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81.
82.
83.
Treatment of [Ru3(CO)10(μ-dppm)] (4) [dppm = bis(diphenylphosphido)methane] with tetramethylthiourea at 66 °C gave the previously reported dihydrido triruthenium cluster [Ru3(μ-H)23-S)(CO)7(μ-dppm)] (5) and the new compounds [Ru33-S)2(CO)7(μ-dppm)] (6), [Ru33-S)(CO)73-CO)(μ-dppm)] (7) and [Ru33-S){η1-C(NMe2)2}(CO)63-CO)(μ-dppm)] (8) in 6%, 10%, 32% and 9% yields, respectively. Treatment of 4 with thiourea at the same temperature gave 5 and 7 in 30% and 10% yields, respectively. Compound 7 reacts further with tetramethylthiourea at 66 °C to yield 6 (30%) and a new compound [Ru33-S)21-C(NMe2)2}(CO)6(μ-dppm)] (9) (8%). Thermolysis of 8 in refluxing THF yields 7 in 55% yield. The reaction of 4 with selenium at 66 °C yields the new compounds [Ru33-Se)(CO)73-CO)(μ-dppm)] (10) and [Ru33-Se)(μ33-PhPCH2PPh(C6H4)}(CO)6(μ-CO)] (11) and the known compounds [Ru3(μ-H)23-Se)(CO)7(μ-dppm)] (12) and [Ru43-Se)4(CO)10(μ-dppm)] (13) in 29%, 5%, 2% and 5% yields, respectively. Treatment of 10 with tetramethylthiourea at 66 °C gives the mixed sulfur-selenium compounds [Ru33-S)(μ3-Se)(CO)7(μ-dppm)] (14) and [Ru33-S)(μ3-Se){η1-C(NMe2)2}(CO)6(μ-dppm)] (15) in 38% and 10% yields, respectively. The single-crystal XRD structures of 6, 7, 8, 10, 14 and 15 are reported.  相似文献   
84.
The complexing ability of the binary system trans-aconitic acid (H3L) with regard to Cd(II) and the crystal structures of the binary system Cd(II)–(H3L), [Cd3L2(H2O)6] n(1) and ternary systems of Cd(II)–(H3L)–Lewis base [Lewis base = 1,10-phenanthroline (2) and 2,2′-bipyridine (3)] have been determined. Compound 1 is a rare binodal four-connected three-dimensional (3D) metal-organic framework possessing a moganite (mog) topology. Compounds 2 and 3 represent infinite one-dimensional (1D) chains forming three-dimensional metal-supramolecular structures through H-bond and π–π stacking interactions. All compounds have been characterized by spectroscopic and thermogravimetric techniques.  相似文献   
85.
We report a facile and controllable method for the postfabrication texturing of the surface topography of Au nanoshells based on site-selective chemical etching of the polycrystalline Au nanoshell surface by a bifunctional alkanethiol molecule, cysteamine. This nanoscale surface texturing process systematically introduces dramatic changes to the plasmonic properties of the Au nanoshells. The modification of the plasmon resonant properties of nanoshells as a function of increased surface roughness was examined experimentally and modeled theoretically using three-dimensional finite difference time domain (FDTD) simulations.  相似文献   
86.
Experiments in which a thermal-energy beam of xenon Rydberg atoms is directed at near grazing incidence onto a flat Au(111) surface are described that provide new insight into charge transfer and electron tunneling during atom/surface interactions. Analysis of the data shows that for the present range of principal quantum number n, 13 < or = n < or = 20, ionization occurs at an atom/surface separation Z(i) = (4.5+/-0.9)n2a0, where n2a0 is the Bohr radius of the atom. This result is in good agreement with the value Z(i) approximately 3.8n2a0 predicted by ab initio hydrogenic theory.  相似文献   
87.
88.
Density functional calculations have been used to investigate oxygen atom transfer reactions from the biological oxygen atom donors trimethylamine N-oxide (Me(3)NO) and dimethyl sulfoxide (DMSO) to the molybdenum(IV) complexes [MoO(mnt)(2)](2-) and [Mo(OCH(3))(mnt)(2)](-) (mnt = maleonitrile-1,2-dithiolate), which may serve as models for mononuclear molybdenum enzymes of the DMSO reductase family. The reaction between [MoO(mnt)(2)](2-) and trimethylamine N-oxide was found to have an activation energy of 72 kJ/mol and proceed via a transition state (TS) with distorted octahedral geometry, where the Me(3)NO is bound through the oxygen to the molybdenum atom and the N-O bond is considerably weakened. The computational modeling of the reactions between dimethyl sulfoxide (DMSO) and [MoO(mnt)(2)](2-) or [Mo(OCH(3))(mnt)(2)](-) indicated that the former is energetically unfavorable while the latter was found to be favorable. The addition of a methyl group to [MoO(mnt)(2)](2-) to form the corresponding des-oxo complex not only lowers the relative energy of the products but also lowers the activation energy. In addition, the reaction with [Mo(OCH(3))(mnt)(2)](-) proceeds via a TS with trigonal prismatic geometry instead of the distorted octahedral TS geometry modeled for the reaction between [MoO(mnt)(2)](2-) and Me(3)NO.  相似文献   
89.
1(2)-Aryl-5-methylsulfonyltetrazoles react with ethylene glycol, di- and triethylene glycols, and tris(2-hydroxyethyl)amine in acetonitrile in the presence of sodium hydroxide to give tetrazole-containing ethers. The products can be used as polydentate ligands for biomimetic studies.  相似文献   
90.
In an attempt to prepare structural and functional models for the active site of the hydrolytic enzyme zinc phosphotriesterase, five new zinc complexes of the ligands 2,6-bis[N-(N-(carboxylmethyl)-N-((1-methylimidazol)methyl)amine)methyl]-4-methylphenolate (BCIMP) and the corresponding asymmetric ligand 2-(N-isopropyl-N-((1-methylimidazolyl)methyl)aminomethyl)-6-(N-carboxylmethyl-N-((1-methylimidazolyl)methyl)aminomethyl)-4-methylphenol (ICIMP) have been synthesized, viz. Na[Zn(2)(BCIMP)Ac(2)] (1), [Zn(2)(BCIMP)(Ph(2)Ac)] (2), [Zn(2)(ICIMP)Ac(2)] (3), [Zn(4)(ICIMP)(2)(Me(3)Ac)(2)][ClO(4)](2) (4), and [Zn(4)(ICIMP)(2)(Ph(2)Ac)(2)][ClO(4)](2) (5). The X-ray structure of complex 5 has been determined and reveals that the complex is a dimer of dimers in the solid state, which in solution dissociates to potent structural models. Studies using NMR show that only one carboxylate coligand bridges the dizinc units in the case of diphenyl acetate and pivalate, while the steric bulk of acetate is sufficiently small to permit the coordination of two acetates/dizinc unit. Functional studies involving the hydrolysis/transesterification of 2-hydroxypropyl p-nitrophenyl phosphate (HPNP) show that the complex with ICIMP (compound 5) has a significantly higher rate of catalysis than the BCIMP complex (compound 2). This is attributed to the vacant/labile coordination site that is available in the ICIMP complex but not the BCIMP complex.  相似文献   
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