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1.
Rizwan Ahmad Niyaz Ahmad Fatimah AlOthman Haya Mohammad Fatimah AlZahrani 《Biomedical chromatography : BMC》2020,34(1):e4712
Coffee and tea are the most widely consumed beverages worldwide. However, the consumer may be unaware of the exact amount of methyl xanthine (MX, i.e. caffeine [C], theobromine [TB] and theophylline [TH]) consumed, as most of the products do not list the proper amounts. This may lead to serious risks including cardiovascular, kidney and stimulant effects. The aim of the study was to determine the MX amount in ready-to-use beverages (coffee and tea) collected from various outlets in the city of Al-Khobar, Saudi Arabia. Forty different samples of espresso, black coffee and red tea were collected. A fast, reliable and efficient UHPLC–DAD method was developed and validated for MX determination. Total lipids were extracted and fractionated in order to determine glycolipids, phospholipids and neutral lipids. The r2 value for the method was 0.980–0.988 in a linearity range of 0.5–200 ppm. The range for MX (C [0.02–2.39 mg/ml], TB [0.00–0.10 mg/ml] and TH [0.00–0.004 mg/ml]) and total lipids was 1–5 g. The amount of glycolipids (3.1 g) was higher among the lipid fractions followed by phospholipids (1.8 g) and neutral lipids (0.25 g). In general, espresso beverages (20–30 ml) contained high amounts of MX whereas black coffee beverages contained high amount of lipids. Most of the beverages expressed C, TB, TH, lipids or their fractions; however, the product with high amounts of MX and lipids at the same time was espresso (brands Chemistry and Wogard). Although the MX and lipid levels in these beverages well below the allowed limits, care must still be taken, especially when using the beverages with high serving volumes (200–250 ml) or coffee prepared via the filter method i.e. black coffee, using a high temperature for a longer time. 相似文献
2.
Niyaz Ahmad Rizwan Ahmad Atta Abbas Naqvi Md Aftab Alam Mohammad Ashafaq Zeenat Iqbal 《液相色谱法及相关技术杂志》2017,40(3):133-146
The study reports a rapid and short analytical technique for separation, characterization, and quantitation along with comparative pharmacological effect of curcuminoids in cerebral ischemia. Flash chromatography, using silica and diol columns along with gradient mobile phase, was utilized to separate three curcuminoids, i.e., curcumin (Cur), demethoxycurcumin (DMC), and bisdemethoxycurcumin (BDMC) for the first time. The separated peaks were monitored at 200–360?nm, whereas the purity of compounds (96.2–97.6%) was determined through qualitative analysis such as infrared and 1H and 13C-nuclear magnetic resonance spectroscopy, mass spectrometry (MS), and differential scanning calorimetry. Furthermore, chitosan nanoparticles (CS-NPs) for curcuminoids were prepared and characterized through zeta sizer, zeta potential, scanning electron microscopy, and transmission electron microscopy. The developed ultra performance of liquid chromatography-electrospray ionization-quadrupole-time of flight-mass spectrometry/mass spectrometry (UPLC-ESI-Q-TOF-MS/MS) method showed simplified automation and shorter run time for Combi flash over conventional separation techniques. The CS-NPs for all the three curcuminoids and combined-curcuminoids (CCr) (combined and administered together for a synergistic effect), following intranasal administration in middle cerebral artery–occluded rats were evaluated for grip strength, locomotor activity, and histopathological examination where the anti-ischemic activity was observed, in terms of potency, for all three CS-NPs and CCr as CCr>Cur>DMC>>BDMC. Cur-CS-NPs exhibited more potency among Cur, DMC, and BDMC, whereas CCr was the more potent anti-ischemic drug compared to Cur, DMC, and BDMC. For Cur the characteristic activity is proposed because of the presence of methoxy group on the phenyl ring whereas for CCr it is synergistic effect of curcuminoids. 相似文献
3.
Niyaz Ahmad 《液相色谱法及相关技术杂志》2017,40(13):677-690
The aim of this study was to investigate the brain targeting potential of rasagiline-encapsulated chitosan-coated PLGA nanoparticles (RSG-CS-PLGA-NPs) delivered intranasally into the brain. Chitosan-coated PLGA nanoparticles (RSG-CS-PLGA-NPs) were developed through double emulsification-solvent evaporation technique. RSG-CS-PLGA-NPs were characterized for particle size, zeta potential, size distribution, encapsulation efficiency, and in vitro drug release. The mean particle size, polydispersity index, and encapsulation efficiency were found to be 122.38?±?3.64, 0.212?±?0.009, and 75.83?±?3.76, respectively. High-performance liquid chromatography–mass spectroscopy and mass spectroscopy study showed a significantly high mucoadhesive potential of RSG-CS-PLGA-NPs and least for conventional and homogenized nanoformulation. Pharmacokinetic results of RSG-CS-PLGA-NPs in Wistar rat brain and plasma showed a significantly high (**p?<?0.005) AUC0-24 and amplified Cmax over intravenous treatment group. Finally, the investigation demonstrated that intranasal delivery of mucoadhesive nanocarrier showed significant enhancement of bioavailability in brain, after administration of the RSG-CS-PLGA-NPs which could be a substantial achievement of direct nose to brain targeting in Parkinson’s disease therapy and related brain disorders. 相似文献
4.
Rizwan Ahmad Niyaz Ahmad Muhammad Riaz Maria Al-tarouti Fatimah Aloufi Alaa AlDarwish Bayan Alalaq Badriah Alhanfoush Zahid Khan 《Biomedical chromatography : BMC》2020,34(11):e4942
A range of conventional, i.e. maceration, percolation, ultrasonic assisted, Soxhlet and Soxtec extraction (STE), to advanced extraction techniques of accelerated solvent extraction (ASE) was utilized for the first time in order to optimize the extract yield and recovery of phenolics—gallic acid (GA), rutin (RT) and quercetin (QT)—quantified via ultra-high performance liquid chromatography with diode array detector (UHPLC–DAD). The effect of solvents (n-hexane, dichloromethane and methanol) and temperature (60, 80 and 100°C) upon extraction yield, phenolic content and antioxidant activity (DPPH, ABTS and DPPH) was studied, and the method was validated in commercial food samples from Saudi Arabia, China and India. A high extract yield with percentage recovery was observed for STE (1221.10 mg/5 g; 24.42%) and ASE techniques (91.50 mg/1 g; 9.15%) in methanol at 100°C. UHPLC–DAD showed retention times (min) of 0.67, 1.93 and 1.90 for GA, RT and QT, respectively in the shortest runtime of 3 min. The yield for phenolics was higher for STE/ASE (ppm): 15.27/15.29 (GA), 85.24/37.56 (RT) and 52.20/33.40 (QT), respectively. In terms of antioxidant activities, low IC50 values (μg/ml) of 1.09/1.18 (DPPH), 2.11/5.32 (ABTS) and 4.35/7.88 (phenazine methosulfate–nicotinamide adenine dinucleotide) were observed for STE and ASE, respectively. Multivariate analysis for STE showed a significant (P = 0.000) correlation for extraction type vs. extract yield and phenolics content; however, there was no significance for antioxidant activities vs. extraction type. ASE showed a positive correlation for solvent vs. extraction yield, phenolics and antioxidant activity; however, there was no correlation for extraction yield and DPPH activity. Principal component analysis for STE showed a major variability (52.02%) for extraction yield and phenolics in PC1 followed by PC2 (38.30%) for antioxidant activities. For ASE, PC1 (48.68%) showed a positive correlation for solvent vs. extraction yield and phenolics while PC2 (33.12%) showed a positive correlation for temperature and antioxidant activities. STE and ASE were the optimized extraction techniques for the garlic food sample while a significant effect of solvent and temperature was observed upon extraction yield, phenolics and antioxidant activity. 相似文献
5.
M. Niyaz Ahamad Rahul Vaish K. B. R. Varma 《Journal of Thermal Analysis and Calorimetry》2011,105(1):239-243
Glasses of the composition 2TeO2–V2O5 were fabricated via the conventional melt-quenching technique. The amorphous and the glassy nature of the as-quenched samples
were confirmed by X-ray powder diffraction (XRD) and differential scanning calorimetry (DSC), respectively. The glass transition
and crystallization parameters were evaluated under non-isothermal conditions using DSC. X-ray diffraction studies confirmed
the presence of partially oriented crystallites in the heat-treated glasses. Kauzmann temperature (lower bound for the kinetically
observed glass transition) was deduced from the heating rate dependent glass transition and crystallization temperatures. 相似文献
6.
Pseudo‐first‐order rate constants (kobs) for tertiary amine (DABCO and Me3N) buffer‐catalyzed cyclization of N′‐morpholino‐N‐(2′‐methoxyphenyl)phthalamide ( 1 ) to N‐(2′‐methoxyphenyl)phthalimide ( 2 ) reveal saturation (nonlinear) plots of kobs versus [Buf]T (total tertiary amine buffer concentration) at a constant pH. Such plots at different pH have been attributed to the presence of a reactive intermediate (T?) formed by tertiary amine buffer‐catalyzed intramolecular nucleophilic addition of the secondary amide nitrogen to the carbonyl carbon of the tertiary amide group of 1 . © 2010 Wiley Periodicals, Inc. Int J Chem Kinet 42: 263–272, 2010 相似文献
7.
Pseudo‐first‐order rate constants (kobs) for pH‐independent hydrolysis of phthalimide ( 1 ), obtained at a constant total concentration of cetyltrimethylammonium bromide and hydroxide ([CTABr]T), 2.0 × 10?4 M 1 , 0.02 M MOH (M+ = Li+, Na+ and K+) and various concentrations of inert salt MX (= LiCl, LiBr, NaCl, NaBr, KCl and KBr), follow a relationship derived from the pseudophase micellar (PM) model coupled with an empirical equation. This relationship gives empirical constants, FX/S and KX /S, with S representing anionic 1 . The magnitude of FX/S is the measure of the fraction of micellized anionic 1 (S?M) transferred to the aqueous phase by the limiting concentration of X?. The value of KX/S is the measure of the ability of the counterions (X?) to expel the reactive counterions (S?) from the cationic micellar surface to the aqueous phase. The values of FX/ S are ~ 1 for MBr (M+ = Li+, Na+ and K+) and in the range ? 0.7 to ? 0.5 for MCl (M+ = Na+ and K+) at 0.006, 0.010 and 0.016 M CTABr. For LiCl, the values of FX/S become ~1 at 0.006 and 0.010 M CTABr and 0.8 at 0.016 M CTABr. The values of the empirical constants, FX/S and KX/S, have been used to determine the usual ion exchange constant (KClBr). The mean values of KClBr are 3.9 ± 0.5, 2.7 ± 0.1, and 2.6 ± 0.3 for LiX, NaX, and KX, respectively. These values of KClBr are comparable with those obtained directly by other physicochemical techniques. Thus, this new method for the determination of ion exchange constants for various counterions of cationic micelles may be considered as a reliable one. © 2010 Wiley Periodicals, Inc. Int J Chem Kinet 43: 9–20, 2011 相似文献
8.
M. Niyaz Khan 《国际化学动力学杂志》1987,19(5):415-434
The aqueous cleavage of methyl salicylate has been studied in the buffer solutions of various primary mono- and di-amines as well as secondary amines at 30°C. Both ionized (MS?) and nonionized (MSH) methyl salicylate are reactive toward primary mono- and di-amines. The second-order rate constants for the reactions of MS? with primary mono- and di-amines of pKa > 9.4 exhibit Bronsted plot of slope (βnuc) of 0.82. This high value of βnuc is attributed to an intramolecular proton transfer in a thermodynamically unfavorable direction in the rate-determining step in a stepwise process for the formation of monoanionic tetrahedral intermediate. However, a concerted process for the formation of a monoanionic tetrahedral intermediate in the reactions of MS? with amine nucleophiles wherein expulsion of leaving group is a rate-determining step is not completely ruled out. The α-effect nitrogen nucleophiles hydroxylamine and hydrazine reveal, respectively, ca. 104- and 103-fold higher reactivity compared to other amine nucleophiles of comparable basicity. The value of βnuc of 1.03 obtained for the reactions of primary monoamines with MSH is ascribed to the expulsion of leaving group as the rate-determining step. The significantly lower value of βnuc of 0.60 obtained in the reactions of MSH with both monoprotonated and unprotonated diamines is explained in terms of possible occurrence of intramolecular general acid-base catalysis. Intramolecular general base catalysis is responsible for the enhanced nucleophilic reactivity of primary amines toward MS?. Dimethylamine, piperidine, morpholine, and piperazine have no detectable nucleophilic reactivity toward MS?. 相似文献
9.
The values of pseudo first‐order rate constants (kobs) for the cleavage of N‐(2‐hydroxyphenyl)phthalamic acid ( 7 ), obtained at 4.9 × 10?2 M HCl, 35°C, and within CH3CN content range 2–80% (v/v) in mixed aqueous solvent are smaller than kobs for the cleavage of N‐(2‐methoxyphenyl)phthalamic acid ( 8 ), obtained under almost similar experimental conditions, by nearly 1.5‐ to 2‐fold. These observations show the absence of expected intramolecular general acid catalysis due to 2‐OH group in 7 . The values of kobs for the cleavage of 7 and 8 decrease by more than 20‐fold with the increase in the content of CH3CN from 2 to 80–82% (v/v) in mixed aqueous solvent. The kinetic data reveal that in acidic aqueous cleavage of 7 , N‐cyclization (leading to the formation of imide) and O‐cyclization (leading to the formation of phthalic anhydride) vary from ~10 to 15% and ~90 to 85%, respectively, with the increase in CH3CN content from 2 to 80% (v/v). Similar increase in CH3CN content causes increase in N‐cyclization from ~0 to 5% and decrease in O‐cyclization from ~100 to 95% in the acidic aqueous cleavage of 8 . Some speculative, yet conceivable, reasons for nearly 10 and 0% N‐cyclization in the cleavage of respective 7 and 8 at low content of CH3CN have been described. © 2006 Wiley Periodicals, Inc. Int J Chem Kinet 38: 746–758, 2006 相似文献
10.
In aqueous methylamine buffers of pH 10.21–11.25 nucleophilic cleavage of ionized (S–) phthalimide and general base-catalyzed cleavage of nonionized (SH) phthalimide is observed. 相似文献