全文获取类型
收费全文 | 169篇 |
免费 | 10篇 |
国内免费 | 1篇 |
专业分类
化学 | 138篇 |
晶体学 | 2篇 |
数学 | 23篇 |
物理学 | 17篇 |
出版年
2023年 | 1篇 |
2021年 | 3篇 |
2020年 | 1篇 |
2019年 | 6篇 |
2018年 | 1篇 |
2016年 | 6篇 |
2015年 | 3篇 |
2014年 | 5篇 |
2013年 | 5篇 |
2012年 | 7篇 |
2011年 | 8篇 |
2010年 | 1篇 |
2009年 | 4篇 |
2008年 | 9篇 |
2007年 | 11篇 |
2006年 | 13篇 |
2005年 | 12篇 |
2004年 | 13篇 |
2003年 | 12篇 |
2002年 | 8篇 |
2001年 | 2篇 |
2000年 | 2篇 |
1999年 | 5篇 |
1998年 | 2篇 |
1997年 | 8篇 |
1996年 | 3篇 |
1995年 | 5篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1981年 | 3篇 |
1978年 | 2篇 |
1977年 | 1篇 |
1975年 | 2篇 |
1969年 | 1篇 |
排序方式: 共有180条查询结果,搜索用时 15 毫秒
161.
Ryo Kobayashi Shintaro Ishida Takeaki Iwamoto 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(28):9525-9528
Despite tremendous efforts to synthesize isolable compounds with an Si=O bond, silicon analogues of ketones that contain an unperturbed Si=O bond have remained elusive for more than 100 years. Herein, we report the synthesis of an isolable silicon analogue of a ketone that exhibits a three‐coordinate silicon center and an unperturbed Si=O bond, thus representing the first example of a genuine silanone. Most importantly, this silanone does not require coordination by Lewis bases and acids and/or the introduction of electron‐donating groups to stabilize the Si=O bond. The structure and properties of this unperturbed Si=O bond were examined by a single‐crystal X‐ray diffraction analysis, NMR spectroscopy, and theoretical calculations. Bimolecular reactions revealed high electrophilicity on the Si atom and high nucleophilicity on the O atom of this genuine Si=O bond. 相似文献
162.
The first intermolecular reactions of the excited state of a silicon divalent compound (silylene) with benzene derivatives were discovered. Typically, when a benzene solution of an isolable silylene is irradiated with light of wavelengths longer than 420 nm at room temperature, the corresponding silacyclohepta-2,4,6-triene (silepin) is yielded quantitatively. The photochemical insertion of the silylene toward substituted benzenes occurs in general to give the corresponding substituted silepins. The insertion reaction is highly sensitive to the steric hindrance at a reacting C-C double bond in benzene; during the reactions of the silylene with substituted benzenes, only unsubstituted C-C double bonds in the benzene ring reacted selectively. The irradiation of the silylene in the presence of mesitylene afforded the insertion product to a benzylic C-H bond, indicative of the biradical nature of the excited-state silylene. 相似文献
163.
Iwamoto T Okita J Kabuto C Kira M 《Journal of the American Chemical Society》2002,124(39):11604-11605
The proton abstraction (sila-metalation) of trialkylsilyl-substituted dihydridosilanes with t-BuLi or LDA in THF was found to be a convenient route to the corresponding silyllithiums (RR'SiHLi; 1a, R, R' = t-BuMe(2)Si; 1b, R, R' = Me(3)Si; 1c, R, R' = i-Pr(2)MeSi; 1d, R = t-BuMe(2)Si, R' = 4-methylphenyl). Hydridosilylithium 1a was isolated as air- and moisture-sensitive, but thermally stable, colorless crystals. X-ray analysis has shown that 1a is dimeric in the solid state, where two lithium atoms bridge between anionic silicon atoms forming a parallelogram, each lithium atom is coordinated by one THF molecule, and the Si-H hydrogen atoms are in the plane of the parallelogram. X-ray analysis has shown that (t-BuMe(2)Si)(2)GeHLi (5) has a dimeric structure similar to that of 1a. 相似文献
164.
Muneo?ChōEmail author Tadasi?Huruya Takeaki?Yamazaki 《Integral Equations and Operator Theory》2004,48(3):295-304
The purpose of this paper is to introduce mosaic and principal
functions of log-hyponormal operators associated with Aluthge transformation
and discuss determining sets. 相似文献
165.
Akiyoshi Shioura Takeaki Uno 《Journal of Algorithms in Cognition, Informatics and Logic》1997,23(2):281-290
Given a tree containingnvertices, consider the sum of the distance between all vertices and ak-leaf subtree (subtree which contains exactlykleaves). Ak-tree core is ak-leaf subtree which minimizes the sum of the distances. In this paper, we propose a linear time algorithm for finding ak-tree core for a givenk. 相似文献
166.
A glassy state of matter results if crystallization is avoided upon cooling or increasing density. However, the physical factors controlling the ease of vitrification and nature of the glass transition remain elusive. Using numerical simulations of polydisperse hard disks, we find a direct relation between medium-range crystalline ordering and the slow dynamics which characterizes the glass transition. This suggests an intriguing scenario that the strength of frustration controls both the ease of vitrification and nature of the glass transition. Vitrification may be a process of hidden crystalline ordering under frustration, at least in our system. 相似文献
167.
Nakakoshi M Ueda M Sakurai S Asakura K Utsumi H Miyata O Naito T Takahashi Y 《Magnetic resonance in chemistry : MRC》2007,45(11):989-992
Direct observation of the unstable intermediate in the radical addition reaction of the oxime ether 1 mediated by triethylborane (Et(3)B) is described using (1)H and (11)B micro channeled cell for synthesis monitoring (MICCS), which was recently developed as an interfacing microchip for NMR. It was possible that the signal of the intermediate was observed as a result of using MICCS technique with a standard NMR instrument. This result supports the structure of the intermediate analyzed by diffusion-ordered spectroscopy (DOSY) NMR method in a previous paper. The procedure of micro channeled cell for synthesis monitoring-nuclear magnetic resonance (MICCS-NMR) was much easier than that of DOSY method. It was proven that it could be applied to the reaction in an anhydrous condition. 相似文献
168.
169.
Yutaka Moritomo Kouhei Yonezawa Takeaki Sakurai Takeshi Yasuda Yasuo Takeichi Hayato Kamioka 《Molecular Crystals and Liquid Crystals》2015,620(1):32-37
Clarification of the morphology of bulk heterojunction (BHJ) is indispensable for true comprehension of the organic solar cells. Here, we performed scanning transmission X-ray microscopy (STXM) for a poly-(9,9-dioctylfluorene-co-bithiophene) (F8T2)/[6,6]-phenyl C71-butyric acid methyl ester (PC71BM) blend film annealed at various temperatures (Tan). We found that the fullerene concentration within the polymer-rich domain decreases with Tan while the domain size (~230 nm) is essentially unchanged. We will discuss the interrelation between the film morphology and the photovoltaic performance. 相似文献
170.