全文获取类型
收费全文 | 108篇 |
免费 | 3篇 |
专业分类
化学 | 88篇 |
晶体学 | 1篇 |
数学 | 4篇 |
物理学 | 18篇 |
出版年
2022年 | 1篇 |
2021年 | 8篇 |
2020年 | 2篇 |
2019年 | 3篇 |
2018年 | 2篇 |
2017年 | 5篇 |
2016年 | 4篇 |
2015年 | 6篇 |
2014年 | 3篇 |
2013年 | 4篇 |
2012年 | 4篇 |
2011年 | 9篇 |
2010年 | 4篇 |
2009年 | 6篇 |
2008年 | 10篇 |
2007年 | 5篇 |
2006年 | 5篇 |
2005年 | 3篇 |
2001年 | 2篇 |
2000年 | 2篇 |
1994年 | 3篇 |
1993年 | 4篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1984年 | 1篇 |
1979年 | 1篇 |
1977年 | 3篇 |
1975年 | 1篇 |
1973年 | 2篇 |
1971年 | 1篇 |
1970年 | 1篇 |
1969年 | 2篇 |
排序方式: 共有111条查询结果,搜索用时 281 毫秒
91.
Accurate standardized methods for the determination of amino acid in foods are required to assess the nutritional safety and compositional adequacy of sole source foods such as infant formulas and enteral nutritionals, and protein and amino acid supplements and their hydrolysates, and to assess protein claims of foods. Protein digestibility-corrected amino acid score (PDCAAS), which requires information on amino acid composition, is the official method for assessing protein claims of foods and supplements sold in the United States. PDCAAS has also been adopted internationally as the most suitable method for routine evaluation of protein quality of foods by the Food and Agriculture Organization/World Health Organization. Standardized methods for analysis of amino acids by ion-exchange chromatography have been developed. However, there is a need to develop validated methods of amino acid analysis in foods using liquid chromatographic techniques, which have replaced ion-exchange methods for quantifying amino acids in most laboratories. Bioactive peptides from animal and plant proteins have been found to potentially impact human health. A wide range of physiological effects, including blood pressure-lowering effects, cholesterol-lowering ability, antithrombotic effects, enhancement of mineral absorption, and immunomodulatory effects have been described for bioactive peptides. There is considerable commercial interest in developing functional foods containing bioactive peptides. There is also a need to develop accurate standardized methods for the characterization (amino acid sequencing) and quantification of bioactive peptides and to carry out dose-response studies in animal models and clinical trials to assess safety, potential allergenicity, potential intolerance, and efficacy of bioactive peptides. Information from these studies is needed for determining the upper safe levels of bioactive peptides and as the basis for developing potential health claims for bioactive peptides. This information is, in turn, needed by regulatory agencies for developing appropriate policy and regulations on adding these substances to foods and for determining if health claims are scientifically substantiated. 相似文献
92.
Saman Fatima Sarwar Beg Mohammed Samim Farhan J. Ahmad 《Journal of separation science》2019,42(21):3293-3301
A systematic Quality by Design approach was employed for developing an isocratic reversed‐phase liquid chromatographic technique for the estimation of ropinirole hydrochloride in bulk drug and pharmaceutical formulations. LiChrospher RP 18‐5 Endcapped column (25 cm × 4.6 mm id) at ambient temperature (25 ± 2°C) was used for the chromatographic separation of the drug. The screening of factors influencing chromatographic separation of the active pharmaceutical ingredient was performed employing fractional factorial design to identify the influential factors. Optimization of the selected factors was carried out using central composite design for selecting the optimum chomatographic conditions. The mobile phase employed was constituted of Solvent A/Solvent B (65:35 v/v) (Solvent A [methanol/0.05 M ammonium acetate buffer, pH 7, 80:20 v/v] and Solvent B [high performance liquid chromatography grade water]) and used at 0.6 mL/min flow rate, while UV detection was performed at 250 nm. Linearity was achieved in the drug concentration range 5–100 µg/mL (R2 = 0.9998) with limits of detection and quantification of 1.02 and 3.09 µg/mL, respectively. Method validation was performed as per ICH guidelines followed by forced degradation studies, which indicated good specificity of the developed method for detecting ropinirole hydrochloride and its possible degradation products in the bulk drug and pharmaceutical formulations. 相似文献
93.
This study aims to identify two critical components required for pharmaceutical cleaning verification when an FTIR is used: (a) the number of scans required per hard-to-clean location, and (b) the limit of quantification (LOQ) of the FTIR instrument when measuring the surface contamination. The current practice in pharmaceutical manufacturing does not require multiple samples as it is standard practice to collect a single swab sample from a 25 × 25 cm area from a difficult-to-reach area of the manufacturing equipment. However, since the FTIR will only scan a tiny portion of the surface compared to the swab, a sufficient number of samples (data points) are required to provide enough confidence to ensure that the measurement results are close to the true value with a maximum degree of certainty. Similarly, calculating the LOQ for a linear regression could be straightforward. However, complexity arises when the experimental data are complex; in this case, the complexity arises due to the nature of the measurement and the lack of the defined peak in the pre-processed spectra. Therefore, this study uses the practical approach of calculating the sample size and the LOQ. 相似文献
94.
Abu Hasnath Md Golam Sarwar Ranjeet Kumar Nirala Mohammed Arif Beena Khillare 《Natural product research》2015,29(12):1166-1169
This study was carried out to assess the spermicidal action of hexane extract from the fruits of Piper longum Linn. The sperm immobilisation studies showed that 20 mg/mL of hexane extract was able to immobilise sperms completely within 20 s. The sperm revival test revealed that the effects were spermicidal as sperm immobilisation effect was irreversible. There was also a significant reduction in sperm viability in the treated group in comparison to the control. The hypo-osmotic swelling of these sperms was significantly reduced, indicating that the hexane extract may probably cause injury to the sperm plasma membrane. Hence, this study showed that the hexane extract of P. longum possesses potential contraceptive spermicidal activity in vitro. 相似文献
95.
96.
Frabetti PL Cheung HW Cumalat JP Dallapiccola C Ginkel JF Greene SV Johns WE Nehring MS Butler JN Cihangir S Gaines I Garbincius PH Garren L Gourlay SA Harding DJ Kasper P Kreymer A Lebrun P Shukla S Vittone M Bianco S Fabbri FL Sarwar S Zallo A Culbertson R Gardner RW Greene R Wiss J Alimonti G Bellini G Caccianiga B Cinquini L Di Corato M Giammarchi M Inzani P Leveraro F Malvezzi S Menasce D Meroni E Moroni L Pedrini D Perasso L Sala A Sala S Torretta D Buchholz D Claes D Gobbi B O'Reilly B 《Physical review letters》1994,72(3):324-327
97.
In this paper, a new hybrid algorithm, Hybrid Symbiosis Organisms Search (HSOS) has been proposed by combining Symbiosis Organisms Search (SOS) algorithm with Simple Quadratic Interpolation (SQI). The proposed algorithm provides more efficient behavior when dealing with real-world and large scale problems. To verify the performance of this suggested algorithm, 13 (Thirteen) well known benchmark functions, CEC2005 and CEC2010 special session on real-parameter optimization are being considered. The results obtained by the proposed method are compared with other state-of-the-art algorithms and it was observed that the suggested approach provides an effective and efficient solution in regards to the quality of the final result as well as the convergence rate. Moreover, the effect of the common controlling parameters of the algorithm, viz. population size, number of fitness evaluations (number of generations) of the algorithm are also being investigated by considering different population sizes and the number of fitness evaluations (number of generations). Finally, the method endorsed in this paper has been applied to two real life problems and it was inferred that the output of the proposed algorithm is satisfactory. 相似文献
98.
Palladium‐catalyzed cyclization of 2‐alkynyl‐N‐ethanoyl anilines to indoles: synthesis,structural, spectroscopic,and mechanistic study
下载免费PDF全文
![点击此处可从《Journal of Physical Organic Chemistry》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Mohammad Mazharol Hoque Mohammad A. Halim Mohammed G. Sarwar Md. Wahab Khan 《Journal of Physical Organic Chemistry》2015,28(12):732-742
This study reports a facial regio‐selective synthesis of 2‐alkyl‐N‐ethanoyl indoles from substituted‐N‐ethanoyl anilines employing palladium (II) chloride, which acts as a cyclization catalyst. The mechanistic trait of palladium‐based cyclization is also explored by employing density functional theory. In a two‐step mechanism, the palladium, which attaches to the ethylene carbons, promotes the proton transfer and cyclization. The gas‐phase barrier height of the first transition state is 37 kcal/mol, indicating the rate‐determining step of this reaction. Incorporating acetonitrile through the solvation model on density solvation model reduces the barrier height to 31 kcal/mol. In the presence of solvent, the electron‐releasing (–CH3) group has a greater influence on the reduction of the barrier height compared with the electron‐withdrawing group (–Cl). These results further confirm that solvent plays an important role on palladium‐catalyzed proton transfer and cyclization. For unveiling structural, spectroscopic, and photophysical properties, experimental and computational studies are also performed. Thermodynamic analysis discloses that these reactions are exothermic. The highest occupied molecular orbital?lowest unoccupied molecular orbital gap (4.9–5.0 eV) confirms that these compounds are more chemically reactive than indole. The calculated UV–Vis spectra by time‐dependent density functional theory exhibit strong peaks at 290, 246, and 232 nm, in good agreement with the experimental results. Moreover, experimental and computed 1H and 13C NMR chemical shifts of the indole derivatives are well correlated. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
99.
Sonia Zulfiqar Zahoor Ahmad Muhammad Ilyas Sarwar 《Colloid and polymer science》2007,285(15):1749-1754
Soluble aromatic polyamide chains were prepared by reacting 4–4′-oxydianiline with isophthaloyl chloride in dimethylacetamide.
To quench the HCl produced during the polymerization reaction, a stoichiometric amount of triethylamine was added. The precipitates
formed were separated leaving behind clear polyamide resin. Thin and transparent film was obtained by evaporating the solvent
and was subjected for Fourier transform infrared (IR), nuclear magnetic resonance (NMR), gel permeation chromatography, thermogravimetric
analysis, differential scanning calorimetry, water absorption, and mechanical analyses. The transparent film was found to
be soluble in dimethylacetamide, dimethyl sulfoxide, and dimethylformamide. IR and NMR spectroscopic analyses confirmed the
structure of the polyamide while the gel permeation chromatography revealed the formation of a high-molecular-weight polymer.
Thermogravimetry, differential scanning calorimetry, water absorption, and mechanical testing were also performed to further
verify its physical properties. A soluble aromatic polyamide was successfully synthesized by solution polymerization and characterized.
The polyamide has film-forming property, and the film is transparent, mechanically strong, and thermally stable. 相似文献
100.
A sensitive and selective kinetic-spectrophotometric method is proposed for the determination of microg mL(-1) amounts of Cu2+ based on its catalytic effect on the oxidation of L-ascorbic acid by Methylene Blue in a strongly acidic medium. The reaction is monitored spectrophotometrically by measuring the decrease in color intensity of Methylene Blue at 665 nm. The analysis of Cu2+ ion is performed by a fixed-time method. At a given time of 2 min at pH 2.20 and 32 degrees C, the detection limit is 10 ng mL(-1) and the relative standard deviation for 0.4 microg mL(-1) Cu2+ is 3.60% (n = 6). The method is free from most of the interferences and the effect of diverse ions on the determination of Cu2+ is also reported. The proposed method is virtually specific to copper and has been satisfactorily applied to its determination in electric copper wire samples and pharmaceutical products. Results were also verified by the atomic absorption spectrometry technique (AAS). 相似文献