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121.
In recent years, Māori and wider indigenous geographies have flourished. These include works by scholars identifying specific Māori or indigenous issues but less attention has been paid to the way such research is conducted. This paper engages with these developments and presents the practices and lessons learnt from one particular research collaboration. Relationship building, multiple methods, flexibility, communication choices and wider support are all noted as key elements in establishing a supportive and fruitful collaboration. 相似文献
122.
Morphostructure and evolution of the central and Eastern Bransfield Basins (NW Antarctic Peninsula) 总被引:2,自引:0,他引:2
Eulàlia Gràcia Miquel Canals Marcel Lí Farràn Maria José Prieto Jordi Sorribas Gebra Team 《Marine Geophysical Researches》1996,18(2-4):429-448
The Bransfield Basin is a narrow and elongated active rift basin located between the Antarctic Peninsula and the South Shetland Islands. The Bransfield Basin is composed of three small basins, and two of them, the Central and Eastern Bransfield Basins, were surveyed during a recent cruise (GEBRA 93). The full swath bathymetry coverage as well as the single-channel seismic reflection and magnetic profiles that have been acquired, help us to better understand the morphostructure and recent evolution of the Bransfield Basin. Six large volcanic edifices aligned with the basin axis stick out of the sedimented seafloor of the Central Bransfield Basin. In contrast, the Eastern Bransfield Basin is characterised by four deep troughs displaying a rhombic-shape, and small, scattered volcanic cones located in the southwestern half basin. Seamount volcanism plays an important role in the formation of new crust in the Bransfield Basin. The larger seamounts of the Central Bransfield Basin are located at the intersection of the two main orthogonal sets of faults (longitudinal ENE-WSW and transversal NNW-SSE). Morphological analysis of the seamounts indicates a multi-staged volcano-tectonic construction. The distribution and shape of these edifices suggests that both volcanism and extension are concentrated at the same preferential areas through time. This might be related to the fracturation style of the continental crust. The Central and Eastern Bransfield Basins are very different in morphostructure, volcanism, and sedimentary cover. The Central Bransfield Basin shows evidence of NW-SE extensional faulting and focused active MORB-volcanism interpreted as result of incipient seafloor spreading. The Eastern Bransfield Basin is still in a rifting stage, mainly dominated by a NW-SE extension and some left-lateral strike-slip component probably related to the South Scotia Ridge.J. Acosta, J. Baraza, P. Bart, A.M. Calafat, J.L. Casamor, M. De Batist, G. Ercilla, G. Francés, E. Ramos, J.L. Sanz, and A. Tassone. 相似文献
123.
Led by the National Solar Observatory, plans have been made to design and to develop the Advanced Technology Solar Telescope (ATST). The ATST will be a 4‐m general‐purpose solar telescope equipped with adaptive optics and versatile post‐focus instrumentation. Its main aim will be to achieve an angular resolution of 0.03 arcsec (20 km on the solar surface). The project and the telescope design are briefly described. 相似文献
124.
Connecteur WG Think‐Tank Team Jo?o Pedro Nunes John Wainwright Charles L. Bielders Frédéric Darboux Peter Fiener David Finger Laura Turnbull 《地球表面变化过程与地形》2018,43(6):1355-1360
Water‐ and sediment‐transfer models are commonly used to explain or predict patterns in the landscape at scales different from those at which observations are available. These patterns are often the result of emergent properties that occur because processes of water and sediment transfer are connected in different ways. Recent advances in geomorphology suggest that it is important to consider, at a specific spatio‐temporal scale, the structural connectivity of system properties that control processes, and the functional connectivity resulting from the way those processes operate and evolve through time. We argue that a more careful consideration of how structural and functional connectivity are represented in models should lead to more robust models that are appropriate for the scale of application and provide results that can be upscaled. This approach is necessary because, notwithstanding the significant advances in computer power in recent years, many geomorphic models are still unable to represent the landscape in sufficient detail to allow all connectivity to emerge. It is important to go beyond the simple representation of structural connectivity elements and allow the dynamics of processes to be represented, for example by using a connectivity function. This commentary aims to show how a better representation of connectivity in models can be achieved, by considering the sorts of landscape features present, and whether these features can be represented explicitly in the model spatial structure, or must be represented implicitly at the subgrid scale. Copyright © 2017 John Wiley & Sons, Ltd. 相似文献
125.
INDEPTH-Ⅲ地震层析成像--藏北印度岩石圈俯冲断落的证据 总被引:9,自引:2,他引:9
德庆-龙尾错剖面层析速度结构剖面揭示了在高原地壳发生缩短与增厚后,高速的印度大陆地幔岩石圈分为两层以不同角度向北伸展到(美)塘盆地的中部(33°N~34°N之间).上层在拉萨地块岩石圈(速度为7.9~8.0 km/s)之下向北伸展过程中发生断裂,形成若T断块,并下沉;下层以较大角度向北俯冲下去,并在32°N之下进人软流圈;发现北部有一浅一深2条低速带,可能代表地幔内温度较高的热流体的流动通道,并产生强烈的各向异性.浅处低速带与深部低速带有联系;此低速带与东部Wittlinger发现的34.5°N深部的高温低速体没有直接联系,后者呈NV-SE走向. 相似文献
126.
南岭东段赣南地区天门山花岗岩体及花岗斑岩脉的SHRIMP定年及其意义 总被引:16,自引:5,他引:11
赣南地区岩浆岩分布广泛,其中燕山期岩浆活动最为强烈,与W、Sn、Nb、Ta成矿的关系尤为密切。选择天门山岩体及附近的花岗斑岩脉为研究对象,应用SHRIMP锆石微区U-Pb测年技术,对天门山岩体的主体、补体和花岗斑岩脉进行了精确测年:天门山岩体的主体——中细粒斑状黑云母花岗岩锆石的9个点SHRIMP谐和年龄为152±2Ma(MSWD=1.09);补体——细粒斑状黑云母花岗岩锆石的5个点SHRIMP谐和年龄为152±2.6Ma(MSWD=0.16);花岗斑岩(墙)脉锆石10个点的SHRIMP谐和年龄为150.8±1.8Ma(MSWD=1.6)。结合区域资料,研究表明:①天门山岩体的主体形成于中侏罗世,补体是主体进一步分异演化的产物;②在赣南西部的崇余犹矿集区内成岩与成矿的年龄基本上是协调一致的,成矿集中期为150~155Ma;③岩浆活动由中深成相花岗岩侵入体演化到浅成相花岗斑岩脉仅相差1~5Ma,表明存在成矿集中期。 相似文献
127.
新疆玛因鄂博断裂带中花岗质糜棱岩锆石U-Pb SHRIMP和黑云母40Ar-39Ar年龄及意义 总被引:14,自引:0,他引:14
玛因鄂博断裂带具有左型剪切活动特征,分布其中的花岗质糜棱岩呈脉状、条带状产出,展布方向与剪切拉伸方向一致,为同构造花岗岩。其岩石化学为高钾钙碱性系列,属后碰撞“I”型花岗岩;稀土元素含量较高,ΣREE为(239.14~266.31)×10-6;具有中等程度的铕负异常,δEu为0.45~0.66,轻稀土明显富集。其锆石U-PbSHRIMP年龄为281±4Ma,黑云母40Ar-39Ar等时线年龄为236.1±1.2Ma。二者分别代表岩石的侵入年龄和后期的剪切变形年龄。其形成与早二叠世区域性大规模剪切活动有关,而黑云母40Ar-39Ar等时线年龄代表中三叠世早期的剪切变形活动。结合前人资料分析,玛因鄂博断裂的剪切活动持续时间较长,高峰期可能为290~270Ma,而其最后结束时间为230Ma左右。 相似文献
128.
川西北马脑壳金矿床流体包裹体研究及对成矿条件的制约 总被引:8,自引:1,他引:7
川西北的马脑壳金矿床为一赋存于三叠系碎屑岩、碳酸盐岩系的大型微细浸梁型金矿床,通过详细野外地质调查和室内综合研究,可将矿床的热液成矿作用划分为四个阶段,应用均一法测得:I、II、III、IV阶段的成矿温度分别为175~230℃,179~255℃,157~207℃,120~200℃,峰值分别为190~210℃,200~230℃,170~190℃,130~170℃,盐度变化范围,I、II、III、IV 相似文献
129.
S.J. Ostro L.C. Wye M.A. Janssen K. Kelleher R.A. Boehmer Y. Gim W.T.K. Johnson R.D. Lorenz the Cassini RADAR Team 《Icarus》2010,206(2):498-506
Cassini radar tracks on Saturn’s icy satellites through the end of the Prime Mission in 2008 have increased the number of radar albedo estimates from 10 (Ostro et al., 2006) to 73. The measurements sample diverse subradar locations (and for Dione, Rhea, and Iapetus almost always use beamwidths less than half the target angular diameters), thereby constraining the satellites’ global radar albedo distributions. The echoes result predominantly from volume scattering, and their strength is thus strongly sensitive to ice purity and regolith maturity. The combination of the Cassini data set and Arecibo 13-cm observations of Enceladus, Tethys, Dione, Rhea (Black et al., 2007), and Iapetus (Black et al., 2004) discloses an unexpectedly complex pattern of 13-to-2-cm wavelength dependence. The 13-cm albedos are generally smaller than 2-cm albedos and lack the correlation seen between 2-cm and optical geometric albedos. Enceladus and Iapetus are the most interesting cases. We infer from hemispheric albedo variations that the E-ring has a prominent effect on the 13-cm radar “lightcurve”. The uppermost trailing-side regolith is too fresh for meteoroid bombardment to have developed larger-scale heterogeneities that would be necessary to elevate the 13-cm radar albedo, whereas all of Enceladus is clean and mature enough for the 2-cm albedo to be uniformly high. For, Iapetus, the 2-cm albedo is strongly correlated with optical albedo: low for the optically dark, leading-side material and high for the optically bright, trailing-side material. However, Iapetus’ 13-cm albedo values show no significant albedo dichotomy and are several times lower than 2-cm values, being indistinguishable from the weighted mean of 13-cm albedos for main-belt asteroids, 0.15 ± 0.10. The leading side’s optically dark contaminant must be present to depths of at least one to several decimeters, so 2-cm albedos can mimic the optical dichotomy; however, it does not have to extend any deeper than that. The fact that both hemispheres of Iapetus look Asteroid-like at 13 cm means that coherent backscattering itself is not nearly as effective as it is at 2 cm. Since Iapetus’ entire surface is mature regolith, the wavelength dependence must involve composition, not structure. Either the composition is a function of depth everywhere (with electrical loss much greater at depths greater than a decimeter or two), or the intrinsic electrical loss of some pervasive constituent is much higher at 13 cm than at 2 cm. Ammonia is a candidate for such a contaminant. If ammonia’s electrical properties do not depend on frequency, and if ammonia is globally much less abundant within the upper one or two decimeters than at greater depths, then coherent backscattering would effectively be shut down at 13 cm, explaining the Asteroid-like 13-cm albedo. 相似文献
130.
Frédéric Schmidt Bernard Schmitt Francois Forget Patrick Martin Jean-Pierre Bibring the OMEGA Team 《Planetary and Space Science》2010,58(10):1129-1138
The polar condensation/sublimation of CO2, that involve about one fourth of the atmosphere mass, is the major Martian climatic cycle. Early observations in visible and thermal infrared have shown that the sublimation of the Seasonal South Polar Cap (SSPC) is not symmetric around the geographic South Pole.Here we use observations by OMEGA/Mars Express in the near-infrared to detect unambiguously the presence of CO2 at the surface, and to estimate albedo. Second, we estimate the sublimation of CO2 released in the atmosphere and show that there is a two-step process. From Ls=180° to 220°, the sublimation is nearly symmetric with a slight advantage for the cryptic region. After Ls=220° the anti-cryptic region sublimation is stronger. Those two phases are not balanced such that there is 22% ± 9 more mass the anti-cryptic region, arguing for more snow precipitation. We compare those results with the MOLA height measurements. Finally we discuss implications for the Martian atmosphere about general circulation and gas tracers, e.g. Ar. 相似文献