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61.
MgB2 superconducting wires were produced by the Mg diffusion method. Scanning electron microscopy (SEM), optical microscopy, dispersive X-ray analysis (EDS), and XRD diffraction were used to study the physical structure and content of the wires. Magnetic properties (T
c
m, H
c1, H
c2, J
c by the Bean model) were obtained with a SQUID magnetometer, and transport properties (T
c
r
, H
c2, resistivity and residual resistivity ratio) were measured using a standard four-lead configuration. The V-I characteristics of the wires close to the critical temperature showed a staircase response, which was attributed to the presence of weak links, creating phase slip centers. The origin of those weak links is discussed in relation to their formation and structure. 相似文献
62.
研究了焦耳退火和等温退火对Fe73.5Cu1 Nb3Si1 3.5B9非晶丝巨应力阻抗效应的影响。实验结果表明 ,非晶合金丝经电流密度为2 6A·mm- 2 的焦耳处理后 ,其阻抗最大变化率达到 2 5 % ,灵敏度为 1 71%·MPa- 1 ;淬态样品在 5 80℃等温退火 0 5h后 ,其阻抗最大变化率达到 67% ,灵敏度为 0 85 %·MPa- 1 。这两种退火方法都可以明显改善Fe73.5Cu1 Nb3Si1 3.5B9非晶合金丝的巨应力阻抗效应 ,阻抗的最大变化率与退火过程中晶化导致的平均各向异性的改变有关 ,而灵敏度的差异是由退火方法导致材料机械性能的差异带来的 相似文献
63.
Bong-Hwan Oh Kazuaki Ishikawa Naoki Hayakawa Hitoshi Okubo Yukio Kito 《Electrical Engineering in Japan》1994,114(1):45-53
A superconducting multistranded cable is used to realize high current capacity for ac use. The critical current value of the cable is reported to be less than the simple summation of the individual critical current value of each strand. The causes for such a degradation of the critical current value have not been revealed. This paper investigates the current distribution in multistrands before and after their quenching by using seven-strand superconducting cable and 7x7 cable. The following experimental results are derived: (1) the quenching is initiated at one strand in the cable; (2) the current in the quenched strand is transferred into the other strands; (3) an avalanche of quenching is induced among the strands; and (4) the central strand is quenched finally among the strands. The critical current values of the 7- and 7 × 7-stranded cables also are measured. These values are in good agreement with the predicted values based on the mutual inductance among the strands. It is concluded that the unbalance of the current distribution in the superconducting multistrands can be one of the promising causes for the degradation of the critical current value. 相似文献
64.
65.
66.
67.
M. Henini A. PatanèA. Polimeni A. LevinL. Eaves P.C. MainG. Hill 《Microelectronics Journal》2002,33(4):313-318
One of the main directions of contemporary semiconductor physics is the production and study of structures with a dimension less than two, i.e. quantum wires (QWi) and quantum dots (QDs), in order to realise novel devices that make use of low-dimensional confinement effects.One of the promising fabrication methods is to use self-organised three-dimensional (3D) structures, such as 3D coherent islands, which are often formed during the initial stage of heteroepitaxial growth in lattice-mismatched systems. Quantum dots, for example, are believed to provide a promising way for a new generation of optical light sources such as injection lasers. While quantum well structures are already widely used in optoelectronic devices, QWi and QDs appear to be much more difficult to fabricate for this purpose. Some of the electrical and optical properties of self-assembled QDs will be reported in this paper. 相似文献
68.
In this paper, we will present our recent research on the growth and characterization of some Si-based heterostructures for
optical and photonic devices. The heterostructures to be discussed are ZnO nanorods on Si, SiO2, and other substrates such as SiN and sapphire. We will also consider strained Si1−xGex/Si heterostructures for Si optoelectronics. The performance and functionality extension of Si technology for photonic applications
due to the development of such heterostructures will be presented. We will focus on the results of structural and optical
characterization in relation to device properties. The structural characterization includes x-ray diffraction for assessment
of the crystallinity and stress in the films and secondary ion mass spectrometry for chemical analysis. The optical properties
and electronic structure were investigated by using photoluminescence. The device application of these thin film structures
includes detectors, lasers, and light emitting devices. Some of the Si-based heterostructures to be presented include devices
emitting and detecting up to the blue-green and violet wave lengths. 相似文献
69.
四线法是精确测量小电阻时最常用的一种方法。射频控制器1805B作为微波功率计自动校准装置中(系统ⅡA)的重要组成部分,它的直流替代电路是由三个臂的惠斯通电桥组成,其每四个臂可以用两个100Q的标准电阻等效代替。通过对标准电阻两端直流电压的准确测量,就可判断1805B在各档的直流替代功率是否满足要求,本文最后给出了直流替代功率所对应的直流电压范围。 相似文献
70.