全文获取类型
收费全文 | 413篇 |
免费 | 9篇 |
专业分类
化学 | 266篇 |
晶体学 | 8篇 |
力学 | 2篇 |
数学 | 17篇 |
物理学 | 129篇 |
出版年
2021年 | 3篇 |
2020年 | 3篇 |
2019年 | 3篇 |
2017年 | 3篇 |
2016年 | 5篇 |
2015年 | 6篇 |
2014年 | 3篇 |
2013年 | 12篇 |
2012年 | 21篇 |
2011年 | 19篇 |
2010年 | 15篇 |
2009年 | 11篇 |
2008年 | 18篇 |
2007年 | 16篇 |
2006年 | 25篇 |
2005年 | 12篇 |
2004年 | 16篇 |
2003年 | 7篇 |
2002年 | 14篇 |
2001年 | 7篇 |
2000年 | 6篇 |
1999年 | 12篇 |
1998年 | 9篇 |
1997年 | 6篇 |
1995年 | 6篇 |
1994年 | 4篇 |
1989年 | 3篇 |
1988年 | 8篇 |
1987年 | 3篇 |
1986年 | 3篇 |
1985年 | 16篇 |
1984年 | 5篇 |
1982年 | 8篇 |
1981年 | 5篇 |
1979年 | 3篇 |
1977年 | 6篇 |
1976年 | 5篇 |
1973年 | 5篇 |
1972年 | 4篇 |
1970年 | 8篇 |
1969年 | 3篇 |
1967年 | 6篇 |
1962年 | 4篇 |
1960年 | 5篇 |
1958年 | 3篇 |
1948年 | 2篇 |
1940年 | 2篇 |
1929年 | 2篇 |
1905年 | 2篇 |
1871年 | 2篇 |
排序方式: 共有422条查询结果,搜索用时 62 毫秒
331.
332.
Polymorphism of Bis(dineopentoxyphosphorothioyl)diselenide – Correlation of X‐Ray Structure and MAS NMR Data The crystal structures of two polymorphs of the title compound were determined by single‐crystal X‐ray methods and refined both at room temperature and 250 K. A triclinic and a monoclinic phase were discovered and studied. Both modifications are centrosymmetrical layer structures. The numerically clearly significant differences were observed in unit cell volumes as well as in alternating disproportions of distances of atoms being chemically and crystallographically equivalent as a result of discontinuously distributed conformational changes along the single bonds. Phase transitions were not observed by cooling up to 240 K. Lowering temperatures single crystals of both phases decompose because of the considerable anisotropy of intermolecular interaction. The small differences of molecular structure produce slightly splitted 31P CP MAS NMR signals. A comparison of the chemical shifts from 13C CP MAS NMR spectra and from quantum‐chemical calculations leads to the conclusion that the inner rotation around CH2–Cq bonds is not frozen in the solid state. 相似文献
333.
This paper shows the feasibility of using digital speckle pattern interferometry (DSPI) as a fluid velocimetry technique
in high speed gaseous flows. The light scattered from an illuminated plane was recorded with a CCD camera at the same time
as a uniform reference beam. A fibre optic was used to bring this reference beam from the laser cavity to the CCD camera.
The comparison of two subsequent frames gives information about the velocity field. DSPI was applied to a Von Karman street
flow set up in a wind tunnel. Particle image velocimetry (PIV) measurements were also obtained for comparison with the information
provided by DSPI. A system for increasing the measurement region when using short coherence length lasers is proposed.
Received: 15 June 2000/Accepted: 8 September 2000 相似文献
334.
335.
Dr. Oleksandr Stroyuk Dr. Oleksandra Raievska Prof. Dr. Dietrich R. T. Zahn Prof. Dr. Christoph J. Brabec 《Chemical record (New York, N.Y.)》2024,24(2):e202300241
The review summarizes our recent reports on brightly-emitting materials with varied dimensionality (3D, 2D, 0D) synthesized using “green” chemistry and exhibiting highly efficient photoluminescence (PL) originating from self-trapped exciton (STE) states. The discussion starts with 0D emitters, in particular, ternary indium-based colloidal quantum dots, continues with 2D materials, focusing on single-layer polyheptazine carbon nitride, and further evolves to 3D luminophores, the latter exemplified by lead-free double halide perovskites. The review shows the broadband STE PL to be an inherent feature of many materials produced in mild conditions by “green” chemistry, outlining PL features general for these STE emitters and differences in their photophysical properties. The review is concluded with an outlook on the challenges in the field of STE PL emission and the most promising venues for future research. 相似文献
336.
337.
338.
339.
340.