全文获取类型
收费全文 | 6516篇 |
免费 | 1207篇 |
国内免费 | 1569篇 |
专业分类
测绘学 | 616篇 |
大气科学 | 1010篇 |
地球物理 | 1469篇 |
地质学 | 3620篇 |
海洋学 | 928篇 |
天文学 | 332篇 |
综合类 | 537篇 |
自然地理 | 780篇 |
出版年
2024年 | 65篇 |
2023年 | 188篇 |
2022年 | 430篇 |
2021年 | 471篇 |
2020年 | 396篇 |
2019年 | 400篇 |
2018年 | 448篇 |
2017年 | 413篇 |
2016年 | 425篇 |
2015年 | 382篇 |
2014年 | 416篇 |
2013年 | 390篇 |
2012年 | 353篇 |
2011年 | 394篇 |
2010年 | 350篇 |
2009年 | 353篇 |
2008年 | 298篇 |
2007年 | 276篇 |
2006年 | 207篇 |
2005年 | 224篇 |
2004年 | 206篇 |
2003年 | 222篇 |
2002年 | 350篇 |
2001年 | 271篇 |
2000年 | 240篇 |
1999年 | 237篇 |
1998年 | 132篇 |
1997年 | 108篇 |
1996年 | 94篇 |
1995年 | 89篇 |
1994年 | 86篇 |
1993年 | 64篇 |
1992年 | 68篇 |
1991年 | 41篇 |
1990年 | 38篇 |
1989年 | 20篇 |
1988年 | 19篇 |
1987年 | 16篇 |
1986年 | 15篇 |
1985年 | 15篇 |
1984年 | 14篇 |
1983年 | 7篇 |
1982年 | 12篇 |
1981年 | 11篇 |
1980年 | 6篇 |
1979年 | 3篇 |
1976年 | 3篇 |
1958年 | 4篇 |
1957年 | 2篇 |
1954年 | 5篇 |
排序方式: 共有9292条查询结果,搜索用时 15 毫秒
1.
Vertical drains are usually installed in subsoil consisting of several layers. Due to the complex nature of the problem, over the past decades, the consolidation properties of multi‐layered ground with vertical drains have been analysed mainly by numerical methods. An analytical solution for consolidation of double‐layered ground with vertical drains under quasi‐equal strain condition is presented in this paper. The main steps for the computation procedure are listed. The convergence of the series solution is discussed. The comparisons between the results obtained by the present analytical method and the existing numerical solutions are described by figures. The orthogonal relation for the system of double‐layered ground with vertical drains is proven. Finally, some consolidation properties of double‐layered ground with vertical drains are analysed. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
2.
DEVELOPMENTSTRATEGIESOFWATERANDLANDRESOURCESINTHEHEXIREGION,CHINA肖洪浪,高前兆,李福兴DEVELOPMENTSTRATEGIESOFWATERANDLANDRESOURCESINTHE... 相似文献
3.
张晓晖 《成都信息工程学院学报》2002,17(3):166-169
通过对影响能见度的因素的分析,提出了一种能见度预报方法-综合分析法,极大地提高了能见度的预报准确率。 相似文献
4.
本文报告一种用半导体激光器作光源,用子脉冲宽度100ns,长度为511的周期伪随机码对半导体激光器的输出作幅度调制;APD作光电检测器,高速数字信号处理器TMS320C25作信号处理的激光雷达组成方案和试作样机的实验结果。 相似文献
5.
In this paper the tidal phenomena on the Earth are concisely specified, including solid tides, ocean tides and atmospheric tides due to the luni-solar tide-generating force, and the Earth pole tide due to the motion of the Earth's rotation axis (polar motion); as well as their effects on the Earth rotation. The outcomes of scientific researches of Chinese astronomers on these topics are described in some detail. These researches deal with the mechanisms responsible for tidal effects on the earth rotation, and on the measurements of the Earth rotation parameters. Finally, the effects discovered by Chinese researchers on the measurements of the period and change in period of pulsars are discussed. These effects are very small in magnitude but not negligible. 相似文献
6.
本文叙述南天区 5GHzVLBI普查中新发现的视超光速射电源 ,0 4 2 0— 0 1 4,1 334—1 2 7和 2 345— 1 67,这些结果尚待进一步的观测加以证实 相似文献
7.
网络安全是近年来研究的热点,各种新技术不断涌现,身份认证是安全应用中最重要的一个问题,也是PKI的核心服务之一。PKI作为信息安全的基石经过几年的发展不断走向成熟,在许多领域发挥着重要的作用。针对目前对PKI中的重要部件RA的研究很少的状况,着重对RA的实现模型进行了探讨。 相似文献
8.
The inception and growth of the active Carpino-Le Piane Basin Fault System (CLPBFS; central-southern Apennines, Italy) was analysed with respect to the neighbouring Isernia and Surrounding (ISFS) and Boiano Basin (BBFS) extensional Fault Systems. 39Ar–40Ar dating showed that the BBFS was already active 649 ± 21 ka bp and that the ISFS was active at least 476 ±10 ka bp , whereas the activity of the CLPBFS started certainly later than 253 ± 22 ka bp , and very probably as recently as <28 ka bp . These ages, combined with structural data (geometry and kinematics of the fault systems), indicate that the inception and development of the CLPBFS could be strictly related to the stress changes caused by earthquakes occurring on the BBFS. 相似文献
9.
G. Palladino A. Basili G. Di Cocco T. Franceschini G. Landini S. Silvestri A. Barbini M. Galimberti L. A. Gizzi 《Experimental Astronomy》2006,21(3):169-187
This paper describes the design of a star sensor based upon a high dynamic range CCD in order to reach an arcsec-level attitude
determination in balloon-borne missions. A custom star identification software was developed and laboratory-tested on a prototype
assembled using commercial components. A set of numerical simulations have been carried out to study the dependence on the
pointing precision of the centroid position accuracy, the number of detected stars and the effect of the image focusing. Moreover,
the role of the electronic noise and the discrete pixel structure on the light signals is identified by the analysis of numerical
simulations. Laboratory tests confirm that the arcsec pointing accuracy with a 1 Hz update rate can be achieved with our combination
of custom-developed software and selected hardware components. 相似文献