全文获取类型
收费全文 | 455篇 |
免费 | 6篇 |
国内免费 | 1篇 |
专业分类
化学 | 327篇 |
晶体学 | 7篇 |
力学 | 5篇 |
数学 | 9篇 |
物理学 | 114篇 |
出版年
2021年 | 5篇 |
2019年 | 6篇 |
2018年 | 3篇 |
2016年 | 4篇 |
2015年 | 7篇 |
2014年 | 6篇 |
2013年 | 31篇 |
2012年 | 13篇 |
2011年 | 22篇 |
2010年 | 10篇 |
2009年 | 11篇 |
2008年 | 27篇 |
2007年 | 17篇 |
2006年 | 27篇 |
2005年 | 26篇 |
2004年 | 9篇 |
2003年 | 10篇 |
2002年 | 19篇 |
2001年 | 3篇 |
2000年 | 5篇 |
1999年 | 4篇 |
1997年 | 4篇 |
1996年 | 5篇 |
1995年 | 2篇 |
1994年 | 3篇 |
1993年 | 3篇 |
1992年 | 2篇 |
1991年 | 5篇 |
1990年 | 3篇 |
1989年 | 3篇 |
1988年 | 3篇 |
1986年 | 3篇 |
1985年 | 10篇 |
1984年 | 17篇 |
1983年 | 5篇 |
1982年 | 13篇 |
1981年 | 20篇 |
1980年 | 20篇 |
1979年 | 14篇 |
1978年 | 13篇 |
1977年 | 7篇 |
1976年 | 8篇 |
1975年 | 6篇 |
1974年 | 8篇 |
1973年 | 3篇 |
1972年 | 3篇 |
1968年 | 3篇 |
1959年 | 1篇 |
1942年 | 1篇 |
1938年 | 1篇 |
排序方式: 共有462条查询结果,搜索用时 15 毫秒
71.
We have theoretically investigated Kelvin waves of quantized vortex lines in trapped Bose-Einstein condensates. Counterrotating perturbation induces an elliptical instability to the initially straight vortex line, driven by a parametric resonance between a quadrupole mode and a pair of Kelvin modes of opposite momenta. Subsequently, Kelvin waves rapidly decay to longer wavelengths emitting sound waves in the process. We present a modified Kelvin wave dispersion relation for trapped superfluids and propose a simple method to excite Kelvin waves of specific wave number. 相似文献
72.
Hiroshi Itokawa Nobuaki Yasutake Shintaro Okamoto Ichiro Mizushima 《Applied Surface Science》2008,254(19):6135-6139
Embedded silicon carbon alloy (e-Si:C) technology for source and drain (S/D) is expected to improve nMOSFET drive current. The distribution and activation characteristics of arsenic in Si:C film and the interfacial solid-phase reaction of the Ni/Si:C system were studied with the aim of achieving the maximum improvement of the characteristics of e-Si:C S/D. It was clarified that the active carrier concentration of Si:C decreased with increasing carbon concentration compared to the control Si. There is concern that the low doping activation in Si:C increases series resistance of e-Si:C S/D nMOSFETs and degrades the performance gain expected from the strain effect. 相似文献
73.
74.
Jiro Egawa 《Proceedings of the American Mathematical Society》1998,126(1):273-278
In this paper we construct distal functions of another type discussed by Salehi (1991). Let be an almost periodic function with the mean value 0, which has unbounded integral, and a continuous periodic function with the prime period 1. If satisfies some additional condition, then is a distal function, which is not almost periodic, and the set of eigenvalues of is the module of .
75.
The PtCl2-catalyzed cyclization reaction of ortho-alkynylphenyl acetals 1 in the presence of COD (1,5-cyclooctadiene) produces 3-(α-alkoxyalkyl)benzofurans 2 in good to high yields. For example, the reaction of acetaldehyde ethyl 2-(1-octynyl)phenyl acetal (1a), acetaldehyde ethyl 2-(cyclohexylethynyl)phenyl acetal (1c), and acetaldehyde ethyl 2-(phenylethynyl)phenyl acetal (1f) in the presence of 2 mol % of platinum(II) chloride and 8 mol % of 1,5-cycloocatadiene in toluene at 30 °C gave the corresponding 2,3-disubstituted benzofurans 2a, 2c, and 2f in 91, 94, and 88% yields, respectively. Moreover, the reaction of N-methoxymethyl-2-alkynylanilines 3 was catalyzed by PdBr2, affording the corresponding 2,3-disubstituted indoles 4 in moderate yields. For example, the reaction of N-methoxymethyl-2-(1-pentynyl)-N-tosylaniline (3a) and N-methoxymethyl-2-(phenylethynyl)-N-tosylaniline (3b) in the presence of 10 mol % of PdBr2 in toluene at 80 °C gave 3-methoxymethyl-2-propyl-1-tosylindole (4a) and 3-methoxymethyl-2-phenyl-1-tosylindole (4b) in 33 and 33% yields, respectively. 相似文献
76.
Relocation of a glycosylphosphatidylinositol (GPI)-anchored protein acetylcholinesterase (AChE) in its enzymatically active form from proteovesicles containing human erythrocyte ghost membrane proteins onto a liposome-gel conjugate was examined. Liposomes of 1,2-dimyristoylphosphatidylcholine (DMPC) were immobilized on Sephacryl S-1000 gel that was chemically modified to bear hydrophobic octyl moieties. Upon coincubation of the liposome-gel conjugate with freely suspended proteovesicles prepared from erythrocyte ghosts, 50% of the AChE left the proteovesicles and immobilized onto the liposome-gel conjugate in 18 h. When the proteovesicles were immobilized and interacted with freely suspended plain liposomes, approximately 2% of the AChE appeared in the liposome fraction. The relocation of AChE apparently possesses strong preference for the liposome-gel conjugate, suggesting that the hydrophobic moieties on the gel could assist the relocation. 相似文献
77.
The enhancement effects of Y ( Ⅲ) ions on the fluorescence of Ce ( Ⅲ) in Ce ( Ⅲ)-Y ( Ⅲ)-PMMA (polymethylmethacrylate ) or Ce ( Ⅲ)-Y ( Ⅲ)-PVC (polyvinyl chloride ) complex systems were observed. The influence of Y ( Ⅲ) ions on the emission spectra of PMMA ligands in PMMA-Y ( Ⅲ) and the fluorescent enhance- ment of Y( Ⅲ) on Ce( Ⅲ) emission in PMMA-Ce-Y by Y( Ⅲ) ion were studied. It was also of interest to note that when Y ( Ⅲ) ions were added into PMMA and into bpy(bipyridine ), respectively, the emission spectrum of PMMA ligands was split into fine structure bands by Y ( Ⅲ), and the fluorescence intensities of bpy ligands in bpy-Y ( Ⅲ) complexes were considerably increased. 相似文献
78.
79.