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排序方式: 共有103条查询结果,搜索用时 171 毫秒
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Dr. Jie Yao Dr. Xiaobo Feng Dr. Jiaqi Fan Shoya Komiyama Dr. Yasuharu Kugue Dr. Xiaoyu Guo Dr. Yingluo He Prof. Guohui Yang Prof. Noritatsu Tsubaki 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(59):e202201783
The non-petroleum synthesis route of ethanol from syngas (H2+CO) with methyl acetate (MA) as the core intermediate product has been confirmed as an excellent industrialization route for high purity ethanol production. However, as the central part of this tandem-catalysis path, the carbonylation of dimethyl ether (DME) to MA is limited by the undesirable catalytic activity and stability of zeolite catalysts. Herein, a facile inhibitor-assisted strategy was developed for constructing self-assembled nano-Mordenite (nano-MOR) zeolites without using any expensive or complex template. A nano-filamentous MOR zeolite with only 70 nm crystal diameter was successfully synthesized by selectively controlling the crystal growth orientation with a specific inhibitor. The catalytic performance of self-assembled nano-MOR catalysts was remarkably outstanding in DME carbonylation reaction. The highest Space-Time Yield (STY) of MA was achieved over Nanofilament MOR (NF-MOR), which was significantly improved comparing with that of the traditional Ellipsoid-MOR (ES-MOR) [3780 mmol/(kg ⋅ h) vs. 1368 mmol/(kg ⋅ h)]. One-step ethanol synthesis was realized by combining the MOR catalyst and an innovative self-reduced Cu-ZnO/SiO2 (CZ/SiO2) catalyst in a rationally designed dual-bed catalysis system. Adopting the tailor-made NF-MOR&CZ/SiO2 combination, it obtained the highest STY of ethanol, about 4 times of the conventional ES-MOR&CZ combination [1800 mmol/(kg ⋅ h) vs. 476 mmol/(kg ⋅ h)]. The present self-assembled nano-MOR zeolites synthetic strategy opens a new way for the fabrication of high-performance zeolites for practical industrial applications in catalytic conversions of one-carbon (C1) small molecules to high value-added chemicals. 相似文献
43.
Hajime Maeda Takahiro Okumura Yasuharu Yoshimi Kazuhiko Mizuno 《Tetrahedron: Asymmetry》2009,20(3):381-384
Photoirradiation of 1-cyano-2-(5-methyl-2-oxa-4-hexenyl)naphthalene, included in NaY zeolites along with chiral inductors, such as diethyl tartrate or phenylalaninol, gives an intramolecular [2+2] photocycloadduct with a maximum 15% ee. The degree of enantioselectivity was found to depend on the Si/Al ratio, the nature of the cations in the zeolites, the structure of the chiral inductors, and the molar ratio of substrate and chiral inductors. 相似文献
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Physical and gas transport properties of novel hyperbranched polyimide–silica hybrid membranes were investigated and compared with those of linear‐type polyimide–silica hybrid membranes with similar chemical structures. Hyperbranched polyamic acid, as a precursor, was prepared by polycondensation of a triamine, 1,3,5‐tris(4‐aminophenoxy)benzene (TAPOB), and a dianhydride, 4,4′‐(hexafluoroisopropylidene)diphthalic anhydride (6FDA). 6FDA‐TAPOB hyperbranched polyimide–silica hybrids were prepared using the polyamic acid, water, and tetramethoxysilane (TMOS) by sol–gel reaction. 5% weight‐loss temperature of the 6FDA‐TAPOB hyperbranched polyimide–silica hybrids determined by TG‐DTA measurement considerably increased with increasing silica content, indicating effective crosslinking at polymer–silica interface. CO2, O2, N2, and CH4 permeability coefficients of the 6FDA‐based polyimide–silica hybrids increased with increasing silica content. In addition, CO2/CH4 selectivity of the 6FDA‐TAPOB–silica hybrids remarkably increased with increasing silica content. From 129Xe NMR analysis, characteristic distribution and interconnectivity of cavities created around polymer–silica interface were suggested in the 6FDA‐TAPOB–silica hybrids. It was indicated that size‐selective separation ability is effectively brought by the incorporation of silica for the 6FDA‐TAPOB hyperbranched polyimide–silica hybrid membranes. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 291–298, 2006 相似文献
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Yukio Nagasaki Eiichi Honzawa Masao Kato Yasuharu Kihara Teiji Tsuruta 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(6):457-470
Abstract Reaction between dimethyldivinylsilane (1) and N,N′-diethyl-N-lithio-ethylenediamine (2a) in the presence of N,N′-diethylethylenediamine (3a) in THF at 20°C gave a monoadduct, 3,3-dimethyl-6-ethyl-3-sila-6,9-diaza-1-undecene (4a). An anionic self-polyaddition reaction of 4a in the presence of lithium diisopropylamide (LDA) proceeded to form oligomers. Each of the oligomers thus obtained was found to carry a polymerizable vinylsilane moiety at the oligomer chain terminal. As a result, a new type of macromonomer having alternating repeating units of ethylenediamine and organosilyl groups was synthesized. Acid-base titration showed the macromonomer to have unique characteristics on protonation of diamine moieties. Anionic polyaddition reactions between 1 and N-lithio-piperazine (2b) in the presence of piperazine (3b) also gave a macromonomer consisting of alternating repeating units of piperazine and organosilyl groups (4b). Radical copolymerizations of styrene with 5b gave comblike graft copolymers. 相似文献
48.
Ikeshoji T Otani M Hamada I Okamoto Y 《Physical chemistry chemical physics : PCCP》2011,13(45):20223-20227
The water dissociation reaction and water molecule configuration on a positively charged platinum (111) surface were investigated by means of first principles molecular dynamics under periodic boundary conditions. Water molecules on the Pt surface were mostly in the O-down orientation but some H-down structures were also found. OH(-) ion, generated by removing H from H(2)O in the bulk region, moved to the Pt surface, on which a positive charge is induced, by a Grotthuss-like proton-relay mechanism and adsorbed on it as OH(Pt). Hydrogen atom exchange between OH(Pt) and a near-by water molecule frequently occurred on the Pt surface and had a low activation energy of the same order as room temperature energy. When a positive charge (7 μC cm(-2)) was added to the Pt surface, H(3)O(+) and OH(Pt) were generated from 2H(2)O on the Pt. This may be coupled with an electron transfer to the Pt electrode [2H(2)O → H(3)O(+) + OH(Pt) + e(-)]. The opposite reaction was also observed on the same charged surface during a simulation of duration about 10 ps; it is a reversible redox reaction. When further positive charge (14 μC cm(-2)) was added, the reaction shifted to the right hand side completely. Thus, this one-electron transfer reaction, which is a part of the oxygen electrode reaction in fuel cells and water electrolysis, was confirmed to be a low activation energy process. 相似文献
49.
Toshiaki Shimasaki Shunsuke Okajima Rino Ishikawa Shinji Kawaguchi Takeshi Akimoto Naoto Asano Tetsuo Iwanaga Motonori Watanabe Naozumi Teramoto Mitsuhiro Shibata 《Tetrahedron》2018,74(20):2454-2465
Fully conjugated macrocycles 1a?1c composed of m-diethynylene-phenylene-bridged two dibenzofuran, dibenzothiophene and carbazole units were synthesized via Sonogashira cross coupling reactions under high-diluted condition. These conjugated macrocycles were fully characterized by 1H NMR, 13C NMR, FT-IR, Mass spectroscopies and elemental analysis. Photophysical and redox properties of 1a?1c were investigated by means of UV–vis/fluorescence spectroscopies and cyclic voltammetry, respectively, and those features were compared with those of the corresponding linear phenylethynyldibenzoheterols 11a?11c. Furthermore, their structural and electronic insights were studied by theoretical calculations at the B3LYP/cc-pVDZ//B3LYP/6-31G(d) level of theory. 相似文献
50.
We designed a planar-waveguide quasi-phase-matched second-harmonic-generation device, which consists of a Y-cut periodically poled 5 mol.% MgO-doped LiNbO3 core and SiO2 claddings, that provided a 1.08 W green light with 30% conversion efficiency by using a 7 mm long sample at room temperature. The highest conversion efficiency of 49% at 0.88 W second-harmonic generation was attained by using an 18 mm long device. 相似文献