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31.
32.
汉诺坝玄武岩中地幔岩捕掳体REE和Sr,Nd同位素地球化学 总被引:20,自引:3,他引:20
本文报道汉诺坝玄武岩中地幔岩捕掳体的REE丰度和Sr、Nd同位素组成。不同岩石类型的REE配分模式和同位素组成反映地幔部分熔融程度和交代作用过程。二辉橄榄岩亏损轻稀土,是原始地幔经不同程度部分熔融的残留体。方辉橄榄岩具U型REE配分模式,是强烈亏损的地幔岩被熔体非化学平衡交代的结果。二辉岩脉状体富轻、中稀土,它同与脉状体接触的二辉橄榄岩可达化学平衡或近于化学平衡,而二辉岩脉状体的形成与玄武岩岩浆无成因关系。据对二辉岩脉状体和不含脉状体橄榄岩的Sm-Nd同位素定年,这种脉状体形成于300Ma左右。 相似文献
33.
贵州关岭三叠系竹杆坡组、小凹组头足类化石——兼论关岭生物群的时代 总被引:10,自引:1,他引:10
贵州关岭地区中、上三叠统竹杆坡组和小凹组产较丰富的头足类化石,计有11科19届37种,其中Enoploceras,Alloceratites,Sibyllites等属以及Trachyceras aon种系国内首次报道。自下而上可识别出(1)Xenopratrachyceras primum带;(2)Protrachyceras deprati带;(3)Protrachyceras costulatum带;(4)Trachycems multituberculatum带;(5)Sirenites cf. senticosus带等5个菊石带。讨论了每个菊石带的特征,并与国外同期菊石带进行了对比,指出(1)带与欧洲拉丁期早期R.reitzi带相当,(2)和(3)带分别与拉丁期晚期E.curionii带和P.archelaus带相当,(4)和(5)带分别与欧洲早卡尼期早期T.aon带和北美的早卡尼期晚期Sirenites nanseni带对比。关岭生物群产出层位与Trachyceras multituberculatum菊石带层位一致,时代应为早卡尼期早期。 相似文献
34.
长白山地区新生代火山岩的岩石化学及Sr、Nd、Pb同位素地球化学研究 总被引:12,自引:10,他引:12
通过主元素、稀土元素、Sr、Nd、Pb同位素地球化学特征并结合板块俯冲模式来讨论长白山地区新生代火山岩系的形成和演化。大部分样品都进入上地幔Sr演化范围,具低Sr高~(87)Sr/~(86)Sr特点;∑Nd介于-2.3—+2.9之间;不同岩性熔岩的Pb同位素组成变化不大。主元素、REE模式和同位素的资料都证实区内火山岩是源自上地幔的同源岩浆分异演化而成,并有地壳物质的混染。 相似文献
35.
XU Guanghong LU Dadao Institute of Geography Chinese Academy of Sciences Beijing CHINA 《地理学报(英文版)》1998,(3)
IntroductionAlongwithintegratedregionalcooperation,interegionalasociationhasbenthemainpartofregionaleconomicdevelopmentinsome... 相似文献
36.
On the basis of hydrographic data obtained from 12 June to 6 July, 1998, the three-dimensional structure of circulation in
the South China Sea (SCS) is computed using a three-dimensional diagnostic model. The combination of sea surface height anomaly
from altimeter data and numerical results provides a consistent circulation pattern for the SCS, and the main circulation
features can be summarized as follows: In the northern SCS there are a cyclonic eddy C1 near Dongsha Islands and an anti-cyclonic
eddy W1 west of Luzon Island. In the central SCS a strong anti-cyclonic eddy W3 and a cyclonic eddy C3 compose a quasi-dipole
southeast of Vietnam. A coastal northward jet is present at the western boundary near the Vietnam coast above 300 m level.
This northward coastal jet flows northward and turns eastward at about 14°N, and then flows southeastward into the area between
eddies W3 and C3. In the southern SCS the current is weaker. The most important dynamic mechanism underlying the circulation
in the SCS is the joint effect of the baroclinicity and relief (JEBAR), and the second dynamical mechanism is the interaction
between the wind stress and relief (IBWSR). Comparison of the characters of circulation in the SCS during summer 2000 with
that during summer 1998 reveals no obvious variability of the main characteristics. 相似文献
37.
38.
Considering the highly stochastic nature of the hydrological process, wavelet transform was used to analyse the characteristics, trends and causes of variations in annual run‐off (1917–2006) into Tianjin in the Haihe River Basin. Run‐off was steadily declining due to climate change and human activity and a significant decrease in run‐off along the time series was discovered around the 1960s; however, the change in precipitation was insignificant. The time series of run‐off was heavily influenced by a nonlinear feature and mainly influenced by the natural climate before the 1960s, but after the 1970s the change remained steady, with an annual run‐off that fluctuated between 0·2 and 48·4 mm and was maintained at a low level (9·3 mm). The main cause of the run‐off decline in the 1960s was that more than 1900 reservoirs with a total holding capacity of up to 83 mm were constructed in the upper and middle reaches, which controlled 85% of the total run‐off. These projects have played an active role in the reservoir action and water conservation since they were implemented. At the beginning of the 1980s, the demand for water resources increased with the rapid growth of the population and the large‐scale development of industry and agriculture in the Haihe River Basin, which caused a reduction in run‐off into Tianjin. Overall, the hydrological effects of water storage projects regulating river run‐off were beneficial to flood control, but might cause a serious reduction in river run‐off into Tianjin and the lower reaches of the basin. In addition, a decrease in annual precipitation and changes in temperature in Northern China have also had an adverse effect on natural run‐off, which caused a greater decline in water resources, but this did not have a powerful influence on the overall decline in the run‐off. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
39.
LIAO Guanghong YANG Chenghao XU Xiaohu SHI Xingang YUAN Yaochu HUANG Weigen 《海洋学报(英文版)》2012,31(5):26-40
The mesoscale eddy and internal wave both are phenomena commonly observed in oceans. It is aimed to investigate how the presence of a mesoscale eddy in the ocean affects wave form deformation of the internal solitary wave propagation. An ocean eddy is produced by a quasi-geostrophic model in f-plane, and the one-dimensional nonlinear variable-coefficient extended Korteweg-de Vries (eKdV) equation is used to simulate an internal solitary wave passing through the mesoscale eddy field. The results suggest that the mode structures of the linear internal wave are modified due to the presence of the mesoscale eddy field. A cyclonic eddy and an anticyclonic eddy have different influences on the background environment of the internal solitary wave propagation. The existence of a mesoscale eddy field has almost no prominent impact on the propagation of a smallamplitude internal solitary wave only based on the first mode vertical structure, but the mesoscale eddy background field exerts a considerable influence on the solitary wave propagation if considering high-mode vertical structures. Furthermore, whether an internal solitary wave first passes through anticyclonic eddy or cyclonic eddy, the deformation of wave profiles is different. Many observations of solitary internal waves in the real oceans suggest the formation of the waves. Apart from topography effect, it is shown that the mesoscale eddy background field is also a considerable factor which influences the internal solitary wave propagation and deformation. 相似文献
40.
针对地形地籍测绘项目的特点,结合广州市中心城区地形地籍成果更新项目管理实践,探讨地形地籍测绘项目精细化管理的理论和方法。在项目的初期,精心设计整个项目的管理构架,引入过程监理和数据建库机制;在项目实施中,成立联席工作小组,从技术审核、进度控制、质量控制等方面提高项目的执行力;通过周期性沟通协调、人员及设备投入核查、合同约定等手段,有效保障项目的进度和质量,使广州市中心城区近700平方公里的1:500地形地籍成果更新项目顺利完成。 相似文献