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排序方式: 共有857条查询结果,搜索用时 15 毫秒
851.
Berrettini W Bierut L Crowley TJ Cubells JF Frascella J Gelernter J Hewitt JK Kreek MJ Lachman H Leppert M Li MD Madden P Miner C Pollock JD Pomerleau O Rice JP Rutter JL Shurtleff D Swan GE Tischfield JA Tsuang M Uhl GR Vanyukov M Volkow ND Wanke K 《Science (New York, N.Y.)》2004,304(5676):1445-7; author reply 1445-7
852.
Duda TF Bingham JP Livett BG Kohn AJ Massilia GR Schultz JR Down J Sandall D Sweedler JV 《Science (New York, N.Y.)》2004,303(5660):955-7; author reply 955-7
853.
The primary mineral assemblages and initial (26)Al/(27)Al ratios of rare calcium-aluminum-rich inclusions (CAIs) from enstatite (E) chondrites are similar to those of CAIs from other chondrite classes. CAIs from all chondrite classes formed under oxidizing conditions that are much different from the reducing conditions under which the E chondrites formed. Either CAIs formed at an earlier, more oxidizing epoch in the region where E chondrites ultimately formed, or they formed at a different place in the solar nebula and were transported into the E chondrite formation region. 相似文献
854.
Heath GR 《Science (New York, N.Y.)》1979,205(4409):903-904
The size distributions of deep-sea manganese nodules are consistent with a simple model of uniform growth at a few millimeters per million years and with the same probability of burial for all nodules, regardless of size. The model suggests that most nodules spend 1 million years or less on the sea floor. 相似文献
855.
Matus-Cádiz MA Daskalchuk TE Verma B Puttick D Chibbar RN Gray GR Perron CE Tyler RT Hucl P 《Journal of agricultural and food chemistry》2008,56(5):1644-1653
Unacceptably dark bran color has prevented the white-kernelled variety Argent from meeting grain color marketing standards for hard white wheats (Triticum aestivum L.). The objective of this research was to identify phenolic compounds that negatively affect bran color in white wheat using Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) and vanillin-HCl and NaOH staining methods. In mature bran, FT-ICR-MS detected derivatives of the flavonol quercetin in varieties Argent and RL4137 (red-kernelled wheat) but not in W98616, a white wheat variety with acceptable grain color. Derivatives of the isoflavone formononetin were more abundant in W98616 relative to RL4137 and Argent. Vanillin-HCl staining indicated that RL4137 sequestered high levels of proanthocyanidin (PA) throughout its entire seed coat, whereas white wheats sequestered PAs as discrete speckles. Argent possessed abundant speckles over its entire seed coat, whereas speckles were almost undetectable in W98616. In mature kernels, flavonoids throughout the seed coat of RL4137 reacted with NaOH, but only the speckles appeared to react in white wheats. W98616 consistently had lighter grain than Argent before and after NaOH treatment. Free and bound phenolic differences in bran samples confirmed that the darker seed coat color of Argent, relative to W98616, was likely due to higher total phenolic acid content. Although isoflavones accumulated in Argent and RL4137, it appears that the majority of the flux through the flavonoid pathway ultimately accumulates quercetin derivatives and PAs. In W98616, PAs accumulate, but it appears that flavonoid biosynthesis ultimately accumulates isoflavones. Argent, compared to W98616, generally accumulated higher levels of total phenolics (flavonols, stilbenes, and PAs) within its darker pigmented bran. 相似文献
856.
Tokar RL Johnson RE Hill TW Pontius DH Kurth WS Crary FJ Young DT Thomsen MF Reisenfeld DB Coates AJ Lewis GR Sittler EC Gurnett DA 《Science (New York, N.Y.)》2006,311(5766):1409-1412
During the 14 July 2005 encounter of Cassini with Enceladus, the Cassini Plasma Spectrometer measured strong deflections in the corotating ion flow, commencing at least 27 Enceladus radii (27 x 252.1 kilometers) from Enceladus. The Cassini Radio and Plasma Wave Science instrument inferred little plasma density increase near Enceladus. These data are consistent with ion formation via charge exchange and pickup by Saturn's magnetic field. The charge exchange occurs between neutrals in the Enceladus atmosphere and corotating ions in Saturn's inner magnetosphere. Pickup ions are observed near Enceladus, and a total mass loading rate of about 100 kilograms per second (3 x 10(27) H(2)O molecules per second) is inferred. 相似文献
857.
Foulger GR 《Science (New York, N.Y.)》2006,313(5788):768-769