全文获取类型
收费全文 | 322篇 |
免费 | 16篇 |
国内免费 | 18篇 |
专业分类
测绘学 | 4篇 |
大气科学 | 18篇 |
地球物理 | 106篇 |
地质学 | 121篇 |
海洋学 | 14篇 |
天文学 | 64篇 |
综合类 | 10篇 |
自然地理 | 19篇 |
出版年
2024年 | 2篇 |
2023年 | 2篇 |
2022年 | 6篇 |
2021年 | 5篇 |
2020年 | 7篇 |
2019年 | 10篇 |
2018年 | 27篇 |
2017年 | 18篇 |
2016年 | 19篇 |
2015年 | 27篇 |
2014年 | 20篇 |
2013年 | 31篇 |
2012年 | 22篇 |
2011年 | 27篇 |
2010年 | 20篇 |
2009年 | 13篇 |
2008年 | 14篇 |
2007年 | 17篇 |
2006年 | 7篇 |
2005年 | 7篇 |
2004年 | 11篇 |
2003年 | 5篇 |
2002年 | 13篇 |
2001年 | 6篇 |
2000年 | 6篇 |
1999年 | 3篇 |
1998年 | 2篇 |
1997年 | 2篇 |
1996年 | 1篇 |
1995年 | 2篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1989年 | 1篇 |
排序方式: 共有356条查询结果,搜索用时 640 毫秒
331.
Sergey M. Kudryavtsev 《Celestial Mechanics and Dynamical Astronomy》1995,61(3):207-215
A high-precise analytical theory of a satellite in orbit around a non-spherical planet has been developed. The Poisson's small parameter method has been used. All secular and short-periodic perturbations proportional up to and including a product of five arbitrary harmonic coefficients of the planetary potential expansion are calculated. Long-periodic perturbations are derived with the accuracy of up to the fourth-order, inclusive. The influence of the high-order perturbations on the motion of ETALON-1 satellite has been investigated. The results of comparison of the numerical and analytical integration of the equations of its motion over a five year interval are as follows:
The theory is intended to be used for processing precise laser range measurements of the Earth geodynamical satellites over long-term intervals. 相似文献
| - the r.m.s. difference between the positions is 1.1 cm; |
| - the r.m.s. difference between the ranges is 0.5 cm. |
332.
333.
On anelliptic approximations for qP velocities in VTI media 总被引:5,自引:1,他引:5
Sergey Fomel 《Geophysical Prospecting》2004,52(3):247-259
A unified approach to approximating phase and group velocities of qP seismic waves in a transversely isotropic medium with vertical axis of symmetry (VTI) is developed. While the exact phase‐velocity expressions involve four independent parameters to characterize the elastic medium, the proposed approximate expressions use only three parameters. This makes them more convenient for use in surface seismic experiments, where the estimation of all four parameters is problematic. The three‐parameter phase‐velocity approximation coincides with the previously published ‘acoustic’ approximation of Alkhalifah. The group‐velocity approximation is new and noticeably more accurate than some of the previously published approximations. An application of the group‐velocity approximation for finite‐difference computation of traveltimes is shown. 相似文献
334.
Interannual variations of total copepod abundance in the Gulf of Maine (1961-1991) are analyzed and related to the semi-permanent atmospheric pressure systems: Icelandic Low (IL) and the Azores High (AH). These centers of action dominate atmospheric and oceanic circulation in the North Atlantic. Cross-correlation analysis of zooplankton, sea surface temperature (SST) and the atmospheric characteristics have revealed different (from one to three years) time lags between the above characteristics. A multiple stepwise regression analysis gave a correlation value of 0.7 between observed and predicted interannual changes of total copepod abundance. A discussion is included of possible mechanisms that may contribute to the dynamic links that transfer atmospheric variation into observed changes in zooplankton abundance. 相似文献
335.
336.
Horizontal wells or radial collector wells are used in shallow aquifers to enhance water withdrawal rates. Groundwater flow patterns near these wells are three-dimensional (3D), but difficult to represent in a 3D numerical model because of the high degree of grid refinement needed. However, for the purpose of designing water withdrawal systems, it is sufficient to obtain the correct production rate of these wells for a given drawdown. We developed a Cauchy boundary condition along a horizontal well in a Dupuit-Forchheimer model. Such a steady-state 2D model is not only useful for predicting groundwater withdrawal rates but also for capture zone delineation in the context of source water protection. A comparison of our Dupuit-Forchheimer model for a radial collector well with a 3D model yields a nearly exact production rate. Particular attention is given to horizontal wells that extend underneath a river. A comparison of our approach with a 3D solution for this case yields satisfactory results, at least for moderate-to-large river bottom resistances. 相似文献
337.
Christina Neal Olga Girina Sergey Senyukov Alexander Rybin Jeffrey Osiensky Pavel Izbekov Gail Ferguson 《Natural Hazards》2009,51(2):245-262
More than 65 potentially active volcanoes on the Kamchatka Peninsula and the Kurile Islands pose a substantial threat to aircraft on the Northern Pacific (NOPAC), Russian Trans-East (RTE), and Pacific Organized Track System (PACOTS) air routes. The Kamchatka Volcanic Eruption Response Team (KVERT) monitors and reports on volcanic hazards to aviation for Kamchatka and the north Kuriles. KVERT scientists utilize real-time seismic data, daily satellite views of the region, real-time video, and pilot and field reports of activity to track and alert the aviation industry of hazardous activity. Most Kurile Island volcanoes are monitored by the Sakhalin Volcanic Eruption Response Team (SVERT) based in Yuzhno-Sakhalinsk. SVERT uses daily moderate resolution imaging spectroradiometer (MODIS) satellite images to look for volcanic activity along this 1,250-km chain of islands. Neither operation is staffed 24 h per day. In addition, the vast majority of Russian volcanoes are not monitored seismically in real-time. Other challenges include multiple time-zones and language differences that hamper communication among volcanologists and meteorologists in the US, Japan, and Russia who share the responsibility to issue official warnings. Rapid, consistent verification of explosive eruptions and determination of cloud heights remain significant technical challenges. Despite these difficulties, in more than a decade of frequent eruptive activity in Kamchatka and the northern Kuriles, no damaging encounters with volcanic ash from Russian eruptions have been recorded. 相似文献
338.
Geomorphological evidence for the Late Holocene evolution and the Holocene lake level maximum of the Aral Sea 总被引:1,自引:0,他引:1
During the Holocene the Aral Sea underwent various transgressive and regressive phases of different magnitudes. However, previous work has not yet fully clarified the evolution and chronology of the individual phases. Research presented here throws light on the evolution of the Aral Sea during the past 2000 years. It includes field surveys, tachymetric and DGPS-derived altitude measurements, analysis of sediments from two areas of the northern and southern Aral Basin (Tastubek Bay and Karaumbet Bay), and their correlation with GIS-based lake area models. Geomorphological and sedimentological evidence from the study areas shows a transgression of the Aral Sea around 200 AD, ending at a lake level maximum of 54 to 55 m. After a medieval regression, the lake reached this level again between the late 16th and early 19th century AD. The digital elevation model SRTM-3 was used to estimate a lake size of 72,400 km2 for the lake level maximum.Elevated palaeoshorelines, specifically at 72–73 m, are completely absent in the study areas. Local remains of escarpments at elevations of 66 m and 73 m are due to resistant Miocene caprock and are therefore not interpretable as shoreline features. 相似文献
339.
Catastrophic detachment and high-velocity long-runout flow of Kolka Glacier, Caucasus Mountains, Russia in 2002 总被引:1,自引:0,他引:1
Stephen G. Evans Olga V. Tutubalina Valery N. Drobyshev Sergey S. Chernomorets Scott McDougall Dmitry A. Petrakov Oldrich Hungr 《Geomorphology》2009,105(3-4):314-321
In September 2002, a catastrophic geomorphic event occurred in the Caucasus Mountains, southern Russia, in which almost the entire mass of Kolka Glacier detached from its bed, accelerated to a very high velocity (max. 65–80 m/s), and traveled a total distance of 19 km downstream as a glacier-debris flow. Based on the interpretation of satellite imagery obtained only 8.5 h before the event occurred, the analysis of seismograms from nearby seismic stations, and subsequent detailed field observations and measurements, we suggest that this remarkable event was not a response to impulse loading from a rock avalanche in the mountainside above the glacier, or to glacier surging, but due entirely to the static and delayed catastrophic response of the Kolka glacier to ice and debris loading over a period of months prior to the September 20 detachment. We reconstruct the glacier-debris flow using field observations in conjunction with the interpretation of seismographs from nearby seismic stations and successfully simulate the behaviour (runout, velocity, and deposition) of the post-detachment glacier-debris flow using a three-dimensional analytical model. Our demonstration of a standing-start hypothesis in the 2002 Kolka Glacier detachment has substantial implications for glacier hazard assessment and risk management strategies in valleys downstream from unstable debris-covered glaciers in the mountain regions of the world. 相似文献
340.