全文获取类型
收费全文 | 1631篇 |
免费 | 822篇 |
国内免费 | 461篇 |
专业分类
化学 | 1118篇 |
晶体学 | 33篇 |
力学 | 44篇 |
综合类 | 23篇 |
数学 | 30篇 |
物理学 | 1666篇 |
出版年
2024年 | 8篇 |
2023年 | 26篇 |
2022年 | 84篇 |
2021年 | 90篇 |
2020年 | 111篇 |
2019年 | 69篇 |
2018年 | 95篇 |
2017年 | 110篇 |
2016年 | 125篇 |
2015年 | 123篇 |
2014年 | 212篇 |
2013年 | 244篇 |
2012年 | 190篇 |
2011年 | 191篇 |
2010年 | 173篇 |
2009年 | 105篇 |
2008年 | 105篇 |
2007年 | 125篇 |
2006年 | 110篇 |
2005年 | 115篇 |
2004年 | 87篇 |
2003年 | 68篇 |
2002年 | 56篇 |
2001年 | 47篇 |
2000年 | 38篇 |
1999年 | 32篇 |
1998年 | 24篇 |
1997年 | 25篇 |
1996年 | 23篇 |
1995年 | 23篇 |
1994年 | 18篇 |
1993年 | 14篇 |
1992年 | 11篇 |
1991年 | 7篇 |
1990年 | 6篇 |
1989年 | 8篇 |
1988年 | 5篇 |
1987年 | 4篇 |
1986年 | 2篇 |
1984年 | 1篇 |
1982年 | 1篇 |
1981年 | 3篇 |
排序方式: 共有2914条查询结果,搜索用时 78 毫秒
61.
Frequency and voltage-dependent electrical and dielectric properties of Al/Co-doped PVA/p-Si structures at room temperature
下载免费PDF全文
![点击此处可从《中国物理 B》网站下载免费的PDF全文](/ch/ext_images/free.gif)
In order to investigate of cobalt-doped interracial polyvinyl alcohol (PVA) layer and interface trap (Dit) effects, A1/p- Si Schottky barrier diodes (SBDs) are fabricated, and their electrical and dielectric properties are investigated at room temperature. The forward and reverse admittance measurements are carded out in the frequency and voltage ranges of 30 kHz-300 kHz and -5 V-6 V, respectively. C-V or er-V plots exhibit two distinct peaks corresponding to inversion and accumulation regions. The first peak is attributed to the existence of Dit, the other to the series resistance (Rs), and interfacial layer. Both the real and imaginary parts of dielectric constant (er and err) and electric modulus (Mr and Mrr), loss tangent (tan~), and AC electrical conductivity (aac) are investigated, each as a function of frequency and applied bias voltage. Each of the M~ versus V and Mrr versus V plots shows a peak and the magnitude of peak increases with the increasing of frequency. Especially due to the Dit and interfacial PVA layer, both capacitance (C) and conductance (G/w) values are strongly affected, which consequently contributes to deviation from both the electrical and dielectric properties of A1/Co-doped PVA/p-Si (MPS) type SBD. In addition, the voltage-dependent profile of Dit is obtained from the low-high frequency capacitance (CLF-CHF) method. 相似文献
62.
63.
Sheng Yang Antonio Gaetano Ricciardulli Dr. Shaohua Liu Dr. Renhao Dong Dr. Martin R. Lohe Alfons Becker Marco A. Squillaci Prof. Paolo Samorì Prof. Klaus Müllen Prof. Xinliang Feng 《Angewandte Chemie (International ed. in English)》2017,56(23):6669-6675
To bridge the gap between laboratory-scale studies and commercial applications, mass production of high quality graphene is essential. A scalable exfoliation strategy towards the production of graphene sheets is presented that has excellent yield (ca. 75 %, 1–3 layers), low defect density (a C/O ratio of 21.2), great solution-processability, and outstanding electronic properties (a hole mobility of 430 cm2 V−1 s−1). By applying alternating currents, dual exfoliation at both graphite electrodes enables a high production rate exceeding 20 g h−1 in laboratory tests. As a cathode material for lithium storage, graphene-wrapped LiFePO4 particles deliver a high capacity of 167 mAh g−1 at 1 C rate after 500 cycles. 相似文献
64.
W. Winiarczyk 《光谱学快报》2013,46(8):1165-1175
A thin copper foil placed diagonally in a cylindrical copper hollow cathode undergoes fast erosion caused by cathode sputtering. Changes in the foil shape are related to current distribution along the hollow cathode axis. The experimental results aid in understanding the increase in spectral lines intensities emitted from conical bottom hollow cathode lamps. 相似文献
65.
Ling Wang Xiao-Tong Wang Jia-Huan Zhong Dr. Kang Xiao Dr. Ting Ouyang Prof. Zhao-Qing Liu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(18):5796-5802
The high charge–discharge voltage gap is one of the main bottlenecks of zinc–air batteries (ZABs) because of the kinetically sluggish oxygen reduction/evolution reactions (ORR/OER) on the oxygen electrode side. Thus, an efficient bifunctional catalyst for ORR and OER is highly desired. Herein, honeycomb-like MnCo2O4.5 spheres were used as an efficient bifunctional electrocatalyst. It was demonstrated that both ORR and OER catalytic activity are promoted by MnIV-induced oxygen vacancy defects and multiple active sites. Importantly, the multivalent ions present in the material and its defect structure endow stable pseudocapacitance within the inactive region of ORR and OER; as a result, a low charge–discharge voltage gap (0.43 V at 10 mA cm−2) was achieved when it was employed in a flexible hybrid Zn-based battery. This mechanism provides unprecedented and valuable insights for the development of next-generation metal–air batteries. 相似文献
66.
Dr. Shiyong Zuo Dr. Xijun Xu Prof. Shaomin Ji Zhuosen Wang Dr. Zhengbo Liu Prof. Jun Liu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(3):830-860
As concerns about the safety of lithium-ions batteries (LIBs) increases, aqueous zinc-ion batteries (ZIBs) with a lower cost, higher safety, and higher co-efficiency have attracted more and more interest. However, finding suitable cathode materials is still an urgent problem in ZIBs. In recent years, a lot of significant works have been reported, including manganese-based cathodes, vanadium-based cathodes, Prussian blue analog-based materials, and sustainable quinone cathodes. In this review, some typical cathode materials are introduced. The detailed storage mechanisms and methods for improving the reaction kinetics of the zinc ions are summarized. Finally, the issues, challenges, and the research directions are provided. 相似文献
67.
Dr. Ngoc-Anh Tran Nhan Do Van Thanh Prof. My Loan Phung Le 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(36):9198-9217
Magnesium batteries, like lithium-ion batteries, with higher abundance and similar efficiency, have drawn great interest for large-scale applications such as electric vehicles, grid energy storage and many more. On the other hand, the use of organic electrode materials allows high energy-performance, metal-free, environmentally friendly, versatile, lightweight, and economically efficient magnesium storage devices. In particular, the structural diversity and the simple activity of organic molecules make redox properties, and hence battery efficiency, easy to monitor. While organic magnesium batteries still in their infancy, this field becomes more and more promising because significant results were reported. To summarize the achievements in studies on organic cathodes for magnesium systems, their synthesis is discussed, combined with electrode design to provide the basis for controlling the electrochemical properties. Moreover, the techniques to synthesize organic materials with high-yield are mentioned. Finally, potential problems and prospects are explored to further improve organic cathodes. 相似文献
68.
《International journal of quantum chemistry》2018,118(15)
This article presents a discussion about the formalism, which might be associated to a general Quantum quantitative structure–properties relations operator, appearing in a Boltzmann‐like exponential form, which is based in turn on the definition of the concept of thermal voltage, applied to thermally scaled electronic density functions. Three practical numerical examples are presented, corresponding to the calculation of the polarization angle in assorted chiral molecules, the estimation of fish toxicity for perchlorobenzene within the set of chlorobenzenes and a typical quantum QSAR study on the popular Cramer steroid set. 相似文献
69.
Zhipeng Lin Hao Zhang Guofeng Liang Yanqi Jin Hongbin Zeng Jiawang Li Jian Chen Weihong Zhang Fangyan Xie Yanshuo Jin Hui Meng 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(12):3112-3118
A composite of FeOOH nanocubes anchored on carbon ribbons has been synthesized and used as a cathode material for Li/O2 batteries. Fe2+ ion-exchanged resin serves as a precursor for both FeOOH nanocubes and carbon ribbons, which are formed simultaneously. The as-prepared FeOOH cubes are proposed to have a core–shell structure, with FeOOH as the shell and Prussian blue as the core, based on information from XPS, TEM, and EDS mapping. As a cathode material for Li/O2 batteries, FeOOH delivers a specific capacity of 14816 mA h g−1cathode with a cycling stability of 67 cycles over 400 h. The high performance is related to the low overpotential of the oxygen reduction/evolution reaction on FeOOH. The cube structure, the supporting carbon ribbons, and the -OOH moieties all contribute to the low overpotential. The discharge product Li2O2 can be efficiently decomposed in the FeOOH cathode after a charging process, leading to higher cycling stability. Its high activity and stability make FeOOH a good candidate for use in non-aqueous Li/O2 batteries. 相似文献
70.
A low-operating voltage and high performance polymeric field effect transistors using octadecylphosphonic acid-treated high-k AlOx and HfO2 hybrid dielectrics were demonstrated. High-k metal oxide hybrid dielectrics were prepared by oxygen plasma treatment of deposited Al film for AlOx and by spin coating of solution-processable HfO2 sol-gel solution for HfO2 in combination with phosphoric acid-based self-assembled monolayer (SAM), resulting in high capacitance (10 nF/cm2 for SiO2, 600 nF/cm2 for AlOx and 580 nF/cm2 for HfO2). With phosphoric acid-based SAM on high-k metal oxide and thermal annealing of thieno[3,2-b]thiophene-based conducting polymer, the device performance was significantly enhanced. The highest mobility of the transistors using ODPA-treated AlOx as a gate dielectric is 2.3 × 10?2 cm2 V?1 s?1 in the saturation region with the source-drain of ?2 V. In ODPA-treated HfO2 hybrid dielectric, the saturated mobility is 1.1 × 10?2 cm2 V?1 s?1 and the threshold voltage was measured to be ?0.31 V, which is at least one order lower than SiO2 hybrid dielectric (?3 V). 相似文献