全文获取类型
收费全文 | 243526篇 |
免费 | 4359篇 |
国内免费 | 1771篇 |
专业分类
化学 | 133138篇 |
晶体学 | 4107篇 |
力学 | 10772篇 |
综合类 | 124篇 |
数学 | 23052篇 |
物理学 | 78463篇 |
出版年
2018年 | 2032篇 |
2017年 | 1883篇 |
2016年 | 3421篇 |
2015年 | 2675篇 |
2014年 | 3680篇 |
2013年 | 10431篇 |
2012年 | 7583篇 |
2011年 | 9396篇 |
2010年 | 6381篇 |
2009年 | 6255篇 |
2008年 | 8281篇 |
2007年 | 8274篇 |
2006年 | 7814篇 |
2005年 | 7148篇 |
2004年 | 6490篇 |
2003年 | 5820篇 |
2002年 | 5661篇 |
2001年 | 7894篇 |
2000年 | 5877篇 |
1999年 | 4635篇 |
1998年 | 3581篇 |
1997年 | 3573篇 |
1996年 | 3374篇 |
1995年 | 3114篇 |
1994年 | 2946篇 |
1993年 | 2789篇 |
1992年 | 3459篇 |
1991年 | 3365篇 |
1990年 | 3219篇 |
1989年 | 3165篇 |
1988年 | 3092篇 |
1987年 | 3135篇 |
1986年 | 2883篇 |
1985年 | 3927篇 |
1984年 | 3914篇 |
1983年 | 3153篇 |
1982年 | 3336篇 |
1981年 | 3285篇 |
1980年 | 3148篇 |
1979年 | 3391篇 |
1978年 | 3669篇 |
1977年 | 3456篇 |
1976年 | 3368篇 |
1975年 | 3145篇 |
1974年 | 3123篇 |
1973年 | 3080篇 |
1972年 | 1957篇 |
1968年 | 2049篇 |
1967年 | 2247篇 |
1966年 | 1991篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
42.
43.
44.
45.
46.
47.
S. Q. Hou W. Wang Z. Y. Wang Z. W. Hu K. Liu 《Journal of Applied Mechanics and Technical Physics》2018,59(1):153-162
In order to investigate the characteristics of force chains in a granular flow system, a parallel plate shear cell is constructed to simulate the shear movement of an infinite parallel plate and observe variations in relevant parameters. The shear dilatancy process is divided into three stages, namely, plastic strain, macroscopic failure, and granular recombination. The stickslip phenomenon is highly connected with the evolution of force chains during the shear dilatancy process. The load–distribution rate curves and patterns of the force chains are utilized to describe the load-carrying behaviors and morphologic changes of force chains separately. Force chains, namely, “diagonal gridding,” “tadpole-shaped,” and “pinnate” are defined according to the form of the force chains in the corresponding three stages. 相似文献
48.
49.
Youchao Wang Na Tian Weize Sun Boerhan Rena Xusheng Guo Yang Feng Chao Li Xuesong Wang Qianxiong Zhou 《Particle & Particle Systems Characterization》2020,37(5):2000045
Photoactivated chemotherapy (PACT) has appealing merits over traditional chemotherapy as well as photodynamic therapy (PDT) by virtue of its spatial and temporal control on drug activity and oxygen-independent mechanisms of action. However, the short photoactivation wavelengths, e.g., visible light–activated Ru(II)-based PACT agents, limit the clinical application severely. In this work, a facile construction of supramolecular nanoparticles from a poly(ethylene glycol) (PEG)-modified [Ru(dip)2(py-SO3)]+ (abbreviated as Ru-PEG, dip = 4,7-diphenyl-1,10-phenanthroline, py-SO3 = pyridine-2-sulfonate) and 1,3-phenylenebis(pyren-1-ylmethanone) (BP) is shown. While Ru-PEG may undergo photoinduced ligand dissociation and release anticancer species of [Ru(dip)2(H2O)2]2+, BP has extremely large two-photon absorption cross sections (δ2) in the NIR region and intense fluorescence over the wavelengths where Ru-PEG has strong absorption. Thus, two-photon excitation of BP followed by an efficient Förster resonance energy transfer (FRET) from BP to Ru-PEG may lead to a potent inactivation against cisplatin-resistant cancer cells and 3D multicellular tumor spheroids (MCTSs). The residue fluorescence of BP also allows the cellular uptake of the particles to be visualized. This work provides a universal and convenient strategy to realize theranostic PACT in the ideal phototherapeutic window of 650–900 nm. 相似文献
50.
The Ramanujan Journal - Inspired by Andrews and Merca’s recent work on the number of even parts over all partitions into distinct parts, we introduce a new kind of Beck type identities, which... 相似文献