全文获取类型
收费全文 | 125篇 |
免费 | 63篇 |
国内免费 | 26篇 |
专业分类
化学 | 54篇 |
晶体学 | 1篇 |
力学 | 13篇 |
数学 | 18篇 |
物理学 | 128篇 |
出版年
2023年 | 4篇 |
2022年 | 7篇 |
2021年 | 1篇 |
2019年 | 10篇 |
2018年 | 4篇 |
2017年 | 4篇 |
2016年 | 3篇 |
2015年 | 3篇 |
2014年 | 9篇 |
2013年 | 7篇 |
2012年 | 6篇 |
2011年 | 10篇 |
2010年 | 8篇 |
2009年 | 6篇 |
2008年 | 16篇 |
2007年 | 5篇 |
2006年 | 16篇 |
2005年 | 19篇 |
2004年 | 21篇 |
2003年 | 9篇 |
2002年 | 12篇 |
2001年 | 13篇 |
2000年 | 9篇 |
1999年 | 1篇 |
1998年 | 3篇 |
1997年 | 3篇 |
1992年 | 2篇 |
1989年 | 3篇 |
排序方式: 共有214条查询结果,搜索用时 15 毫秒
131.
A Passively Mode-Locked Diode-End-Pumped Nd:YAG Laser with a Semiconductor Saturable Absorber Mirror Grown by Metal Organic Chemical Vapour Deposition 下载免费PDF全文
We report the experimentM results of a mode-locked diode-end-pumped Nd:YAG laser with a semiconductorsaturable absorber mirror (SESAM) from which we achieved a lOps pulse duration at 150MHz repetition rate.The SESAM was grown by metal organic chemical vapour deposition at low temperature. The recovery time wasmeasured to be 0.5 ps, indicating the potential pulse compression to sub-picoseconds. 相似文献
132.
Negative Dispersion Mirrors in Ta2O5/SiO2 for Femtosecond Ti:Sapphire Lasers by Using Gires-Tournois Interferometers 下载免费PDF全文
We design and experimentally demonstrate some negative dispersion mirrors with optimized Gires-Zournois interferometers. The mirror structure is composed of 38 alternating Ta2 O5 and SiO2 layers and could be regarded as two sections: high-reflectivity section consisting of a series of quarter-wavelength optical thickness stacks and negative-dispersion section consisting of only 13 layers. The designed mirrors exhibit the expected performance.These mirrors were fabricated by using ion beam sputtering. By adopting such mirrors, dispersion of a modelocked femtosecond Ti:sapphire laser has been compensated for mostly. With two series of the mirrors, 32 fs and 15 fs pulses have been obtained respectively. 相似文献
133.
134.
We present a compact and high output power diode end-pumped Nd:YAG laser which operates at the wavelength of 1123 nm. Continuous wave (CW) laser output of 2.6 W was achieved at the incident pump power of 15.9 W, indicating an overall optical-optical conversion efficiency of 16.4%, and the slope efficiency was 18%. 相似文献
135.
数学概念教学是数学教学的重要组成部分之一,其在教学中的意义是不言而喻的.不过,在概念教学中也时常会出现了“重结论,轻过程”的现象,使学生对概念的理解难以深入.为改变这一现状,教师应化“讲授”为“探究”,多引导学生参与概念的生成,让学生“学懂学会”,从而可以应用概念解决实际问题,以此提升概念教学的有效性. 相似文献
136.
137.
138.
We investigate SrBi2 Ta2 O9 (SBT) films prepared by the sol-gel spin method with different spin rates or different anneal conditions for the first layer of SBT, as promising ferroelectric layer materials applied to ferroelectric random access memory (FeRAM). All the specimens in this experiment have similar SBT crystal orientations of (115), (020), (220), and (135). The Pt/SBT/Pt capacitor with coating of 3000rpm spin rate has a perfect rectangle shape of hysteresis loops, remanent polarization of 7.571μC/cm^2 and coercive voltage of 0.816 V at 5 V voltage amplitude. These characteristics are better than those with coating of 3500rpm spin rate, which is attributed to the influence for thickness and grain size of the film from depressed spin rate. Slow-rate anneal in the furnace for the first layer of SBT can improve the crystallization processes and properties for SBT layers slightly, compared with rapid thermal annealing. The ion damage from etching for the top electrode can influence leakage current characteristics of the Pt/SBT/Pt capacitor at positive voltage bias. 相似文献
139.
140.
用碳酰肼的水溶液与高氯酸锰的水溶液反应制备了一种新型配物。用元素分析、红外光谱分析和 DSC分析对其进行了结构表征 ,通过 X-射线四圆衍射分析测定了它的分子结构 ,其分子式可表示为 [Mn( CHZ) 3]( Cl O4) 2 。该晶体属于单斜晶系 ,P2 1 / n空间群 ,晶胞参数为 :a=1 .0 1 97( 2 ) nm,b=0 .85 93( 1 ) nm,c=2 .1 41 2 ( 3)nm,b=1 0 0 .86°,V=1 .842 6 ( 5 ) nm3,Z=4。分析结果表明 ,碳酰肼分子通过其羰基氧原子和一个端位氮原子与中心锰离子配位形成五元环结构 ,分子中共有三个这样的五元环结构 ,使得该配合物结构稳定 ,具有用作含能材料的可能性。 相似文献