全文获取类型
收费全文 | 8664篇 |
免费 | 1524篇 |
国内免费 | 995篇 |
专业分类
化学 | 6448篇 |
晶体学 | 77篇 |
力学 | 504篇 |
综合类 | 49篇 |
数学 | 1064篇 |
物理学 | 3041篇 |
出版年
2024年 | 16篇 |
2023年 | 205篇 |
2022年 | 305篇 |
2021年 | 328篇 |
2020年 | 464篇 |
2019年 | 401篇 |
2018年 | 355篇 |
2017年 | 284篇 |
2016年 | 418篇 |
2015年 | 428篇 |
2014年 | 530篇 |
2013年 | 635篇 |
2012年 | 778篇 |
2011年 | 845篇 |
2010年 | 558篇 |
2009年 | 503篇 |
2008年 | 487篇 |
2007年 | 461篇 |
2006年 | 471篇 |
2005年 | 365篇 |
2004年 | 277篇 |
2003年 | 230篇 |
2002年 | 281篇 |
2001年 | 164篇 |
2000年 | 175篇 |
1999年 | 185篇 |
1998年 | 134篇 |
1997年 | 130篇 |
1996年 | 142篇 |
1995年 | 111篇 |
1994年 | 99篇 |
1993年 | 65篇 |
1992年 | 67篇 |
1991年 | 59篇 |
1990年 | 49篇 |
1989年 | 43篇 |
1988年 | 38篇 |
1987年 | 18篇 |
1986年 | 25篇 |
1985年 | 21篇 |
1984年 | 13篇 |
1983年 | 3篇 |
1982年 | 1篇 |
1981年 | 6篇 |
1980年 | 1篇 |
1957年 | 3篇 |
1935年 | 1篇 |
1931年 | 1篇 |
1930年 | 3篇 |
1922年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 570 毫秒
941.
942.
The dc field rheological properties and frequency dependent dielectric properties of a set of electrorheological (ER) fluids composed of oxidized polyacrylonitrile or aluminosilicate materials dispersed in silicone oil were examined in this paper. Our experimental investigations show that there is a complicated relationship between the dielectric properties of dispersed particles and the ER effect. The dielectric loss of dispersed particles, which has not attracted much attention in previous work, was found to play a considerable role in ER response. The large dielectric loss tangent, experimentally around 0.10 at 1000 Hz, is found to be needed for a strong ER effect. A good ER solid material should first have large dielectric loss, and then the higher the dielectric constant, the stronger the ER effect. The large dielectric loss would facilitate the turning of dispersed particles, and the high dielectric constant would maintain the fibrillation structure stable and strong. Two processes, the particle turning process and the particle polarization process, are thought to be involved in ER activity. Our findings, in connection with the Wagner model, can better explain why the strongest ER effect occurs at particle conductivity of 10−7S/m; why the shear stress of some ER fluids decreases with frequency while with others the shear stress increases with frequency; and why trace water can enhance the ER effect considerably, which would help in understanding the mechanism of the ER effect. Too large a dielectric loss is thought to be unfavorable for the ER effect, and its suitable range is worth further study. The results also present a method of designing high performance ER fluids, which would significantly promote development of electrorheology and its application in industrial areas. 相似文献
943.
944.
945.
Yongge Tian 《Linear and Multilinear Algebra》2002,49(4):269-288
A matrix X is called an outer inverse for a matrix A if XAX=X. In this paper, we present some basic rank equalities for difference and sum of outer inverses of a matrix, and apply them to characterize various equalities related to outer inverses, Moore-Penrose inverses, group inverses, Drazin inverses and weighted Moore-Penrose inverses of matrices. 相似文献
946.
Jinhai Si Yougui Wang Qiguang Yang Peixian Ye Hongjian Tian Qingfu Zhou Huijun Xu 《Applied physics. B, Lasers and optics》1997,64(6):663-665
′ ,4′′,4′′′-tetrasulfonato-phthalocyanine/N-butyl-N′-methylanthraquinone-4,4′-bipyridinum dibromide assembly (ZnTsPc-V-AQ), was observed to be enhanced by ten times when the sample was optically pumped
by a 355 nm pump beam. The enhancement of the nonlinearity was found to be due predominantly to the charge transfer between
the two monomers of the supramolecule after optical excitation.
Received: 2 July 1996 相似文献
947.
Periodic and almost periodic solutions of nonlinear discrete Volterra equations with unbounded delay
The existence of periodic and almost periodic solutions of nonlinear discrete Volterra equations with unbounded delay is obtained by using stability properties of a bounded solution. 相似文献
948.
ZnO nanotubes were successfully synthesized by a simple template-free hydrothermal method. X-ray powder diffraction and transmission electron microscopy were used to characterize the as-prepared ZnO nanotubes. The average size of the nanotubes is 200-500 nm in length and 20-30 nm in diameter. In addition, a further investigation of the optimized synthetic conditions has been carried out. 相似文献
949.
950.