全文获取类型
收费全文 | 1286篇 |
免费 | 71篇 |
国内免费 | 44篇 |
专业分类
测绘学 | 68篇 |
大气科学 | 63篇 |
地球物理 | 429篇 |
地质学 | 654篇 |
海洋学 | 67篇 |
天文学 | 42篇 |
综合类 | 14篇 |
自然地理 | 64篇 |
出版年
2024年 | 5篇 |
2023年 | 4篇 |
2022年 | 50篇 |
2021年 | 68篇 |
2020年 | 78篇 |
2019年 | 53篇 |
2018年 | 138篇 |
2017年 | 113篇 |
2016年 | 138篇 |
2015年 | 76篇 |
2014年 | 112篇 |
2013年 | 140篇 |
2012年 | 78篇 |
2011年 | 86篇 |
2010年 | 53篇 |
2009年 | 45篇 |
2008年 | 29篇 |
2007年 | 16篇 |
2006年 | 21篇 |
2005年 | 5篇 |
2004年 | 15篇 |
2003年 | 6篇 |
2002年 | 6篇 |
2001年 | 9篇 |
2000年 | 3篇 |
1999年 | 2篇 |
1998年 | 3篇 |
1997年 | 2篇 |
1996年 | 3篇 |
1995年 | 3篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1991年 | 2篇 |
1990年 | 7篇 |
1989年 | 4篇 |
1986年 | 2篇 |
1985年 | 3篇 |
1984年 | 3篇 |
1983年 | 2篇 |
1979年 | 2篇 |
1977年 | 2篇 |
1976年 | 1篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1972年 | 3篇 |
1971年 | 4篇 |
1969年 | 1篇 |
排序方式: 共有1401条查询结果,搜索用时 15 毫秒
1.
Crustal xenoliths from Calbuco Volcano,Andean Southern Volcanic Zone: implications for crustal composition and magma-crust interaction 总被引:1,自引:1,他引:0
Rosemary Hickey-Vargas Mohammad J. Abdollahi Miguel A. Parada Leopoldo López-Escobar Fred A. Frey 《Contributions to Mineralogy and Petrology》1995,119(4):331-344
Crustal xenoliths in the 1961 andesite flow of Calbuco Volcano, in the southern Southern Volcanic Zone (SSVZ) of the Andes, consist predominantly of pyroxene granulites and hornblende gabbronorites. The granulites contain plagioclase+pyroxene+magnetite±amphibole, and have pronounced granoblastic textures. Small amounts of relict amphibole surrounded by pyroxene-plagioclase-magnetite-glass symplectites are found in some specimens. These and similar textures in the gabbronorites are interpreted as evidence of dehydration melting. Mineral and bulk rock geochemical data indicate that the granulites are derived from an incompatible trace element depleted basaltic protolith that underwent two stages of metamorphism: a moderate pressure, high temperature stage accompanied by melting and melt extraction from some samples, followed by thermal metamorphism after entrainment in the Calbuco andesite lavas. High Nd
T values (+4.0 to +8.6), Nd-isotope model ages of 1.7–2.0 Ga, and trace element characteristics like chondrite normalized La/Yb< and La/Nb1 indicate that the protoliths were oceanic basalts. Similar oceanic metabasalts of greenschist to amphibolite facies are found in the Paleozoic metamorphic belt that underlies the Chilean coastal ranges. Mineral and bulk rock compositions of the gabbronorite xenoliths indicate that they are cognate, crystallizing from the basaltic andesite magma at Calbuco. Crystallization pressures for the gabbros based on total Al contents in amphibole are 6–8 kbar. These pressures point to middle to lower crustal storage of the Calbuco magma. Neither granulite nor gabbro xenoliths have the appropriate geochemical characteristics to be contaminants of Calbuco andesites, although an ancient sedimentary contaminant is indicated by the lava compositions. The presence of oceanic metabasaltic xenoliths, together with the sedimentary isotopic imprint, suggests that the lower crust beneath the volcano is analogous to the coastal metamorphic belt, which is an accretionary complex of intercalated basalts and sediments that formed along the Paleozoic Gondwanan margin. If this is the case, the geochemical composition of the lower and middle crust beneath the SSVZ is significantly different from that of most recent SSVZ volcanic rocks. 相似文献
2.
ABSTRACTA novel approach is introduced for simulation of instantaneous unit hydrographs (IUHs). The model consists of a series of linear reservoirs that are connected to each other, and is referred to as the inter-connected linear reservoir model (ICLRM). By assuming the flow between two reservoirs is a linear function of the difference between the water levels in the reservoirs, a system of first-order linear differential equations is obtained as the ICLRM governing equation. By solving the equations, the discharge from the last reservoir is considered as an IUH. A small-scale laboratory device was constructed for the simulation of IUHs using the model. By studying four hydrographs extracted from the literature, and simulating them using both the ICLRM and the Nash model, it is concluded that the ICLRM can predict these hydrographs more accurately than the Nash model. Due to the simplicity of the construction and operation of the ICLRM and, more importantly, its visual aspect, the ICLRM may be considered as an effective educational tool for studying IUHs. 相似文献
3.
4.
5.
Javad Ashjari Mojtaba Noori Reza Azimi Mohammad Nakhaei 《Arabian Journal of Geosciences》2016,9(3):227
Hydrogeologically, faults may impede, conduit, exert no influence, or may play a combination of these roles on groundwater flow. The object of this paper is to study the hydrogeological role of the Tabarteh fault, which is located on the border of Zagros and Central Iran tectonic zones in an alluvial aquifer. The recorded data of water table levels, chemical parameters, and discharge rate of wells, in addition to geological maps and geophysical results, were collected and evaluated. The outcrop of travertine in limited areas and the emergence of a few small springs within the alluvium show a barrier role of the fault in the groundwater flow. The spatial analysis of chemical components, head time series, and groundwater flow direction assessment demonstrated that the fault acts as both a barrier and a non-barrier in different sections. The multivariate statistical methods of cluster and discriminant analyses also confirm the dual role of the fault. 相似文献
6.
The role of tourism in rural development: Evidence from Iran 总被引:1,自引:0,他引:1
Nooripoor Mehdi Khosrowjerdi Madineh Rastegari Hamid Sharifi Zeinab Bijani Masoud 《GeoJournal》2021,86(4):1705-1719
GeoJournal - Tourism can play an important role in diversifying the rural economy and its expanding in rural areas contributes to the sustainability of the population and the economy of these areas... 相似文献
7.
Taherynia Mohammad Hossein Koopialipoor Mohammadreza Azizzadeh Abbas Fahimifar Ahmad Ghyasvand Soheil 《Geotechnical and Geological Engineering》2021,39(7):5119-5133
Geotechnical and Geological Engineering - Small variation in shear strength parameters results in remarkable changes in the safety factor (SF) of a rock slope. In this regard, rock mass strength of... 相似文献
8.
Khoshghalb Arman Nobarinia Mohammad Stockton Joshua Kalateh Farhoud 《Acta Geotechnica》2021,16(5):1635-1645
Acta Geotechnica - The purpose of this study is to conduct hole erosion tests (HETs) to better understand the progression of concentrated leaks in compacted soils. While samples with high levels of... 相似文献
9.
Natural Resources Research - Assessing reservoir properties and knowing the relationship between different reservoir parameters can significantly help to plan for production from a reservoir. In... 相似文献
10.
Khan Mohammad Rasheed Tariq Zeeshan Abdulraheem Abdulazeez 《Natural Resources Research》2020,29(6):4017-4029
Natural Resources Research - Optimization and monitoring schemes for oil well and reservoir system require accurate estimation of production rate. Real-time monitoring is conducted typically using... 相似文献