全文获取类型
收费全文 | 9320篇 |
免费 | 788篇 |
国内免费 | 51篇 |
专业分类
电工技术 | 132篇 |
综合类 | 42篇 |
化学工业 | 2259篇 |
金属工艺 | 368篇 |
机械仪表 | 485篇 |
建筑科学 | 156篇 |
矿业工程 | 27篇 |
能源动力 | 352篇 |
轻工业 | 924篇 |
水利工程 | 42篇 |
石油天然气 | 29篇 |
武器工业 | 2篇 |
无线电 | 1547篇 |
一般工业技术 | 2212篇 |
冶金工业 | 599篇 |
原子能技术 | 93篇 |
自动化技术 | 890篇 |
出版年
2024年 | 13篇 |
2023年 | 140篇 |
2022年 | 208篇 |
2021年 | 337篇 |
2020年 | 238篇 |
2019年 | 238篇 |
2018年 | 324篇 |
2017年 | 342篇 |
2016年 | 421篇 |
2015年 | 363篇 |
2014年 | 468篇 |
2013年 | 650篇 |
2012年 | 658篇 |
2011年 | 850篇 |
2010年 | 596篇 |
2009年 | 558篇 |
2008年 | 454篇 |
2007年 | 404篇 |
2006年 | 346篇 |
2005年 | 274篇 |
2004年 | 277篇 |
2003年 | 239篇 |
2002年 | 183篇 |
2001年 | 172篇 |
2000年 | 178篇 |
1999年 | 162篇 |
1998年 | 255篇 |
1997年 | 144篇 |
1996年 | 122篇 |
1995年 | 72篇 |
1994年 | 95篇 |
1993年 | 60篇 |
1992年 | 49篇 |
1991年 | 36篇 |
1990年 | 30篇 |
1989年 | 28篇 |
1988年 | 19篇 |
1987年 | 11篇 |
1986年 | 20篇 |
1985年 | 11篇 |
1984年 | 11篇 |
1983年 | 11篇 |
1981年 | 6篇 |
1980年 | 7篇 |
1979年 | 6篇 |
1977年 | 7篇 |
1976年 | 9篇 |
1974年 | 7篇 |
1971年 | 7篇 |
1970年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
61.
A new current control scheme with the reference voltage estimation for a voltage-fed pulsewidth modulated (PWM) inverter is presented. This scheme is simple and can provide smaller current error than predictive control with the same switching frequency when the load parameters are mismatched.<> 相似文献
62.
A novel soft-switching two-switch flyback converter is proposed in this article. This converter is composed of two active power switches, a flyback transformer and two passive regenerative clamping circuits. The proposed converter has the advantages of a low-cost circuit configuration, a simple control scheme, high efficiency, and a wide operating range. The circuit topology, analysis, design considerations and experimental results of the new flyback converter are presented. 相似文献
63.
The quest for improved energy savings is driving research into power converter high-efficiency operation under extremely light-load conditions. The use of multiple output converters to satisfy circuit needs and cost requirements adds additional complication to the standby mode power-consumption problem. This is due to the difficulty of satisfying both good cross-regulation under various load conditions as well as high efficiency in the standby mode simultaneously; because topologies that exhibit a good cross-regulation performance, such as resonant converters, generally have a poor efficiency problem under extremely light-loads. A secondary side post regulator (SSPR) is proposed to reduce the standby power consumption and to improve the cross-regulation performance of single- controller multiple-output channel power converters. It is capable of reducing the power consumption of the power converter as well as the SSPR. The SSPR is analysed using its operational principles and small signal models. A 110?W experimental prototype was built to verify the standby power consumption and cross-regulation performance using the proposed SSPR. 相似文献
64.
Jong-Woo Park Yun-Gi Kim Il-Kwon Kim Kyu-Charn Park Kyu-Chan Lee Tae-Sung Jung 《Solid-State Circuits, IEEE Journal of》1999,34(11):1446-1453
Process integration of cell capacitors that can circumvent the usual difficulties of large topographic height difference and high-temperature process are presented. A 16 Mbit silicon-on-insulator (SOI) DRAM with a 0.3 μm design rule is successfully fabricated and analyzed for processing integrity and circuit performance based on process integration of the cell capacitor using the pattern-bonded SOI (PBSOI) technology. Measurements for the strobe access time (tRAC) acid the operation current (Iccl) show significant improvement (over 25%) for the SOI DRAM compared to those for the 16 Mbit bulk counterpart with the same circuit and layout. On the transistor side, ultra-low-voltage transistor technology using the body bias control schemes is also implemented and investigated. Devices with small leakage current and almost ideal subthreshold swing are obtained. The results give us guidance for transistor and process schematics for low-voltage DRAM application 相似文献
65.
Hyung-Min Park Ho-Young Jung Te-Won Lee Soo-Young Lee 《Electronics letters》1999,35(23):2011-2012
A method for directly extracting clean speech features from noisy speech is proposed. This process is based on independent component analysis (ICA) and a new feature analysis technique for reducing the computational complexity of the frequency domain ICA. For noisy speech signals recorded in real environments, this method yielded a considerable performance improvement 相似文献
66.
Dong Geon Lee Dong Hoe Kim Jae Myeong Lee Byeong Jo Kim Jun Young Kim Seong Sik Shin Hyun Suk Jung 《Advanced functional materials》2021,31(9):2006718
One of the most effective methods to achieve high-performance perovskite solar cells (PSCs) is to employ additives as crystallization agents or to passivate defects. Tri-iodide ion has been known as an efficient additive to improve the crystallinity, grain size, and morphology of perovskite films. However, the generation and control of this tri-iodide ion are challenging. Herein, an efficient method to produce tri-iodide ion in a precursor solution using a photoassisted process for application in PSCs is developed. Results suggest that the tri-iodide ion can be synthesized rapidly when formamidinium iodide (FAI) dissolved isopropyl alcohol (IPA) solution is exposed to LED light. Specifically, the photoassisted FAI–IPA solution facilitates the formation of fine perovskite films with high crystallinity, large grain size, and low trap density, thereby improving the device performance up to 22%. This study demonstrates that the photoassisted process in FAI dissolved IPA solution can be an alternative strategy to fabricate highly efficient PSCs with significantly reduced processing times. 相似文献
67.
Hong-Joon Yoon Dong-Min Lee Young-Jun Kim Sera Jeon Jae-Hwan Jung Sung Soo Kwak Jihye Kim SeongMin Kim Yunseok Kim Sang-Woo Kim 《Advanced functional materials》2021,31(23):2100649
Diverse touch experiences offer a path toward greater human–machine interaction, which is essential for the development of haptic technology. Recent advances in triboelectricity-based touch sensors provide great advantages in terms of cost, simplicity of design, and use of a broader range of materials. Since performance solely relies on the level of contact electrification between materials, triboelectricity-based touch sensors cannot effectively be used to measure the extent of deformation of materials under a given mechanical force. Here, an ion-doped gelatin hydrogel (IGH)-based touch sensor is reported to identify not only contact with an object but also deformation under a certain level of force. Switchable ionic polarization of the gelatin hydrogel is found to be instrumental in allowing for different sensing mechanisms when it is contacted and deformed. The results show that ionic polarization relies on conductivity of the hydrogels. Quantitative studies using voltage sweeps demonstrate that higher ion mobility and shorter Debye length serve to improve the performance of the mechanical stimuli-perceptible sensor. It is successfully demonstrated that this sensor offers dynamic deformation-responsive signals that can be used to control the motion of a miniature car. This study broadens the potential applications for ionic hydrogel-based sensors in a human–machine communication system. 相似文献
68.
The distributions of electric field and induced second‐order nonlinearity are analyzed in the periodic poling of optical fibers. A quasi‐phase matching efficiency for the induced nonlinearity is calculated in terms of both the electrode separation distance between the applied voltage and generalized electrode width for the periodic poling. Our analysis of the quasi‐phase matching efficiency implies that the conversion efficiency can be enhanced through adjusting the separation distance, and the electrode width can be maximized if the electrode width is optimized. 相似文献
69.
70.
In this letter, a Balun-bandpass filter (BPF) is proposed by using a dual-mode ring resonator. The Balun-BPF is not a simply combined or integrated component of a BPF and a Balun but a single BPF with the balun function. We obtained the proper balanced outputs and two-pole BPF characteristic by symmetrically placing the output ports at lambda/2 distance from each other on the dual-mode ring resonator. The fabricated Balun-BPF has a bandwidth of 40 MHz and an insertion loss of 2.4 dB at a center frequency of 2.45 GHz. The differences between the two outputs are 180-184deg in phase and within 1dB in magnitude. The measured frequency responses agree well with simulated ones. 相似文献