全文获取类型
收费全文 | 3182篇 |
免费 | 414篇 |
国内免费 | 149篇 |
专业分类
化学 | 361篇 |
晶体学 | 23篇 |
力学 | 121篇 |
综合类 | 5篇 |
数学 | 139篇 |
物理学 | 801篇 |
无线电 | 2295篇 |
出版年
2024年 | 6篇 |
2023年 | 9篇 |
2022年 | 21篇 |
2021年 | 45篇 |
2020年 | 57篇 |
2019年 | 54篇 |
2018年 | 56篇 |
2017年 | 105篇 |
2016年 | 143篇 |
2015年 | 170篇 |
2014年 | 285篇 |
2013年 | 204篇 |
2012年 | 335篇 |
2011年 | 367篇 |
2010年 | 281篇 |
2009年 | 263篇 |
2008年 | 240篇 |
2007年 | 199篇 |
2006年 | 203篇 |
2005年 | 125篇 |
2004年 | 120篇 |
2003年 | 114篇 |
2002年 | 68篇 |
2001年 | 33篇 |
2000年 | 36篇 |
1999年 | 42篇 |
1998年 | 34篇 |
1997年 | 37篇 |
1996年 | 16篇 |
1995年 | 22篇 |
1994年 | 7篇 |
1993年 | 9篇 |
1992年 | 9篇 |
1991年 | 10篇 |
1990年 | 3篇 |
1989年 | 5篇 |
1988年 | 4篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1979年 | 1篇 |
1977年 | 1篇 |
排序方式: 共有3745条查询结果,搜索用时 203 毫秒
1.
《电子技术与软件工程》2015,(8)
太阳能光伏能够提供较为稳定的直流电源,是目前最受欢迎的绿色能源之一;而LED(发光二极管)则是直流电控制光源,两者的结合已有诸多研究。本文设计了一款单片机控制和光自动控制相结合的太阳能装饰灯,集美观、实用、节能等理念于一体。 相似文献
2.
In this work, simple n-type electrode structures were used to enhance the electrical and optical performances of fully packaged commercially mass-produced vertical-geometry light-emitting diodes (VLEDs). The forward bias voltage of the VLED with a Y-pattern electrode increased less rapidly than that of VLEDs with a reference electrode. The VLEDs with the reference and Y-pattern electrodes exhibited forward voltages of 2.93±0.015 and 2.89±0.015 V at 350 mA and 3.77±0.015 and 3.53±0.015 V at 2000 mA, respectively. The VLEDs with the Y-pattern electrode resulted in a higher light output than the VLEDs with the reference electrode with increase in the drive current to 2000 mA. The emission images showed that the VLEDs with the Y-pattern electrode exhibited better current spreading behavior and lower junction temperatures than the VLEDs with the reference electrode. With increase in the current from 350 to 2000 mA, the VLEDs with the Y-pattern electrode experienced a 39.4% reduction in the wall plug efficiency, whereas the VLEDs with the reference electrode suffered from a 43.3% reduction. 相似文献
3.
Naphthalimide‐phthalimide derivative based photoinitiating systems for polymerization reactions under blue lights
下载免费PDF全文
![点击此处可从《Journal of polymer science. Part A, Polymer chemistry》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Pu Xiao Frédéric Dumur Jing Zhang Bernadette Graff Didier Gigmes Jean Pierre Fouassier Jacques Lalevée 《Journal of polymer science. Part A, Polymer chemistry》2015,53(5):665-674
Naphthalimide‐phthalimide derivatives (NDPDs) have been synthesized and combined with an iodonium salt, N‐vinylcarbazole, amine or 2,4,6‐tris(trichloromethyl)‐1,3,5‐triazine to produce reactive species (i.e., radicals and cations). These generated reactive species are capable of initiating the cationic polymerization of epoxides and/or the radical polymerization of acrylates upon exposure to very soft polychromatic visible lights or blue lights. Compared with the well‐known camphorquinone based systems used as references, the novel NDPD based combinations employed here demonstrate clearly higher efficiencies for the cationic polymerization of epoxides under air as well as the radical polymerization of acrylates. Remarkably, one of the NDPDs (i.e., NDPD2) based systems is characterized by an outstanding reactivity. The structure/reactivity/efficiency relationships of the investigated NDPDs were studied by fluorescence, cyclic voltammetry, laser flash photolysis, electron spin resonance spin trapping, and steady state photolysis techniques. The key parameters for their reactivity are provided. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 665–674 相似文献
4.
5.
6.
7.
美国固体照明技术进展概况 总被引:2,自引:0,他引:2
介绍了美国能源部于2002年开始实施的固体照明(SSL)技术的"下一代照明计划".同时对美国SSL技术的研发、生产和使用现状以及召开学术会议的情况做了叙述. 相似文献
8.
LED交通信号灯系统的硬件设计 总被引:1,自引:0,他引:1
LED交通信号灯是传统交通信号灯的理想换代产品,文中介绍了一种LED交通信号灯系统的硬件设计方案,利用电流环具有光电隔离、抗干扰能力强、通信距离远的优点,结合串行移位、串并转换的数据传输方式,实现了对信号灯的远程弱电控制,并且能够直接实现倒计时显示功能.系统连线简单、安装方便、功能扩充性好,实现了亮度的自动控制.采用这种远程弱电隔离控制方式后,避免了传统的强电控制方式下可控硅容易损坏、系统故障率较高的缺陷,从而可以大大提高系统的可靠性. 相似文献
9.
10.
LIULu FANGuang-han LIAOChang-jun 《半导体光子学与技术》2004,10(2):86-92
A simple model of the graded heterojunction in AIGalnP compound semiconductors was introduced to analyze the band profile. The band profiles are analyzed with the different grading ways but the same grading length and under the different doping densities. The effect of the different grading lengths on the surplus of the potential of the spike to the potential of N region are also analyzed under the different doping densities. Through the experiments, it proves that the performances of high brightness light emitting diodes can be improved by the effects of the graded heterojunction. 相似文献