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361.
Tomokazu Ito Akihiko Nakatsuka Hideki Maekawa Akira Yoshiasa Takamitsu Yamanaka 《无机化学与普通化学杂志》2000,626(1):42-49
The crystal structures of MgAl2–xGaxO4 (0 ≤ x ≤ 2) spinel solid solutions (x = 0.00, 0.38, 0.76, 0.96, 1.52, 2.00) were refined using 27Al MAS NMR measurements and single crystal X‐ray diffraction technique. Site preferences of cations were investigated. The inversion parameter (i) of MgAl2O4 (i = 0.206) is slightly larger than given in previous studies. It is considered that the difference of inversion parameter is caused by not only the difference of heat treatment time but also some influence of melting with a flux. The distribution of Ga3+ is little affected by a change of the temperature from 1473 K to 973 K. The degree of order‐disorder of Mg2+ or Al3+ between the fourfold‐ and sixfold‐coordinated sites is almost constant against Ga3+ content (x) in the solid solution. A compositional variable of the Ga/(Mg + Ga) ratio in the sixfold‐coordinated site has a constant value through the whole compositional range: the ratio is not influenced by the occupancy of Al3+. The occupancy of Al3+ is independent of the occupancy of Ga3+, though it depends on the occupancy of Mg2+ according to thermal history. The local bond lengths were estimated from the refined data of solid solutions. The local bond length between specific cation and oxygen corresponds with that expected from the effective ionic radii except local Al–O bond length in the fourfold‐coordinated site and local Mg–O bond length in the sixfold‐coordinated site. The local Al–O bond length in the fourfold‐coordinated site (1.92 Å) is about 0.15 Å longer than the expected bond length. This difference is induced by a difference in site symmetry of the fourfold‐coordinated site. The nature that Al3+ in spinel structure occupies mainly the sixfold‐coordinated site arises from the character of Al3+ itself. The local Mg–O bond length in the sixfold‐coordinated site (2.03 Å) is about 0.07 Å shorter than the expected one. Difference Fourier synthesis for MgGa2O4 shows a residual electron density peak of about 0.17 e/Å3 in height on the center of (Ga0.59 Mg0.41)–O bond. This peak indicates the covalent bonding nature of Ga–O bond on the sixfold‐coordinated site in the spinel structure. 相似文献
362.
Hiroyuki Maekawa Kosyu Nakamura Hiroto Kudo 《Journal of polymer science. Part A, Polymer chemistry》2024,62(9):1731-1741
In this paper, we aimed to develop ultrathin films of hyperbranched polybenzoxazole with a thickness in the range between 1 and 100 nm. They are expected to have great potential for various applications as functional materials due to their high thermal stability, good chemical resistance and mechanical strength. The synthesis of various hyperbranched poly(o-hydroxyamide)s as precursors of polybenzoxazole was examined by the polycondensation of 2,2-bis(3-amino-4-hydroxyphenyl)propane (AHP) and 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane (AHFP) with 1,3,5-benzenetricarbonyl trichloride (BCC), yielding the corresponding hyperbranched poly(o-hydroxyamide), poly(AHFPm-co-AHPn-co-BCC2.0), with Mn in the range between 12,870 and 22,210 in satisfactory yields. Poly(AHFP3.0-co-BCC2.0), poly(AHFP2.25-co-AHP0.75-co-BCC2.0), and poly(AHFP1.50-co-AHP1.50-co-BCC2.0) showed good solubility and film-forming ability, and ultrathin films 8.9–88.6 nm thick were prepared on silicon wafers. Heating of the ultrathin films of poly(AHFPm-co-AHPn-co-BCC2.0) on a hot plate at 350 °C for 1 h afforded the corresponding ultrathin films of hyperbranched polybenzoxazole, poly(AHFPm-cyclo-AHPn-cyclo-BCC2.0), with a thickness of 5.3–82.4 nm. Double-layer thin films consisting of resist materials on top of hyperbranched polybenzoxazole were also prepared. 相似文献
363.
Kunihisa Sugimoto Takayoshi Kuroda‐Sowa Sheng‐Gang Yan Masahiko Maekawa Mugumu Munakata 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(4):414-415
The title triangular tripalladium cluster, [Pd3Cl5(C18H15P)3]·C3H6O, (I), has a trigonal‐bipyramidal framework of Pd3(μ3‐Cl)2, with the two Cl atoms in apical positions. Each Pd atom in the framework has two additional coordination sites to establish square‐planar cis‐PdL2(μ3‐Cl)2 geometry. Three P atoms are located on the same side of the plane defined by the Pd3 triangle, which leads to a pseudo‐C3v symmetry for the core framework of Pd3(μ3‐Cl)2P3Cl3. The average Pd—Cl distance trans to PPh3 is 2.473 (8) Å, which is significantly longer than the average Pd—Cl distance of 2.294 (4) Å for those trans to terminal Cl, due to the strong trans effect of a P atom compared with a Cl atom. Compound (I) has 49 valence electrons and shows a rhombic electron‐spin resonance signal, indicating an S = ½ ground state. 相似文献
364.
365.
Wave trajectories of the ordinary mode as well as the extraordinary one injected obliquely into a magnetic field in high density toroidal plasmas, are studied theoretically. Both waves are finally converted into the electron Bernstein mode and cyclotron damped. 相似文献
366.
1H-F-Alkene-1-phosphonates, easily accessible from F-alkanoyl chlorides, underwent dephosphorylation on treatment with a catalytic amount of fluoride ion at O°C to room temperature to give terminal F-alkylacetylenes in good yields. 相似文献
367.
Imidoyl chlorides were successfully transformed into ketimines when treated with organotin compounds in the presence of palladium complex catalysts. 相似文献
368.
Dimethylphenylsilane was catalytically dehydrogenated and condensed in the presence of platinum complexes to give 1,1,2,2-tetramethyl-1,2-diphenyl-disilane. 相似文献
369.
The relation between two approaches to Rubin's model of brownian particles is clarified. The Fokker-Planck-like equation for the model is thereby derived. 相似文献
370.
Y. Noda H. Maekawa A. Kasuya 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2010,57(1):43-47
A 1-nm particle of CdSe showing a sharp photoabsorption peak at 350 nm has been selectively synthesized as a single species
in solution.
Solid NMR spectra of both atoms show a single narrow peak of large chemical shift anisotropy and asymmetry compared with the
essentially isotropic bulk CdSe.
This result indicates that this extremely small 1-nm particle has most of its atoms at the surface, and the atoms are deformed
from the sp3 configuration of the bulk fragment into an assembly consisting entirely of apexes of equivalent symmetry that are particularly
stable and preferentially grown.
This observed selective stability presents the possibility of growing 1-nm particles with an atomic monostructure in macroscopic
quantities. 相似文献