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51.
使用固-液相转移催化法合成了18种标题化合物,产率最高达93.4%,部分化合物结构由IR,^1HNMR及元素分析鉴定。使用氧指数,塑化效率、拉伸伸长率及差势分析研究基阻燃、增塑性能及热稳定性。 相似文献
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Recent experiments have observed bulk superconductivity in doped topological insulators. Here we ask whether vortex Majorana zero modes, previously predicted to occur when s-wave superconductivity is induced on the surface of topological insulators, survive in these doped systems with metallic normal states. Assuming inversion symmetry, we find that they do but only below a critical doping. The critical doping is tied to a topological phase transition of the vortex line, at which it supports gapless excitations along its length. The critical point depends only on the vortex orientation and a suitably defined SU(2) Berry phase of the normal state Fermi surface. By calculating this phase for available band structures we determine that superconducting p-doped Bi(2)Te(3), among others, supports vortex end Majorana modes. Surprisingly, superconductors derived from topologically trivial band structures can support Majorana modes too. 相似文献
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Using the nanometer depth sensitivity of differential confocal microscopy, we detect surface features of lateral dimensions smaller than the diffraction limit without fluorescence labeling. The lateral resolution of the topographic images is further enhanced by a maximum-likelihood estimation algorithm. Based on the comparison of signal and noise at high spatial frequency, we estimate the best lateral resolution of the enhanced images to be 0.15 lambda. In addition, on composite samples this technique can simultaneously display sub-diffraction-limit topographic features and reflectivity heterogeneity. 相似文献
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A two-stage intelligent search algorithm for the two-dimensional strip packing problem 总被引:2,自引:0,他引:2
Stephen C.H. LeungDefu Zhang Kwang Mong Sim 《European Journal of Operational Research》2011,215(1):57-69
This paper presents a two-stage intelligent search algorithm for a two-dimensional strip packing problem without guillotine constraint. In the first stage, a heuristic algorithm is proposed, which is based on a simple scoring rule that selects one rectangle from all rectangles to be packed, for a given space. In the second stage, a local search and a simulated annealing algorithm are combined to improve solutions of the problem. In particular, a multi-start strategy is designed to enhance the search capability of the simulated annealing algorithm. Extensive computational experiments on a wide range of benchmark problems from zero-waste to non-zero-waste instances are implemented. Computational results obtained in less than 60 seconds of computation time show that the proposed algorithm outperforms the supposedly excellent algorithms reported recently, on average. It performs particularly better for large instances. 相似文献
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G. M. Mong J. A. Campbell R. D. Orr S. A. Clauss K. L. Wahl F. V. Hoopes 《Journal of Radioanalytical and Nuclear Chemistry》1997,219(1):41-45
Instrumental neutron activation analysis (INAA) based on a nuclear reactor and proton induced X-ray emission (PIXE) based on a 2 Me V Van de Graaff accelerator were used to analyse different environmental samples including coal, sawdust, fly ash and landfill materials. These samples represent a large component of the solid waste being buried in the ground, and may be a potential source of toxicity which can have not only adverse effects on the soil and ground water, if diffused during leaching processes, but may also be transferred to humans through the food chain. Both techniques were employed to determine trace element concentrations in these matrices. The concentration of 30 elements were detemined, namely Na, Mg. Cl, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Br, Rb, Cd, Ba, La, Sm, Eu, Tb, Ho, Yb, Hf, Ta and Th. The detection limits in the various sample matrices were calculated and a comparison was made for those elements commonly detected by both techniques. 相似文献
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Let = 2cos (/5) and let []. Denote the normaliser ofG0() of the Hecke group G5 in PSL2() by N(G0()). Then N(G0())= G0(/h), where h is the largest divisor of 4 such that h2 divides. Further, N(G0())/G0() is either 1 (if h = 1), 2 x 2 (if h= 2) or 4 x 4 (if h = 4). 相似文献