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排序方式: 共有400条查询结果,搜索用时 15 毫秒
101.
A method for the isolation of six isoflavones (genistein, genistin, daidzein, daidzin, glycitein and glycitin) with high purity from Semen sojae praeparatum, a famous traditional Chinese medicine, by preparative HPLC is described. 相似文献
102.
103.
Voegel LP 《Science (New York, N.Y.)》2002,295(5555):625
104.
105.
Doh YJ van Dam JA Roest AL Bakkers EP Kouwenhoven LP De Franceschi S 《Science (New York, N.Y.)》2005,309(5732):272-275
Nanoscale superconductor/semiconductor hybrid devices are assembled from indium arsenide semiconductor nanowires individually contacted by aluminum-based superconductor electrodes. Below 1 kelvin, the high transparency of the contacts gives rise to proximity-induced superconductivity. The nanowires form superconducting weak links operating as mesoscopic Josephson junctions with electrically tunable coupling. The supercurrent can be switched on/off by a gate voltage acting on the electron density in the nanowire. A variation in gate voltage induces universal fluctuations in the normal-state conductance, which are clearly correlated to critical current fluctuations. The alternating-current Josephson effect gives rise to Shapiro steps in the voltage-current characteristic under microwave irradiation. 相似文献
106.
In the burrowing cockroach Arenivaga, two giant interneurons in each connective of the ventral nerve cord provide gravity orientation information. The interneurons receive input from plumb bob-like equilibrium receptors on the ventral surface of the cerci. Ouir results support the theory that the cerci of cockroaches are specialized equilibrium organs. 相似文献
107.
Zhu YM Shi HF Gao YR Xin JQ Liu NH Xiang WH Ren XG Feng JK Zhao LP Xue F 《Veterinary microbiology》2011,149(3-4):446-451
Bovine parainfluenza virus type 3 (BPIV3) is one of the most important of the known viral respiratory pathogens of both young and adult cattle. However BPIV3 has not been detected or isolated in China prior to this study. In 2008, four BPIV3 strains were isolated with MDBK cells from cattle in China and characterized by RT-PCR, nucleotide sequence analysis, transmission electron microscope observation, hemadsorption and hemagglutination tests. Nucleotide phylogenetic analysis of partial hemagglutinin-neuraminidase (HN) gene for four isolates and the complete genome for the SD0835 isolate implicated that the four Chinese BPIV3 strains were distinct from the previously reported genotype A (BPIV3a) and genotype B (BPIV3b) and might be a potentially new genotype, which was tentatively classified as genotype C (BPIV3c). This is the first study to report the isolation and genetic characterization of BPIV3 from cattle in China. 相似文献
108.
Mourik V Zuo K Frolov SM Plissard SR Bakkers EP Kouwenhoven LP 《Science (New York, N.Y.)》2012,336(6084):1003-1007
Majorana fermions are particles identical to their own antiparticles. They have been theoretically predicted to exist in topological superconductors. Here, we report electrical measurements on indium antimonide nanowires contacted with one normal (gold) and one superconducting (niobium titanium nitride) electrode. Gate voltages vary electron density and define a tunnel barrier between normal and superconducting contacts. In the presence of magnetic fields on the order of 100 millitesla, we observe bound, midgap states at zero bias voltage. These bound states remain fixed to zero bias, even when magnetic fields and gate voltages are changed over considerable ranges. Our observations support the hypothesis of Majorana fermions in nanowires coupled to superconductors. 相似文献
109.
Chemical investigation on the seeds of Vitex negundo has afforded a new furan-containing sesquiterpenoid, negunfurol (1), a new norlabdane-type diterpenoid, negundoal (2), and two new norursane-type triterpenoids, negundonorins A (3) and B (4), together with two know compounds, 3-formyl-4,5-dimethyl-8-oxo-5H-6,7-dihydronaphtho[2,3-b]furan (5) and 3-epi-corosolic acid (6). Their structures and configurations were elucidated by detailed spectroscopic analyses on the basis of NMR, IR, and MS data. Compound 3 was strongly cytotoxic against ZR-75-30 cell line with IC50 value of 0.56 ± 0.19 μg/mL, whereas compound 1 was most active against HL-60 cell line with IC50 value of 0.94 ± 0.26 μg/mL. 相似文献
110.
Costa JF Kiperstok AC David JP David JM Giulietti AM de Queiroz LP dos Santos RR Soares MB 《Fitoterapia》2007,78(7-8):510-514
Ethyl acetate and chloroform extracts from aerial parts of Portulaca werdermannii and P. hirsutissima were tested in lymphoproliferation assays and axenic cultures of Leishmania amazonensis and Trypanosoma cruzi. Both extracts of P. werdermannii and P. hirsutissima had a potent inhibitory activity on lymphocyte proliferation. On the contrary, only the chloroformic extract of both plants inhibited L. amazonensis growth, without effect on T. cruzi cultures. These results indicate these Portulaca species as potential sources of new active molecules for the treatment of leishmaniasis and immune-mediated pathologies. 相似文献