全文获取类型
收费全文 | 960篇 |
免费 | 114篇 |
国内免费 | 104篇 |
专业分类
测绘学 | 16篇 |
大气科学 | 36篇 |
地球物理 | 113篇 |
地质学 | 293篇 |
海洋学 | 671篇 |
天文学 | 1篇 |
综合类 | 16篇 |
自然地理 | 32篇 |
出版年
2024年 | 10篇 |
2023年 | 32篇 |
2022年 | 36篇 |
2021年 | 35篇 |
2020年 | 48篇 |
2019年 | 50篇 |
2018年 | 33篇 |
2017年 | 36篇 |
2016年 | 41篇 |
2015年 | 35篇 |
2014年 | 58篇 |
2013年 | 61篇 |
2012年 | 48篇 |
2011年 | 43篇 |
2010年 | 31篇 |
2009年 | 46篇 |
2008年 | 57篇 |
2007年 | 43篇 |
2006年 | 49篇 |
2005年 | 48篇 |
2004年 | 52篇 |
2003年 | 42篇 |
2002年 | 46篇 |
2001年 | 26篇 |
2000年 | 21篇 |
1999年 | 29篇 |
1998年 | 24篇 |
1997年 | 10篇 |
1996年 | 14篇 |
1995年 | 8篇 |
1994年 | 14篇 |
1993年 | 14篇 |
1992年 | 13篇 |
1991年 | 6篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1988年 | 6篇 |
1985年 | 5篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1954年 | 1篇 |
排序方式: 共有1178条查询结果,搜索用时 15 毫秒
991.
为改善海上风电大直径钢管桩的水平承载性能,基于ABAQUS有限元软件对单桩改进形式的加翼桩结构进行了系统研究,计算分析了软黏土地基中加翼桩在水平荷载作用下桩身弯矩、应力、位移、桩身泥面处倾斜率和极限承载力,研究了加翼桩面积、形状、埋深和刚度等翼板参数对加翼桩水平承载性能的影响规律,根据加翼桩的桩-土作用机理,参考现行规范模式提出适用于软黏土地基大直径钢管桩的P-Y曲线。研究结果表明,加翼桩通过在泥面处设置翼板可降低桩基泥面处倾斜率50%、提高桩基极限承载力60%以上,加翼桩水平承载性能明显优于单桩。 相似文献
992.
Vikram Singh 《Marine Georesources & Geotechnology》2018,36(5):505-514
Although the uplift behavior of offshore plate anchors under undrained conditions has been investigated well in the past, studies on the behavior of anchors under long-term sustained loading are in relatively few numbers. The time required for consolidation under sustained load is important because the shear strength of soil changes after dissipation of excess pore pressure. In this paper, small strain finite-element analyses have been performed to investigate the consolidation time history above and beneath strip anchors. The modified cam clay plasticity constitutive model is used for modeling coupled pore fluid stress analysis. The effects of magnitude of preloading with embedment level have been studied. As expected, the FE results have shown that excess pore pressure dissipation time for soil above the anchor increased with the increase in embedment depth and the magnitude of preload. Rapid dissipation of negative excess pore pressure beneath the anchor was observed with increasing embedment depth, if the preload magnitude is equal to or more than 60% of the undrained capacity. Observed consolidation responses are presented as nondimensional design charts and simplified equations for ease of practice. 相似文献
993.
Bearing capacity of shallow foundations in clay with linear increase in strength and adhesion factor
Boonchai Ukritchon Sothoan Yoang Suraparb Keawsawasvong 《Marine Georesources & Geotechnology》2018,36(4):438-451
In this paper, the computational lower bound (LB) limit analysis using finite element with second-order cone programming was used to investigate the LB solutions of the undrained bearing capacity of continuous footing with a linear increase in the strength profile and an adhesion factor at the soil–footing interface. A full range of parametric studies of the dimensionless strength gradients and adhesion factors at the soil–footing interface were performed in the LB calculations. The results were verified by comparison with the available solution from the method of characteristics (slip-line analysis) for perfectly smooth and rough footings. The LB analyses were able to complete a prior solution of undrained bearing capacity with a linear increase in the strength profile by incorporating the influence of adhesion factor at the soil–footing interface. Based on the nonlinear regression to the computed LB solutions, an approximate expression of the LB solution regression was proposed, which is applicable to an accurate prediction of a safe load for offshore shallow foundations in clay with an arbitrary linear increase in strength and adhesion factor at soil–foundation interface in practice. 相似文献
994.
利用Topex/Poseidon(T/P)、Jason-1和Jason-2卫星24a的原始轨道及6a的变轨轨道高度计资料,对浙江近海区域内进行潮汐调和分析,得到8个主要分潮(Q_1、O_1、P_1、K_1、N_2、M_2、S_2和K_2)的调和常数.比较卫星轨道交叉点处潮汐调和常数结果显示,8个分潮总体综合误差在原始轨道,变轨轨道及原始轨道与变轨轨道交叉点处的和方根RSS值分别为3.16、7.02、5.54cm;用卫星高度计资料及31个近岸验潮站得到的潮汐分布与21个验潮站资料结果进行比较,M_2、S_2、N_2、K_1和O_1主要分潮的多点向量均方根偏差分别为4.32、3.64、1.97、2.61、1.83 cm;本研究结果与前人数值模拟结果比较显示M2、S2分潮在对比点处的多点向量均方根偏差在11、8 cm左右,最后给出了浙江近岸及近海区域更为精确的5个主要分潮(M_2、S_2、N_2、K_1和O_1)的同潮图. 相似文献
995.
Tidally driven pore water exchange within offshore intertidal sandbanks: Part II numerical simulations 总被引:1,自引:0,他引:1
B. Gibbes C. Robinson L. Li D. Lockington H. Li 《Estuarine, Coastal and Shelf Science》2008,80(4):472-482
Field measurements presented by [Gibbes, B., Robinson, C., Li, L., Lockington, D.A., Carey, H., 2008. Tidally driven pore water exchange within offshore intertidal sandbanks: Part I Field measurements. Estuarine, Coastal and Shelf Science 79, pp. 121–132.] revealed a tidally driven pore water flow system within an offshore intertidal sandbank in Moreton Bay, Australia. The field data suggested that this flow system might be capable of delivering nutrients, and in particular bio-available iron, across the sediment–water interface. Bio-available iron has been implicated as a key nutrient in the growth of the toxic marine cyanobacteria Lyngbya majuscula and therefore this pore water exchange process is of interest at sites where L. majuscula blooms have been observed. In this study two-dimensional numerical simulations were used in conjunction with hydraulic data from field measurements to further investigate the tidally induced pore water flow patterns. Simulation results generally showed good agreement with the field data and revealed a more complex residual pore water flow system in the sandbank than shown by the field data. The flow system, strongly influenced by the geometry of the sandbank, was characterized by two circulation cells which resulted in pore water discharge at the bank edge and also to a permanently ponded area within the sandbank interior. Simulated discharge volumes in these two zones were in the order of 0.813 m3 and 0.143 m3 per meter width (along shore) of sandbank per tidal cycle at the bank edge and sandbank interior respectively. Transit times of pore water circulating through these cells were found to range from ≈ 17 days to > 60 years with an average time of 780 days. The results suggest that the tidally driven flow systems might provide a mechanism for transport of bio-available iron across the sediment–water interface. This flow could constitute a previously unrecognized source of bio-available iron for L. majuscula blooms in the Bay. 相似文献
996.
Mobile offshore double-causeway pier system, a type of seashore unloading equipment, consists of two groups of multiple connected semi-submersible modules. This structure has wide application because most of the middle or mini type of vessels and ships can be moored to it. Based on the analysis of computational methods of multi-body motion response, a hydrodynamic model is set up and the three-dimensional potential theory in finite depth is adopted to calculate the three-dimensional motion response of this system. The double P-M spectrum is used to analyze the motion response in irregular waves. Different wave directions are specially taken into consideration, due to their various effects to the motion response. Furthermore, the calculated result is compared with that of the experiment, and it is proved that sway, heave, pitch and yaw motion are greatly constrained by mooring system. The comparison also indicates that the model can forecast the motion performance of the target, and that the calculated result can also be used as reference in connector and mooring system design. 相似文献
997.
998.
999.
This paper presents new seismic hazard maps of the Maghreb countries by using newly re-evaluated earthquake data catalogue in the region under consideration. For this region, there is a clear need to use common procedure and data bases through the whole Maghreb region so that seismic hazard assessments are consistent from country to country. An effort is made to assess the seismic hazard and to construct earthquake hazard maps in terms of expected horizontal and vertical PGA for a 10 per cent chance of being exceeded, expected intensity (MSK), all in an economic life time of 50 and 100 years. Also, a return period seismic hazard map for PGA≥140cm/s2 is presented. For engineering applications, earthquake hazard maps for structures with different periods are also constructed. 相似文献
1000.
1604年泉州海外大地震及其海啸影响分析 总被引:1,自引:0,他引:1
由于史料记载的模糊和局限性, 1604年泉州海外8级大地震是否引发地震海啸灾难, 一直是有争议的。 该文从这次地震历史资料的辨别、 考证和分析研究认为, 泉州海外大地震并未引发地震海啸产生的显著灾害。 在相关的史料与台湾海峡发震构造的分析基础上, 通过潜在海啸源的鉴别以及海啸源参数的确定, 对泉州滨海断裂和台湾海峡浅滩南缘海啸源进行数值模拟计算。 在计算过程中, 利用了1994年台湾海峡浅滩南缘地震的海啸波验潮站资料, 对计算模型和方法进行了检验。 1604年泉州海外大地震的潜在海啸源(滨海断裂)的数值计算结果表明, 海啸波对泉州湾沿岸的增减水效应不足以造成灾难性的影响, 因此也为1604年泉州海外大地震未引发灾难性的海啸提供了新的证据。 相似文献