全文获取类型
收费全文 | 769篇 |
免费 | 37篇 |
国内免费 | 2篇 |
专业分类
测绘学 | 39篇 |
大气科学 | 63篇 |
地球物理 | 191篇 |
地质学 | 289篇 |
海洋学 | 38篇 |
天文学 | 133篇 |
综合类 | 2篇 |
自然地理 | 53篇 |
出版年
2023年 | 4篇 |
2022年 | 7篇 |
2021年 | 17篇 |
2020年 | 11篇 |
2019年 | 18篇 |
2018年 | 27篇 |
2017年 | 27篇 |
2016年 | 27篇 |
2015年 | 31篇 |
2014年 | 33篇 |
2013年 | 41篇 |
2012年 | 26篇 |
2011年 | 39篇 |
2010年 | 29篇 |
2009年 | 38篇 |
2008年 | 35篇 |
2007年 | 34篇 |
2006年 | 36篇 |
2005年 | 21篇 |
2004年 | 25篇 |
2003年 | 15篇 |
2002年 | 24篇 |
2001年 | 18篇 |
2000年 | 7篇 |
1999年 | 10篇 |
1998年 | 13篇 |
1997年 | 11篇 |
1996年 | 8篇 |
1995年 | 6篇 |
1994年 | 7篇 |
1989年 | 5篇 |
1986年 | 4篇 |
1984年 | 8篇 |
1982年 | 4篇 |
1981年 | 9篇 |
1980年 | 7篇 |
1979年 | 4篇 |
1978年 | 9篇 |
1976年 | 6篇 |
1975年 | 5篇 |
1974年 | 4篇 |
1971年 | 4篇 |
1967年 | 4篇 |
1966年 | 4篇 |
1965年 | 5篇 |
1964年 | 4篇 |
1957年 | 4篇 |
1948年 | 3篇 |
1926年 | 3篇 |
1914年 | 3篇 |
排序方式: 共有808条查询结果,搜索用时 20 毫秒
81.
Soil moisture influences many hydrologic applications including agriculture, land management and flood prediction. Most remote‐sensing methods that estimate soil moisture produce coarse resolution patterns, so methods are required to downscale such patterns to the resolutions required by these applications (e.g. 10‐ to 30‐m grid cells). At such resolutions, topography is known to affect soil moisture patterns. Although methods have been proposed to downscale soil moisture based on topography, they usually require the availability of past high‐resolution soil moisture patterns from the application region. The objective of this article is to determine whether a single topographic‐based downscaling method can be used at multiple locations without relying on detailed local observations. The evaluated downscaling method is developed on the basis of empirical orthogonal function (EOF) analysis of space–time soil moisture data at a reference catchment. The most important EOFs are then estimated from topographic attributes, and the associated expansion coefficients are estimated on the basis of the spatial‐average soil moisture. To test the portability of this EOF‐based method, it is developed separately using four data sets (Tarrawarra, Tarrawarra 2, Cache la Poudre and Satellite Station), and the relationships that are derived from these data sets to estimate the EOFs and expansion coefficients are compared. In addition, each of these downscaling methods is applied not only for the catchment where it was developed but also to the other three catchments. The results suggest that the EOF downscaling method performs well for the location where it is developed, but its performance degrades when applied to other catchments. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
82.
Wilhelm Wenz 《International Journal of Earth Sciences》1914,5(5-6):321-346
Ohne Zusammenfassung 相似文献
83.
Crustal extension in the overriding plate at the Aegean subduction zone, related to the rollback of the subducting African slab in the Miocene, resulted in a detachment fault separating high‐pressure/low‐temperature (HP‐LT) metamorphic lower from non‐metamorphic upper tectonic units on Crete. In western Crete, detachment faulting at deeper crustal levels was accompanied by structural disintegration of the hangingwall leading to the formation of half‐graben‐type sedimentary basins filled by alluvial fan and fan‐delta deposits. The coarse‐grained clastic sediments in these half‐grabens are exclusively derived from the non‐metamorphic units atop the detachment fault. Being in direct tectonic contact with HP‐LT metamorphic rocks of the lower tectonic units today, the basins must have formed in the period between c. 20 and 15 Ma, prior to the exposure of the HP‐LT metamorphic rocks at the surface, and juxtaposed with the latter during ongoing deformation. 相似文献
84.
Measuring and forecasting recruitment are central to the understanding and management of fish stocks. Kainge et al. (2013) studied the effect of spawning stock size and environmental fluctuations on the recruitment levels of the Cape hake Merluccius capensis in Namibia. However, their study contains some flaws that undermine the conclusion that Cape hake recruitment is under the influence of upwelling in summer. Until those flaws are properly addressed, this conclusion, in our view, should be treated with caution. 相似文献
85.
A fully automated optimization process is provided for the design of ducted propellers under open water conditions, including 3D geometry modeling, meshing, optimization algorithm and CFD analysis techniques. The developed process allows the direct integration of a RANSE solver in the design stage. A practical ducted propeller design case study is carried out for validation. Numerical simulations and open water tests are fulfilled and proved that the optimum ducted propeller improves hydrodynamic performance as predicted. 相似文献
86.
87.
88.
K. Wilhelm 《Astronomische Nachrichten》2010,331(5):502-511
Quantitative solar spectroscopy must be based on calibrated instrumentation. The basic requirement of a calibration, i.e., a comparison between the instrument under test and a primary laboratory standard through appropriate procedures, will be briefly reviewed, and the application to modern space instruments will be illustrated. Quantitative measurements of spectral radiances with high spectral and spatial resolutions as well as spectral irradiances yield detailed information on temperatures, electron densities, bulk and turbulent motions, element abundances of plasma structures in various regions of the solar atmosphere – from the photosphere to the outer corona and the solar wind. The particular requirements for helioseismology and magnetic‐field observations will not be covered in any depth in this review. Calibration by a laboratory standard is necessary, but not sufficient, because an adequate radiometric stability can only be achieved together with a stringent cleanliness concept that rules out a contamination of the optical system and the detectors as much as possible. In addition, there is a need for calibration monitoring through inter‐calibration and other means (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
89.
Michael W. Busch Steven J. Ostro Jon D. Giorgini Ellen S. Howell Alice A. Hine Irwin I. Shapiro 《Icarus》2007,186(2):581-584
In November 2005, we observed the moons of Mars using the Arecibo 2380-MHz (13-cm) radar, obtaining a result for the OC radar albedo of Phobos (0.056±0.014) consistent with its previously reported radar albedo and implying an upper bound on its near-surface bulk density of . We detected Deimos by radar for the first time, finding its OC radar albedo to be 0.021±0.006, implying an upper bound on its near-surface density of , consistent with a high-porosity regolith. We briefly discuss reasons for these low radar albedos, Deimos' being possibly the lowest of any Solar System body yet observed by radar. 相似文献
90.
Facies analyses of Pleistocene deposits from southern coastal Tanzania (Lindi District) document that sediments formed in a wetland evolving on a coastal terrace in the Lindi Fracture Zone foreland. The exposed succession shows a marked sedimentary change from tidal to terrestrial facies. 14C analyses on gastropod shells indicate the emergence of the Lindi coast at ∼ 44 14C ka BP. Emergence and subsequent elevation of terraces to 21 m above present-day sea level was linked to the falling eustatic sea level prior to the last glacial maximum, and to a periodic elevation due to extensional tectonic episodes in the eastern branch of the East African Rift System (EARS). Since ∼ 44 14C ka BP tectonic uplift at the coast was 80-110 m, comparable to that in the extreme uplift areas of the EARS. 相似文献