全文获取类型
收费全文 | 4111篇 |
免费 | 566篇 |
国内免费 | 405篇 |
专业分类
化学 | 2886篇 |
晶体学 | 38篇 |
力学 | 192篇 |
综合类 | 47篇 |
数学 | 611篇 |
物理学 | 1308篇 |
出版年
2024年 | 12篇 |
2023年 | 77篇 |
2022年 | 134篇 |
2021年 | 132篇 |
2020年 | 145篇 |
2019年 | 157篇 |
2018年 | 154篇 |
2017年 | 127篇 |
2016年 | 199篇 |
2015年 | 186篇 |
2014年 | 264篇 |
2013年 | 298篇 |
2012年 | 339篇 |
2011年 | 321篇 |
2010年 | 238篇 |
2009年 | 223篇 |
2008年 | 264篇 |
2007年 | 219篇 |
2006年 | 209篇 |
2005年 | 173篇 |
2004年 | 143篇 |
2003年 | 124篇 |
2002年 | 148篇 |
2001年 | 125篇 |
2000年 | 74篇 |
1999年 | 69篇 |
1998年 | 62篇 |
1997年 | 41篇 |
1996年 | 38篇 |
1995年 | 44篇 |
1994年 | 48篇 |
1993年 | 35篇 |
1992年 | 35篇 |
1991年 | 41篇 |
1990年 | 31篇 |
1989年 | 16篇 |
1988年 | 15篇 |
1987年 | 14篇 |
1986年 | 9篇 |
1985年 | 16篇 |
1984年 | 8篇 |
1983年 | 6篇 |
1982年 | 6篇 |
1981年 | 8篇 |
1980年 | 6篇 |
1979年 | 6篇 |
1978年 | 5篇 |
1977年 | 5篇 |
1971年 | 5篇 |
1962年 | 3篇 |
排序方式: 共有5082条查询结果,搜索用时 22 毫秒
951.
Under the framework of drive-response systems, a new method of complete dislocated general hybrid projective synchronization (CDGHPS) is proposed. In this design, every state variable of drive system does not equal the corresponding state variable of response system, but equal other ones of response system while evolving in time. Especially, complete dislocated synchronization, dislocated anti-synchronization and projective dislocated synchronization can be considered all as the special cases of the proposed method. In addition, this method is applied to secure communication through chaotic masking, the unpredictability of the scaling factor in projective synchronization can additionally enhance the security of communication. In consideration of random white noise, we study the random white noise perturbing for the transmission of an information signal. Finally, eliminate noise using wavelet transform. Numerical simulations are given to show the effectiveness of these methods. 相似文献
952.
有界连通区域上Dirichlet空间及其算子 总被引:1,自引:0,他引:1
本文主要讨论了有界连通区域Dirichlet空间上Toeplitz算子的Fredholm性质,计算了符号在C1中的Toeplitz算子的本性谱和Fredholm指标. 相似文献
953.
954.
以Du Pont公司的商用Teflon FEP A型薄膜为例,通过热脉冲技术、等温表面电位衰减测量和开路热刺激放电电流谱分析等实验结果,讨论了经常温和高温电晕充电后样品厚度对薄膜驻极体的沉积电荷密度、薄膜驻极体的内电场、体电导率以及电荷储存稳定性的影响.通过热脉冲技术组合电导率温度曲线的测量,研究了在不同温度条件下样品厚度对沉积电荷层的平均电荷重心移动的影响.结果表明:在充电参数一定的条件下,随着膜厚的降低,储存电荷密度上升,但电荷稳定性有所下降.因此,合理地调控薄膜厚度,可以有效地优化驻极体的电荷储存能
关键词:
厚度
驻极体
电荷储存能力
电荷稳定性 相似文献
955.
Single crystalline GaN nanoribbons were synthesized through nitriding Ga2O3 thin films deposited on sapphire (0001) substrates by radio frequency magnetron sputtering. The component and structure of nanoribbons were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray (EDX), transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM). The flat and smooth ribbon-like nanostructures are high quality single crystalline hexagonal wurtzite GaN. The thickness and width-to-thickness ratio of the grown GaN nanoribbons are in the range of 8-15 nm and ∼5-10, respectively. 相似文献
956.
Properties of field quantum entropy evolution in the Jaynes--Cummings model with initial squeezed coherent states field
下载免费PDF全文
![点击此处可从《中国物理》网站下载免费的PDF全文](/ch/ext_images/free.gif)
The properties of the field quantum entropy evolution in a system of
a single-mode squeezed coherent state field interacting with a
two-level atom is studied by utilizing the complete quantum theory,
and we focus our attention on the discussion of the influences of
field squeezing parameter $\gamma $, atomic distribution angle
$\theta $ and coupling strength $g$ between the field and the atom
on the properties of the evolution of field quantum entropy. The
results obtained from numerical calculation indicate that the
amplitude of oscillation of field quantum entropy evolution
decreases with the increasing of squeezing parameter $\gamma $, and
that both atomic distribution angle $\theta $ and coupling strength
$g$ between the field and the atom can influence the periodicity of
field quantum entropy evolution. 相似文献
957.
针对窄线宽激光器输出谱线窄,难以被锁定的情况,利用F-P腔特有极窄线宽、高精细度特性对激光器谱线线宽实施压窄及频率锁定。通过设计实验方案并搭建锁频测试平台,利用F-P腔外部光反馈将窄线宽半导体激光器线宽压窄来提高锁频精度。通过监测正弦波调制下F-P腔对于4种不同直流电压下激光PZT扫频段的透射谱线,并对其分别进行解调和锁频精度测试,得到直流高压放大器电压为73 V时对窄线宽激光器进行扫频,激光器反馈锁频精度最高可达1.5 MHz。 相似文献
958.
959.
960.
Oligomers of l-lactic acid and citric acid (PLCA) were synthesized by reacting lactic acid with citric acid in the presence of stannous chloride. The chemical compositions of these multicarboxylated oligomers were verified by FT-IR and 1H-NMR spectroscopy. The thermal characteristics of the oligomers, such as glass transition temperature Tg, melting temperature Tm and melting enthalpy, were confirmed by DSC. The crystallinity of the oligomers were determined by DSC and WXRD. Meanwhile, the acid-base surface characteristics of PLCA have been determined by contact angle. The results implicated that these oligomers may be used to entrap the cospecies on PLLA surface in tissue engineering. 相似文献