全文获取类型
收费全文 | 638篇 |
免费 | 17篇 |
国内免费 | 1篇 |
专业分类
化学 | 520篇 |
晶体学 | 6篇 |
力学 | 7篇 |
数学 | 25篇 |
物理学 | 98篇 |
出版年
2023年 | 3篇 |
2022年 | 3篇 |
2021年 | 9篇 |
2020年 | 11篇 |
2019年 | 9篇 |
2018年 | 8篇 |
2017年 | 9篇 |
2016年 | 15篇 |
2015年 | 9篇 |
2014年 | 16篇 |
2013年 | 36篇 |
2012年 | 39篇 |
2011年 | 39篇 |
2010年 | 23篇 |
2009年 | 26篇 |
2008年 | 42篇 |
2007年 | 45篇 |
2006年 | 34篇 |
2005年 | 32篇 |
2004年 | 41篇 |
2003年 | 29篇 |
2002年 | 18篇 |
2000年 | 10篇 |
1999年 | 8篇 |
1998年 | 12篇 |
1997年 | 4篇 |
1996年 | 6篇 |
1995年 | 8篇 |
1994年 | 15篇 |
1993年 | 5篇 |
1992年 | 10篇 |
1991年 | 4篇 |
1990年 | 4篇 |
1989年 | 4篇 |
1986年 | 6篇 |
1985年 | 8篇 |
1984年 | 5篇 |
1983年 | 3篇 |
1982年 | 5篇 |
1981年 | 5篇 |
1980年 | 3篇 |
1979年 | 3篇 |
1973年 | 4篇 |
1972年 | 3篇 |
1971年 | 2篇 |
1970年 | 2篇 |
1969年 | 2篇 |
1968年 | 2篇 |
1964年 | 3篇 |
1909年 | 2篇 |
排序方式: 共有656条查询结果,搜索用时 883 毫秒
651.
Nghia Tuan Duong Yoshitaka Aoyama Katsumi Kawamoto Toshio Yamazaki Yusuke Nishiyama 《Molecules (Basel, Switzerland)》2021,26(15)
Three-dimensional electron diffraction crystallography (microED) can solve structures of sub-micrometer crystals, which are too small for single crystal X-ray crystallography. However, R factors for the microED-based structures are generally high because of dynamic scattering. That means R factor may not be reliable provided that kinetic analysis is used. Consequently, there remains ambiguity to locate hydrogens and to assign nuclei with close atomic numbers, like carbon, nitrogen, and oxygen. Herein, we employed microED and ssNMR dipolar-based experiments together with spin dynamics numerical simulations. The NMR dipolar-based experiments were 1H-14N phase-modulated rotational-echo saturation-pulse double-resonance (PM-S-RESPDOR) and 1H-1H selective recoupling of proton (SERP) experiments. The former examined the dephasing effect of a specific 1H resonance under multiple 1H-14N dipolar couplings. The latter examined the selective polarization transfer between a 1H-1H pair. The structure was solved by microED and then validated by evaluating the agreement between experimental and calculated dipolar-based NMR results. As the measurements were performed on 1H and 14N, the method can be employed for natural abundance samples. Furthermore, the whole validation procedure was conducted at 293 K unlike widely used chemical shift calculation at 0 K using the GIPAW method. This combined method was demonstrated on monoclinic l-histidine. 相似文献
652.
653.
654.
Ken-ichi Ito Yoshitaka Shigeru Masahiro Tsunooka 《Macromolecular rapid communications》1996,17(4):203-207
Films of polymers bearing pendant acyloxyimino (AOI) groups become insoluble when irradiated by ultraviolet light in the presence of p-benzoquinone. Post-heating of these films after irradiation also induces further the insolubilization. In the photocrosslinking, it is deduced that p-benzoquinone serves not only as sensitizer for the decomposition of AOI groups but also as crosslinker during the photo-irradiation and heating after irradiation. 相似文献
655.
656.
Jun'ichi Uenishi Mitsuhiro Motoyama Yoshitaka Nishiyama Yuichi Hirota Yuki Kubo Haruo Akashi 《Heteroatom Chemistry》1994,5(1):51-60
Stereospecific ring openings of optically active 2,3-epoxy alcohols were performed by the reaction of 1 , 3 , 5 , and 7 with carbon disulfide and sodium hydride to give the five-membered xanthates 2 , 4 , 6 , and 8 . Both enantiomers of 2-mercapto-1,3-diol triacetates, 11 and 14 , were derived from 4 and 6 , respectively. The ring opening reaction proceeded at −78°C to −30°C, and the yields were around 80%. However, at a higher temperature between 0°C to room temperature, a complicated reaction took place and led to the formation of two isomers of the cyclic thiol carbonates 15 and 16 from 1 or 5 . These processes were also stereospecific, and mechanisms have been proposed. In the case of the 3,4-epoxy alcohol 20 , the epoxide ring opening gave the six-membered xanthate 21 stereospecifically. 相似文献