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91.
The determination of the internal strains on the coupling parameter approach becomes very involved particularly when the number
of atoms per unit cell is very large. It is shown in this paper that a knowledge of the site symmetry of the atoms helps one
in determining the number of non-vanishing internal strain coefficients easily. The internal strain coefficients of two symmetry
connected atoms can also be related. Examples are shown to illustrate these ideas. 相似文献
92.
A theory of optical double resonance which takes into account the cooperative interactions among atoms is formulated. The analytical result for the double resonance spectra in the conventional situation when the probe field is weak, is given. The changes in the nature of the spectra as one sweeps from cooperative to single atom branch are discussed. The cooperative interaction is shown to reduce considerably the asymmetry of the Autler-Towne's doublet. 相似文献
93.
G. S. Reddi C. R. M. Rao T. A. S. Rao S. Vijaya Lakshmi R. K. Prabhu T. R. Mahalingam 《Fresenius' Journal of Analytical Chemistry》1994,348(5-6):350-352
Summary Detailed studies for evaluating the optimum nickel sulphide button size in the estimation of platinum group elements (PGE) by inductively coupled plasma mass spectrometry (ICPMS) were carried out. PGE losses in various stages of the process have been studied. The results indicate that among the three button sizes investigated, i.e., 2.5, 5 and 8 g, the 2.5 g button was found to be adequate for the full recovery of the PGE. Losses of PGE in the fusion slag and in the pulp at the second filtration stage have been found to be negligible. Tellurium coprecipitation was found to minimize the losses during the dissolution of the nickel sulphide button. 相似文献
94.
Shailaja J Kaanumalle LS Sivasubramanian K Natarajan A Ponchot KJ Pradhan A Ramamurthy V 《Organic & biomolecular chemistry》2006,4(8):1561-1571
Photochemistry of 17 aryl alkyl ketones included within cation exchanged zeolites has been examined. In solution five of the 17 ketones undergo intramolecular hydrogen abstraction reaction even in the presence of a chiral amine and the rest are photoreduced to the corresponding alcohol. Within zeolites all 17 ketones yielded in presence of a chiral amine, the corresponding alcohol as the major product. When a chiral amine was used as the coadsorbent within alkali ion exchanged zeolites, enantiomerically enriched alcohol was formed in all cases. The best chiral induction was obtained with phenyl cyclohexyl ketone (enantiomeric excess: 68%). 1H-13C Cross Polarization Magic Angle Spinning (CP-MAS) experiments, with a model ketone (perdeuterated acetophenone) and chiral amine (pseudoephedrine) included within MY zeolites, suggested that the cation brings the reactant and the chiral amine closer. The role of the cation in such a process is also revealed by the computation results. The results presented here highlight the importance of a supramolecular structure in forcing a closer interaction between a reactant and a chiral inductor that could be used to achieve asymmetric induction in photoproducts. 相似文献
95.
Sharmistha Bagchi Snehal Jani N. Lakshmi 《Journal of magnetism and magnetic materials》2010,322(24):3851-3856
The present study reports the effect of swift heavy ion irradiation on structural and magnetic properties of sputtered W/Fe multilayer structure (MLS) having bilayer compositions of [W(10 Å)/Fe(20 Å)]10BL. The MLS is irradiated by 120 MeV Au9+ ions of fluences 1×1013 and 4×1013 ions/cm2. Techniques like X-ray reflectivity (XRR), cross-sectional transmission electron microscopy (X-TEM) and DC magnetization with a vibrating sample magnetometer (VSM) are used for structural and magnetic characterization of pristine and irradiated MLS. Analysis of XRR data using Parratt’s formalism shows a significant increase in W/Fe layer roughness. X-TEM studies reveal that intra-layer microstructure of Fe layers in MLS becomes nano-crystalline on irradiation. DC magnetization study shows that with spacer layer thickness interlayer coupling changes between ferromagnetic to antiferromagnetic. 相似文献
96.
Fixed point theorems for generalized weakly S-contractive mappings in partial metric spaces
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Lakshmi Narayan Mishr Shiv Kant Tiwari Vishnu Narayan Mishra 《Journal of Applied Analysis & Computation》2015,5(4):600-612
In this paper, we establish some unique xed point theorems for generalized weakly S-contractive with nondecreasing and weakly increasing mappings in complete partial metric space. Also, we give some examples for strengthens of our main results. 相似文献
97.
S. Lakshmi Reddy N. C. Gangi Reddy R. Rama Subba Reddy G. Siva Reddy P. Sambasiva Rao B. Jagannatha Reddy 《辐射效应与固体损伤》2013,168(11):671-679
A powdered sample of Phyllanthus amarus herb of Kadapa district of Andhra Pradesh, India, is used in the present study. ICP-MS analysis indicates that copper is present in higher concentration when compared to other elements. Although the Pb is toxic, it is within the permissible limit. The evaluated soil and herb physico-chemical parameters indicate that the sample is acidic in nature in comparison with the soil. An EPR study on powdered sample confirms the presence of Fe(III), Mn(II) and Cu(II). Optical absorption spectrum indicates that Fe(III) impurity is present in octahedral structure whereas Cu(II) is present in rhombically distorted octahedral environment. MIR results are due to carbonate fundamentals. 相似文献
98.
P. Vinotha Boorana Lakshmi 《辐射效应与固体损伤》2013,168(6):365-371
The diluted magnetic semiconductor, ZnO:Mn, is studied here theoretically for the defect modes, as this is not well documented in the literature, even though other investigations are reported. Theoretical results are compared with the experimental results. 相似文献
99.
P. Lakshmi Praveen 《Phase Transitions》2013,86(5):433-441
This article describes the thermodynamic stability and phase behaviour of a liquid crystalline material p-n-hexyloxybenzylidene-p-toluidine (6OBT) at a molecular level. The atomic net charge and dipole moment at each atomic centre have been evaluated using the complete neglect differential overlap (CNDO/2) method. The modified Rayleigh–Schrodinger perturbation method along with multicentred-multipole expansion method has been employed to evaluate the long-range intermolecular interactions, while a ‘6-exp’ potential function has been assumed for the short-range interactions. The total interaction energy values obtained through these computations have been used to calculate the probability of each configuration at room temperature (300?K), nematic–isotropic transition temperature (346.9?K) and above transition temperature (400?K) using the Maxwell–Boltzmann formula. Further, the Helmholtz free energy and entropy of each configuration has been computed during the different modes of interactions. An attempt has been made to understand the phase behaviour and stability of the molecule based on thermodynamic parameters introduced in this article. 相似文献
100.
Increasing the stability of perovskite solar cells is one of the most important tasks in the photovoltaic industry. Thus, the structural, energetic, and electronic properties of pure CH3NH3PbI3 and fully doped compounds (CH3NH3PbBr3 and CH3NH3PbCl3) in cubic and tetragonal phases were investigated using density functional theory calculations. We also considered the effects of mixed halide perovskites CH3NH3PbI2X (where X = Br and Cl) and compared their properties with CH3NH3PbI3. The DFT results indicate that the phase transformation from tetragonal to cubic phase decreases the band gap. The calculated results show that the X‐site ion plays a vital role in the geometrical stability and electronic levels. An increase in the band gap and a reduction in the lattice constants are more apparent in CH3NH3PbI2X compounds (I > Br > Cl). 相似文献