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Valeria van Axel Castelli Antonella Dalla Cort Luigi Mandolini Valentina Pinto David N. Reinhoudt Fabrizio Ribaudo 《Supramolecular chemistry》2013,25(2-3):211-219
The complexation of the salophen-uranyl metallocleft 2 and of its half-cleft analogue 3 with enones and other carbonyl compounds was assessed in chloroform by UV-Vis titration and, occasionally, by FT-IR measurements. Complexes with receptors 2 and 3 are in all cases more stable than those with the control unsubstituted uranyl-salophen 1 , showing that in addition to the primary binding force provided by coordination of the carbonyl oxygen to the uranium, a significant driving force for complexation, typically in the range of 2-3 kcal/mol, results from van der Waals interactions of the guest with the aromatic walls. Replacement of the phenyl group in 3 with larger aromatic residues to give 4 and 5 , led to enhanced complex stabilities, due to more extended contact surfaces between host and guest. 相似文献
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Vera Vasylyeva 《Journal of fluorine chemistry》2010,131(3):446-4255
The influence of fluorine substituents on the crystallisation behaviour of pyridine was investigated by crystal structure determinations. The low melting compounds 2-fluoropyridine, 2,6-difluoropyridine and 2,4,6-trifluoropyridine were crystallised by in situ crystallisation directly on the single crystal X-ray diffractometer. 相似文献
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Energy bands formed by rotation–vibrational states of molecules in the presence of symmetry and their qualitative modifications under variation of some control parameters are studied within the semi-quantum model. Rotational variables are treated as classical whereas a finite set of vibrational states is considered as quantum. In the two-state approximation the system is described in terms of a fiber bundle with the base space being a two-dimensional sphere, the classical phase space for rotational variables. Generically this rank 2 complex vector bundle can be decomposed into two complex line bundles characterized by a topological invariant, the first Chern class. A general method of explicit calculation of Chern classes and of their possible modifications under variation of control parameters in the presence of symmetry is suggested. The construction of iso-Chern diagrams which split the space of control parameters into connected domains with fixed Chern numbers is suggested. A detailed analysis of the rovibrational model Hamiltonian for a D3 invariant molecule possessing two vibrational states transforming according to the two-dimensional irreducible representation is done to illustrate non-trivial restrictions imposed by symmetry on possible values of Chern classes. 相似文献
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Hu Jianjun Duan Yuping Zhang JiaJing Hui Liu ShunhuaLi Weiping 《Physica B: Condensed Matter》2011,406(10):1950-1955
MnO2/doped polyaniline (PANI) is prepared by an in situ polymerization method using γ-MnO2 as the addition agent and hydrochloric acid as the doping agent. Products are characterized by FT-IR, UV-vis, XRD, and TEM. Conductivity, electromagnetic properties, and microwave absorption properties are first discussed on the basis of structural characterization. The as-prepared products of MnO2/PANI are partially crystalline in nature and spherical in pattern with grain sizes of 50-70 nm. MnO2 particles are successfully decorated with doped PANI. MnO2/PANI displays moderate electric conduction, excellent dielectric losses, and microwave absorption capabilities. Compared to pure MnO2, the dielectric and reflection loss properties of MnO2/PANI composites exhibit significant improvements, with an effective absorption band at 5 GHz under −10 dB and maximum reflection loss of −21 dB at 13.56 GHz. Pure MnO2 shows an effective absorption band of 3 GHz under −10 dB and a maximum reflection loss of −14.20 dB at 11.5 GHz. Thus, MnO2/PANI composites are found to be a promising microwave absorption material. 相似文献
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We report a Kondo-effect study of electron transport through a quantum dot with embedded biaxial single-molecule magnet based on slave boson mean-field theory and non-equilibrium Green-function technique. It is found the macroscopic quantum coherence of molecule-magnet results in the Kondo peak split of differential conductance due to interaction between electron and molecular magnet. It is also demonstrated that both the peak height and position can be controlled by the sweeping magnetic field and polarization of ferromagnetic electrodes. The characteristic peak split may be used to identify the macroscopic quantum coherence and develop molecule devices. 相似文献