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21.
The electrical characteristics of Pd Schottky contacts on ZnO films have been investigated by current-voltage (I–V) and capacitance–voltage (C–V) measurements at different temperatures. ZnO films of two thicknesses (400 nm and 1000 nm) were grown by DC-magnetron sputtering on n-Si substrates. The basic structural, optical and electrical properties of these films are also reported. We compared the two Schottky diodes by means of characteristic parameters, such as rectification ratio, ideality factor (η), barrier height (Φb) and series resistance and obtained better results for the 1000 nm-ZnO Schottky diodes. We also discussed the dependence of I‐V characteristics on temperature and the two distinct linear regions observed at low temperatures are attributed to the existence of two different inhomogeneous barrier heights. From I–V plots in a log-log scale we found that the dominant current-transport mechanism at large forward bias is space-charge limited current (SCLC) controlled by the presence of traps within the ZnO bandgap. The existence of such traps (deep states or interface states) is demonstrated by frequency-dependent capacitance and deep-level transient spectroscopy (DLTS) measurements. 相似文献
22.
Dave KIELPINSKI 《Frontiers of Physics in China》2008,3(4):365-381
Atomic ions trapped in ultra-high vacuum form an especially well-understood and useful physical system for quantum information
processing. They provide excellent shielding of quantum information from environmental noise, while strong, well-controlled
laser interactions readily provide quantum logic gates. A number of basic quantum information protocols have been demonstrated
with trapped ions. Much current work aims at the construction of large-scale ion-trap quantum computers using complex microfabricated
trap arrays. Several groups are also actively pursuing quantum interfacing of trapped ions with photons.
相似文献
23.
24.
X. J. Bao T. E. Schlesinger W. A. Bonner R. E. Nahory H. L. Gilchrist E. Berry E. A. Beam S. Mahajan 《Journal of Electronic Materials》1991,20(2):207-210
Bulk single crystals of InxGa1-xAs (0.01 <x < 0.12) were successfully grown by the Liquid Encapsulated Czochraski (LEC) technique. These crystals are of high quality
and can provide tunable substrate material for epitaxial application, since the lattice constant may be adjusted by varying
the composition. Nominally undoped crystals were semi-insulating as grown ifx is less than about 0.05. Semi-insulating crystals with higher In composition can be obtained by chromium doping during crystal
growth. The asgrown crystals were studied by 4.2 K photoluminescence spectroscopy (PL) and thermally stimulated current spectroscopy
(TSC). Results from PL measurements indicate good crystal quality and impurity control. TSC spectra reveal several bulk traps
in undoped and Cr doped semi-insulating samples. The activation energies of these traps decrease as In composition is increased.
The amount of change in activation energy is about one third of the bandgap shrinkage due to increased In concentration. 相似文献
25.
Standard IC processes, as well as those involving the use of ionizing radiation, such as x-ray lithography etc., result in
the generation of bulk defects, and interface states in the gate insulator, or underlying substrate, respectively, of insulated
gate field effect transistors. Bulk defects are believed to be present as positively and negatively charged electron and hole
traps, respectively, as well as neutral hole and “large” and “small” neutral electron traps. This paper provides a perspective
of the current state of knowledge about the spatial distributions of large bulk defects, their areal densities, sizes, possible
interrelationships among them, and the special cases of defects created by ion implanted silicon and oxygen, where knock-on
effects have been simulated. It appears that bulk defects may all have their origin in neutral hole traps, (so-called E′ centers)
and that when the insulator thickness is decreased to about 6-7 nm, defects are either no longer present, or, more likely,
are incapable of trapping charge at room temperature because trapped carriers can either tunnel to one of the interfaces,
or be annihilated by a reverse process. It appears possible also that the precursor of the several types of defects only forms
at a “grown” silicon-silicon oxide interface. In theory, this would make it possible to grow defect free insulators by a combination
of deposition and oxidation processes. 相似文献
26.
The characteristics of a new type of capacitance spectroscopy of deep traps in semiconductors are reviewed. A double radiation
source technique is employed, the first source controlling the occupation of the traps and the characteristic time constant
of the experiment, the second probing the spectral distribution of traps by selectively photoinducing emission to the conduction
and valence bands. Time differentiation enhances the detectivity of the traps and minimizes drift problems. Typical spectra
obtained with this quasi-equilibrium spectroscopic technique are described. The chromium trap in GaAs presents a distinctive
feature with interesting properties which are discussed. Comparisons with thermal capacitance measurements are made, showing
the complementary nature of the two methods. The use of the technique to detect out-diffusion of Cr from an insulating substrate
into an epitaxial layer is described. 相似文献
27.
A 100 MWt reactor design has been conceived to support flux level of the order of 1015 n/cm2/s in selected flux trap zones. The physics design considers high enriched metallic alloy fuel in the form of annular plates
placed in a D2O moderator tank in a hexagonal lattice arrangement. By choosing a tight lattice pitch in the central region and double the
lattice pitch in the outer region, it is possible to have both high fast flux and thermal flux trap zones. By design the flux
level in the seed fuel has been kept lower than in the high flux trap zones so that the burning rate of the seed is reduced.
Another important objective of the design is to maximize the time interval of refueling. As against a typical refueling interval
of a few weeks in such high flux reactor cores, it is desired to maximize this period to as much as six months or even one
year. This is possible to achieve by eliminating the conventional control absorbers and replacing them with a suitable amount
of fertile material loading in the reactor. Requisite number of seedless thorium-aluminum alloy plates are placed at regular
lattice locations vacated by seed fuel in alternate fuel layers. It is seen that these thorium plates are capable of acquiring
asymptotic fissile content of 14 g/kg in about 100 days of irradiation at a flux level of 8 × 1014 n/cm2/s. In summary, the core has a relatively higher fast flux in the central region and high thermal flux in the outer region.
The present physics design envisages a flat core excess reactivity for the longest possible cycle length of 6 months to one
year. It is also possible to modify the design for constant subcriticality for about the same period or longer duration by
considering neutron spallation source at the centre and curtailing the power density in the inner core region by shielding
it with a layer of thoria fuel loading.
相似文献
28.
Recent theoretical advances have identified several computational algorithms that can be implemented utilizing quantum information
processing (QIP), which gives an exponential speedup over the corresponding (known) algorithms on conventional computers.
QIP makes use of the counter-intuitive properties of quantum mechanics, such as entanglement and the superposition principle.
Unfortunately it has so far been impossible to build a practical QIP system that outperforms conventional computers. Atomic
ions confined in an array of interconnected traps represent a potentially scalable approach to QIP. All basic requirements
have been experimentally demonstrated in one and two qubit experiments. The remaining task is to scale the system to many
qubits while minimizing and correcting errors in the system. While this requires extremely challenging technological improvements,
no fundamental roadblocks are currently foreseen. 相似文献
29.
光电耦合器电流传输比的噪声表征 总被引:5,自引:0,他引:5
光电耦合器中可俘获载流子的陷阱密度是影响其电流传输比(CTR)的重要因素,并与器件可靠性有密切关系.在器件内部的多种噪声中,1/f噪声可有效地表征器件陷阱密度.本文在研究光电耦合器工作原理以及1/f噪声理论的基础上,建立了光电耦合器的CTR表征模型和1/f噪声模型.在输入电流宽范围变化的条件下,测量了器件的电学噪声和CTR变化,实验结果验证了以上模型的正确性.将CTR模型与噪声模型相结合,得到了CTR与1/f噪声之间的关系.此关系应用于对光电耦合器辐照实验结果的分析,实验结果与理论得到的结论一致.理论与实验结果表明,噪声幅值越大,电流指数越接近于2,则器件的可靠性越差,相同工作条件下CTR的老化衰减量越大,其失效率显著增大.从而证明噪声可表征光电耦合器的CTR并能准确地反映器件的可靠性. 相似文献
30.
Larry Sadwick 《Journal of Electronic Materials》1990,19(7):637-650
The capacitance-voltage (C-V) technique is one of the most powerful and direct methods to investigate interface traps in metal-insulator-semiconductor
(MIS or MOS) related devices. As the C-V technique is of such fundamental importance in detecting and monitoring process related
defects the systematic measurement concerns, misinterpretations and limitations associated with the equipment used to implement
this technique must be fully understood and characterized. This study reports the results of a detailed comparison of both
the (raw) measured C-V curve and the (analyzed) interface trap density versus energy data obtained using commercially available
quasistatic meters, specifically the Hewlett-Packard (HP) model 4140B quasistatic/dc picoammeter and the Keithley model 595
quasistatic meter. 相似文献