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701.
Detailed examination of China's 1982 census data confirms that the standard of age reporting among the Han Chinese, and among many of the ethnic minorities, is very good. Furthermore the quality of age reporting is unaffected by large variations in levels of literacy which exist between men and women, between young and old, and between rural and urban areas. Much of the credit for the high quality of China's age reporting stems from the distinctive nature of Chinese traditional calendars. However, in the far west of China, in the Xinjiang Autonomous Region, age heaping and age exaggeration are as bad as they are in many other developing countries. The authors show that the poor quality of age reporting in Xinjiang is confined to three of the region's ethnic communities, the Uygur, Kirgiz and Tajik, who appear to neither know, nor care, how old they are. 相似文献
702.
冀西北长城纪宣龙式铁矿层中微体植物化石的发现及其意义 总被引:10,自引:0,他引:10
本文研究的是笔者等在冀西北长城系串岭沟组宣龙式铁矿层中发现的微体植物化石,这些化石都保存在铁质叠层石(肾状赤铁矿)和铁质核形石(鲕状赤铁矿)的基本层中。微化石以丝状体为主,部分为球状体。归属于原核生物蓝藻门颤藻科的两个属和色球藻科的一个属。化石层同位素年龄约在1800—1757Ma。这些化石与北美冈弗林特组微化石比较,既有些相似,又有些区别。该化石的发现为研究铁矿的成因,指示沉积环境及层位对比都很有意义。 相似文献
703.
自1990年6月北京天文台太阳射电偏振仪投入实测以来,观测到一百多个“Spike”和短时标精细结构微波幅射,其中包括一些新的微波幅射特征。本文给出了主要的四点特征:(1)窄带辐射;(2)快速偏振逆转;(3)快速频率漂移;(4)不同时标的准周期振荡。 相似文献
704.
本文记述了发现于辽南复州湾上石炭统太原组的燕海扇类,计5属17种。讨论了Annuliconcha与Paradoxipecten的属征及有关问题。上述发现在东北地区尚属首次。 相似文献
705.
Deyi Wu Bohua Zhang Li Yan Hainan Kong Xinze Wang 《International Journal of Mineral Processing》2006,80(2-4):266-272
Hydrothermal conversion of fly ash into zeolites was conducted and the effects of the addition of sodium halide and waste solutions produced after zeolitization of fly ash, as well as the adjustment of the Si/Al ratio prior to synthesis process on the formation and cation exchange capacity (CEC) of zeolite product were evaluated. Both the addition of NaCl and NaF ameliorated the crystallinity and CEC of synthesized zeolite, but NaF had a better improvement effect. Na+ was considered to enhance the crystallization of zeolite, while F− favored the dissolution of fly ash. The type of zeolite formed depended on the Si/Al ratio of the starting material prior to the nucleation and crystallization of zeolite. The adjustment of the Si/Al ratio of fly ash by addition of Na2SiO4 and Al(OH)3 changed the type and CEC of zeolite. Waste solutions contained large amount of Si and little Al due to the formation of a zeolite named NaP1 in zeolite terminology with the Joint Committee of Powder Diffraction Standard (JCPDS) code of 39-0219. The alkalinity decreased largely. As a result, the CEC value of zeolite products synthesized with waste solution as alkali source decreased. The supplementation of new alkali to adjust the alkalinity of waste solution could enhance the CEC of synthesized product. It was concluded that: (1) addition of sodium halide and adjustment of the Si/Al ratio prior to synthesis can improve the quality of zeolite; (2) waste solutions produced following the zeolitization of fly ash can be reused as an alkali source in the activation of fly ash; zero-emission of waste solution in the synthesis of zeolite from fly ash is possible. 相似文献
706.
Maowen Li Yongqiang Xiong Lloyd R. Snowdon Dale Issler 《Journal of Geochemical Exploration》2006,89(1-3):214
Molecular and isotopic compositions of crude oils in the Beaufort–Mackenzie Basin confirm three genetic end-member oil groups and suggest extensive cross-formational hydrocarbon fluid flows in the Tertiary deltaic system. Inter- and intra-fractional variations in the geochemistry of the Tertiary-reservoired oils indicate that the oil source/maturity signatures were substantially masked by biomarkers that were picked up along migration pathways. Thus, many of the previously recognized “immature non-marine oils” are in fact thermally mature, probably derived from unpenetrated deeper marine source rocks. Although the effective source rock volumes have not been evaluated and their exact stratigraphic levels remain unknown, the relative timing of oil generation versus trap formation, rather than poor source quality, may be the cause of under-filled traps in the offshore area. 相似文献
707.
Are the South and North Liaohe Groups of North China Craton different exotic terranes? Nd isotope constraints 总被引:29,自引:1,他引:29
Sanzhong Li Guochun Zhao Min Sun Zongzhu Han Guangtao Zhao Defeng Hao 《Gondwana Research》2006,9(1-2):198
The Liaohe Group is an important Paleoproterozoic stratigraphic unit in the northeastern part of the North China Craton and is traditionally subdivided into the North and South Liaohe Groups. Associated with both the North and South Liaohe Groups are voluminous Paleoproterozoic granitoid rocks, named the Liaoji granitoids. Different tectonic models, including terrane amalgamation, continent–arc collision and rift closure, have been proposed to interpret the tectonic setting and evolution of the North and South Liaohe Groups and associated Liaoji granitoids. At the centre of the controversy between these models is whether or not the North and South Liaohe Groups developed on the same Archean basement. Nd isotopic geochemistry of the Liaoji granitoids provides important constraints on this controversial issue. The Liaoji granitoids associated with the North and South Liaohe Groups display similar εNd values, restricted to a narrow range from 0 to 2, implying that these granitoid rocks were derived from the same or a similar magma source. Moreover, the Liaoji granitoids associated with the North and South Liaohe Groups have similar Nd model ages (TDM), ranging from 2.4 to 2.6 Ga, suggesting that the protoliths of the Liaoji granitoids associated with both groups may have formed simultaneously, and that the basement rocks underneath the Liaoji granitoids and associated North and South Liaohe Groups belong to the same continental block rather than two different blocks. Combining lithological, structural and geochronological considerations, we interpret the North and South Liaohe Groups as having developed on a single late Archean basement that underwent Paleoproterozoic rifting associated with the intrusion of the Liaoji granitoids and the formation of the Liaohe Group, and closed upon itself in the Paleoproterozoic. 相似文献
708.
Element geochemistry of lake sediments has been widely used to detect climate change because element composition and ratios can reflect the weathering degree in the source area. Given the dement composition of lake sediments from Gulug Co Lake, Hoh Xil, Qing- hai-Xizang Plateau, chemical index of alteration (CIA), index of composition variability (ICV) and other element ratios have been used to establish the weathering sequence of this area since 1820 AD. The weathering is so weak that the element composition change is more sensitive to climate change and autochthonous processes. From 1820 to 1984 AD, there were two drier periods with a wetter interval from 1870 to 1945 AD. After 1984 the weather showed a tendency of becoming wet. 相似文献
709.
710.
一、“十五”期间取得的主要成绩
“十五”期间,全局工勘施工业坚持以市场为导向,从实际出发,大胆创新,加强实践,及时调整不合时宜、束缚和阻碍生产力发展的一些制度、观念和作法,通过不断深化改革,调整队伍结构和产业结构、提升资质、改善装备水平、加强管理等措施,较好地拓宽了市场服务领域,创收能力逐年提高,其作为地勘经济骨干产业的地位和作用日益凸显。 相似文献