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991.
Hardware complexity, active Tag power consumption, and Multiple Tags collection method are three critical parameters in all active radio frequency identification systems. In this work, both the MCU and RF operations are performed in single chip, which makes the Tag hardware smaller. A lot amount of energy is restored by setting Tags in the sleep mode in the most of times. Four commands are used for this system. At first, a unique ID is dedicated to each Tag by the ID allocation command. The polling command is implemented for searching desired Tags. By using of the ID clearing command, the object loses the passing permission for a given time or permanently. Utilizing the collection command, the information of all surrounding Tags are collected and monitored, simultaneously. The Carrier Sense Multiple Access method is used and its performance is evaluated. The maximum transmission range of 80 m at the output power of 4.5 dBm is obtained. An active Tag with unique ID is mounted on each vehicle. Receiver sensitivity of 97 dBm and current consumption of 1 $\mu \text{ A}$ in the sleep mode and 29.6 mA in the active mode are reported.  相似文献   
992.
A novel design for compact probe-fed wideband microstrip patch antenna for ultra-wideband (UWB) applications is proposed in this paper. The antenna consists of a folded ramp-shaped feed, trapezoidal patch and shorting pins. By adding two pins at end side of the patch, its size is miniaturized. The measured impedance bandwidth (VSWR  $\le $  2) of fabricated antenna is more than 130 % from 3.7 to 17.6 GHz. This antenna achieves an acceptable miniaturization and provides an excellent UWB impedance bandwidth with stable radiation patterns. It is shown by simulated results how the bandwidth can be considerably increased by introducing novel feeding method namely, the folded ramp-shaped feed. Likewise, the parametric study is performed to describe the characteristics of the proposed antenna. Moreover, good antenna performances such as radiation patterns, acceptable miniaturization and antenna gains over the operating band have been observed.  相似文献   
993.
Recent developments in biosensor and wireless technology have led to a rapid progress in wearable real time health monitoring. Unlike wired networks, wireless networks are subject to more packet loss and congestion. In this paper, we propose a congestion control and service prioritization protocol for real time monitoring of patients’ vital signs using wireless biomedical sensor networks. The proposed system is able to discriminate between physiological signals and assign them different priorities. Thus, it would be possible to provide a better quality of service for transmitting highly important vital signs. Congestion control is performed by considering both the congestion situation in the parent node and the priority of the child nodes in assigning network bandwidth to signals from different patients. Given the dynamic nature of patients’ health conditions, the proposed system can detect an anomaly in the received vital signs from a patient and hence assign more priority to patients in need. Simulation results confirm the superior performance of the proposed protocol. To our knowledge, this is the first attempt at a special-purpose congestion control protocol specifically designed for wireless biosensor networks.  相似文献   
994.
In the Journal of Cryptology (20(3):323–373, 2007), Blundo, D’Arco, De Santis and Stinson proposed a general model for unconditionally secure distributed oblivious transfer (DOT), where a sender has n secrets and a receiver is interested to one of them. We show that their “t-private weak one-round (k,m)-DOT $\binom{n}{1}$ ” protocol cannot prevent a receiver who attempts to obtain more than one secret. We present a modification to Blundo et al.’s protocol that fixes this problem.  相似文献   
995.
The aim of the present work was to study the effect of microstructure and microfibril formation on dyeability of polypropylene/poly(butylene terephthalate)/organoclay blend nanocomposite fibres. The blend nanocomposite samples with the same blend ratio but varying in organoclay content were prepared via melt compounding by using a co‐rotating twin screw extruder. The microfibrillar morphology and nanoclay partitioning were studied using scanning electron microscopy and transmission electron microscopy together with rheological results. The presence of nanoclay in the form of tactoids in the polypropylene matrix accelerated the dye sorption but much greater ultimate dye uptake could be achieved for the sample in which the major part of the platelets were preferentially located inside the poly(butylene terephthalate) fibrils. Although increasing the organoclay concentration increased the ultimate dye uptake, it limited the fibril formation at higher organoclay concentration. The utilisation of a compatibiliser was found to have an enhancing effect on ultimate dye uptake. This could be explained in terms of the interfacial role of the compatibiliser in improving microfibril formation as well as partitioning a fraction of nanoclay platelets inside the polypropylene matrix.  相似文献   
996.
Data detection in the presence of interference is one of the main challenges in multicarrier code division multiple access (MC-CDMA) communication systems. In this paper, a new detection technique for downlink MC-CDMA systems is proposed. This technique uses complex-valued multilayer neural networks at the receiver side. With the new definition for desired responses (±(1+J) instead of ±1, where $ J = \sqrt {{ - 1}} $ ), the convergence rate is increased (in the training process) regarding to saturation of imaginary output and the performance is increased because of increasing Euclidean distance of output neuron inputs in two states of desired outputs (with factor of $ \sqrt {2} $ ). The performance of the proposed method is improved further by considering two various saturation coefficients (in the activation function of output layer) in the training and test processes. Since the last performance improving lead to low convergence rate, this effect is compensated by correcting the coefficient of training rate in the output layer. Simulation results confirm the high convergence rate, low computational complexity, and also good performance of the proposed method in wide range of SNRs.  相似文献   
997.
The aging behavior of a thermomechanically processed Mo-Al-Nb transformation-induced plasticity steel with ultrafine microstructure was investigated using transmission electron microscopy and atom probe tomography (APT). Strain aging at 73 K (200 °C) for 1800 seconds led to a significant bake-hardening response (up to 222 MPa). Moreover, aging for 1800 seconds at room temperature after 4 pct pre-strain also revealed a bake-hardening response (~60 MPa). The experimental results showed the formation of carbon Cottrell atmospheres around dislocations and the formation of carbon clusters/fine carbides in the bainitic ferrite during aging. It is proposed that this is associated with the high dislocation density of bainitic ferrite with formation of a complex dislocation substructure after pre-straining and its high average carbon content (~0.35 at. pct). The segregation of carbon and substitutional elements such as Mn and Mo to the retained austenite/bainitic ferrite interface during aging was observed by APT. This segregation is likely to be the preliminary stage for Mo-C particles’ formation. The aging after pre-straining also induced the decomposition of retained austenite with formation of ferrite and carbides.  相似文献   
998.
This study integrates advanced mathematical modeling and experimental methodologies to investigate the simultaneous impact of modifications in the split ratio and molecular weight (MW) of chains on the rheological and mechanical properties of bimodal polyethylene (BiPE) resins. The outcomes underscored the viability of fine-tuning the molecular weight distribution (MWD) of a BiPE resin by augmenting the MW of high molecular weight (HMW) chains while simultaneously diminishing their proportion in the final alloy formulation. In addition, the experimental results illuminated the prospect of attaining a targeted melt flow index for the final polymers by elevating the MW of HMW chains alongside an increase in the proportion of low molecular weight chains. Significantly, these adjustments resulted in remarkable enhancements in the shear thinning index and strain hardening modulus of the fabricated resins.  相似文献   
999.
In this article, laminar flow-forced convective heat transfer of Al2O3/water nanofluid in a triangular duct under constant wall temperature condition is investigated numerically. In this investigation, the effects of parameters, such as nanoparticles diameter, concentration, and Reynolds number on the enhancement of nanofluids heat transfer is studied. Besides, the comparison between nanofluid and pure fluid heat transfer is achieved in this article. Sometimes, because of pressure drop limitations, the need for non-circular ducts arises in many heat transfer applications. The low heat transfer rate of non-circular ducts is one the limitations of these systems, and utilization of nanofluid instead of pure fluid because of its potential to increase heat transfer of system can compensate this problem. In this article, for considering the presence of nanoparticl: es, the dispersion model is used. Numerical results represent an enhancement of heat transfer of fluid associated with changing to the suspension of nanometer-sized particles in the triangular duct. The results of the present model indicate that the nanofluid Nusselt number increases with increasing concentration of nanoparticles and decreasing diameter. Also, the enhancement of the fluid heat transfer becomes better at high Re in laminar flow with the addition of nanoparticles.  相似文献   
1000.
There has been a growing interest to model and analyze Vehicle-Bridge Interaction (VBI) of intricate vehicles on bridges. The objective of such an analysis is to realistically investigate the dynamic effects of moving vehicles particularly in case of high-speed trains, where the vehicle acceleration is a design criterion and should be calculated appropriately. One method of analysis is to eliminate the wheel degrees of freedom (DOF) that are in direct contact with the bridge surface resulting in a VBI element, which is a modified beam element acted upon directly by wheel(s) of a running vehicle. The contact force is the mutual force between the wheel and the bridge. The available formulation in the literature is used to formulate the contact forces, which are related to those in the beam element DOFs by the Hermitian interpolation functions. Considering suitable interpolation functions between the beam element displacement vector and those for contact points and also a new formulation for the contact points, a new formulation is proposed for the structural properties of the VBI element, resulting in a new element capable of capturing bridge and vehicle responses more realistically. A study is conducted on the model variables and their effects on the bridge dynamic amplification factor and also bridge and vehicle accelerations, in order to compare the new VBI method with the existing one. The studied parameters include vehicle and bridge damping, frequency parameter, system mass parameter, and a new parameter called vehicle mass parameter. Results generally demonstrate noticeable differences particularly for high speed vehicles. In addition, it is observed that the effect of shear deformations in a simply-supported bridge might not be negligible and should be considered for moving vehicle analysis. For double girder open-deck steel railway bridges, the difference in midspan deflection of models including or excluding shear deformation can vary from 18% to 8% for 4.0 m and 30.0 m spans, respectively, for a sample vehicle.  相似文献   
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