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991.
H. Miura Y. Ushikubo K. Sugiyama T. Matsuda 《Reaction Kinetics and Catalysis Letters》1986,32(2):487-492
The exchange reaction of methane and deuterium was studied over a series of silica-supported Pt–Ru bimetallic catalysts, whose surface composition was determined by means of O2–CO titration. The stepwise exchange, giving CH3D as the main product, proceeded on each surface Pt atom. The multiple exchange, which formed CD4 directly, proceeded on an ensemble of several Ru atoms.
Pt–Ru, SiO2, O2–CO . , CH3D , Pt. , CD4, Ru.相似文献
992.
Adenosine diphosphatase (ADPase) activity was solubilized with a non-ionic detergent, Tween 20, from human umbilical vessels and purified to homogeneity by diethylaminoethyl-Sepharose CL-6B, adenosine 5'-monophosphate-Sepharose 4B, and concanavalin A-Sepharose chromatography. The apparent molecular mass was 75 kDa. The purified enzyme hydrolyzed pyrophosphate bonds of nucleoside di- and triphosphates in the presence of calcium ion. It was insensitive to the adenosine triphosphatase (ATPase) inhibitors, oligomycin and ouabain, and sensitive to sodium azide. Therefore, we concluded that the ADPase activity in human umbilical vessels does not derive from ADPase degrading only ADP but from ATP diphosphohydrolase (EC 3.6.1.5). The broad substrate specificity and the sensitivity to various inhibitors and calcium ion are common to ATP diphosphohydrolase from bovine aorta. However, there might exist some structural difference around the active site, because the antiserum raised in rabbit against the bovine aorta enzyme scarcely inhibited the human umbilical enzyme. 相似文献
993.
Satoshi Kamiguchi Ikuko Takahashi Kunihiko Kondo Sayoko Nagashima Hideki Kurokawa Hiroshi Miura Teiji Chihara 《Journal of Cluster Science》2007,18(4):845-853
When a molecular tungsten halide cluster on silica gel, (H3O)2[(W6Cl8)Cl6] · 6H2O/SiO2, was treated in a nitrogen stream at temperatures above 250 °C, Brønsted acidity appeared as the result of formation of a hydroxo ligand. The cluster catalyzed hydration of 1-hexyne to yield 2-hexanone. The catalytic activity increased with increasing temperature, the selectivity for 2-hexanone being 70% in the temperature range 250–400 °C. 1-Heptyne, 1-octyne, 1-nonyne, and phenylacetylene were also preferentially hydrated to produce the corresponding ketones. 2-Hexyne provided 2- and 3-hexanones in equal amounts, as happens with Brønsted acid catalysts. Halide clusters of niobium, molybdenum, and tantalum having the same octahedral metal framework were also active catalysts for the reaction. 相似文献
994.
Miura Y Momoki M Fuchikami T Teki Y Itoh K Mizutani H 《The Journal of organic chemistry》1996,61(13):4300-4308
The preparation, ESR spectra, isolation, and X-ray crystallographic structure of N-(arylthio)-2-tert-butyl-4,6-diarylphenylaminyls (1) and N-(arylthio)-4-tert-butyl-2,6-diarylphenylaminyls (2) are described. The aminyls are generated by PbO(2) oxidation of N-(arylthio)-2-tert-butyl-4,6-diarylanilines and N-(arylthio)-4-tert-butyl-2,6-diarylanilines. The kinetic ESR study shows that the aminyls are quite persistent, even in the presence of oxygen, and exist in the individual radical forms. Among the seventeen aminyls prepared, N-[(4-nitrophenyl)thio]-2-tert-butyl-4,6-diphenylphenylaminyl (1b), N-[(4-nitrophenyl)thio]-2-tert-butyl-4,6-bis(4-chlorophenyl)phenylaminyl (1f), N-[(4-nitrophenyl)thio]-4-tert-butyl-2,6-diphenylphenylaminyl (2b), N-[(4-nitrophenyl)thio]-4-tert-butyl-2,6-bis(4-chlorophenyl)phenylaminyl (2h), and N-[(3,5-dichlorophenyl)thio]-4-tert-butyl-2,6-bis(4-chlorophenyl)phenylaminyl (2j) are isolated as radical crystals. The crystallographic structures of 1b and 2b are determined by the X-ray crystallographic analyses. Aminyls 1 and 2 give similar ESR spectra consisting of 1:1:1 triplets with the a(N) values of 0.921-0.948 mT. Deuteration of the phenyl groups on the anilino benzene ring gives rise to a further splitting of the nitrogen 1:1:1 triplet by the anilino meta (0.126-0.138) and phenylthiyl ortho and para protons (0.077-0.096 mT). Upon recording at high gain, one of the partly deuterated aminyls gives satellite lines due to (33)S isotopes at natural abundance from which a(33)(S) is determined to be 0.51 mT. The ESR parameters for 1 and 2 are compared with those for structurally close N-(arylthio)-2,4,6-triarylphenylaminyl and N-(arylthio)-2,4,6-tri-tert-butylphenylaminyl. 相似文献
995.
Filtered backprojection method has been commonly used to reconstruct images in the field of the computed tomography (CT). However, in the emission CT such as positron and single photon CT, poor counting static which are caused by limited dosage to patients, limited counting rate capacity and limited efficiency of the imaging device, produce a statistical noise in the reconstructed image. The magnitude of the statistical noise and the spatial resolution were evaluated for various shapes of the filter used in the convolution integrals of the filtered back-projection procedure. The statistical noise was proportional to the inverse of the root of the total number of counts for any filters. The high-frequency-cut characteristic of the filter reduced the statistical noise, but increased the spatial resolution in the images. It was possible to optimize the shape of the filter for given total number of counts and required statistical noise and spatial resolution. 相似文献
996.
Toshio Tanaka Seizi Kurozumi Takeshi Toru Makiko Kobayashi Shuji Miura Sachio Ishimoto 《Tetrahedron》1977,33(10):1105-1112
Regiospecific α-acylation of β-alkenylated enolates generated by conjugate addition of lithium organocuprates to α,β-unsaturated ketones is described. Several new 7-oxoprostaglandin analogues, 7-oxoprostaglandin E1 (18), 11-deoxy-7-oxoprostaglandin E1 (23), and their 15-epi enantiomers 17 and 22, were synthesized by conjugate addition-acylation method. From optically active 4(R) -t - butyldimethylsiloxycyclopent - 2 - en - 1 - one (R-11), 7-oxoprostaglandin E1 (18) was synthesized. Determination of the absolute configuration of 11-deoxy-7-oxoprostaglandin E1 (23) and its 15-epi enantiomer (22) on the basis of CD study is described. Successful acylation of β-alkenylated lithium copper enolates with reactive acylating agents such as thiol esters and N-acyl imidazole as well as acyl halides is described. 相似文献
997.
Takenori Suzuki Yuichi Oki Masaharu Numajiri Taichi Miura Kenjiro Kondo Yasuo Ito Yutaka Shiomi 《Radiation Physics and Chemistry》1994,43(6):557-562
Positron annihilation lifetimes (PAL) have been measured for polythylenes (PEs) under differenr conditions of heat treatment. It is shown that the intensity, I3, of the long-lived component of positronium (Ps) shows hystereses between the heating and cooling processes due to aging effect. It is also shown that about half of Ps observed at low temperatures below the glass transition is inhibited after the sample is heat-treated above the melting point in the atmosphere containing oxygen. It is suggested that carbonyl groups (C=0) formed by thermal oxidation can inhibit Ps formation through trapping the precursors of Ps, e+ and/or e-. 相似文献
998.
Vasile Dinoiu Tsuyoshi Fukuhara Kaori Miura Norihiko Yoneda 《Journal of fluorine chemistry》2003,121(2):227-231
Anodic oxidation of some benzyl derivatives (phenylacetic acids esters) 1, and 1-tetralone 4, using ammonium fluorides or ammonium tetrafluoroborate as fluorine sources and supporting electrolytes and CH2Cl2 as solvent, allowed the introduction of a fluorine atom in the α position of an electron withdrawing group via carbocation (C), (ECBECN mechanism). 相似文献
999.
Yu Miura Takeshi Kaneko Kotaro Satoh Dr. Masami Kamigaito Prof. Hiroshi Jinnai Prof. Yoshio Okamoto Prof. 《化学:亚洲杂志》2007,2(5):662-672
Novel copolymers with controlled architectures can function as new building blocks for well‐defined nanostructures on the basis of microphase separation, unlike conventional ABA triblock copolymers. A series of well‐defined AxBAx‐type block–graft copolymers consisting of soft middle segments (dodecyl methacrylate (DMA)) and hard outer graft chains (styrene (St)) were synthesized by ruthenium‐catalyzed living radical block and graft polymerization. NMR spectroscopy and size‐exclusion chromatography combined with multiangle laser light scattering confirmed the well‐defined structure of the AxBAx block–graft copolymers with backbones and graft chains of controlled lengths. Transmission electron microscopy and transmission electron microtomography revealed a series of morphologies for the copolymers. Morphological changes were observed from PSt “honeycomb” cylinders to lamellae and poly(DMA) cylinders with increasing PSt‐graft content, whereby the phase diagram was shifted significantly to lower volume fractions of the larger‐number component (St) relative to those of the corresponding ABA triblock copolymers. More specifically, poly(DMA) cylinders were observed even before the St content reached 50 wt %. The AxBAx and ABA copolymers with 17–30 wt % of St exhibited characteristics of a thermoplastic elastomer with tensile strengths of 1–6 MPa and elongations at break of 70–300 %. These mechanical properties can be related well to the microphase structures of the AxBAx and ABA copolymers. 相似文献
1000.
Makoto Fujiwara Takashi Yamauchi Kenji Miura Masao Inoue 《Journal of the American Society for Mass Spectrometry》1992,3(8):847-852
Ion motion during frequency sweep excitation was computer simulated to study the effect of the direction of frequency sweep on the z motion of ions in a cylindrical Fourier transform ion cyclotron resonance (FT-ICR) cell. It is shown that the z motion is more forcefully excited by upsweep that by downsweep; thus at large amplitudes ions are more easily ejected to the trapping electrodes by upsweep and larger cyclotron orbits can be achieved by downsweep. This effect was confirmed by experiment and the results are favorably compared with the calculations. From these results it is concluded that downward sweeping is advantageous for ion detection and upward sweeping is preferable for ion ejection. The simulations clearly explain the effect of the direction of frequency sweep by visualizing the directions of the forces that ions experience immediately after the excitation of their cyclotron motion. It was demonstrated by experiment that the z ejection can be reduced by applying a phase-adjusted ac potential to the trapping electrodes. 相似文献