全文获取类型
收费全文 | 11876篇 |
免费 | 1307篇 |
国内免费 | 959篇 |
专业分类
化学 | 1314篇 |
晶体学 | 22篇 |
力学 | 1374篇 |
综合类 | 251篇 |
数学 | 7778篇 |
物理学 | 3403篇 |
出版年
2024年 | 24篇 |
2023年 | 115篇 |
2022年 | 220篇 |
2021年 | 263篇 |
2020年 | 359篇 |
2019年 | 322篇 |
2018年 | 294篇 |
2017年 | 366篇 |
2016年 | 376篇 |
2015年 | 280篇 |
2014年 | 461篇 |
2013年 | 862篇 |
2012年 | 540篇 |
2011年 | 633篇 |
2010年 | 536篇 |
2009年 | 761篇 |
2008年 | 769篇 |
2007年 | 762篇 |
2006年 | 696篇 |
2005年 | 599篇 |
2004年 | 501篇 |
2003年 | 524篇 |
2002年 | 486篇 |
2001年 | 422篇 |
2000年 | 440篇 |
1999年 | 356篇 |
1998年 | 369篇 |
1997年 | 270篇 |
1996年 | 224篇 |
1995年 | 134篇 |
1994年 | 147篇 |
1993年 | 111篇 |
1992年 | 115篇 |
1991年 | 108篇 |
1990年 | 79篇 |
1989年 | 70篇 |
1988年 | 72篇 |
1987年 | 59篇 |
1986年 | 45篇 |
1985年 | 52篇 |
1984年 | 71篇 |
1983年 | 31篇 |
1982年 | 33篇 |
1981年 | 42篇 |
1980年 | 25篇 |
1979年 | 24篇 |
1978年 | 26篇 |
1977年 | 16篇 |
1976年 | 12篇 |
1973年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
《Mendeleev Communications》2022,32(4):534-536
Correlation times and diffusion coefficients of water molecules were measured for the first time by 1H spin relaxation and pulsed field gradient NMR in Li+, Na+ and Cs+ ionic forms of Nafion 117 membrane. Hydration numbers of Li+, Na+ and Cs+ cations were calculated. It was shown that at high humidity macroscopic transfer is controlled by the local translational motion of water molecules. 相似文献
2.
3.
4.
G. Peruginelli 《代数通讯》2018,46(11):4724-4738
We classify the maximal subrings of the ring of n×n matrices over a finite field, and show that these subrings may be divided into three types. We also describe all of the maximal subrings of a finite semisimple ring, and categorize them into two classes. As an application of these results, we calculate the covering number of a finite semisimple ring. 相似文献
5.
A (di)graph is supereulerian if it contains a spanning eulerian sub(di)graph. This property is a relaxation of hamiltonicity. Inspired by this analogy with hamiltonian cycles and by similar results in supereulerian graph theory, we analyze a number of sufficient Ore type conditions for a digraph to be supereulerian. Furthermore, we study the following conjecture due to Thomassé and the first author: if the arc‐connectivity of a digraph is not smaller than its independence number, then the digraph is supereulerian. As a support for this conjecture we prove it for digraphs that are semicomplete multipartite or quasitransitive and verify the analogous statement for undirected graphs. 相似文献
6.
7.
9.
10.
Renny Mathew Karolina A. Uchman Lydia Gkoura Chris J. Pickard Maria Baias 《Magnetic resonance in chemistry : MRC》2020,58(11):1018-1025
A combined experimental and computational approach was used to distinguish between different polymorphs of the pharmaceutical drug aspirin. This method involves the use of ab initio random structure searching (AIRSS), a density functional theory (DFT)-based crystal structure prediction method for the high-accuracy prediction of polymorphic structures, with DFT calculations of nuclear magnetic resonance (NMR) parameters and solid-state NMR experiments at natural abundance. AIRSS was used to predict the crystal structures of form-I and form-II of aspirin. The root-mean-square deviation between experimental and calculated 1H chemical shifts was used to identify form-I as the polymorph present in the experimental sample, the selection being successful despite the large similarities between the molecular environments in the crystals of the two polymorphs. 相似文献