全文获取类型
收费全文 | 2047篇 |
免费 | 244篇 |
国内免费 | 272篇 |
专业分类
测绘学 | 573篇 |
大气科学 | 166篇 |
地球物理 | 576篇 |
地质学 | 570篇 |
海洋学 | 248篇 |
天文学 | 87篇 |
综合类 | 145篇 |
自然地理 | 198篇 |
出版年
2024年 | 8篇 |
2023年 | 15篇 |
2022年 | 44篇 |
2021年 | 70篇 |
2020年 | 64篇 |
2019年 | 93篇 |
2018年 | 53篇 |
2017年 | 88篇 |
2016年 | 86篇 |
2015年 | 95篇 |
2014年 | 113篇 |
2013年 | 134篇 |
2012年 | 138篇 |
2011年 | 107篇 |
2010年 | 95篇 |
2009年 | 113篇 |
2008年 | 117篇 |
2007年 | 147篇 |
2006年 | 130篇 |
2005年 | 101篇 |
2004年 | 113篇 |
2003年 | 101篇 |
2002年 | 65篇 |
2001年 | 54篇 |
2000年 | 65篇 |
1999年 | 58篇 |
1998年 | 51篇 |
1997年 | 30篇 |
1996年 | 41篇 |
1995年 | 30篇 |
1994年 | 25篇 |
1993年 | 22篇 |
1992年 | 20篇 |
1991年 | 14篇 |
1990年 | 18篇 |
1989年 | 8篇 |
1988年 | 10篇 |
1987年 | 9篇 |
1986年 | 1篇 |
1985年 | 3篇 |
1984年 | 3篇 |
1983年 | 1篇 |
1982年 | 4篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1954年 | 1篇 |
排序方式: 共有2563条查询结果,搜索用时 952 毫秒
41.
42.
Masao Komazawa Hitoshi Morikawa Kajuro Nakamura Junpei Akamatsu Keiichi Nishimura Sumio Sawada Ayfer Erken Akin Onalp 《Soil Dynamics and Earthquake Engineering》2002,22(9-12):829-836
The 1999 Kocaeli earthquake brought serious damage to downtown of Adapazari. To study why strong motions were generated at the town, a bedrock structure was investigated on the basis of Bouguer gravity anomaly, and SPAC and H/V analyses of microseisms. It was revealed that, the basin consists of three narrow depressions of bedrock with very steep edges, extending in E–W or NE–SW directions along the North Anatolia faults, and the depth to bedrock reaches 1000 m or more. Downtown of Adapazari is located 1–2 km apart from the basin-edge. It is considered that, the specific configuration of bedrock amplifies ground motions at the downtown area by focusing of seismic waves and/or interference between incident S-waves and surface-waves secondarily generated at the basin-edge. Studying 3D bedrock structure is an urgent issue for microzoning an urban area in a sedimentary basin. 相似文献
43.
44.
In continent Lg is usually one of the predominant phases recorded by short-period or broad-band seismometers. A ray-theoretical approach shows that Lg wave is the superposition of higher-mode surface waves propagating in the continental crust[1—4]. The g… 相似文献
45.
A method, based on the Hilbert–Huang spectral analysis, has been proposed by the authors to identify linear structures in which normal modes exist (i.e., real eigenvalues and eigenvectors). Frequently, all the eigenvalues and eigenvectors of linear structures are complex. In this paper, the method is extended further to identify general linear structures with complex modes using the free vibration response data polluted by noise. Measured response signals are first decomposed into modal responses using the method of Empirical Mode Decomposition with intermittency criteria. Each modal response contains the contribution of a complex conjugate pair of modes with a unique frequency and a damping ratio. Then, each modal response is decomposed in the frequency–time domain to yield instantaneous phase angle and amplitude using the Hilbert transform. Based on a single measurement of the impulse response time history at one appropriate location, the complex eigenvalues of the linear structure can be identified using a simple analysis procedure. When the response time histories are measured at all locations, the proposed methodology is capable of identifying the complex mode shapes as well as the mass, damping and stiffness matrices of the structure. The effectiveness and accuracy of the method presented are illustrated through numerical simulations. It is demonstrated that dynamic characteristics of linear structures with complex modes can be identified effectively using the proposed method. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
46.
时间谱电阻率法中的剩余电磁效应研究 总被引:2,自引:0,他引:2
根据频谱激电(SIP)法或复电阻率(CR)法中研究剩余电磁(REM)效应的思想,通过分析时间谱电阻率(TSR)法中场的基本特征,在TSR法中建立了与SIP(或CR)法中参数Φmax/Φ0max相类似的参数-Emax/E0,用来描述了TSR法中的REM效应。通过对一维可极化大地模型的REM效应的理论计算,验证了用Emax/E0表示的REM异常可用来形象地反映地电断面电阻率的高低。 相似文献
47.
电子地图的数据交换(CNSDTF)实现 总被引:4,自引:2,他引:4
电子地图是传统地图的矢量数据格式,由于采用不同的软件平台和不同的数据格式,因此在进行数据交换和数据共享时经常需要进行数据格式的转换。中国《地球空间数据交换格式》标准中给出了矢量数据交换的标准格式,对于GIS应用中的矢量数据交换基本已满足要求,但对于电子地图的交换尚有不足。本文在认真研究了电子地图的一般特征后,提出了电子地图所具备的图形表现属性不同于非图形属性的概念,在不违背标准的基本原则下扩充了现有标准的格式,大大方便了电子地图数据的交换,并且给出了程序实现的简要流程。 相似文献
48.
49.
50.
The basic concepts of spectral and multiscale selective reconstruction of (geophysically relevant) vector fields on the sphere from error-affected data is outlined in detail. The reconstruction mechanism is formulated under the assumption that spectral as well as multiscale approximation is well-representable in terms of only a certain number of expansion coefficients at the various resolution levels. It is shown that spectral denoising by means of orthogonal expansions in terms of vector spherical harmonics reflects global a priori information of the noise (e.g., in form of a covariance tensor field), whereas multiscale signal-to-noise thresholding can be performed under locally dependent noise information within a multiresolution analysis in terms of spherical vector wavelets. An application of the multiscale formalism to Earth's magnetic field determination is presented. 相似文献