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51.
用高温熔融结合放电等离子烧结(SPS)方法合成了Sb掺杂的单相n型Ba8Ga16-xSbxGe30化合物,探索了Sb对Ga的取代对其热电性能的影响规律.研究结果表明随着Sb取代分数x的增加,Seebeck系数逐渐降低,Seebeck系数峰值对应的温度向低温方向偏移.电导率随着x的增加先增大后减小,当x=2时达到最大值.Sb取代Ga后对化合物的热性能有较大影响,其热导率和晶格热导率都有不同程度的降低.在所有n型Ba8Ga16-xSbxGe30化合物中,Ba8Ga14Sb2Ge30化合物的ZT值最大,在950 K左右其最大ZT值达1.1. 相似文献
52.
Calorimetric study of phase transitions in the thiourea 1,1,2,2-tetrachloroethane clathrate compound
Heat capacities of the thiourea clathrate compound of 1,1,2,2-tetrachloroethane, {(NH2)2CS}3(CHCl2)2, were measured at temperatures between 13 and 330 K. Two phase transitions were found. The enthalpy and entropy changes of the transition are 5940 J·mol–1 and 28.1 JK–1· mol–1 for the one occurring at 224 K and 2756 J·mol–1 and 11.3 JK–1·mol–1 for the other at 248 K. It is concluded from the transition entropy values that the guest molecules are orientionally disordered nearly to the same extent as in the neat liquid.Contribution No. 56 from the Microcalorimetry Research Center 相似文献
53.
The bonding of the O-O group in the dicobalt cation 1a [(NH3)6Co2(μ-O2)(μ-OH)(μ-NH2)]3+ was studied by DFT methods (ADF program) and the bridging O2 ligand was characterized as superoxide(O2−). In this complex, three bridging ligands connect the two cobalt atoms, forcing a cis conformation of the Co-O-O-Co atoms. A comparison was made with [(NH3)10Co2(μ-O2)]5+, 2a, where a trans arrangement is observed. Superoxide binds more strongly to the dicobalt(III) fragment in 2a than in 1a, both as a result of weaker Pauli repulsion and stronger covalent interaction. It was found that in 1a the electronic structure with one unpaired electron, where cobalt is formally Co(III), d6, and O2 carries one negative charge gives rise to the most stable structure, compared to possibilities with three and five unpaired electrons. The hydrogen bonds in the crystal were analyzed and the interactions between one water molecule or one nitrate ion studied in more detail. 相似文献
54.
Nicolás Yutronic Juan Merchán Paul Jara Guillermo Gonzalez María T. Garland 《Journal of inclusion phenomena and macrocyclic chemistry》2003,45(1-2):51-57
Thiourea reacts with 1-azabicyclo[2.2.2]octane (quinuclidine, Q) in methanol at room temperature leading to the formation of Q(3-thiourea).Single crystal X-ray diffraction analysis shows that the product has a rhombohedral structure, = = 90°, = 120°,a = b = 15.9371(2),c = 12.4248(2),which may bedescribed as a thiourea matrix defining hexagonal channels where the quinuclidine molecules are located. The 13C-cross polarisation magic angle spinning (CP-MAS) study indicates that the guest inside the cavities has high conformational, rotational and translational mobility at room temperature. Thermal studies indicate that the structural identity of the thiourea matrix remains after a partial loss of amine, and this result suggests that the thiourea-amine inclusion compound possesses an open host structure, or that a topotactic process is associated. 相似文献
55.
IR spectra of Mn(en)M(CN)4·2C6H6 (M=Cd or Hg), and IR and Raman spectra of Cd(en)M(CN)4·2C6H6 (M=Cd or Hg) clathrates are reported. The spectral features suggest that the first two compounds are similar in structure to the later two Td-type clathrates. 相似文献
56.
Michael Wiebcke Jrg Emmer Jürgen Felsche Dagobert Hoebbel Günter Engelhardt 《无机化学与普通化学杂志》1994,620(4):757-765
[TMPA]4[Si8O20] · 34 H2O ( 1 ) and [DDBO]4[Si8O20] · 32 H2O ( 2 ) have been prepared by crystallization from aqueous solutions of the respective quaternary alkylammonium hydroxide and SiO2. The crystal structures have been determined by single-crystal X-ray diffraction. 1 : Monoclinic, a = 16.056(2), b = 22.086(6), c = 22.701(2) Å, β = 90.57(1)° (T = 210 K), space group C2/c, Z = 4. 2 : Monoclinic, a = 14.828(9), b = 20.201(7), c = 15.519(5) Å, β = 124.13(4)° (T = 255 K), space group P21/c, Z = 2. The polyhydrates are structurally related host-guest compounds with three-dimensional host frameworks composed of oligomeric [Si8O20]8? anions and H2O molecules which are linked via hydrogen bonds. The silicate anions possess a cube-shaped double four-ring structure and a characteristic local environment formed by 24 H2O molecules and six cations (TMPA, [C8H20N2]2+, or DDBO, [C8H18N2]2+). The cations themselves reside as guest species in large, irregular, cage-like voids. Studies employing 29Si NMR spectroscopy and the trimethylsilylation method have revealed that the saturated aqueous solutions of 1 and 2 contain high proportions of double four-ring silicate anions. Such anions are also abundant species in the saturated solution of the heteronetwork clathrate [DMPI]6[Si8O18(OH)2] · 48.5 H2O ( 3 ) with 1,1-dimethylpiperidinium (DMPI, [C7H16N]+) guest cations. 相似文献
57.
J. Lipkowski D. V. Soldatov N. V. Kislykh N. V. Pervukhina Yu. A. Dyadin 《Journal of inclusion phenomena and macrocyclic chemistry》1994,17(4):305-316
A phase diagram of the [Zn(MePy)2(NCS)2]-MePy binary system has been studied by DTA and solubility methods. Two compounds melting incongruently (at 63 and 57°C) have been discovered in the system. They have been obtained as separate phases with crystals of different shape (needles and octahedra). Their composition has been determined by analytical methods and verified by X-ray structural analysis: [Zn(MePy)4(NCS)2]·0.67 MePy·xH2O, wherex depends on the synthesis conditions, and [Zn(MePy)4(NCS)2]·MePy, respectively.The preliminary X-ray study of the first compound (at –100°C) has shown it to be isostructural with the known clathrates of the common formula [M(MePy)4(NCS)2]·0.67MePy·xH2O, where M=Cu, Mn, Mg andx=0–0.33. The unit cell parameters are as follows:a=27.20(1),c=11.202(4) Å, space group
,Z=9.The X-ray study of [Zn(MePy)4(NCS)2]·MePy (at–50°C) has shown it to be analogous to the organic zeolite -phase with the guest MePy molecules located in the channels formed by molecular packing of the [Zn(MePy)4(NCS)2]host. The cell is tetragonal, the space groupI41/a,a=16.845(6),c=23.496(7) Å,V=6667(4) Å3,Z=8,D
calc=1.289 g cm–3,R=0.074. The zinc cation is surrounded by a slightly irregular octahedron of six nitrogen atoms of the MePy and NCS ligands. The crystallisation field of the host [Zn(MePy)4(NCS)2] complex in the temperature range concerned is absent in the phase diagram. It suggests contact stabilization of the [Zn(MePy)4(NCS)2] molecule by the guest in the clathrates.
Supplementary Data relevant to this paper have been deposited with the British Library at Boston Spa, Wetherby, West Yorkshire, U.K. as Supplementary Publication No. SUP 82166 (15 pages). 相似文献
58.
A. Yu. Manakov J. Lipkowski 《Journal of inclusion phenomena and macrocyclic chemistry》1997,29(1):41-55
Sorption equilibria have been studied in the systems solid -[Ni(NCS)2(4-MePy)4] clathrate – gaseous guest (benzene, furan,tetrahydrofuran, propane, CH2Cl2, CH2Br2, methanol). Analysis of theexperimental data shows that the solid–gas equilibrium in this systemcannot be regarded as simple physical sorption by a rigid host lattice. Itwas found that the isosteric heats of guest sorption decrease withincreasing guest uptake in all systems studied. The observed phenomena areinterpreted as the result of a guest to host influence and guest–guest repulsion. The molecular model of guest sorption by the-[Ni(NCS)2(4-MePy)4] host was suggested on the basis of combinedanalysis of sorption isotherms and the dependence of the isosteric heat ofsorption on clathrate composition. 相似文献
59.
60.