全文获取类型
收费全文 | 3408篇 |
免费 | 549篇 |
国内免费 | 360篇 |
专业分类
化学 | 2552篇 |
晶体学 | 41篇 |
力学 | 133篇 |
综合类 | 8篇 |
数学 | 341篇 |
物理学 | 1242篇 |
出版年
2024年 | 6篇 |
2023年 | 67篇 |
2022年 | 111篇 |
2021年 | 153篇 |
2020年 | 142篇 |
2019年 | 127篇 |
2018年 | 117篇 |
2017年 | 105篇 |
2016年 | 161篇 |
2015年 | 177篇 |
2014年 | 194篇 |
2013年 | 273篇 |
2012年 | 348篇 |
2011年 | 341篇 |
2010年 | 197篇 |
2009年 | 235篇 |
2008年 | 191篇 |
2007年 | 204篇 |
2006年 | 185篇 |
2005年 | 126篇 |
2004年 | 125篇 |
2003年 | 84篇 |
2002年 | 75篇 |
2001年 | 47篇 |
2000年 | 58篇 |
1999年 | 67篇 |
1998年 | 49篇 |
1997年 | 37篇 |
1996年 | 58篇 |
1995年 | 25篇 |
1994年 | 30篇 |
1993年 | 30篇 |
1992年 | 25篇 |
1991年 | 18篇 |
1990年 | 23篇 |
1989年 | 23篇 |
1988年 | 13篇 |
1987年 | 19篇 |
1986年 | 8篇 |
1985年 | 7篇 |
1984年 | 13篇 |
1983年 | 6篇 |
1982年 | 6篇 |
1981年 | 2篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1957年 | 2篇 |
排序方式: 共有4317条查询结果,搜索用时 15 毫秒
101.
102.
W. Yang K. Nelissen M. H. Kong Y. T. Li Y. M. Tian 《The European Physical Journal B - Condensed Matter and Complex Systems》2011,83(4):499-505
The angular and radial melting properties of two-dimensional classical systems consisting
of different types of particles confined in a parabolic trap are studied through modified
Monte Carlo simulations. A universal behavior of the angular melting process is found,
which occurs in multiple steps due to shell depended melting temperatures. The melting
sequence of the different shells is determined by two major factors: (1) the confinement
strength which each shell is subjected to, and (2) the specific structure of each shell.
Further, a continuous radial disordering of the particle types forming a single circular
shell is found and analyzed. This phenomenon has never been observed before in
two-dimensional mono-dispersive systems. This continuous radial disordering results from
the high energy barrier between different particle types in multi-species systems. 相似文献
103.
104.
Performance improvement of MEH-PPV:PCBM solar cells using bathocuproine and bathophenanthroline as the buffer layers 下载免费PDF全文
In this work, bathocuproine (BCP) and bathophenanthroline (Bphen), commonly used in small-molecule organic solar cells (OSCs), are adopted as the buffer layers to improve the performance of the polymer solar cells (PSCs) based on poly(2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene) (MEH-PPV): [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) bulk heterojunction. By inserting BCP or Bphen between the active layer and the top cathode, all the performance parameters are dramatically improved. The power conversion efficiency is increased by about 70% and 120% with 5-nm BCP and 12-nm Bphen layers, respectively, when compared with that of the devices without any buffer layer. The performance enhancement is attributed to BCP or Bphen (i) increasing the optical field, and hence the absorption in the active layer, (ii) effectively blocking the excitons generated in MEH-PPV from quenching at organic/aluminum (Al) interface due to the large band-gap of BCP or Bphen, which results in a significant reduction in series resistance (Rs), and (iii) preventing damage to the active layer during the metal deposition. Compared with the traditional device using LiF as the buffer layer, the BCP-based devices show a comparable efficiency, while the Bphen-based devices show a much larger efficiency. This is due to the higher electron mobility in Bphen than that in BCP, which facilitates the electron transport and extraction through the buffer layer to the cathode. 相似文献
105.
106.
Solid-state dye-doped materials are an attractive alternative to conventional liquid dye solution. In this study, the spectral characteristics of dye cresyl violet before and after intercalating into layered titanate nanosheets and forming a nanohybrid thin film were investigated by measuring absorption and fluorescence spectra. In addition, their nonlinear optical properties were studied using single beam z-scan technique under irradiation of low power continuous wave (CW) produced by DPSS laser with a wavelength of 532 nm. The nonlinear studying results reveal that the dye cresyl violet in solution has a negative nonlinear refractive index, but it reverses to positive after the dye is intercalated into layered titanate nanosheets with a negative nonlinear refractive index forming CV/HTO nanohybrid thin film. This method can provide a way to turn to reverse nonlinear refraction sign of the materials. 相似文献
107.
108.
This paper performs a numerical simulation of concentric-ring discharge structures within the scope of a two-dimensional diffusion--drift model at atmospheric pressure between two parallel circular electrodes covered with thin dielectric layers. With a relative high frequency the discharge structures present different appearances of ring structures within different radii in time due to the evolvement of the filaments. The spontaneous electron density distributions help understanding the formation and development of self-organized discharge structures. During a cycle the electron avalanches are triggered by the electric field strengthened by the feeding voltage and the residual charged particles on the barrier surface deposited in the previous discharges. The accumulation of charges is shown to play a dominant role in the generation and annihilation of the discharge structures. Besides, the rings split and unify to bring and annihilate rings which form a new discharge structure. 相似文献
109.
本文采用基于密度泛函理论的第一性原理全势能线性缀加平面波方法(FLAPW),分析了Bi2Te3-xSex体系中各原子自旋轨道耦合(SOI)的p1/2修正对体系性质的影响,并对Bi2Te3-xSex(x≤3)同晶化合物的电子特性进行系统的理论研究,首次计算出Bi2S
关键词:
2Te3-xSex(x≤3)同晶化合物')" href="#">Bi2Te3-xSex(x≤3)同晶化合物
第一性原理
电子结构
自旋轨道耦合 相似文献
110.
研究了TiN/SiC纳米多层膜中立方SiC(B1cubic SiC)的形成及其对TiN/SiC多层膜力学性能的影响.结果表明:在TiN/SiC多层膜中,非晶态的SiC层在厚度小于0.6nm时形成立方结构并与TiN形成共格外延生长的超晶格柱状晶,使多层膜产生硬度和弹性模量显著升高的超硬效应,最高硬度超过60GPa.SiC随着层厚的增加转变为非晶相,从而阻止了多层膜的共格外延生长,使薄膜呈现TiN纳米晶和SiC非晶组成的层状结构特征,同时多层膜的硬度和弹性模量下降.TiN/SiC纳米多层膜产生的超硬效应与立方
关键词:
立方碳化硅
TiN/SiC纳米多层膜
外延生长
超硬效应 相似文献