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101.
K. De S. Das A. Roy V.S. Amaral S. Majumder S. Giri P.K. Mahapatra 《Physica B: Condensed Matter》2012,407(13):2442-2446
The magnetic and electrical transport properties of La0.9Mn0.9M0.1O3 (M=Mn, Zn and Ti) were investigated. The temperature and magnetic field dependence of electrical resistivity (ρ) and dc magnetization were studied. All the compounds are found in rhombohedral structure. The excess oxygen in all three compounds was detected through iodometric titration. A modification in resistivity is observed when M=Mn is replaced by M=Zn and Ti. The high temperature resistivity above TC follow variable range hopping model for both Zn and Ti compounds. For Zn doping, the observation of large field-cool effect and decrease in resistivity at room temperature and is assumed to be due to the implant of Mn4+ in Mn3+ matrix, which favor Mn3+/Mn4+ double exchange. The ferromagnetic behavior below TC for the compound with M=Ti is correlated to the excess oxygen in it, which implants Mn4+ and thus incorporates ferromagnetic interactions. The substitutions lead to a reduction of Tc and magnetization. 相似文献
102.
P. Mallick S. Majumder D.C. Agarwal D.K. Avasthi N.C. Mishra 《Applied Surface Science》2009,256(2):521-523
NiO nanoparticle thin films grown on Si substrates were irradiated by 107 MeV Ag8+ ions. The films were characterized by glancing angle X-ray diffraction and atomic force microscopy. Ag ion irradiation was found to influence the shape and size of the nanoparticles. The pristine NiO film consisted of uniform size (∼100 nm along major axis and ∼55 nm along minor axis) elliptical particles, which changed to also of uniform size (∼63 nm) circular shape particles on irradiation at a fluence of 3 × 1013 ions cm−2. Comparison of XRD line width analysis and AFM data revealed that the particles in the pristine films are single crystalline, which turn to polycrystalline on irradiation with 107 MeV Ag ions. 相似文献
103.
Manisree Majumder 《Journal of luminescence》2010,130(8):1497-1503
Nanostructured cadmium sulfide (CdS) thin films have been prepared by chemical bath deposition (CBD) method and after post deposition annealing of the thin films at different temperatures, photoluminescence (PL) property has been studied. The effects of various photoexcitation wavelengths on the PL behaviour of different annealed films of CdS were studied by recording the PL spectra. The intensity of PL, the profile of the PL spectra and the effects of photoexcitation wavelength depend drastically on the temperature of the post deposition annealing of the thin films. The XRD patterns of the films show the presence of both the hexagonal and cubic phases (mixed phases). The emission peak arises from the surface defects of the CdS nanocrystalline thin films. Significant modification in the surface morphology of the CdS films upon annealing has been observed from the FESEM images. The morphology of the thin films is expected to influence the PL behaviour of the CdS thin films. The quantum size effect and size dependant PL have been observed. 相似文献
104.
Rameswar Bhattacharjee Tirthick Majumder Ayan Datta 《Journal of computational chemistry》2019,40(15):1488-1495
Ground state (GS) instability of nondegenerate molecules in high symmetric structures is understood through Pseudo Jahn–Teller mixing of the electronic states through the vibronic coupling. The general approach involves setting up of a Pseudo Jahn–Teller (PJT) problem wherein one or more symmetry allowed excited states couple to the GS to create vibrational instability along a normal mode. This faces two major complications namely (1) estimating the adiabatic potential energy surfaces for the excited states which are often difficult to describe in case the excited states have charge-transfer or multi-excitonic (ME) character and (2) finding out how many such excited states (all satisfying the symmetry requirements for vibronic coupling) of increasing energies need to be coupled with the GS for a particular PJT problem. An analogous alternative approach presented here for the well-known case of symmetry breaking of planar (D6h) hexasilabenzene (Si6H6) to the buckled (D3d) structure involves identifying the second-order donor–acceptor, hyperconjugative interactions (E2i → j) that stabilize the distorted structure. Following the recent work of Nori-Shargh and Weinhold, one observes that the orbitals involved in the vibronic coupling between the S0/Sn states and those for the donor (filled)–acceptor (empty) interactions are identical. In fact, deletion of any particular pair of E2i → j interaction creates vibrational instability in the buckled structure and as a corollary, deleting it for the planar structure removes its instability. The one-to-one correlation between the natural bond orbital theory and PJT theory assists in an intuitive identification of the relevant (few) excited states from a manifold of computed ones that cause symmetry breaking by vibronic coupling. © 2019 Wiley Periodicals, Inc. 相似文献
105.
106.
S. Barman C. Rajesh G. P. Das C. Majumder 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2009,55(3):613-625
Here we report a systematic theoretical study of the structure and
electronic properties of Snn-1Pb and Pbn-1Sn (n = 2-13) clusters
and compare these results with pure Snn and Pbn to understand the
influence of the dopant elements. The calculations were carried out using
the density functional theory with generalized gradient approximation for
the exchange-correlation potential. Extensive search based on large number
of initial configurations has been carried out to locate the stable isomers
of Snn-1Pb and Pbn-1Sn (n = 2-13) clusters. The relative
stability of Snn-1Pb and Pbn-1Sn (n = 2-13) clusters is analyzed
based on the calculated binding energies and second difference in energy.
The stability analysis of these clusters suggests that, while the
substitution of Sn by Pb lowers the stability of Snn clusters, presence
of Sn enhances the stability of the Pbn clusters. The results suggest
that while for Snn-1Pb, n=4, 7, 10, 12 clusters are more stable than
their respective neighbors, Pbn-1Sn clusters with n = 4, 7 and 9 are
found to be more stable. Based on the fragmentation pattern it is seen that
for Snn-1Pb and Pbn-1Sn clusters favor monomer evaporation of the
Pb atom up to n =11 and n =12, respectively. Unlike this trend, the
Sn11Pb undergoes fission type fragment into Sn5Pb and Sn6
clusters. A comparison between our theoretical results and surface induced
dissociation experiment shows good agreement, which gives confidence on the
prediction of the ground state geometries. 相似文献
107.
108.
We discuss the question of equilibration in heavy ion collisions and how it can be addressed in experiment 相似文献
109.
110.