全文获取类型
收费全文 | 415篇 |
免费 | 30篇 |
国内免费 | 70篇 |
专业分类
测绘学 | 31篇 |
大气科学 | 13篇 |
地球物理 | 42篇 |
地质学 | 310篇 |
海洋学 | 29篇 |
天文学 | 7篇 |
综合类 | 27篇 |
自然地理 | 56篇 |
出版年
2023年 | 4篇 |
2022年 | 6篇 |
2021年 | 14篇 |
2020年 | 6篇 |
2019年 | 4篇 |
2018年 | 23篇 |
2017年 | 15篇 |
2016年 | 9篇 |
2015年 | 13篇 |
2014年 | 22篇 |
2013年 | 22篇 |
2012年 | 21篇 |
2011年 | 32篇 |
2010年 | 16篇 |
2009年 | 24篇 |
2008年 | 28篇 |
2007年 | 33篇 |
2006年 | 20篇 |
2005年 | 23篇 |
2004年 | 20篇 |
2003年 | 19篇 |
2002年 | 13篇 |
2001年 | 13篇 |
2000年 | 8篇 |
1999年 | 11篇 |
1998年 | 14篇 |
1997年 | 15篇 |
1996年 | 11篇 |
1995年 | 10篇 |
1994年 | 5篇 |
1993年 | 7篇 |
1992年 | 5篇 |
1991年 | 8篇 |
1990年 | 8篇 |
1989年 | 3篇 |
1988年 | 2篇 |
1987年 | 4篇 |
1984年 | 1篇 |
1980年 | 2篇 |
1978年 | 1篇 |
排序方式: 共有515条查询结果,搜索用时 187 毫秒
81.
LIU Yongqing GAO Linzhi LIU Yanxue Institute of Geology Chinese Academy of Geological Sciences Beijing E-mail: liuyongqing@cags.net.cn 《《地质学报》英文版》2005,79(4):533-539
Molar tooth structure (MTS) represented by complex ptygmatical shapes is widely distributed in the Proterozoic of the world. MTS filled by fine, equant sparry calcite (or dolomite) displays an abrupt contact with hosting rocks, which are mainly composed of carbonaceous micrites and fine-grained carbonates with local silts and stormdominated deposits with graded, cross or wave beddings, numerous erosional surfaces and truncated and fills or guttered bases. Occurrence of MTS suggests a result of the constraint of sedimentary facies, and the storm-base in ramp settings is the maximum depth for the formation of MTS. Vertical succession of MTS-bearing carbonates shows a deposition stacked by high-frequency shallow subtidal and peritidal cycles. An individual cyclic MTS-bearing sequence is characterized by thinning, shallowing and dynamic decreasing-upward, and peritidal caps of purple red iron and organic carbonaceous sediments with more complicated shapes of MTS are common on the top of individual MTS-bearing sequences. 相似文献
82.
V. G. Knyazev R. V. Kutygin S. V. Meledina 《Stratigraphy and Geological Correlation》2009,17(2):192-203
Modifications to the upper Bathonian zonal scale for northern East Siberia provided by the newly available paleontological record on Middle Jurassic reference sections in the Arctic regions of Yakutia and by the revised earlier collections, are justified. The oldest East Siberian members of Cadoceras are found to be characteristic not of the initial Callovian age as believed by Russian paleontologists, but of the terminal Bathonian age as was previously shown in the biostratigraphic scheme of East Greenland. The succession of zones and index species analogous to that of the latter is revealed in the studied region and the zonal boundaries in Siberia and East Greenland are inferred to be synchronous. Finds of Cadoceras calyx in the upper Bathonian scale permitted, for the first time, the recognition of a corresponding zone. The Bathonian-Callovian boundary is placed between the calyx and anabarense zones. The upper Bathonian zonal scale of northern East Siberia is now in total agreement with the East Greenland zonal scale. 相似文献
83.
Nadezhda Priyatkina William J. Collins Andrei Khudoley Dmitry Zastrozhnov Victoria Ershova Kevin Chamberlain 《International Geology Review》2017,59(13):1632-1656
Identifying the cratonic affinity of Neoproterozoic crust that surrounds the northern margin of the Siberian Craton (SC) is critical for determining its tectonic evolution and placing the Craton in Neoproterozoic supercontinental reconstructions. Integration of new U–Pb–Hf detrital zircon data with regional geological constraints indicates that distinct Neoproterozoic arc-related magmatic belts can be identified within the Taimyr orogen. Sedimentary rocks derived from 970 to 800 Ma arc-related suites reveal abundant Archean and Paleoproterozoic detritus, characteristic of the SC. The 720–600 Ma arc-related zircon population from the younger Cambrian sedimentary rocks is also complemented by an exotic juvenile Mesoproterozoic zircon population and erosional products of older arc-related suites. Nonetheless, numerous evidences imply that both arcs broadly reworked Siberian basement components. We suggest that the early Neoproterozoic (ca. 970–800 Ma) arc system of the Taimyr orogen evolved on the active margin of the SC and probably extended along the periphery of Rodinia into Valhalla orogen of NE Laurentia. We also suggest the late Neoproterozoic (750–550 Ma) arc system could have been part of the Timanian orogen, which linked Siberia and Baltica at the Precambrian/Phanerozoic transition. 相似文献
84.
The pores in shales are mainly on a nanometer scale, and the pore-size distribution is vital with regard to the preservation and exploitation of shale gas. This study focuses on the organic-rich lower Cambrian black shale in the Upper Yangtze Platform, South China and investigates their TOC, mineralogical composition and nanopore structure. Low-pressure N2 and CO2 adsorption experiments were conducted at 77.35 K and 273.15 K, respectively, and the nanopore structures were characterised by the modified Brunauer–Emmett–Teller, Dubinin–Radushkevich, t-plot, Barrett–Joyner–Halenda and density functional theory (DFT) methods. The results indicate the following. (1) The lower Cambrian shale has a high TOC content (1.77–7.23 wt%) and a high quartz content (27.7–51.6 vol%). The total specific surface area varies from 12.02 to 28.87 m2/g. Both the total specific surface area and quartz content are positively associated with the TOC content. (2) Shale samples with a higher TOC content have a greater number of micropores, resulting in more complicated nanopore structures. Micropore volumes/surface areas and non-micropore surface areas all increase with increasing TOC content, indicating that TOC is the key factor determining the nanopore structure of the lower Cambrian shale. (3) A combination of N2 and CO2 adsorption provides the most suitable detection range (~0.3–60 nm) and is both highly reliable and accurate with regard to nanopore structure characterisation. 相似文献
85.
ZHANG Guobin YANG Yanchen Alexander S. VAKH Vadim G. KHOMICH WANG Keyong YE Songqing HAN Shijiong 《《地质学报》英文版》2017,91(5):1733-1750
The Berezitovoe deposit is a large-sized Au-Ag-Zn-Pb deposit in the east of the SelengaStanovoi superterrane, Russia. Au-Ag orebodies are hosted by tourmaline-garnet-quartz-muscovite metasomatic rocks; Zn-Pb orebodies are hosted by granodiorites, porphyritic granites and tourmalinegarnet-quartz-muscovite metasomatic rocks. These orebodies are surrounded by wall rocks dominated by the Tukuringra Complex granodiorites, porphyritic granites, and gneissic granodiorites. The alteration includes silicification and garnet, sericitization chloritization, carbonatization and kaollinization. LA-ICP-MS U-Pb zircon dating indicates that the gold mineralization can be divided into two stages in the Berezitovoe polymetallic gold deposit(at 363.5 ± 1.5 Ma, and133.4± 0.5).Hornblende-plagioclase gneisses of the Mogocha Group in the study area underwent Paleoproterozoic metamorphism(at 1870 ± 7.8 and 2400 ± 13 Ma), gneissic granodiorite of the Tukuringra Complex yields a late Paleozoic magmatic age(at 379.2 ± 1.1 Ma),and subalkaline porphyritic granitoid of the Amudzhikan Complex yield late Mesozoic magmatic ages(133-139 and 150-163 Ma). Granodiorites of the Tukuringra Complex in the study area have high concentrations of SiO_2(average of 60.9 wt%), are aluminum-oversaturated(average A/CNK of 1.49), are enriched in the large ion lithophile elements(e.g.,K, Rb, and Ba), U, Th, and Pb, are depleted in high field strength elements(e.g., Ta, Nb, and Ti), and have slightly negative Eu and no Ce anomalies in chondrite-normalized rare earth element diagrams.Fluid inclusions from quartz veins include three types: aqueous two-phase, CO_2-bearing three-phase,and pure CO_2. Aqueous two-phase inclusions homogenize at 167℃-249℃ and have salinities of 4.32%-9.47% NaCl equivalent, densities of 0.86-0.95 g/cm~3, and formed at depths of 0.52-0.94 km. In comparison, the C0_2-bearing three-phase inclusions have homogenization temperatures of 265℃-346℃,salinities of 7.14%-11.57% NaCl equivalent, and total densities of 0.62-0.67 g/cm~3. The geochemical and zircon U-Pb data and the regional tectonic evolution of the study area, show that the Berezitovoe polymetallic gold deposit formed in an island arc or active continental margin setting, most probably related to late Paleozoic subduction of Okhotsk Ocean crust beneath the Siberian Plate. 相似文献
86.
河流冲刷对第四纪软弱地层岸坡的地质灾害起到控制性作用。本文以磨西台地冰水堆积物岸坡为例,充分考虑河流与岸坡地质灾害之间的内在联系,基于对实测地质灾害的分析结果,采用Logistic监督分类方法,评价各环境因子(尤其是河流冲蚀特性因子)在河流岸坡稳定性评价中的作用,进而采用高相关的环境因子进行地质灾害易发性预测。研究表明,河流弯曲度、河流流量、岸坡坡度、河床宽度、岸坡宽度与地质灾害的发育相关性强,采用这些参数和Logistic模型预测的地质灾害易发性能很好的反映现状和未来地质灾害的发育特点,进而提出了磨西台地岸坡地质灾害防治的初步建议。 相似文献
87.
Neocomian reservoirs in the Mesozoic sedimentary cover of West Siberia have a complex geological structure. Their wedge-like (clinoform) geometry, with abrupt thickness changes and facies diversity (continental, shoreface, and pelagic deposits), causes difficulty in correlation between drilling- and seismics-based sand formations and clay caps. East-wedging (west-dipping) clinoforms consisting of interbedded clay and sand have the greatest reservoir potential in the West Siberian basin. Prediction of new oil and gas plays and their reservoir potential assessment require regional reconstructions in addition to local contour maps of individual zones and fields. However, the simulation technology which has been applied for years to Jurassic regional reservoirs is not fully applicable to the Neocomian clinoform sequences. Therefore we have adapted it correspondingly and suggest new tools to make due regard for the clinoform reservoir structure. The new approach has been tested through computing several structure and thickness contour maps of clinoform sequences for three largest regional Neocomian reservoirs (sub-Sarman, sub-Pim, and sub-Alymka) in northern and arctic West Siberia. 相似文献
88.
89.
中朝古陆的解体与华北、华泰二克拉通的确立 总被引:1,自引:0,他引:1
半个世纪之前,黄汲清和任纪舜等将华北、东北南部以及西北的阿拉善这类凡有前寒武纪结晶基底出露的地区确定为单一的中朝古陆(或准地台).这种观念一直被沿用迄今.近年,构造地层地体的研究发现原称之“中朝古陆”是由华北和华泰两个克拉通构成,计 11个地块或地体.重新厘定的华北克拉通,其范围只限于辽宁省西部和北部、河北省、内蒙古南... 相似文献
90.