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61.
Ezis A. Liou L.L. Ikossi-Anastasiou K. Evans K.R. Stutz C.E. Jones R.L. 《Electron Device Letters, IEEE》1989,10(4):168-170
The fabrication is reported of a high-gain (Ga,Al)As/GaAs heterostructure bipolar transistor (HBT) with a p-spike-doped base that is depleted at equilibrium. The device structure, based on that proposed for a bipolar inversion-channel field-effect transistor (BICFET), was grown by molecular-beam epitaxy (MBE). Fabricated transistors, containing an AlAs/n-GaAs superlattice emitter layer, exhibited DC current gains of up to 500. Maximum current gains of tested devices occurred at collector current densities in the mid-103 A cm -2 range. It is postulated that the induced base in these transistors is formed predominantly by the forward-bias action on the base-emitter junction 相似文献
62.
Ohtsu M. Liou K.-Y. Burrows E.C. Burrus C.A. Jr. Eisenstein G. 《Lightwave Technology, Journal of》1989,7(1):68-76
The mode-hopping events in a 1.3-μm grating-tuned external-cavity laser are analyzed on the basis of interferometric measurements. The average frequency of mode hopping for a 7.5-cm external-cavity laser is estimated and is expressed as f c =2.7×106×exp [-1.7/(I /I th-1)] (hertz) for 0.07⩽(I /I th -1)⩽0.8 (I =injection current and I th =threshold current). The mode-hopping monitoring signal was negatively fed back to the laser using an automatic control circuit which maintained single-mode operation while the wavelength of the grating external-cavity laser was tuned 相似文献
63.
Control of tool-workpiece interaction force is of vital importance in automated assembly. Using a simple linear continuous model of an edge-following system to predict the appropriate accomodation gains in a force control loop, previous work has shown that force control by accomodation is feasible. Following up this work, this paper describes the analysis, simulation and implementation of an adaptive force control in a two-dimensional edge-following task with a PUMA 560 robot and wrist force sensor. First, a discrete-time model of an edge-following system is developed and then used as the plant; second, a model reference adaptive control (MRAC) scheme is applied to achieve both tracking and regulation purposes. The reference (tracking) model can be determined by experimental reference input and desired model output information; the reference (regulation) model can be obtained by simulation to smooth out the plant output and improve the augmented filtered plant-model error. Study is done on the values of the adaptation gains in the adaptive mechanism, and hence can be adjusted to insure the best plant output performance. 相似文献
64.
Chraplyvy A.R. Liou K.Y. Tkach R.W. Eisenstein G. Jhee Y.K. Koch T.L. Anthony P.J. Chakrabarti U.K. 《Electronics letters》1986,22(2):88-90
An external-cavity laser consisting of a 1.5 ?m-wavelength antireflection-coated DFB laser chip, a microscope objective and a mirror provides a stable, single-frequency, narrow-linewidth (?f=40 kHz) output. Because the laser operates in the strong feedback regime, it is immune to external optical perturbations. Single-longitudinal-mode operation is maintained by the DFB grating, and the linewidth is reduced by the extended passive cavity. 相似文献
65.
Nan-Chyuan Tsai Jiun-Sheng Liou Chih-Che Lin Tuan Li 《Sensors and actuators. A, Physical》2010,157(1):68-76
For micro-gyroscopes, the angular rate detection components have to oscillate forwards and backwards alternatively. An innovative design of micro-electromagnetic drive module is proposed to make a Π-type thin disc reciprocally and efficiently rotate within a certain of angular interval. Twelve EM (Electromagnetic) poles, with iron cores at the center and wound by electroplated copper wires, enclosing the thin disc are designed to provide the magnetic drive power. Isotropic etching technique is employed to fabricate the high-aspect-ratio trench, housing of the follow-up electroplated copper, so that the contact angle of wire against trench can be increased and the potential defect of cavities and pores within the wire can be prevented. On the other hand, a Π-type thin disc, with a central bearing and a set of auxiliary bushing, is designed to conduct the pitch motion as an angular excitation, in addition to spinning, is exerted on the gyroscope. That is, the angular motion of the disc is two-dimensional: spinning, driven by the EM poles, and tilting, to respond to the exerted angular rate due to Coriolis effect.The efficacy of the micro-magnetic drive module is verified by theoretical analysis and computer simulations by the commercial software, Ansoft Maxewll. In comparison with the conventional planar windings in micro-scale systems, the magnetic drive force is increased by 150%. 相似文献
66.
S.W. Chang T.-M. Liou K.F. Chiang G.F. Hong 《International Journal of Heat and Mass Transfer》2008,51(3-4):457-468
A novel heat transfer enhancement (HTE) roughness with V-shaped ribs and deepened scales is devised. Performances of heat transfer and pressure drop in a rectangular channel fitted with such HTE surfaces are experimentally examined for both forward and backward flows in the Re range of 1000–30000. Relative to the smooth-walled pipe flow conditions, HTE ratios for the present test channel with forward and backward flows, respectively, reach 9.5–13.6 and 9–12.3 for laminar flows and 6.8–6.3 and 5.7–4.3 for turbulent flows. Comparisons of heat transfer data, pressure-drop measurements and thermal performance factors with previous results collected from varieties of HTE devices demonstrate the superiorities of this compound HTE device. The decrease of HTE ratio as Re increases for turbulent flows, which is a common setback for several HTE elements, is almost diminished in the channel fitted with present compound HTE surfaces. Experimental correlations of heat transfer and friction coefficient for the tested channel with forward and backward flows are derived for design applications. 相似文献
67.
We have demonstrated a graded-index-rod external coupled-cavity (GRECC) laser with backface output through a partially transmitting external cavity mirror. Laser output is monitored from the backface in a transmitter module with double-loop feedback control which stabilizes output power and maintains single-frequency operation under CW and pseudorandom pulse modulation. 相似文献
68.
69.
J. J. Liou K. Lee S. M. Knapp K. B. Sundaram J. S. Yuan D. C. Malocha M. Belkerdid 《Solid-state electronics》1990,33(12):1629-1632
The quasi-static approximation, which assumes that free-carrier propagation delay in the semiconductor device is zero, is often used in device modeling. Consequently, the quasi-static model is adequate only for low-frequency excitations for which free-carrier propagation delay is very small compared to the variation of the excitations. This paper develops a non-quasi-static model suitable for metal-semiconductor junction diodes subjected to small-signal excitation. We show that the predictions of the non-quasi-static model agree more favourably with experimental data taken from Al---Si diodes than that of the quasi-static model, particularly when the frequency of the excitation is high. 相似文献
70.
Wu W.-C. Chao T.-S. Peng W.-C. Yang W.-L. Wang J.-C. Chen J.-H. Lai C.-S. Yang T.-Y. Lee C.-H. Hsieh T.-M. Liou J. C. 《Electron Device Letters, IEEE》2007,28(3):214-216
In this letter, high-performance and reliable wrapped select gate (WSG) polysilicon-oxide-nitride-oxide-silicon (SONOS) memory cells with multilevel and 2-bit/cell operation have been successfully demonstrated. The multilevel storage is easily obtained with fast program/erase speed (10 mus/5 ms) and low programming current (3.5 muA) for our WSG SONOS by a source-side injection. Besides the excellent reliability properties of our multilevel WSG-SONOS memory including unconsidered gate and drain disturbance, long charge retention (>150degC) and good endurance (>104) are also presented. This novel WSG-SONOS memory with a multilevel and 2-bit/cell operation can be used in future high-density and high-performance memory application 相似文献