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151.
Abstract The effects of buoyancy forces on the laminar boundary layer flow and heat transfer along vertically moving cylinders are analyzed for the cases of prescribed surface temperature and prescribed wall heat flux in power of streamwise distance. Local similarity solutions are obtained to show the effects of buoyancy parameters and the transverse curvature of the cylinder on the surface friction and heat transfer rate. 相似文献
152.
Adaptive neural dynamic surface control of MIMO stochastic nonlinear systems with unknown control directions 下载免费PDF全文
Milad Shahvali Javad Askari 《International Journal of Adaptive Control and Signal Processing》2017,31(1):97-121
In this paper, an adaptive neural output‐feedback control approach is considered for a class of uncertain multi‐input and multi‐output (MIMO) stochastic nonlinear systems with unknown control directions. Neural networks (NNs) are applied to approximate unknown nonlinearities, and K‐filter observer is designed to estimate unavailable system's states. Due to utilization of Nussbaum gain function technique in the proposed approach, the singularity problem and requirement to prior knowledge about signs of high‐frequency gains are removed, simultaneously. Razumikhin functional method is employed to deal with unknown state time‐varying delays, so that the offered control approach is free of common assumptions on derivative of time‐varying delays. Also, an adaptive neural dynamic surface control is developed; hence, explosion of complexity in conventional backstepping method is eliminated, effectively. The boundedness of all the resulting closed‐loop signals is guaranteed in probability; meanwhile, convergence of the tracking errors to adjustable compact set in the sense of mean quartic value is also proved. Finally, simulation results are shown to verify and clarify efficiency of the offered approach. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
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155.
The purpose of this paper is to present a multivariable linear parameter varying (LPV) controller with a gain scheduling Smith Predictor (SP) scheme applicable to open-flow canal systems. This LPV controller based on SP is designed taking into account the uncertainty in the estimation of delay and the variation of plant parameters according to the operating point. This new methodology can be applied to a class of delay systems that can be represented by a set of models that can be factorized into a rational multivariable model in series with left/right diagonal (multiple) delays, such as, the case of irrigation canals. A multiple pool canal system is used to test and validate the proposed control approach. 相似文献
156.
《Organic Electronics》2014,15(1):299-305
A direct comparison of charge transport and electronic traps in representative polymer–fullerene blend, poly (3-hexylthiophene) (P3HT) and 1-(3-methoxycarbonyl)-propyl-1-phenyl-(6,6)C61 (PCBM), is carried out in dark and illuminated conditions based on the measurements of temperature-dependent current–voltage characteristics. In dark condition, the charge transport presents a transition from Ohmic to trap-limited current. While the trap-filled space charge limited current is observed under illumination at the same applied bias. From evaluations of trap density and energy distribution by a differential method, it is reveal that the diverse charge transport in dark and illuminated conditions is mainly caused by the different trap states distribution, which strongly affects the space charges and the electrical field in P3HT: PCBM blends. 相似文献
157.
针对桌面灰尘检测在光照变化时有灰尘与无灰尘图像相似度区分界限不明显的问题,提出一种基于兰氏距离改进的图像相似度算法。该算法融合指数函数性质,将模板图与有灰尘和无灰尘图像之间的兰氏距离转换为(0,1]区间的相似度值,同时扩大相似度差值。为增强灰尘纹理特征信息,将灰度图进行拉普拉斯算子卷积,再用共生矩阵特征提取算法提取特征参数并将其组合成一维向量。用改进后的相似度算法计算模板图与待检测图的特征参数向量相似度,根据向量相似度判断桌面是否具有灰尘。实验结果表明在300~900 lux光照范围内,无灰尘图像之间的相似度高于90.01%,有灰尘与无灰尘图像之间的相似度低于62.57%。两种相似度的均值能够作为阈值,在光照变化时有效地判断桌面是否具有灰尘。 相似文献
158.
A control architecture for air to fuel ratio (AFR) control of gasoline engines designed to work with switching and/or wide range oxygen sensors, with the goal of minimizing calibration effort while meeting performance requirements, is described. A high bandwidth, dithered inner-loop reference tracking controller with pre-catalyst oxygen sensor feedback coupled with a low bandwidth setpoint tracking outer-loop with post catalyst oxygen sensor feedback, is used to control engine exhaust and O2 storage in the three-way catalyst (TWC), respectively. A total synthesis inspired design ensures that significant non-linearity in the system is handled through a coordinated and corrective action and expected response blocks in the open-loop, without burdening the closed loop controller. Calibration is achieved offline, through closed loop optimization using genetic algorithms, while simultaneously meeting performance and stability criteria with significantly reduced need for in-vehicle tuning. Experimental results show comparable emissions performance with the stock OEM AFR controller under warmed up conditions over a standard drive cycle. 相似文献
159.
Flexible solid-state dye sensitized solar cell is an important milestone for low-cost, large scale fabrication of dye-sensitized solar cells. Flexible solid-state dye-sensitized solar cell is fabricated for the first time on titanium substrates using D102 sensitizer and a sputtered platinum semi-transparent cathode. Devices are illuminated from the cathode side since titanium substrates are non-transparent. Due to rear-side illumination, significant proportion of radiation is absorbed and scattered by poly(3-hexylthiophene) and platinum, respectively. Limiting the amount of platinum and poly(3-hexylthiophene), up to a point, is found to enhance device efficiency. The amount of platinum and poly(3-hexylthiophene) is optimized on glass substrates before fabrication of flexible devices on titanium substrates. The rough surface of titanium substrates is smoothened until a mirror finish and the growth of a thin layer of native oxide enhanced the device efficiency. Under optimized conditions, an efficiency of 1.20% is obtained for devices fabricated on titanium foil substrates. The lower efficiency as compared to conventional devices is mainly due to light absorption/scattering from the poly(3-hexylthiophene) and platinum layers. 相似文献
160.
A robust system for backlit keyboard inspection is revealed. The backlit keyboard not only has changeable diverse colors but also has the laser marking keys. The keys on the keyboard can be divided into regions of function keys, normal keys, and number keys. However, there might have some types of defects:incorrect illuminating area, non-uniform illumination of specified inspection region (IR), and incorrect luminance and intensity of individual key. Since the illumination features of backlit keyboard are too complex to inspect for human inspector in the production line, an auto-mated inspection system for the backlit keyboard is proposed in this paper. The system was designed into the operation module and inspection module. A set of image processing methods were developed for these defects inspection. Some experimental results demonstrate the robustness and effectiveness of the proposed system. 相似文献