全文获取类型
收费全文 | 269篇 |
免费 | 5篇 |
专业分类
化学 | 140篇 |
数学 | 54篇 |
物理学 | 36篇 |
无线电 | 44篇 |
出版年
2023年 | 3篇 |
2021年 | 3篇 |
2020年 | 2篇 |
2019年 | 4篇 |
2018年 | 6篇 |
2017年 | 3篇 |
2016年 | 5篇 |
2015年 | 6篇 |
2014年 | 7篇 |
2013年 | 2篇 |
2012年 | 17篇 |
2011年 | 11篇 |
2010年 | 9篇 |
2009年 | 9篇 |
2008年 | 9篇 |
2007年 | 9篇 |
2006年 | 15篇 |
2005年 | 17篇 |
2004年 | 18篇 |
2003年 | 11篇 |
2002年 | 8篇 |
2001年 | 7篇 |
2000年 | 5篇 |
1999年 | 1篇 |
1998年 | 1篇 |
1997年 | 2篇 |
1996年 | 3篇 |
1995年 | 1篇 |
1994年 | 4篇 |
1993年 | 5篇 |
1992年 | 5篇 |
1991年 | 4篇 |
1990年 | 4篇 |
1989年 | 4篇 |
1988年 | 3篇 |
1987年 | 5篇 |
1986年 | 5篇 |
1985年 | 7篇 |
1984年 | 7篇 |
1983年 | 3篇 |
1982年 | 3篇 |
1981年 | 1篇 |
1979年 | 3篇 |
1977年 | 4篇 |
1976年 | 8篇 |
1974年 | 2篇 |
1973年 | 2篇 |
1972年 | 1篇 |
排序方式: 共有274条查询结果,搜索用时 15 毫秒
101.
102.
Setsuko Nakamura Takuto Yamawaki Katsuhiro Kusaka Takuhiro Otsuka Tomoji Ozeki 《Journal of Cluster Science》2006,17(2):245-256
Tetraphenylphosphonium salts of protonated tetradecavanadophosphate (PV14) anions, [(C6H5)4P]4H5PV14O42·5H2O (1) and [(C6H5)4P]2H7PV14O42·6H2O (2), have been synthesized and their crystal structures have been determined. Compound 1 crystallizes in triclinic, P1 with a=12.7866(1), b=15.5261(2), c=16.0730(3) ?, α=109.358(1), β=98.411(1), γ=110.040(1)°. Synchrotron radiation X-ray diffraction revealed that compound 2 crystallizes in monoclinic, P21/c with a=16.821(1), b=25.163(2), c=18.817(1) ?, β=109.992(2)°. In compound 1, the PV14 anions are linked into a one-dimensional chain structure by water molecules of crystallization. In compound 2, hydrogen bonds directly link PV14 anions into a zigzag chain, which are then woven into a three-dimensional network by hydrogen bonds bridged by water molecules.Dedicated to Professor Michael T. Pope on the occasion of his retirement, in recognition of his outstanding contributions to the polyoxometalate chemistry. 相似文献
103.
Toru Ozeki Seiichiro Hikime Iwao Watanabe Shigero Ikeda 《Journal of Electroanalytical Chemistry》1985,195(1):71-79
When two reactions take place at a given potential, other information is necessary, in addition to the relation between the applied potential and electric current, in order to evaluate the individual contribution of the reactions. Information about the heat evolved at the electrode during cyclic voltammetry enables the reaction components to be separated. It is concluded that the Cu/CuI redox system in chloride solution (0.1 < [Cl?] < 0.45 M) giving a simple CV curve, can be divided into two reactions: Cu/CuClad and Cu/CuCl?2. A similar overlap of the Ag/AgClad and Ag/AgCl?2 reactions is also observed for the Ag/AgI redox system in 7 < [Cl?] < 9 M solutions. 相似文献
104.
The uptake of fractionated [3H]heparin was investigated in rat parenchymal hepatocytes in primary culture. The initial uptake of fractionated [3H]heparin was found to be saturable with the maximum uptake velocity (Vmax) of 10.1 +/- 1.46 pmol/min/mg protein and the Michaelis constant (Km) of 284 +/- 47.9 nM. The effect of alpha-globulin, the major protein binding to fractionated [3H]heparin, on the saturable uptake profile of fractionated [3H]heparin was also investigated. The uptake clearance was reduced, depending on the concentration of fractionated [3H]heparin, by the addition of 1 mg/ml alpha-globulin. We assumed that fractionated 3H-heparin bound to alpha-globulin was not available for uptake and that the reduction in the uptake clearance was solely attributable to the saturable binding of fractionated [3H]heparin to alpha-globulin. The uptake clearance versus concentration profile was analyzed to obtain the dissociation constant (Kd) of 31.8 nM and the capacity (n) of 0.047 for the binding of fractionated [3H]heparin to alpha-globulin. The saturable binding of fractionated [3H]heparin to alpha-globulin was supported by in vitro binding experiments using gel chromatography, in which bound fractionated [3H]heparin decreased with the concentration of fractionated [3H]heparin in the presence of alpha-globulin. In conclusion, the present study demonstrated the saturable uptake of fractionated [3H]heparin by rat parenchymal hepatocytes and the saturable binding of fractionated [3H]heparin to alpha-globulin. The saturable uptake may suggest the involvement of a specific transport system such as receptor-mediated endocytosis. 相似文献
105.
Two new vanadoselenites, [SeV(3)O(11)](3)(-) and [Se(2)V(2)O(10)](2)(-), were synthesized by reacting SeO(2) with VO(3)(-). Single-crystal X-ray structural analyses of [(n-C(4)H(9))(4)N](3)[SeV(3)O(11)].0.5H(2)O [orthorhombic, space group P2(1)2(1)2, a = 22.328(5) A, b = 44.099(9) A, c = 12.287(3) A, Z = 8] and [[(C(6)H(5))(3)P](2)N](2)[Se(2)V(2)O(10)] [monoclinic, space group P2(1)/n, a = 12.2931(3) A, b = 13.5101(3) A, c = 20.9793(5) A, beta = 106.307(1) degrees, Z = 2] revealed that both anions are composed of Se(x)()V(4)(-)(x)()O(4) rings. The (51)V, (77)Se, and (17)O NMR spectra established that both [SeV(3)O(11)](3)(-) and [Se(2)V(2)O(10)](2)(-) anions maintain this ring structure in solution. 相似文献
106.
The crystal structure of [(CH3)4N]4Na2H[alpha-PW11O39].8H2O has been determined by using the Weissenberg camera at the BL04B2 beamline of SPring-8, revealing that it contains a disorder-free lacunary [alpha-PW11O39]7- anion with one sodium cation embedded into its lacuna that links the oxometalate building blocks into a one-dimensional chain, which is then woven into a three dimensional latticework by another Na+. 相似文献
107.
It has been proved by L. Sweet that the octahedron functional equation implies the cube functional equation in all dimensionsn1. In this note we give an elementary proof of this theorem. 相似文献
108.
Satoru Onaka Masanobu Yaguchi Tomoji Ozeki Tetsuya Sunahara Michito Shiotsuka Makoto Horibe Akifumi Iida Katsuya Inoue Katsuya Sako 《Journal of organometallic chemistry》2005,690(1):57-68
The effect of the carbon chain-length for Ph2P-R-PPh2 (R = -CHCH-, -CH2-CH2-, -CH2-CH2-CH2-, and -CH2-CH2-CH2- CH2-) and S-(CH2)n-pyridine ligand (n = 0 to 2) on the aurophilic interaction has been explored systematically. The effect of the N position in x-mercaptopyridine (x = 2 or 4) toward Au(I) center and/or the SR group was also investigated. X-ray structural study was made for 12 new derivatives. The Au-Au distances are below 3.0 Å for 2-S-pyridine derivatives with Ph2P-CHCH-PPh2 (t-dpen) and Ph2P-CH2-CH2-PPh2 (dppe) ligand and the pyridine N atoms come in close contact with the H atoms of these diphosphine carbon chains. A local coplanar conformation is formed between 2-S-pyridine and Au-P-CH groups for these derivatives. The carbon chain lengths are not too consequential on the induction of aurophilicity. Various infinite and/or dimer structures have been revealed from single crystal X-ray analysis for the present series of compounds. 相似文献
109.
Yamamoto Y Sawa S Funada Y Morimoto T Falkenström M Miyasaka H Shishido S Ozeki T Koike K Ishitani O 《Journal of the American Chemical Society》2008,130(44):14659-14674
Systematic synthesis routes have been developed for the linear-shaped rhenium(I) oligomers and polymers bridged with bidentate phosphorus ligands, [Re(N--N)(CO)3-PP-{Re(N--N)(CO)2-PP-}(n)Re(N--N)(CO)3](PF6)(n+2) (N--N = diimine, PP = bidentate phosphine, n = 0-18). These were isolated by size exclusion chromatography (SEC) and identified by (1)H NMR, IR, electrospray ionization Fourier transform mass spectrometry, analytical SEC, and elemental analysis. Crystal structures of [Re(bpy)(CO)3-Ph2PC[triple bond]CPPh2-Re(bpy)(CO)3](PF6)2, [Re(bpy)(CO)3-Ph2PC[triple bond]CPPh2-Re(bpy)(CO)2-Ph2PC[triple bond]CPPh2-Re(bpy)(CO)3](PF6)3 and [Re(bpy)(CO)3-Ph2PC2H4PPh2-{Re(bpy)(CO)2Ph2PC2H4PPh2-}(n)Re(bpy)(CO)3](PF6)(n+2) (bpy = 2,2'-bipyridine, n = 1, 2) were obtained, showing that they have interligand pi-pi interaction between the bpy ligand and the phenyl groups on the phosphorus ligand. All of the oligomers and polymers synthesized were emissive at room temperature in solution. For the dimers, broad emission was observed with a maximum at 523-545 nm, from the (3)MLCT excited-state of the tricarbonyl complex unit, [Re(N--N)(CO)3-PP-]. Emission from the longer oligomers and polymers with > or = 3 Re(I) units was observed at wavelengths 50-60 nm longer than those of the corresponding dimers. This fact and the emission decay results clearly show that energy transfer from the edge unit to the interior unit occurs with a rate constant of (0.9 x 10(8))-(2.5 x 10(8)) s(-1). The efficient energy transfer and the smaller exclusive volume of the longer Re(I) polymers indicated intermolecular aggregation for these polymers in an MeCN solution. 相似文献
110.