounds were characterized by spectroscopic methods and confirmed by using X-ray crystallography. A rationale for the formation of the products is presented. 相似文献
29.
Fatimah Y. Alomari Abeer A. Sharfalddin Magda H. Abdellattif Doaa Domyati Amal S. Basaleh Mostafa A. Hussien 《Molecules (Basel, Switzerland)》2022,27(3)
Four new drug-based oxidovanadium (IV) complexes were synthesized and characterized by various spectral techniques, including molar conductance, magnetic measurements, and thermogravimetric analysis. Moreover, optimal structures geometry for all syntheses was obtained by the Gaussian09 program via the DFT/B3LYP method and showed that all of the metal complexes adopted a square-pyramidal structure. The essential parameters, electrophilicity (ω) value and expression for the maximum charge that an electrophile molecule may accept (ΔNmax) showed the practical biological potency of [VO(CTZ)2] 2H2O. The complexes were also evaluated for their propensity to bind to DNA through UV–vis absorption titration. The result revealed a high binding ability of the [VO(CTZ)2] 2H2O complex with Kb = 1.40 × 10⁶ M−1. Furthermore, molecular docking was carried out to study the behavior of the VO (II) complexes towards colon cancer cell (3IG7) protein. A quantitative structure–activity relationship (QSAR) study was also implemented for the newly synthesized compounds. The results of validation indicate that the generated QSAR model possessed a high predictive power (R2 = 0.97). Within the investigated series, the [VO(CTZ)2] 2H2O complex showed the greatest potential the most selective compound comparing to the stander chemotherapy drug. 相似文献
30.
Doaa S.EL-DESOUKI Amina H.IBRAHIM Samira M.ABDELAZIM Noha A.K.ABOUL-GHEIT Dalia R.ABDEL-HAFIZAR 《燃料化学学报》2021,49(1):63-71
Sulfated zirconia (SZ) and two promoted 1%Mn/SZ catalysts which have been prepared via sol gel (Mn/SZ-S) and impregnation (Mn/SZ-I) methods were studied.The morphology of the catalysts was characterized by XRD,BET,NH_3-TPD,ICP,SEM and FT-IR analysis.The conversion of methanol to dimethyl ether and hydrocarbons was carried out in the temperature range of 120-300 ℃.The Mn/SZ-S showed the highest activity due to the high surface area with suitable acidity.The optimum condition of Mn/SZ-S catalyst was investigated at 200°C and LHSV of 0.02 h~(-1) in a time range from 30 to 210 min.It was found that the total conversion decreased from 80.18% to 53.26% at 210 min.The reusability of this catalyst was studied at the optimum condition up till four cycles for 1 h.The characterization of the reused catalyst showed a significant change in the structure and surface acidity due to the blockage of the surface acid sited by carbonaceous materials. 相似文献