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排序方式： 共有365条查询结果，搜索用时 15 毫秒
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Aragonitic, unconsolidated sediments from the borings on the Eniwetok and Bikini atolls are isotopically identical with unaltered skeletal fragments, whereas the recrystallized limestones exhibit isotopic variations resulting from alteration in meteoric waters during periods of emergence. Dolomites and associated calcites are enriched in O(18), perhaps because of interaction with hypersaline brines. 相似文献
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Mannhart J Gross R Hipler K Huebener RP Tsuei CC Dimos D Chaudhari P 《Science (New York, N.Y.)》1989,245(4920):839-841
Spatially resolved resistivity measurements of current transport across individual grain boundaries have been made on superconducting YBa(2)Cu(3)O(7). These experiments were done by low-temperature scanning electron microscopy with a resolution of 1 to 2 micrometers, and they show directly the limitation of the critical current density caused by grain boundaries in YBa(2)Cu(3)O(7). Furthermore, complex spatial patterns of the current transport across grain boundaries were observed. These patterns reflect self-excited resonances of the grain boundaries and are closely correlated to the unexplained "sub-gap structure" in the current-voltage characteristics of polycrystalline YBa(2)Cu(3)O(7). 相似文献
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Biodegradable polymers for the environment 总被引：1，自引：0，他引：1
Biodegradable polymers are designed to degrade upon disposal by the action of living organisms. Extraordinary progress has been made in the development of practical processes and products from polymers such as starch, cellulose, and lactic acid. The need to create alternative biodegradable water-soluble polymers for down-the-drain products such as detergents and cosmetics has taken on increasing importance. Consumers have, however, thus far attached little or no added value to the property of biodegradability, forcing industry to compete head-to-head on a cost-performance basis with existing familiar products. In addition, no suitable infrastructure for the disposal of biodegradable materials exists as yet. 相似文献
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Two representative anabolicsteroids caused an increase in the uptake of alpha-aminoisobutyric acid-1-C(14) in the levator ani muscle of rats. The distribution ratio between that muscle and the plasma was increased fourfold by the administration of a synthetic anabolic steroid and twofold by administration of testosterone propionate. The determination of this increase may serve as an indicator for the myotrophic effect of anabolic steroids. 相似文献
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Endres M Cheneau M Fukuhara T Weitenberg C Schauss P Gross C Mazza L Bañuls MC Pollet L Bloch I Kuhr S 《Science (New York, N.Y.)》2011,334(6053):200-203
Quantum phases of matter are characterized by the underlying correlations of the many-body system. Although this is typically captured by a local order parameter, it has been shown that a broad class of many-body systems possesses a hidden nonlocal order. In the case of bosonic Mott insulators, the ground state properties are governed by quantum fluctuations in the form of correlated particle-hole pairs that lead to the emergence of a nonlocal string order in one dimension. By using high-resolution imaging of low-dimensional quantum gases in an optical lattice, we directly detect these pairs with single-site and single-particle sensitivity and observe string order in the one-dimensional case. 相似文献