全文获取类型
收费全文 | 108856篇 |
免费 | 4132篇 |
国内免费 | 3902篇 |
专业分类
化学 | 35517篇 |
晶体学 | 1036篇 |
力学 | 7671篇 |
综合类 | 251篇 |
数学 | 33929篇 |
物理学 | 21184篇 |
综合类 | 17302篇 |
出版年
2024年 | 89篇 |
2023年 | 316篇 |
2022年 | 624篇 |
2021年 | 752篇 |
2020年 | 675篇 |
2019年 | 701篇 |
2018年 | 11240篇 |
2017年 | 11094篇 |
2016年 | 7177篇 |
2015年 | 2032篇 |
2014年 | 1893篇 |
2013年 | 2166篇 |
2012年 | 5971篇 |
2011年 | 13238篇 |
2010年 | 8162篇 |
2009年 | 8381篇 |
2008年 | 9078篇 |
2007年 | 11278篇 |
2006年 | 2061篇 |
2005年 | 2980篇 |
2004年 | 2916篇 |
2003年 | 3272篇 |
2002年 | 2545篇 |
2001年 | 1470篇 |
2000年 | 1195篇 |
1999年 | 817篇 |
1998年 | 580篇 |
1997年 | 506篇 |
1996年 | 507篇 |
1995年 | 321篇 |
1994年 | 262篇 |
1993年 | 257篇 |
1992年 | 177篇 |
1991年 | 187篇 |
1990年 | 157篇 |
1989年 | 157篇 |
1988年 | 134篇 |
1987年 | 109篇 |
1986年 | 90篇 |
1985年 | 79篇 |
1984年 | 53篇 |
1983年 | 45篇 |
1982年 | 46篇 |
1981年 | 41篇 |
1980年 | 54篇 |
1979年 | 49篇 |
1978年 | 48篇 |
1914年 | 45篇 |
1909年 | 41篇 |
1908年 | 40篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
Yi Han Zibo Xue Dr. Guangwu Li Dr. Yanwei Gu Dr. Yong Ni Dr. Shaoqiang Dong Prof. Chunyan Chi 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(23):9111-9116
Incorporation of a non-hexagonal ring into a nanographene framework can lead to new electronic properties. During the attempted synthesis of naphthalene-bridged double [6]helicene and heptagon-containing nanographene by the Scholl reaction, an unexpected azulene-embedded nanographene and its triflyloxylated product were obtained, as confirmed by X-ray crystallographic analysis and 2D NMR spectroscopy. A 5/7/7/5 ring-fused substructure containing two formal azulene units is formed, but only one of them shows an azulene-like electronic structure. The formation of this unique structure is explained by arenium ion mediated 1,2-phenyl migration and a naphthalene to azulene rearrangement reaction according to an in-silico study. This report represents the first experimental example of the thermodynamically unfavorable naphthalene to azulene rearrangement and may lead to new azulene-based molecular materials. 相似文献
12.
13.
14.
15.
16.
17.
Polypyrrole Shell@3D‐Ni Metal Core Structured Electrodes for High‐Performance Supercapacitors 下载免费PDF全文
Gao‐Feng Chen Yu‐Zhi Su Pan‐Yong Kuang Zhao‐Qing Liu Dao‐Yi Chen Xu Wu Nan Li Prof. Shi‐Zhang Qiao 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(12):4614-4621
Three‐dimensional (3D) nanometal films serving as current collectors have attracted much interest recently owing to their promising application in high‐performance supercapacitors. In the process of the electrochemical reaction, the 3D structure can provide a short diffusion path for fast ion transport, and the highly conductive nanometal may serve as a backbone for facile electron transfer. In this work, a novel polypyrrole (PPy) shell@3D‐Ni‐core composite is developed to enhance the electrochemical performance of conventional PPy. With the introduction of a Ni metal core, the as‐prepared material exhibits a high specific capacitance (726 F g?1 at a charge/discharge rate of 1 A g?1), good rate capability (a decay of 33 % in Csp with charge/discharge rates increasing from 1 to 20 A g?1), and high cycle stability (only a small decrease of 4.2 % in Csp after 1000 cycles at a scan rate of 100 mV s?1). Furthermore, an aqueous symmetric supercapacitor device is fabricated by using the as‐prepared composite as electrodes; the device demonstrates a high energy density (≈21.2 Wh kg?1) and superior long‐term cycle ability (only 4.4 % and 18.6 % loss in Csp after 2000 and 5000 cycles, respectively). 相似文献
18.
洪勇 《吉林大学学报(理学版)》2019,57(2):191-198
利用实分析技巧和权函数方法, 讨论具有齐次核的多重级数Hilbert型不等式, 得到了其取最佳常数因子的充分必要条件, 并给出其应用. 相似文献
19.
Through molecular dynamics(MD)simulation,the dependencies of temperature,grain size and strain rate on the mechanical properties were studied.The simulation results demonstrated that the strain rate from 0.05 to 2 ns~(–1 )affected the Young’s modulus of nickel nanowires slightly,whereas the yield stress increased.The Young’s modulus decreased approximately linearly;however,the yield stress firstly increased and subsequently dropped as the temperature increased.The Young’s modulus and yield stress increased as the mean grain size increased from 2.66 to6.72 nm.Moreover,certain efforts have been made in the microstructure evolution with mechanical properties association under uniaxial tension.Certain phenomena such as the formation of twin structures,which were found in nanowires with larger grain size at higher strain rate and lower temperature,as well as the movement of grain boundaries and dislocation,were detected and discussed in detail.The results demonstrated that the plastic deformation was mainly accommodated by the motion of grain boundaries for smaller grain size.However,for larger grain size,the formations of stacking faults and twins were the main mechanisms of plastic deformation in the polycrystalline nickel nanowire. 相似文献
20.