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A.K. Verma Nainu P. Chaudhari Ashwani Kumar 《AEUE-International Journal of Electronics and Communications》2013,67(9):761-770
Performances of the conventional Butterworth step impedance lowpass filters (LPF) are significantly improved by placing transmission zero either closer to the cut-off frequency (fc) or away from it. It is achieved by using transverse resonance width of the capacitive line sections. We report method of designing transverse resonance type LPF (TR-LPF) for 5 to 11-pole filters. At fc = 2.5 GHz, we obtained selectivity in the range 113.3–56.66 dB/GHz and 20–60 dB rejection BW in the range 9.61–7.29 GHz. The TR-LPF can suppress the stopband signal by 60 dB up to 5fc. Insertion loss in passband is within 0.72 dB. Improved performance of TR-LPF can be designed for fc up to 7.5 GHz. 相似文献
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国际热核聚变实验反应堆是世界上在建的最大的磁约束聚变装置托克马克装置,通过对其中软X射线的测量,可实现等离子体辐射对锯齿、色骨模等磁流体现象的物理研究和成像反演。软X射线诊断系统就是用来检测软X射线的设备。由于热核聚变时恶劣电磁环境及远距离传输,在设计信号检测系统时必须进行电磁兼容设计,以降低系统噪声、提高检测精度。本文中使用的检测电路采用差分结构实现电流信号到电压信号的转换,重点研究检测电路的实现及其电磁兼容设计。从电磁抗干扰的三要素出发,结合实验测试,针对电磁干扰的特殊性,讨论了滤波电路设计、印制电路板(Printed Circuit Board,PCB)走线、电磁屏蔽及信号接地在系统中实现。本文采用32通道板卡集成设计;信号增益提高至107 V?A-1;放大器带宽达到120 k Hz。通过测试结果可以看出,信号噪声降至8 mV。通过优化设计提高了检测电路的集成度和放大电路的增益及带宽,同时降低了检测电路的噪声。 相似文献
35.
A Gaussian filter (GF) is the most commonly used low-pass filter of measuring surface roughness. However, undesirable distortions, called “end effects," occur near the end points of the data ends in GF. The transmission characteristics are one of the most important indicators that show the quality of a filter. Previously, it was only possible to obtain theoretical values for the transmission characteristics of filters whose weights were given by an explicit function. In recent years, it has also become possible to obtain the transmission characteristics of a filter whose weights are given by an implicit function. However, this method has a problem in that the values near the end points of the measurement data become significantly different from each other. The consequence is that end effects may occur in the filter outputs due to side effects of the periodic extension. In the case of a spline filter (SF) applied to open profiles, the transmission characteristics of a periodic SF with an end effect can be obtained uniquely. However, the transmission characteristics of a nonperiodic SF, which has no end effect, cannot be uniquely obtained. This results in a trade-off between the two states: end effects exist in a filter whose transmission characteristics can be obtained, and the transmission characteristics of a filter without end effects cannot be uniquely obtained. To address this problem, we propose a method for the GF processing that uses shearing, point symmetric extension, and periodic extension, and produces no end effect but allows the transmission characteristics to be obtained. Previously, there was a problem with the proposed method in that the rationale was unclear regarding how to determine the reference points for point symmetric extension. We resolved this and optimized the reference points. As a result, the proposed method was shown to be successful in not only resolving the end effects in the GF, but also obtaining the transmission characteristics. 相似文献
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Munetoshi Numada Takashi Nomura Kazuhisa Yanagi Kazuhide Kamiya Hatsuzo Tashiro 《Precision Engineering》2007,31(3):234-242
We propose a method of obtaining a more vertical step-edge-like cut-off characteristic of a low-pass filter, in which a mean line for the roughness profile is extracted and the computation time is significantly reduced. In order to make the cut-off characteristic more step-edge-like, attention is focused on the relationship between the spline filter order and mean line smoothness, and the order is made larger. This filter, i.e., the high-order spline filter, has extremely low end effects because it is an extension of the spline filter. Raising the order of the high-order spline filter to ∞ can also realize an ideal low-pass filter that has a step-edge-shaped cut-off characteristic. In addition, in order to reduce computation time, the high-order spline filter is calculated in the frequency domain. When several thousand data points are used, the spline filter requires a maximum of 1 h, whereas using the proposed high-order spline filter allows computation to be completed in less than 1 s. 相似文献
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This paper presents a method of finite-dimensional Markov process (FDMP) approximation for stochastic dynamical systems with time delay and numerical solutions of probability density functions of the systems. Solutions of probability density functions of time-delayed systems are rare in the literature. The FDMP method preserves the standard state space format of the system, and allows us to apply all the existing methods and theories for analysis and control of stochastic dynamical systems and to compute the probability density functions efficiently. The solutions of the FPK equation for a linear time-delayed stochastic system are presented. The effects of different spectral differentiation schemes for the FDMP method on the probability density functions are compared. 相似文献
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本文在推导阻抗匹配网络输入端反射系数极点解析式和分子多项式的基础上,编写了设计任意偶数阶具有Butterworth响应和Chebyshev响应阻抗匹配网络的计算机程序,程序用Forran语言编写,当输入匹配网络的阶数n=2m和阻抗变换比r=R2/R1对Chebyshev响应,通带容许的最大波纹αdB,计算机程序输出匹配带宽和匹配网络归一化元件值。 相似文献
40.
夏玉米可见/近红外光小波主成分提取与氮素含量神经网络检测 总被引:2,自引:0,他引:2
使用高光谱仪ASD Field Spec于吐丝期采集不同氮素处理的夏玉米叶片光谱,并进行对数变换处理;通过对"绿峰"(450~680nm)和"近红外反射平台"(760~1000nm)谱段光谱数据进行多尺度小波分解,获取第二层离散近似小波系数向量;采用主成分分析,从第二层离散近似小波系数向量中提取特征作为输入参数,建立对... 相似文献