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61.
R. K. Das D. P. K. Banerjee N. M. Ashok 《Monthly notices of the Royal Astronomical Society》2009,398(1):375-384
We present near-infrared (1–2.5 μm) spectroscopic and photometric results of Nova V2615 Ophiuchi which was discovered in outburst in 2007 March. Our observations span a period of ∼80 d starting from 2007 March 28 when the nova was at its maximum light. The evolution of the spectra is shown from the initial P Cygni phase to an emission-line phase and finally to a dust formation stage. The characteristics of the JHK spectra are very similar to those observed in a nova outburst occurring on a carbon–oxygen white dwarf. We analyse an observed line at 2.088 μm and suggest that it could be due to Fe ii excited by Lyman α fluorescence. The highlight of the observations is the detection of the first overtone bands of carbon monoxide (CO) in the 2.29–2.40 μm region. The CO bands are modelled to estimate the temperature and mass of the emitting CO gas and also to place limits on the 12 C/13 C ratio. The CO bands are recorded over several epochs, thereby allowing a rare opportunity to study the evolution from a phase of constant strength through a stage when the CO is destroyed fairly rapidly. We compare the observed time-scales involved in the evolution of the CO emission and find a good agreement with model predictions that investigate the chemistry in a nova outflow during the early stages. 相似文献
62.
Simon Portegies Zwart Steve McMillan Stefan Harfst Derek Groen Michiko Fujii Breanndán Ó Nualláin Evert Glebbeek Douglas Heggie James Lombardi Piet Hut Vangelis Angelou Sambaran Banerjee Houria Belkus Tassos Fragos John Fregeau Evghenii Gaburov Rob Izzard Mario Jurić Stephen Justham Andrea Sottoriva Marcel Zemp 《New Astronomy》2009,14(4):369-378
We present MUSE, a software framework for combining existing computational tools for different astrophysical domains into a single multiphysics, multiscale application. MUSE facilitates the coupling of existing codes written in different languages by providing inter-language tools and by specifying an interface between each module and the framework that represents a balance between generality and computational efficiency. This approach allows scientists to use combinations of codes to solve highly coupled problems without the need to write new codes for other domains or significantly alter their existing codes. MUSE currently incorporates the domains of stellar dynamics, stellar evolution and stellar hydrodynamics for studying generalized stellar systems. We have now reached a “Noah’s Ark” milestone, with (at least) two available numerical solvers for each domain. MUSE can treat multiscale and multiphysics systems in which the time- and size-scales are well separated, like simulating the evolution of planetary systems, small stellar associations, dense stellar clusters, galaxies and galactic nuclei. In this paper we describe three examples calculated using MUSE: the merger of two galaxies, the merger of two evolving stars, and a hybrid N-body simulation. In addition, we demonstrate an implementation of MUSE on a distributed computer which may also include special-purpose hardware, such as GRAPEs or GPUs, to accelerate computations. The current MUSE code base is publicly available as open source at http://muse.li. 相似文献
63.
Shovan Lal Chattoraj Santanu Banerjee P. K. Saraswati 《Journal of the Geological Society of India》2009,73(4):567-574
Glauconitic minerals are considered as one of the valuable input parameters in sequence stratigraphic analysis of a basin.
In the present study glauconitic minerals are reported from subtidal green shale facies in the lower part of the Late Paleocene-Early
Eocene Naredi Formation of western Kutch. On the basis of the foraminiferal assemblage the glauconite bearing beds are interpreted
to have formed in a mid shelf depositional settings of an unstable marine conditions. XRD studies confirm the glauconite mineralogy
of the green pellets and provide an estimation of glauconite maturity. Textural attributes of the glauconites confirm their
derivation by different degrees of alteration of precursor feldspar grains. Because of the authigenic origin and autochthonous
nature, these glauconites hold promise for understanding sequence stratigraphy of the Palaeogene succession of the western
Kutch. 相似文献
64.
The paper consists of some exact solutions for a homogeneous Bianchi type VI0 universe. The material distribution is taken to be a magnetized bulk viscous fluid in presence of massive cosmological string. We assume that current is flowing along x-direction. Therefore, the magnetic field is in yz-plane. For deterministic model of the universe, we assume that shear (σ) is proportional to the expansion (θ) and ζ θ=constant=ξ where ζ the coefficient of bulk viscosity and θ the expansion in the model. The physical and kinematical parameters of the models thus formed are discussed. 相似文献
65.
Peter Brugger Tirtha Banerjee Frederik De Roo Konstantin Kröniger Rafat Qubaja Shani Rohatyn Eyal Rotenberg Feodor Tatarinov Dan Yakir Fulin Yang Matthias Mauder 《Boundary-Layer Meteorology》2018,169(2):233-250
We investigate the effects of an isolated meso-\(\gamma \)-scale surface heterogeneity for roughness and albedo on the atmospheric boundary-layer (ABL) height, with a case study at a semi-arid forest surrounded by sparse shrubland (forest area: \(28~\text{ km }^2\), forest length in the main wind direction: 7 km). Doppler lidar and ceilometer measurements at this semi-arid forest show an increase in the ABL height over the forest compared with the shrubland on four out of eight days. The differences in the ABL height between shrubland and forest are explained for all days with a model that assumes a linear growth of the internal boundary layer of the forest through the convective ABL upwind of the forest followed by a square-root growth into the stable free atmosphere. For the environmental conditions that existed during our measurements, the increase in ABL height due to large sensible heat fluxes from the forest (\(600~\text {W~m}^{-2}\) in summer) is subdued by stable stratification in the free atmosphere above the ABL, or reduced by high wind speeds in the mixed layer. 相似文献
66.
A number of archeological features, including in‐filled irrigation canals of uncertain prehistoric age, occur within the Holocene floodplain of the Salt River at Phoenix, Arizona. In the first attempt to date irrigation‐canal sediments using luminescence methods, we obtained age estimates of 1640 ± 190 yr B.P. (1σ) (multi‐aliquot or MA) and 1621 ± 95 yr B.P. (post‐IR single‐aliquot‐regenerative‐dose or SAR) for a single sample from the base of the oldest canal‐infilling deposits (all IR‐PSL ages reported in this article are in calendar years before A.D. 2001). For the remaining canal samples, weighted mean luminescence ages of 819 ± 45 yr (MA) and 826 ± 32 yr (post‐IR SAR) were obtained. Thus from photonic dating we can resolve the first and last phases of canal use at this Phoenix site: initiation at ca. 1600 years ago and final use at ca. 800 years ago. These results demonstrate the power of SAR luminescence sediment dating to enhance our understanding of prehistoric irrigation‐canal development and usage here and elsewhere in the world. © 2004 Wiley Periodicals, Inc. 相似文献
67.
Archaeological investigations into the processes and factors controlling the magnetic enhancement of soils were initiated in the 1960s in conjunction with the application of magnetic prospection surveys. After a highly productive period of research, archaeological interest in soil magnetism experienced a downswing, which has just recently been reversed. Continuing research within the fields of rock magnetism and environmental magnetism has refined our understanding of the processes and products of magnetic enhancement and demonstrated the broad applicability of soil magnetic analyses. Using this information, together with recent archaeological studies, we update archaeologists on the variety of soil magnetic techniques and how they can be utilized to define, detail, and understand archaeological sites, features, and environments. A case study at the Cahokia Mounds Site in southwestern Illinois illustrates how soil magnetic techniques can be interfaced with other methods to understand archaeological landscapes and landscape change. © 1998 John Wiley & Sons, Inc. 相似文献
68.
69.
Forecasting of groundwater level in hard rock region using artificial neural network 总被引:2,自引:0,他引:2
In hardrock terrain where seasonal streams are not perennial source of freshwater, increase in ground water exploitation has
already resulted here in declining ground water levels and deteriorating its’ quality. The aquifer system has shown signs
of depletion and quality contamination. Thus, to secure water for the future, water resource estimation and management has
urgently become the need of the hour. In order to manage groundwater resources, it is vital to have a tool to predict the
aquifer response for a given stress (abstraction and recharge). Artificial neural network (ANN) has surfaced as a proven and
potential methodology to forecast the groundwater levels. In this paper, Feed-Forward Network based ANN model is used as a
method to predict the groundwater levels. The models are trained with the inputs collected from field and then used as prediction
tool for various scenarios of stress on aquifer. Such predictions help in developing better strategies for sustainable development
of groundwater resources. 相似文献
70.
Santanu Banerjee Shovan Lal ChattorajP.K. Saraswati Somnath DasguptaUrbashi Sarkar 《Marine and Petroleum Geology》2012,30(1):144-160
Formation and maturation of glauconites within the early Middle Eocene Harudi Formation, built up in a lagoon to shelf transition in western Kutch, India is addressed taking recourse to a combined sedimentological, micropalaeontological and mineralogical investigation. The glauconite is authigenic and its occurrence coincides with maximum flooding. The glauconite is more matured within the fecal pellets and is less matured within the intra-particle pores of bioclasts namely, foraminifera, ostracoda, gastropoda and bryozoa. SEM-EDS, XRD and geochemical studies clearly document that the infilling within the intra-particle pores of bioclasts belong to nascent to slightly evolved glauconite (<5 wt% K2O), while the pellet belongs to slightly evolved to evolved glauconite (5-7 wt% K2O). Based on chemical characteristics and SEM investigations the glauconitization process can be best explained by the ‘verdissement theory’. The glauconite possibly formed as initial authigenic glauconitic smectite precipitates; while the pellet matured subsequently by addition of K, the process was hindered in case of infillings. The maturation process also involved addition of Si and release of Al, with or without release of Mg. The glauconite maturation was facilitated in case of fecal pellets because of higher porosity, inter-granular nature of pores and availability of necessary elements in semi-confined micro-environments. In contrast, the maturation was aborted at an early stage in case of infillings because of the minute, closed nature of the pores and prevalent alkaline conditions not allowing dissolution of calcitic tests. A low negative cerium anomaly suggests glauconite formation in sub-oxic micro-environments, created by decay of organic matters within the fecal pellets and bioclasts. A clear case of substratum control on glauconitization becomes apparent. 相似文献