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排序方式: 共有143条查询结果,搜索用时 78 毫秒
11.
Dr. Tomoki Ogoshi Ryuta Sueto Kumiko Yoshikoshi Dr. Yoko Sakata Prof. Shigehisa Akine Prof. Tada‐aki Yamagishi 《Angewandte Chemie (International ed. in English)》2015,54(34):9849-9852
Activated perethylated pillar[5]arene crystals show an unexpected alkane‐shape‐ and ‐length‐selective gate‐opening behavior. Activated crystals were obtained upon removing solvents from perethylated pillar[5]arene crystals by heating. The activated crystals could quantitatively take up n‐alkanes with carbon chains containing more than five carbon atoms as a consequence of their gate‐opening pressure. As the chain length of the n‐alkanes increased, the gate pressure decreased. A transformation into a herringbone structure was induced when n‐hexane was used as a guest. By contrast, cyclic and branched alkanes were not taken up and could not induce a crystal transformation because they were too large to fit in the cavities of the pillar[5]arene. Alkane‐shape‐selective molecular recognition of pillar[5]arenes in the solution state was translated into the vapor/crystal state. 相似文献
12.
A Strategy to Control the Reactivation of Frustrated Lewis Pairs from Shelf‐Stable Carbene Borane Complexes 下载免费PDF全文
Dr. Yoichi Hoshimoto Takuya Kinoshita Prof. Dr. Masato Ohashi Prof. Dr. Sensuke Ogoshi 《Angewandte Chemie (International ed. in English)》2015,54(40):11666-11671
N‐Phosphine oxide substituted imidazolylidenes (PoxIms) have been synthesized and fully characterized. These species can undergo significant changes to the spatial environment surrounding their carbene center through rotation of the phosphine oxide moiety. Either classical Lewis adducts (CLAs) or frustrated Lewis pairs (FLPs) are thus formed with B(C6F5)3 depending on the orientation of the phosphine oxide group. A strategy to reactivate FLPs from CLAs by exploiting molecular motions that are responsive to external stimuli has therefore been developed. The reactivation conditions were successfully controlled by tuning the strain in the PoxIm–B(C6F5)3 complexes so that reactivation only occurred above ambient temperature. 相似文献
13.
Photoswitching of the transformation between seconds and hours time-scales is demonstrated using the threading of per-hydroxylated pillar[5]arene onto the azobenzene-end of a viologen derivative. When the azobenzene moiety was in the trans form, the threading of per-hydroxylated pillar[5]arene quickly took place at 25 °C and could not be monitored directly. The exchange rate (k) and half-life time (t(1/2)) examined by 2D EXSY NMR spectroscopy were found to be 0.209 ± 0.013 s(-1) and 3.33 ± 0.21 s, respectively. In contrast, the cis form of the azobenzene moiety required very long time (k = 2.14 ± 0.27 × 10(-5) s(-1), t(1/2) = 9.13 ± 1.2 h) to thread per-hydroxylated pillar[5]arene at 25 °C. Photoisomerization from the trans to the cis form generated the following increment of free energy of activation at 25 °C: ΔG(in)(?) (cis form) - ΔG(in)(?) (trans form) = 22.8 ± 0.24 kJ mol(-1), which led to the time-scale transformation. The tuning of the threading was also accomplished by heating/cooling: the rate constants increased on heating and decreased on cooling. 相似文献
14.
Ogoshi T Kitajima K Fujinami S Yamagishi TA 《Chemical communications (Cambridge, England)》2011,47(36):10106-10108
The reaction of 1,4-dimethoxybenzene and paraformaldehyde using AlBr(3) yields multiple-deprotected pillar[5]arenes. A1/B2 di-deprotected pillar[5]arene can be isolated by silica gel chromatography and washing procedures. The X-ray structure and polymerization of the A1/B2 di-deprotected pillar[5]arene are reported. 相似文献
15.
In this study, the combined effects of high pressure and sodium hydrogen carbonate (NaHCO3) treatment on the physical and chemical properties, and palatability of pork ham, a tough and under-utilized meat, were investigated. Assessment of meat properties with heat treatment, after exposure to NaHCO3 and high pressure treatment, revealed an increase in water content, and decreased weight reduction and rupture stress. The free amino acid content of meat samples increased with NaHCO3 and high pressure treatment. The effect of high pressure processing was especially notable at a pressure of 300 MPa. Sensory evaluation showed that meat subjected to high pressure processing after NaHCO3 treatment was tender and juicy. In addition, the sample produced minimal residue in the mouth and was characterized by a good taste. 相似文献
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Dmytro Strilets Dr. Shixin Fa Arthur Hardiagon Dr. Marc Baaden Prof. Tomoki Ogoshi Dr. Mihail Barboiu 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(51):23413-23419
Artificial water channels mimicking natural aquaporins (AQPs) can be used for selective and fast transport of water. Here, we quantify the transport performances of peralkyl-carboxylate-pillar[5]arenes dimers in bilayer membranes. They can transport ≈107 water molecules/channel/second, within one order of magnitude of the transport rates of AQPs, rejecting Na+ and K+ cations. The dimers have a tubular structure, superposing pillar[5]arene pores of 5 Å diameter with twisted carboxy-phenyl pores of 2.8 Å diameter. This biomimetic platform, with variable pore dimensions within the same structure, offers size restriction reminiscent of natural proteins. It allows water molecules to selectively transit and prevents bigger hydrated cations from passing through the 2.8 Å pore. Molecular simulations prove that dimeric or multimeric honeycomb aggregates are stable in the membrane and form water pathways through the bilayer. Over time, a significant shift of the upper vs. lower layer occurs initiating new unexpected water permeation events through toroidal pores. 相似文献
19.
Fluorinated Vinylsilanes from the Copper‐Catalyzed Defluorosilylation of Fluoroalkene Feedstocks 下载免费PDF全文
Hironobu Sakaguchi Prof. Dr. Masato Ohashi Prof. Dr. Sensuke Ogoshi 《Angewandte Chemie (International ed. in English)》2018,57(1):328-332
Herein, a copper‐catalyzed C?F bond defluorosilylation reaction of tetrafluoroethylene and other polyfluoroalkenes is described. Mechanistic studies, based on a series of stoichiometric reactions with copper complexes, revealed that the key steps of this defluorosilylation reaction are 1) the 1,2‐addition of a silylcopper intermediate to the polyfluoroalkene and 2) a subsequent selective β‐fluorine elimination, which generates a Cu?F species. The β‐fluorine elimination is facilitated by Lewis acidic F?Bpin, which is generated in situ during the defluorosilylation. 相似文献
20.
Ogoshi S Arai T Ohashi M Kurosawa H 《Chemical communications (Cambridge, England)》2008,(11):1347-1349
The formation of a nickeladihydrofuran by oxidative cyclization of an alkyne and an aldehyde with nickel(0) has been demonstrated; the transformation of the nickeladihydrofuran into an enone by decomposition, a lactone by carbonylation and an allylic alcohol by treatment with ZnMe(2) suggests that nickeladihydrofuran is an important key intermediate in a variety of catalytic reactions. 相似文献