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31.
Sato K Akai S Sugita N Ohsawa T Kogure T Shoji H Yoshimura J 《The Journal of organic chemistry》2005,70(19):7496-7504
[reactions: see text] The novel and stereocontrolled synthesis of (+/-)-tetrodotoxin from myo-inositol is described. The key steps involve the stepwise oxidation of hydroxyl groups to the carbonyl function, followed by the addition of specific nucleophiles, including the successive spiro alpha-chloroepoxide formation and its ring-opening with the azide anion, to give the desired branched chain structures (5-->6, 17-->18-->19-->20 and 23-->24-->25) with the desired regio- and stereoselectivities in high yields. The stepwise conversion of the alpha-azido aldehyde 25 to the delta-lactone 29, followed by reduction of the azide, introduction of a guanidine moiety, aldehyde formation, and deprotection, produced the (+/-)-tetrodotoxin. 相似文献
32.
The dissociative excitation reaction of BrCN induced by the products of the electron cyclotron resonance (ECR) plasma flow of He was studied based on the electrostatic-probe measurements and on the optical emission spectra of the B2Σ+ − X2Σ+ transition of CN radicals. The partial pressures of He and BrCN were 3 and 1 mTorr, respectively, and the partial pressure of H2O, PH2O, was in the range of 0.0–0.6 mTorr. The electron density, ne, showed a negative dependence on PH2O as (2.63 ± 0.13) × 1012 − (0.23 ± 0.10) × 1012 m−3, and the electron temperature, Te, a positive dependence, (2.38 ± 0.36) − (4.51 ± 0.15) eV. The CN(B2Σ+ − X2Σ+) emission intensity showed a negative dependence on PH2O. Based on a kinetic analysis of these PH2O dependencies, the decomposition of BrCN does not proceed via electron impact; instead, decomposition proceeds via the processes involving He+ and/or He metastable atoms. 相似文献
33.
Iwao Ojima Shin-Ichi Inaba Tetsuo Kogure Yoichiro Nagai 《Journal of organometallic chemistry》1973,55(1):C7-C8
Dibromomethyllithium and its homologues RCBr2Li (R = Bu, Me3Si, Br) are prepared by metallation of the corresponding α,α-dibromo compounds with lithium diisopropylamide in THF at low temperature. Various coupling reactions are described (alkylation, hydroxyalkylation). New one-step preparations of α-bromoepoxides and α-bromoketones are reported. 相似文献
34.
Summary The thin-layer chromatographic behavior of 57 metals on a weakly acidic cation exchanger, carboxymethyl (CM) cellulose, has investigated systematically in sulfuric acid (0.01–1.0 M) and the acidic ammonium sulfate media. Thin-layer plates of a microcrystalline cellulose, Avicel SF, were also used to compare with the chromatographic behavior of the metals in the acidic sulfate system. The Rf values obtained for many metals tested on CM-cellulose plates increase with increasing concentration of sulfuric acid. Most of metals tested are distributed chromatographically on the CM-cellulose in the low acid concentration. The characteristic retention of many metals, including sulfato-complexes forming metals, on the CM-cellulose can be observed in ammonium sulfate solutions of a low concentration of the acid. Useful multicomponent separations of analytical interest on CM-cellulose layers are presented to demonstrate the use of Rf measurements for predicting separations in the acid and the acidic ammonium sulfate systems. 相似文献
35.
Saruwatari K Sato H Kogure T Wakayama T Iitake M Akatsuka K Haga M Sasaki T Yamagishi A 《Langmuir : the ACS journal of surfaces and colloids》2006,22(24):10066-10071
Electrical conductivity of titania nanosheets was investigated for a single-layered Langmuir-Blodgett (LB) film deposited onto a comb-type electrode (5 or 10 microm (electrode spacing) x 8 mm (electrode width)). The photoresponsive electrical properties of the film were investigated by irradiating with a Xe lamp under various atmospheric conditions. The atmosphere was controlled by introducing either oxygen or nitrogen gases containing different amounts of water vapor. As a result, the LB film behaved as an insulator with little photoresponse under dry atmospheric conditions. It became conductive on illuminating with a Xe lamp under a wet oxygen atmosphere. Conductivity increased with the increase of irradiation time (0-30 min) to attain a stationary value in 1 h. The highest conductive state thus attained lasted for several hours in the dark. The impedance of the film was measured over the frequency range of 1 MHz to 50 Hz by varying the relative humidity of an atmosphere from 0 to 100%. The results were analyzed by assuming an equivalent circuit consisting of one resistance (R) with constant Warburg component (W) and one capacitance (C) in parallel. The R component depended remarkably on the relative humidity, while the C component stayed nearly at the constant value. The dependence of R on water vapor (PH2O) was expressed by R = A[PH2O]n with A = constant and n = -2.9. The results were rationalized in terms of the surface modification of titania nanosheets to hydrophilic nature under the illumination of UV light. 相似文献
36.
Nabil M. Hassan Tetsuo Ishikawa Masahiro Hosoda Atsuyuki Sorimachi Shinji Tokonami Masahiro Fukushi Sarata K. Sahoo 《Journal of Radioanalytical and Nuclear Chemistry》2010,283(1):15-21
The specific activities of 238U, 232Th, and 40K in selected building materials used in Japan were measured using a high-purity germanium detector. The uranium and thorium concentrations were determined from same samples using inductively coupled plasma mass spectrometry. There was a good agreement between the measurement of uranium and thorium with both methods (R 2 = 0.94, and 0.97, respectively). Based on the specific activities, we have estimated some hazard indexes such as radium equivalent activities (Ra eq), external hazard index (H ex), internal hazard index (H in), annual gonadal equivalent dose (AGED), internal alpha dose, mass exhalation rate and emanation coefficient of radon. 相似文献
37.
Iwao Ojima Mitsuru Nihonyanagi Tetsuo Kogure Miyoko Kumagai Shuji Horiuchi Kimiyo Nakatsugawa Yoichiro Nagai 《Journal of organometallic chemistry》1975,94(3):449-461
The hydrosilylation of various carbonyl compounds such as simple aldehydes, simple ketones, α,β-unsaturated carbonyl compounds, α-diketones, acyl cyanides and ketones having an electron-withdrawing group on the α-carbon using tris(triphenylphosphine)chlororhodium as a catalyst is described. Solvolysis of these silyl ethers and silyl enol ethers afforded the corresponding reduced products. The hydrosilylation of α,β-unsaturated carbonyl compounds was found to proceed by 1,4-addition. An oxidative adduct of triethylsilane to the rhodium-(I) complex was obtained as a reaction intermediate. The structure of the adduct was discussed on the basis of its IR and far-IR spectra. 相似文献
38.
Formation of Anatase Nanocrystals in Sol-Gel Derived TiO2-SiO2 Thin Films with Hot Water Treatment 总被引:8,自引:0,他引:8
Yoshinori Kotani Atsunori Matsuda Masahiro Tatsumisago Tsutomu Minami Taku Umezawa Toshihiro Kogure 《Journal of Sol-Gel Science and Technology》2000,19(1-3):585-588
We have successfully prepared transparent and porous anatase nanocrystals-dispersed films by treating the sol-gel derived TiO2-SiO2 films containing poly(ethylene glycol), PEG, with hot water. This process was done at temperatures lower than 100°C under atmospheric pressure, and thus anatase nanocrystals-dispersed films can be formed on various kinds of substrates including organic polymers with poor heat resistance. The changes in structure and composition of the TiO2-SiO2 gel films with hot water treatment were related to the formation process of anatase nanocrystals in the TiO2-SiO2 gel films with hot water treatment. The formation of anatase nanocrystals was found to proceed to hydrolysis of Si–O–Ti bonds and dissolution of SiO2 component. In addition, porous film structure formed by leaching of PEG with hot water treatment led to homogenous dispersion of anatase nonocrystals in the films. 相似文献
39.
Asymmetric hydrogenations of n-propyl pyruvate and ketopantoyl lactone catalyzed by rhodium complexes with (—) DIOP and BPPM were carried out under a variety of conditions. It was found that i) the Schrock-Osborn mechanism was not operative in these reactions at all since no acceleration of the reaction rate by the addition of water (1%) was observed, ii) there was a clear difference between cationic and neutral (in situ) rhodium catalysts in their enantioselectivity, and iii) there was a remarkable solvent effect on the extent and direction of asymmetric induction. Possible mechanisms are discussed on the basis of these results. 相似文献
40.