全文获取类型
收费全文 | 315篇 |
免费 | 13篇 |
专业分类
化学 | 228篇 |
晶体学 | 1篇 |
力学 | 6篇 |
数学 | 45篇 |
物理学 | 48篇 |
出版年
2023年 | 2篇 |
2022年 | 3篇 |
2021年 | 7篇 |
2020年 | 4篇 |
2019年 | 9篇 |
2018年 | 6篇 |
2017年 | 6篇 |
2016年 | 7篇 |
2015年 | 7篇 |
2014年 | 8篇 |
2013年 | 20篇 |
2012年 | 22篇 |
2011年 | 18篇 |
2010年 | 12篇 |
2009年 | 5篇 |
2008年 | 15篇 |
2007年 | 23篇 |
2006年 | 23篇 |
2005年 | 15篇 |
2004年 | 15篇 |
2003年 | 15篇 |
2002年 | 15篇 |
1999年 | 3篇 |
1997年 | 2篇 |
1996年 | 3篇 |
1995年 | 4篇 |
1994年 | 4篇 |
1989年 | 4篇 |
1986年 | 2篇 |
1985年 | 2篇 |
1984年 | 4篇 |
1983年 | 3篇 |
1982年 | 2篇 |
1981年 | 3篇 |
1979年 | 4篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1975年 | 3篇 |
1974年 | 1篇 |
1973年 | 2篇 |
1972年 | 2篇 |
1968年 | 2篇 |
1967年 | 2篇 |
1966年 | 1篇 |
1963年 | 1篇 |
1962年 | 2篇 |
1960年 | 1篇 |
1958年 | 1篇 |
1956年 | 1篇 |
1939年 | 1篇 |
排序方式: 共有328条查询结果,搜索用时 15 毫秒
321.
Marushchak D Kalinin S Mikhalyov I Gretskaya N -A Johansson LB 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2006,65(1):113-122
Homo and hetero dimerisation of two spectroscopically different BODIPY chromophores was studied, namely, 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene and its 5-styryl-derivative. These exhibit very similar absorption and fluorescence spectral shape, but are mutually shifted by ca. 70 nm. For this reason the former and the latter are referred to as the green and red BODIPY, which here are denoted gB and rB, respectively. Various spectroscopic properties of the rB in different common solvents were determined. The calculated and experimental fluorescence quantum yield is found to be close to 100%, the fluorescence relaxation has a single exponential decay with a lifetime of about 4.5 ns, and the F?rster radius for donor-donor energy migration is 67+/-1A. The dimerisation in different solvents was examined by using custom synthesised; mono and bis BODIPY-labelled forms of 1,2-cis-diaminocyclohexane. It is shown that gB and rB can form ground state homo- as well as hetero dimers. The dimers are non-fluorescent, compatible with H-dimers and may act as excitation traps or as acceptors to the corresponding excited monomers. 相似文献
322.
C Kamper K Korpis E Specker L Anger M Neuenschwander PJ Bednarski A Link 《Molecular diversity》2012,16(3):541-551
A sub-library of 88 information-rich lead-like purine derivatives were prepared and deposited in an open access academic screening facility. The rationale for the synthesis of these rigid low complexity structures was the privileged character of the purine heterocycle associated with its inherent probability of interactions with multiple adenine-related targets. Although generally expected to be weak binders in many assays, such fragment-like compounds are estimated to match diverse binding sites. It is suggested that heterocycles with many anchor points for hydrogen bonds can be anticipated to undergo very specific interactions to produce more negative enthalpies and thus provide superior starting points for lead optimization than compounds that owe their activity to entropic effects. The in vitro cytotoxicity of the small compounds on a panel of human cancer cell lines has been investigated and some of them showed marked unselective or selective toxicity. This data may be useful if these fragments are to be incorporated into drug-like structures via metabolically cleavable connections. The sub-library will be implemented as part of the ChemBioNet ( www.chembionet.info ) library, and it is open to screening campaigns of academic research groups striving for a fragment-based approach in their biological assays. 相似文献
323.
324.
325.
Dr. Markus Staudt Prof. Theis Sølling Prof. Lennart Bunch 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(42):10941-10947
Disrotatory – thermally allowed – 2π-electrocyclic ring-opening reactions require high temperatures to proceed. Herein, we report the first anion-accelerated 2π-electrocyclic ring opening of 6,6-dihalobicyclo[3.1.0]hexan-2-ones at low temperature to give the corresponding meta-halophenols in good to high yields (18 examples, 29–92 % yield, average: 65 %). Many of the phenols have unconventional substitution patterns and are reported here for the first time. Furthermore, the strength of the methodology was shown by the total synthesis of the densely functionalized phenolic natural product caramboxin (isolated as the lactam dehydrate). The reaction mechanism underlying the anion-acceleration was investigated in an ab initio study, which concluded that base-mediated proton abstraction anti to the concurrently departing endo-bromine was the initiating step in an overall concerted reaction mechanism leading directly to the meta-halophenol. 相似文献
326.
Guo Fei Zhang Xuexia Yang Rilong Salmén Lennart Yu Yan 《Cellulose (London, England)》2021,28(13):8867-8876
Cellulose - Parenchyma cells and fibers are the two dominant types of cells in the bamboo culm. Their mechanical and biological functions in bamboo differ substantially, derived from their cell... 相似文献
327.
Garg Mohit Apostolopoulou-Kalkavoura Varvara Linares Mathieu Kaldéus Tahani Malmström Eva Bergström Lennart Zozoulenko Igor 《Cellulose (London, England)》2021,28(14):9007-9021
Cellulose - Foams made from cellulose nanomaterials are highly porous and possess excellent mechanical and thermal insulation properties. However, the moisture uptake and hygroscopic properties of... 相似文献
328.
Baardman Lennart Cristian Rares Perakis Georgia Singhvi Divya Skali Lami Omar Thayaparan Leann 《Mathematical Programming》2023,197(1):1-26
Mathematical Programming - In this paper, we present a new framework of bi-level unconstrained minimization for development of accelerated methods in Convex Programming. These methods use... 相似文献