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991.
原状软粘土各向异性及其对工程影响研究 总被引:1,自引:0,他引:1
利用空心圆柱扭剪仪(HCA),通过设置不同的应力路径对杭州原状软粘土进行了系列试验,研究了原状软粘土的应力-应变-强度各向异性。通过试验研究发现原状软粘土的强度、变形模量等特性都存在强烈的各向异性,且在应力水平较低时(q=5 kPa),主应力轴旋转条件下土体应力应变的特性主要体现了原生各向异性的影响,应力引起的次生各向异性对其影响很小。结合路堤填筑问题的分析发现,存在主应力轴显著旋转的实际工程问题,由于原状软粘土应力-应变-强度各向异性的存在,采用常规的不考虑主应力轴旋转(土体各向异性)影响的设计方法可能偏于不安全。 相似文献
992.
993.
Horst G. Brandes 《Ocean Engineering》2011,38(7):835-848
Geotechnical properties from a series of deep-sea sites in the North Atlantic and North Pacific oceans are examined to evaluate overall trends and to compare with similar fine-grained soils found on land. The study areas encompass a range of sedimentary environments dominated by combinations of turbidite and pelagic deposits. Carbonate content in excess of 20% is seen to result in a decrease in liquid limit and compressibility. Vertical profiles of geotechnical properties in the North Pacific show broader changes in down-core geotechnical properties compared to the North Atlantic and reflect the effects of long-term climatic changes and seafloor spreading. Sediments in the North Atlantic indicate significant differences depending on location, which is attributed to variability in turbidite deposition, water depth, distance from sediment sources, and the effects of bottom currents. Compared to equivalent fine-grained soils on land, deep-sea sediments are generally softer, more compressible and have higher friction angles at comparable Atterberg limits. Deeper and older sediments in the North Pacific are characterized by unusually large plastic limits, which are attributed to the presence of volcanic fractions. Empirical relationships for compression index and friction angle are discussed for sediments from both oceans. 相似文献
994.
995.
系统测定了陕西洛川黑木沟黄土/古土壤的总有机碳及其主要组分(稳定有机碳、矿物保护有机碳和化学稳定有机碳)的含量,并对总有机碳与粘粒含量及粘土矿物含量的相关性进行了分析。结果表明:(1)各层古土壤的总有机碳含量均高于其下伏的黄土层(S4例外),而稳定有机碳、矿物保护有机碳以及化学稳定有机碳的平均含量在黄土与古土壤之间无明显差异;(2)黄土和古土壤中有机碳含量达到稳定所需要的时间不同,分别是140~250 ka和330~410ka;(3)总有机碳和化学稳定有机碳与粘粒呈正相关关系(相关系数r分别为0.46和0.54),它们与粉粒和细砂粒的相关性较差,这说明粘粒是土壤固定有机碳的重要组分;(4)高岭石与总有机碳和化学稳定有机碳的相关性比较明显(r分别为0.74和0.61),伊利石和蒙脱石与它们不相关或相关性较差。 相似文献
996.
997.
为了探索西南喀斯特地区土壤中黏土矿物组成及其含量的变异规律,以贵州省普定县和荔波县不同石漠化阶段典型土壤的黏土矿物为例,采用x-射线衍射仪图谱分析方法,计算得到黏土矿物组成及其含量,探讨不同石漠化阶段黏土矿物组成变化规律及其含量之间的线性关系。结果表明:不同石漠化阶段黏土矿物的组成是相同的,均为高岭石、蒙脱石和伊利石;在未石漠化、轻度石漠化、中度石漠化阶段,蒙脱石在剖面表层的质量分数分别为27.82%、29.34%、58.32%,高岭石分别为21.39%、31.81%、36.93%,伊利石分别为50.79%、38.85%、4.75%;在西南喀斯特地区,各石漠化阶段伊利石与蒙脱石的含量之间以及伊利石和高岭石的含量之间都呈显著的线性相关,相关系数分别为-0.9703、-0.9456;西南喀斯特地区土壤相似的成土作用和成土环境造成了黏土矿物相同的组成,而黏土矿物含量的差异说明各成土作用的程度或阶段是不同的;粉粒中的黏土矿物主要为石英和白云母,而砂砾中的黏土矿物主要为石英。 相似文献
998.
探讨了利用青铜器内残留的陶范或泥芯示踪青铜器产地的可行性。采用偏光显微镜、XRD、XRF、NAA等技术手段,测试分析了湖北九连墩楚墓青铜器内的泥芯,发现九连墩外来风格青铜器的泥芯,在物相、微观结构、化学成分、植硅体组合等方面与本地风格青铜器的泥芯有较大差异。外来风格青铜器的泥芯,其CaO含量很高,达6%以上,而Na2O的含量相对较低,这一富钙、贫钠的特点,与中国黄土的典型特征极为吻合。结合泥芯中的植硅体组合特征,推测九连墩外来风格的青铜器很可能来自中国北方黄土堆积地区,系当地铸造后输入到楚国的。本研究表明利用青铜器内的泥芯或陶范残留,可望有效地示踪青铜器的产地。 相似文献
999.
A simplified method for predicting ground settlement profiles induced by excavation in soft clay 总被引:2,自引:0,他引:2
A series of parametric studies was performed to examine the influence factors affecting the settlement influence zone induced by excavation in soft clay. It was found that the excavation depth, width, the soft clay bottom depth and the rock-like soil depth are all related to the settlement influence zone. The potential failure surface, as deduced from the failure mechanism, covering the above-mentioned parameters, is consistent with the settlement influence zone. Thus, a simple method based on the analysis results is proposed to predict the settlement influence zone. Ten case histories and statistical data for the settlements in the Shanghai area were used to verify the proposed method. 相似文献
1000.
Grain‐size data from different climatic zones across the Chinese Loess Plateau show that the loess generally contains an ultrafine component, which has a consistent modal grain size of ca 0·37 μm and a variable proportion of 4 to 10%. The variation of the ultrafine component through a loess section is characterized by a high proportion and fine grain size in palaeosols, and by a low proportion and coarse grain size in loess layers. Its proportional content in a stratum roughly increases from north‐west to south‐east across the Loess Plateau. Quantitative X‐ray diffraction analysis indicates that the ultrafine component is composed mainly of clay minerals (ca 70%), which are mostly illite (ca 80%), and with significant amounts of kaolinite (ca 8%) and chlorite (ca 2%). The temporal and spatial variations of the ultrafine component, and the degree of illite crystallinity, suggest that this component in aeolian sediments is linked closely to the process of pedogenesis. Weakly altered loess on the north‐western margin of the Loess Plateau contains considerable amounts of detrital clay minerals derived from the aeolian source areas. Results from a loess section with a basal age of 7·6 Ma in the central Loess Plateau show that the ultrafine component increased from 7·6 to 5 Ma, and progressively decreased thereafter. This trend was punctuated by two abrupt changes at 2·6 and 0·6 Ma. These variations reflect to a considerable extent the history of pedogenesis during the Late Cenozoic. 相似文献