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171.
    
To address the issue of extensive deformation in the Tabaiyi Tunnel caused by the fault zone, nuclear magnetic resonance (NMR) technology was employed to analyze the physical and mechanical properties of water-absorbing mudstone. This analysis aimed to understand the mechanism behind the significant deformations. Drawing from the principle of excavation stress compensation, a support scheme featuring NPR anchor-cables and an asymmetric truss support system was devised. To validate the scheme, numerical analysis using a combination of the Discrete Element Method (DEM) - Finite Element Method (FEM) was conducted. Additionally, similar material model tests and engineering measurements were carried out. Field experiments were also performed to evaluate the NPR anchor-cable and truss support system, focusing on anchor cable forces, pressures between the truss and surrounding rock, pressures between the initial support and secondary lining, as well as the magnitude of settlement and convergence deformation in the surrounding rock. The results indicate that the water-induced expansion of clay minerals, resulting from damage caused by fissure water, accelerated the softening of the mudstone's internal structure, leading to significant deformations in the Tabaiyi Tunnel under high tectonic stress. The original support design fell short as the length of the anchor rods was smaller than the expansion depth of the plastic zone. As a result, the initial support structure bore the entire load from the surrounding rock, and a non-coupled deformation contact was observed between the double-arch truss and the surrounding rock. The adoption of NPR asymmetric anchor-cable support effectively restrained the expansion and asymmetric distribution characteristics of the plastic zone. Considering the mechanical degradation caused by water absorption in mudstone, the rigid constraint provided by the truss proved crucial for controlling the stability of the surrounding rock. These research findings hold significant implications for managing large deformations in soft rock tunnels situated within fractured zones under high tectonic stress conditions.  相似文献   
172.
本文主要依据地形图和航空照片解译,并经已有地质、钻孔资料验证及野外实地考察的方法来研究地形面及其变形特征,由此确定渭河盆地活断层的分布、最新活动特征及活动规律,为地震预报及地震危险性分析提供依据。  相似文献   
173.
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The area of the present investigation's expanse constitutes the southernmost extent of the southeast Kumaun Himalaya and western Nepal Himalaya. Multidisciplinary approaches have been employed to understand the landforms associated with tectonic deformation, through detailed field investigation supplemented by the geodetic, chronological, and morphometric database. The morphogenic expressions of the Main Boundary Thrust (MBT) are reflected in the form of ~25 km long E-W trending north dipping fault scarp. The deformation along the strike length of the Himalayan Frontal Thrust (HFT) is noticed in the form of uplifted and incised fill terraces, and strath terraces. The deformation within the fluvial sequences in the study area can be visualized in the form of sheared boulders and pebbles, tilted and faulted terrace deposits. Furthermore, the chronological data of fluvial landforms in the study area suggests two major phases of tectonic deformations that have occurred around 58.7±10.8 ka and 3.88±0.4 ka. The chronology of late-Quaternary landforms advocates that the initial stage of aggradations in the Himalayan foothills commenced around 75.1±0.58 ka. The aggradational landforms resulted from the diverse depositional regime as evident from the nature of the sediment sequences from clasts dominated to thick mud sequences. The rate of deformation in the southeastern Kumaun and western Nepal Himalaya is ± 7 mm/yr, as per the data obtained from the Persistent Scatterer Interferometric Synthetic Aperture Radar (PSInSAR). The landform deformation pattern, phase of incision and aggradation, frequent occurrence of landslides, and recent past earthquake activity within the wide zone of the HFT, the MBT, and Ramgarh Thrust suggests that the southernmost front of the Kumaun Himalaya is active and has potential for future geohazard. The foothill zone of Himalayan towns are actively growing in terms of population and infrastructural development. Therefore, such intradisciplinary studies for tectonically active regions are needed for future infrastructural development.  相似文献   
174.
应用构造-层序地层分析的思维,通过构造格架与地层格架的关联分析,对南堡凹陷东营组沉积充填样式与过程、控制要素进行了综合研究。通过沉降史分析,并结合区域构造演化特征,古近纪可划分为4个次级构造幕。凹陷内断裂发育,同沉积断裂及其时空配置关系对凹陷内结构和沉积体系类型及其展布起着重要的控制作用。控凹断裂直接控制了局部构造带的可容纳空间变化和古地貌形态,从而形成不同的沉积展布特征。高柳断层是南堡凹陷内最为重要的二级断裂,其活动始于Es1沉积时期,在东营组沉积时期活动最为强烈。在东营组沉积时期,高柳断层将凹陷分为南、北两个独立的沉积系统,尤其在Ed3沉积期其强烈的翘倾作用使高柳地区成为一个孤立的湖盆,直接影响到了高柳地区的沉积充填。根据东营组沉积时期同沉积断裂组合样式划分出4种断裂坡折带:断崖型、断坡型、同向断阶型和反向断阶型,为研究南堡凹陷东营组同沉积断裂对沉积格局的控制作用提供了有利的指导,具有重要的石油地质意义。  相似文献   
175.
半球成像方法可广泛应用于植被结构参数及冠层光合有效辐射测量等领域。高逼真度虚拟森林环境的半球成像方法模拟及验证可用于定量评估半球成像方法测量精度及地面验证研究。但高逼真度虚拟森林环境下半球成像方法模拟面临场景复杂度高、面片数巨大、模拟效率低等难题。首先,论文以高逼真度虚拟森林环境构建原理建立了不同林分密度、树木分布模式、场景大小及树木种类等特征的虚拟森林环境库;然后,在采用光线跟踪算法开展半球成像方法模拟时,对比分析了4种数据结构分割平面搜索方法,即空间中分法、对象中分法、启发式排序法和启发式BIN分区法,结果表明,启发式排序法性能最佳;最后,以高逼真度虚拟森林环境库,对比分析了传统方法、Kdtree、BVH、Octree 4种数据结构方案组织、管理单树几何模型及虚拟森林场景两级数据集效率,并选择场景节点遍历数、单树几何模型节点遍历数、单树几何模型遍历数、面片遍历数及平均计算时间等参数作为衡量数据结构组织方案性能的定量化指标,研究发现Kdtree数据结构方案较其他3种数据结构方案更为优越,因此,其可作为高逼真度虚拟森林环境库的半球成像方法模拟之首选。  相似文献   
176.
廊固凹陷近岸水下扇特征及控制因素   总被引:2,自引:0,他引:2  
通过对廊固凹陷18口井541 m岩心的系统观察、156口井测井序列的建立、1km×1 km三维地震测网密度的地震相识别,分析了该沉积体系的相带展布特征。该砂砾岩层总体趋势为向上厚度减薄、层数减少,共识别出5期扇体,多呈条带状沿大兴断层断面分布,每期之间发育稳定的暗色泥岩段。该近岸水下扇的形成受3级层序、大兴断层、古构造、古气候、古地形以及物源供给等多种因素的控制。3级层序的发育特点、大兴断层的分段活动以及特殊的物源供给背景因素的匹配对近岸水下扇形成起到决定性作用。2~3期扇体扇中分布范围广,储集条件好,是凹陷下一步开发工作的有利目标。  相似文献   
177.
在国内外现行的主要孕震模式的基础上,得出了一个较为合理的详细阐述孕震过程的模式。该模式由(Ⅰ)弹性变形、(Ⅱ)扩容、(Ⅲ)前兆蠕动、(Ⅳ)地震、(Ⅴ)震后调整等阶段组成,主要强调液体(水)存在;发生大小地震的断层均由积累单元和调整单元组成,余震是大震后构造剪切应力重新调整以及主断层未破裂区和位于它两侧尺度小、长度短的断层未破裂区共同破裂的结果。最后,运用断裂力学理论对该模式的孕震过程进行了比较圆满的解释。  相似文献   
178.
    
It is inevitable to encounter fault zones in tunnel construction. These faults can lead to significant deformations and potential collapses of the surrounding rock in the tunnel. Therefore, it is crucial to study the influence of different fault angles on tunnel deformation. The Tabaiyi Tunnel, located in Yunnan Province of China passes through a multi-stage fault zone. The dynamic response characteristics of the surrounding rock in the Tabaiyi Tunnel were studied under various fault dip angles and the most unfavorable angle was identified. Physical model tests were conducted using two types of anchor cables with specific parameters. Additionally, a relationship between the engineering rock mass and energy absorption by the anchor cables was established, demonstrating the advantages of negative Poisson's ratio (NPR) anchor cables. Experimental results indicate that stress concentration tends to occur at the junctions between faults and the surrounding rock mass. Tunnels supported by NPR anchor cables effectively mitigate amplification effects, achieving energy absorption increases of up to 87% compared to positive Poisson's ratio (PR) anchor cables. Furthermore, the highest acceleration amplification was observed at a fault dip angle of 45°, with peak acceleration reaching twice that of the original input wave, indicating that this angle should be avoided in tunnel design. These findings provide valuable insights for the safe management of tunnels traversing fault zones.  相似文献   
179.
本文通过对实测海平面高度的对比,发现龙口平均海平面从1991年起有明显的升高趋势。作者猜测此乃龙口在码头扩建后有系统下沉所致。  相似文献   
180.
Chalk is exposed in the Heidestrasse quarry at Lägerdorf, at the top of the NE-SW trending Krempe salt ridge. Structural data indicate the presence of two joint sets, striking almost parallel and perpendicular to the salt ridge, respectively, and of a set of conjugate extensional faults and fault zones striking NW-SE, i.e. almost perpendicular to the salt ridge. Within the overall NW-SE trend of joints and faults, strike variations occur from the massive chalk exposed in the lower half of the quarry, to the overlying layered chalk. A large variability characterizes the normalized spacing of both joint sets, which does not show any clear trend with layer dip. In situ measurements indicate that the cross-sectional permeability of tight joints increases 1-2 orders of magnitude with respect to the undeformed chalk. We propose that joint and fault azimuthal variability resulted from changes through time of the stress ellipsoid at the top of the salt ridge, while joint spacing variability is associated with the weak mechanical influence of bedding in chalk. Azimuthal variability improves fracture connectivity and, hence, permeability and fluid flow.  相似文献   
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