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排序方式: 共有253条查询结果,搜索用时 546 毫秒
131.
Madhusmita Behera Subramanian Raju Ganapathy Panneerselvam Mythili Rangachari Saroja Saibaba 《Journal of Physics and Chemistry of Solids》2014
The enthalpy increment for a series of Ti–xTa (x=5, 10, 15, 20 mass%) alloys, having α(hcp)+β(bcc) two phase microstructure has been measured using inverse drop calorimetry in the temperature range 463–1257 K. The studies clearly revealed the occurrence of α→β diffusional phase transformation. Both the α→β transformation onset temperatures and the measured transformation enthalpy Δ0Htrα→β exhibit progressively lower values with increasing Ta content. It is found that the measured enthalpy in the transformation region is constituted of two principal contributions namely, (i) the enthalpy due to untransformed α and coexisting β phases and (ii) the transformation enthalpy due to α→β phase change. Since the fractional extent of α→β transformation varies continuously with temperature, the measured enthalpy variation in the transformation domain has been modeled using Kolmogorov–Johnson–Mehl–Avrami formalism for the diffusional transformation kinetics. The thermodynamic quantities for all the alloys have been derived. 相似文献
132.
Pradip Kar Ajaya K. Behera Narayan C. Pradhan Basudam Adhikari 《Journal of Macromolecular Science: Physics》2013,52(9):1822-1833
Poly(m-aminophenol) (PmAP) was synthesized from m-aminophenol (mAP) in aqueous sodium hydroxide (NaOH) using ammonium persulfate (APS) as an oxidative initiator. Free standing PmAP films were cast from dimethyl sulfoxide (DMSO) solution of the polymer. Then the film was doped with various inorganic acids using a solution doping technique. Various inorganic acid doped PmAP films were characterized by ultraviolet-visible (UV-Vis), Fourier transform infrared (FTIR), and energy dispersive X-ray (EDS) spectroscopies, X-ray diffraction (XRD) analysis and elemental (C, H, N, S, O) analysis. All the results were explained on a comparative basis and the doping scheme was proposed. The DC-conductivity of the inorganic acid doped films was measured using a standard four-probe method. From the DC-conductivity measurements it was found that sulfuric acid had a better doping effect in terms of conductivity than that of the other inorganic acids used, perchloric acid and phosphoric acid. An explanation of the reason for the better doping effect of sulfuric acid than that of the other inorganic acids is given. 相似文献
133.
Khatkar V. Vijayalakshmi A. G. Sakthi Manjunath R. N. Olhan S. Behera B. K. 《Mechanics of Composite Materials》2020,56(3):367-378
Mechanics of Composite Materials - The role of fiber reinforcement architecture in adjusting the mechanical properties of glass-fiber-reinforced epoxy composite materials is studied. Fibrous... 相似文献
134.
135.
Ani Ozcelik Dr. Daniel Aranda Sara Gil-Guerrero Xaquín A. Pola-Otero Dr. Maria Talavera Liangxuan Wang Dr. Santosh Kumar Behera Dr. Johannes Gierschner Prof. Ángeles Peña-Gallego Dr. Fabrizio Santoro Dr. Raquel Pereira-Cameselle Dr. J. Lorenzo Alonso-Gómez 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(72):17342-17349
Several theoretical studies have proposed strategies to generate helical molecular orbitals (Hel-MOs) in [n]cumulenes and oligoynes. While chiral even-[n] cumulenes feature Hel-MOs, odd-[n] cumulenes may also present them if the terminal groups lie in different planes. However, the proposed systems have been either experimentally unfeasible or resulted in opposite pseudo-degenerated Hel-MOs. We hereby demonstrate the introduction of a remarkable energy difference between helical orbitals of opposite twist by fixing the torsion angle between the terminal groups in butadiyne fragments. To experimentally lock the conformation of the terminal groups, we designed and synthesized cyclic architectures by combining acetylenes with chiral spirobifluorenes. The high stability of these systems with distinct helical orbitals allowed their isolation and full characterization. In our view, these results constitute a step further in the development of real systems presenting helical molecular orbitals. 相似文献
136.
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138.
Structural and impedance spectroscopic studies of samarium modified lead zirconate titanate ceramics
The polycrystalline samples of Pb1−xSmx(Zr0.60Ti0.40)1−x/4O3 (PSZT) where x=0.00, 0.03, 0.06 and 0.09 were prepared by a high-temperature solid-state reaction technique. The preliminary structural analysis using X-ray diffraction (XRD) data collected at room temperature has confirmed the formation of single-phase compounds in tetragonal crystal system. The morphological study of each sample using scanning electron microscope (SEM) has revealed that the grains are uniformly distributed through out the surfaces of the samples. Using complex impedance spectroscopy (CIS) technique, the electrical impedance and modulus properties of the materials were studied in a wide range of temperatures at different frequencies. The impedance analysis indicates the presence of bulk resistive contributions in the materials which is found to decrease on increasing temperature. The nature of variation of resistances with temperature suggests a typical negative temperature coefficient of resistance (NTCR) type behavior of the materials. The complex modulus plots clearly exhibits the presence of grain boundaries along with the bulk contributions in the PSZT materials. The presence of non-Debye type of relaxation has been confirmed by the complex impedance analysis. The variation of dc conductivity (bulk) with temperature demonstrates that the compounds exhibit Arrhenius type of electrical conductivity. 相似文献
139.
The heavy fermion system (HFS) is described by the periodic Anderson model (PAM), treating the Coulomb correlation between
the f-electrons in the meanfield Hartree-Fock approximation. Superconductivity is introduced by a BCS-type pairing term among the
conduction electrons. Within this approximation the equation for the superconducting gap is derived, which depends on the
effective position of the energy level of the f-electrons relative to the Fermi level. The latter in turn depends on the occupation probability n
f of the f-electrons. The gap equation is solved self-consistently with the equation for n
f; and their temperature dependences are studied for different positions of the bare f-electron energy level, with respect to the Fermi level. The dependence of the superconducting gap on the hybridization leads
to a re-entrant behaviour with increasing strength. The induced pairing between the f-electrons and the pairing of mixed conduction and f-electrons due to hybridization are also determined. The temperature dependence of the hybridization parameter, which characterizes
the number of electrons with mixed character and represents the number of heavy electrons is studied. This number is shown
to be small. The quasi-particle density of states (DOS) shows the existence of a pseudo-gap due to superconductivity and the
signature of a hybridization gap at the Fermi level. For the choice of the model parameters, the DOS shows that the HFS is
a metal and undergoes a transition to the gap-less superconducting state.
相似文献
140.
The behaviour of the impurity modes due to a pair of substitutional impurities characterized by both mass as well as force-constant
changes and occupying nearest neighbour positions in a diatomic linear chain, is studied. The results are compared with those
for the case of impurity pairs occupying next nearest neighbour sites discussed earlier as well as the existing three dimensional
calculations of Elliott and Pfeuty. The nearest neighbour impurity pair gap and local modes can be interpreted in terms of
two single impurities substituted in the two different sublattices unlike the next nearest neighbour pair modes. The inband
resonant modes are totally new features characteristic of the pair. Finally, the predictions of the theory are compared with
the available experimental data for Si-impurity-pair-complexes and qualitative agreement is shown. 相似文献