全文获取类型
收费全文 | 50篇 |
免费 | 1篇 |
专业分类
化学 | 25篇 |
晶体学 | 4篇 |
物理学 | 22篇 |
出版年
2021年 | 1篇 |
2020年 | 3篇 |
2017年 | 1篇 |
2016年 | 1篇 |
2015年 | 1篇 |
2014年 | 2篇 |
2013年 | 4篇 |
2012年 | 3篇 |
2011年 | 4篇 |
2008年 | 1篇 |
2007年 | 3篇 |
2006年 | 1篇 |
2004年 | 2篇 |
2003年 | 1篇 |
2002年 | 2篇 |
2000年 | 1篇 |
1997年 | 1篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1991年 | 2篇 |
1990年 | 3篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1981年 | 2篇 |
排序方式: 共有51条查询结果,搜索用时 15 毫秒
1.
2.
Ethanol determination in frozen fruit pulps: an application of quantitative nuclear magnetic resonance 下载免费PDF全文
Wilian da Silva Nunes Caroline Silva de Oliveira Glaucia Braz Alcantara 《Magnetic resonance in chemistry : MRC》2016,54(4):334-340
This study reports the chemical composition of five types of industrial frozen fruit pulps (acerola, cashew, grape, passion fruit and pineapple fruit pulps) and compares them with homemade pulps at two different stages of ripening. The fruit pulps were characterized by analyzing their metabolic profiles and determining their ethanol content using quantitative Nuclear Magnetic Resonance (qNMR). In addition, principal component analysis (PCA) was applied to extract more information from the NMR data. We detected ethanol in all industrial and homemade pulps; and acetic acid in cashew, grape and passion fruit industrial and homemade pulps. The ethanol content in some industrial pulps is above the level recommended by regulatory agencies and is near the levels of some post‐ripened homemade pulps. This study demonstrates that qNMR can be used to rapidly detect ethanol content in frozen fruit pulps and food derivatives. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
3.
We present a new device for the measurement of the metastable zone width and related parameters. The salting-out is detected by using simultaneously seven different methods: a) visual detection, b) intensity of the transmitted laser beam, c) noise associated to (b), d) intensity of the reflected laser beam, e) noise associated to (d), f) conductivity, and g) pH. Full computerization permits an easy and quick take of data on the evolution of the nucleation and crystal growth processes. The use of this apparatus shows that the waiting time for the growth component of the induction time is minimized for the method using the noise associated to the reflected light as the recorded parameter. This comparative study shows that the maximum undercooling and maximum allowable supersaturation values obtained by the different tested methods present significant differences between each other. Meanwhile, we propose that the tabulated values of such parameters should specify the experimental way followed for the obtainment of reliable data. 相似文献
4.
M.A.G. Soler G.B. Alcantara W.R. Viali J.R.L. Fernandez V.K. Garg P.C. Morais 《Surface science》2007,601(18):3921-3925
In this study γ-Fe2O3 nanoparticle, surface-coated with increasing amount of oleic acid, have been prepared while the stability against particle degradation under laser excitation intensity was investigated. Maghemite nanoparticle was obtained via oxidation of magnetite nanoparticle, the latter synthesized by co-precipitation of Fe (II) and Fe (III) ions in alkaline medium. By varying the experimental conditions of surface-coating maghemite nanoparticles with oleic acid, samples with different grafting coefficient were obtained and investigated using X-ray diffraction and different spectroscopic techniques, namely Raman, Mössbauer, and infrared. The amount of oleic acid adsorbed on the maghemite surface was estimated via the carbon content obtained from elemental analysis. 相似文献
5.
The flow activation free energy ( ΔG *) is the minimum energy necessary to induce a flow in a system that is at rest. It can be calculated from the system viscosity using the Andrade--Eyring theory. In the present work the flow activation free energy of cholesteric lyotropic liquid crystals was studied as a function of D-(+)-mannose concentration added to a nematic mesophase. The results obtained showed that all the systems can be characterized as Newtonian, but a smooth time-dependent effect can be observed mainly in systems with a lower chiral inductor concentration. It has also been observed that an increase of cholestericity leads to a decrease of ΔH * values until a limit is reached at 1 mol % of inductor. From a positive ΔS * variation it was possible to verify the existence of a locally less organized transient state during the process of micellar diffusion. When the cholesterization process was considered, the increase of the inductor concentration leads to a decrease of ΔS * and consequently to a system, as a whole, more orderly, possibly as a result of the restriction of movement caused by the presence of chiral interactions. 相似文献
6.
Abd Elmoneim O. Elkhalifa Eyad Al-Shammari Mohd Adnan Jerold C. Alcantara Khalid Mehmood Nagat Elzein Eltoum Amir Mahgoub Awadelkareem Mushtaq Ahmad Khan Syed Amir Ashraf 《Molecules (Basel, Switzerland)》2021,26(12)
Abelmoschus esculentus (Okra) is an important vegetable crop, widely cultivated around the world due to its high nutritional significance along with several health benefits. Different parts of okra including its mucilage have been currently studied for its role in various therapeutic applications. Therefore, we aimed to develop and characterize the okra mucilage biopolymer (OMB) for its physicochemical properties as well as to evaluate its in vitro antidiabetic activity. The characterization of OMB using Fourier-transform infrared spectroscopy (FT-IR) revealed that okra mucilage containing polysaccharides lies in the bandwidth of 3279 and 1030 cm−1, which constitutes the fingerprint region of the spectrum. In addition, physicochemical parameters such as percentage yield, percentage solubility, and swelling index were found to be 2.66%, 96.9%, and 5, respectively. A mineral analysis of newly developed biopolymers showed a substantial amount of calcium (412 mg/100 g), potassium (418 mg/100 g), phosphorus (60 mg/100 g), iron (47 mg/100 g), zinc (16 mg/100 g), and sodium (9 mg/100 g). The significant antidiabetic potential of OMB was demonstrated using α-amylase and α-glucosidase enzyme inhibitory assay. Further investigations are required to explore the newly developed biopolymer for its toxicity, efficacy, and its possible utilization in food, nutraceutical, as well as pharmaceutical industries. 相似文献
7.
8.
A.?G.?Pacheco G.?Salgado-Morán L.?Gerli-Candia R.?Ramírez-TagleEmail author D.?Glossman-Mitnik A.?Misra A.?F.?de Carvalho Alcantara 《Journal of Structural Chemistry》2017,58(2):261-267
Nonsteroidal anti-inflammatory drugs (NSAIDs) are among the most frequently prescribed drugs and have multiple therapeutic uses. These drugs are predominantly used for the treatment of musculoskeletal diseases because of their analgesic, antipyretic, and antiplatelet activities. Oxicams constitute an interesting class of organic compounds and have been investigated in the search for new analgesic and anti-inflammatory drugs. In the present work, a theoretical investigation of the molecular structure and spectroscopic properties of a series of five oxicams in different solvents was performed using density functional theory (DFT) methods. The geometric optimizations of the oxicams were carried out using the M06 density functional and the CBSB7 basis set. The infrared data were all obtained at the same theoretical level. The UV-Vis absorption and NMR data of some oxicams were calculated using the DFT and CBSB3 basis sets. The analysis of structural parameters, particularly the bond length and spectroscopic data, indicated that interactions occurred between the hydrogen bond types for 4-meloxicam, isoxicam, and normeloxicam. Stereoelectronic interactions caused by the substitution of alkyl groups caused the bond lengths to elongate. Similarly, the substitution of heteroatoms, such as nitrogen, sulfur, or oxygen, increased the bond lengths and angular stresses. 相似文献
9.
Hernane T. Barcelos Luclecia D. Nunes Guilherme W. Tavares Edesio F. C. Alcantara Alexandre G. S. Prado 《Journal of Thermal Analysis and Calorimetry》2011,106(2):421-425
Silica gel was modified by silanization reaction followed by functionalization of histamine in a heterogeneous route. These
materials were characterized by elementary nitrogen and chloride analyses, porosity, thermogravimetry, and infrared. The functionalized
surface adsorbed Cu(II), Co(II), Ni(II), and Zn(II) ions in an aqueous solution at 25 °C. The isotherms of adsorption are
in accordance with Langmuir model and the surface presented a great potential to form complexes metal-surface in the chemical
reason of 1:1. 相似文献
10.
Sorption and desorption properties of a CaH2/MgB2/CaF2 reactive hydride composite as potential hydrogen storage material 总被引:1,自引:0,他引:1
K. Suarez Alcantara U. Boesenberg O. Zavorotynska J. Bellosta von Colbe K. Taube M. Baricco T. Klassen M. Dornheim 《Journal of solid state chemistry》2011,184(11):3104-3109
The hydrogenation behavior of 3CaH2+4MgB2+CaF2 composite was studied by manometric measurements, powder X-ray diffraction, differential scanning calorimetry and attenuated total reflection infrared spectroscopy. The maximum observed quantity of hydrogen loaded in the composite was 7.0 wt%. X-ray diffraction showed the formation of Ca(BH4)2 and MgH2 after hydrogenation. The activation energy for the dehydrogenation reaction was evaluated by DSC measurements and turns out to be 162±15 kJ mol−1 H2. This value decreases due to cycling to 116±5 kJ mol−1 H2 for the third dehydrogenation step. A decrease of ca. 25–50 °C in dehydrogenation temperature was observed with cycling. Due to its high capacity and reversibility, this composite is a promising candidate as a potential hydrogen storage material. 相似文献