全文获取类型
收费全文 | 253篇 |
免费 | 40篇 |
国内免费 | 52篇 |
专业分类
测绘学 | 14篇 |
大气科学 | 2篇 |
地球物理 | 53篇 |
地质学 | 93篇 |
海洋学 | 171篇 |
综合类 | 11篇 |
自然地理 | 1篇 |
出版年
2024年 | 1篇 |
2023年 | 1篇 |
2022年 | 6篇 |
2021年 | 7篇 |
2020年 | 7篇 |
2019年 | 14篇 |
2018年 | 15篇 |
2017年 | 24篇 |
2016年 | 15篇 |
2015年 | 15篇 |
2014年 | 17篇 |
2013年 | 15篇 |
2012年 | 9篇 |
2011年 | 18篇 |
2010年 | 14篇 |
2009年 | 6篇 |
2008年 | 11篇 |
2007年 | 13篇 |
2006年 | 9篇 |
2005年 | 13篇 |
2004年 | 16篇 |
2003年 | 7篇 |
2002年 | 12篇 |
2001年 | 11篇 |
2000年 | 9篇 |
1999年 | 5篇 |
1998年 | 10篇 |
1997年 | 3篇 |
1996年 | 4篇 |
1995年 | 7篇 |
1994年 | 7篇 |
1993年 | 3篇 |
1992年 | 7篇 |
1991年 | 2篇 |
1990年 | 2篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1980年 | 2篇 |
排序方式: 共有345条查询结果,搜索用时 15 毫秒
21.
22.
23.
球状地球体可控深度电法的效应系数可近似地全面表达可控深度电法和各种效应。通过点源二度体的电算模拟实验,证明了该方法在水平柱状体和地下存在电阻率垂直界面的条件下,也是有效的。 相似文献
24.
范孟彬 《水文地质工程地质》1997,24(4):54-54,57
本文重点介绍在漂石,砂卵石地层中进行大口径φ1.8m桩基施工时,采用钻,抓成孔工艺的实例。 相似文献
25.
26.
研究了移动测量系统宽幅影像的拼接与量测算法。通过建立三幅影像柱面全景投影的几何关系,能够直接拼接完成宽幅影像。利用宽幅影像和原始影像间反投影变换关系以及三幅原始影像的同、异步立体像对,可建立宽幅影像与物方空间坐标间一一对应关系,从而实现宽幅影像目标的量测算法。宽幅影像的投影拼接和量测实验表明,利用柱面全景投影拼接得到宽幅影像的方法可应用于移动测量平台宽幅影像序列的拼接;在原始影像具备同步立体像对的条件下,宽幅影像量测的绝对精度可达1 m以内,相对精度可达0.2 m以内,满足城市环境实景目标量测的精度需求。 相似文献
27.
The first order reliability method (FORM) is efficient, but it has limited accuracy; the second order reliability method (SORM) provides greater accuracy, but with additional computational effort. In this study, a new method which integrates two quasi-Newton approximation algorithms is proposed to efficiently estimate the second order reliability of geotechnical problems with reasonable accuracy. In particular, the Hasofer–Lind–Rackwitz–Fiessler–Broyden–Fletcher–Goldfarb–Shanno (HLRF–BFGS) algorithm is applied to identify the design point on the limit state function (LSF), and consequently to compute the first order reliability index; whereas the Symmetric Rank-one (SR1) algorithm is nested within the HLRF–BFGS algorithm to compute good approximations, yet with a reduced computational effort, of the Hessian matrix required to compute second order reliabilities. Three typical geotechnical problems are employed to demonstrate the ability of the suggested procedure, and advantages of the proposed approach with respect to conventional alternatives are discussed. Results show that the proposed method is able to achieve the accuracy of conventional SORM, but with a reduced computational cost that is equal to the computational cost of HLRF–BFGS-based FORM. 相似文献
28.
Laboratory Study for Influence of Clay Content (CC) on Wave-Induced Liquefaction in Marine Sediments
B. Liu 《Marine Georesources & Geotechnology》2016,34(3):280-292
In this artice, the influence of clay content on the wave-induced liquefaction in marine sediments was reported. The one-dimensional (1-D) equipment was setup with a vertical cylinder and 1.8–m–thick clayey sandy deposit and 0.2–m–thick water above the deposit. Unlike the previous experimental study for a single soil layer, this study used sand-kaolin mixtures, sand-illite mixtures, and sand-bentonite mixtures as the experimental samples. A series of experiments with 3,000 wave cycles in each test were conducted under numerous wave and soil conditions, which allowed us to examine the influence of clay content (CC) on wave-induced liquefaction in marine sediments. The experimental results showed that the clayey sandy deposit will become prone to liquefaction with the increase of CC when CC is less than a critical value, which depends on the type of clay. However, when CC is greater than the critical value, liquefaction depth will decrease as CC increases. Furthermore, when the CC value reaches a certain level, liquefaction will not occur. For example, no liquefaction occurs when CC ≥ 33% for both kaolin-sand and illite-sand mixtures and CC ≥ 16.36% for bentonite-sand mixtures. 相似文献
29.
为解决介质圆柱体逆散射问题,提出一种新的在线逆散射方法,通过支持向量机将逆散射问题转化成一个回归估计问题. 该方法可应用于各种逆散射方面, 尤其是目标的几何与电磁参数重构和埋地目标探测. 文中首次将支持向量机方法应用到该领域,设置多个散射场的观测点,通过提取散射场的不同信息作为样本信息训练支持向量机, 建立了介质圆柱体的逆散射模型, 利用该模型重构了介质圆柱体的电磁参数,同时探测了埋地位置. 数值结果显示了该方法的有效性和准确性,为目标的实时逆散射研究提供了一种有效方法. 相似文献
30.
Direct numerical simulation was conducted to investigate the flow past a slotted cylinder at low Reynolds number (Re) of 100. The slotting of cylinder affects the boundary layer separation, vortex formation position, recirculation region length and wake width, which are determined by the type of slit. The streamwise slit (SS1), T-shaped slit (SS3) and Y-shaped slit (SS4) act as passive jets, while the transverse slit (SS2) achieves an alternate self-organized boundary layer suction and blowing. The flow rate in slits fluctuates over time due to the alternate vortex shedding and fluctuating pressure distribution around the cylinder surface. One fluctuation cycle of flow rate is caused by a pair of vortices shedding for SS2, SS3 and SS4, while it is created by each vortex shedding for SS1. The wall shear stress and flow impact on the slit wall partly contribute to the hydrodynamic forces acting on the slotted cylinder. Taking into account the internal wall of slit, the transverse slit plays the best role in suppressing the fluid forces with drag reduction of 1.7% and lift reduction of 17%. 相似文献