全文获取类型
收费全文 | 2182篇 |
免费 | 580篇 |
国内免费 | 525篇 |
专业分类
测绘学 | 3篇 |
地球物理 | 137篇 |
地质学 | 2845篇 |
海洋学 | 180篇 |
综合类 | 80篇 |
自然地理 | 42篇 |
出版年
2024年 | 12篇 |
2023年 | 35篇 |
2022年 | 43篇 |
2021年 | 67篇 |
2020年 | 75篇 |
2019年 | 78篇 |
2018年 | 85篇 |
2017年 | 85篇 |
2016年 | 109篇 |
2015年 | 93篇 |
2014年 | 141篇 |
2013年 | 139篇 |
2012年 | 133篇 |
2011年 | 170篇 |
2010年 | 146篇 |
2009年 | 144篇 |
2008年 | 126篇 |
2007年 | 141篇 |
2006年 | 131篇 |
2005年 | 124篇 |
2004年 | 107篇 |
2003年 | 113篇 |
2002年 | 110篇 |
2001年 | 100篇 |
2000年 | 113篇 |
1999年 | 105篇 |
1998年 | 79篇 |
1997年 | 77篇 |
1996年 | 65篇 |
1995年 | 61篇 |
1994年 | 55篇 |
1993年 | 53篇 |
1992年 | 47篇 |
1991年 | 35篇 |
1990年 | 20篇 |
1989年 | 14篇 |
1988年 | 15篇 |
1987年 | 12篇 |
1986年 | 6篇 |
1985年 | 3篇 |
1984年 | 10篇 |
1983年 | 7篇 |
1976年 | 1篇 |
1973年 | 1篇 |
1954年 | 1篇 |
排序方式: 共有3287条查询结果,搜索用时 0 毫秒
991.
鲁西南石炭二叠纪煤系潮坪沉积体系与聚煤作用 总被引:2,自引:0,他引:2
鲁西南石炭二叠纪煤系形成于内陆表海盆地。潮坪沉积体系是研究区聚时重要的沉积体系之一。作者详细研究了潮坪沉积体系的内部构成、成因相及各种沉积体发育特点,分析了沉积组合类型及其成因单元,论述了潮坪沉积体系的聚煤特点及富单元的形成与分布规律。 相似文献
992.
993.
994.
大别山北部榴辉岩的大地构造属性及冷却史 总被引:12,自引:0,他引:12
岩石地球化学及同位素年代学研究表明,大别山北部榴辉岩的大部分属印支期扬子俯冲陆壳(下地壳)的一部分;大致沿磨子潭-晓天断裂附近分布的含榴辉岩、大理岩和变质橄榄岩的镁铁-超镁失质岩带可能代表扬子与华北2个大陆板块之间的变质构造混杂岩带,它应接近于扬子与华北2个大陆板块之间的缝合线(镁铁-超镁铁质岩带以北),而五河-水吼剪切带则可能代表扬子腐冲陆壳内部的1条拆离带或滑脱带。冷却史研究表明,大别山北部榴辉岩峰期变质后初期(230-210Ma)仅抬升到下地壳水平,因而未经历降温过程并具有比大别山南部榴辉岩较低的抬升速率,峰期变质后较慢的抬升速率及相应的近于等温或局部升温阶段也许是造成大别山北部榴辉岩与南部超高压带中榴辉岩差异的重要原因之一;同时,也许是研究区榴辉岩很少见有保留早期超高压变质证据的重要原因。 相似文献
995.
Spatially-focussed melt formation in aluminous metapelites from Broken Hill, Australia 总被引:6,自引:1,他引:6
Large garnet poikiloblasts hosted by leucosome in metapelitic gneiss from Broken Hill reflect complex mineral–melt relationships. The spatial relationship between the leucosomes and the garnet poikiloblasts implies that the growth of garnet was strongly linked to the production of melt. The apparent difficulty of garnet to nucleate a large number of grains during the prograde breakdown of coexisting biotite and sillimanite led to the spatial focussing of melting reactions around the few garnet nuclei that formed. Continued reaction of biotite and sillimanite required diffusion of elements from where minerals were reacting to sites of garnet growth. This diffusion was driven by chemical potential gradients between garnet‐bearing and garnet‐absent parts of the rock. As a consequence, melt and peritectic K‐feldspar also preferentially formed around the garnet. The diffusion of elements led to the chemical partitioning of the rock within an overall context in which equilibrium may have been approached. Thus, the garnet‐bearing leucosomes record in situ melt formation around garnet porphyroblasts rather than centimetre‐scale physical melt migration and segregation. The near complete preservation of the high‐grade assemblages in the mesosome and leucosome is consistent with substantial melt loss. Interconnected networks between garnet‐rich leucosomes provide the most likely pathway for melt migration. Decimetre‐scale, coarse‐grained, garnet‐poor leucosomes may represent areas of melt flux through a large‐scale melt transfer network. 相似文献
996.
Phengites in ecologites of the Dabieshan region can be divided into three enerations:primary phengite formed during ecologite-facies prograde metamorphism(Phel),phengite formed during the late stage of eclogite-facies retrograde metamorphism(Phe2)and phengite formed during amphibolite-to greenschist-facies diaphthoresis(Phe3).Electron microprobe analyses show that the Si and Fe^2 Mg contents of Phel are unexpectedly lower than those of Phe3.Therefore,much caution should be exerciesed while using the Si content of phengite to estimate the pressure of a retrograde process. 相似文献
997.
Fractionation of bulk rock composition due to porphyroblast growth: effects on eclogite facies mineral equilibria, Pam Peninsula, New Caledonia 总被引:16,自引:2,他引:16
Chemically zoned porphyroblasts in metamorphic rocks indicate that diffusional processes could not maintain equilibrium conditions on a grain scale during porphyroblast growth or establish it afterwards. An effect of this inability to maintain equilibrium is the progressive removal of elements forming garnet cores from any metamorphic reaction that occurs at the porphyroblast boundaries or in the matrix of the rock. To examine this effect on mineral assemblages, the Bence–Albee matrix correction was applied to X‐ray intensity maps collected using eclogite samples from northern New Caledonia in order to determine the chemical composition of all parts of the sample. The manipulation of these element maps allows a quantitative analysis of the fractionation of the bulk rock composition between garnet cores and the matrix. A series of calculated equilibrium‐volume compositions represents the change in matrix chemistry with progressive elemental fractionation as a consequence of prograde garnet growth under high‐P conditions. Pressure–temperature pseudosections are calculated for these compositions, in the CaO–Na2O–FeO–MgO–Al2O3–SiO2–H2O system. Assemblages, modal proportions and mineral textures observed in the New Caledonian eclogites can be closely modelled by progressively ‘removing’ elements forming garnet cores from the bulk rock composition. The pseudosections demonstrate how chemical fractionation effects the peak metamorphic assemblage, prograde textures and the development of retrograde assemblages. 相似文献
998.
999.
Donna L. Whitney Christian Teyssier Seth C. Kruckenberg Valerie L. Morgan Lindsay J. Iredale 《Lithos》2008,101(3-4):218-232
Kilometer-scale lenses of quartz-rich metasedimentary rocks crop out in a discontinuous belt along the southern margin of the Menderes Massif, Turkey, and preserve evidence for high-pressure–low-temperature (HP–LT) metamorphism related to subduction of a continental margin during Alpine orogeny. Kyanite schist, quartzite, and quartz veins contain kyanite + phengite + Mg-chlorite, and the veins also contain magnesiocarpholite. A deformed carbonate metaconglomerate juxtaposed with the quartzite-dominated unit does not contain HP index minerals, and likely represents the tectonized boundary of the siliceous rocks with adjacent marble. The HP–LT rocks (10–12 kbar, 470–570 °C) record different pressure conditions than the adjacent, apparently lower pressure Menderes metasedimentary sequence. Despite this difference there is disagreement as to whether these HP–LT rocks are part of the Menderes sequence or are related to the tectonically overlying Cycladic blueschist unit. If the former, the entire southern Menderes Massif experienced HP–LT metamorphism but the evidence has been obliterated from most rocks; if the latter, rocks recording different metamorphic-kinematic conditions experienced different tectonic histories and were tectonically juxtaposed during thrusting. Based on observations and data in this study, the second model better accounts for the differences in P–T-deformation histories of the southern Menderes Massif rocks, and suggests that the HP–LT rocks are not part of the Menderes cover sequence. 相似文献
1000.
西藏拉萨地体榴辉岩的地球化学特征和Sm-Nd、Rb-Sr同位素组成及其地质意义 总被引:2,自引:0,他引:2
最近在青藏高原拉萨地体新发现了一条榴辉岩带,该榴辉岩带位于冈底斯岩浆岛弧带的北缘。对该带榴辉岩的岩石地球化学特征及SmNd、RbSr同位素组成研究表明: ① 该带榴辉岩的原岩主要是一套低钾的大洋拉斑系列玄武岩,其原岩类似于典型的NMORB,源于亏损地幔; ② 该带榴辉岩样品 (87Sr/86Sr)i=0.70335~0.70457,变化范围较大,且与εNd(t)值及微量元素特征均没有好的对应关系,可能是由于该套岩石形成于大洋环境,形成后遭受了海水的蚀变作用;(3)该带榴辉岩全岩的SmNd等时线年龄为305.5±50Ma (2σ),(143Nd/144Nd)i=0.5126±0.00007 (2σ),表明该带榴辉岩可能形成于早石炭-晚二叠世,在这一时期冈底斯北缘可能存在古特提斯洋盆及古特提斯洋盆深俯冲作用。 相似文献