全文获取类型
收费全文 | 8027篇 |
免费 | 423篇 |
国内免费 | 37篇 |
专业分类
化学 | 5646篇 |
晶体学 | 20篇 |
力学 | 203篇 |
数学 | 1398篇 |
物理学 | 1220篇 |
出版年
2023年 | 76篇 |
2022年 | 72篇 |
2021年 | 135篇 |
2020年 | 189篇 |
2019年 | 190篇 |
2018年 | 115篇 |
2017年 | 115篇 |
2016年 | 357篇 |
2015年 | 314篇 |
2014年 | 296篇 |
2013年 | 472篇 |
2012年 | 554篇 |
2011年 | 652篇 |
2010年 | 378篇 |
2009年 | 321篇 |
2008年 | 515篇 |
2007年 | 462篇 |
2006年 | 439篇 |
2005年 | 410篇 |
2004年 | 347篇 |
2003年 | 315篇 |
2002年 | 288篇 |
2001年 | 169篇 |
2000年 | 122篇 |
1999年 | 120篇 |
1998年 | 93篇 |
1997年 | 102篇 |
1996年 | 103篇 |
1995年 | 85篇 |
1994年 | 59篇 |
1993年 | 62篇 |
1992年 | 53篇 |
1991年 | 35篇 |
1990年 | 36篇 |
1989年 | 29篇 |
1988年 | 34篇 |
1987年 | 26篇 |
1986年 | 31篇 |
1985年 | 24篇 |
1984年 | 22篇 |
1983年 | 14篇 |
1982年 | 22篇 |
1981年 | 16篇 |
1980年 | 18篇 |
1979年 | 10篇 |
1978年 | 21篇 |
1977年 | 13篇 |
1975年 | 11篇 |
1974年 | 13篇 |
1970年 | 8篇 |
排序方式: 共有8487条查询结果,搜索用时 31 毫秒
941.
942.
Petra Lommens Celso de Mello Donega Luc Piraux Stefan Mátéfi-Tempfli Zeger Hens 《Journal of luminescence》2006,118(2):245-250
We performed photoluminescence experiments on colloidal, Co2+-doped ZnO nanocrystals in order to study the electronic properties of Co2+ in a ZnO host. Room temperature measurements showed, next to the ZnO exciton and trap emission, an additional emission related to the Co2+ dopant. The spectral position and width of this emission does not depend on particle size or Co2+ concentration. At 8 K, a series of ZnO bulk phonon replicas appear on the Co2+-emission band. We conclude that Co2+ ions are strongly localized in the ZnO host, making the formation of a Co2+d-band unlikely. Magnetic measurements revealed a paramagnetic behaviour. 相似文献
943.
An overview over the binding situation in transition metal and lanthanide aminopyridinato complexes is given. True aminopyridinato complexes in which we observe a significant longer N‐amido than N‐pyridine bond length are rare and for instance observed for ruthenium. Additional examples of ruthenium aminopyridinato complexes were synthesized and characterized by X‐ray crystal structure analysis. 相似文献
944.
945.
946.
947.
948.
949.
Polydisperse suspensions consist of particles differing in size or density that are dispersed in a viscous fluid. During sedimentation, the different particle species segregate and create areas of different composition. Spatially one-dimensional mathematical models of this process can be expressed as strongly coupled, nonlinear systems of first-order conservation laws. The solution of this system is the vector of volume fractions of each species as a function of depth and time, which will in general be discontinuous. It is well known that this system is strictly hyperbolic provided that the Masliyah–Lockett–Bassoon (MLB) flux vector is chosen, the particles have the same density, and the hindered-settling factor (a multiplicative algebraic expression appearing in the flux vector) does not depend on the particle size but is the same for all species. It is the purpose of this paper to prove that this hyperbolicity result remains valid in a fairly general class of cases where the hindered-settling factor does depend on particle size. This includes the common power-law type hindered-settling factor in which the exponent, sometimes called Richardson–Zaki exponent, is determined individually for each species, and is a decreasing function of particle size. The importance of this paper is two-fold: it proves stability for a class of polydisperse suspensions that was not covered in previous work, and it offers a new analysis of real data. 相似文献