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1.
上海某国际金融大厦深大基坑项目北侧紧邻运营轨道交通8号线区间隧道,最近处仅7.87 m,南侧与现有世博共同管沟净距2.0~3.0 m,基坑变形控制要求高,周边环境敏感。同时,本项目位于黄浦江畔,场地浅层为典型的淤泥质软土地层,下部为富含承压水粉(砂)土层,且微承压水层与第一、第二承压水层互为连通,止水帷幕无法隔断承压水层,地质条件复杂。设计采用分坑施工、被动区加固、预应力伺服钢支撑系统、抽灌一体化降水方案、超深地下连续墙、跟踪注浆、型钢垫层等技术方案。实测结果表明,区间隧道的最大变形6.52 mm,共同管沟的最大变形15.3 mm,其最大变形均满足变形控制要求,确保了运营区间隧道和共同管沟的安全。 相似文献
2.
Characterization of Continental Intercalaire aquifer (CI) in the Tinrhert-East Area-Illizi Basin on the Algerian-Libyan Border 下载免费PDF全文
This paper addresses the characterization of the Continental Intercalaire aquifer(CI) in the Tinrhert-East area of Illizi Basin on the Algerian-Libyan border, which belongs to the SASS1 system, one of the biggest transboundary aquifers in the world. This study concerns a superficies of 4 300 km~2. On the basis of Mud Logging borehole data conducted in this part of the aquifer, a realistic characterization of the aquifer was done. The thickness of the CI aquifer varies from 300 m in the south to 700 m in the north, and the depth ranges from 180 m to 320 m. The interpretation of the logs showed that the aquifer is characterized by a maximum net thickness in its southwestern part(more than 600 m), the porosity is very high, ranging from 30% in the west to 24% at the Libyan borders, the permeability is low to medium around 10~(-5) m/s, and the maximum transmissivity values of about 8× 10~(-3) m~2/s were recorded at the center of the study area. The depth of water varies from 235 m to 312 m, and the water flows from south to north, in accordance with the general direction observed in the CI aquifer in the Northern Sahara Aquifer System(SASS). The porosity values obtained from the interpretation of the sonic and density logs permit to estimate the water reserves of this aquifer considered fossil, at thresholds much higher than what was considered until now. 相似文献
3.
广东省珠海市洪鹤大桥主墩承台位于珠江西江流域的流塑状淤泥地层,采用钢板桩围堰进行基坑支护,基坑开挖过程中,钢板桩围堰发生较大的变形。经详细分析,发现导致事故的主要原因有地下水位持续升高导致土体力学性能显著下降、边跨侧钢板桩长度不足、基坑边缘集中荷载过大、施工控制不严、内支撑体系施工精度不足等。为了确保深基坑支护的安全,在全面分析总结了钢板桩围堰变形原因的基础上,结合实际情况,采取了增设穿透淤泥质土层的钢管桩围堰、加强内支撑体系等加固处理措施,并在实施过程中进行持续监测,最终安全地完成了基坑工程的施工。 相似文献
4.
基坑降水的成功与否,将对基坑开挖和周边环境产生重要影响,因此有必要对基坑降水方案进行评估。针对扬中金源时代购物中心基坑降水问题,采用MIDAS/GTS对基坑降水效果进行研究。首先,依据地勘报告中提供的土体渗透系数,结合单井、双井抽水试验结果,反演出MIDAS/GTS中需要的土层渗流系数和边界函数;然后利用反演得到的参数,建立了考虑回灌井补水效应的三维基坑降水效果分析模型,模拟基坑内水位降深与时间的变化关系,并对基坑降水效果进行分析和评估,以期指导土方开挖工程的施工。 相似文献
5.
伴随着城市的快速发展,地铁深基坑工程越来越多。在开挖过程中如何对其稳定性进行评价,是当前需要重点关注的问题。以成都地铁十七号线凤溪站深基坑支护开挖工程为依托,利用层次分析确定的主观权重与利用熵值法确定的客观权重计算获得组合权重,并与灰色关联度分析法相结合,通过现场数据采集并进行综合评判,客观评价地铁深基坑开挖的稳定性。结果表明,各监测项目对基坑稳定性的重要程度从大到小依次为桩顶水平位移(0.29)、地表沉降(0.24)、建筑物沉降(0.19)、桩顶沉降(0.18)、内支撑轴力(0.10),基坑稳定性综合评判结果等级为"非常好"。所建立的评价模型可为类似地铁深基坑开挖稳定性评价提供新的方法。 相似文献
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The ground motion owing to the collapse of a large-scale cooling tower under strong earthquakes was appropriately predicted using a comprehensive approach. The predicted results can be used for the safety evaluation of nuclear-related facilities adjacent to the cooling tower as well as in the planning of nuclear power plant construction in China. In this study, a cooling tower–soil model was first developed based on a falling weight–soil model, which the authors verified by falling weight tests. Then the collapse process of a cooling tower was simulated, and the collapse-induced ground vibrations were assessed by using the proposed model. Finally, the ground motion, which was a combination of the earthquake-induced ground motion and the collapse-induced ground vibrations, was estimated based on the superposition principle of waves. It was found that the cooling tower may collapse under strong earthquakes with the peak ground accelerations (PGAs) in the range of 0.35–0.45 g in x (EW) and y (NS) directions, respectively. These PGAs are far beyond the PGA range of major earthquakes in the common seismic design in China. The types of the site geologies of towers can significantly affect the collapse-induced ground vibrations. For a typical hard soil consisting of strongly weathered sandy slate, moderate ground vibrations may occur in the considered region. The collapse-induced PGAs were in the range of 0.017–0.046 g for the observed points at distances of 350 m in radial direction. For a rock-like foundation, the collapse-induced radial PGAs may be as high as 0.08 g at distances of 350 m, indicating that the effect of the collapse-induced ground vibrations on the nuclear-related facilities should be seriously assessed in certain scenarios. 相似文献
8.
锚索的预应力损失在工程建设中不可忽视,工程的场地环境条件成为影响锚索预应力损失的主因。饱和粉细砂层较其他地质条件更为复杂敏感,更易引起锚索预应力值的损失。通过对廊坊市某深基坑工程锚索预应力值的实时监测,结合工程环境,分析饱和粉细砂层中造成锚索预应力值变化的原因。结果表明,施工过程、张拉过程以及环境因素都影响锚索预应力的变化,其中开挖过程的影响最明显,预应力值的变化率最大值达79.1%;瞬时卸载造成预应力值22.8%59.2%的损失。对饱和粉细砂层中锚索预应力变化规律的研究分析结论可为类似地质环境的工程建设提供经验。 相似文献
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