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211.
Pisignano D Persano L Mele E Visconti P Cingolani R Gigli G Barbarella G Favaretto L 《Optics letters》2005,30(3):260-262
We investigated the emission properties of a distributed-feedback resonator based on an organic semiconductor patterned by a novel printing technology. We observed the peak splitting of the photonic bandstructure of the periodic grating and extracted the effective refractive index of the outcoupled guided modes. The laser works at the second diffraction order, exhibiting narrow single-mode emission at 637 nm, with a threshold as low as 37 microJ/cm2. The results suggest that direct printing is a promising fabrication technique for optically confined integrated optoelectronics. 相似文献
212.
Mele A Tran CD De Paoli Lacerda SH 《Angewandte Chemie (International ed. in English)》2003,42(36):4364-4366
213.
An effective Green function is introduced which satisfies an equation whose solution for a very large system is tractable. This function yields local densities of states and energy-dependent charge densities. Using a tight binding Hamiltonian and basis orbitals localized in the bonds, bulk and intrinsic unrelaxed vacancy states in Ge are studied. Results obtained are comparable to pseudo-potential calculations requiring self-consistency. 相似文献
214.
215.
We show that an electrical shift current is generated when electrons are photoexcited from the valence to conduction bands on a BN nanotube. This photocurrent follows the light pulse envelope and its symmetry is controlled by the atomic structure of the nanotube. We find that the shift current has an intrinsic quantum mechanical signature in which the chiral index of the tube determines the direction of the current along the tube axis. We identify the discrete lattice effects in the tangent plane of the tube that lead to an azimuthal component of the shift current. The nanotube shift current can lead to ultrafast optoelectronic and optomechanical applications. 相似文献
216.
Niko Van den Brande Cor Koning Paul Geerlings Gregory Van Lier Guy Van Assche Bruno Van Mele 《Journal of Thermal Analysis and Calorimetry》2011,105(3):775-781
The potential of polystyrene/polymethylphenylsiloxane (PS/PMPS) blends as a matrix for nanocomposites is investigated. It
was proven by dynamic rheometry and conductivity measurements that PMPS effectively disperses carbon nanotubes, as was already
known for polydimethylsiloxane (PDMS). The phase behaviour of PS/PMPS blends was investigated using differential scanning
calorimetry or modulated temperature differential scanning calorimetry. The blends were found to exhibit partial miscibility,
in contrast to the known immiscible behaviour of PS/PDMS blends. A miscibility window exists for PS/PMPS blends containing
less than approximately 10 wt% PMPS. 相似文献
217.
Fatma Demir Niko Van den Brande Bruno Van Mele Sabine Bertho Dirk Vanderzande Jean Manca Guy Van Assche 《Journal of Thermal Analysis and Calorimetry》2011,105(3):845-849
Defining appropriate annealing temperatures and times is vitally important for increasing the efficiency of bulk heterojunction
solar cells by favoring the crystallinity of the polymer-fullerene blend components. In order to better understand the annealing
process, the isothermal crystallization of poly(3-hexyl thiophene) (P3HT) and [6,6]-phenyl C61-butyric acid methyl ester (PCBM) blend investigated by means of rapid heating cooling calorimetry (RHC). Isothermal crystallization
experiments at temperatures in between the glass transition and melting, within the temperature range of 70–150 °C, can successfully
be performed since RHC permits cooling at a sufficiently high rate in order to prevent crystallization during cooling. Crystallization
isotherms were determined from the subsequent melting behavior of the blend. They were measured for a wide set of annealing
temperatures and times, and the evolution of the crystallization rate with temperature is compared for annealing from the
glassy state and from the melt state. 相似文献
218.
Zhao J Bertho S Vandenbergh J Van Assche G Manca J Vanderzande D Yin X Shi J Cleij T Lutsen L Van Mele B 《Physical chemistry chemical physics : PCCP》2011,13(26):12285-12292
In this work the phase behavior of [6,6]-phenyl C(61)-butyric acid methyl ester (PCBM) blends with different poly(phenylene vinylene) (PPV) samples is investigated by means of standard and modulated temperature differential scanning calorimetry (DSC and MTDSC) and rapid heat-cool calorimetry (RHC). The PPV conjugated polymers include poly(2-methoxy-5-(3',7'-dimethyloctyloxy)-1,4-phenylene vinylene) (MDMO-PPV), High T(g)-PPV which is a copolymer, and poly((2-methoxy-5-phenethoxy)-1,4-phenylene vinylene) (MPE-PPV). Comparisons of these PPV:PCBM blends with regioregular poly(3-hexyl thiophene) (P3HT):PCBM blends are made to see the different component miscibilities among different blends. The occurrence of liquid-liquid phase separation in the molten state of MDMO-PPV:PCBM and High T(g)-PPV:PCBM blends is indicated by the coexistence of double glass transitions for blends with a PCBM weight fraction of around 80 wt%. This is in contrast to the P3HT:PCBM blends where no phase separation is observed. Due to its high cooling rate (about 2000 K min(-1)), RHC proves to be a useful tool to investigate the phase separation in PPV:PCBM blends through the glass transition of these crystallizable blends. P3HT is found to have much higher thermal stability than the PPV samples. 相似文献
219.
L. Miu I. Ivan P. Badica G. Jakob D. Miu P. Mele K. Matsumoto M. Mukaida Y. Yoshida T. Horide A. Ichinose S. Horii 《Physica C: Superconductivity and its Applications》2010,470(20):1126-1129
The temperature T variation of the normalized magnetization relaxation rate S in high-temperature superconductors (HTS) with strong vortex pinning exhibits a maximum in the low-T range. This was reported for various HTS, and the origin of the faster relaxation at low T appearing in standard magnetization relaxation measurements was usually related to specific pinning properties of the investigated specimens. Since the observed behaviour seems to be characteristic to all HTS with enhanced pinning (generated by random and/or correlated disorder), we show that the S(T) maximum can be explained in terms of classic collective vortex creep. The influence of thermo-magnetic instabilities in the low-T range is also evidenced. The collective (elastic) creep regime is generated by the T dependent macroscopic currents induced in the sample during standard magnetization measurements. 相似文献
220.