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231.
Four new epoxy taxoids were isolated from the needles of Taxus cuspidata. Their structures were established as 2a,9a-diacetoxy-5a-cinnamoyloxy-11,12-epoxy-10ss-hydroxytax-4(20)-en-13-one (1), 2a,10ss-diacetoxy-5a-cinnamoyloxy-11,12-epoxy-9a-hydroxytax-4(20)-en-13-one (2), 2a,9a-diacetoxy-11,12-epoxy-10ss,20-dihydroxytax-4-en-13-one (3) and 2a,10ss-diacetoxy-11,12-epoxy-9a,20-dihydroxytax-4-en-13-one (4) on the basis of spectral analysis including 1H-NMR, 13C-NMR, 1H-1H-COSY, HSQC, HMBC and HRFABMS. Compounds 3 and 4 are the first example of 11,12-epoxy taxoids with C-4 double bond found in T. cuspidata. 相似文献
232.
Hiroaki Taira Hiromasa Nagase Tomohiro Endo Haruhisa Ueda 《Journal of inclusion phenomena and macrocyclic chemistry》2006,56(1-2):23-28
Large-ring cyclodextrins (LR-CDs) composed of more than 9 d-glucose units are not well studied. In this study, LR-CDs composed of 36, 37, 38 and 39 d-glucose units (CD36∼
∼CD39) were isolated and purified from a LR-CD mixture, and their physicochemical properties including aqueous solubility, surface tension, specific rotation and acid-catalyzed hydrolysis rate were elucidated. The aqueous solubilities of CD36∼
∼CD39 were greater than those of α-, β-, γ-CD, CD9, CD10, CD14 and CD26. CD36∼
∼CD39 did not show any surface activity. The acid-catalyzed hydrolysis of CD36∼
∼CD39 was a little faster than that of other LR-CDs (CD9∼
∼CD35). There was no marked difference in specific rotation or the acid-catalyzed hydrolysis rate among CD36∼
∼CD39. Furthermore, we compared these findings with the physicochemical properties of α-, β-, γ-CD and other LR-CDs (CD9∼
∼CD35). 相似文献
233.
Sameh Ahmed Naoya Kishikawa Kaname Ohyama Toshihide Maki Hiromasa Kurosaki Kenichiro Nakashima Naotaka Kuroda 《Journal of chromatography. A》2009,1216(18):3977-3984
Quinones are a class of compounds of substantial toxicological and pharmacological interest. An ultrasensitive and highly selective chemiluminescence (CL) method was newly developed for the determination of quinones based on the utility of photochemically initiated luminol CL. The method involved ultraviolet (UV) irradiation of quinones to generate reactive oxygen species (ROS) through the unique photosensitization reaction accompanied with the photolytical generation of 3,6-dihydroxyphthalic acid (DHPA) from quinones. The photoproducts were detected by luminol CL reaction. Interestingly, it was noticed that DHPA had enhancement effect for the luminol CL. The generation of the enhancer (DHPA) in association with the oxidant (ROS) in the photochemical reaction greatly increases the sensitivity and selectivity of the proposed luminol CL method. In order to elucidate the type of ROS produced by the photosensitizaion reaction in relation to the proposed CL reaction, we investigated the quenching effect of selective ROS scavengers in the luminol CL. Although several ROS were generated, superoxide anion was the most effective ROS for the generated CL. Moreover, the enhancement mechanism of DHPA for luminol CL was confirmed. The enhancement was found to be through the formation of stabilized semiquinone anion radical that provided long-lived CL. The generation of the semiquinone radical was confirmed by electron spin resonance technique. Furthermore, we developed an HPLC method with on-line photochemical reaction followed by the proposed CL detection for the determination of four quinones. A luminol analogue, L-012, was used for its high sensitivity. The detection limits for quinones obtained with the proposed method (S/N = 3) were in the range 1.5–24 fmol that were 10–1000 times more sensitive compared with the previous methods. Finally, the developed HPLC-CL system was successfully applied for the determination of quinones in airborne particulate samples collected at Nagasaki city. 相似文献
234.
Satoshi Kubota Hiromasa Nishikiori Nobuaki Tanaka Morinobu Endo Tsuneo Fujii 《Journal of photochemistry and photobiology. A, Chemistry》2009,206(2-3):148-154
Pyrene crystals were grown on carbon nanofibers (CNFs) by dispersing pyrene polycrystals and CNFs in water during ultrasonic irradiation, and they were characterized by scanning electron microscopy, X-ray diffractometry (XRD) and spectroscopy. The XRD measurements indicated that the orientation and size of the pyrene crystals on the CNF aggregates were different from that of the added pyrene polycrystals. Based on the spectroscopic properties of the pyrene crystals on the CNFs, the pyrene crystals on the CNF aggregates and on the individual CNFs were determined to be polycrystals and single crystals, respectively. These results indicate that pyrene crystals are produced on the CNFs by recrystallization of the added pyrene polycrystals and their crystal states depend on the aggregation state of the CNFs. 相似文献
235.
Rudi Agus Setiawan Hiromasa Nishikiori Nobuaki Tanaka Tsuneo Fujii 《Photochemistry and photobiology》2014,90(5):1004-1011
The titania and dye‐dispersing titania electrodes were prepared by a nitric acid‐catalyzed sol‐gel process. The dye‐dispersing titania contains the dye molecules dispersed on the surface of the individual nanosized titania particles. The photo‐cyclic voltammetry (Photo‐CV) and photoelectric measurements of the dye‐dispersing titania electrodes were conducted to clarify the factors changing the conduction band edge of the titania and the open‐circuit voltage (Voc) of the electrodes. The remaining nitrate ions caused a negative shift of conduction band edge of the titania of the dye‐dispersing titania. The conduction band edge of the titania was shifted in a negative direction in the electrode containing a greater amount of the dye. These results are due to the adsorption of nitrate ions and the dye‐titania complex formation on the titania particle surface. The effect of the dye‐titania complex formation on the shift in the titania conduction band edge was greater than that of the adsorption of nitrate ions due to strong interaction between the dye and titania through the carboxylate and quinone‐like groups of the dye. The shift in the titania conduction band edge corresponded to the change in the Voc value. 相似文献
236.
Ryo Sekiya Kazumasa Hosoya Shin‐ichi Nishikiori 《Acta Crystallographica. Section C, Structural Chemistry》2006,62(5):i32-i34
The title compound, poly[diamminehexa‐μ‐cyano‐dicopper(I)copper(II)mercury(II)], [Cu3Hg(CN)6(NH3)2]n, has a novel threefold‐interpenetrating structure of three‐dimensional frameworks. This three‐dimensional framework consists of two‐dimensional network Cu3(CN)4(NH3)2 complexes and rod‐like Hg(CN)2 complexes. The two‐dimensional network complex contains trigonal–planar CuI (site symmetry m) and octahedral CuII (site symmetry 2/m) in a 2:1 ratio. Two types of cyanide group form bridges between three coordination sites of CuI and two equatorial sites of CuII to form a two‐dimensional structure with large hexagonal windows. One type of CN− group is disordered across a center of inversion, while the other resides on the mirror plane. Two NH3 molecules (site symmetry 2) are located in the hexagonal windows and coordinate to the remaining equatorial sites of CuII. Both N atoms of the rod‐like Hg(CN)2 group (Hg site symmetry 2/m and CN− site symmetry m) coordinate to the axial sites of CuII. This linkage completes the three‐dimensional framework and penetrates two hexagonal windows of two two‐dimensional network complexes to form the threefold‐interpenetrating structure. 相似文献
237.
Rika Nishikiori Shotaro Morimoto Yoshihisa Fujiwara Yoshifumi Tanimoto 《Applied magnetic resonance》2011,41(2-4):221-227
The magnetic field effect (0?C0.47?T) on cathodic potential oscillation of a zinc cathode in an alkaline solution was studied. By applying a magnetic field, the oscillation interval increased. The oscillation was quenched at 0.47?T. In situ bore-scope observation of the cathode during electrolysis in magnetic fields revealed that the solution convection induced by the Lorentz force causes the observed effect. 相似文献
238.