全文获取类型
收费全文 | 1699篇 |
免费 | 544篇 |
国内免费 | 373篇 |
专业分类
测绘学 | 3篇 |
地球物理 | 93篇 |
地质学 | 2254篇 |
海洋学 | 156篇 |
综合类 | 72篇 |
自然地理 | 38篇 |
出版年
2024年 | 7篇 |
2023年 | 16篇 |
2022年 | 33篇 |
2021年 | 55篇 |
2020年 | 50篇 |
2019年 | 61篇 |
2018年 | 65篇 |
2017年 | 72篇 |
2016年 | 91篇 |
2015年 | 79篇 |
2014年 | 126篇 |
2013年 | 108篇 |
2012年 | 116篇 |
2011年 | 148篇 |
2010年 | 125篇 |
2009年 | 124篇 |
2008年 | 119篇 |
2007年 | 103篇 |
2006年 | 102篇 |
2005年 | 99篇 |
2004年 | 75篇 |
2003年 | 75篇 |
2002年 | 85篇 |
2001年 | 68篇 |
2000年 | 86篇 |
1999年 | 82篇 |
1998年 | 57篇 |
1997年 | 53篇 |
1996年 | 52篇 |
1995年 | 41篇 |
1994年 | 44篇 |
1993年 | 47篇 |
1992年 | 39篇 |
1991年 | 28篇 |
1990年 | 19篇 |
1989年 | 13篇 |
1988年 | 15篇 |
1987年 | 12篇 |
1986年 | 6篇 |
1985年 | 3篇 |
1984年 | 9篇 |
1983年 | 5篇 |
1976年 | 1篇 |
1973年 | 1篇 |
1954年 | 1篇 |
排序方式: 共有2616条查询结果,搜索用时 359 毫秒
51.
H. Sommer A. Kröner C. Hauzenberger S. Muhongo M. T. D. Wingate 《Journal of Metamorphic Geology》2003,21(9):915-934
New data on the metamorphic petrology and zircon geochronology of high‐grade rocks in the central Mozambique Belt (MB) of Tanzania show that this part of the orogen consists of Archean and Palaeoproterozoic material that was structurally reworked during the Pan‐African event. The metamorphic rocks are characterized by a clockwise P–T path, followed by strong decompression, and the time of peak granulite facies metamorphism is similar to other granulite terranes in Tanzania. The predominant rock types are mafic to intermediate granulites, migmatites, granitoid orthogneisses and kyanite/sillimanite‐bearing metapelites. The meta‐granitoid rocks are of calc‐alkaline composition, range in age from late Archean to Neoproterozoic, and their protoliths were probably derived from magmatic arcs during collisional processes. Mafic to intermediate granulites consist of the mineral assemblage garnet–clinopyroxene–plagioclase–quartz–biotite–amphibole ± K‐feldspar ± orthopyroxene ± oxides. Metapelites are composed of garnet‐biotite‐plagioclase ± K‐feldspar ± kyanite/sillimanite ± oxides. Estimated values for peak granulite facies metamorphism are 12–13 kbar and 750–800 °C. Pressures of 5–8 kbar and temperatures of 550–700 °C characterize subsequent retrogression to amphibolite facies conditions. Evidence for a clockwise P–T path is provided by late growth of sillimanite after kyanite in metapelites. Zircon ages indicate that most of the central part of the MB in Tanzania consists of reworked ancient crust as shown by Archean (c. 2970–2500 Ma) and Palaeoproterozoic (c. 2124–1837 Ma) protolith ages. Metamorphic zircon from metapelites and granitoid orthogneisses yielded ages of c. 640 Ma which are considered to date peak regional granulite facies metamorphism during the Pan‐African orogenic event. However, the available zircon ages for the entire MB in East Africa and Madagascar also document that peak metamorphic conditions were reached at different times in different places. Large parts of the MB in central Tanzania consist of Archean and Palaeoproterozoic material that was reworked during the Pan‐African event and that may have been part of the Tanzania Craton and Usagaran domain farther to the west. 相似文献
52.
U–Pb sensitive high resolution ion microprobe (SHRIMP) dating of zircons from charnockitic and garnet–biotite gneisses from the central portion of the Mozambique belt, central Tanzania indicate that the protolith granitoids were emplaced in a late Archaean, ca. 2.7 Ga, magmatic event. These ages are similar to other U–Pb and Pb–Pb ages obtained for other gneisses in this part of the belt. Zircon xenocrysts dated between 2.8 and 3.0 Ga indicate the presence of an older basement. Major and trace element geochemistry of these high-grade gneisses suggests that the granitoid protoliths may have formed in an active continental margin environment. Metamorphic zircon rims and multifaceted metamorphic zircons are dated at ca. 2.6 Ga indicating that these rocks were metamorphosed some 50–100 my after their emplacement. Pressure and temperature estimates on the charnockitic and garnet–biotite gneisses were obscured by post-peak metamorphic compositional homogenisation; however, these estimates combined with mineral textures suggest that these rocks underwent isobaric cooling to 800–850 °C at 12–14 kbar. It is considered likely that the granulite facies mineral assemblage developed during the ca. 2.6 Ga event, but it must be considered that it might instead represent a pervasive Neoproterozoic, Pan African, granulite facies overprint, similar to the ubiquitous eastern granulites further to the east. 相似文献
53.
A biostratigraphic study carried out in the Monti d'Ocre area, Abruzzi, Central Apennines, allowed us to recognize Orbitolina (Conicorbitolina) moulladei ‘Strata 5 (1985) 1’, Praealveolina iberica Reichel and Praealveolina simplex Reichel in uppermost Albian–lower Cenomanian shelf-edge deposits of the Fossato Machè succession. These foraminifers have now been found for the first time in the Apennines of central Italy; their finding is quite important from a palaeobiogeographic viewpoint, as it contributes to the improvement of our knowledge on facies distribution in the circum-Mediterranean regions during the Cretaceous Period. In the study area, the coeval Monte Rotondo and Monte Orsello sections also crop out; these are characterized by bauxite deposits and stratigraphic gaps reflecting episodes of emergence on the carbonate platform. The Monte Rotondo and Monte Orsello sections accumulated in a platform back-reef environment; consequently, in this sector of the Monti d'Ocre area, the depositional environment shifted from a back-reef westward and southward to a shelf-edge northward, during the latest Albian–early Cenomanian. Owing to synsedimentary tectonics, the area investigated underwent differential subsidence: westward and southward, wide areas were uplifted and subjected to emergence, karstification and bauxite accumulation, whereas sedimentation continued in a shelf-edge environment in the north-eastern area. 相似文献
54.
NafiM AbdullatifM 《中国地质大学学报(英文版)》2003,14(2):137-143
The sedimentology of the Northwestern Sudan consists of lower, middle and upper cycles. The lower and upper cycles are composed of intercalated fluvial and shallow marine facies, whereas the middle cycle consists entirely of fluvial and glaciofluvial facies. The petrographic analysis shows that the lower and upper cydes consist of quartz and lithic arenite sandstones, whereas the middle cycle consists of arkosic and lithic arenite sandstones. The lower and upper cycle sandstones reflect derivation mainly from recycled orogens with minor contribution from craton interior provenances. However, the middle cycle sandstones indicate derivation from basement uplift, transitional and mainly recycled orogens provenances. 相似文献
55.
楚雄盆地下侏罗统磨拉石楔沉积与含油性研究 总被引:1,自引:1,他引:1
楚雄盆地为一中生代周缘型走滑前陆盆地,通过对下侏罗统冯家河组沉积特征的详细研究与对比,作者认为早侏罗世是楚雄前陆盆地强烈坳陷与沉降的主要发展时期从早期到晚期经历了一个变深又变浅的典型前陆盆地充填过程。在前陆冲断块体的不断逆冲和加载条件下,楚雄盆地西部早侏罗世沉积物的来源主要为哀牢山造山带隆起,其沉积环境以滨,浅湖或湖泊三角洲为主。 相似文献
56.
碳酸盐与陆源碎屑的混合沉积研究至今尚未引起足够重视。文献屈指可数。扬子西经缘龙门山地区盆纪发育了了这类良好的混合沉积。作者根据实际材料,首次从这一思路出发,识别该区泥盆纪Emsian期到Givetian早期的混积相四种,混积亚相约14种,阐明了其优势混积作用;根据混积作用特征、沉积背景关系,划分出两大混积类型,即泥质背景下的混积1型和砂灰质背景下的混积Ⅱ型;对混积作用机理进行了探讨;并指出不同级次 相似文献
57.
本文系统地讨论了皖南地区晚二叠世早期沉积层发育特征,确定了龙潭期地层的顶、底界线。以单因素图件为基础,结合其它成因标志,编制了龙潭早期(三个亚期)和龙潭晚期岩相古地理图,由此可以看出龙潭期的岩相古地理特征及其演化历史 相似文献
58.
湘鄂赣二叠纪岩相古地理研究 总被引:4,自引:0,他引:4
湘鄂赣二叠纪沉积盆地是在华南陆块基础上发育而成,具有扬子克拉通北缘被动大陆边缘盆地,扬子克拉通盆地,湘赣板内拉张盆地和华夏克拉通边缘盆地等四类。根据古暴露等标志,建立了各类盆地的沉积层序,并进行了区域对比。 相似文献
59.
60.
Timing and exhumation of eclogite facies shear zones, Musgrave Block, central Australia 总被引:2,自引:0,他引:2
A. CAMACHO W. COMPSTON M. McCULLOCH & I. McDOUGALL 《Journal of Metamorphic Geology》1997,15(6):735-751
Timing constraints on shear zones can provide an insight into the kinematic and exhumation evolution of metamorphic belts. In the Musgrave Block, central Australia, granulite facies gneisses have been affected, to varying degrees, by mylonitic deformation, some of which attained eclogite facies. The Davenport Shear Zone is a dominant strike-slip system that formed at eclogite facies conditions ( T ≈650 °C and P ≈12.0 kbar). Sm–Nd mineral isochrons obtained from equilibrated high-pressure assemblages, as well as 40 Ar–39 Ar data, show that the eclogite and greenschist facies high-strain overprints were coeval, at c . 550 Ma. Mylonitic processes do not appear to have reset the U–Pb system in zircon, but may have partially disturbed it. The thermal gradient in the Musgrave Block crust at c . 550 Ma was c . 16 °C km−1 and at c . 535 Ma was c . 18 °C km−1 , based on P – T estimates of eclogite and greenschist facies shear zones, respectively. These estimates are similar to present-day geothermal gradients in many stable continental shield areas, suggesting that the region did not undergo a significant transient perturbation of the geotherm. Therefore, in the Musgrave Block, cooling subsequent to eclogite facies metamorphism appears to have been controlled by exhumation, rather than by the removal of a heat source. Estimated exhumation rates in the range 0.2 to ≥1.5 mm year−1 are comparable with other orogenic belts, rather than cratonic areas elsewhere. 相似文献