全文获取类型
收费全文 | 114篇 |
免费 | 12篇 |
专业分类
化学 | 95篇 |
力学 | 6篇 |
数学 | 11篇 |
物理学 | 14篇 |
出版年
2023年 | 1篇 |
2022年 | 4篇 |
2021年 | 3篇 |
2020年 | 5篇 |
2019年 | 5篇 |
2018年 | 6篇 |
2017年 | 1篇 |
2016年 | 12篇 |
2015年 | 8篇 |
2014年 | 3篇 |
2013年 | 11篇 |
2012年 | 11篇 |
2011年 | 10篇 |
2010年 | 10篇 |
2009年 | 4篇 |
2008年 | 7篇 |
2007年 | 5篇 |
2006年 | 3篇 |
2005年 | 4篇 |
2003年 | 2篇 |
2002年 | 2篇 |
1998年 | 1篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1980年 | 1篇 |
1978年 | 1篇 |
1977年 | 2篇 |
1943年 | 2篇 |
排序方式: 共有126条查询结果,搜索用时 109 毫秒
51.
52.
Clever GH Kawamura W Tashiro S Shiro M Shionoya M 《Angewandte Chemie (International ed. in English)》2012,51(11):2606-2609
Neatly wrapped up: alternately stacked square-planar platinum(II) complexes inside a dinuclear coordination cage were prepared to give a discrete and soluble Pt(5) -array of the Magnus' salt type. Characterization of the complex in solution was complemented by an X-ray crystal structure of {[Pt(pyridine)(4)]? [PtCl(4)](2) @Cage}; this structure showed the linear, pentanuclear array within the cages and their circular packing into a hollow tubular superstructure. 相似文献
53.
Guilherme F. de Arruda Thomas Kauê Dal’Maso Peron Marinho Gomes de Andrade Jorge Alberto Achcar Francisco Aparecido Rodrigues 《Journal of statistical physics》2013,152(3):519-533
The influence of the network structure on the emergence of collective dynamical behavior is an important topic of research that has not been fully understood yet. In the current work, it is shown how statistical regression analysis can be considered to address this issue. The regression model proposed suggests that the average shortest path length is the network property most influencing the degree of synchronization of Kuramoto oscillators. Moreover, this model revealed to be very accurate, being the predicted and measured values of synchronization highly correlated. Therefore, the regression modeling allows predicting the values of the dynamic variable in terms of network structure. 相似文献
54.
55.
56.
Thorben R. Schulte Julian J. Holstein Guido H. Clever 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(17):5618-5622
Chiral nanosized confinements play a major role for enantioselective recognition and reaction control in biological systems. Supramolecular self‐assembly gives access to artificial mimics with tunable sizes and properties. Herein, a new family of [Pd2L4] coordination cages based on a chiral [6]helicene backbone is introduced. A racemic mixture of the bis‐monodentate pyridyl ligand L1 selectively assembles with PdII cations under chiral self‐discrimination to an achiral meso cage, cis‐[Pd2 L1P 2 L1M 2]. Enantiopure L1 forms homochiral cages [Pd2 L1P/M 4]. A longer derivative L2 forms chiral cages [Pd2 L2P/M 4] with larger cavities, which bind optical isomers of chiral guests with different affinities. Owing to its distinct chiroptical properties, this cage can distinguish non‐chiral guests of different lengths, as they were found to squeeze or elongate the cavity under modulation of the helical pitch of the helicenes. The CD spectroscopic results were supported by ion mobility mass spectrometry. 相似文献
57.
Eduardo Carlos Alexandrina Diego Victor Babos Daniel Fernandes Andrade Vinicius Câmara Costa Elaine Schornobay Lui Nivaldo Aparecido Corrêa 《International journal of environmental analytical chemistry》2019,99(7):653-669
Chemical composition of PM10 was studied during the period of 2014–2015 in the city of São Carlos, Brazil (‘Dos Voluntários’ Square). PM10 samples were directly analysed by wavelength dispersive X-ray fluorescence – WD-XRF (Al, Ca, Ce, Cl, Fe, K, Mg, P, S, Si, Ti, V, and Zn), and by laser-induced breakdown spectroscopy – LIBS (Ba, Ca, Fe, K, Mg, Na, Si and Ti) both for qualitative purposes. For quantitative analysis of Al, Ba, Ca, Fe, K, Na, S, and Zn, the analytes were extracted from samples of PM10 collected, in filters of glass fibre, with an extractive acid solution (HNO3 and HCl) and determined by inductively coupled plasma optical emission spectrometry – ICP OES. Spatial variations of elemental concentrations (ng m–3) were significantly higher in winter Al (19.0), Ba (13.6), Ca (20.0), Na (27.0), S (37.1), and Zn (9.5), autumn showed the highest concentration of Na (26.4), spring showed the highest concentration of Fe (11.6), K (13.1) and also S (25.3) and summer did not show a high concentration in the comparison between the seasons at the site. Using principal component analysis (PCA), as a data interpretation tool, with the data obtained by the WD-XRF and LIBS it was not possible to obtain a good correlation, but with the data of ICP OES, it was possible to verify correlations between identified and determinate elements, with samples collected in the autumn, winter, spring and summer seasons in the city of São Carlos. These associated analytical techniques were excellent tools in environmental monitoring, through the analysis of PM10 samples, presenting reliable and efficiency strategy, and based on the PCA and the EF equation was possible to draw the profile of the possible origins of these elements in the city. 相似文献
58.
Arthur V. Azevedo Aparecido J. de Souza Frederico Furtado Dan Marchesin Bradley Plohr 《Transport in Porous Media》2010,83(1):99-125
There are two goals of this study. The first is to provide an introduction to the wave curve method for finding the analytic solution of a porous medium injection problem. Similar to fractional and chromatographic flow theory, the wave curve method is based on the method of characteristics, but it is applicable to an expanded range of physical processes in porous medium flow. The second goal is to solve injection problems for immiscible three-phase flow, as described by Corey’s model, in which a mixture of gas and water is injected into a porous medium containing oil and irreducible water. In particular we determine, for any choice of the phase viscosities, the proportion of the injected fluids that maximizes recovery around breakthrough time. Numerical simulations are performed to compare our solutions for Corey’s model with those of other models. For the injection problems we consider, solutions for Corey’s model are very similar to those for Stone’s model, despite the presence of an elliptic region in the latter; and they are very different from those for the Juanes-Patzek model, which preserves strict hyperbolicity. A nice feature of our analytical method is that it facilitates explaining both differences and similarities among the solutions for the three models considered. 相似文献
59.
Fernando Aparecido Kawaguchi 《Applied Surface Science》2008,254(13):4118-4122
This study evaluated the influence of chemical vapor deposition (CVD) tips surface treatments of enamel and dentin on bonding resistance of two adhesive systems. Thirty embedded samples were divided in 12 groups (n = 10), according to factors: substrate (enamel and dentin), adhesive system [etch-and-rinse (SB) and self-etch]; and the surface treatments (paper discs, impact CVD tips and tangential CVD tip). When CVD tip was used in the impact mode the tip was applied perpendicular to dental surface, while at tangential mode, the tip worked parallel to dental surface. Specimens were tested in tension after 24 h at 0.5 mm/min of cross-head speed. ANOVA results, in MPa showed that in enamel, only adhesive system factor was statistically significant (p = 0.015) under tested conditions, with higher bond strength observed for SB groups. However, in dentin the best bonding performance was obtained in SE groups (p = 0.00). In both tested substrates, results did not show statistically significant difference for factors treatment and its interactions.
Conclusions
It may be concluded that CVD-tip surface treatment, in both tested modes, did not influence on adhesion to enamel and dentin. But, it is important to choose adhesive system according to the tissue available to bonding. 相似文献60.
H. Lawrence Clever 《Monatshefte für Chemie / Chemical Monthly》2003,359(3):745-750
There are more than 150 papers that report on the solubility of the four chloromethanes in water. Volume 62 of the Solubility
Data Series compiles and evaluates the papers concerned with the liquid–liquid solubility of the chloromethanes with water.
A similar evaluation has not been carried out for the vapor–liquid solubility at a partial pressure up to the saturation vapor
pressure of the four chloromethanes. This paper uses the liquid–liquid evaluated solubility values to calculate vapor–liquid
Henry’s constants. They are compared with a compilation of Henry’s constants with good agreements between the calculated constants and the median of the compiled constants. It is believed
that the calculated constants are a reliable set of values to use for the vapor–liquid solubility of the chloromethanes in
water. 相似文献