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151.
中国经济系统中化石燃料的物质流分析   总被引:19,自引:0,他引:19  
研究了中国经济系统与自然环境间相互作用 ,为可持续发展提供可度量的指标 ,对 1990至 2 0 0 0年间中国经济系统所使用的化石燃料数据进行统计分析。以在欧美得到广泛应用的物质流分析方法为基础 ,结合中国统计资料的特点 ,重点计算化石燃料物质需求总量 ,并通过与人口、经济数据的结合得到其他统计指标。研究表明 ,中国经济系统对化石燃料的利用存在很多问题 ,为了实现化石燃料利用的可持续发展 ,2 0 10年和 2 0 5 0年中国对化石燃料的利用效率应该分别达到 1990年西德和 1994年日本的水平  相似文献   
152.
本文就龙永煤田童子岩组地层的一般特征,各段及亚段在岩性、岩相、化石组合、岩石粒度趋势、含煤性、煤层灰成分、特别是地层的地球物理特征进行了分析,对各段及亚段的主要区别进行详细说明,有助于地质工作者清楚认识这些地层的特征,这对于解决复杂地质构造问题、进行岩煤层对比等有重要意义。  相似文献   
153.
Protopteryx, a monotypic fossil bird discovered from the Sichakou basin in Fengning, Hebei, is the most primitive enantiornithine currently known. The bird-bearing strata do not contain the index fossils of the Yixian Formation in western Liaoning; the fish and bird fossils have more primitive features than the related forms found in the Yixian Formation, and the conchostracans are those usually distributed in the Dabeigou and Dadianzi formations in northern Hebei. Besides, the Protopteryx-bearing strata underlie the deposits bearing the index fossils of the Yixian Formation in the neighboring basin. Thus, it could be confirmed that the horizon of Protopteryx should be lower than the Yixian Formation, and is approximately equivalent to the Dadianzi Formation in northern Hebei. This is the lowest horizon of the known fossil birds in China and Mesozoic enantiornithine birds in the world. Accompanying Protop- teryx, there are other birds, acipenseriform fishes, salamanders, and mammals, which compose the Peipiaosteus fengningensis-Protopteryx fengningensis assemblage. This new assemblage traces the vertebrate evolution history of the Jehol Biota back to 130.7 Ma before. It is suggested that the de- marcation of the Jehol Biota should be based on the large-scale tectonic-sedimentary cycles, and Peipiaosteus, instead of Lycoptera, could be taken as the vertebrate representative of the Jehol Biota.  相似文献   
154.
“许昌人”头盖骨的发现,印证了“多地区起源”及人类连续进化附带杂交模式学说的正确性,面对“许昌人”头盖骨,“非洲夏娃说”、“代替说”等不攻自破。“许昌人”不仅可能是北京猿人的后代,同时还应是现代中国人的祖先。同时“许昌人”头盖骨的发现在人类学研究领域对DNA的科学证明提出了严峻挑战。它以事实提醒我们,面对现代人类多源说的实证资料,在人类学、考古学和基因科学诸多学术研究领域里调整学术思路势在必然。  相似文献   
155.
156.
Fossil insects from the Middle Jurassic of Daohugou, Inner Mongolia were investigated using Scanning Electron Microscope (SEM) for the first time, and portions and distribution of some elements in compression and pyrited fossils were also revealed by X-ray Energy Dispersive Spectroscopy (EDS) attached to SEM. Most of compression fossil insects from the Daohugou Biota are preserved in organic remains (diagenetic products of the original organic components). A small part of compression fossils retain a comparatively high Fe concentration which probably resulted from the absorption of Fe by biopolymers during the decaying period. Pyritized insect fossils suggest that the “fossil envelop” model found in the Early Cretaceous Jehol Biota probably also occurs in the Daohugou Biota. Different preservation modes show various mechanisms of fossilization, and also suggest that several different microenvironments are present in Daohugou palaeolakes. Supported by National Basic Research Program of China (Grant No. 2006CB806400), National Natural Science Foundation of China (Grant Nos. 40872015, 40523004, 40632010), and Special Fund for Graduates in the Graduate University of the Chinese Academy of Sciences  相似文献   
157.
Hominin fossils are the most important materials for exploring questions about human origins and evolution. Because human fossils are very rare, it is impossible to use highly destructive techniques in order to study their morphology. Traditional analyses can only rely on the information gained from the study of the external morphology of specimens, and these approaches limited the study of human evolution. The application of computed tomography (CT) has facilitated major developments in paleoanthropology. To date, few studies on Chinese hominin fossils have used CT scanning methodology, but this is rapidly changing. In order to better understand the application of CT methodology in paleoanthropology, we review the applications of CT scanning on hominin fossils throughout the world. Studies examined include virtual fossil reconstruction, the use of endocasts to elucidate brain morphology, biomechanical analyses of bone distribution, imaging of mummies and research on early human health, and skeletal and dental microanatomical research.  相似文献   
158.
159.
Mutualism is an interactive, mutually beneficial relationship between two or rarely more unrelated taxa. It is ubiquitous in most environments. In the marine environment it is most likely to occur in shallow marine, oligotrophic regions, the open marine photic zone and oxygen-limited environments. Whereas the eukaryote cell is of some antiquity, other mutualisms may have been acquired during the Phanerozoic. The fossil record provides inferential evidence for the minimum time of origin and occurrence of mutualisms. This suggests that a variety of mutualisms may have occurred during the Palaeozoic with most apparently being terminated by the Permian mass extinction. Tracing back the origin of extant mutualisms suggests that the majority of these began in the Mesozoic or Cenozoic and indicate an increase to the present day. Whether the increase in mutualisms is a product of increased biodiversity or whether mutualisms may have partly driven biodiversity is unclear.  相似文献   
160.
分析了湖南省西北地区沅、澧水流域17个有关旧石器人类遗址和9类更新世时期哺乳动物化石点的史料,结合田野考察,目前已掌握的资料有石门智人股骨化石1件、旧石器9种、哺乳动物群化石8目36种.开展了有关旧石器演化的规律和哺乳动物化石的生物分类与组合形式的研究,客观地揭示了湖南省西北地区史前人类的演化规律以及地理变迁、气候再造与其生态环境的关系.  相似文献   
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