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排序方式: 共有76条查询结果,搜索用时 15 毫秒
1.
ZHAO Ye 《自然科学进展(英文版)》2004,14(8):713-715
A detailed record of sea level changes during the last 2500 years is preserved in the northernwest coast of Fildes Peninsula in Antarctica. Fourteen marine alga layers were deposited in the beach with an altitude of 2.80 m, and one diatom layer deposited in the ancient lake on the terrace with an altitude of 6.84 m. A radiocarbon age of 695±70 aBP was obtained for the modern marine alga, and the age was used in correction for the carbon reservoir effect of the marine alga. Sea level fell 4.98 m from the 4th century B.C. to the early 13th century, at an average of -0.31 cm/a, then rose about 0.78 m during the early 13th to the middle 18th century, at an average of 0.14 cm/a. It has risen about 0.16 m since the middle 18th century, at an average of 0.07 cm/a. 相似文献
2.
Jianguo Ren Xianbin Wang Jianfa Chen Chunyuan Li Hui Yang Ziyuan Ouyang 《科学通报(英文版)》1998,43(9):761-761
The isotopic cumpositions of helium have been investigated in hot spring gases sampled from the Liaodong Peninsula. China.
The3He/4He ratios range from 0.14 Ra (0.14 times the atmospheric3He/4He ratio of 1.40 × 10-6 to 0.72 Ra.3He/4He versus4He/20Ne ratios and He contents suggest that a small amount of mantle-derived helium reaches the earth’s surface. Helium iwtope
ratios of the hot spring gases show a distribution pattern similar to the regional heat flow values, indicating that the positive
thermal anomaly occurring in the rtrea is closely associated with the presence of mantle-derived helium. The observations
described above provide some significant evidence that the molten magma originating from partial melting of the upper mantle
may have intruded into the continental crust along the activity fault. The coupling of the presence of mantle He and heat
flow anomalies to seismic activity in studied region seem to imply that there is an internal relationship between mantle degassing
and seismic activity. 相似文献
3.
山东半岛城市群处于城市化中期,内部城市联系日益密切,城市经济综合实力、联系距离是影响城市流产生的原因.采用因子分析测度城市经济综合实力,通过赋权重求得相对距离矩阵,并引入城市流公式计算各城市间的城市流,得出胶济铁路沿线城市城市流大,而刚刚加入半岛城市群的日照、东营城市流较小,且以外向流出为主,基于原因分析提出中心城市和基础设施建设等具体对策. 相似文献
4.
海陆联测的大地电磁数据处理与综合解释 总被引:2,自引:0,他引:2
结合研究区雷州半岛的实际地质情况,通过在陆上布置磁道,近岸的浅海-潮间带海水中布置电道,实现了海陆电场和磁场分离同步采集的大地电磁勘探,填补了海陆地震空白带.通过建立针对性的地电模型,利用正演模拟方法校正了海水对陆地测点的畸变效应影响,并通过大地电磁二维反演以及重力和磁力数据的正反演计算,进行了综合地质地球物理解释,证明了海陆联测数据的采集、处理和解释效果. 相似文献
5.
Specialist and generalist species in habitat use: implications for conservation assessment in snakes
《Journal of Natural History》2012,46(41-44):2765-2774
Habitat specialization is recorded as one of the central factors that make species vulnerable to extinction. Among snakes, there is considerable variation in this trait, as some species are specialists and others are generalists in habitat use. We have quantified habitat specialization in the snakes of the southern Iberian Peninsula, and compared it with their abundance and IUCN categories. All data were combined for a principal components analysis that discriminated two main groups: three generalist species that live in all types of habitat, and five specialist species that ranged from rather scarce to extremely rare and are found only in unaltered habitats. The three generalist snakes are not threatened and their IUCN category is Least Concern. Three out of the five specialist species are categorized as Near Threatened, Vulnerable, and Endangered at regional or national levels. The other two species are currently considered Not Threatened and we discuss whether they are incorrectly classified. The conservation status of snakes is difficult to evaluate because of their secretive habits and low population densities. We suggest that quantifying habitat specialization may be a useful tool for assessing the conservation status of secretive organisms such as snakes. 相似文献
6.
《Journal of Natural History》2012,46(31-32):1929-1945
The ground plan of the bot flies (Oestridae, part) is compared with those of Ephydroidea and Calyptratae. Comparative anatomy suggests that the bot flies are unlikely to have arisen from within Calyptratae and that their derivation from near the base of Ephydroidea is more probable. A large body of evidence is assembled to counter the theory that would place Oestridae within the Tachinidae family-group. It is shown that Hippoboscoidea is unlikely to be monophyletic. The fit of Glossinidae to the suggested ground plan profile of the Ephydroidea/bot flies is shown to be good. 相似文献
7.
《Journal of Natural History》2012,46(17-18):1065-1078
Recent molecular analyses revealed unexpected genetic variability within Hydraena gracilis, one of the most common and widespread European moss beetles, belonging to the West Palaearctic endemic “Haenydra” lineage. For this taxon, molecular data univocally evidenced two distinct clades, the first one including populations from the Iberian Peninsula, and the second including populations from central and eastern Europe. Aedeagal morphology of H. gracilis was further investigated, finally demonstrating the actual existence of a new cryptic species of the H. gracilis complex in Portugal, Spain and the French Pyrenees. The geographical range of the true H. gracilis was consequently revised. Finally, dichotomous keys for males of all species belonging to the H. gracilis complex, and for males of all the Iberian “Haenydra” species, are also supplied. 相似文献
8.
中南半岛恐怖袭击事件时空演变特征分析 总被引:1,自引:0,他引:1
以国际恐怖主义事件数据库等数据源为基础,采用空间统计和核密度分析方法,分析了中南半岛恐怖袭击的时空演变特征,探讨了恐怖袭击目标和方式的转变特征,介绍了中南半岛恐怖袭击事件中的主要恐怖组织。研究表明,中南半岛逐渐成为恐怖组织袭击的重点区域之一,并且采取的方式杀伤性更强,政府应该采取措施预防应对恐怖袭击事件。 相似文献
9.
10.
景谷是我国傣族傣哪支系的一个聚居区,由于优越的地理位置和丰富的自然资源,使得在南诏大理国时期这一区域曾经兴盛一时,成为云南通往中南半岛的南部重镇,其民族和历史也呈现出丰富多姿的面貌。通过对汉文史料和当地傣文古籍的对比,辅以相关的田野调查,对景谷傣族的源流和傣族土司世系进行分析,并理清景谷傣族源流和土司世系,对于丰富少数民族历史研究和进一步探索历史上云南与中南半岛的关系具有一定意义。 相似文献