全文获取类型
收费全文 | 154篇 |
免费 | 6篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 2篇 |
综合类 | 1篇 |
化学工业 | 15篇 |
机械仪表 | 7篇 |
建筑科学 | 4篇 |
矿业工程 | 2篇 |
能源动力 | 6篇 |
轻工业 | 1篇 |
水利工程 | 1篇 |
石油天然气 | 2篇 |
无线电 | 41篇 |
一般工业技术 | 26篇 |
冶金工业 | 5篇 |
自动化技术 | 49篇 |
出版年
2022年 | 3篇 |
2021年 | 6篇 |
2020年 | 12篇 |
2019年 | 8篇 |
2018年 | 12篇 |
2017年 | 5篇 |
2016年 | 5篇 |
2015年 | 6篇 |
2014年 | 7篇 |
2013年 | 9篇 |
2012年 | 7篇 |
2011年 | 16篇 |
2010年 | 11篇 |
2009年 | 15篇 |
2008年 | 8篇 |
2007年 | 5篇 |
2006年 | 5篇 |
2005年 | 5篇 |
2004年 | 1篇 |
2003年 | 3篇 |
2002年 | 1篇 |
2001年 | 1篇 |
2000年 | 3篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1990年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 1篇 |
排序方式: 共有162条查询结果,搜索用时 15 毫秒
31.
This paper presents an improved automatic tuning method for stable processes using a modified relay in the presence of static load disturbances and measurement noise. The modified relay consists of a standard relay in series with a PI controller of unity proportional gain. The integral time constant of the PI controller of the modified relay is chosen so as to ensure a minimum loop phase margin of 30. A limit cycle is then obtained using the modified relay. Hereafter, the PID controller is designed using the limit cycle output data. The derivative time constant is obtained by maintaining the above mentioned loop phase margin. Minimizing the distance of Nyquist curve of the loop transfer function from the imaginary axis of the complex plane gives the proportional gain. The integral time constant of the PID controller is set equal to the integral time constant of the PI controller of the modified relay. The effectiveness of the proposed technique is verified by simulation results. 相似文献
32.
The aim of this paper is to evaluate and validate the average value of national or secondary standard of DC voltage, using four different methods; comparison, substitution, difference and ratio method. In the paper the custom made automation program developed to control the whole measurement process is discussed as well. The automation system has been developed in the view of achieving maximal quality of metrological performance i.e. minimum measurement uncertainty and maximum reliability. It is found that measurement automation provides reliable and efficient way for the calibration of Zener based standard of DC voltage. 相似文献
33.
The paper studies the capacities of time hopping ultra wideband (TH-UWB) systems by adopting orthogonal pulse-based modulation
schemes in a multipath environment with the consideration of multiple access interference (MAI) and inter symbol interference
(ISI). Recently, orthogonal pulse-based modulation schemes such as pulse shape modulation (PSM), biorthogonal PSM (BPSM) and
the combination of orthogonal pulse position modulation (OPPM) and BPSM have been proposed for UWB system to reduce ISI and
MAI. In this paper, we first investigate the influences of ISI and MAI on the capacities of TH-UWB systems in terms of signal-to-interference
and noise ratio (SINR) for high-order modulation schemes based on various sets of orthogonal pulses. How mutual information
varies with the number of multipath components (MPCs) is then analyzed. The complete mathematical analysis and simulation
results are provided in detail. When maximizing the mutual information, the Gaussian distribution approximate is assumed to
describe the characteristics of MAI and ISI. Simulation results are provided to verify the theoretical analysis. Some conclusions
are drawn thereafter, such as that capacity depends on the pulse patterns adopted and mutual information varies with inversely
proportional to the number of MPCs. We also observed that the capacities of UWB systems for OPPM-BPSM schemes are larger than
those of PSM and BPSM schemes. 相似文献
34.
Babita Kumari Shailja Sharma Nirupama Singh Anuradha Verma Vibha R. Satsangi Sahab Dass Rohit Shrivastav 《International Journal of Hydrogen Energy》2014
ZnO thin films, showing nano-ridges at the surface and the top layer embedded with metal (Ag/Au) nanoparticles (MNP), were obtained by sol-gel synthesis, using zinc acetate dihydrate [(CH3.COO)2Zn.2H2O] as precursor. The method involved prior synthesis of Ag and Au nanoparticles via biological reduction of AgNO3 and HAuCl4, respectively, using algae Spirulina platensis. The XRD analysis indicated dominant evolution of wurtzite ZnO phase. Low-angle shift in peaks, seen with nanoparticles embedded films, indicated partial diffusion of metals into ZnO lattice. Band gap energy was least affected and lied in the expected range. AFM and SEM analysis revealed the surface topography and morphology, while EDX analysis confirmed the elemental stoichiometry and existence of Ag/Au nanoparticles in samples. Significant gain in photoelectrochemical current using MNP embedded films is largely accountable to the improvement in electrical conductance and the role played by metal nanoparticles in charge-carrier separation, collection and transport. 相似文献
35.
Jos Prakash A. V Babita R. Jose Jimson Mathew Bijoy A. Jose 《International Journal of Electronics》2013,100(7):1142-1160
Hardware reconfigurability is an attractive solution for modern multi-standard wireless systems. This paper analyses the performance and implementation of an efficient triple-mode hexa-standard reconfigurable sigma-delta (∑?) modulator designed for six different wireless communication standards. Enhanced noise-shaping characteristics and increased digitisation rate, obtained by time-interleaved cross-coupling of ∑? paths, have been utilised for the modulator design. Power/hardware efficiency and the capability to acclimate the requirements of wide hexa-standard specifications are achieved by introducing an advanced noise-shaping structure, the dual-extended architecture. Simulation results of the proposed architecture using Hspice shows that the proposed modulator obtains a peak signal-to-noise ratio of 83.4/80.2/67.8/61.5/60.8/51.03 dB for hexa-standards, i.e. GSM????????/Bluetooth/GPS/WCDMA/WLAN/WiMAX standards with significantly less hardware and low operating frequency. The proposed architecture is implemented in 45 nm CMOS process using a 1 V supply and 0.7 V input range with a power consumption of 1.93 mW. Both architectural- and transistor-level simulation results prove the effectiveness and feasibility of this architecture to accomplish multi-standard cellular communication characteristics. 相似文献
36.
Gaihre B Khil MS Kang HK Kim HY 《Journal of materials science. Materials in medicine》2009,20(2):573-581
Current research explores formation of bone like apatite on gelatin coated magnetic iron oxide nanoparticles (GIOPs) to evaluate the bioactivity of the material. The GIOPs were soaked in simulated body fluid (SBF) and the apatite formation on the surface was investigated in regular interval of time. Fourier transform-infrared (FT-IR) and x-ray diffraction spectroscopic (XRD) analyses were done to investigate the chemical changes and field emission-scanning electron microscopic (FE-SEM) analysis was done to investigate the morphological changes occurring on the surface of the GIOPs after soaking in different time intervals. The kinetic studies of the apatite growth in SBF suggest that initially calcium and phosphorous ions were deposited to the surface of the GIOPs from the SBF leading to formation of amorphous Ca/P particles. Later, after 9 days of the incubation the amorphous particles were fused to form needle and blade like crystalline structures of bone like apatite. 相似文献
37.
Rhmann Wasiur Pandey Babita Ansari Gufran Ahmad 《Innovations in Systems and Software Engineering》2022,18(2):309-319
Innovations in Systems and Software Engineering - Software effort estimation is an essential task for software organizations to allocate resources efficiently during the development of software and... 相似文献
38.
Dash Bodhisattva Rup Suvendu Mohapatra Anjali Majhi Banshidhar Swamy M. N. S. 《Multimedia Tools and Applications》2018,77(12):15221-15250
Multimedia Tools and Applications - This paper proposes an ensemble of multi-layer perceptron (MLP) networks for side information (SI) generation in distributed video coding (DVC). In the proposed... 相似文献
39.
Wireless Networks - In the cooperative cognitive radio networks (CRN), often secondary user (SU) relays the information of primary user (PU) as a rewarding relay to improve diversity gain of PU... 相似文献
40.
Enhancing Data Rates of TH-UWB Systems Using M-ary OPPM-BPSM Modulation Scheme: A System Perspective
Sudhan Majhi A. S. Madhukumar A. B. Premkumar W. Xiang P. Richardson 《Wireless Personal Communications》2011,56(3):583-597
This paper proposes and studies a combined modulation scheme for time hopping ultra wideband (TH-UWB) radio system based on
orthogonal pulse position modulation (OPPM) and biorthogonal pulse shape modulation (BPSM). The proposed scheme offers a high
data rate with satisfactory system performance by using high-level multi-dimensional modulation schemes. It allows one to
increase the number of orthogonal pulses in each pulse position and, consequently, be able to adopt shorter pulse repetition
intervals than those used in conventional M-ary OPPM or M-ary biorthogonal PPM (BPPM) modulation schemes. The performance is analyzed by using characteristic function and Gaussian
approximation in additive white Gaussian and multipath scenarios, respectively. The proposed scheme reduces multiple access
interference considerably in multi-user environments. Finally, simulation results are provided to validate the theoretical
results. 相似文献