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31.
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Susumu Honda Atsushi Taga Kazuaki Kakehi Shigetaka Koda Yoshihiko Okamoto 《Journal of chromatography. A》1992,590(2):364-368
Cefixime (CX), an oral cephalosporin antibiotic, and its metabolites in human digestive organs were separated by various modes of high-performance capillary electrophoresis. The zone electrophoresis mode in phosphate buffer (pH 6.8) containing 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulphonate gave the best separation, permitting the complete resolution of CX and all of five metabolites. On the other hand, the plain zone electrophoresis mode in phosphate buffer (pH 6.8) offered a simple procedure for the direct determination of urinary CX concentration using intact urine samples. 相似文献
33.
From the leaves of Acanthopanax hypoleucus Makino (Araliaceae), five triterpenoidal saponins, having oleanolic acid and hederagenin as sapogenins, were isolated. On the basis of chemical and spectral data, the structures of two new saponins, named hypoleucosides A (1), and B (5) were elucidated as follows: 1; 3-O-beta-D-glucopyranosyl 11 alpha-methoxy-oleanolic acid 28-O-beta-D-glucopyranosyl ester, 5; 3-O-beta-D-glucopyranosyl-(1----2)-alpha-L-arabinopyranosyl-(1---- 4)-beta-D-glucopyranosyl oleanolic acid 28-O-beta-D-glucopyranosyl-(1----6)-beta-D-glucopyranosyl ester. 相似文献
34.
Hideki Kubo Shigetaka Hayano Toshio Masuda 《Journal of polymer science. Part A, Polymer chemistry》2000,38(15):2697-2701
The polymerization of aliphatic disubstituted acetylenes was examined with MoOCl4–n‐Bu4Sn–EtOH (1/1/2) ternary catalyst in anisole at 0 °C. Various linear aliphatic disubstituted acetylenes such as 2‐nonyne provided polymers with narrow molecular weight distributions (weight‐average molecular weight/number‐average molecular weight = 1.05–1.20). The living character of the polymerization was proven by both the time profile of the polymerization and the multistage polymerization of 2‐nonyne. The initiation efficiency was about 3%, which is rather low. Although 5‐dodecyne, which has a triple bond in a more inner part, polymerized more slowly than 2‐nonyne, their living characters were hardly different. Diblock copolymers were synthesized by the sequential living polymerization of internal linear alkynes. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 2697–2701, 2000 相似文献
35.
Masato Sakaguchi Katsuhiro Yamamoto Shigetaka Shimada Masahiro Sakai 《Journal of Polymer Science.Polymer Physics》1998,36(12):2095-2102
Poly(isobutylene) (PIB) chains with a radical at the chain end were graft-copolymerized on the poly(tetrafluoroethylene) (PTFE) surface in vacuo at 77 K. The PIB chains tethered on the PTFE surface in vacuo were regarded as isolated chains from neighboring tethered PIB chains. The molecular motion of the ends of the isolated PIB chains was observed by an electron spin resonance (ESR) spectrometer in the temperature range from 3 to 125 K, which was lower than Tg of PIB, 200 K,1 and two motion modes were found: One is a quantum tunneling of the methyl group located at the chain end at 3 K, and the other is an interconformation transition with freely rotating methyl group at the end at 77 K, where the transition rate was estimated to be 15 MHz at that temperature. The transition rate increased with an increase in temperature. The activation energy of the transition was estimated to be 370 J/mol. The high mobility and low activation energy was attributed to the isolation of PIB chains in vacuo. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 2095–2102, 1998 相似文献
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37.
Yasuro Hori Shigetaka Shimada Hisatsugu Kashiwabara 《Journal of Polymer Science.Polymer Physics》1984,22(8):1407-1415
The decay of peroxy radicals trapped in irradiated isotactic polypropylene has been studied by ESR in air at various temperatures between 284 and 309 K. All the ESR spectra obtained at the various reaction stages are shown to be composed of two components arising from a mobile fraction and an immobile fraction. Only the mobile peroxy radicals decay; those belonging to the immobile fraction are stable. Various reaction mechanisms are examined in order to explain the experimental results; it is concluded that the decay reaction is controlled by diffusion of peroxy radicals and that the immobile peroxy radicals play no role in the decay reaction. Intermolecular hydrogen abstraction of the peroxy radicals, rather than intramolecular abstraction, is suggested as the rate-determining reaction. 相似文献
38.
Shigeo Hara Katsuhiro Yamamoto Shigetaka Shimada Hajime Nishi 《Journal of Polymer Science.Polymer Physics》2004,42(8):1539-1547
Temperature‐dependent electron spin resonance spectra of main‐chain free radicals, ? CF2(β)? C · F(α)? CF2(β)? , in poly(tetrafluoroethylene) (PTFE) were analyzed by the change in the hyperfine splitting due to β‐fluorines, which was a decreasing function of the observation temperature. The results were interpreted in terms of the rotational vibration around the Cα? Cβ bond. The amplitude of the vibration was estimated on the assumption of its harmonic oscillation. The vibration of the PTFE chain was found to have a large amplitude in comparison with that of a polyethylene chain in single crystals. The vibration of the large amplitude was caused by a weak interchain interaction in the PTFE matrices. The amplitude of the vibration in crosslinked PTFE was much larger than that in noncrosslinked PTFE. This result indicated that the free radicals in crosslinked PTFE were trapped in the amorphous region, which had the disordered sites of crosslinking, whereas the free radicals in noncrosslinked PTFE were mainly trapped in the paracrystalline region. The decay reaction of the free radicals in the PTFE matrices was also related to the heterogeneity in the structure and the rotational vibration. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1539–1547, 2004 相似文献
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40.
The electronic states of lanthanide (Ln) doped CaGa2S4 are investigated by the molecular orbital calculations for a spherical cluster of LnCa8Ga12S24 using the FORTRAN program DVSCAT on the basis of the Discrete Variational method with Xα potentials (DV-Xα). In view of the SCF convergence, the Ln-doped lattice should contract to 85-90% of the mother crystal around the Ln atom for the lightweight lanthanides from Ce to Sm. On the other hand, the lattice contraction is very small for the heavyweight lanthanides, especially for Er, Tm and Yb in contrast to the generally known lanthanide contraction for Ln3+ ions. This is probably attributed to the effective charges of Ln atoms calculated here to be less than +1 for all lanthanides contrary to the chemically accepted value of +3. The energy level scheme of 4f and 5d related molecular orbitals is proposed for each Ln substituting Ca in CaGa2S4, showing that the optical processes relating to the 5d→4f transition must be complicated especially for the lightweight Ln-doped CaGa2S4. 相似文献