全文获取类型
收费全文 | 351篇 |
免费 | 56篇 |
国内免费 | 46篇 |
专业分类
测绘学 | 18篇 |
大气科学 | 29篇 |
地球物理 | 68篇 |
地质学 | 268篇 |
海洋学 | 16篇 |
天文学 | 25篇 |
综合类 | 23篇 |
自然地理 | 6篇 |
出版年
2024年 | 1篇 |
2023年 | 4篇 |
2022年 | 8篇 |
2021年 | 15篇 |
2020年 | 11篇 |
2019年 | 9篇 |
2018年 | 6篇 |
2017年 | 11篇 |
2016年 | 17篇 |
2015年 | 20篇 |
2014年 | 23篇 |
2013年 | 15篇 |
2012年 | 30篇 |
2011年 | 34篇 |
2010年 | 15篇 |
2009年 | 18篇 |
2008年 | 23篇 |
2007年 | 24篇 |
2006年 | 24篇 |
2005年 | 17篇 |
2004年 | 11篇 |
2003年 | 24篇 |
2002年 | 22篇 |
2001年 | 7篇 |
2000年 | 14篇 |
1999年 | 10篇 |
1998年 | 9篇 |
1997年 | 7篇 |
1996年 | 3篇 |
1995年 | 6篇 |
1994年 | 1篇 |
1993年 | 4篇 |
1992年 | 5篇 |
1991年 | 1篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1986年 | 1篇 |
1985年 | 1篇 |
排序方式: 共有453条查询结果,搜索用时 15 毫秒
131.
132.
The dynamic processes of bore propagation over a uniform slope are studied numerically using a 2-D Reynolds Averaged Navier–Stokes (RANS) solver, coupled to a non-linear k − ε turbulence closure and a volume of fluid (VOF) method. The dam-break mechanism is used to generate bores in a constant depth region. Present numerical results for the ensemble-averaged flow field are compared with existing experimental data as well as theoretical and numerical results based on non-linear shallow water (NSW) equations. Reasonable agreement between the present numerical solutions and experimental data is observed. Using the numerical results, small-scale bore behaviors and flow features, such as the bore collapse process near the still-water shoreline, the ‘mini-collapse’ during the runup phase and the ‘back-wash bore’ in the down-rush phase, are described. In the case of a strong bore, the evolution of the averaged turbulence kinetic energy (TKE) over the swash zone consists of two phases: in the region near the still-water shoreline, the production and the dissipation of TKE are roughly in balance; in the region farther landwards of the still-water shoreline, the TKE decay rate is very close to that of homogeneous grid turbulence. On the other hand, in the case of a weak bore, the bore collapse generated turbulence is confined near the bottom boundary layer and the TKE decays at a much slower rate. 相似文献
133.
介绍了一种基于GPRS的TCP/IP嵌入式协议转换器的设计。利用西门子MC55射频模块和嵌入式系统,设计具有标准的RS232串口到GPRS无线网络TCP/IP协议的双向转换传输设备。变传统的串口通讯为GPRS无线网络通讯,实现串口设备的快速无线联网。转换器采用透明传输的方式,用户不用知道复杂的GPRS通讯原理和TCP/IP协议,不用更改程序即可实现原有串口设备的无线网络连接。 相似文献
134.
135.
136.
黄海西部2005—2007年海雾演变的气候特征研究 总被引:2,自引:0,他引:2
海雾对沿海地区的交通运输、工农业生产等影响很大,需要开展深入研究,以探索其生消演变规律。本文选择黄海西部的成山头、青岛、海阳、日照等4个测站为代表性测站,分析了2005—2007年海雾发生期间的位势高度、海温、海表面风场、相对湿度、稳定度及散度等要素场特征,着重探讨了海雾演变的气候特征。研究结果表明:500 hPa高空槽前位于黄海上空时有利于成雾;海温异常低的年份雾日较多;风向、散度和低层的层结稳定度是影响黄海海雾的主要因素;地理位置也是影响黄海海雾变化的重要因子;黄海海雾的水平分布具有南北空间不一致的特点。 相似文献
137.
井中激电在西霞矿区的应用 总被引:3,自引:0,他引:3
以西霞矿区ZK001孔的井中激电为实例,介绍了井中激电在该矿区的应用效果及推断解释方法。说明井中激电在对地面激电异常验证中可以判断、验证钻孔是否已揭露异常体及异常体的空间展布状况。 相似文献
138.
139.
G. Beekman M. Somers T. Naylor C. Hellier 《Monthly notices of the Royal Astronomical Society》2000,318(1):9-17
We present red spectra in the region ∼ λ 7000–8300 Å of the eclipsing dwarf nova IP Peg, with simultaneous narrow-band photometry centred at 7322 Å. We show that by placing a second star on the slit we can correct for the telluric absorption bands which have hitherto made the TiO features from the secondary star unusable. We use these TiO features to carry out a radial velocity study of the secondary star, and find this gives an improvement in the signal-to-noise ratio of a factor of 2 compared with using the Na i doublet. In contrast with previous results, we find no apparent ellipticity in the radial velocity curve. As a result we revise the semi-amplitude to K 2 =331.3±5.8 km s−1 , and thus the primary and secondary star masses to 1.05-0.07 +0.14 M⊙ and 0.33-0.05 +0.14 M⊙ respectively. Although this is the lowest mass yet derived for the secondary star, it is still overmassive for its observed spectral type. However, the revised mass and radius bring IP Peg into line with other cataclysmic variables in the mass–radius–period relationships.
By fitting the phase-resolved spectra around the TiO bands to a mean spectrum, we attempt to isolate the light curve of the secondary star. The resulting light curve has marked deviations from the expected ellipsoidal shape. The largest difference is at phase 0.5, and can be explained as an eclipse of the secondary star by the disc, indicating that the disc is optically thick when viewed at high inclination angles. 相似文献
By fitting the phase-resolved spectra around the TiO bands to a mean spectrum, we attempt to isolate the light curve of the secondary star. The resulting light curve has marked deviations from the expected ellipsoidal shape. The largest difference is at phase 0.5, and can be explained as an eclipse of the secondary star by the disc, indicating that the disc is optically thick when viewed at high inclination angles. 相似文献
140.