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排序方式: 共有249条查询结果,搜索用时 15 毫秒
111.
Keisuke Kato Prof. Satoshi Motodate Tomoyuki Mochida Prof. Takuya Kobayashi Hiroyuki Akita Prof. 《Angewandte Chemie (International ed. in English)》2009,48(18):3326-3328
Boxing clever : Direct conversion of a terminal alkyne group into a β‐methoxyacrylate is realized with the aid of the bis(oxazoline) ligand (box). Acetyl and ketal protecting groups, free hydroxy groups, and acid‐sensitive glycosidic bonds are not affected under the reaction conditions. The one‐pot synthesis of (±)‐dihydrokawain from the homopropargyl alcohol is also achieved. tfa=trifluoroacetate
112.
The reaction of 2,3-anti-2-tert-butyldimethylsiloxy-3-substituted butanal derivative [anti-B, (±)-10 and (±)-16] derived from trans-(2,3)-epoxy butanoate (1) with carbon nucleophiles [α-furyl anion, acetate anion, and indium (In)-assisted allyl anion] has been investigated to give selectively the anti-, anti-adduct D. This anti-stereoselection could be explained by the Felkin-Anh transition state model. Thus obtained anti-, anti-adducts (±)-17 and (±)-38 were formally converted to natural products, (±)-asperlin (2) and (±)-olivose (4), respectively. The major anti-, anti-adduct (±)-26 was converted to (±)-digitoxose (3), while the minor anti-, syn-adduct (±)-27 was also converted to (±)-olivose (4). The reaction of (±)-10 with tert-butyl acetate anion gave predominantly afforded the anti-, anti-adduct (±)-23, which was converted to (±)-1,5-dideoxyhexitol (25). Alternately, the reaction of 2,3-syn-2-tert-butyldimethylsiloxy-3-p-methoxyphenoxy butanal derivative [syn-B, (±)-14] derived from trans-(2,3)-epoxy butanoate (1) with carbon nucleophile (In-assisted allyl anion) afforded a ca. 1 : 1 mixture of the syn-, anti-adduct E [(±)-32 or (±)-34] and syn-, syn-adduct F [(±)-33 or (±)-35]. After separation of this mixture, (±)-34 and (±)-35 were separately converted to (±)-oliose (5) and (±)-boivinose (6), respectively. 相似文献
113.
K. Mitsuhara Y. Kitsudo H. Matsumoto A. Visikovskiy M. Takizawa T. Nishimura T. Akita Y. Kido 《Surface science》2010,604(5-6):548-554
The interaction between Au nano-particles and oxide supports is recently discussed in terms of the catalytic activities. This paper reports the electronic charge transfer between Au nano-particles and TiO2-terminated SrTiO3(0 0 1) substrate, which is compared with that for stoichiometric(S)-, pseudo-stoichiometric(S1)- and reduced(R)-TiO2(1 1 0) supports. We observed the photoelectron spectra of Au 4f, O 2s, Ti 3p, and Sr 4p lines and also measured the work functions for Au/oxides supports using synchrotron-radiation light. As the results, all the O 2s, Ti 3p, and Sr 4p lines for Au/SrTiO3(0 0 1) show lower binding energy shifts in a quite same manner and abrupt increase in the work function is seen in an initial stage. This clearly evidences an electronic charge transfer from the substrate to Au probably due to a much larger work function of Au than SrTiO3(0 0 1), which leads to an upward band bending (0.3 eV) just like a Schottky contact. Electronic charge transfers also take place at Au/S- and Au/S1-TiO2(1 1 0) and Au/R-TiO2(1 1 0) interfaces, where electrons are transferred from Au to S- and S1-TiO2 and from R-TiO2 to Au, as predicted by ab initio calculations. 相似文献
114.
Kazunori Nakano Shigendo Akita Nungruethai Yoswathananont Kazuki Sada Mikiji Miyata 《Journal of inclusion phenomena and macrocyclic chemistry》2004,48(3-4):181-184
Selective incorporation of two aromatic compounds, benzene and ethylbenzene,into an inclusion crystal of cholic acid was investigated. Addition of an excessamount of 1:1 mixture of benzene and ethylbenzene into saturated solution ofcholic acid in 1-butanol led to a spontaneous formation of an inclusion crystal.The co-crystal contained benzene and ethylbenzene at the constant molar ratioof 8:2 irrespective of the relative concentrations of guest and host in the feedsolution, indicating that the resulting crystal consists of the two guests mixedin a single host framework. The resulting ternary crystal had thermal behaviorsimilar to a binary crystal obtained from benzene. In contrast to the guest/hostratio, the benzene/ethylbenzene ratio in the feed solution affected that in theinclusion crystal. Benzene was basically preferred in the cholic acid crystalover ethylbenzene, but the selectivity reversed at an excess amount of ethylbenzene.This separation behavior can be understood in terms of the structural flexibility ofhost frameworks. 相似文献
115.
Tamao Ishida Yuta Onuma Kota Kinjo Akiyuki Hamasaki Hironori Ohashi Tetsuo Honma Tomoki Akita Takushi Yokoyama Makoto Tokunaga Masatake Haruta 《Tetrahedron》2014
Palladium nanoparticles (Pd NPs) encapsulated by conjugated microporous polymers (CMPs) were prepared by the Pd-catalyzed polymerization followed by a thermal treatment with N2 or H2. The Pd catalysts were embedded in the porous network during polymerization and used as a precursor for the generation of Pd NPs in CMP. Although no Pd NPs were formed in the as-synthesized Pd/CMPs, Pd NPs with 1.6–3.5 nm size were formed after the thermal treatment. The obtained Pd/CMP-N2 and -H2 catalysts were highly selective in the hydrogenation of 4-nitrostyrene to 4-ethylnitrobenzene, whereas Pd NPs supported on carbon (Ketjen black) gave a fully reduced product, 4-ethylaniline. Substituents in CMP framework could change the catalytic activity of Pd NPs; hydroxy-substituted CMP encapsulated Pd NPs showed higher catalytic activity than Pd/CMP-H2 for benzyl alcohol oxidation. 相似文献
116.
Dr. Zhiou Li Dr. Yoshihisa Sei Prof. Munetaka Akita Dr. Michito Yoshizawa 《化学:亚洲杂志》2014,9(4):1016-1019
A fluorescent macrocycle containing four anthracene panels linked by meta‐phenylene spacers and amino hinges was synthesized. The macrocycle adopts a twisted, compressed conformation that places embedded anthracene fluorophores in close contact. Emission from the convoluted macrocycle is highly solvatochromic and significantly enhanced as compared with that of the partial structures. 相似文献
117.
Hironori?Tsunoyama Yongmei?Liu Tomoki?Akita Nobuyuki?Ichikuni Hidehiro?Sakurai Songhai?Xie Tatsuya?TsukudaEmail author 《Catalysis Surveys from Asia》2011,15(4):230-239
This article summarizes our recent research on the size-controlled synthesis of Au clusters stabilized by a polymer or supported
by a solid, and related work reported by others. Small Au clusters have excellent, size-specific catalytic activity in the
aerobic oxidation of alcohols and alkanes. 相似文献
118.
Kenta Awa Ryo Akashi Atsunobu Akita Dr. Shin-ichi Naya Prof. Dr. Hisayoshi Kobayashi Prof. Dr. Hiroaki Tada 《Chemphyschem》2019,20(17):2155-2161
Single-crystal SnO2 nanorods were grown on rutile TiO2 with a heteroepitaxial relation of SnO2{001}/TiO2{001} (SnO2-NR#TiO2) by a hydrothermal reaction. Resulting compressive lattice strain in the SnO2-NR near the interface induces a continuous increase in the a-axis length extending over 60 nm to relax towards the [001] direction from the root to the tip. UV-light irradiation of the robust SnO2-NR#TiO2 stably progresses the selective oxidation of ethanol to acetaldehyde with an external quantum yield of 25.6 % at excitation wavelength (λex)=365 nm under ambient temperature and pressure. Spectroscopic analyses and density functional theory simulation results suggested that the extremely high photocatalytic activity stems from the smooth interfacial electron transfer from TiO2 to SnO2-NR through the high-quality junction and subsequent efficient charge separation due to the lattice strain-induced unidirectional potential gradient of the conduction band minimum in the SnO2-NR. 相似文献
119.
Kazuki Miyazawa Dr. Takashi Koike Prof. Dr. Munetaka Akita 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(33):11677-11680
A simple and regiospecific aminohydroxylation of olefins by photoredox catalysis has been developed. N‐protected 1‐aminopyridinium salts are the key compounds and serve as amidyl radical precursors by the action of Ir photocatalysts, fac‐[Ir(ppy)3] and [Ir(ppy)2(dtbbpy)](PF6) (ppy=2‐pyridylphenyl, dtbbpy=4,4′‐di‐tert‐butyl‐2,2′‐bipyridine). The present photocatalytic system allows for synthesis of vicinal aminoalcohol derivatives from olefins with various functional groups under mild reaction conditions with easy handling. 相似文献
120.
Dr. Ryohei Akiyoshi Hikaru Zenno Dr. Yoshihiro Sekine Dr. Manabu Nakaya Prof. Motoko Akita Dr. Daisuke Kosumi Prof. Leonard F. Lindoy Prof. Shinya Hayami 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(5):e202103367
Magnetoelectric (ME) materials exhibiting coupled electric and magnetic properties are of significant interest because of their potential use in memory storage devices, new sensors, or low-consumption devices. Herein, we report a new category of ME material that shows liquid crystal (LC), ferroelectric (FE), and field-induced single molecule magnet (SMM) behaviors. Co(II) complex incorporating alkyl chains of type [Co(3C16-bzimpy)2](BF4)2 ( 1 ; 3C16-bzimpy=2,2’-(4-hexadecyloxy-2,6-diyl)bis(1-hexadecyl-1H-benzo[d]imidazole)) displayed a chiral smectic C mesophase in the temperature range 321 K–458 K, in which distinct FE behavior was observed, with a remnant polarization (88.3 nC cm−2). Complex 1 also exhibited field-induced slow magnetic relaxation behavior that reflects the large magnetic anisotropy of the Co(II) center. Furthermore, the dielectric property of 1 was able to be tuned by an external magnetic field occurring from both spin-lattice coupling and molecular orientational variation. Clearly, this multifunctional compound, combining LC, FE, and SMM properties, represents an entry to the development of a range of next-generation ME materials. 相似文献