全文获取类型
| 收费全文 | 399篇 |
| 免费 | 196篇 |
| 国内免费 | 15篇 |
专业分类
| 测绘学 | 5篇 |
| 大气科学 | 34篇 |
| 地球物理 | 457篇 |
| 地质学 | 57篇 |
| 海洋学 | 31篇 |
| 天文学 | 16篇 |
| 综合类 | 5篇 |
| 自然地理 | 5篇 |
出版年
| 2023年 | 2篇 |
| 2022年 | 9篇 |
| 2021年 | 7篇 |
| 2020年 | 28篇 |
| 2019年 | 25篇 |
| 2018年 | 11篇 |
| 2017年 | 23篇 |
| 2016年 | 17篇 |
| 2015年 | 23篇 |
| 2014年 | 28篇 |
| 2013年 | 31篇 |
| 2012年 | 27篇 |
| 2011年 | 34篇 |
| 2010年 | 22篇 |
| 2009年 | 39篇 |
| 2008年 | 35篇 |
| 2007年 | 27篇 |
| 2006年 | 21篇 |
| 2005年 | 15篇 |
| 2004年 | 14篇 |
| 2003年 | 14篇 |
| 2002年 | 17篇 |
| 2001年 | 6篇 |
| 2000年 | 11篇 |
| 1999年 | 12篇 |
| 1998年 | 18篇 |
| 1997年 | 13篇 |
| 1996年 | 9篇 |
| 1995年 | 13篇 |
| 1994年 | 11篇 |
| 1993年 | 12篇 |
| 1992年 | 9篇 |
| 1991年 | 5篇 |
| 1990年 | 3篇 |
| 1989年 | 5篇 |
| 1987年 | 2篇 |
| 1985年 | 1篇 |
| 1982年 | 1篇 |
| 1981年 | 1篇 |
| 1980年 | 1篇 |
| 1978年 | 3篇 |
| 1977年 | 2篇 |
| 1954年 | 3篇 |
排序方式： 共有610条查询结果，搜索用时 31 毫秒
91.
A series of experiments for the incipient motion of frazil particles under ice cover have been carried out in laboratory under different flow and boundary conditions.Measurements on flow velocities across the measuring cross-section at different water depths have been conducted.Based on these experiments under both ice-covered and open flow conditions,the impacts of solid boundary(such as ice cover and flume sidewall) on the distribution of flow velocity profiles have been discussed.The criteria for the inc... 相似文献
92.
In this experimental study,field observations and laboratory experiments have been carried out to assess the impacts of the vegetated channel walls and aspect ratio on flow velocity profiles,shear stress distribution and roughness coefficient of channel.Results show that the presence of vegetation cover on channel wall causes deviation of the Reynolds stress distribution from the linear one under uniform flow condition.It is also noticed that the Reynolds stress distribution is influenced by the aspect rati... 相似文献
93.
94.
95.
Vertical profiles of fluid velocity and suspended sediment concentration in nearshore 总被引：2，自引：0，他引：2
Based on the power function of velocity and the friction velocity,a velocity profile is obtained.By solving the Schmidt’s diffusion equation,an equilibrium suspended sediment concentration profile is further deduced.The profiles of velocity and suspended sediment concentration agree well with the field data,and the profile of suspended sediment concentration avoids the unreasonableness of the classical Rouse profile such as a zero value at the water surface.According to these profiles,an expression which is easy to use for calculating the suspended sediment transport rate is derived. 相似文献
96.
Both P- and S-wave arrivals were collected for imaging upper crustal structures in the source region of the April 20, 2013 Lushan earthquake. High-resolution, three- dimensional P and S velocity models were constructed by travel-time tomography. Moreover, more than 3700 after- shocks of the Lushan earthquake were relocated via a grid search method. The P- and S-wave velocity images of the upper crust show largely similar characters, with high and low velocity anomalies, which mark the presence of sig- nificant lateral and vertical heterogeneity at the source region of the Lushan earthquake. The characteristics of the velocity anomalies also reflect the associated surface geo- logical tectonics in this region. The distributions of high velocity anomalies of both P- and S-waves to 18 km depth are consistent with the distributions of relocated after- shocks, suggesting that most of the ruptures were localized inside the high velocity region. In contrast, low P and S velocities were found in the surrounding regions without aftershocks, especially in the region to the northeast of the Lushan earthquake. For the relocated aftershocks of the Lushan earthquake from this study, we found that mostaftershocks were concentrated in a zone of about 40 km long and 20 km wide, and were located in the hanging wall of Dayi-Mingshan fault. The focal depths of aftershocks increase from the southeast to the northwest region in the direction perpendicular to the fault strike, suggesting that the fault ruptured at an approximate dip angle of 45°. The main depths of the aftershocks in the northwest of the main shock are significantly shallower than expected, revealing the different seismogenic conditions in the source region. 相似文献
97.
为了研究通海盆地的地震动场地效应,在强地面运动的数值模拟计算中需要提供该地区的浅层速度结构模型.为此,在通海盆地开展了10 km高分辨率反射地震勘探和30个测点的面波联合勘探工作.综合本次探测结果与褐煤普查中的电测深和钻孔资料,得到了通海盆地的基岩埋深分布图.结果表明,在通海盆地中部,新生界厚度为100~300 m,整体表现出西南厚东北薄的趋势,盆地沉积层厚度变化明显受到小江断裂南段分支断裂的控制.浅层速度随深度分布表现出在深度相同的情况下,盆地边缘的速度高于盆地中部. 相似文献
98.
99.
100.
Predicting the velocity within the ship’s propeller jet is the initial step to investigate the scouring made by the propeller jet. Albertson et al. (1950) suggested the investigation of a submerged jet can be undertaken through observation of the plain water jet from an orifice. The plain water jet investigation of Albertson et al. (1950) was based on the axial momentum theory. This has been the basis of all subsequent work with propeller jets. In reality, the velocity characteristic of a ship’s propeller jet is more complicated than a plain water jet. Fuehrer and Römisch (1977), Blaauw and van de Kaa (1978), Berger et al. (1981), Verhey (1983) and Hamill (1987) have carried out investigations using physical model. Current paper reviews the state-of-art of the equations used to predict the time-averaged axial, tangential and radial components of velocity within the zone of flow establishment and the zone of established flow of a ship’s propeller jet. 相似文献