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851.
110kV单腿铁塔基础纠偏技术 总被引:1,自引:1,他引:0
建于深厚软土上的某铁塔因基础周边不均匀填土后产生了严重的不均匀沉降,经采用顶压法和掏土法对构筑物进行综合促沉纠偏,同时采用钢管桩法加固处理,实践表明效果良好. 相似文献
852.
结合实际介绍了公路路基加宽时处理措施、加宽方法和施工时注意的问题,并提出几点看法和建议,希望能为其他项目施工提供借鉴。 相似文献
853.
854.
Sediment instabilities are common on the prodeltas of the seismically active continental margins of Western Greece. Sediment
failures on the low-angle (0.5°–2°) prodelta slopes manifest themselves as successions of peripheral rotational block slumps
restricted to the foresets of the late highstand systems tract (HST). The individual slump blocks are about 80–150 m long
and are bounded by growth faults acting as curved slip planes that extend to a mean depth of 10–15 m below seafloor. Shear
planes develop in the lower part of muddy and/or gas charged HST foresets. Deeper basal transparent muddy layers of the early
HST bottomset, together with the late Pleistocene transgressive systems tract sequences (TST), are mostly unaffected. On the
steeper (2°–6°) fan delta slopes of the western Gulf of Corinth debris flows and avalanches with a significant retrogressive component dominate
slope destabilisation. Sediment cores taken from landslide scarps and slide planes penetrated gas bubble releasing sediments
thereby indicating that failure planes are in the late HST foresets/upper part of the early HST bottomsets gas charged zone.
The foresets of the HST prodelta deposits display high water content (30–80%), low bulk density (1.4–1.9 g cm−3) and relatively low values of undrained shear strength (3–20 kPa). The water content of the HST distal muddy bottomsets is
relatively higher (50–110%) and bulk density relatively lower (1.3–1.7 g cm−3) with low values of shear strength (2–10 kPa). The shear strength of the gas releasing sediment layer displays lower values
(2–9 kPa) relative to the overlying, post failure, muddy sediments of the late 100–300 years. Slope stability was calculated
using the normalised soil parameter (NSP) method under undrained conditions for normally consolidated prodelta sediments.
This analysis indicates that instabilities could be induced by critical earthquake ground accelerations of 26.6–29.6% g for
the HST foresets and 12.4–14.1% g for the basal transparent layer belonging to the early HST bottomsets. Consequently the
early HST bottomsets has to be considered a potentially unstable layer since the regional peak ground accelerations (PGAs)
for the next 50 years are expected to range from 19 to 30% g. Moreover, our results show that new glide planes in the prodeltaic
sediment bodies of the seismically active continental margins of Western Greece will likely develop from the gas charged sediments
of the lower part of the HST foresets to the upper part of early HST bottomsets. 相似文献
855.
105°E和125°E越赤道气流与南、北半球环流变化的关系 总被引:4,自引:2,他引:2
采用1980~2004年5~8月NCEP/NCAR逐日再分析资料, 将105°E和125°E越赤道气流增强过程按一定标准进行取样, 并对增强过程中越赤道气流的变化特点及其相应的南、 北半球环流特征进行分析, 结果表明: 越赤道气流的增强往往对应着通道南侧或北侧从热带到副热带地区的环流调整, 而这种环流调整在南半球主要指澳洲冷空气活动, 在北半球主要为辐合带的变化, 二者是影响越赤道气流的主要环流因子; 北半球辐合带的变化与西太平洋副高的东西振荡有密切关系, 前者的分布形态在一定程度上决定了南半球环流及越赤道气流变化对北半球热带外环流的影响情况; 125°E越赤道气流比105°E越赤道气流的增强过程通常更为显著, 这与它们对应的南、 北半球环流调整的差异有关。 相似文献
856.
Determination of the critical failure surface for slope stability analysis using ant colony optimization 总被引:3,自引:0,他引:3
Slope stability analysis of any natural or artificial slope aims at determining the factor of safety of the slip surface that possesses the lowest factor of safety. In this study, an ant colony optimization (ACO) algorithm is developed to solve this factor-of-safety minimization problem. Factors of safety of slip surfaces are found by using the Morgenstern–Price method, which satisfies both force and moment equilibrium. Nonlinear equations from the Morgenstern–Price method are solved numerically by the Newton–Raphson method. In the proposed ACO algorithm, the initiation point and the shape of the slip surface are treated as the search variables. The proposed heuristic algorithm represents slip surfaces as piecewise-linear curves and solves for the optimal curve yielding the minimum factor of safety. To demonstrate its applicability and to investigate the validity and effectiveness of the algorithm, four examples with varying complexity are presented. The obtained results are compared with the available literature and are found to be in agreement. 相似文献
857.
This research selected water soil erosion indicators (land cover, vegetation cover, slope) to assess the risk of soil erosion,
ARCMAP GIS ver.9.0 environments and ERDAS ver.9.0 were used to manage and process satellite images and thematic tabular data.
Landsat TM images in 2003 were used to produce land/cover maps of the study area based on visual interpreting method and derived
vegetation cover maps, and the relief map at the scale of 1:50,000 to calculate the slope gradient maps. The area of water
soil erosion was classified into six grades by an integration of slope gradients, land cover types, and vegetation cover fraction.
All the data were integrated into a cross-tabular format to carry out the grid-based analysis of soil erosion risk. Results
showed that the upper basin of Miyun Reservoir, in general, is exposed to a moderate risk of soil erosion, there is 715,848 ha
of land suffered from water soil erosion in 2003, occupied 46.62% of total area, and most of the soil erosion area is on the
slight and moderate risk, occupied 45.60 and 47.58% of soil erosion area, respectively. 相似文献
858.
An assessment of the susceptibility to rock slope failure by means of a back-propagation network is proposed for the eastern
portion of the Southern Cross-Island Highway in Taiwan. The model was developed on the basis of six influence parameters of
rock slope instability, which include the rock type, slope aspect, slope angle, joint set number, joint spacing and bedding–slope
relationship. The values of these influence parameters were used as inputs for the network and were classified as nominal
scales in terms of binary numbers, while the state of failure/non-failure of a given slope was assumed to be the output variable.
Data on a total of 170 slopes along the highway was fed into the network for learning. According to the outputs of the network,
the susceptibility to rock slope failure is categorized into four levels, namely low, medium–low, medium and high, which are
mapped along the highway. Three highly susceptible regions are found, which can be viewed as hazardous sections requiring
cautionary measures. Moreover, the proposed model can be used as a tool for determining the possible state of an unfamiliar
rock slope in the context of devising management strategies to be applied to the investigated portion of the highway. 相似文献
859.
松辽盆地西部斜坡北段油气主要来自齐家-古龙生油凹陷青山口组烃源岩,油气沿着高台子油层和萨尔图二-三油层砂体以狭窄的路径侧向西运.共发育3条运移路径,侧向运移的油气受低幅度构造、断层和地层尖灭遮挡富集成藏.西部斜坡构造幅度较低,断层规模小,平面延伸的距离短,不利于油气大规模聚集成藏,盆地边部的地层超覆带是寻找大规模地层尖灭油气藏和油砂矿的有利地区.斜坡区普遍受大气降水淋滤作用,原油受喜氧细菌的降解作用普遍稠化,沿着大气水下渗方向,原油稠化的程度越米越低,造成自西而东原油性质呈现规律性变化:地层超覆带为严重降解的稠油和油砂,断层遮挡油气聚集带为中等降解的稠油,构造-岩性油气聚集带为轻度降解的稠油和正常原油. 相似文献
860.
利用中国首次北极科学考察白令海调查资料计算了白令海东部陆坡区 58- 60°N范围内海流的流幅、流速和流量 ,并获得如下结论 :(1 )白令海东陆坡区陆坡流由东南向西北变化 ,流速由东南向西北逐渐增加 ,在 58°N处 ,最大流速达到 1 0cm/s,到 60°N处 ,最大流速达到 30cm/s,是历年调查中最高的 ;流幅由东南向西北不断增宽 ,在 58°N处 ,最大流幅约 1 0 0km ,到 60°N处 ,最大流幅达到 2 1 0km ,流量由东南向西北也不断增加 ,在 58°N处 ,最大流量 5 .3Sv ,到 60°N处 ,最大流量达到 1 0 .2Sv ;(2 )陆坡流的近陆架一侧陆坡逆流的北界位置在 58°N处 ,其表层流幅宽度为 70km ,流速达到 5cm/s以上 ,在 59°N处其影响深度可以直达海底 ,,陆坡逆流的流速降低 ,流幅增宽到 1 1 0km ,60°N附近为陆坡逆流的北界 ,未观测到陆坡逆流 ;(3)陆架坡折锋强化了陆坡流。 相似文献