全文获取类型
收费全文 | 214篇 |
免费 | 8篇 |
专业分类
化学 | 171篇 |
力学 | 2篇 |
数学 | 11篇 |
物理学 | 27篇 |
无线电 | 11篇 |
出版年
2023年 | 1篇 |
2022年 | 4篇 |
2021年 | 13篇 |
2020年 | 5篇 |
2019年 | 6篇 |
2018年 | 5篇 |
2017年 | 2篇 |
2016年 | 13篇 |
2015年 | 5篇 |
2014年 | 8篇 |
2013年 | 13篇 |
2012年 | 11篇 |
2011年 | 23篇 |
2010年 | 12篇 |
2009年 | 11篇 |
2008年 | 14篇 |
2007年 | 19篇 |
2006年 | 12篇 |
2005年 | 11篇 |
2004年 | 8篇 |
2003年 | 2篇 |
2002年 | 7篇 |
2001年 | 1篇 |
2000年 | 2篇 |
1999年 | 1篇 |
1998年 | 1篇 |
1997年 | 1篇 |
1996年 | 2篇 |
1991年 | 1篇 |
1988年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1980年 | 1篇 |
1974年 | 1篇 |
1906年 | 2篇 |
排序方式: 共有222条查询结果,搜索用时 968 毫秒
191.
Gas chromatography analysis of major free mono‐ and disaccharides in milk: Method assessment,validation, and application to real samples
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)
Ilenia Idda Nadia Spano Marco Ciulu Valeria M. Nurchi Angelo Panzanelli Maria I. Pilo Gavino Sanna 《Journal of separation science》2016,39(23):4577-4584
Saccharides are functional constituents of milk. Although d ‐lactose represents almost the totality of the saccharides in the milk, minor species, like d ‐glucose, d ‐galactose, myo‐inositol and, as a result of severe thermal treatments, monosaccharides like d ‐tagatose, are also detectable. Although chromatography has been the main analytical approach used for accomplishing this task, quite surprisingly a validated gas chromatographic method aimed at the simultaneous determination of these compounds is still needed. Hence, our contribution is devoted to fill this gap. After the optimization of clean‐up and derivatization (conversion of saccharides in their trimethyl silyl ethers) steps, the adoption of a highly cross‐linked silphenylene stationary phase permitted to obtain high resolution and a fast chromatographic run. Validation was accomplished in terms of limit of detection, limit of quantification, linearity, precision, and trueness. The accuracy of the method was successfully tested on a number of partially skimmed milk samples. Excellent limits of detection for all analytes make this method eligible, also with respect to a gas chromatographic/mass spectrometry approach, for routine analysis and quality control in the dairy industries. 相似文献
192.
Hourahine B Sanna S Aradi B Köhler C Niehaus T Frauenheim T 《The journal of physical chemistry. A》2007,111(26):5671-5677
The density functional based tight-binding (DFTB) method can benefit substantially from a number of developments in density functional theory (DFT) while also providing a simple analytical proving ground for new extensions. This contribution begins by demonstrating the variational nature of charge-self-consistent DFTB (SCC-DFTB), proving the presence of a defined ground-state in this class of methods. Because the ground state of the SCC-DFTB method itself can be qualitatively incorrect for some systems, suitable forms of the recent LDA+U functionals for SCC-DFTB are also presented. This leads to both a new semilocal self-interaction correction scheme and a new physical argument for the choice of parameters in the LDA+U method. The locality of these corrections can only partly repair the HOMO-LUMO gap and chemical potential discontinuity, hence a novel method for introducing this further physics into the method is also presented, leading to exact derivative discontinuities in this theory at low computational cost. The prototypical system NiO is used as an illustration for these developments. 相似文献
193.
A direct HPLC enantioseparation of three new chiral oxadiazoline derivatives endowed with potential MAO-B inhibitory activity was accomplished on the immobilised Chiralpak IA chiral stationary phase. Multi-mg amounts of enantiomers with high enantiomeric purity (ee ≥ 98%) were rapidly collected using pure dichloromethane as eluent. The absolute configuration and chiroptical properties of the enantiomers isolated at semipreparative scale were exhaustively determined. 相似文献
194.
Paola Manca Maria I. Pilo Giovanni Casu Serafino Gladiali Gavino Sanna Roberta Scanu Nadia Spano Antonio Zucca Chiara Zanardi Diego Bagnis Luca Valentini 《Journal of polymer science. Part A, Polymer chemistry》2011,49(16):3513-3523
A novel polythiophene bearing a pendant terpyridine moiety has been synthesized by electrochemical polymerization of a new thiophene monomer, namely 4′‐(2,2′:5′,2″‐terthien‐3′‐ethynyl)‐2,2′:6′,2″‐terpyridine (TAT). The insertion of a conjugated ethynyl spacer between the terthiophene and the terpyridine fragments provides for an effective extension of the delocalization of electrons within the structural unit and the polymer as a whole. The synthesis and characterization of the relevant monomer, the electrosynthesis of the corresponding polymer and its electrochemical, UV–visible spectroelectrochemical and IR characterization are described. Finally, a comparison between the electrochemical, spectroscopic, and spectroelectrochemical properties of PTAT and the analogue, saturated‐spacer PTTT (TTT = 4′‐[(2,2′:5′,2″‐terthien‐3′‐yl)methoxy]‐2,2′:6′,2″‐terpyridine) polymer is discussed. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011 相似文献
195.
Niina Aaltonen Juha R. Savinainen Casandra Riera Ribas Jani Rönkkö Anne Kuusisto Jani Korhonen Dina Navia-Paldanius Jukka Häyrinen Piia Takabe Heikki Käsnänen Tatu Pantsar Tuomo Laitinen Marko Lehtonen Sanna Pasonen-Seppänen Antti Poso Tapio Nevalainen Jarmo T. Laitinen 《Chemistry & biology》2013,20(3):379-390
196.
Valeria Alzari Daniele Nuvoli Mariano Casu Roberta Sanna Ernesto Rivera Alberto Mariani 《Journal of polymer science. Part A, Polymer chemistry》2013,51(21):4618-4625
Novel polyacrylamide‐based hydrogels containing 3‐(trimethoxysilyl)propyl methacrylate and/or tetraethoxy silane were synthesized by means of frontal polymerization, using ammonium persulfate as initiator, N,N′‐methylene bisacrylamide as crosslinking agent and dimethyl sulfoxide as solvent. The obtained samples were treated at pH of 2 or 5 to induce the sol–gel reaction and evaluate their swelling behavior in the conditions. The occurrence of this reaction was assessed by solid‐state NMR. Moreover, the thermal properties of the dry materials were studied by differential scanning calorimetry and thermal gravimetric analysis, and their water‐contact angles were measured. It was found that the amount of Si affects the extent of swelling and the hydrophilicity of the resulting materials. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 4618–4625 相似文献
197.
198.
Angelo Zinellu Salvatore Sotgia Elisabetta Pisanu Bastianina Scanu Manuela Sanna Maria Franca Usai Roberto Chessa Luca Deiana Ciriaco Carru 《Analytical and bioanalytical chemistry》2010,398(5):1973-1978
The role of neurotransmitter amino acids (NAAs) in the functioning of the nervous system has been the focus of increasingly
intense research over the past several years. Among the various amino acids that have important roles as neurotransmitters,
there are alanine (Ala), glutamic acid (Glu), aspartic acid (Asp), serine (Ser), taurine (Tau) and glycine (Gly). NAAs are
present in plasma, cells and—at trace levels—in all biological fluids, but complex components in biological matrices make
it difficult to determine them in biological samples. We describe a new capillary electrophoresis (CE) method with laser-induced
fluorescence detection by which analytes are resolved in less than 12 minutes in a 18 mmol/L phosphate run buffer at pH 11.6.
The use of elevated temperatures during sample derivatization leads to a drastic reduction in the reaction time, down to 20 min,
compared to the 6–14 h usually described for reactions between FITC and amino acids at room temperature. In order to demonstrate
its wide range of applications, the method was applied to the analysis of NAA in human plasma and in other sample types, such
as red blood cells, urine, cultured cells, cerebrospinal fluid, saliva and vitreous humor, thus avoiding the typical limitations
of other methods, which are normally suitable for use with only one or two matrix types. 相似文献
199.
Angelo Zinellu Valeria Pasciu Salvatore Sotgia Bastianina Scanu Fiammetta Berlinguer Giovanni Leoni Sara Succu Ignazio Cossu Eraldo Sanna Passino Salvatore Naitana Luca Deiana Ciriaco Carru 《Analytical and bioanalytical chemistry》2010,398(5):2109-2116
We describe a new capillary electrophoresis laser-induced fluorescence (CE-LIF) method for the quantification of adenosine 5′-triphosphate (ATP) in spermatozoa and oocytes. The optimization of the precapillary derivatization reaction between ATP and 4,4-difluoro-5,7-dimethyl-4-bora-3a,4adiaza-s-indacene-3-propionyl ethylene diamine hydrochloride (BODIPY FL EDA) has been described. BODIPY-ATP conjugate was analysed in an uncoated fused silica capillary of 75 μm ID and 50 cm effective length using a 10 mmol/L tribasic sodium phosphate buffer, pH 11.5, at 22 kV in <5 min. A good reproducibility of intra- and inter-assay tests was obtained (CV?=?4.55% and 7.14%, respectively). With respect to our previous CE-UV assay, the new method showed an improvement in sensitivity that was about 120-fold (limit of quantification, 0.15 vs 18 μmol/L). Method applicability was proven on the reproductive cells of several animal species (roosters, horses, sheep and goats). Due to the elevated sensitivity, the new assay allows the measurement of adenosine 5′-triphosphate levels from just 20 oocytes. Considering that ATP concentration in reproductive cells is related to the mitochondrial integrity after cryopreservation, the proposed method could be a useful tool in assisted reproductive technologies. 相似文献
200.
Integration of self-assembled three-dimensional photonic crystals onto structured silicon wafers 总被引:2,自引:0,他引:2
Ye J Zentel R Arpiainen S Ahopelto J Jonsson F Romanov SG Sotomayor Torres CM 《Langmuir : the ACS journal of surfaces and colloids》2006,22(17):7378-7383
We report on the fabrication of high-quality opaline photonic crystals from large silica spheres (diameter of 890 nm), self-assembled in hydrophilic trenches of silicon wafers by using a novel technique coined a combination of "lifting and stirring". The achievements reported here comprise a spatial selectivity of opal crystallization without special treatment of the wafer surface, a filling of the trenches up to the top, leading to a spatially uniform film thickness, particularly an absence of cracks within the size of the trenches, and finally a good 3D order of the opal lattice even in trenches with a complex confined geometry, verified using optical measurements. The opal lattice was found to match the pattern precisely in width as well as depth, providing an important step toward applications of opals in integrated optics. 相似文献