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71.
We examine the discrete free boundaries arising from a finiteelement discretization of a variational inequality. We giveL error bounds for the Hausdorff distance of the discrete andtrue free boundary, as well as for the normals. The theoreticalresults are confirmed by numerical experiments in two and threedimensions. 相似文献
72.
It is common for peristaltic micropumps to have large compression ratios. In the limit, the chamber of the pump is completely blocked by the membrane to prevent back flow. Different from this kind of pump, a micropump with small compression ratios is proposed in this study. With small oscillation amplitudes the membrane of the pump can reciprocate at high frequencies to improve its pumping flow. Both the multidimensional method and the lumped‐element method are employed for analysis. For this kind of peristaltic micropump the working fluid is allowed to flow freely in the forward and backward directions. Therefore, the operating sequences for the high‐compression ratio type of pumps are not appropriate. It is shown that the theoretical net flow rate is zero for the four‐phase and six‐phase modes of sequence and becomes negative for the three‐phase mode unless regulators, such as the nozzle/diffusers, are incorporated to rectify the flow. However, this pump becomes very attractive by reversing the operating sequence of the three‐phase mode because positive net flow is yielded. It is seen that with the reversed three‐phase mode and the nozzle/diffuser as connecting channels, the pumping effectiveness is greatly enhanced. The pumps with both two chambers and three chambers are under consideration in the study. Copyright ©2011 John Wiley & Sons, Ltd. 相似文献
73.
Inside Cover: Ketimido Metallophthalocyanines: An Approach to Phthalocyanine‐Supported Mononuclear High‐Valent Ruthenium Complexes (Chem. Asian J. 1/2014) 下载免费PDF全文
74.
Wai K. Tso 《Experimental Mechanics》1966,6(7):357-361
An account of certain subharmonic vibrations as observed during a resonant testing of thin-walled beams of monosymmetric open section for coupled torsional and bending vibrations is presented. The phenomenon can be described in terms of the vibrational modes of the beam. When the beam is excited at the resonant frequency of a higher mode, there is a tendency for the lowest mode to be excited, resulting in a high-order subharmonic oscillation. It is found that when such phenomenon occurs, the high-mode frequency is a multiple or near multiple of the fundamental frequency of the beam. Under such condition, the response of the beam consists of a superposition of the response of the high mode (harmonic response) and that of the fundamental mode (subharmonic response). The amplitude of the subharmonic motion is generally much larger than that of the harmonic response. 相似文献
75.
Fang-Chyou Chiu Qiang Fu Mark Leland Stephen Z. D. Cheng Eric T. Hsieh Chung C. Tso 《Journal of Macromolecular Science: Physics》2013,52(5):553-567
Melt-crystallization behavior and single-crystal morphology of two low molecular weight (LMW) linear polyethylene (PE) fractions of 3900 and 5800 have been investigated. Linear growth rates along the b axis (G b) of these fractions were measured via polarized light microscopy (PLM). The two fractions show a growth rate change at an undercooling of 17°C (at 117°C and 120°C, respectively, for these two fractions), which may be identified as the regime I/II transition. This transition does not correspond to a single-crystal morphological change from a truncated lozenge with curved (200) and (110) planes to a lenticular crystal as proposed previously. However, this morphological change can be observed at a temperature higher than the regime transition (at 122°C and 124°C), at which the cusps of the G b data can be observed for these two fractions. Based on our morphological study via PLM, transmission electron microscopy, electron diffraction, small-angle x-ray scattering (SAXS), and differential scanning calorimetry (DSC) experiments, it is found that within a 2°C temperature region, the G b change is accompanied by a sharp long period increase and a drastic change in single-crystal morphology from a truncated lozenge with curved (200) and (110) planes to a lenticular-shape crystal. The morphological change may result from a sudden increase in the G b coupled with a smaller change in the growth rate along the a axis with undercooling. This implies that, within this temperature region (2°C), the crystals may undergo substantial changes in the geometry of the (110) and (200) crystal growth fronts and chain folding behavior. 相似文献
76.
Fourier‐transform infrared spectroscopy has been employed to investigate the adsorption and photo‐oxidation of CH4 over powdered TiO2. The interaction between the CH4 and TiO2 surface is weak. It is found that no CH4 molecules are adsorbed on the surface at 35 °C in a vacuum. Under UV irradiation, CH4 decomposes to form CO(a), CO2(g), H20(a), and HCOO(a) in the presence of O2. The photoreaction rate is retarded and only small amounts of CO(a) and HCOO(a) are formed in the absence of O2. It is observed that the oxygen atoms of O2 are incorporated into these photoproducts as 18O2 is used. The major 18O‐containing products are C18O(a), C18O2(g), H2 18O(a), HC16O18O(a), and HC18O18O(a) after 180 min UV irradiation. However, the extent of 18O incorporating into the adsorbed formate is dependent on UV irradiation time. In the early stage of UV irradiation HC16O16O(a) is the major formate form indicating the involvement of TiO2 lattice oxygens for its formation, but HC18O18O(a) becomes the major one after 180 min indicating the involvement of 18O2. Formate on TiO2 further photodecomposes to CO2(g), but not to CO(a). CO(a) formation is directly from CH4 photodecomposition with the participation of TiO2 lattice oxygens and O2. 相似文献
77.
Eric T. Hsieh Chung C. Tso Jim D. Byers Timothy W. Johnson Qiang Fu Stephen Z. D. Cheng 《Journal of Macromolecular Science: Physics》2013,52(5):615-628
Direct proof of intermolecular compositional inhomogeneity of a metallocene polyethylene copolymer has been obtained using a cross-fractionation (CF) technique. The ethylene/1-hexene copolymer sample was synthesized using a Zr-based homogeneous metallocene catalyst. A solvent gradient fractionation (SGF) applied to the whole polymer material has produced nearly monodispersed molecular weight distribution fractions. The component molecules of a representative SGF fraction are then further sorted out, using a temperature gradient fractionation technique, according to their short-chain branching (SCB) differences. Molecular characterization of the resulting CF fractions reveals the presence of significant intermolecular SCB content differences among the components of the sample material. 相似文献
78.
79.
80.
Keita Fuchise Ryohei Kakuchi Sung‐Tso Lin Ryosuke Sakai Shin‐Ichiro Sato Toshifumi Satoh Wen‐Chang Chen Toyoji Kakuchi 《Journal of polymer science. Part A, Polymer chemistry》2009,47(22):6259-6268
The precise synthesis and variation in the thermoresponsive property based on the supramolecular assembly of a novel urea end‐functionalized poly(N‐isopropylacrylamide) (PNIPAM) were studied. A series of PNIPAMs with different diphenylurea groups at the chain end (X? Ph? NH? CO? NH? Ph? trz? PNIPAM: X = H, OCH3, CH3, NO2, Cl, and CF3) were synthesized by using a combination of the atom transfer radical polymerization and the copper(I)‐catalyzed azide‐alkyne cycloaddition. The cloud point of the obtained polymers depended on the hydrogen‐bonding ability of the introduced urea group. The 1H NMR measurement suggested that the obtained PNIPAM assembled in water via the intermolecular hydrogen bonding by the terminal urea group. From the dynamic light scattering and transmission electron microscopy measurements, the aggregated nanoparticles of the resulting polymer were directly observed in water at a temperature below its cloud point. The hydrogen‐bonding property of the chain end urea group was concluded to be involved in the aggregation of the PNIPAM in water, leading to the variation in its cloud point. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 6259–6268, 2009 相似文献