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排序方式: 共有1317条查询结果,搜索用时 46 毫秒
91.
92.
RNA complementary to a herpesvirus alpha gene mRNA is prominent in latently infected neurons 总被引:107,自引:0,他引:107
J G Stevens E K Wagner G B Devi-Rao M L Cook L T Feldman 《Science (New York, N.Y.)》1987,235(4792):1056-1059
93.
Genetics and phenogenetics of mitochondria 总被引:6,自引:0,他引:6
R P Wagner 《Science (New York, N.Y.)》1969,163(871):1026-1031
94.
The Vinca alkaloids vinblastine sulfate and vincrystine sulfate, which are mitotic poisons, inhibit RNA synthesis in human (HEp-2) cells cultured in vitro. Analyses of RNA synthesis by cells treated with these drugs by acrylamide gel electrophoresis show that 28s rRNA and to a lesser extent 18s rRNA are preferentially inhibited. The synthesis of tRNA is affected much less than that of rRNA. The present experiments suggest that the drugs inhibit both the synthesis and processing of the nucleolar RNA precursors of rRNA. An explanation is also given for previous reports that these alkaloids preferentially inhibit the synthesis of tRNA in animal cells in vitro. 相似文献
95.
96.
Tyler GL Eshleman VR Fjeldbo G Howard HT Peterson AM 《Science (New York, N.Y.)》1967,157(3785):193-195
Continuous-wave signals transmitted from Lunar Orbiter I have been received on Earth after they have been reflected from the surface of the moon. The frequency spectrum of the reflected signals is used to locate discrete, heterogeneous, scattering centers on the lunar surface. The scattering centers are probably distinguished from the surrounding terrain by a higher surface reflectivity. Continuous-wave bistatic radar could provide an important new method for the study and mapping of planetary surfaces. 相似文献
97.
Horowitz HS McLain SJ Sleight AW Druliner JD Gai PL Vankavelaar MJ Wagner JL Biggs BD Poon SJ 《Science (New York, N.Y.)》1989,243(4887):66-69
Evidence suggests that superconducting, orthorhombic YBa(2)Cu(3)O(6+x)+ (x greater, similar 0.5) is always produced by oxidation of the oxygen-deficient, tetragonal form (x less, similar 0.5) of this phase (commonly referred to as 123). A synthetic route whereby solution-derived, carbon-free precursors are decomposed at 650 degrees to 700 degrees C in inert atmosphere to yield tetragonal 123 is now available. Appropriate precursors include hydrated oxides derived from the hydrolysis of organometallic solutions and aqueous solution-derived hyponitrites. Subsequent oxidation of the tetragonal phase at 400 degrees C results in submicrometer particles of orthorhombic 123. Superconductivity (T(c) onset approximately 87 K) has been confirmed in these materials by both Meissner effect and specific-heat measurements. 相似文献
98.
The Australasian and Ivory Coast deep-sea microtektites have fission track ages of 0.71 and 1.09 million years, respectively. These ages are in good agreement with the ages of deposition of the microtektites determined from paleomagnetic data. Both the fission track ages and ages of deposition of the microtektites agree with the potassium/ argon and fission track ages of tektites from the respective tektite strewn fields. 相似文献
99.
The T cell coreceptors CD4 and CD8 both associate via their cytoplasmic tails with the N-terminus of the Src-family tyrosine kinase Lck. These interactions require zinc and are critical for T cell development and activation. We examined the folding and solution structures of ternary CD4-Lck-Zn2+ and CD8alpha-Lck-Zn2+ complexes. The coreceptor tails and the Lck N-terminus are unstructured in isolation but assemble in the presence of zinc to form compactly folded heterodimeric domains. The cofolded complexes have similar "zinc clasp" cores that are augmented by distinct structural elements. A dileucine motif required for clathrin-mediated endocytosis of CD4 is masked by Lck. 相似文献
100.
A sporadic third layer in the ionosphere of Mars 总被引:1,自引:0,他引:1
Pätzold M Tellmann S Häusler B Hinson D Schaa R Tyler GL 《Science (New York, N.Y.)》2005,310(5749):837-839
The daytime martian ionosphere has been observed as a two-layer structure with electron densities that peak at altitudes between about 110 and 130 kilometers. The Mars Express Orbiter Radio Science Experiment on the European Mars Express spacecraft observed, in 10 out of 120 electron density profiles, a third ionospheric layer at altitude ranges of 65 to 110 kilometers, where electron densities, on average, peaked at 0.8 x 10(10) per cubic meter. Such a layer has been predicted to be permanent and continuous. Its origin has been attributed to ablation of meteors and charge exchange of magnesium and iron. Our observations imply that this layer is present sporadically and locally. 相似文献