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81.
82.
《Journal of Physics and Chemistry of Solids》2014,75(4):550-557
We present a model to study the electrochemical effects of voids in oxide materials under equilibrium conditions and apply this model to uranium dioxide. Based on thermodynamic arguments, we claim that voids in uranium dioxide must contain oxygen gas at a pressure that we determine via a Kelvin equation in terms of temperature, void radius and the oxygen pressure of the outside gas reservoir in equilibrium with the oxide. The oxygen gas within a void gives rise to ionosorption and the formation of a layer of surface-charge on the void surface, which, in turn, induces an influence zone of space charge into the matrix surrounding the void. Since the space charge is carried in part by atomic defects, it is concluded that, as a part of the thermodynamic equilibrium of oxides containing voids, the off-stoichiometry around the void is different from its remote bulk value. As such, in a uranium dioxide solid with a void ensemble, the average off-stoichiometry level in the material differs from that of the void-free counterpart. The model is applied to isolated voids in off-stoichiometric uranium dioxide for a wide range of temperature and disorder state of the oxide. 相似文献
83.
《Journal of Physics and Chemistry of Solids》2014,75(4):523-527
Bulk polycrystalline Bi85Sb15−xGex (x=0, 0.5, 1, 1.5, 2) composites were prepared by mechanical alloying followed by pressureless sintering. The thermoelectric properties were studied in the temperature range of 77–300 K. The results indicate that increasing the Ge concentration causes the Seebeck coefficient to change sign from negative to positive. Moreover, it is found that the maximum value of the Seebeck coefficient can be precisely controlled with the Ge concentration. The maximum dimensionless figure of merit reaches 0.07 at 140 K. These results suggest that the preparation of p-type Bi–Sb alloys is possible by using the Ge-doping approach. 相似文献
84.
采用基于密度泛函理论(DFT)的第一性原理研究了合金团簇(PbSn)n (n=1~10)的稳定性及金属性。结果显示:同比例铅锡合金团簇具有与单质铅、锡团簇相同的幻数尺寸,但结构特点却与单质团簇不同,铅、锡原子间首先各自形成单质团簇,然后再结合成合金团簇,且表现出松散型与密堆积型的有机结合。另外,(PbSn)n (n=1~10)团簇构型在N=14处发生突变:类似于密堆积构型向层状转变,同时HOMO-LUMO能隙具有先增大后减小的趋势,并出现微弱的半导体向金属转变的行为,而且团簇原子总数为20的HOMO-LUMO能隙较相同尺寸单质团簇的还低,说明合金团簇具有比单质团簇更好的导电性。 相似文献
85.
《Solid State Sciences》2003,5(8):1177-1186
Three new one-dimensional coordination polymers have been prepared using Hg(II), Ag(I) and Zn(II) inorganic salts in combination with 2,5-bis(3-pyridyl)-1,3,4-oxadiazole (L6). The compounds were characterized by single crystal X-ray diffraction, IR spectroscopy, and elemental analysis. In the solid state, compounds 1 and 3 (1: monoclinic, P21/n, a=5.5373(3) Å, b=16.7839(9) Å, c=16.8120(9) Å, β=92.8610(10)°, V=1560.52(15) Å3, Z=4; 3: monoclinic, P21/n, a=7.2958(4) Å, b=11.7214(6) Å, c=16.3979(9) Å, β=101.1150(10)°, V=1375.99(13) Å3, Z=4) feature novel one-dimensional helical chain motif. Compound 2, however, (2: monoclinic, P21/c, a=5.5506(4) Å, b=16.5895(12) Å, c=16.6871(11) Å, β=95.424(2)°, V=1529.70(19) Å3, Z=4) exhibits one-dimensional zigzag chain motif, which result from the different conformations adopted by the L6 ligand and also the different metal coordination geometry. The luminescent properties of three new compounds were investigated in the solid state. 相似文献
86.
This paper presents direct simulations on the two-dimensional dielectrophoretic (DEP) motion of a pair of particles in a viscous fluid, interacting with a nearby planar wall, to further understand the DEP interaction among multiple particles and a wall. Results show that, under an external direct-current electric field parallel to the wall-fluid interface, the nearby wall has significant effects on the DEP motion of both particles including their revolution, alignment and aligned movement. Regardless of their particle conductivity, the wall being less (more) conductive than the fluid pushes (draws) both particles to move away from (toward) it. 相似文献
87.
A sonochemical method was used to synthesize nano-peanuts of a new lead(II) coordination 1D polymer, [Pb(qcnh)(NO3)2]n (1), where qcnh = 2-quinolincarbaldehyde nicotinohydrazide. The compound was characterized by scanning electron microscopy (SEM), elemental analysis, IR spectroscopy, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), X-ray powder diffraction (XRD), and single crystal X-ray analysis. The X-ray structure revealed that the Pb(II) atom is coordinated by one oxygen and three nitrogen atoms from two qcnh ligands and five oxygen atoms from three nitrate ligands in an 8 + 1 fashion with a PbN3O6 donor set. One of the PdN distances in the vicinity of the central atom is a bit longer (Pb1N1 = 2.939(4) Å), which shows the effect of the 6s2 lone electron pair localized within the valence shell of the lead(II) atom. PbO nanoparticles were obtained by thermolysis of 1 at 180 °C with oleic acid as a surfactant. The average diameter of the nanoparticles was estimated by XRD to be 28 nm. The morphology and size of the prepared PbO nanoparticles were further studied using SEM. 相似文献
88.
在辅助配体4,4′-二(1H-咪唑-1-基)-1,1′-双苯(4,4′-DIB)的帮助下,5-羟甲基-1.3-苯二甲酸(H2HIA)与Zn(BF4)2通过溶剂热或者水热反应构建出了两个具有sql网络的三维超分子配合物,即{[Zn2(HIA)2(4,4′-DIB)2]·xGuest}n (1, CCDC: 1989855 )和[Zn2(HIA)2(4,4′-DIB)2]n(2, CCDC: 1989856)。并对配合物的PXRD, IR, TGA和荧光等特性进行了表征。 相似文献
89.
Let ■ be a k-uniform hypergraph on n vertices with degree sequence △= d1≥…≥ dn =δ. In this paper, in terms of degree di , we give some upper bounds for the Z-spectral radius of the signless Laplacian tensor (Q(■)) of ■. Some examples are given to show the efficiency of these bounds. 相似文献
90.
Let X
1, X
2, ... be i.i.d. random variables. The sample range is R
n
= max {X
i
, 1 ≤ i ≤ n} − min {X
i
, 1 ≤ i ≤ n}. If for a non-degenerate distribution G and some sequences (α
k
), (β
k
) then we have
and
almost surely for any continuity point x of G and for any bounded Lipschitz function f: R → R.
相似文献