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191.
Energy distributions of electrons emitted from polycrystalline naphthacene due to the impact of metastable argon or krypton atoms were measured. The energy distribution peaks, except for large peaks appearing near zero eV, correspond to the kinetic energies estimated from photoelectron spectra on the assumption that the excitation energies of the metastable atoms are transferred to the electrons in the valence bands. The results are interpreted as the occurrence of Penning ionization (Auger de-excitation) on the naphthacene surface. 相似文献
192.
Phenol synthesis by liquid-phase oxidation of benzene with molecular oxygen over iron-heteropoly acid 总被引:2,自引:0,他引:2
Young-Jong Seo Yoshio Mukai Tomohiko Tagawa Shigeo Goto 《Journal of molecular catalysis. A, Chemical》1997,120(1-3):149-154
The phenol synthesis by liquid-phase oxidation of benzene with molecular oxygen over iron-heteropoly acid (HPA) system was studied. When iron salts were used with H3PW12O40, the highest activity was obtained. Spectroscopic studies showed that the state of the iron ion was changed after interaction with heteropoly acid (HPA) while the Keggin structure of HPA remained. The acidic nature of HPA activated benzene to form cationic species. Insoluble iron ion-exchanged heteropoly acid was obtained by partial ion exchange method, which also showed high activity on oxidation of benzene with molecular oxygen. The effects of reaction conditions were studied and the mechanism of deactivation was discussed. For the regeneration of catalytic activity, the addition of
-ascorbic acid as a reducing agent was suggested. 相似文献
193.
Tomohiko Tagawa Yasuhito Fushii Hisao Imai Masahiro Yoshimura Shigeyuki Somiya 《Reaction Kinetics and Catalysis Letters》1989,39(1):49-53
Catalytic properties of a series of HfO2–Eu2O3 fine crystalline powders were examined by the isomerization of n-butenes. HfO2 pretreated at 873 K showed a high activity. It decreased with the addition of the Eu component. The product distributions are discussed on the basis of the acid-base properties.
HfO2–Eu2O3 -. HfO2, 873 K, . Eu. - .相似文献
194.
Toshiaki Munakata Tomohiko Hirooka Kozo Kuchitsu 《Journal of Electron Spectroscopy and Related Phenomena》1980,18(1):51-59
Energy distributions of the electrons ejected from the evaporated film surfaces of LiF, LiCl, LiBr, NaF and NaCl by the impact of metastable He and Ne atoms have been measured. The observed distribution curves have two distinct structures: one peak is identified as the valence band structure caused by Penning ionization, while the other peak is ascribed to scattered electrons. The positions of the valence band peaks are shifted to lower ionization energy from the corresponding photoelectron peaks (by 0.1–1.5 eV depending on the substance). In contrast to the photoelectron spectra, the structure attributable to conduction bands appears only very weakly. The relative intensity of the peak caused by scattered electrons is either strong or weak depending on the combination of the metastable atom and the sample. The interpretation of this observation is that the scattered electron peak is enhanced when the energy of the metastable atom exceeds twice the band gap energy, i.e. when the electron—electron scattering of Penning electrons in the solid is feasible. 相似文献
195.
Nakayama T Isobe T Nakamiya K Edmonds JS Shibata Y Morita M 《Magnetic resonance in chemistry : MRC》2005,43(7):543-550
The high toxicity of diphenylarsinic acid, found in ground water and well water as a probable consequence of the inappropriate disposal of warfare agents, prompted us to study the reaction, monitored by 1H and 13C NMR spectroscopy, of the compound and its monophenyl analogue, phenylarsonic acid, with cellular thiols as represented, in particular, by glutathione. Glutathione reduced the phenylarsenic acids to trivalent forms and complexed them: diphenylarsinic acid to a monoglutathione adduct and phenylarsonic acid to a diglutathione adduct. The complexes were characterized by 1H and 13C NMR spectroscopy and mass spectrometry. The NMR spectra showed the diastereotopic nature of the two phenyl groups in the diphenylarsinic acid-glutathione compound, and of the two glutathione residues in the phenylarsonic acid-diglutathione complex. The stereochemistry of thiol compounds of phenylarsonic acid was further explored by 1H and 13C NMR spectroscopy of the L-cysteine complex. The diphenylarsinic acid-glutathione complex was stable below pH 12 but at higher pH the complex dissociated into diphenylarsinous acid and reduced glutathione. The released diphenylarsinous acid then oxidized to diphenylarsinic acid with a half-life of about 7 h at pH 13 and at room temperature. 相似文献
196.
Sha Y Tashima T Mochizuki Y Toriumi Y Adachi-Akahane S Nonomura T Cheng M Ohwada T 《Chemical & pharmaceutical bulletin》2005,53(10):1372-1373
We found that a variety of compounds containing partial structures of tamoxifen showed activity as chemical modulators of large-conductance calcium-activated K+ channels (BK channels). 相似文献
197.
Tomohiko Sakaguchi Kouji Kashiwa Masayuki Matsuzaki Hiroaki Kouno Masanobu Yahiro 《Central European Journal of Physics》2008,6(1):116-121
We test the stability of the mean field solution in the Nambu-Jona-Lasinio model in a semi-quantitative manner. For stable
solutions with respect to both the σ and π directions, we investigate effects of the mesonic loop corrections of 1/N
c
, which correspond to the next-to-leading order in the 1/N
c
expansion, on the high density chiral phase transition. The corrections weaken the first order phase transition and shift
the critical chemical potential to a lower value. At N
c
= 3, however, instability of the mean field effective potential prevents us from determining the minimum of the corrected
one.
相似文献
198.
Tomohiko Tagawa Naofumi Nomura Masashi Shimakage Shigeo Goto 《Research on Chemical Intermediates》1995,21(2):193-202
Methanol was synthesized from carbon dioxide and hydrogen over various supported copper catalysts. A support was selected from the viewpoint of its acid-base properties. Acid supports showed high selectivity but low activity. Neutral and basic supports produced only carbon monoxide. Amphoteric supports showed high activities. Among them, TiO2 supports suppressed the reverse water gas shift reaction (CO formation). The role of supports was discussed on the basis of in situ infrared results. 相似文献
199.
It has been experimentally established that the proton affinities (PA), as well as the solution basicities (pK(BH)(+)), of aziridine derivatives are much smaller than those of the corresponding pyrrolidines and piperidines, though the basic strength of azetidines is close to those of pyrrolidines and piperidines. A simple idea of dependence of the basic strength on bond angles seems to be invalid. Because the basicity of cyclic amines is a fundamental property in organic chemistry, we revisited this topic in order to clarify quantitatively the intrinsic origin of the strength of Lewis basicity of the relevant amines, in particular, based on the local electron-donating ability of the amine nitrogen atoms evaluated in terms of the localized reactive hybrid orbital (RHO) concept. In the cases of representative N-substituents such as hydrogen, methyl, and phenyl groups, the electron-donating energy level of the nitrogen center, obtained by maximizing a kind of superdelocalizability, was shown to be correlated with the magnitudes of experimental and calculated gas-phase proton affinities. The present results strongly support the view that the C-N-C bond angle, i.e., angle strain, in the cyclic amines is not the major source of the difference in strength of basicity of these amines, but rather, the degree of pyramidalization around the nitrogen atom has a significant impact on the electron-donating ability of the nitrogen lone-pair orbital. 相似文献
200.
Effect of acid-base properties on copper catalysts for hydrogenation of carbon dioxide 总被引:1,自引:0,他引:1
Naofumi Nomura Tomohiko Tagawa Shigeo Goto 《Reaction Kinetics and Catalysis Letters》1998,63(1):21-25
Acidic or basic components as co-catalysts were added to the Cu-based catalysts for hydrogenation of CO2. Effects of acid-base properties on the catalytic activity and methanol selectivity are discussed. 相似文献