全文获取类型
收费全文 | 10468篇 |
免费 | 298篇 |
国内免费 | 31篇 |
专业分类
化学 | 7856篇 |
晶体学 | 29篇 |
力学 | 162篇 |
数学 | 1788篇 |
物理学 | 962篇 |
出版年
2020年 | 140篇 |
2019年 | 104篇 |
2018年 | 77篇 |
2017年 | 81篇 |
2016年 | 189篇 |
2015年 | 197篇 |
2014年 | 187篇 |
2013年 | 351篇 |
2012年 | 395篇 |
2011年 | 455篇 |
2010年 | 336篇 |
2009年 | 279篇 |
2008年 | 458篇 |
2007年 | 441篇 |
2006年 | 467篇 |
2005年 | 441篇 |
2004年 | 377篇 |
2003年 | 312篇 |
2002年 | 327篇 |
2001年 | 223篇 |
2000年 | 158篇 |
1999年 | 145篇 |
1998年 | 179篇 |
1997年 | 148篇 |
1996年 | 151篇 |
1995年 | 150篇 |
1994年 | 145篇 |
1993年 | 191篇 |
1992年 | 128篇 |
1991年 | 127篇 |
1990年 | 115篇 |
1989年 | 134篇 |
1988年 | 127篇 |
1987年 | 162篇 |
1986年 | 149篇 |
1985年 | 171篇 |
1984年 | 179篇 |
1983年 | 150篇 |
1982年 | 138篇 |
1981年 | 150篇 |
1980年 | 148篇 |
1979年 | 144篇 |
1978年 | 135篇 |
1977年 | 119篇 |
1976年 | 133篇 |
1975年 | 90篇 |
1974年 | 87篇 |
1973年 | 90篇 |
1971年 | 80篇 |
1970年 | 70篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
991.
992.
Lianxiang Yang Wolfgang Steinchen Gerhard Kupfer Peter Mäckel Frank Vössing 《Optics and Lasers in Engineering》1998,30(2):199-212
Digital shearography, also called digital speckle pattern shearing interferometry, is described as a robust measuring method due to its simple optical setup and the relative insensitivity against ambient noise. It has been applied for nondestructive testing and strain measuring. This paper explores its possibilities for vibration analysis. The measuring device performing both continuous (time-average method) and stroboscopic illuminations is described. The selection of the illumination mode is made by adjusting a controller and performed simply by a computer. The real-time observation with refreshing reference frame technique and the quantitative evaluation with the phase shift technique are presented. The results show this measuring device is well suited for both qualitative and quantitative vibration analysis. 相似文献
993.
994.
Two new 8,4′-oxynorneolignans were produced by elicitation of Echinacea purpurea cell suspension cultures with yeast elicitor. Their structures with an unusual (hydroxy)acetyl group were elucidated by spectroscopic methods including gas chromatography (GC) and electrospray ionization (ESI) mass spectrometry. 相似文献
995.
996.
Wolfgang S.M. Werner 《Surface science》2003,526(3):L159
Reflection electron energy loss spectra have been measured for a semiconductor and some metals (Si, Cu, Ag and Au). A novel procedure is presented to rigorously decompose the spectra into contributions corresponding to surface and volume excitations. The resulting distributions of energy losses in an individual surface loss are in good agreement with theory. In particular, the begrenzungs effect occurring at the boundary of a solid state plasma, i.e. the reduction of the intensity of bulk modes due to the coupling with surface modes, can be clearly observed in the retrieved energy loss distribution. 相似文献
997.
We prove the existence of entire functions which are universal under translations and bounded on certain prescribed sets.
It is also shown that the family of all these universal functions is a dense but not a Gδ-subset in the space of entire functions provided with a natural metric.
Received: 24 November 2004; revised: 12 April 2005 相似文献
998.
We study the nucleation phase of molecular beam epitaxy of (hexagonal) MnAs on (cubic) GaAs (0 0 1) using reflection high-energy electron diffraction (RHEED) azimuthal scans. The nucleation proceeds from a non-reconstructed initial stage through randomly oriented small nuclei and two orientation stages to the final single-phase epitaxial orientation. The fascinatingly complex nucleation process contains elements of both Volmer-Weber and Stranski-Krastanov growth. The measurement demonstrates the potential of high-resolution RHEED techniques to assess details of the surface structure during epitaxy. 相似文献
999.
1000.