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991.
Here we report the first observations of loggerhead turtles Caretta caretta preying on a conspicuous molluscan invader, the rapa whelk Rapana venosa. An average number of 136 opercula were found in stomach contents of five turtles, the curved carapace length ranging in from 51 to 112 cm. No other alimentary items were found in the turtles analyzed. We suggest that the rapa whelk may constitute up to 100% of the diet for immature and mature loggerheads in the Río de la Plata estuary (Uruguay), highlighting the plastic nature of the foraging behavior of loggerheads. 相似文献
992.
Joel E. Saylor Brian K. Horton Junsheng Nie Jaime Corredor Andrés Mora 《Basin Research》2011,23(4):377-402
This paper addresses foreland basin fragmentation through integrated detrital zircon U–Pb geochronology, sandstone petrography, facies analysis and palaeocurrent measurements from a Mesozoic–Cenozoic clastic succession preserved in the northern Andean retroarc fold‐thrust belt. Situated along the axis of the Eastern Cordillera of Colombia, the Floresta basin first received sediment from the eastern craton (Guyana shield) in the Cretaceous–early Palaeocene and then from the western magmatic arc (Central Cordillera) starting in the mid‐Palaeocene. The upper‐crustal magmatic arc was replaced by a metamorphic basement source in the middle Eocene. This, in turn, was replaced by an upper‐crustal fold‐thrust belt source in the late Eocene which persisted until Oligocene truncation of the Cenozoic section by the eastward advancing thrust front. Sedimentary facies analysis indicates minimal changes in depositional environments from shallow marine to low‐gradient fluvial and estuarine deposits. These same environments are recorded in coeval strata across the Eastern Cordillera. Throughout the Palaeogene, palaeocurrent and sediment provenance data point to a uniform western or southwestern sediment source. These data show that the Floresta basin existed as part of a laterally extensive, unbroken foreland basin connected with the proximal western (Magdalena Valley) basin from mid‐Paleocene to late Eocene time when it was isolated by uplift of the western flank of the Eastern Cordillera. The Floresta basin was also connected with the distal eastern (Llanos) basin from the Cretaceous until its late Oligocene truncation by the advancing thrust front. 相似文献
993.
994.
Theresa Blume Erwin Zehe Dominik E. Reusser Andrés Iroumé Axel Bronstert 《水文研究》2008,22(18):3661-3675
Catchment scale hydrological process studies in southern Chile are of special interest as little research at this scale has been carried out in this region. In particular, the young volcanic ash soils, which are typical for this area, are not well understood in their hydrological behaviour. In addition, extensive land use changes require detailed knowledge of hydrological processes in disturbed as well as undisturbed catchments in order to estimate resulting risks of erosion, eutrophication, floods and droughts. This study focuses on data collection and experimental determination of relevant processes in an undisturbed forested catchment in the Andes of southern Chile. The here gained understanding of runoff generation can serve as a reference for comparison with sites subject to human intervention, improving estimation of the effects of land use change. Owing to the lack of long‐term data for this catchment it was necessary to replace long time series by a multitude of experimental methods covering as many aspects of the runoff generation process as possible. The methods used in this investigation include: measurements of streamflow, rainfall, throughfall, water chemistry, soil water dynamics, groundwater dynamics, soil physics, soil mineralogy, geo‐electrical sounding, and tracer techniques. Methods and equipment used during field campaigns are described and evaluated for usefulness versus expenditure (labour and financial costs). Selected results and the hypotheses developed from these findings are presented. The results suggest the importance of fast processes for rainfall runoff response on the one hand as well as considerable dampening effects of a large subsurface storage on the other hand. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
995.
Pedro J. Amado Susana Martín-Ruíz Juan Carlos Suárez Armando Arellano Ferro Andrés Moya Ignasi Ribas Ennio Poretti 《Astrophysics and Space Science》2006,304(1-4):173-175
Photometric and spectroscopic results for the star HD 172189, member of the open cluster IC 4756 in the summer field of the space mission COROT, are presented. From photometric observations in the Strömgren system carried out at various epochs, its binary nature as well as the presence of a δ Scuti-type pulsating component have been discovered. The frequency analysis of the whole dataset confirms a dominant frequency of 19.5974 c d?1 with a maximum amplitude near 0.02 mag plus other frequencies in the range 18–20 c d?1. A preliminary orbital solution from the light curve and from four FEROS spectra reveals two similar components of around 1.5 M ⊙ orbiting with a period of 5.702 d. 相似文献
996.
997.
998.
Julio Iglesias de Ussel Antonio Trinidad Diego RuIz Eduardo Battaner Antonio J. Delgado José M. Rodriguez-Espinosa Eduard Salvador-Solé José M. Torrelles 《Astrophysics and Space Science》1997,257(2):237-248
In this paper the main findings are presented of a recent study made by a team of sociologists from the University of Granada
on the professional astronomers currently working in Spain. Despite the peculiarities of this group – its youth, twentyfold
increase in size over the last 20 years, and extremely high rate of specialization abroad – in comparison with other Spanish
professionals, this is the first time that the sociological characteristics of the group have been studied discretely. The
most significant results of the study are presented in the following sections. Section 1 gives a brief historical background
of the development of Astronomy in Spain. Section 2 analyzes the socio-demographic profile of Spanish Astronomy professionals
(sex, age, marital status, etc.). Sections 3–5 are devoted to the college education and study programs followed by Spanish
astronomers, focusing on the features and evaluations of the training received, and pre- and postdoctoral study trips made
to research centers abroad. The results for the latter clearly show the importance that Spanish astronomers place on having
experience abroad. Special attention is paid to scientific papers published as a result of joint research projects carried
out with colleagues from centers abroad as a result of these study trips. Section 6 describes the situation of Astronomy professionals
within the Spanish job market, the different positions available and the time taken to find a job after graduation. Section
7 examines Astronomy as a discipline in Spain, including the astronomers' own opinions of the social status of the discipline
within Spanish society. Particular attention is paid to how Spanish astronomers view the status of Astronomy in Spain in comparison
with that of other European countries.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
999.
Cold Dust and Very Cold Excess Emission in the Galaxy 总被引:2,自引:0,他引:2
Hervé Bourdin Françcois Boulanger Jean-Philippe Bernard Guilaine Lagache 《Astrophysics and Space Science》2002,281(1-2):243-246
We provide insight in the origin of the far-IR to mm emission from galaxies by presenting a decomposition of the Galaxy emission
where we separate the contributions from dust in the atomic gas and dust associated with quiescent molecular gas as a function
of Galacto-centric distance. This decomposition leaves a puzzling very cold emission excess with a brightness independent of Galactic longitude that might be pointing at interstellar matter in the
outer Galaxy not traced by H I nor CO emission.
This revised version was published online in September 2006 with corrections to the Cover Date. 相似文献
1000.
Gutiérrez Pedro J. Ortiz José L. Rodrigo Rafael López-Moreno José J. Jorda Laurent 《Earth, Moon, and Planets》2002,90(1-4):239-247
A simplified thermal model has been used to calculate thenon-gravitational forces acting on small irregular nuclei in the
orbit ofComet 46P/Wirtanen. The torque of thenon-gravitational force has beencalculated and the Euler equations have been
solved in order toinvestigate the rotational evolution of several irregular nuclei duringa single orbital step. Several initial
spin axis orientations andactivity patterns on their surfaces have been considered. The nucleiconsidered have a mean radius
of 1 km and their inertia moments havebeen calculated assuming a homogeneous bulk density of 500 kg/m3. Inall the simulations, the initial spin period is 6h and the nucleiinitially rotate around their shortest axis. Under these
assumptions,significant changes in the angular momentum and in spin period have beenobtained in all the simulations, but the
nucleus is found to practicallyremain in its spin state of lowest energy during the entire orbitalperiod. 相似文献