全文获取类型
收费全文 | 259篇 |
免费 | 10篇 |
国内免费 | 16篇 |
专业分类
测绘学 | 2篇 |
大气科学 | 26篇 |
地球物理 | 72篇 |
地质学 | 106篇 |
海洋学 | 30篇 |
天文学 | 33篇 |
综合类 | 3篇 |
自然地理 | 13篇 |
出版年
2021年 | 4篇 |
2020年 | 1篇 |
2019年 | 2篇 |
2018年 | 9篇 |
2017年 | 5篇 |
2016年 | 10篇 |
2015年 | 9篇 |
2014年 | 6篇 |
2013年 | 11篇 |
2012年 | 7篇 |
2011年 | 27篇 |
2010年 | 17篇 |
2009年 | 19篇 |
2008年 | 17篇 |
2007年 | 18篇 |
2006年 | 10篇 |
2005年 | 10篇 |
2004年 | 12篇 |
2003年 | 8篇 |
2002年 | 8篇 |
2001年 | 5篇 |
2000年 | 8篇 |
1999年 | 2篇 |
1998年 | 3篇 |
1997年 | 6篇 |
1996年 | 3篇 |
1995年 | 1篇 |
1994年 | 3篇 |
1993年 | 3篇 |
1992年 | 1篇 |
1991年 | 3篇 |
1990年 | 2篇 |
1987年 | 1篇 |
1986年 | 2篇 |
1985年 | 1篇 |
1984年 | 3篇 |
1983年 | 4篇 |
1982年 | 3篇 |
1981年 | 2篇 |
1980年 | 3篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1977年 | 1篇 |
1976年 | 2篇 |
1975年 | 1篇 |
1974年 | 2篇 |
1971年 | 1篇 |
1970年 | 1篇 |
1969年 | 1篇 |
1964年 | 1篇 |
排序方式: 共有285条查询结果,搜索用时 15 毫秒
231.
Roberto de Franco 《Geophysical Prospecting》2001,49(4):395-404
A method to estimate interval velocities and thickness in a horizontal isotropic layered medium from wide-angle reflection traveltime curves is presented. The method is based on a relationship between the squared reflection traveltime differences and the squared offset differences relative to two adjacent reflectors. The envelope of the squared-time versus offset-difference curves, for rays with the same ray parameter, is a straight line, whose slope is the inverse of the square of the interval velocity and whose intercept is the square of the interval time. The method yields velocity and thickness estimates without any knowledge of the overlying stratification. It can be applied to wide-angle reflection data when either information on the upper crust and/or refraction control on the velocity is not available. Application to synthetic and real data shows that the method, used together with other methods, allows us to define a reliable 1D starting model for estimating a depth profile using either ray tracing or another technique. 相似文献
232.
A computationally efficient method for delineating irregularly shaped spatial clusters 总被引:1,自引:0,他引:1
Juan C. Duque Jared Aldstadt Ermilson Velasquez Jose L. Franco Alejandro Betancourt 《Journal of Geographical Systems》2011,13(4):355-372
In this paper, we present an efficiency improvement for the algorithm called AMOEBA, A Multidirectional Optimum Ecotope-Based Algorithm, devised by Aldstadt and Getis (Geogr Anal 38(4):327?C343, 2006). AMOEBA embeds a local spatial autocorrelation statistic in an iterative procedure in order to identify spatial clusters (ecotopes) of related spatial units. We provide an analysis of the computational complexity of the original AMOEBA and develop an alternative formulation that reduces computational time without losing optimality. Empirical evidence is provided using georeferenced socio-demographic data in Accra, Ghana. 相似文献
233.
Astronomy Letters - The high-resolution Jet Propulsion Laboratory DE431 and DE432 planetary ephemeris are used to evaluate the instantaneous eccentricity functions of the orbits of the planets of... 相似文献
234.
This paper describes a major programme of small-scale physical model tests to establish better the influence of armour type and configuration on overtopping. Specifically, 179 tests determined the relative difference in overtopping behaviour for 13 types/configurations of armour. Roughness factors γf were determined for rock (two layers), cubes (single layer and two layers), Tetrapod, Antifer, Haro, Accropode, Core-Loc™ and Xbloc™. These roughness influence factors have been included in the CLASH database and are for use in the neural network prediction of overtopping. Individual wave-by-wave overtopping volumes were analysed and found to compare well with current prediction methods. Measured reflection coefficients for the different units are also presented and compared with recent formulae. 相似文献
235.
236.
R. de Franco F. Berra G. Biella G. Boniolo G. Caielli A. Corsi F. Forcella F. Lazzati A. Lozej A. Morrone R. Tondi 《第四纪科学杂志》2004,19(4):409-421
In the Clusone Basin (a large intermontane basin filled by thick late Neogene–Quaternary sediments in the Middle Val Seriana, Southern Alps), two high‐resolution seismic profiles have been acquired in order to reconstruct the geometries of the sediments that fill the depression, with a maximum thickness of more than 200 m as documented by available well data, and to define their relationships with the bedrock, consisting of Late Triassic carbonates. In addition to standard seismic reflection processing, a seismic refraction inversion technique has been applied. The integration of geological (both surface and well data) and seismic data indicates a complex history of the drainage patterns of the Clusone Basin, documenting a shift of the Serio River from a palaeodrainage toward the southeast (Val Borlezza) to the present situation, toward the south (Val Seriana): between the older and the present‐day drainages an important depositional stage occurred, as documented by the thick sediments that fill the Clusone Basin, controlling the capture of the Serio River along the Val Seriana. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
237.
238.
Roberto Battiston Maria Teresa Brunetti Franco Cervelli Cristiano Fidani Mauro Menichelli 《Astrophysics and Space Science》2009,323(4):357-366
We discuss an electromagnetic sampling calorimeter for the detection of very high energy gamma-rays on the Moon, which is
based on the use of scintillating cylinders and plates imbedded in the lunar soil. The use of lunar soil as a calorimeter
radiator reduces the weight of the material to be transported to the Moon and minimises environmental impact. Plastic scintillator
bars inserted into the regolith about 1.5 m are the active elements of this instrument: at the surface, each bar is terminated
by a plastic scintillator plate to veto high energy charge particles. The readout system for the scintillator bars and plates
are based on recently developed single photon solid state detectors (Silicon Photomultiplier, SiPM), extremely compact, sturdy
and sensitive devices suited for detecting small light pulses in a space experiment. The performance of a regolith-scintillator
calorimeter is evaluated and the relevant parameters are optimised using a GEANT4 simulation. 相似文献
239.
Claudia Terzi Franco Ricci Lucchi Gian Battista Vai Paul Aharon 《Geo-Marine Letters》1994,14(2-3):177-184
Over 20 occurrences of discontinuous limestone blocks, locally called calcari aLucina, were mapped in the Tuscan—Romagna region of the northern Italian Apennines. The limestones, consisting of a variable mixture of authigenic carbonates (calcite, dolomite, and aragonite), sulfides (primarily pyrite), and allogenic silicates, occur in association with turbidite and hemipelagite units that were deposited in foredeep basins during early to late Miocene times. The limestone blocks are interpreted to represent relicts of carbonate buildups formed around methane-rich fluid vents on the basis of their (1) striking petrographic similarities to carbonates from cold vents in the modern oceans; (2) unique chemosynthetic-like fauna, and (3) anomalously negative
13C values (
13C = – 16 to – 58 PDB). The contemporaneous tectonism of the Apennine orogeny is likely to be the primary cause for the expulsion of the methane-rich fluids to the seabed in a manner analogous to the fluid-flow processes occurring at modern accretionary prisms. 相似文献
240.
Metazoan/microbial biostalactites from present‐day submarine caves in the Mediterranean Sea 下载免费PDF全文
Rossana Sanfilippo Antonietta Rosso Adriano Guido Adelaide Mastandrea Franco Russo Robert Riding Emma Taddei Ruggiero 《Marine Ecology》2015,36(4):1277-1293
Biostalactites formed by metazoan–microbialite associations from three submerged marine caves in the Plemmirio Peninsula (south of Syracuse, Ionian Sea) are randomly distributed and show different sizes and morphologies, as well as variations in surface roughness/smoothness. The biostalactites consist of crusts a few centimeters thick of small serpulids and other metazoans, associated with fine‐grained carbonate; the larger ones often include a nucleus of serpulid tubes (Protula). The metazoans include mainly serpuloideans, sponges, bryozoans and foraminifers but microbial carbonates are also significant components. The composition of both the living communities and thanatocoenoses on the outer surfaces, as well as the composition and fabric of the internal framework, were analysed and used to reconstruct the history of the caves. All of the identified sessile faunas mainly consist of cryptic and sciaphilic dwellers that reflect cave conditions and their variations through time. The distribution pattern, composition and abundance of the present‐day dwellers largely depend on the degree of roughness of the biostalactite surfaces and their positions within the caves. It has been suggested that the Protula specimens in the nuclei represent pioneer populations that formed aggregates during the early cave colonization phase, in response to relatively high food supply from seawater inflow and intruding continental waters. By contrast, the outer metazoan–microbialite carbonates reflect more confined conditions in the caves caused by Holocene sea‐level rises. Hypotheses are proposed for biostalactite growth, taking into account information about the growth rates of some constituents, and evidence of dissolution effects. Similarities and differences between these biostalactites and other Holocene deposits previously described from submarine caves in the Mediterranean Sea and in tropical reefs are discussed. 相似文献