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411.
412.
黄旗海湖泊沉积记录的早中全新世大湖期环境的差异性 总被引:2,自引:0,他引:2
内蒙古黄旗海H6剖面揭示了最近间冰期古湖泊涨缩的一个完整旋回。基于OSL年代、粒度并结合沉积物地球化学等数据,分析了黄旗海在早、中全新世(约(11.4±1.1~6.7±0.7)ka)大湖期指标记录特点与环境意义。研究认为黄旗海全新世大湖期可分为三个阶段:1)(11.4±1.1~9.3±0.9) ka BP,半深水环境、湖水盐度低、流域存在有利于化学风化的湿润气候条件;2)(9.3±0.9~7.7±0.7) ka BP,湖水变浅、湖泊萎缩、湖泊盐度升高,流域可能存在不利于化学风化的干燥气候;3)(7.7±0.7~6.7±0.7) ka BP,大湖期结束,指标记录存在剧烈波动,揭示气候具有宽幅震荡特征。同时,研究初步认为Mn/Li比值可以作为流域化学风化的指标指示。 相似文献
413.
以五道梁地区1∶20万水系沉积物测量更新数据为基础,以渐新统雅西错组为研究对象,利用地层汇水域水系沉积物测量元素原始数据进行了参数统计,通过相对丰度、R型聚类分析和因子分析,分析了地层中各元素的含量分布特征及元素间的亲疏关系,进一步浅析了地层在成矿中的作用.认为雅西错组高钙碳酸盐岩建造环境显著,Ba、Sr、Ag、As、Cd、Mo在地层中有不同程度的富集.地层有一定的含矿性,其中Ag趋向于与黏土岩伴随的硅质砂岩类中,其他在碳酸盐岩中.在后期岩浆热源作用下,主要成矿元素能进一步富集成异常或成矿. 相似文献
414.
415.
This study focuses on the assessment of relationships between flow and macrozoobenthos structure that was performed in a reconnected oxbow lake located in the S?upia River floodplain (northern Poland). The lake was created during river straightening at the beginning of 20th century by cutting off the right‐bank meander. The oxbow restoration was performed to enhance the ecological viability of this water body and restore riverine wetland. In July 2000 the oxbow was connected with the river channel through PVC pipes which enabled free water movement. Macrozoobenthos sampling, as well as chemical analyses of water and hydrological measurements, took place both before and after the oxbow reconnection. Before the oxbow reconnection, the dominant species was Asellus aquaticus, whereas after the reconnection the structure of benthic species changed significantly. During the first year it was replaced by bivalves and Chironomidae larvae and then A. aquaticus. After the reconnection, macrozoobenthos mean density was 5‐fold higher and the mean wet biomass was 77‐fold higher than before the reconnection. The number of taxa increased from 4 before the oxbow reconnection to 17 during the first year after the performed works and 20 in the next year. We stated that the revitalization process of the reconnected oxbow lake has long‐term consequences for the benthic communities. The most significant feature of the oxbow reconnection is the qualitative and quantitative recolonization by riverine macrozoobenthos species. The performed restoration significantly improved ecological status of the oxbow lake by the increase in biodiversity and water quality. 相似文献
416.
湖相沉积盆地内隐伏断裂的电阻率层析成像探测——以通海盆地为例 总被引:1,自引:0,他引:1
本文利用电阻率层析成像方法对湖相沉积盆地——通海盆地内的小江断裂的西支断裂进行了探测。发现在电阻率图像的较深区域才能识别出断裂的位置和产状,它在通海盆地内的走向约为N47°E,倾角约为57°~66°,视倾向为NW或N,与以往的研究结果基本一致。 相似文献
417.
Climate variability during the Mid‐Late Holocene has influenced the activity of geomorphic processes in the current periglacial belt of the Sierra Nevada. We studied two types of sedimentary records that reveal a synchronous timing for slope instability in this high semi‐arid massif: solifluction landforms and mountain lake sediments. Lithological and sedimentological properties of both records have recorded numerous cycles of different magnitude of slope processes in the massif. Solifluction deposits record seven phases of solifluction activity and soil development during the last 7 ka bp and lake sediments show evidence of eight periods with increased geomorphic activity in the catchments over the last 6 ka bp . Although present‐day climate conditions do not promote active solifluction processes in the Sierra Nevada, colder and wetter periods during the Holocene triggered solifluction and transported coarse‐grained sediments into the lakes. By contrast, warm phases favoured soil formation and spread an incipient vegetation cover over the headwaters of the highest valleys, diminishing the grain size of the particles reaching the lakes. Lake sediments record an aridification trend in the massif intensifying since 4·2 ka bp that has conditioned solifluction activity to shift gradually to higher elevations. During major cooler phases such as the Little Ice Age active solifluction was recorded back down to 2500 m altitude. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
418.
根据1989、2000~2002、2007、2009年TM卫星遥感影像和1989~2009年气象数据分析:近20年来,西藏多庆错湖水面积呈显著的减小趋势,20年内减小了28.4km2;湖泊所在的帕里站年平均气温呈显著的升高趋势,年降水量呈减小趋势。分析湖泊面积变化的原因,降水量减少和气温升高使冰雪加速融化,导致湖泊补给水源不足是湖泊面积萎缩的主要原因。 相似文献
419.
Lower slopes of the Sandia Mountains are characterized by granitic corestone topography and weathering-limited slopes with thin grusy colluvium and weakly developed soils. In contrast, thick soils with illuvial clay and pedogenic carbonate have developed below aplite outcrops. Aplite is resistant to chemical decomposition, but physically weathers to blocky clasts that enhance surface roughness and erosional resistance of colluvium, promoting accumulation of eolian fines. Thick B horizons on aplite slopes indicate limited erosion and prolonged periods of stability and soil development. Accretion of eolian material limits runoff and prevents attainment of a steady-state balance between soil production and downslope transport. 相似文献
420.
高分辨湖泊沉积和孢粉记录对气候、水文变化的响应 总被引:4,自引:2,他引:2
通过对长江中游网湖钻孔高精度分层样品(1.5年/样品)的沉积学和孢粉学研究,试图揭示过去百年网湖在由开放到封闭体系变化中,沉积孢粉与气候、水文动力变化的过程及其相互关系.相关分析和低频滤波分析,反映出沉积物和孢粉的变化对流域降水和长江流量的敏感响应.在过去130年中的多雨洪水年份,湖泊受长江倒灌影响,沉积物以黏土细颗粒... 相似文献