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71.
Ana?Prieto Javier?Hernández Enrique?Herrero Juan?M.?FeliuEmail author 《Journal of Solid State Electrochemistry》2003,7(9):599-606
Oxygen reduction on well-defined single-crystal electrodes in different basic and neutral media has been studied using the impinging jet system. The results obtained with this system in 0.1 M NaOH are comparable to those reported in the literature for rotating disk electrodes, indicating that the impinging jet system behaves as a system in which the thickness of the diffusion layer is stationary. The activity of the Au(100) electrode is considerably higher than the rest of the basal planes in all media and yields water when E>–0.2 V and hydrogen peroxide for E<–0.2 V on the SHE scale. For Au(111) and Au(110) the activity of the electrode is much smaller and the final product is always hydrogen peroxide. The transition between both mechanisms for the Au(100) is, essentially, independent of the solution pH. In acid media the final product is always hydrogen peroxide for all the electrodes studied. The differences between the activities of the electrodes have been explained in the light of the different adsorption properties of the surfaces in relation to HO2
–. In the case of the Au(100) electrode, the existence of a negative charge density on the metal inhibits further reduction of HO2
–.Dedicated to Prof. Dr. Wolf Vielstich on the occasion of his 80th birthday in recognition of his numerous contributions to interfacial electrochemistry 相似文献
72.
E. Jeanneau N. Audebrand M. Le Floch B. Bureau D. Louër 《Journal of solid state chemistry》2003,170(2):330-338
A mixed cadmium-zirconium-sodium oxalate with an open architecture has been synthesized from precipitation methods at ambient pressure. It crystallizes in an hexagonal system, space group P6422 (no. 181), a=8.793(1)Å, c=24.530(1)Å, V=1642.5(3)Å3 and Z=3. The structure displays a [CdZr(C2O4)4]2− helicoidal framework. It is built from CdO8 and ZrO8 square-based antiprisms connected through bichelating oxalates and displays channels along different directions. The sodium counter-cations are located inside the voids of the structure together with water molecules. They exhibit a dynamic disorder which has been further investigated by 1H and 23Na solid-state NMR. The study pointed out two types of water molecules and sodium atoms, with a high mobility for one of each. The thermal decomposition has been studied in situ by temperature-dependent X-ray diffraction and thermogravimety. The final product is a mixture of cadmium oxide, zirconium oxide and amorphous sodium carbonate. 相似文献
73.
The high-temperature hexagonal forms of BaTa2O6 and Ba0.93Nb2.03O6 have P6/mmm symmetry with unit-cell parameters a=21.116(1) Å, c=3.9157(2) Å and a=21.0174(3) Å, c=3.9732(1) Å, respectively. Single crystal X-ray structure refinements for both phases are generally consistent with a previously proposed model, except for displacements of some Ba atoms from high-symmetry positions. The structures are based on a framework of corner- and edge-connected Nb/Ta-centred octahedra, with barium atoms occupying sites in four different types of [0 0 1] channels with hexagonal, triangular, rectangular and pentagonal cross-sections. The refinements showed that the non-stoichiometry in the niobate phase is due to barium atom vacancies in the pentagonal channels and to extra niobium atoms occupying interstitial sites with tri-capped trigonal prismatic coordination. The origin of the non-stoichiometry is attributed to minimisation of non-bonded Ba-Ba repulsions. The hexagonal structure is related to the structures of the low-temperature forms of BaNb2O6 and BaTa2O6, through a 30° rotation of the hexagonal rings of octahedra centred at the origin. 相似文献
74.
Neil J. Bullen Colin A. Kilner William Clegg John D. Kennedy 《Journal of organometallic chemistry》2005,690(11):2815-2828
Reaction of the ten-vertex [6-Ph-nido-6-CB9H11]− anion (1) with two-electron donor ligands L, where L is SMe2, NH2Ph, NC5H5, NC5H4-para-CH2Ph, NC5H4-para-Ph or NC9H7 (where NC9H7 is quinoline) in the presence of {FeCl3(OH2)6} gives the six neutral arachno ten-vertex monocarbaboranes [6-Ph-9-L-arachno-6-CB9H12], compounds 2, 3, 4, 7, 9 and 11, respectively, isolatable in yields of up to 63%. On prolonged treatment with {FeCl3(OH2)6} oxidative cluster closure of the four compounds 4, 7, 9 and 11 that have pyridine-type ligands gives the neutral closo ten-vertex monocarbaboranes [1-Ph-6-L-closo-1-CB9H8], compounds 6, 8, 10 and 12, respectively, in yields of 49-92%. All new species 2, 3, 4, 6, 7, 8, 9, 10, 11 and 12 are characterised by single-crystal X-ray diffraction analysis and NMR spectroscopy. [This paper is an annotated exposition of parts of an oral presentation at the Third Pan-European Meeting of Boron Chemists, EUROBORON-3, Pruhonice, The Czech Republic, September 2004, of which the proceedings constitute this volume of Journal of Organometallic Chemistry.] 相似文献
75.
Frank Hipler 《Journal of Molecular Structure》2003,658(3):179-191
The synthesis and crystal structures of three mercapto functionalised 1,3,4-thiadiazoles and the crystal structure of 2-mercapto-5-methyl-1,3,4-thiadiazole are described. In the solid state, 2-mercapto-5-methyl-1,3,4-thiadiazole 1 forms a thioamide tautomer as shown by FTIR and Raman spectroscopy as well as X-ray crystallography and as theoretically predicted. The molecules are connected to form chains via N-H?S hydrogen bonds with N?S=328.3 pm. Bis(2-methyl-1,3,4-thiadiazolyl)-5,5′-disulfide 2, the disulfide of 1, as well as 2-(tert-butyldithio)-5-methyl-1,3,4-thiadiazole 3 and 2,5-bis(tert-butyldithio)-1,3,4-thiadiazole 4 have been synthesised and characterised by vibrational spectroscopy and X-ray diffraction. 相似文献
76.
用X射线衍射法测定了由η~5-MeO_2CC_5H_4)(CO)_3MoNa和[(η~5-MeO_2CC_5H_4)(CO)_2W]Fe-(CO)_3Co(Co)_3(μ_3-S)的等瓣置换反应所生成的手性簇合物──[(η~5-MeO_2CC_5H_4)(CO)_2Mo]-[(η~5-MeO_2CC_5H_4)(CO)_2W]Fe(CO)_3(μ_3-S)的分子结构及晶体结构。晶体属P1空间群,晶胞参数α=0.87162(5)nm,b=0.76218(4)nm,c=1.87111(8)nm;α=94.164(4)°,β=97.979(2)°,γ=99.108(2)°,Z=2,μ=5.9cm~(-1)。最终的一致性因子R=0.036,Rw=0.037.该簇合物含MoWFeS四面体簇核,其中Mo、W原子以1:1的比例无序地分占了四面体的2个顶点. 相似文献
77.
Jürg Hulliger 《Angewandte Chemie (International ed. in English)》1994,33(2):143-162
Single-crystal materials, along with other forms of condensed matter (ceramics, polymers, liquid crystals, etc.) are fundamental to modern technology. The basic research and production of new materials with “tailored” solid-state physical properties therefore necessitate not only chemical synthesis but also the production of single crystals of a particular morphology (either bulk or thin layer crystals) and well-defined crystal defects (doping). In this review, an attempt is made to broaden the traditional synthetic concept of chemistry to the process of single-crystal synthesis. The methods of the resulting approach, which takes into account the specific properties of solid materials, are discussed and illustrated by experimental set-ups for the solution of a range of problems in chemical crystallization. Also included is recent work on the growing of single crystals of high-temperature superconductors, organic non-linear optical compounds, and proteins. 相似文献
78.
A new lithium zinc iodate, LiZnO(IO3), has been prepared by hydrothermal reactions at 200 °C. Single-crystal X-ray diffraction experiment revealed that the compound crystallizes in a noncentrosymmetric orthorhombic space group Ama2 with cell parameters: a = 6.3386(6) Å, b = 11.2613(11) Å, c = 4.6840(5) Å, Z = 4. In the structure, the basic building units are the distorted ZnO6 octahedron, LiO4 tetrahedron and the IO3 group. These groups are linked together to form a three-dimensional structure by sharing the oxygen atoms. The DSC measurement demonstrates that the compound is stable up to 490 °C. Powder second-harmonic generation (SHG) test shows that the SHG effect is about 2 × KH2PO4. 相似文献
79.
《Journal of Coordination Chemistry》2012,65(18):3245-3254
New zinc(II) and copper(II) complexes with a reduced Schiff-base ligand derived from D,L-selenomethionine and salicylaldehyde have been synthesized and characterized by elemental analysis, magnetic susceptibility, IR, and NMR measurements. The single-crystal X-ray structure of the Cu(II) complex reveals that this complex is a carboxylate-bridged dimer of dinuclear copper(II) subunits and all metal centers are five-coordinate with O4N donor sets in distorted square-pyramidal geometries. The Cu(II) complex consists of a 1-D coordination polymer. 相似文献
80.
《Journal of Coordination Chemistry》2012,65(18):3238-3253
A series of tri-, chlorodi-, and diorganotin(IV) derivatives of 4-(2-methoxyphenyl)piperazine-1-carbodithioate (L) {R?=?n-C4H9 (1), C6H11 (2), CH3 (3) and C6H5 (4)}, (n-C4H9)2SnClL (5) and R2SnL2 {R?=?n-C4H9 (6), C2H5 (7), CH3 (8)} have been synthesized by refluxing organotin(IV) chlorides with the ligand-salt in the appropriate molar ratio. Elemental analysis, Raman, IR, multinuclear NMR (1H, 13C and 119Sn), mass spectroscopic, and single-crystal X-ray crystallographic studies were undertaken to elucidate the structures of the new compounds both in solution and in the solid state. The X-ray diffraction work reveals supramolecular structures for 4 and 6, with distorted trigonal-bipyramidal and distorted octahedral geometries around Sn, respectively. The ligand and several of the new compounds are good antimicrobial agents. 相似文献