全文获取类型
收费全文 | 1786篇 |
免费 | 419篇 |
国内免费 | 719篇 |
专业分类
测绘学 | 122篇 |
大气科学 | 141篇 |
地球物理 | 304篇 |
地质学 | 1889篇 |
海洋学 | 115篇 |
天文学 | 17篇 |
综合类 | 137篇 |
自然地理 | 199篇 |
出版年
2024年 | 12篇 |
2023年 | 28篇 |
2022年 | 80篇 |
2021年 | 100篇 |
2020年 | 80篇 |
2019年 | 99篇 |
2018年 | 80篇 |
2017年 | 105篇 |
2016年 | 95篇 |
2015年 | 93篇 |
2014年 | 114篇 |
2013年 | 134篇 |
2012年 | 180篇 |
2011年 | 104篇 |
2010年 | 125篇 |
2009年 | 128篇 |
2008年 | 88篇 |
2007年 | 127篇 |
2006年 | 134篇 |
2005年 | 116篇 |
2004年 | 112篇 |
2003年 | 84篇 |
2002年 | 69篇 |
2001年 | 78篇 |
2000年 | 67篇 |
1999年 | 63篇 |
1998年 | 59篇 |
1997年 | 82篇 |
1996年 | 60篇 |
1995年 | 37篇 |
1994年 | 53篇 |
1993年 | 30篇 |
1992年 | 21篇 |
1991年 | 23篇 |
1990年 | 20篇 |
1989年 | 8篇 |
1988年 | 9篇 |
1987年 | 14篇 |
1986年 | 8篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1980年 | 1篇 |
排序方式: 共有2924条查询结果,搜索用时 15 毫秒
941.
《International Geology Review》2012,54(7):894-903
The Xiangshan volcanic-intrusive complex is composed of rhyolitic crystal tuffs, welded tuffs, rhyodacite, porphyroclastic rhyolitic lava, subvolcanic rocks such as granite porphyry, and late quartz monzonitic porphyry and lamprophyre dikes. We report the first occurrence of a quartz–amphibole schist (QAS) xenolith enclosed within a mafic microgranular enclave (MME) in the Xiangshan volcanic-intrusive complex. The mineralogy of this xenolith consists of amphibole, biotite, quartz, and minor plagioclase. Petrographic and mineral composition studies indicate that the protolith of this xenolith likely originated from the metamorphic basement beneath Xiangshan. The amphibole (actinolite and magnesiohorblende) has been partially replaced by orthopyroxene at 800–1000°C and by diopside at <700°C, according to mineral thermometers; this replacement process may have taken place after the xenolith was trapped by the mafic magma host (now an MME). Studies of the QAS xenolith provide new information on the emplacement history of the mafic magma. The peak metamorphic temperature for amphibole replaced by pyroxene is higher than the crystallization temperature of the subvolcanic magma, which indicates that the heat of pyroxene formation must have been provided by the engulfing mafic melt. This magma must have emplaced to crustal level and trapped the QAS as a xenolith and then injected into the felsic magma. We suggested that the hybridization processes for the major elements of the pristine mafic magma may have been contaminated by crustal rocks to form its present composition of MME before mafic magma injection. However, the hybridization process appears not to have been formed via a single-stage process because various types of MMEs are presented in the Mesozoic magmatic rocks of SE China. 相似文献
942.
《International Geology Review》2012,54(15):1941-1958
The Qiarbahete complex in NW China consists of gabbroic diorite, granodiorite, and late-stage quartz diorite porphyry veins. Zircon sensitive high-resolution ion microprobe (SHRIMP) U–Pb analyses show that the gabbroic diorite and granodiorite formed at 368 ± 5.2 Ma and 354 ± 4.1 Ma, respectively, indicating that the complex was emplaced in the Late Devonian–Early Carboniferous. The gabbroic diorites, characteristic of Sanukitoids, exhibit high Mg# (62 average), MgO (6.84% average), Cr (195 ppm average), and Ni (61.4 ppm average) contents. The rocks show moderately fractionated rare earth element (REEs) patterns and weak negative Eu anomalies (δEu: 0.83–0.89), enrichment of large ion lithophile elements (LILEs), and depletion of high field strength elements (HFSEs), with low ?Nd(t) values (1.46–1.73). The gabbroic diorites originated from partial melting of a hydrous mantle wedge followed by assimilation of crust during ascent. The granodiorites show a geochemical affinity with adakitic rocks, e.g. SiO2 (64.95–67.87%) > 56%, Al2O3 (15.88–16.56%) > 15%, MgO (1.79–2.31%) < 3%, Sr (315–375 ppm) > 300 ppm, and Yb (1.84–2.06 ppm). They are enriched in light rare earth elements (LREEs) and LILEs and depleted in HFSEs, with weak negative Eu anomalies (δEu: 0.78–0.87). The granodiorites were mainly derived by the partial melting of a subducted oceanic slab, followed by subsequent melt–mantle interaction and crustal rocks contamination. All these indicate that the Qiarbahete complex was emplaced in a continental arc setting attending the southward subduction of the Junggar Ocean during the Late Devonian–early Carboniferous, generating the lateral accretion of continental crust in NW Tianshan. 相似文献
943.
《International Geology Review》2012,54(16):2065-2066
ABSTRACTMetasedimentary rocks from the El Triunfo Complex (Jocote Unit) in the southern Chiapas Massif (SE México) are constituted mainly by sillimanite-rich micaschist, locally intercalated with marble and calc-silicate rocks. Mafic rocks (now amphibolite) intruded the sequence prior to deformation and folding. Peak metamorphic conditions are estimated by geothermobaromerty at ~6.0 kbar and ~650ºC. The timing of the metamorphic event is dated by LA-MC-ICPMS analysis on zircon rims at 438+23/–12 Ma. Furthermore, detrital zircon grains yield mainly Stenian–Tonian and minor early Mesoproterozoic ages, indicating provenance from Grenville-type orogens (such as Oaxaquia) and some older cratonic sources. The 87Sr/86Sr values of 0.70775–0.70777 and the δ13C values from +1.9‰ to +2.7‰ in associated calcite marble define the time of deposition between 600 and 580 Ma. Geochemical markers from metapelite samples (such as La/Th > 3.94, La/Sc > 3.72, Th/U > 8.19, Th/Co > 0.42 and CIA = 74 to 83), as well as Sm–Nd isotope data (εNdi = ?8.1 to ?4.0, TDM(Nd) = 1.65–1.32 Ga) suggest weathering of Mesoproterozoic felsic rocks during temperate to warm climate. Furthermore, Zr/Sc values (9.1–21.0), chondrite-normalized REE patterns [La/Yb]N = 10.3–23.3, Eu/Eu* < 0.64), and ΔHf values (1.98–10.02) are indicative of pelagic and zircon-depleted sediments of a passive margin. The results suggest that the Jocote Unit was deposited during the opening of the Eastern Iapetus Ocean in the Ediacaran Period. This is the first evidence for Rodinia breakup in southern México. Besides that, the Ordovician tectonothermal event is probably related to compression during subduction and accretion along the western margin of Gondwana. 相似文献
944.
简述了河北省迁安市红山铁矿详查矿区地层坚硬、破碎等复杂特点和地层的岩性情况,总结了该矿区破碎复杂地层绳索取心钻探施工技术经验,着重从钻孔结构、钻具及钻进参数选择和冲洗液选取与配制方面分析了破碎漏失、坍塌掉块及坚硬"打滑"地层的处理方法,阐述了保证复杂地层岩心采取率和预防钻孔倾斜的技术措施。通过护壁堵漏、改进冲洗液的配比、调整钻头的胎体硬度,改善了复杂地层的钻进环境,提高了钻探生产效率。 相似文献
945.
946.
947.
948.
复地震道技术采用Hilbert变换通过求解实地震信号的解析信号,可将反映地震信号局部变化情况的地震波的瞬时振幅、瞬时相位和瞬时频率等信息分离开,瞬时相位是一种独立于地震振幅,并且不受其影响的地震属性参数,因此瞬时相位能更好地反映构造几何形态的细节.通过理论模型分析发现,瞬时振幅与极性反转前后地震记录的瞬时相位一阶差分之和进行加权,得到的复合属性可以较为准确、可靠地识别地震反射界面的位置,具有较好的应用效果. 相似文献
949.
江浪穹隆是扬子地台西缘变质核杂岩带中比较典型的一个变质核杂岩体,具有良好的成矿物理化学条件,以存在一
系列铜硫化物矿床而著称。中咀铜矿的成矿作用表现出多期次、多成因的特点,其成矿与江浪变质核杂岩的形成和演化有
着密切的成因联系。本文应用构造解析方法, 对江浪穹隆北部的中咀铜矿进行了构造解析和成矿规律研究。通过野外构造
解析,结合相关同位素测年资料,初步确定中咀铜矿含矿岩系经历至少6 个世代的构造变形,并认为矿体主要受华力西期
顺层韧性剪切带和燕山期成穹过程中形成的重力滑脱带控制,本文从矿源、热源、成矿元素活化、增生富集和成矿空间等
方面探讨了其成矿过程和矿床成因,建立了中咀铜矿的成矿模式,对在江浪变质穹窿周缘寻找同类型矿体指出了明确的层
位和构造部位,指明了下一步重点找矿方向。 相似文献
950.
苦子干碱性杂岩体是塔什库尔干新生代碱性岩带的主要组成之一,主要由霓辉正长岩、石英霓辉正长岩和碱性花岗岩组成。霓辉正长岩、石英霓辉正长岩和碱性花岗岩的SiO2含量差别较大,分别为50.26%~54.11%、59.74%~60.43oA、69.59%~72.13%;霓辉正长岩与石英霓辉正长岩的里特曼指数相近,分别为7.83~10.97、8.51~9.05,明显不同于碱性花岗岩(2.49~3.71)。这3种碱性岩石都表现出富集轻稀土,以及K、Rb、Sr、Ba等大离子亲石元素(LILE),亏损Nb、Ta、Ti等高场强元素(HFSE)的特征。其中异常高的Sr、Ba和∑REE含量暗示可能还有富集地幔物质的加入。利用原位锆石LA—ICP—MS同位素测试方法,获得石英霓辉正长岩和碱性花岗岩的锆石U—Pb年龄分别为10.9±0.1Ma和11.9土0.4Ma,代表了岩石的结晶年龄;石英霓辉正长岩锆石εHf(t)值为-9.78~3.24,碱性花岗岩中锆石εHf(t)值为-13.54~5.78,均显示岩浆源区具有壳幔混合的特点。依据这些资料,并结合区域地质研究的综合分析,笔者初步提出西昆仑塔什库尔干苦子干碱性杂岩体的形成是由于青藏高原在~25Ma期间主体拆沉作用发生后,造成软流圈物质向北逃逸,并受到北面塔里木克拉通岩石圈山根阻挡而上涌,进而发生壳幔混合作用的产物。因此,该杂岩体是青藏高原大规模拆沉后浆活动的远程效应,且标志着研究区在~11Ma期间已处于伸展构造背景。 相似文献