全文获取类型
收费全文 | 1445篇 |
免费 | 82篇 |
国内免费 | 80篇 |
专业分类
化学 | 267篇 |
晶体学 | 5篇 |
力学 | 22篇 |
综合类 | 1篇 |
数学 | 42篇 |
物理学 | 391篇 |
无线电 | 879篇 |
出版年
2024年 | 4篇 |
2023年 | 21篇 |
2022年 | 11篇 |
2021年 | 18篇 |
2020年 | 28篇 |
2019年 | 25篇 |
2018年 | 37篇 |
2017年 | 56篇 |
2016年 | 47篇 |
2015年 | 43篇 |
2014年 | 93篇 |
2013年 | 106篇 |
2012年 | 64篇 |
2011年 | 84篇 |
2010年 | 85篇 |
2009年 | 64篇 |
2008年 | 94篇 |
2007年 | 87篇 |
2006年 | 79篇 |
2005年 | 68篇 |
2004年 | 54篇 |
2003年 | 46篇 |
2002年 | 32篇 |
2001年 | 34篇 |
2000年 | 26篇 |
1999年 | 38篇 |
1998年 | 55篇 |
1997年 | 30篇 |
1996年 | 35篇 |
1995年 | 28篇 |
1994年 | 21篇 |
1993年 | 13篇 |
1992年 | 12篇 |
1991年 | 10篇 |
1990年 | 8篇 |
1989年 | 3篇 |
1988年 | 6篇 |
1987年 | 3篇 |
1986年 | 2篇 |
1985年 | 5篇 |
1984年 | 5篇 |
1983年 | 2篇 |
1982年 | 5篇 |
1981年 | 3篇 |
1980年 | 3篇 |
1979年 | 2篇 |
1977年 | 4篇 |
1976年 | 4篇 |
1974年 | 1篇 |
1973年 | 3篇 |
排序方式: 共有1607条查询结果,搜索用时 15 毫秒
81.
We report an electro-photo double modulation of the fermi level in a WSe2/graphene heterojunction. The heterojunction exhibits high ION/IOFF ratio (~103) in transfer characteristic in dark and distinct rectification behavior in output characteristic under light illumination, respectively. Time-dependent photoresponse reveals that the heterojunction has a considerable potential in the application of photodetection. Interestingly, an exotic current peak is observed in transfer characteristic under light illumination. This novel behavior is attributed to the tunable fermi level at the WSe2/graphene heterojunction by electro-photo double modulation. The results may be helpful to develop tunable photovoltaic optoelectronics based on van der Waals heterojunctions. 相似文献
82.
This paper presents a comprehensive modelling methodology for the electromagnetic immunity of integrated circuits (ICs) to direct power injection (DPI). The aim of this study is to predict the susceptibility of ICs by the means of simulations performed on an appropriate electrical model of different integrated logic cores located in the same die. These cores are identical from a functional point of view, but differ by their design strategies. The simulation model includes the whole measurement setup as well as the integrated circuit under test, its environment (PCB, power supply) and the substrate model of each logic core. Simulation results and comparisons with measurement results demonstrate the validity of the suggested model. Moreover, they highlight the interest of the aforementioned protection strategies against electromagnetic disturbances. 相似文献
83.
84.
B. Chakraborty 《International Journal of Electronics》2013,100(7):671-682
This paper describes a phase locked loop employing a low voltage VCO using modified ECL inverter cells. The VCO circuit employed, features a positive feed back scheme to improve the operating frequency. The phase detector used in the PLL also uses a positive feedback scheme to improve the locked range and to reduce supply voltage of operation of the entire circuit. An improvement of locked range of around 35% was obtained from circuit simulation (using PSPICE) as well as from practical circuit, using discrete components. The minimum supply voltage required here is 2.5 volts. Some biomedical applications of this PLL are also proposed. 相似文献
85.
详细地介绍了辉光放电质谱分析中的质谱干扰如同量异位素、多原子离子和多电荷离子干扰。从同位素选择、高分辨率仪器、碰撞诱导解离、离子源冷却、数学方法校正、放电气体更换和放电气体纯度提高等方面对辉光放电质谱的质谱干扰校正方法的现状进行了评述(引用文献共68篇)。 相似文献
86.
A novel current mode MOSFET-only structure with multi-input single-output (MISO) is proposed. The proposed circuit is free from passive circuit elements like resistors and capacitors and able to realize low-pass (LP), band-pass (BP), high-pass (HP), band-stop (BS) and all-pass (AP) filter functions with using the same circuit configuration. It is also important to note that the proposed filter has electronic tunability property. The proposed circuit is laid-out in the Cadence environment using 0.18 µm TSMC CMOS technology parameters. The layout area is only 408 μm2 and the power consumption is about 0.6 mW. Furthermore, to investigate the performance of the BP filter output of the proposed MISO filter, Monte Carlo and corner analyses are also presented. It is shown that the mismatches and the process variations cause only small deviations for the BP filter configuration. Furthermore, the noise performance of the proposed filter is also investigated. 相似文献
87.
A high-speed current conveyor based current comparator 总被引:1,自引:0,他引:1
R. Chavoshisani 《Microelectronics Journal》2011,42(1):28-32
In this paper, a new high-speed current mode comparator based on inherent current conveyor and positive feedback properties is presented. This novel approach has resulted in major reduction of the response time and hence a wide band application of the circuit. Simulation results using HSPICE and 0.18 μm CMOS technology with 1.8 V supply confirms a propagation delay of less than 0.4 ns in the high frequency range of 700 MHz with 158 μw power dissipation. Under the above conditions, the accuracy of the input current is as low as 50 nA. 相似文献
88.
Brent J. Maundy Ivars G. Finvers Peter Aronhime 《Analog Integrated Circuits and Signal Processing》2002,32(2):157-168
Two variants of a new current feedback amplifier (CFA) are presented in this paper. These CFAs are realized in CMOS technology and both are capable of working at low voltages. It is shown that one circuit performs better than the other by virtue of an increased impedance at its Z terminal achieved through the use of additional transistors. Analysis of both variants of the current conveyor and buffer that form the current feedback amplifier gives an insight into the location of primary poles and zeros of the CFAs. Simulation results indicate an overall gain bandwidth product in excess of 59 MHz and 102 MHz for each circuit at a gain of –10 and with a 3.3 V supply. Experimental results from a chip fabricated in a 0.35 m CMOS technology agree closely with the simulation results. 相似文献
89.
谐波电流与谐波阻抗的估算——工业与建筑电气系统谐波问题之二 总被引:1,自引:0,他引:1
本文介绍了电气设备发射的谐波电流大小以及与设备的哪些参数有关和如何估算大小,指明了近代出现电压型谐波源的谐波量更大,比较分析了单相负载中有不同的谐波源时,如何估算中性线电流IN的大小,简单介绍了谐波阻抗计算的难点所在。 相似文献
90.
本文着眼于楼宇供电用燃料电池发电系统的研究,针对中等容量(几千瓦至几百千瓦)的功率变换装置,分析其运行特点和对系统结构和控制的基本要求,提出具体的系统方案与控制策略,满足楼宇供电燃料电池发电系统的并网发电和独立运行的要求。最后给出了一个5kVA的燃料电池发电装置试验结果。 相似文献