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XIA Bin LU Ye YUAN Yajuan CHEN Weiyan ZHANG Xiao XU Chi YU Shengrui WAN Zhifeng 《《地质学报》英文版》2018,92(5):1753-1768
New zircon U–Pb ages, whole-rock geochemistry and zircon Hf isotopes from the Habo porphyry Western Yunnan, China, were determined to provide constraints on the timing of uplift of the Eastern Tibetan Plateau. The intrusive rocks consist of shoshonitic porphyry (syenite porphyry and monzonite porphyry). Zircon laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) U–Pb dating indicates coeval emplacement ages of ~35 Ma. The porphyries have alkaline affinities, enrichment in large ion lithophile elements (LILEs) and light rare earth elements (LREEs) (e.g., Rb, Th, U, Pb), with depletion of high field strength elements (HFSEs) (e.g., Nb, Ti, Ta) and weak Eu anomalies. They display uniform Lu–Hf isotopic compositions with negative zircon εHf(t) values ranging from -3.9 to -0.6. The chemical characteristics of the syenite porphyries indicated that they most likely originated from the lower crust, with mantle-derived material involved in their generation. Geochemically, the monzonite porphyries are similar to the syenite porphyries; however, the lower MgO contents suggest that they were produced by different degrees of partial melting of the same lower crust source. Combined with the geochemical and isotopic data in this paper, imply that the alkali-rich porphyries of the Habo polymetallic deposit were derived from the partial melting of lower crust, enriched by mantle magma, formed in a conversion stage from stress extrusion (a strike-slip shear process) to local stress relaxation (a strike-slip pull-apart process) at the Ailaoshao tectonic zone. 相似文献
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A review of advances in China’s flash flood early-warning system 总被引:1,自引:0,他引:1
Changjun Liu Liang Guo Lei Ye Shunfu Zhang Yanzeng Zhao Tianyu Song 《Natural Hazards》2018,92(2):619-634
This paper summarizes the main flash flood early-warning systems of America, Europe, Japan, and Taiwan China and discusses their advantages and disadvantages. The latest development in flash flood prevention is also presented. China’s flash flood prevention system involves three stages. Herein, the warning methods and achievements in the first two stages are introduced in detail. Based on the worldwide experience of flash flood early-warning systems, the general research idea of the third stage is proposed from the viewpoint of requirements for flash flood prevention and construction progress of the next stage in China. Real-time dynamic warning systems can be applied to the early-warning platform at four levels (central level, provincial level, municipal level, and county level) . Through this, soil moisture, peak flow, and water level can be calculated in real-time using distributed hydrological models, and then flash flood warning indexes can be computed based on defined thresholds of runoff and water level. A compound warning index (CWI) can be applied to regions where rainfall and water level are measured by simple equipment. In this manner, flash-flood-related factors such as rainfall intensity and antecedent and cumulative rainfall depths can be determined using the CWI method. The proposed methodology for the third stage could support flash flood prevention measures in the 13th 5-Year Plan for Economic and Social Development of the People’s Republic of China (2016–2020). The research achievements will serve as a guidance for flash flood monitoring and warning as well as flood warning in medium and small rivers. 相似文献
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文章从蚀源区铀源条件、中新生代构造演化条件、侏罗系沉积建造特征及后生蚀变特征等角度分析了准噶尔盆地东北部砂岩型铀矿的区域成矿条件,认为卡拉麦里山的富铀花岗岩体为该区砂岩型铀成矿提供了丰富的铀源,中侏罗统含煤碎屑岩建造为砂岩型铀成矿提供了良好的容矿空间,侏罗纪以来多期次不整合面的发育为含铀含氧水的渗入改造提供了通道及时间,为大规模层间氧化带的发育提供了物质基础。研究结果显示,卡拉麦里山北坡为最有利的砂岩型铀矿找矿部位,其主要找矿目标层位为中侏罗统头屯河组,找矿类型为层间氧化带型。 相似文献
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Timokhov L. A. Ivanov V. V. Kassens H. Lebedev N. V. Frolov I. Ye. Hölemann J. 《Doklady Earth Sciences》2018,480(1):685-688
Doklady Earth Sciences - According to historical oceanographic data, anomalies in the dynamic topography during the winter period were calculated and two climatic stages of dynamic condition of the... 相似文献
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Landslide-prone slopes in earthquake-affected areas commonly feature heterogeneity and high permeability due to the presence of cracks and fissures that were caused by ground shaking. Landslide reactivation in heterogeneous slope may be affected by preferential flow that was commonly occurred under heavy rainfall. Current hydro-mechanical models that are based on a single-permeability model consider soil as a homogeneous continuum, which, however, cannot explicitly represent the hydraulic properties of heterogeneous soil. The present study adopted a dual-permeability model, using two Darcy-Richards equations to simulate the infiltration processes in both matrix and preferential flow domains. The hydrological results were integrated with an infinite slope stability approach, attempting to investigate the hydro-mechanical behavior. A coarse-textured unstable slope in an earthquake-affected area was chosen for conducting artificial rainfall experiment, and in the experiment slope, failure was triggered several times under heavy rainfall. The simulated hydro-mechanical results of both single- and dual-permeability model were compared with the measurements, including soil moisture content, pore water pressure, and slope stability conditions. Under high-intensity rainfall, the measured soil moisture and pore water pressure at 1-m depth showed faster hydrological response than its simulations, which can be regarded as a typical evidence of preferential flow. We found the dual-permeability model substantially improved the quantification of hydro-mechanical processes. Such improvement could assist in obtaining more reliable landslide-triggering predication. In the light of the implementation of a dual-permeability model for slope stability analysis, a more flexible and robust early warning system for shallow landslides hazard in coarse-textured slopes could be provided. 相似文献
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提出基于背景噪声波速测量的综合预测指标法,将测震资料更好地应用于震情跟踪和地震短临预报。利用滇西北5个台站2012-01~2020-11宽频带连续波形资料,基于背景噪声互相关及傅立叶变换等方法,提取10个台站对当天经验格林函数与参考经验格林函数的直达瑞利波走时偏移时间序列,设定±1.5倍标准差作为异常阈值,并以其间发生的6次M≥5.0地震为样本,采用R值评分法对每个台站对的映震能力进行效能检验,最后基于自适应加权综合预测方法提取适合于滇西北地区的地震短临异常识别指标(综合指标)。结果表明,利用该综合指标对滇西北2012年以来发生的6次M≥5.0地震进行90 d短临预报,异常指标共出现8次,其中准确预报地震5次,漏报1次,虚报4次,预报效能评分R为0.692,R0为0.475。该综合指标的地震对应率为62.50%,概括率为83.33%。 相似文献