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51.
铜引线键合中影响焊球硬度因素的研究 总被引:1,自引:0,他引:1
Hong Meng Ho Yee Chen Tan Heng Mui Goh Wee Chong Tan Boon Hoe Toh Jonathan Tan Zhao Wei Zhong 《电子工业专用设备》2009,38(11):10-18
铜丝球焊由于其经济优势和优越的电气性能近来得到了普及,然而,在引线键合工艺中用铜丝取代金丝面临着一些技术上的挑战。多年来,IC芯片焊盘结构已经逐步适应了金丝球焊。铜在本质上比金硬度高,因此以铜线取代金线便引出了有关硬度的问题。研究了用25.4μm铜丝球焊中与键合机参数有关的铜焊球硬度特性。采用电子打火系统不同的电流和打火时间设置,用5%氢气和95%氮气组成的惰性保护气体形成了一个典型的25.4μm大小的铜焊球,研究了维氏硬度的焊球。用实验设计建立了第一和第二键合参数,进行了无空气焊球基本数据调整。通过改变电子打火系统参数。对硬度特性进行了进一步的测试。典型的键合球的大小和厚度的第一键合响应证实铜键合球的生产实力与电子打火系统的电流和打火时间有关. 相似文献
52.
Recent experiments have shown failure in flip chip micro solder joints induced by electromigration. This paper proposes a three-dimensional computational model to simulate the evolution of micro and sub-micro scale solder joints due to electromigration induced diffusion. The evolving morphology of the solder joint related with multiple mechanisms causes a computational challenge. This is addressed by employing a diffuse interface model with multiple concentrations. To efficiently resolve complications, a semi-implicit Fourier spectral scheme and a biconjugate-gradient method are adopted. Results have demonstrated rich dynamics and solder breakage at the interface on the cathode side. Furthermore, the effect of the designed interface region on the reliability of solder joints has been investigated with the developed model. 相似文献
53.
Thermomechanical stress and strain in the solder joints of a dummy area array package were studied as electromigration occurred.
A current density of 0.4 × 104 A/cm2 was applied to this package, constructed with 9 × 9 solder joints in a daisy chain, to perform the electromigration test.
After 37 h, the first joint on the path of the electron flow broke off at the cathode, and the first three solder joints all
exhibited a typical accumulation of intermetallic compounds at the anode. Different solder joints exhibited dissimilar electromigration
states, such as steady state and nonsteady state. Finite element analysis indicated that during steady-state electromigration,
although the symmetrical structure produced uniform distributions of current density and Joule heating in all solder joints,
the distribution of temperature was nonuniform. This was due to the imbalanced heat dissipation, which in turn affected the
distribution of thermomechanical stress and strain in the solder joints. The maximum thermomechanical stress and strain, as
well the highest temperature and current crowding, appeared in the Ni/Cu layer of each joint. The strain in the Ni/Cu layer
was significant along the z-axis, but was constrained in the x–y plane. The thermomechanical stress and strain increased with advancing electromigration; thus, a potential delamination between
the Ni/Cu layer and the printed circuit board could occur. 相似文献
54.
55.
M. Sinha H. Dutta S.K. Pradhan 《Physica E: Low-dimensional Systems and Nanostructures》2006,33(2):367-369
Nanocrystalline Mg–Zn-ferrite is prepared by ball milling the stoichiometric powder mixture of MgO, ZnO and α-Fe2O3. A non-stoichiometric ferrite phase is noticed to form after 3 h of milling when particles of starting materials became nano-sized. After 25 h of milling, stoichiometric ferrite phase is formed with 9 nm particle size. Post annealing study of ball-milled sample reveals that the nanocrystalline ferrite phase is stable up to 873 K and then starts to decompose into individual starting phases. However, heat treatment of unmilled stoichiometric powder mixture even at 1473 K for 1 h duration does not result in formation of stoichiometric Mg–Zn-ferrite phase. 相似文献
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58.
BGA焊点的质量控制 总被引:1,自引:0,他引:1
本文将结合实际工作中的一些体会和经验,就BGA焊点的接收标准、缺陷表现及可靠性等问题展开论述,特别对有争议的一种缺陷空洞进行较为详细透彻的分析,并提出一些改善BGA焊点质量的工艺改进的建议. 相似文献
59.
D.M. Rajkumar M. Manivel RajaR. Gopalan V. Chandrasekaran 《Journal of magnetism and magnetic materials》2008
Evolution of structure and magnetocaloric properties in ball-milled Gd5Si2Ge2 and Gd5Si2Ge2/0.1 wt% Fe nanostructured powders were investigated. The high-energy ball-milled powders were composed of very fine grains (70–80 nm). Magnetization decreased with milling time due to decrease in the grain size and randomization of the magnetic moments at the surface. The magnetic entropy change (ΔSM) was calculated from the isothermal magnetization curves and a maximum value of 0.45 J/kg K was obtained for 32 h milled Gd5Si2Ge2 alloy powder for a magnetic field change of 2 T while it was still low in Fe-contained alloy powders. The thermo-magnetic measurements revealed that the milled powders display distribution of magnetic transitions, which is desirable for practical magnetic refrigerant to cover a wide temperature span. 相似文献
60.