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排序方式: 共有122条查询结果,搜索用时 656 毫秒
1.
Weihua Jiang Zinsmeyer K. Less M. Schoenbach K.H. Kristiansen M. 《Electron Devices, IEEE Transactions on》1994,41(4):582-586
Results of electron-beam controlled switching experiments with switch samples of quartz crystal and polycrystalline zinc selenide (ZnSe) are presented. For switch samples of both materials, drastic reductions of the switch resistance were induced by the electron beam. The quartz sample showed very fast temporal response (less than 1 ns) with potential applicability for current control. The ZnSe samples, on the other hand, showed longer current transients (on the order of 10 ns) with exponential development of the switch resistance after the electron beam pulse 相似文献
2.
Recent advances in high-power ignitron development 总被引:2,自引:0,他引:2
Loree D.L. Giesselmann M.G. Kristiansen M. Shulski A.P. Kihara R. 《Electron Devices, IEEE Transactions on》1991,38(4):720-725
The authors describe the advances made in high-power ignitron switching capabilities in a comparison study between conventional size D and size E tubes, demountable experimental tubes, and the new NL-9000 (Richardson Electronics). The authors discuss the differences in tube design and the associated peak current and charge transfer capabilities and lifetime expectancies. The critical design criteria are the anode shape and placement in order to control the plasma and prevent prefires. Tube failure modes and recent studies on alternate ignitor schemes are presented. In addition, results of plasma diagnostics performed on a demountable ignitron with optical access to the discharge plasma are shown. Time-resolved images of the interference patterns from an optical Mach-Zehnder interferometer were recorded with a mechanical high-speed camera and evaluated with the help of image processing 相似文献
3.
J Br?ns-Poulsen NE Petersen M H?rder K Kristiansen 《Canadian Metallurgical Quarterly》1998,12(6):345-348
The antimicrobial activity of a combination of lactic acid and whey permeate fermented by a nisin-producing Lactococcus lactis strain was tested by the agar diffusion method using bacteria isolated from fish as test organisms. Lactic acid inhibited all bacterial strains studied, but nisin whey permeate inhibited Gram-positive bacteria only. The combination was more effective than lactic acid alone against Pseudomonas fluorescens and Staphylococcus hominis isolated from fish, and Pseudomonas aeruginosa ATCC9721 and Micrococcus luteus ATCC9341. 相似文献
4.
Molly S. Bazilchuk Takashi Sumigawa Takayuki Kitamura Zhiliang Zhang Helge Kristiansen Jianying He 《Advanced Engineering Materials》2018,20(7)
5.
We present a solution to the problem of tracking relative rotation in a leader-follower spacecraft formation using feedback from relative attitude only. The controller incorporates an approximate-differentiation filter to account for the unmeasured angular velocity. We show uniform practical asymptotic stability (UPAS) of the closed-loop system. For simplicity, we assume that the leader is controlled and that we know orbital perturbations; however, this assumption can be easily relaxed to boundedness without degrading the stability property. We also assume that angular velocities of spacecraft relative to an inertial frame are bounded. Simulation results of a leader-follower spacecraft formation using the proposed controller structure are also presented. 相似文献
6.
Spacecraft formation reconfiguration with collision avoidance 总被引:1,自引:0,他引:1
In this paper we present a behavioral control solution for reconfiguration of a spacecraft formation using the Null-Space Based (NSB) concept. The solution is task based, and aims to reconfigure and maintain a rigid formation while avoiding collisions between spacecraft. A model of relative translation is derived, together with a passivity-based sliding surface controller which globally stabilizes the equilibrium point of the closed-loop system. The NSB control method is implemented by giving each task different priorities and then calculating desired velocity and a Jacobian matrix for each spacecraft and each task. The velocity vector for each task is then projected into the null-space for higher prioritized tasks to remove conflicting velocity components. Simulation results are presented, showing that each spacecraft moves into the predefined formation without breaking any rules for the higher priority tasks, and all collisions are avoided. 相似文献
7.
Electrical characterization of individual metal‐coated polymer spheres used in isotropic conductive adhesives
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Hoang‐Vu Nguyen Jianying He Tore Helland Helge Kristiansen Knut E. Aasmundtveit 《应用聚合物科学杂志》2016,133(31)
Isotropic conductive adhesives (ICAs) filled with metal‐coated polymer spheres (MPS) have been proposed to improve the mechanical reliability compared to conventional ICAs filled with silver flakes. The electrical properties of MPS play an important role in the electrical performance of macroscopic MPS‐based ICAs. This article deals with the electrical characterization of individual MPS using a nanoindentation‐based flat punch method, in which the resistance and the deformation of single MPS were monitored simultaneously. Four groups of silver‐coated polymer spheres (AgPS) with identical polymer cores but different silver coating thicknesses were tested. The resistance of AgPS decreases gradually with increasing deformation degree of particles, and increases when the deformation of particles is reduced. In addition, the resistance of individual AgPS is dependent on the physical properties of the silver coating, such as thickness, uniformity, and porosity. The thicker the silver coating is, the lower and more stable the resistance of AgPS is. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43764. 相似文献
8.
Junhua Zhao Shijo Nagao Gregory M Odegard Zhiliang Zhang Helge Kristiansen Jianying He 《Nanoscale research letters》2013,8(1):541
Anisotropic conductive adhesives (ACAs) are promising materials used for producing ultra-thin liquid-crystal displays. Because the mechanical response of polymer particles can have a significant impact in the performance of ACAs, understanding of this apparent size effect is of fundamental importance in the electronics industry. The objective of this research is to use a coarse-grained molecular dynamics model to verify and gain physical insight into the observed size dependence effect in polymer particles. In agreement with experimental studies, the results of this study clearly indicate that there is a strong size effect in spherical polymer particles with diameters approaching the nanometer length scale. The results of the simulations also clearly indicate that the source for the increases in modulus is the increase in relative surface energy for decreasing particle sizes. Finally, the actual contact conditions at the surface of the polymer nanoparticles are shown to be similar to those predicted using Hertz and perfectly plastic contact theory. As ACA thicknesses are reduced in response to reductions in polymer particle size, it is expected that the overall compressive stiffness of the ACA will increase, thus influencing the manufacturing process. 相似文献
9.
The influence of magnetic fields on dielectric surface flashover 总被引:3,自引:0,他引:3
Korzekwa R. Lehr F.M. Krompholz H.G. Kristiansen M. 《Electron Devices, IEEE Transactions on》1991,38(4):745-749
The influence of low-amplitude magnetic fields, in a variety of configurations, on pulsed dielectric surface flashover has been investigated. These variations include DC magnetic fields; pulsed magnetic fields simulating conditions for magnetic self-insulation; and different environments (vacuum, ambient, gas, plasma), geometries, dielectric materials, and orientations of the magnetic field. For field amplitudes of 0.3 T, typically a doubling of the flashover voltage is observed, if the E ×B drift is away from the surface. For flashover in vacuum, it is sufficient to place permanent magnets in the cathode vicinity to increase the flashover voltage. The observations are consistent with the saturated surface secondary avalanche model and electron-induced gas desorption. The pulse shape of light emission during the prebreakdown phase depends on the orientation and amplitude of the magnetic field and shows that the electron trajectories above the surface are altered by magnetic fields 相似文献
10.
Antiproliferative properties of molecular regulators of lipid metabolism have been increasingly studied during recent years.
Discussion is ongoing concerning optimal treatment conditions and assays used for monitoring proliferation and cytotoxicity.
The objective of the present work was to optimize methods and treatment conditions used for studying antiproliferative effects
of fatty acids and analogs, represented by palmitic acid (PA) and the β-oxidation-restricted fatty acid analog tetradecylthioacetic
acid (TTA), in rat (BT4Cn) and human (D54Mg and GaMg) glioma cell lines. Changes in [3H]thymidine incorporation preceded changes in cell number in TTA-treated glioma cell cultures, and the growth inhibition was
more significantly expressed by [3H]thymidine incorporation than cell number. Addition of bovine serum albumin decreased cellular fatty acid uptake and reduced
the effects of TTA and PA on [3H]thymidine incorporation. Determination of the antiproliferative effect of TTA in BT4Cn cells by MTT conversion and [3H]thymidine incorporation yielded concordant results. TTA-mediated reduction in cell number corresponded to reduction in cellular
protein and total DNA content in BT4Cn cells. Reduced growth potential in TTA-treated multicellular D54Mg and GaMg spheroids
supported the findings from monolayer cultures. In conclusion, cell density, treatment period, fatty acid administration,
and methods for growth determination may profoundly influence the outcome of cell growth experiments. Thus, experimental conditions
should be carefully controlled when performing cell growth experiments, and effects on cell growth should preferably be confirmed
by different methods.
Karl Johan Tronstad and Kjetil Berge contributed equally to this article. 相似文献