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991.
受冲击石英砂岩碎屑分析 总被引:2,自引:0,他引:2
利用二级轻气炮将6mm直径的钢球加速到5~7km/s后撞击石英砂岩靶,利用磁性分选,扫描电镜和X射线衍射等方法对嵌靶受击后形成碎屑进行了矿物分类和鉴别,碎屑主要由石英,高硅玻璃,微量柯石英以及铁碎屑,微细钢球等组成,70%的碎屑分布在0.097~0.90mm范围内,无一弱磁性碎屑约占总重量的92%,其它为强磁性碎屑。 相似文献
992.
The Dongping gold deposit, situated on the northern margin of the North China Platform, is a composite deposit composed of
auriferous quartz vein-type and altered rock-type ore bodies. It is hosted in the inner contact zone of an alkaline intrusion
which was intruded into Archean metamorphic rocks and was formed not later than the Hercynian period. Auriferous quartz veins
of the deposit are dated with the fluid inclusion Rb-Sr isochron method at 103 ± 4 Ma, indicating that the gold deposit was
formed in the Yenshanian period.87Sr/86Sr sourcetracing shows the ore forming materials came dominantly from alkaline intrusions. These results, combined with other
isotope and REE data, suggest that the Dongping gold deposit is not a traditional magmatic hydrothermal deposit, but a reworked
hydrothermal deposit related to heated and evolved meteoric water.
This project (49372105) is financially supported by the National Natural Science Foundation of China. 相似文献
993.
The Thermal History of the Huangmeijian Granite Intrusion in Anhui and Its Relation to Mineralization: Isotopic Evidence 总被引:3,自引:0,他引:3
Zheng Yongfei Fu Bin Gong Bing Department of Earth Space Sciences University of Science Technology of Chin Hefei Liu Xinzhu 《《地质学报》英文版》1996,70(2)
Whole-rock Rb-Sr, zircon U-Pb and hornblende, biotite and K-feldspar K-Ar ages areused to reconstruct the cooling history of the Huangmeijian intrusion in the Anqing-Lujiangquartz-syenite belt in Anhui. Oxygen isotope geothermometry of mineral pairs demonstrates thatdiffusion is a dominant factor controlling the closure of isotopic systems. Assuming the coolingof the intrusion is synchronous with a dicrease in local geothermal gradients, an emplacementdepth of about 8 km and the magma crystallization temperature of 800±50℃ are estimated. TheHuangmeijian intrusion experienced a rapid cooling process and uplifted after its emplacementand crystallization at 133 Ma B.P. with a cooling rate of 34.5℃/Ma and an uplifting rate of 0.35mm/a. The intrusion was rising until it rested at a depth of 3km at a temperature of 300±50℃about 14 Ma later. Then the intrusion was in slow cooling and uplifting with a cooling rate of4.4℃/Ma and an uplifting rate of 0.04 mm/a. U-Pb dating of pitchblende is done for the hydrothermal uranium deposit formed in thecontact zone of the Huangmeijian intrusion. The result shows that the mineralization age is closeto the closing time of the K-Ar system in biotite. The fluid inclusion thermometry indicates thatthe mineralization temperature is in agreement with the closure temperature of the biotite K-Arsystem. This suggests a close relationship between the slow cooling of the intrusion and thehydrothermal uranium mineralization process. 相似文献
994.
金矿石英脉K-Ar年龄测定 总被引:4,自引:0,他引:4
本文从不同地质时代含金石英脉中选取石英进行了K-Ar年龄实验研究,认为石英是含微量钾的矿物。Ar的析出曲线呈“马鞍型”,显示含过剩40Ar。几个石英K-Ar年龄实测结果均含过剩40Ar,其表面年龄无地质年代学意义。 相似文献
995.
Grain-boundary migration of quartz during annealing experiments at high temperatures and pressures, with implications for metamorphic geology 总被引:4,自引:0,他引:4
Annealing experiments on agate, quartz schist and metachert at 800–1000 °C, confining pressures of 400 and 800 MPa, and annealing times of 6.0×10–3.6×105 s revealed normal grain growth of quartz in the agate, grain-size increasing with time, but the rate of grain growth decreasing with increasing grain size.
The boundaries of agate with quartz schist and metachert migrated into the agate at the expense of fine-grained quartz in the agate. The driving force for the migration appears to be the reduction of surface energy associated with removal of fine-grained quartz in the agate. Assuming the activation energy as Q m =11 kcal mol−1 , a general expression for the relationship between velocity of boundary migration ( V ) and driving force ( P ) is where γ is the specific surface energy of quartz, R is the gas constant and T is the absolute temperature. The velocity is relatively fast at high temperatures on a geological time-scale. The expression assists a quantitative understanding of the microstructural development of quartz at metamorphic conditions. 相似文献
The boundaries of agate with quartz schist and metachert migrated into the agate at the expense of fine-grained quartz in the agate. The driving force for the migration appears to be the reduction of surface energy associated with removal of fine-grained quartz in the agate. Assuming the activation energy as Q
996.
997.
南极无冰区古海蚀龛石英颗粒表面结构特征及其环境意义 总被引:9,自引:0,他引:9
石英砂表面结构特征组合能指示沉积物的搬运历史和沉积环境。利用电镜扫描方法分析了南极法尔兹半岛上海蚀成因的古海蚀龛沉积物中的石英砂表面结构特征组合。结果表明,在所有的石英砂表面上均表现出冰川和水流共同作用的结构特征组合,龛中沉积物是冰水沉积环境下的产物,在沉积过程中,沉积物先经过较薄的冰川搬运,后经历了不同能量的流水改造作用,但冰川和流水的搬运距离有限。上述研究结果表明,南极法尔兹半岛上的冰盖解体并退出长城站区的时间应早于4600aBP。 相似文献
998.
999.
Francisco A. Jimenez Jr Graciano P. Yumul Jr Victor B. Maglambayan 《Resource Geology》2007,57(2):170-179
The Sibutad gold deposit has gold associated in quartz veins. The most important of these is the Lalab orebody, which contains ore‐grade gold, predominantly, in milky quartz veins and veinlets. Here, alteration quartz and fine‐grained crystalline clear and milky quartz were formed from hydrothermal fluids in three stages, namely stages I, II and III. Fluid inclusion microthermometry was carried out on stage I milky quartz, stage II fine‐grained alteration quartz and stage III milky quartz ± barite veins and veinlets. Homogenization temperatures (TH) are >248°C in stage I, 214–232°C in stage II and 186–239°C in stage III. These fluid inclusions have salinity between 1 and 2 wt% NaCl equivalent. In terms of gold assay, stage I drill‐core samples have gold grades 0.53–0.76 g/ton Au, stage II samples have 1.12–3.70 g/ton Au and stage III samples have 9.06–23.88 g/ton Au. This correlation suggests that gold was precipitated from the stage II and III fluids. 相似文献
1000.
Clinopyroxene + plagioclase (±Hbl ± Qtz) symplectites after omphacite are widely cited as evidence for prior eclogite-facies
or high-pressure (HP) metamorphism. Precursor omphacite compositions of retrograde eclogites, used for reconstructing retrograde
P–T paths, are commonly estimated by reintegrating symplectite phases with the assumption that the symplectite-forming reactions
were isochemical. Comparisons of broadbeam symplectite compositions to adjacent unreacted pyroxene from various symplectites
after clinopyroxene from the Appalachian Blue Ridge (ABR) and Western Gneiss Region (WGR) suggest that the symplectite forming
reactions are largely isochemical. Endmember calculations based on reintegrated symplectite compositions from the ABR and
WGR suggest that a minor Ca-Eskola (CaEs) component (XCaEs = 0.04–0.15) was present in precursor HP clinopyroxene. WGR symplectites consist of fine-grained (∼1 μm-scale), vermicular
intergrowths of Pl + Cpx II ± Hbl that occur at grain boundaries or internally. ABR symplectites contain coarser (∼10 μm-scale)
planar lamellae and rods of Pl + Cpx II + Qtz + Hbl within clinopyroxene cores. The contrasting textures correlate with decompression
and cooling rate, and degree of overstepping of the retrograde reaction (lamellar: slow, erosionally controlled exhumation
with slow/low overstepping; fine-grained, grainboundary symplectite: rapid, tectonic exhumation with rapid/high overstepping).
Variations in XCaEs, Xjd, and XCaTs of precursor HP omphacite are related to the symplectic mineral assemblages that result from decompression. Quartz-normative
symplectities indicate quartz-producing retrograde reactions (e.g., breakdown of precursor CaEs); quartz-free symplectities
(e.g., diopside + plagioclase after omphacite) indicate quartz-consuming reactions (jd, CaTs breakdown) outpaced quartz-producing
reactions.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献