全文获取类型
收费全文 | 4602篇 |
免费 | 870篇 |
国内免费 | 1131篇 |
专业分类
测绘学 | 702篇 |
大气科学 | 758篇 |
地球物理 | 1305篇 |
地质学 | 2005篇 |
海洋学 | 792篇 |
天文学 | 47篇 |
综合类 | 463篇 |
自然地理 | 531篇 |
出版年
2024年 | 8篇 |
2023年 | 36篇 |
2022年 | 129篇 |
2021年 | 143篇 |
2020年 | 207篇 |
2019年 | 221篇 |
2018年 | 187篇 |
2017年 | 203篇 |
2016年 | 224篇 |
2015年 | 242篇 |
2014年 | 289篇 |
2013年 | 330篇 |
2012年 | 357篇 |
2011年 | 382篇 |
2010年 | 302篇 |
2009年 | 377篇 |
2008年 | 323篇 |
2007年 | 427篇 |
2006年 | 308篇 |
2005年 | 288篇 |
2004年 | 266篇 |
2003年 | 225篇 |
2002年 | 166篇 |
2001年 | 144篇 |
2000年 | 121篇 |
1999年 | 105篇 |
1998年 | 116篇 |
1997年 | 81篇 |
1996年 | 69篇 |
1995年 | 49篇 |
1994年 | 53篇 |
1993年 | 67篇 |
1992年 | 33篇 |
1991年 | 27篇 |
1990年 | 21篇 |
1989年 | 25篇 |
1988年 | 22篇 |
1987年 | 8篇 |
1986年 | 3篇 |
1985年 | 8篇 |
1984年 | 1篇 |
1983年 | 3篇 |
1982年 | 1篇 |
1979年 | 1篇 |
1977年 | 2篇 |
1975年 | 1篇 |
1954年 | 2篇 |
排序方式: 共有6603条查询结果,搜索用时 15 毫秒
91.
92.
93.
Introduction Receiver function has been extensively applied in studying S wave velocity of crust and up-per mantle for about 20 years (Owens, et al, 1987; LIU, et al, 1996), which is a time series ob-tained by the deconvolution of vertical component from horizontal component for teleseismic P waveform. Receiver function represents the teleseismic P plane wave response of crust and upper mantle beneath seismic station, from which the source and propagation effects are removed. Receiver funct… 相似文献
94.
A new algorithm to correct the orientation error of the accelerometerat the Dahan Downhole Array, Hualien, Taiwan is developed. This algorithmconsists of three stages: (1) rotating two horizontal ground motions on thefree surface to the SH-SVdirection and SH axis offers a reference direction.(2) computing the synthetic downhole SH waves at a downhole station and (3)searching a rotation angle for downhole observation that yields a best waveformmatch between the synthetic and observed downhole seismograms. At this point, the rotated angle corresponding to the best waveform match can be considered as the orientation error. We selected five earthquakes with good data qualityfor analysis. Results show that this algorithm gives a more stable estimationthan a conventional method because it allows the selection of data from a wider time window for analyses. The estimated orientation error of the accelerometers at the Dahan Downhole Array after the 1999 reinstallation are40°, 114° and 285° at depths of 50, 100 and 200 m, respectively. 相似文献
95.
Migration characteristics of dense non-aqueous phase liquids (DNAPLs) in the subsurface can be expressed as a water–DNAPL two-phase system based on mainly the k–S–p relations, which describe the relations among relative permeability (k), degree of water saturation (S), and capillary pressure head (p). The aims of this research are to develop an experimental system with new type of probes, such as the electrical conductivity probe for measuring the degree of water saturation and the hydrophilic and hydrophobic tensiometer for measuring the pore water and DNAPL pressures, and also to estimate the results obtained from the developed experimental system. From these tests, the excellent k–S–p relations were obtained and the efficiency and validity of this developed experimental system have been confirmed in terms of the concept of the scaling coefficient calculated by interfacial tensions. 相似文献
96.
97.
98.
99.
100.
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