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41.
Alexandru Vlasceanu Dr. Søren L. Broman Anne S. Hansen Anders B. Skov Prof. Dr. Martina Cacciarini Prof. Dr. Anders Kadziola Prof. Dr. Henrik G. Kjaergaard Prof. Dr. Kurt V. Mikkelsen Prof. Dr. Mogens Brøndsted Nielsen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(31):10796-10800
The conversion and efficient storage of solar energy is recognized to hold significant potential with regard to future energy solutions. Molecular solar thermal batteries based on photochromic systems exemplify one possible technology able to harness and apply this potential. Herein is described the synthesis of a macrocycle based on a dimer of the dihydroazulene/vinylheptafulvene (DHA/VHF) photo/thermal couple. By taking advantage of conformational strain, this DHA–DHA macrocycle presents an improved ability to absorb and store incident light energy in chemical bonds (VHF–VHF). A stepwise energy release over two sequential ring‐closing reactions (VHF→DHA) combines the advantages of an initially fast discharge, hypothetically addressing immediate energy consumption needs, followed by a slow process for consistent, long‐term use. This exemplifies another step forward in the molecular engineering and design of functional organic materials towards solar thermal energy storage and release. 相似文献
42.
We have theoretically investigated the energy band structures of two typical magnetic superlattices formed by perpendicular or parallel magnetization ferromagnetic stripes periodically deposited on a two-dimensional electron gas (2DEG), where the magnetic profile in the perpendicular magnetization is of inversion anti-symmetry, but of inversion symmetry in parallel magnetization, respectively. We have shown that the energy bands of perpendicular magnetization display the spin-splitting and transverse wave-vector symmetry, while the energy bands of the parallel magnetization exhibit spin degeneration and transverse wave-vector asymmetry. These distinguishing spin-dependent and transverse wave-vector asymmetry features are essential for future spintronics devices applications. 相似文献
43.
44.
J. Grenzer A. A. Ignatov E. Schomburg K. F. Renk D. G. Pavel'ev Yu. Koschurinov B. Melzer S. Ivanov S. Schaposchnikov P. S. Kop'ev 《Annalen der Physik》1995,507(3):184-190
We report on a microwave oscillator based on Bloch oscillations of electrons in a semiconductor superlattice. Our GaAs/AlAs superlattice, at room temperature, was coupled electromagnetically by an antenna to a rectangular cavity resonator, and was operated at a current-voltage state of negative differential conductance. We observed generation of microwave radiation at frequencies, depending on the resonator length, between 7 and 30 GHz. Electronic tuning by several percent was possible; the ratio of linewidth to frequency was of the order of 10?4. A radiation power up to 1 μW (at 10 GHz) was obtained, corresponding to a generator efficiency of the order of 10?3 for the conversion of electrical power to microwave radiation. 相似文献
45.
用能带理论分析一维超晶格电子在直流外场作用下的阻尼运动,对Bloch振荡和负微分电导现象给出清楚的物理图象,并通过数值解得到有阻尼时振荡频率随外场增加而趋近于Bloch频率的一般规律。 相似文献
46.
47.
Thin strained regions have been inserted at the interfaces of lattice-matched InGaAs/lnP superlattices to assess growth conditions
for tailoring of localized compositional changes and for studying As-P intermixing behavior during heterojunction growth.
Also, precise growth rates of binary composition layers were determined from specially designed superlattices using strained
layers of common anion compounds inserted periodically into InP and GaAs. Growth rates of fractional monolayers are found
to be identical to thick layer growth rates. When thin InAs, GaAs, GaP, ALAs, or AIP layers were inserted at the InGaAs/lnP
heterojunctions, the measured strain at either one or both interfaces was equal to the strain predicted from the growth rate
x time product. Excess strain seen in some cases is due to a change in As-P intermixing and this component can be separated
from the predicted strain. Insertion of Ga-compounds at the InP-grown-on-InGaAs interface causes interface roughening which
degrades the superlattice. For all other compositions the thin, highly strained regions are not detrimental to the crystalline
quality of the periodic structure. 相似文献
48.
M. Razeghi M. A. Poisson J. P. Larivain J. P. Duchemin 《Journal of Electronic Materials》1983,12(2):371-395
The low pressure metalorganic chemical vapor deposition epitaxial growth and characterization of InP, Ga0.47In0.53 As and GaxIn1-xAsyP1-y, lattice-matched to InP substrate are described. The layers were found to have the same etch pit density (EPD) as the substrate.
The best mobility obtained for InP was 5300 cm2 V−1S−1 at 300 K and 58 900 cm2 V−1 S−1 at 772K, and for GaInAs was 11900 cm2 V−1 S−1 at 300 K, 54 600 cm2 V−1 S−1 at 77 K and 90 000 cm V−1S−1 at 2°K. We report the first successful growth of a GaInAs-InP superlattice and the enhanced mobility of a two dimensional
electron gas at a GaInAs -InP heterojunction grown by LP-MO CVD. LP MO CVD material has been used for GaInAsPInP, DH lasers
emitting at 1.3 um and 1.5 um. These devices exhibit a low threshold current, a slightly higher than liquid phase epitaxy
devices and a high differential quantum efficiency of 60%. Fundamental transverse mode oscillation has been achieved up to
a power outpout of 10 mW. Threshold currents as low as 200 mA dc have been measured for devices with a stripe width of 9 um
and a cavity length of 300 um for emission at 1.5 um. Values of T in the range 64–80 C have been obtained. Preliminary life
testing has been carried out at room temperature on a few laser diodes (λ = 1.5μm). Operation at constant current for severalthousand
hours has been achieved with no change in the threshold current. 相似文献
49.
50.
The electron charge distribution in a strongly twisted push-pull ethylene [PPE, 3-(1,3-diisopropyl-2-imidazolidinylidene)-2,4-pentanedione] has been determined by low temperature (T = 21 K) single-crystal X-ray diffraction analysis. The derived electronic properties are consistent with a zwitterionic molecule, as indicated by a charge transfer of 0.82(16) e from the push to the pull moieties and a charge polarization of 0.29(7) e on the olefinic bond. A dipole moment of 12(3) D has been determined, which compares well with ab initio theoretical results in terms of both modulus and orientation. The second moments, which have also been obtained with good precision, characterize PPE as a highly quadrupolar molecule. The special electronic features of the molecule confer particular topological properties to the electron density distribution, as evidenced by comparison with "standard" organic molecules. The crystallographic asymmetric unit of the present system includes one water molecule, which is hydrogen bonded to PPE. Its topological properties have also been investigated, together with an analysis of the hydrogen bonds involved. 相似文献