全文获取类型
收费全文 | 253篇 |
免费 | 24篇 |
国内免费 | 25篇 |
专业分类
化学 | 197篇 |
晶体学 | 3篇 |
力学 | 42篇 |
综合类 | 2篇 |
数学 | 12篇 |
物理学 | 46篇 |
出版年
2024年 | 2篇 |
2023年 | 15篇 |
2022年 | 24篇 |
2021年 | 22篇 |
2020年 | 16篇 |
2019年 | 16篇 |
2018年 | 18篇 |
2017年 | 7篇 |
2016年 | 18篇 |
2015年 | 9篇 |
2014年 | 10篇 |
2013年 | 10篇 |
2012年 | 14篇 |
2011年 | 17篇 |
2010年 | 10篇 |
2009年 | 7篇 |
2008年 | 9篇 |
2007年 | 12篇 |
2006年 | 13篇 |
2005年 | 7篇 |
2004年 | 3篇 |
2003年 | 6篇 |
2002年 | 4篇 |
2001年 | 1篇 |
2000年 | 5篇 |
1999年 | 2篇 |
1998年 | 3篇 |
1997年 | 1篇 |
1996年 | 8篇 |
1995年 | 4篇 |
1994年 | 2篇 |
1993年 | 1篇 |
1992年 | 2篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1957年 | 1篇 |
排序方式: 共有302条查询结果,搜索用时 0 毫秒
1.
Tuning the Basicity of Cyano‐Containing Ionic Liquids to Improve SO2 Capture through Cyano–Sulfur Interactions 下载免费PDF全文
Dr. Guokai Cui Fengtao Zhang Xiuyuan Zhou Prof. Haoran Li Prof. Jianji Wang Prof. Congmin Wang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(14):5632-5639
A new approach has been developed to improve SO2 sorption by cyano‐containing ionic liquids (ILs) through tuning the basicity of ILs and cyano–sulfur interaction. Several kinds of cyano‐containing ILs with different basicity were designed, prepared, and used for SO2 capture. The interaction between these cyano‐containing ILs and SO2 was investigated by FTIR and NMR methods. Spectroscopic investigations and quantum chemical calculations showed that dramatic effects on SO2 capacity originate from the basicity of the ILs and enhanced cyano–sulfur interaction. Furthermore, the captured SO2 was easy to release by heating or bubbling N2 through the ILs. This efficient and reversible process, achieved by tuning the basicity of ILs, is an excellent alternative to current technologies for SO2 capture. 相似文献
2.
Amide-water mixtures are studied by all-atom molecular dynamics (MD) simulations and the relative temperature-dependent NMR experiment. The weak C-H...O contacts are found in the amide-water systems theoretically and experimentally. The statistical results of the average numbers of hydrogen bonds indicate that the methyl groups in amide molecules represent different capabilities in forming the weak C-H...O contacts. The statistics also imply that the C-H...O contacts are more obvious in the amide-rich region than those in the water-rich region. The temperature-dependent NMR spectra are also adopted to investigate the weak C-H...O contacts in the amide-water systems. The relative chemical shifts of the methyl groups are in good agreement with the MD simulations. 相似文献
3.
Chemical shifts of the alcohol and DMF protons in DMF–alcohol mixtures with the mole fraction of alcohol are reported in order to study the hydrogen bond interaction present in the mixtures. The densities of DMF–methanol mixture at 22°C are also measured. Excess volumes and excess chemical shifts are correlated by the Redlich–Kister equation. The relation between excess volumes and excess chemical shifts in the mixtures is discussed. It is found that the maximum excess chemical shifts E(CHO-OH) and E(CH3-OH) are positioned at about mole fraction methanol = 0.57 for the DMF–methanol system, as is V
E. The results show that the NMR spectral method offers a valuable approach to similar future studies of interactions in mixtures. 相似文献
4.
An all-atom dimethyl sulfoxide (DMSO) model and a TIP5P water model have been adopted for molecular dynamics simulation. Two new qualities ηrelE and ηrel are introduced to describe the anomalous nonideal behaviors of DMSO–water mixtures. The simulation is compared with chemical shift and excess enthalpy of mixing, which shows good concentration dependences. In addition, our all-atom simulation also indicates that the C–H groups of DMSO may interact with the oxygen atoms of water and DMSO. The weak C–HO contacts and the strong O–HO hydrogen bonds represent the consistent concentration dependences, which exhibits the cooperation effect. 相似文献
5.
Compared to the general ionic liquids (ILs), a significant deviation of the binary mixtures of 1-decyl-3-methylimidazolium tri(hexafluoroacetylaceto)-copper(II) ([C10mim][Cu(hfacac)3]) with methanol was found, indicating the way methanol interacts with ILs might be governed by the special structure of the chelating anion. IR results showed that the (C2-H) of 1-decyl-3-methylimidazolium hexafluoroacetylacetonate ([C10mim][hfacac]) blue-shifted more significantly than that of [C10mim][Cu(hfacac)3], meanwhile the (C=O) red-shifted in [C10mim][Cu(hfacac)3], which is contrast with that in [C10mim][hfacac]. Two-dimensional correlation analysis of the FTIR spectra indicated that the chelating cavity has little effect on the sequence of the ILs sites that interact with methanol. Combined with small angle X-ray scattering (SAXS) results, the picture of mixing processes in these two systems were proposed. Methanol interacts directly with the anion followed by the cation in [C10mim][hfacac], while methanol preferentially enters the chelating cavity and enhances the packing effect in the [C10mim][Cu(hfacac)3] system. 相似文献
6.
Polymer nanodielectrics render a great material platform for exhibiting the intrinsic nature of incorporated particles, particularly semiconducting types, and their interfaces with the polymer matrix. Incorporating the oxide fillers with higher loading percentages (>40 vol%) encounters particular challenges in terms of dispersion, homogeneous distribution, and porosity from the process. This work investigated the dielectric loss and electrical conduction behaviors of composites containing semiconducting ZnO varistor particles of various concentrations using the epoxy impregnation method. The ZnO varistor particles increased the dielectric permittivity, loss, and electrical conductivity of the epoxy composites into three different regimes (0–50 vol%, 50–70 vol%, 70–100 vol%), particularly under an electric bias field or at higher temperatures. For lower loading fractions below 50 vol%, the dielectric responses are dominated by the insulating epoxy matrix. When loading fractions are between 50 and 70 vol%, the dielectric and electric responses are mostly associated with the semiconducting interfaces of ZnO varistor particles and ZnO–epoxy. At above 70 vol%, the apparent increase in the dielectric loss and conductivity is primarily associated with the conducting ZnO core forming the interconnected channels of electric conduction. The foam-agent-assisted ZnO varistor particle framework appears to be a better way of fabricating composites of filler loading above 80 vol%. A physical model using an equivalent capacitor, diode, and resistor in the epoxy composites was proposed to explain the different property behaviors. 相似文献
7.
Zheng Yuanzhou Yang Haoran Mazaheri Hossein Aghaei Alireza Mokhtari Namjoo Afrand Masoud 《Journal of Thermal Analysis and Calorimetry》2021,143(2):1425-1438
Journal of Thermal Analysis and Calorimetry - The purpose of this study is to numerically investigate flow field and turbulent heat transfer of hybrid nanofluid, water–DWCNT–TiO2 in a... 相似文献
8.
Dr. Qian Li Gang Liu Haoran Cheng Dr. Qujiang Sun Prof. Junli Zhang Prof. Jun Ming 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(64):15842-15865
Lithium-ion batteries have dominated the energy market from portable electronic devices to electric vehicles. However, the LIBs applications are limited seriously when they were operated in the cold regions and seasons if there is no thermal protection. This is because the Li+ transportation capability within the electrode and particularly in the electrolyte dropped significantly due to the decreased electrolyte liquidity, leading to a sudden decline in performance and short cycle-life. Thus, design a low-temperature electrolyte becomes ever more important to enable the further applications of LIBs. Herein, we summarize the low-temperature electrolyte development from the aspects of solvent, salt, additives, electrolyte analysis, and performance in the different battery systems. Then, we also introduce the recent new insight about the cation solvation structure, which is significant to understand the interfacial behaviors at the low temperature, aiming to guide the design of a low-temperature electrolyte more effectively. 相似文献
9.
The structures and conformational properties of 1-alkyl-3-methylimidazolium halide ionic liquids have been studied with a Becke's 3 Parameter functional method. The interaction mechanisms between the cation and the anion in 1-ethyl-3-methylimidazolium (Emim+) halide and 1-butyl-3-methylimidazolium (Bmim+) halide ionic liquids were investigated using 6-31G*, 6-31++G**, and 6-311++G** basis sets. Forty structures of different ion pairs were optimized and geometrical parameters of them have been discussed in details. Halide ions (Cl- or Br-) have been gradually placed in different regions around imidazolium cation and the interaction energies between the anion and the cation have been calculated. Theoretical results indicate that there are four activity regions in the vicinity of the imidazolium cations, in these regions the imidazolium cations and the halide anions formed stable ion pairs. Imidazolium cations can form hydrogen bond interactions with one, two or three but no more than three nearest halide anions. The halide ions are situated in hydrogen bond positions rather than at random. 相似文献
10.