全文获取类型
收费全文 | 147篇 |
免费 | 1篇 |
专业分类
化学 | 105篇 |
晶体学 | 2篇 |
力学 | 1篇 |
数学 | 14篇 |
物理学 | 26篇 |
出版年
2023年 | 2篇 |
2022年 | 5篇 |
2021年 | 10篇 |
2020年 | 3篇 |
2019年 | 2篇 |
2018年 | 3篇 |
2017年 | 3篇 |
2016年 | 4篇 |
2015年 | 2篇 |
2014年 | 2篇 |
2013年 | 13篇 |
2012年 | 6篇 |
2011年 | 7篇 |
2010年 | 2篇 |
2009年 | 5篇 |
2008年 | 6篇 |
2007年 | 7篇 |
2006年 | 3篇 |
2005年 | 6篇 |
2004年 | 4篇 |
2003年 | 3篇 |
2002年 | 4篇 |
2001年 | 1篇 |
2000年 | 3篇 |
1997年 | 2篇 |
1996年 | 1篇 |
1995年 | 5篇 |
1994年 | 3篇 |
1993年 | 2篇 |
1991年 | 2篇 |
1990年 | 3篇 |
1988年 | 4篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1983年 | 6篇 |
1982年 | 2篇 |
1980年 | 3篇 |
1979年 | 2篇 |
1970年 | 1篇 |
1968年 | 1篇 |
1967年 | 1篇 |
1937年 | 1篇 |
排序方式: 共有148条查询结果,搜索用时 500 毫秒
81.
Keul HA Ryu HJ Möller M Bockstaller MR 《Physical chemistry chemical physics : PCCP》2011,13(30):13572-13578
The relevance of anion structure on the shape regulating effect of 3-ethyl-1-methylimidazolium-based ionic liquids during the seed-induced growth of gold nanocrystals is evaluated for the particular case of lactate, acetate, methylsulfate, ethylsulfate and tosylsulfonate anion systems. Carboxylate-based anions (lactate and acetate) are found to inhibit the reduction of the gold precursor salt presumably due to the deprotonation of the reducing agent ascorbic acid. The formation of non-uniform, 'head-tail'-type anisotropic particle structures is observed in both methyl- and ethylsulfate anion systems whereas rapid precipitation is observed in the case of tosylsulfonate anions. The particular efficiency of the ethylsulfate solvent system in promoting shape anisotropic growth is interpreted to be a consequence of both reduced anion/cation interactions that act to support the coordination of imidazolium to the metal surface and the enhanced capacity of anions to participate in the particle stabilization process. 相似文献
82.
Self-diffusion of component atoms and ‘order–order’ relaxations in a B2-ordering binary system AB showing a tendency for triple-defect formation were consistently simulated by means of two Monte Carlo techniques. In view of a strict correlation between antisite-defect and vacancy concentrations the Kinetic Monte Carlo (KMC) simulations were implemented with a temperature-dependent vacancy concentration determined by means of Semi-Grand Canonical Monte Carlo (SGCMC) simulations. The Ising model of the system was completed with local-configuration-dependent saddle-point energy parameters related to vacancy mediated atomic jumps. The simulations elucidated the atomistic origin of the experimentally observed low rate of ‘order–order’ relaxations in NiAl, as well as reproduced the experimental relation between the activation energies for ‘order–order’ kinetics and Ni self-diffusion in NiAl. Higher value of the deduced activation energy for atomic migration with respect to the effective energy barriers related to individual atomic jumps indicated their high correlation. 相似文献
83.
Doyle Britton John R. Sowa Kent R. Mann 《Acta Crystallographica. Section C, Structural Chemistry》2004,60(6):o418-o420
p‐Decylphenyl isocyanide, p‐C10H21–C6H4–NC or C17H25N, and p‐decylbenzonitrile, p‐C10H21–C6H4–CN or C17H25N, are isomorphous. The molecules lie in mirror planes, with the C6 rings perpendicular to the mirror. The packing of both molecules includes an aliphatic region, with close to ideal packing of the C10H21 chains, and an aromatic region, with phenyl ring–CN interactions. In addition, the CN ends of the molecules are also involved in a CN⋯NC dipolar interaction. 相似文献
84.
Shu‐Qin Liu Hisashi Konaka Takayoshi Kuroda‐Sowa Gui‐Ling Ning Megumu Munakata 《Acta Crystallographica. Section C, Structural Chemistry》2005,61(4):m194-m196
In the title complex, [Ag2(C7H4NO4)2(C16H16S2)], each AgI atom is trigonally coordinated by one S atom of a 2,11‐dithia[3.3]paracyclophane (dtpcp) ligand, and by one N and one O atom of a 6‐carboxypyridine‐2‐carboxylate ligand. Dtpcp acts as a bidentate ligand, bridging two inversion‐related AgI atoms to give a dinuclear silver(I) compound. The dinuclear moieties are interconnected via O—H·O hydrogen bonds to form a two‐dimensional zigzag sheet. Two such sheets are interwoven viaπ–π interactions between pyridine rings, affording an interwoven bilayer network. 相似文献
85.
Alkylated Aromatic Thioethers with Aggregation‐Induced Emission Properties—Assembly and Photophysics
Steffen Riebe Marco Saccone Jacqueline Stelzer Andrea Sowa Christoph Wlper Kateryna Soloviova Cristian A. Strassert Michael Giese Jens Voskuhl 《化学:亚洲杂志》2019,14(6):814-820
In this contribution, we present the synthesis and self‐assembly of alkylated thioethers with interesting photophysical properties. To this end, the emission, absorption and excitation spectra in organic solvents and as aggregates in water were measured as well as the corresponding photoluminescence quantum yields and lifetimes. The aggregates in aqueous media were visualized and measured using transmission electron microscopy. Besides that, crystal structures of selected compounds allowed a detailed discussion of the structure–property relationship. Furthermore, the mesomorphic behavior was investigated using polarized optical microscopy (POM) as well as differential scanning calorimetry (DSC). 相似文献
86.
87.
In a deuterium plasma with an electron density of 2.8 × 1013 cm-3 and an electron temperature of 1850 K, the n = 2 level is coupled to the n = 6 level by absorption of short-pulsed laser light. Due to inelastic and superelastic electron collisions, the enhanced n = 6 population density is distributed to its neighbouring levels, i.e., n = 5 and n = 7. The laser-resonance fluorescences of the Balmer lines D5, D6, and D7 were measured with time resolution. The transient behaviour of the fluorescence is compared with numerical calculations, which are based on the rate equations for population densities of a system with 5 states. It is observed that the rate coefficients of Johnson cannot explain our experimental data. The coefficients of Vriens and Smeets compare favourably with the measurements within experimental errors. 相似文献
88.
Summary Increasing amounts of large climate data require new analysis techniques. The area of data mining investigates new paradigms
and methods including factors like scalability, flexibility and problem abstraction for large data sets. The field of visual
data mining in particular offers valuable methods for analyzing large amounts of data intuitively. In this paper we describe
our approach of integrating cluster analysis and visualization methods for the exploration of climate data. We integrated
cluster algorithms, appropriate visualization techniques and sophisticated interaction paradigms into a general framework. 相似文献
89.
Polyol-induced extraction (PIE) is applied to the extraction of essential oils, using glycerol as a mass separating agent. In 1:1 acetonitrile (ACN)/water solvent mixtures, two immiscible phases can be generated. PIE as an alternative extraction technique was assessed by the extraction of the main flavor and fragrance compounds that comprise six essential oils. In the extraction of eugenol (4-allyl-2-methoxyphenol) from clove buds, the partition coefficients were determined and the % recovery and thermodynamic data in the temperature range of ?20 to 20°C were calculated. The main components present in each essential oil extract were identified through gas chromatography/mass spectrometry (GC/MS) and the compositional profile was compared to traditional extraction techniques. The optimized extraction conditions (?10°C, 1:1 ACN/water (v/v), 20% glycerol) for eugenol at ?10°C give a partition coefficient (KPC) of 87 and an extraction efficiency of 97% in the acetonitrile-rich phase. The eugenol migration to the organic phase is a spontaneous process (ΔG°?=??9.3?kJ/mol) and an endothermic process (ΔH°?=?9.2?kJ/mol) with entropy being the driving force behind the reaction (ΔS°?=?70?J/K, TΔS°?=?18.4?kJ). The technique was applied to five other essential oils (cinnamon bark, caraway seed, spearmint leaf, peppermint leaf, and anise seed oils) with similar results. 相似文献
90.
A simple method for the extraction of carotenoid pigments from frozen wet cells of red yeasts (Basidiomycota) and their analysis by reversed-phase HPLC using a C(18) column and a water/acetone solvent system is described. Typical red yeast carotenoids belonging to an oxidative series from the monocyclic gamma-carotene to 2-hydroxytorularhodin and from the bicyclic beta-carotene to astaxanthin were separated. Pigment identity was confirmed by LC-atmospheric pressure chemical ionisation (APCI) mass spectrometry using similar chromatographic conditions. 相似文献