全文获取类型
收费全文 | 150篇 |
免费 | 8篇 |
国内免费 | 1篇 |
专业分类
化学 | 106篇 |
晶体学 | 4篇 |
力学 | 1篇 |
数学 | 27篇 |
物理学 | 21篇 |
出版年
2023年 | 5篇 |
2022年 | 5篇 |
2021年 | 11篇 |
2020年 | 10篇 |
2019年 | 12篇 |
2018年 | 5篇 |
2017年 | 5篇 |
2016年 | 12篇 |
2015年 | 6篇 |
2014年 | 6篇 |
2013年 | 9篇 |
2012年 | 14篇 |
2011年 | 9篇 |
2010年 | 5篇 |
2008年 | 9篇 |
2007年 | 11篇 |
2006年 | 4篇 |
2005年 | 6篇 |
2004年 | 5篇 |
2003年 | 1篇 |
2002年 | 1篇 |
2001年 | 1篇 |
2000年 | 2篇 |
1997年 | 1篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1986年 | 2篇 |
排序方式: 共有159条查询结果,搜索用时 23 毫秒
1.
2.
ABSTRACTAmino acid derived macrocycles with elaborate well-defined stereochemistry are a unique class of compounds that have been isolated from natural sources. Macrocycles like cyclosporine, octreotide, and valinomycin have been used in multiple applications, like drugs or ion sensors. Chemists have long been fascinated by the unique molecular recognition capabilities of these macrocycles and tried to design synthetic analogs with similar functions. This article is focused on reviewing current research on amide and amino acid containing macrocycles that have been developed in research laboratories for biological recognition, specifically for anion sensing, ion transport, carbohydrate sensing, and peptide sensing. 相似文献
3.
4.
5.
利用可再生清洁能源将CO2转化为CO和其他小分子是合成含碳燃料的可观方法之一。间歇性可再生能源存储的重要策略之一是将二氧化碳进行电化学还原。选择具有高活性和稳定性的电催化剂对于电化学还原CO2至关重要。在这项研究中,我们使用简单的电沉积方法合成了具有纳米晶枝状结构的CuAu合金电极。各项表征显示原子比约为1:1的CuAu纳米枝晶对CO2的电化学还原具有出色的催化活性。合成的主要产物是H2和CO,这是合成气体是合成天然气,氨和甲醇合成的中间体。电化学阻抗谱(EIS)测量表明,相对于Cu和Au电沉积催化剂,CuAu纳米晶枝状催化剂具有相对低的电荷转移阻力。CuAu纳米枝晶催化剂是一种具有潜在的转化CO2为合成气体的高活性电催化剂。 相似文献
6.
Polarised neutron diffraction experiments conducted at 4.2 K on Cs(3)CoCl(5) crystals have been analysed by using a four-dimensional model Hilbert space made of ab initio n-electron wave functions of the CoCl(4) (2-) molecular ion. Two spin-orbit mixing coefficients and several configuration interaction coefficients have been optimized by fitting calculated magnetic structure factors to experimental ones, to obtain the best ensemble density operator that is representable in the model space. A goodness of fit, χ(2), less then 1 has been obtained for the first time for the two experimental data sets available. In the present article, the optimized density operators are used to calculate the magnetic field densities that are the genuine observables probed in neutron diffraction experiments. Density maps of such observables are presented for the first time and numerical details are provided. The respective contributions of spin density and orbital current to the magnetic field density are analyzed. 相似文献
7.
Henry W. Orton Dr. Jan Stanek Dr. Tobias Schubeis Dylan Foucaudeau Claire Ollier Dr. Adrian W. Draney Dr. Tanguy Le Marchand Dr. Diane Cala-De Paepe Prof. Dr. Isabella C. Felli Prof. Dr. Roberta Pierattelli Prof. Dr. Sebastian Hiller Dr. Wolfgang Bermel Dr. Guido Pintacuda 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(6):2400-2405
8.
David K. Geiger Dylan E. Parsons 《Acta Crystallographica. Section C, Structural Chemistry》2014,70(7):681-688
The structures of 4‐nitrobenzene‐1,2‐diamine [C6H7N3O2, (I)], 2‐amino‐5‐nitroanilinium chloride [C6H8N3O2+·Cl−, (II)] and 2‐amino‐5‐nitroanilinium bromide monohydrate [C6H8N3O2+·Br−·H2O, (III)] are reported and their hydrogen‐bonded structures described. The amine group para to the nitro group in (I) adopts an approximately planar geometry, whereas the meta amine group is decidedly pyramidal. In the hydrogen halide salts (II) and (III), the amine group meta to the nitro group is protonated. Compound (I) displays a pleated‐sheet hydrogen‐bonded two‐dimensional structure with R22(14) and R44(20) rings. The sheets are joined by additional hydrogen bonds, resulting in a three‐dimensional extended structure. Hydrohalide salt (II) has two formula units in the asymmetric unit that are related by a pseudo‐inversion center. The dominant hydrogen‐bonding interactions involve the chloride ion and result in R42(8) rings linked to form a ladder‐chain structure. The chains are joined by N—H...Cl and N—H...O hydrogen bonds to form sheets parallel to (010). In hydrated hydrohalide salt (III), bromide ions are hydrogen bonded to amine and ammonium groups to form R42(8) rings. The water behaves as a double donor/single acceptor and, along with the bromide anions, forms hydrogen bonds involving the nitro, amine, and ammonium groups. The result is sheets parallel to (001) composed of alternating R55(15) and R64(24) rings. Ammonium N—H...Br interactions join the sheets to form a three‐dimensional extended structure. Energy‐minimized structures obtained using DFT and MP2 calculations are consistent with the solid‐state structures. Consistent with (II) and (III), calculations show that protonation of the amine group meta to the nitro group results in a structure that is about 1.5 kJ mol−1 more stable than that obtained by protonation of the para‐amine group. DFT calculations on single molecules and hydrogen‐bonded pairs of molecules based on structural results obtained for (I) and for 3‐nitrobenzene‐1,2‐diamine, (IV) [Betz & Gerber (2011). Acta Cryst. E 67 , o1359] were used to estimate the strength of the N—H...O(nitro) interactions for three observed motifs. The hydrogen‐bonding interaction between the pairs of molecules examined was found to correspond to 20–30 kJ mol−1. 相似文献
9.
Hang Kuen Lau Shruti Rattan Hongbo Fu Cristobal G. Garcia Dylan M. Barber Kristi L. Kiick Alfred J. Crosby 《Macromolecular bioscience》2020,20(5)
Local, micromechanical environment is known to influence cellular function in heterogeneous hydrogels, and knowledge gained in micromechanics will facilitate the improved design of biomaterials for tissue regeneration. In this study, a system comprising microstructured resilin‐like polypeptide (RLP)–poly(ethylene glycol) (PEG) hydrogels is utilized. The micromechanical properties of RLP‐PEG hydrogels are evaluated with oscillatory shear rheometry, compression dynamic mechanic analysis, small‐strain microindentation, and large‐strain indentation and puncture over a range of different deformation length scales. The measured elastic moduli are consistent with volume averaging models, indicating that volume fraction, not domain size, plays a dominant role in determining the low strain mechanical response. Large‐strain indentation under a confocal microscope enables the visualization of the microstructured hydrogel micromechanical deformation, emphasizing the translation, rotation, and deformation of RLP‐rich domains. The fracture initiation energy results demonstrate that failure of the composite hydrogels is controlled by the RLP‐rich phase, and their independence with domain size suggested that failure initiation is controlled by multiple domains within the strained volume. This approach and findings provide new quantitative insight into the micromechanical response of soft hydrogel composites and highlight the opportunities in employing these methods to understand the physical origins of mechanical properties of soft synthetic and biological materials. 相似文献
10.
Lukáš Bučinský Stanislav Biskupič Dylan Jayatilaka 《Theoretical chemistry accounts》2011,129(2):181-197
The 2nd order Douglas-Kroll-Hess (DKH2) and the Infinite Order Two Component (IOTC) radial distributions of electron density
of canonical Hartree-Fock (HF) orbitals of radon atom are presented. Furthermore, the total electron density is revisited.
The picture change error (PCE) correction is investigated by analytical means. The point charge model of nucleus and the Gaussian
nucleus model are employed. The basis set is extrapolated by means of including tight s and also p Gaussians within the original triple zeta basis set. It is found that the DKH1 PCE corrected DKH2 total electron and s orbital contact densities are negative for the point charge model of nucleus if tight enough s Gaussians are included in the basis set. It is shown that this failure is caused due to the missing terms of the second order
Douglas-Kroll transformation for the DKH2 electron density. PCE is found the most striking in the DKH2/IOTC electron density
of s orbitals close to the nucleus. The radial distributions of the 2-component p
1/2 orbital densities are considerably affected by PCE at the nucleus as well. Furthermore, the PCE corrected DKH2/IOTC scalar
p orbital densities have a non-zero value of electron density at nucleus and can be considered as an spin-orbit (SO) average
of the p
1/2 and p
3/2 orbitals. The d and f orbitals are affected by PCE in the vicinity of the nucleus only little. The PCE corrected DKH2 and IOTC radial distributions
of orbital densities are nodeless, which is completely in agreement with the radial distribution of the analytic or numeric
DCH orbital densities. 相似文献