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101.
Paleothermometry is an essential tool for understanding past changes in climate. The ‘carbonate clumped isotope thermometer’ is a temperature proxy related to ordering of 13C and 18O in the carbonate lattice (based on measurements of 13C18O16O in CO2 produced by acid digestion of carbonate). This thermometer has been previously calibrated for inorganic calcite and aragonitic corals [Ghosh P., Adkins J., Affek H., Balta B., Guo W. F., Schauble E. A., Schrag D., and Eiler J. M. (2006) C-13-O-18 bonds in carbonate minerals: a new kind of paleothermometer. Geochim. Cosmochim. Acta70 (6), 1439-1456]. Here we determine the relationship between growth temperatures of aragonitic fish otoliths and abundances of 13C18O16O produced by acid digestion of those otoliths. Our calibration is based on analyses of otoliths from six species from four genera of modern fish sampled from a latitudinal transect of the Atlantic Ocean between 54° S and 65° N, plus one species from the tropical western Pacific. The temperatures at which fish otoliths precipitated were estimated by the mean temperature in the waters in which they lived, averaged over their estimated lifetimes. Estimated growth temperatures of our samples vary between 2 and 25 °C. Our results show that the abundance of 13C18O16O in CO2 produced by acid digestion of fish otolith aragonite is a function of growth temperature, following the relationship: , where Δ47 is the enrichment, in per mil, of 13C18O16O in CO2 relative to the amount expected for a stochastic (random) distribution of isotopes among all CO2 isotopologues, and T is the temperature in Kelvin. This relationship closely approaches that previously documented for inorganic calcite and aragonitic coral (Ghosh et al., 2006). 相似文献
102.
Sarbari Ghosh Utpal Kumar De Atmospheric Science Research Department of Physics Jadavpur University Calcutta India Received April revised July 《大气科学进展》1997,(1)
AComparativeStudyoftheAtmosphericLayersbelowFirstLiftingCondensationLevelforInstantaneousPre-MonsoonThunderstormOcurenceatAga... 相似文献
103.
We point out that several independent considerations rule out the hypothesis that the missing mass in galactic halos is dominated by massive neutral fermions such as neutrinos, gravitinos or photinos. 相似文献
104.
Cosmic-ray propagation in the vicinity of 1 kpc from the Sun is considered. The data on the 1012–1015 eV particle anisotropy, on 1012 eV electron spectrum, and on temporal cosmic-ray variations are analyzed. The diffusion coefficientD(1012–1013 eV)=1029–1030 cm2s–1 inferred from the analysis coincides with its standard value in the large-halo model withh=15 kpc. The total power of cosmic-ray generation, about 3×1049 erg per SN in the proton component and about 1048 erg per SN in the electron component, typical of the galactic diffusion model is in agreement with the obtained parameters of local sources. 相似文献
105.
Dynamic Response of Machine Foundation on Layered Soil: Cone Model Versus Experiments 总被引:1,自引:0,他引:1
P. K. Pradhan A. Mandal D. K. Baidya D. P. Ghosh 《Geotechnical and Geological Engineering》2008,26(4):453-468
This paper presents the experimental validation of analytical solution based on cone model for machine foundation vibration
analysis on layered soil. Impedance functions for a rigid massless circular foundation resting on a two layered soil system
subjected to vertical harmonic excitation are found using cone model. Linear hysteretic material damping is introduced using
correspondence principle. The frequency-amplitude response of a massive foundation is then computed using impedance functions.
To verify the solution field experiments are conducted in two different layered soil systems such as gravel layer over in situ
soil and gravel layer over concrete slab (rigid base). A total 72 numbers of vertical vibration tests on square model footing
were conducted using Lazan type mechanical oscillator, varying the influencing parameters such as depth of top layer, static
weight of foundation and dynamic force level. The frequency-amplitude response in general and in particular the resonant frequencies
and resonant amplitudes predicted by cone model is compared with the results of experimental investigation, which shows a
close agreement. Thus the cone model is reliable in its application to machine foundation vibration on layered soil. 相似文献
106.
Amitabha Ghosh 《Astrophysics and Space Science》1995,227(1-2):41-52
According to the convention normally followed the redshifts of the galaxies in a cluster are assumed to be of purely dopplerian origin. The resulting velocity dispersion, when used in the virial theorem, leads to a very large proportion of dark matter to be present in the galaxy clusters. However, the recently proposed model of velocity dependent cosmic drag cause redshifts of photons and it is necessary to develop a procedure to determine the true velocity dispersion from the gross redshift data. A method for this has been presented in the paper. Coma and Perseus clusters have been investigated using this procedure and theM/L ratios for both were found to be approximately of the order of 30, i.e., approximately the order ofM/L ratios for individual galaxies. A study of them -z relation indicates that the galaxies with higher redshifts have fainter magnitudes. Distortion of the redshift plots and the typical elongation of the core regions along the line-of-sight is also explained. 相似文献
107.
Rupa Ghosh R. K. Sehgal Pradeep Srivastava U. K. Shukla A. C. Nanda D. S. Singh 《Journal of the Geological Society of India》2016,88(5):559-568
We describe an elephant skull recovered from a cliff section of Dhasan river of Marginal Ganga Plain. The dental morphology and cranial features of the skull have been compared with the known species of Elephas from the Indian subcontinent. Although it shows very near resemblance to Elephas namadicus, but being an isolated specimen its specific identity cannot be proclaimed with certainty. As such, the specimen is provisionally referred as E. cf. namadicus. The Optically Stimulated Luminescence ages place this find at ~56 ka BP. This is the first chronologically well constrained report of E. cf. namadicus from the Ganga Plain. 相似文献
108.
109.
110.
Large phillipsite crystal as ferromanganese nodule nucleus 总被引:1,自引:0,他引:1
We report here the occurrence of, to date, the largest (21 × 10 × 8 mm) phillipsite crystal forming the nucleus of a diagenetically formed ferromanganese nodule from the Central Indian Ocean Basin (CIOB). Assuming an average rate of ferromanganese nodule accretion as ~ 2 mm/Ma and that of phillipsite growth as ~ 0.65 mm/Ka, the nucleus material appears to have been growing for ~4.5–5 Ma. Originally surfaced as a rock fragment from late Miocene volcanism, this nucleus was later altered to phillipsite under alkaline, silica-undersaturated, low-temperature conditions through the length of the Neogene sedimentary hiatus. 相似文献