全文获取类型
收费全文 | 198篇 |
免费 | 33篇 |
国内免费 | 19篇 |
专业分类
测绘学 | 5篇 |
大气科学 | 12篇 |
地球物理 | 67篇 |
地质学 | 46篇 |
海洋学 | 99篇 |
天文学 | 1篇 |
综合类 | 13篇 |
自然地理 | 7篇 |
出版年
2023年 | 2篇 |
2022年 | 6篇 |
2021年 | 6篇 |
2020年 | 8篇 |
2019年 | 9篇 |
2018年 | 4篇 |
2017年 | 6篇 |
2016年 | 15篇 |
2015年 | 6篇 |
2014年 | 11篇 |
2013年 | 10篇 |
2012年 | 8篇 |
2011年 | 15篇 |
2010年 | 10篇 |
2009年 | 11篇 |
2008年 | 16篇 |
2007年 | 15篇 |
2006年 | 12篇 |
2005年 | 11篇 |
2004年 | 6篇 |
2003年 | 4篇 |
2002年 | 13篇 |
2001年 | 4篇 |
2000年 | 8篇 |
1999年 | 3篇 |
1998年 | 8篇 |
1997年 | 6篇 |
1996年 | 4篇 |
1995年 | 1篇 |
1994年 | 4篇 |
1993年 | 1篇 |
1991年 | 5篇 |
1989年 | 2篇 |
排序方式: 共有250条查询结果,搜索用时 15 毫秒
51.
纵横波联合勘探可以得到更多关于岩石圈层岩性、物性等介质属性方面的信息,有效提高地壳物质组成的约束性.在纵波速度结构模型的基础上,通过射线追踪和走时拟合对OBS2006-3地震剖面径向分量的转换震相进行了横波速度结构模拟.结果表明:沉积层1、沉积层2的横波速度分别为0.7~0.9 km/s和1.6~1.7 km/s,波速比由2.64~3.16变化到2.41左右,较高的波速比表明沉积层固结程度不高;中生代沉积层横波速度由浅部的2.6 km/s增大到3.0 km/s,波速比为1.74~1.80;地壳中波速比为1.74~1.82,表明该剖面地壳为陆壳性质;下地壳高速层的横波速度为4.0~4.2 km/s,纵横波速比为1.73~1.78,揭示高速层的物质组成为铁镁质的基性岩,推断其与海底扩张停止之后的岩浆底侵作用有关. 相似文献
52.
依据渤海湾盆地2000余口测温井的地温梯度数据、地层岩性描述、分层数据以及钻井资料,计算了该盆地各生油岩系底界面的温度。统计结果表明:渤海湾盆地沙河街组大部分凹陷区地层底界面温度介于90℃至150℃,目前仍具有大量生油的温度条件,而在隆起或一些凸起地区,该地层组段温度普遍小于90℃,未能达到生油的温度指标。东营组和孔店组地层也仍具有一定的生油温度条件。研究还表明:地层温度与地层界面埋深密切相关,温度随界面埋深的增大而升高,沉积厚度大的凹陷区地层界面温度大于沉积厚度小的凸起区或斜坡地带,说明地层界面埋深是决定地温高低的主要控制因素,而地温梯度对地层界面温度的影响相对较小。 相似文献
53.
由于电磁波无法在水中传播,导致海底地震仪(OBS)与全球定位系统(GPS)无法进行实时对钟,因此会产生一定的时钟漂移.而受船时、海况等影响,被动源OBS在回收后往往电量亏损,致使设备回收时并没有完成对钟,无法直接利用对钟前后的时钟漂移量进行线性校正.本文选取中国科学院海洋研究所2016—2017年间在雅浦俯冲带进行的长周期被动源OBS实验所获得的数据,利用背景噪声互相关方法对OBS进行了时间校正.结果发现,各OBS在经过一年左右时间的布放后,时钟漂移量在1~3 s之间,且基本呈线性趋势,将该结果平均分配到每天从而完成线性校正.另外,探讨了时钟的非线性漂移、误差源、参考台站的选取等因素对时钟准确度的影响,为OBS的数据处理进行了有益的探索. 相似文献
54.
55.
56.
Sarah M. Mardon James C. Hower Jennifer M.K. O'Keefe Maria N. Marks Daniel H. Hedges 《International Journal of Coal Geology》2008,75(4):248-254
Fly ashes from two stoker boilers burning Pennsylvanian Eastern Kentucky high volatile A bituminous coal blends were examined for their petrology and chemistry. The source coals have similar trace element contents. One of the ash collection systems was retrofitted with a baghouse (fabric filter) system, collecting a finer fly ash at a cooler flue gas temperature than the plant that has not been reconfigured. The baghouse ash has a markedly higher trace element content than the coarser fly ash from the other plant. The enhanced trace element content is most notable in the As concentration, reaching nearly 9000 ppm (ash basis) for one of the collection units. Differences in the ash chemistry are not due to any substantial differences in the coal source, even though the coal sources were from different counties and from different coal beds, but rather to the improved pollution control system in the steam plant with the higher trace element contents. 相似文献
57.
Since 1979, China's Open Door policy has attracted increasing foreign investment. To maintain global competitiveness, the British confectioner, Cadbury, authorised its Australian subsidiary to develop a chocolate plant in China. This paper details the decision‐making processes that eventually led to a new factory on a greenfield site near Beijing. It also illustrates some of the adaptations that Cadbury has had to make in its product and production procedures in order to match its own standards for dairy milk chocolate and yet accommodate guo qing (the special situation in China). 相似文献
58.
The Sanmenxia Project completed in 1960 is a multi-purpose hydro project with emphasis on flood control. After the expounding, serious deposition occurs in the upstream part of the reservoir and the Weihe River. The project has to be rebuilt twice in the period from 1964 to 1978. Thus the discharge capacity is greatly enlarged by excavating two side tunnels on the left bank, converting three penstocks into sluice conduits and reopening & bottom outlets formerly used for di- version. By changing the operational mode from storing water year round to stor- ing clear water during the dry season and sluicing sediment during the flood season, the sediment problem of the reservoir is largely solved and multi-purpose benefits of the project are partially retained. But the heavy sediment load still caused serious abrasion on bottom outlets and turbines, particularly on the inlet gate slot, the service gate slot and the floor. Much effort has been made to clarify the mechanism of the damage and to choose abrasion-resistant material for repair. The repair of the bottom outlets has been going on since 1980. This paper describes the abrasion on the bottom outlets in details and the subsequent repair effected. 相似文献
59.
A numerical investigation of the bottom pressure and wave elevation generated by a planing hull in finite-depth water is presented. While the existing literature addresses the free-surface deformation and pressure field at the seafloor independently, this work proposes a direct comparison between the two hydrodynamic quantities. The dependence of the pressure disturbances at the ocean floor from the waves generated at the free-surface by a planing hull is studied for several values of both the depth and hull Froude numbers. The methodology employed is Smoothed Particle Hydrodynamics (SPH), a numerical technique based on the discretization of the continuum fields of hydrodynamics through mesh-less particles. The SPH code herein chosen is initially validated against experimental data for transom-stern flow. Subsequently, numerical simulations are presented for a planing hull in high-speed regimes. The results show a direct correlation between surface wave dynamics and hydrodynamic pressure disturbances at the seafloor as the value of the Froude number is varied. This is assessed by studying the inverse dependence of the low-pressure wake angle with the Froude number and by comparison of SPH results with similar works in the cited literature. 相似文献
60.