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71.
Rémi Valois Christian Camerlynck Amine Dhemaied Roger Guerin Gaghik Hovhannissian Valérie Plagnes Faycal Rejiba Henri Robain 《地球表面变化过程与地形》2011,36(9):1183-1192
In the protection of karstic aquifers, the role played by dolines is of interest as these shallow structures can be preferential infiltration pathways for groundwater recharge. In this study, three depressions in South France (Orniac, Lot) were identified and characterized using combined geophysical methods. Apparent conductivity mapping allows precise definition of dolines corresponding to topographic depressions. It also reveals other dolines that are hidden by soil cover. Electrical resistivity and seismic refraction tomography provide detailed cross‐sections. Even though the dolines studied are close one to another, they exhibit great variability in shape and content. Moreover, time‐lapse data show that the most saturated regions are on the edges of the first doline. Such information helps to evaluate human impacts and forecast potential groundwater contamination. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
72.
I. D. Litovchenko A. V. Alakoz I. E. Val’tts G. M. Larionov 《Astronomy Reports》2011,55(12):1086-1095
Observations of various types of objects in the northern sky were obtained at 44 GHz in the 70-61
A
+ methanol line on the 20-m Onsala radio telescope (Sweden), in order to search for Class I methanol maser emission in the
interstellar medium: regions of formation of high-mass stars, dust rings around HII regions, and protostellar candidates associated
with powerful molecular outflows and Galactic HII regions. Seven new Class Imethanolmasers have been discovered toward regions
of formation of highmass stars, and the existence of two previously observed masers confirmed. The following conclusions are
drawn: (1) neither the association of a bipolar outflow manifest in the wings of CO lines with a highmass protostellar object
(HMPO) nor the presence of thermal emission in lines of complex molecules are sufficient conditions for the detection of Class
I methanol emission; no association with HMPOs radiating at 44 GHz was found for EGOs (a new class of object tracing bipolar
outflows); (2) the existence of H2O masers and Class II methanol masers in the region of aHMPOenhances the probability of detecting Class I methanol emission
toward the HMPO; Class II methanol masers with stronger line fluxes are associated with Class I methanol masers. 相似文献
73.
We present images of the star-forming regionG23.01–0.41 at 6.7GHz in the Class II methanol maser transition 51–60
A
+, produced from archival observations on the European VLBI Network. Our map of the source and its maser spots contains 24
maser components. The data for each spot—absolute coordinates, coordinates relative to the calibration feature, peak flux
and flux integrated over the spot, size, position angle, velocity along the line of sight, and line full width at half-maximum—are
collected in tabular form. The spatial region occupied by the maser spots is approximated by a 200×130 milliarcsec ellipse
in position angle PA = −0.40°, centered on the absolute coordinates α
0 = 18h34m40.282s, δ
0 = −09°00′38.27″ (J2000). If the source is a protoplanetary disk, then, for the distance estimate derived from trigonometric
parallax, its diameter is 1800 AU, and the mass of the central protostar is 23.5M
⊙. 相似文献
74.
Tidal dissipation is the main driver of orbital evolution of natural satellites and a key point to understand the exoplanetary system configurations. Despite its importance, its quantification from observations still remains difficult for most objects of our own Solar System. In this work, we overview the method that has been used to determine, directly from observations, the tidal parameters, with emphasis on the Love number \(k_2\) and the tidal quality factor Q. Up-to-date values of these tidal parameters are summarized. Last, an assessment on the possible determination of the tidal ratio \(k_2/Q\) of Uranus and Neptune is done. This may be particularly relevant for coming astrometric campaigns and future space missions focused on these systems. 相似文献
75.
Amaral Genilda Canuto Pezzopane José Eduardo Macedo de Souza Nóia Júnior Rogério Martínez Manuel Fernández Fonseca Mariana Duarte Silva Gibson Elbya Leão Toledo João Vitor Pezzopane José Ricardo Macedo Klippel Valéria Hollunder Xavier Talita Miranda Teixeira 《Theoretical and Applied Climatology》2022,147(1-2):347-361
Theoretical and Applied Climatology - The climate change endangers many species of the Amazon Forest. An example, in the endangered medicinal species Pilocarpus microphyllus (popularly known as... 相似文献
76.
Huu Hieu Ho Rudy Swennen Val��rie Cappuyns Elvira Vassilieva Tom Van Gerven Tan Van Tran 《Aquatic Geochemistry》2013,19(1):57-75
The speciation and mobility of some selected trace metals (As, Cu, Mn, Pb and Zn) in sediments with depth was investigated in the Cam River-mouth (Vietnam) by collecting sediment cores and analysing porewater and sediment composition, complemented with single (ammonium-EDTA) and sequential (BCR 3-step) extractions and mineralogical analysis (XRD). All trace metals show overall decreasing trends with depth in porewater as a result of anthropogenic input in upper sediment layers. High porewater concentrations of As, Mn and Pb in oxic and suboxic sediment layers may result in groundwater pollution. Sediment-bound Pb and Mn dominate in the reducible and the acid-soluble fraction, respectively, while Cu and Zn distribute rather evenly between four extracted fractions. The porewater metal speciation, as predicted by a geochemical model Visual MINTEQ version 3.0, indicates that the toxicity of Cu, Mn, Pb and Zn (presented by the proportions of free metal ions) decreases with depth, while the toxicity of As increases when As(III) becomes more abundant. The dissolved concentrations of trace metals are not only controlled by the precipitation/dissolution of discrete hydroxide/oxide, carbonate and phosphate minerals, but also by sorption processes on major sorbents (i.e. As on goethite, and Mn and Zn on calcite and dolomite). Sulphide minerals do not show any control even in the anoxic zone most likely because of the low concentration of sulphur. 相似文献
77.
Nick Marriner Jean-Philippe Goiran Bernard Geyer Valérie Matoïan Michel al-Maqdissi Marion Leconte Pierre Carbonel 《Quaternary Research》2012,78(1):35-49
Ras Ibn Hani peninsula, a wave-dominated tombolo (800 × 1000 m) on the Syrian coast, provides evidence for significant Holocene changes that can be linked to geological inheritance, rising post-glacial sea level, sediment supply and human impacts. Initial development of Ras Ibn Hani's coastal system began ~ 8000 years ago when shallow marine environments formed in a context of rising post-glacial sea level. Following relative sea-level stabilization ~ 6000 cal yr BP, beach facies trace the gradual formation of a wave-dominated sandbank fronted by a ~ 2300 × ~ 500 m palaeo-island whose environmental potentiality was attractive to Bronze Age societies. A particularly rapid phase of tombolo accretion is observed after ~ 3500 cal yr BP characterised by a two- to fourfold increase in sedimentation rates. This is consistent with (i) a pulse in sediment supply probably driven by Bronze Age/Iron Age soil erosion in local catchments, and (ii) positive feedback mechanisms linked to regionally attested neotectonics. Archaeological remains and radiocarbon datings confirm that the subaerial tombolo was probably in place by the Late Bronze Age. These data fit tightly with other eastern Mediterranean tombolo systems suggesting that there is a great deal of predictability to their geology and stratigraphy at the regional scale. 相似文献
78.
Sandra Barbouteau Patrick Rasolofosaon Noalwenn Dubos‐Sallée Virginie Vassil Valérie Poitrineau Jean‐François Nauroy 《Geophysical Prospecting》2016,64(5):1368-1385
This article introduces an alternative experimental procedure for measuring the elastic properties of a solid material at laboratory scale, using both the principles of passive seismic interferometry and resonance ultrasound spectroscopy. We generate noise into the studied sample with a pneumatic air blow gun, and we cross‐correlate the signals recorded with two passive piezoelectric sensors put in soft contact with the sample surface. Resonance phenomena are induced in the sample, but in contrast with conventional resonance ultrasound spectroscopy experiments, we have no control over the injected frequencies that are sent all together within the noise spectrum. The spectrum of the correlogram is a good approximation of the resonance spectrum of the vibrating sample and can be inverted in terms of the elastic moduli of the constituent material of the sample. The experimental procedure is validated on samples made of standard materials (here, aluminium and Plexiglas) by consistently comparing the inverted elastic velocities with the velocities independently measured with the conventional technique of ultrasonic pulse transmission. Moreover, we got similar positive results on dry rock samples, such as Vilhonneur limestone. These encouraging preliminary results open up promising prospects for monitoring fluid substitution in rock samples using the technique described in this paper. 相似文献
79.
Shell use by sympatric hermit crab species in a seasonally open coastal lagoon in Northeastern Brazil 下载免费PDF全文
Valéria F. Vale Sávio A. S. N. Moraes Vanessa L. G. Brito Carlos E. R. D. Alencar Fúlvio A. M. Freire 《Marine Ecology》2017,38(5)
There are gaps in what is known about the patterns of gastropod shell use by hermit crabs in Brazilian lagoon areas, especially in Northeastern Brazil. However, this is important because the understanding of selection patterns provides information on life history and eco‐evolutionary conceptions of paguroids. The present study investigated the use of gastropod shells occupied by Pagurus criniticornis and Clibanarius sclopetarius in a coastal lagoon seasonally connected to an estuary and to the sea, correlating eco‐evolutionary aspects and hydrodynamic characters. The study was carried out between February 2013 and January 2014. Hermit crabs and their shells were identified and measured (hermit crabs’ cephalothorax shield length and width, major propodus length and height, weight, shell total length and width, shell aperture length and width). Partial least squares regression was used to analyse the morphometric data. Additionally, a multinomial proportions test was performed to infer patterns (inter‐/intra‐specific) of shells’ occupation. Hermit crab species occupied a total of 13 types of shells, predominantly those of Neritina virginea (67.83%). The shell weight was the most important determinant of shell occupancy in the morphometric model (variable importance in projection >1). The proportions of N. virginea shells used were similar in both species of hermit crabs, except between the sexes of P. criniticornis. Presumably, the high utilization rate of N. virginea shells is related to its abundance and dispersal, and to the shells’ suitability for hermit crabs, which is reflected by the morphometric model, as well as by the hydrodynamics of the lagoon‐estuarine environment. The relative occupation of different types of shells for each species of hermit crabs studied appears to be associated with regulation by inter‐/intra‐specific competition, which fosters the co‐occurrence of those populations. These results endorse coastal lagoons as a refuge and recruitment area for aquatic fauna. In addition, it highlights a challenge in the management and conservation of paguroid species whose population dynamics depend on the resources coming from the Gastropoda community. 相似文献
80.