全文获取类型
收费全文 | 356篇 |
免费 | 14篇 |
国内免费 | 2篇 |
专业分类
化学 | 272篇 |
晶体学 | 3篇 |
力学 | 9篇 |
数学 | 60篇 |
物理学 | 28篇 |
出版年
2023年 | 5篇 |
2022年 | 10篇 |
2021年 | 22篇 |
2020年 | 19篇 |
2019年 | 8篇 |
2018年 | 8篇 |
2017年 | 13篇 |
2016年 | 10篇 |
2015年 | 17篇 |
2014年 | 14篇 |
2013年 | 14篇 |
2012年 | 20篇 |
2011年 | 28篇 |
2010年 | 20篇 |
2009年 | 11篇 |
2008年 | 30篇 |
2007年 | 22篇 |
2006年 | 14篇 |
2005年 | 19篇 |
2004年 | 14篇 |
2003年 | 14篇 |
2002年 | 11篇 |
2001年 | 6篇 |
2000年 | 4篇 |
1999年 | 4篇 |
1998年 | 2篇 |
1997年 | 2篇 |
1996年 | 3篇 |
1993年 | 2篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1974年 | 1篇 |
排序方式: 共有372条查询结果,搜索用时 15 毫秒
171.
Marianna Čierniková Petra Balážová Alfonz Plško Petr Exnar Jana Pagáčová Iveta Papučová 《Journal of Sol-Gel Science and Technology》2018,88(3):497-507
The presented study deals with relation between chemical composition of precursor sols and surface free energy of inorganic-organic films. Inorganic-organic films were prepared from precursor sols in “tetraethoxysilane (TEOS) - triethoxy(octyl)silane (OTES) - distilled water - nitric acid - isopropyl alcohol” system. The fifteen sols were prepared, where the ratio of K?=?x(OTES)/(x(TEOS)?+?x(OTES)) varied from 0 to 0.5 and ratio of R?=?x(H2O)/(x(TEOS)?+?x(OTES)) varied from 2 to 6. The relationship between chemical composition and surface free energy of inorganic-organic films was quantified by model selection approach. Model, which describes the studied relationship in the best way, was selected on the basis of Akaike information criterion. Based on the analysis of selected (the best describing) model, it was found out that the surface free energy as well as its dispersion and polar component are dependent only on K ratio in observed range of K and R values. Form the physico-chemical aspect, the observed dependences of surface free energy, its dispersive and polar component on chemical composition of precursor sols are explained by the influence of octyl groups on the sequences of hydrolysis and condensation reactions leading to formation of particles in precursor sol. In addition, the arrangement of octyl groups is used for explanation of particles arrangement on film surface. 相似文献
172.
Study of the thermodynamics and mass transfer kinetics of two enantiomers on a polymeric imprinted stationary phase 总被引:4,自引:0,他引:4
Peter Sajonz Marianna Kele Guoming Zhong Brje Sellergren Georges Guiochon 《Journal of chromatography. A》1998,810(1-2):1-17
The adsorption isotherms of
- and
-phenylalanine anilide (PA) on an
-phenylalanine anilide imprinted stationary phase have been determined using staircase frontal analysis. An aqueous buffer–organic solvent mixture has been used as mobile phase. The measurements were done at temperatures of 40, 50, 60 and 70°C for sample concentrations ranging between 5·10−4 to 1 g/l. It was found that the adsorption data fit well to both the Freundlich and the Bi-Langmuir isotherm models. Examination of the best values of the numerical coefficients of the Bi-Langmuir model shows that the site class representing the binding sites with the highest binding energy exhibits a very low saturation capacity for the non-imprinted enantiomer, indicating a high selectivity for the imprinted
-enantiomer. The low energy site class also shows some selectivity for the
-enantiomer. Mass transfer rate coefficients were obtained for each single breakthrough curve by using the transport model of chromatography. It was found that the mass transfer coefficient of
-PA increases very rapidly with the sample concentration while there is only a slight increase for the other enantiomer. 相似文献
Full-size image
Full-size image
Full-size image
Full-size image
Full-size image
Full-size image
173.
Li X Wettig SD Wang C Foldvari M Verrall RE 《Physical chemistry chemical physics : PCCP》2005,7(17):3172-3178
Gemini surfactants 18:1-s-18:1, where s = 2, 3, and 6 methylene groups and 18:1 refers to oleyl carbon chains, have been synthesized, characterized and a number of micelle solution properties measured by using electrical conductance, fluorescence probe emission, light scattering (DLS), surface tension and isothermal titration calorimetry (ITC) methods at 25 degrees C. The cmc values of 18:1-2-18:1, 18:1-3-18:1, and 18:1-6-18:1 were found to be 26.9, 23.4, and 18.0 microM, respectively, using the electrical conductance method. Surface tension results suggest that in 0.01 N NaCl solutions, the s = 2 and 3 members of the series form multilayer rather than monolayer structures, while the s = 6 homologue adopts a close-packed arrangement. This is consistent with DLS and EM measurements which show vesicle formation for the s = 2 and 3 compounds, and micelle formation for the s = 6 compound. The enthalpies of micellization (deltaH degrees (M)) are more exothermic for the 18:1-s-18:1 series of surfactants, than for the 12-s-12 series. The differences are rationalized in terms of steric and configurational contributions to deltaH degrees (M) arising from difficulties associated with packing of the bulky cis-9-octadecene tails. 相似文献
174.
Marianna Pioli Nicol Orsoni Mirco Scaccaglia Rossella Alinovi Silvana Pinelli Giorgio Pelosi Franco Bisceglie 《Molecules (Basel, Switzerland)》2021,26(4)
The synthesis, photoactivation and biological activity of a new piano-stool Ru(II) complex is herein reported. The peculiarity of this complex is that its monodentate ligand which undergoes the photodissociation is an asymmetric bis-thiocarbohydrazone ligand that possesses a pyridine moiety binding to Ru(II) and the other moiety contains a quinoline that endows the ligand with the capacity of chelating other metal ions. In this way, upon dissociation, the ligand can be released in the form of a metal complex. In this article, the double ability of this new Ru(II) complex to photorelease the ligand and to chelate copper and nickel is explored and confirmed. The biological activity of this compound is studied in cell line A549 revealing that, after irradiation, proliferation inhibition is reached at very low half maximal inhibitory concentration (IC50) values. Further, biological assays reveal that the dinuclear complex containing Ni is internalized in cells. 相似文献
175.
Comprehensive structural characterization of polyisoprene synthesized via cationic mechanism
下载免费PDF全文
![点击此处可从《Journal of polymer science. Part A, Polymer chemistry》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Victor A. Rozentsvet Nelly A. Korovina Olesya A. Stotskaya Marianna G. Kuznetsova Frederic Peruch Sergei V. Kostjuk 《Journal of polymer science. Part A, Polymer chemistry》2016,54(15):2430-2442
The microstructure of polyisoprene synthesized with tBuCl/TiCl4 initiating system is investigated using 1D and 2D (HSQC and HMBC) NMR spectroscopy. It is found that trans‐1,4‐units with regular (head‐to‐tail) and inverse (tail‐to‐tail) and (head‐to‐head) enchainments are predominant structures of unsaturated part of polymer chain, while 1,2‐ and 3,4‐units are presented in minor amounts. The new methodology for the quantitative calculation of the content of different structural units in polyisoprene chain including both types of inverse trans‐1,4‐addition (tail‐to‐tail and head‐to‐head) is proposed. It is shown that head groups consist of tert‐butyl group connected to trans‐1,4‐unit of polyisoprene chain. In addition, two types of chlorine‐containing end groups are found (trans‐4,1‐Cl and 4,3‐Cl), while conjugated double bonds at the chain end are totally absent. The methodology for the calculation of number‐average functionality by tert‐butyl head and chlorine end groups, respectively, is developed. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 2430–2442 相似文献
176.
177.
178.
Marianna Bolla 《Discrete Mathematics》2008,308(18):4221-4230
Spectra and representations of some special weighted graphs are investigated with weight matrices consisting of homogeneous blocks. It is proved that a random perturbation of the weight matrix or that of the weighted Laplacian with a “Wigner-noise” will not have an effect on the order of the protruding eigenvalues and the representatives of the vertices will unveil the underlying block-structure.Such random graphs adequately describe some biological and social networks, the vertices of which belong either to loosely connected strata or to clusters with homogeneous edge-densities between any two of them, like the structure guaranteed by the Regularity Lemma of Szemerédi. 相似文献
179.
180.