全文获取类型
收费全文 | 3156篇 |
免费 | 119篇 |
国内免费 | 29篇 |
专业分类
测绘学 | 106篇 |
大气科学 | 285篇 |
地球物理 | 722篇 |
地质学 | 1097篇 |
海洋学 | 304篇 |
天文学 | 521篇 |
综合类 | 13篇 |
自然地理 | 256篇 |
出版年
2021年 | 42篇 |
2020年 | 41篇 |
2019年 | 44篇 |
2018年 | 87篇 |
2017年 | 61篇 |
2016年 | 89篇 |
2015年 | 57篇 |
2014年 | 86篇 |
2013年 | 156篇 |
2012年 | 115篇 |
2011年 | 175篇 |
2010年 | 142篇 |
2009年 | 179篇 |
2008年 | 161篇 |
2007年 | 113篇 |
2006年 | 121篇 |
2005年 | 120篇 |
2004年 | 101篇 |
2003年 | 95篇 |
2002年 | 97篇 |
2001年 | 66篇 |
2000年 | 82篇 |
1999年 | 81篇 |
1998年 | 71篇 |
1997年 | 63篇 |
1996年 | 56篇 |
1995年 | 49篇 |
1994年 | 42篇 |
1993年 | 46篇 |
1992年 | 35篇 |
1991年 | 40篇 |
1990年 | 25篇 |
1989年 | 23篇 |
1988年 | 19篇 |
1987年 | 42篇 |
1986年 | 21篇 |
1985年 | 28篇 |
1984年 | 34篇 |
1983年 | 32篇 |
1982年 | 40篇 |
1981年 | 25篇 |
1980年 | 31篇 |
1979年 | 22篇 |
1978年 | 21篇 |
1977年 | 22篇 |
1976年 | 25篇 |
1975年 | 25篇 |
1974年 | 21篇 |
1973年 | 19篇 |
1971年 | 17篇 |
排序方式: 共有3304条查询结果,搜索用时 46 毫秒
1.
Martin Muravchik Gijs A. Henstra Gauti T. Eliassen Rob L. Gawthorpe Mike Leeder Haralambos Kranis Emmanuel Skourtsos Julian Andrews 《Basin Research》2020,32(5):1184-1212
Our current understanding on sedimentary deep-water environments is mainly built of information obtained from tectonic settings such as passive margins and foreland basins. More observations from extensional settings are particularly needed in order to better constrain the role of active tectonics in controlling sediment pathways, depositional style and stratigraphic stacking patterns. This study focuses on the evolution of a Plio-Pleistocene deep-water sedimentary system (Rethi-Dendro Formation) and its relation to structural activity in the Amphithea fault block in the Corinth Rift, Greece. The Corinth Rift is an active extensional basin in the early stages of rift evolution, providing perfect opportunities for the study of early deep-water syn-rift deposits that are usually eroded from the rift shoulders due to erosion in mature basins like the Red Sea, North Sea and the Atlantic rifted margin. The depocentre is located at the exit of a structurally controlled sediment fairway, approximately 15 km from its main sediment source and 12 km basinwards from the basin margin coastline. Fieldwork, augmented by digital outcrop techniques (LiDAR and photogrammetry) and clast-count compositional analysis allowed identification of 16 stratigraphic units that are grouped into six types of depositional elements: A—mudstone-dominated sheets, B—conglomerate-dominated lobes, C—conglomerate channel belts and sandstone sheets, D—sandstone channel belts, E—sandstone-dominated broad shallow lobes, F—sandstone-dominated sheets with broad shallow channels. The formation represents an axial system sourced by a hinterland-fed Mavro delta, with minor contributions from a transverse system of conglomerate-dominated lobes sourced from intrabasinal highs. The results of clast compositional analysis enable precise attribution for the different sediment sources to the deep-water system and their link to other stratigraphic units in the area. Structures in the Amphithea fault block played a major role in controlling the location and orientation of sedimentary systems by modifying basin-floor gradients due to a combination of hangingwall tilt, displacement of faults internal to the depocentre and folding on top of blind growing faults. Fault activity also promoted large-scale subaqueous landslides and eventual uplift of the whole fault block. 相似文献
2.
3.
Anita Enmark Thomas Berkefeld Oskar von der Lühe Torben Andersen 《Experimental Astronomy》2006,21(2):87-99
A simulation model of the adaptive optics of the German Vacuum Tower Telescope (VTT), Observatorio del Teide, Tenerife, is
presented. The model uses modules from the integrated model of the Euro50 extremely large telescope, and includes submodels
of a Shack-Hartmann wavefront sensor, a de-formable mirror, a tip-tilt mirror, high-voltage amplifier low-pass filters, a
reconstructor and a controller. We investigate the impact on the closed loop bandwidth of changes in controller configuration
and certain system parameters, such as low pass filter bandwidth and camera integration and readout time. Control strategies
were tested on simple models before implementation on the full VTT model. Using the models, different control strategies are
compared. 相似文献
4.
Samuel Lévêque Bertrand Koehler Oskar von der Lühe 《Astrophysics and Space Science》1996,239(2):305-314
The Very Large Telescope Interferometer [1,13] will be operated in air which will introduce small optical path fluctuations due to internal turbulence [4,6] and dispersion effects. Both may contribute to fringe contrast decrease. Longitudinal dispersion effects can be corrected by inserting an appropriate glass of variable thickness in one arm of the interferometer [3,5,11,12]. This paper presents a new method applied to VLTI in order to select the optimum glass, according to both the observing wavelength and the spectral bandpath, and to calculate its thickness. Results are presented in terms of improvement on the fringe contrast. 相似文献
5.
K. A. van der Hucht 《Astronomy and Astrophysics Review》1992,4(2):123-159
Summary Recent literature on Population I Wolf-Rayet star research extending from the Milky Way to blue compact dwarf galaxies is reviewed, broken down into inventory, basic parameters and galactic distribution, atmospheres, binaries, intrinsic variability, mass loss, enrichment and evolution. Also the incidence of Wolf-Rayet stars with variable non-thermal radio emission, excess X-ray fluxes, and episodic/periodic IR excesses is reviewed. These phenomena appear to be associated with wind-wind interaction in wide long-period WR+OB binaries and with wind-compact object interaction in WR+c binaries, with orbit sizes of the order of magnitude of the WR radio photosphere sizes or larger. 相似文献
6.
7.
We have recently put forward a ‘unified’ semi-empirical model for the coupling between accretion and jet production in galactic
black hole X-ray binaries. In this paper, we summarise this model and briefly discuss relevant considerations that have arisen
since its publication. 相似文献
8.
P. A. M. Van Hoof M. E. Foord R. F. Heeter J. E. Bailey H.-K. Chung M. E. Cuneo W. H. Goldstein V. Jonauskas F. P. Keenan R. Kisielius D. A. Liedahl C. Ramsbottom S. J. Rose P. T. Springer R. S. Thoe 《Astrophysics and Space Science》2005,298(1-2):147-153
In experiments at the high-power Z-facility at Sandia National Laboratory in Albuquerque, New Mexico, we have been able to
produce a low density photoionized laboratory plasma of Fe mixed with NaF. The conditions in the experiment allow a meaningful
comparison with X-ray emission from astrophysical sources. The charge state distributions of Fe, Na and F are determined in
this plasma using high resolution X-ray spectroscopy. Independent measurements of the density and radiation flux indicate
unprecedented values for the ionization parameter ξ = 20–25 erg cm s−1 under nearly steady-state conditions. First comparisons of the measured charge state distributions with X-ray photoionization
models show reasonable agreement, although many questions remain. 相似文献
9.
Angelika van der Linde 《Mathematical Geology》1993,25(1):1-7
Least squares estimation (LSE) is theoretically related to quadratic unbiased estimation of variance components. It is argued that these methods of estimation of variance components essentially generalize LSE though they are not formally equivalent. 相似文献
10.
Rob Fender 《Astrophysics and Space Science》2003,288(1-2):79-95
I report the detection of circular polarisation, associated with relativistic ejections, from the `microquasar' GRS 1915+105. I further compare detections and limits of circular polarisation and circular-to-linear polarisation ratios in other X-ray binaries. Since in at least two cases the dominance of linear over circular polarisation or vice versa is a function of frequency, this seems to indicate that this is a strong function of depolarisation in the source. Furthermore, I note that circular polarisation has only been detected from sources whose jets lie close to the plane of the sky, where as we have quite stringent limits on the circular polarisation of jets which lie close to the line of sight. 相似文献