全文获取类型
收费全文 | 37367篇 |
免费 | 5901篇 |
国内免费 | 3869篇 |
专业分类
化学 | 26549篇 |
晶体学 | 468篇 |
力学 | 2201篇 |
综合类 | 306篇 |
数学 | 4397篇 |
物理学 | 13216篇 |
出版年
2024年 | 67篇 |
2023年 | 773篇 |
2022年 | 903篇 |
2021年 | 1229篇 |
2020年 | 1597篇 |
2019年 | 1423篇 |
2018年 | 1208篇 |
2017年 | 1112篇 |
2016年 | 1729篇 |
2015年 | 1644篇 |
2014年 | 1931篇 |
2013年 | 2643篇 |
2012年 | 3241篇 |
2011年 | 3283篇 |
2010年 | 2215篇 |
2009年 | 2165篇 |
2008年 | 2456篇 |
2007年 | 2198篇 |
2006年 | 2054篇 |
2005年 | 1768篇 |
2004年 | 1363篇 |
2003年 | 1126篇 |
2002年 | 1025篇 |
2001年 | 837篇 |
2000年 | 796篇 |
1999年 | 876篇 |
1998年 | 677篇 |
1997年 | 579篇 |
1996年 | 627篇 |
1995年 | 547篇 |
1994年 | 493篇 |
1993年 | 447篇 |
1992年 | 368篇 |
1991年 | 313篇 |
1990年 | 324篇 |
1989年 | 223篇 |
1988年 | 181篇 |
1987年 | 132篇 |
1986年 | 135篇 |
1985年 | 107篇 |
1984年 | 73篇 |
1983年 | 56篇 |
1982年 | 51篇 |
1981年 | 39篇 |
1980年 | 19篇 |
1979年 | 12篇 |
1976年 | 11篇 |
1975年 | 11篇 |
1971年 | 7篇 |
1957年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 328 毫秒
11.
Bingjie Chen Dr. Lianhai Zu Dr. Yao Liu Dr. Ruijing Meng Yutong Feng Prof. Chengxin Peng Feng Zhu Tianzi Hao Jiajia Ru Prof. Yonggang Wang Prof. Jinhu Yang 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(8):3161-3166
Incorporating nanoscale Si into a carbon matrix with high dispersity is desirable for the preparation of lithium-ion batteries (LIBs) but remains challenging. A space-confined catalytic strategy is proposed for direct superassembly of Si nanodots within a carbon (Si NDs⊂C) framework by copyrolysis of triphenyltin hydride (TPT) and diphenylsilane (DPS), where Sn atomic clusters created from TPT pyrolysis serve as the catalyst for DPS pyrolysis and Si catalytic growth. The use of Sn atomic cluster catalysts alters the reaction pathway to avoid SiC generation and enable formation of Si NDs with reduced dimensions. A typical Si NDs⊂C framework demonstrates a remarkable comprehensive performance comparable to other Si-based high-performance half LIBs, and higher energy densities compared to commercial full LIBs, as a consequence of the high dispersity of Si NDs with low lithiation stress. Supported by mechanic simulations, this study paves the way for construction of Si/C composites suitable for applications in future energy technologies. 相似文献
12.
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
13.
Journal of Thermal Analysis and Calorimetry - In the present work, pyrolysis kinetic mechanism was studied for regenerated cellulosic fiber (RCF) and composite RCF containing silicon/nitrogen flame... 相似文献
14.
Nonlinear Dynamics - Under investigation is a generalized (3 + 1)-dimensional variable- coefficient Kadomtsev– Petviashvili equation in fluid mechanics. Various exact analytical solutions are... 相似文献
15.
16.
17.
18.
19.
Jing Yu Jingwei Han Chuanzhong Li 《Mathematical Methods in the Applied Sciences》2020,43(6):3076-3085
For the orthosymplectic Lie superalgebra , we choose a set of basis matrices. A linear combination of those basis matrices presents a spatial spectral matrix. The compatible condition of the spatial part and the corresponding temporal parts of the spectral problem leads to a generalized super AKNS (GSAKNS) hierarchy. By making use of the supertrace identity, the obtained GSAKNS hierarchy can be written as the super bi-Hamiltonian structures. 相似文献
20.
Simultaneous quantitative determination of 20 active components in the traditional Chinese medicine formula Zhi‐Zi‐Da‐Huang decoction by liquid chromatography coupled with mass spectrometry: application to study the chemical composition variations in different combinations 下载免费PDF全文
Zheng Tang Ran Yin Kaishun Bi Heyun Zhu Fei Han Kelin Chen Fenrong Wang 《Biomedical chromatography : BMC》2015,29(9):1406-1414