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91.
Anisotropy-induced quantum critical behavior of magnetite nanoparticles at low temperatures 总被引:1,自引:0,他引:1
The classical, thermally driven transition from ferrimagnets to superparamagnets in Fe3O4 nanoparticles can be converted into another quantum phase by a transverse microwave magnetic field or by a strong internal anisotropic field. These fields, perpendicular to the Ising axis, can destroy the magnetic long-range order to quantum paramagnets as the fields exceed some critical values. We have exploited the spin resonance spectrometer to determine the dynamic spin susceptibility and the critical exponent γ, which is a power-law dependent spanning of the quantum critical point. Quantum phase transition observed at low temperatures for small magnetite nanoparticles induced by strong surface anisotropic field illustrates the fascinating interplay between thermal and quantum fluctuations in the vicinity of a quantum critical point. 相似文献
92.
Franoise Humm Robert Romanetti Paul Tordo Lue Bouscasse Roger Phan-Tan-Luu 《Magnetic resonance in chemistry : MRC》1973,5(8):365-371
A non-linear regression method for the resolution of EPR spectra is described. The theoretical model is fitted with the experimental spectrum and the error on each parameter is calculated. The method is applied to the radical anions of 2-nitro-4-methyl thiazole, 4-p-nitro-phenyl-thiazole and 5-p-nitro-phenyl-thiazole. 相似文献
93.
94.
Jin‐Feng Sun Zun‐Lue Zhu Heng Ma Yu‐Fang Liu Zheng‐He Zhu 《International journal of quantum chemistry》2007,107(9):1856-1863
The SAC‐CI (symmetry‐adapted‐cluster configuration‐interaction) method presented in Gaussian 03 program package is applied to investigate the adiabatic potential energy curves (PECs) of 7Li2(b3Πu). These calculations are performed at numbers of basis sets, such as 6‐311++G(3df,3pd), 6‐311++G(2df,2pd), 6‐311++G(df,pd), D95V++, D95(3df,3pd), D95(d,p), cc‐PVTZ, 6‐311++G and 6‐311++G(d,p). All the ab initio calculated points are fitted to the analytic Murrell‐Sorbie functions and then used to compute the spectroscopic parameters. The analytic potential energy function (APEF) for this b3Πu state is reported. By comparison, the spectroscopic parameters reproduced by the APEF attained at 6‐311++G(2df,2pd) are found to be very close to the latest experimental findings. With the APEF obtained at the SAC‐CI/6‐311++G(2df,2pd) level of theory, a total of 62 vibrational states is found when J = 0. The complete vibrational levels, classical turning points, inertial rotation and centrifugal distortion constants for these vibrational states are also reported. The reasonable dissociation limit for this state is deduced using the calculated results at present. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2007 相似文献
95.
The room-temperature phosphorescence of several polyaromatic hydrocarbons (anthracene, coronene, phenanthrene, pyrene, benzo[a]pyrene) and carbazole on paper support has been investigated. Heavy-atom solvents such as silver nitrate and sodium iodide were found to have specific effects in inducing phosphorescence emission from these compounds. 相似文献
96.
We have studied the competition between helix formation and aggregation for a simple polymer model. We present simulation results for a system of two such polymers, examining the potential of mean force, the balance between intermolecular and intramolecular interactions, and the promotion or disruption of secondary structure brought on by the proximity of the two molecules. In particular, we demonstrate that proximity between two such molecules can stabilize secondary structure. However, for this model, observed secondary structure is not stable enough to prevent collapse of the system into an unstructured globule. 相似文献
97.
Chiral Iodine‐Catalyzed Dearomatizative Spirocyclization for the Enantioselective Construction of an All‐Carbon Stereogenic Center
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Dong‐Yang Zhang Lue Xu Hua Wu Prof. Dr. Liu‐Zhu Gong 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(29):10314-10317
The first enantioselective dearomatizative spirocyclization of 1‐hydroxy‐N‐aryl‐2‐naphthamide derivatives has been accomplished by chiral organoiodine catalysis to stereoselectively create an all‐carbon stereogenic center, providing a straightforward approach to access spirooxindole derivatives in good yields and with high to excellent levels of enantioselectivity. Chiral hypervalent phenyl‐λ3‐iodanes generated in situ from the oxidation of the chiral phenyl iodine actually participate in the asymmetric oxidative dearomatizative spirocyclization reaction. 相似文献
98.
Photocontrolled Reversible Conversion of Nanotube and Nanoparticle Mediated by β‐Cyclodextrin Dimers
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He‐Lue Sun Dr. Yong Chen Jin Zhao Prof. Dr. Yu Liu 《Angewandte Chemie (International ed. in English)》2015,54(32):9376-9380
A photochemically interconvertible supramolecular nanotube–nanoparticle system was constructed through secondary assembling of self‐aggregates of amphiphilic porphyrin derivatives mediated by trans‐ and cis‐azobenzene‐bridged bis(permethyl‐β‐cyclodextrin). Significantly, these nanotubes and nanoparticles were able to interconvert upon irradiation at different wavelengths, and this photocontrolled morphological conversion is reversible and recyclable for tens of times, which will provide a feasible and convenient way to construct the ordered nanostructure with various morphologies that can be smartly controlled by the environmentally benign external stimulus. 相似文献
99.
Bo Xiao a Qingchun Yuan b a EaStChem School of Chemistry Purdie Building North Haugh University of St. rews Fife St. rews KY ST UK b Institute of Particle Science Engineering School of Processing Environmental & Mineral Engineering University of Leeds Houldworth Building Leeds LS JT UK 《中国颗粒学报》2009,7(2)
Hydrogen is expected to play an important role in future transportation as a promising alternative clean energy source to carbon-based fuels.One of the key challenges to commercialize hydrogen energy is to develop appropriate onboard hydrogen storage systems,capable of charging and discharging large quantities of hydrogen with fast enough kinetics to meet commercial requirements.Metal organic framework (MOF) is a new type of inorganic and organic hybrid nanoporous particulate materials.Its diverse networks can enhance hydrogen storage through tuning the structure and property of MOFs.The MOF materials so far developed adsorb hydrogen through weak disperston interactions,which allow significant quantity of hydrogen to be stored at cryogenic temperatures with fast kinetics.Novel MOFs are being developed to strengthen the interactions between hydrogen and MOFs in order to store hydrogen under ambient conditions.This review surveys the development of such candidate materials,their performance and future research needs. 相似文献
100.