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11.
Using the sunspot numbers reported during the Maunder minimum and the empirical relations between the mode frequencies and
solar activity indices, the variations in the total solar irradiance and 10.7 cm radio flux for the period 1645 to 1715 is
estimated. We find that the total solar irradiance and radio flux during the Maunder minimum decreased by 0.19% and 52% respectively,
as compared to the values for solar cycle 22.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
12.
S. C. Tripathy C. B. Dwivedi A. C. Das A. R. Prasanna 《Journal of Astrophysics and Astronomy》1993,14(2):103-114
In this paper, the analytical and numerical results of the stability analysis of the accretion disk at the inner boundary
is presented. Including the effect of finite conductivity in the disk dynamics, a simple calculation considering only the
radial perturbation has been carried out. Within local approximation, it is concluded that the disk is stable to Kelvin-Helmholtz
and resistive electromagnetic modes whereas the magnetosonic mode can destabilise the disk structure. 相似文献
13.
S. C. Tripathy C. B. Dwivedi A. C. Das A. R. Prasanna 《Journal of Astrophysics and Astronomy》1993,14(3-4):167-179
A two-dimensional instability analysis for a magneto-keplerian disk flow around a compact object is presented here. Using
the eigenvalue technique, linearly coupled perturbed equations have been numerically solved within the local approximation.
It is concluded that Kelvin-Helmholtz, magnetosonic (fast and slow) and resistive electromagnetic modes exist. However, only
the magnetosonic mode can destabilise the disk structure. Further, we discuss the properties of different modes as a function
of disk parameters and plot the eigenmode structures for different physical quantities. 相似文献
14.
Barik Tapan K. Swain Surya N. Sahu Bijayalaxmi Tripathy Bibarani Acharya Usha R. 《海洋学报(英文版)》2020,39(6):26-35
Marine ecosystems provide a wide variety of diverse habitats that frequently promote migration and ecological adaptation. The extent to which the geographic distribution of marine organism has reshaped by human activities remains underappreciated. The limitations intrinsic to morphology-based identification systems have engendered an urgent need for reliable genetic methods that enable the unequivocal recognition of fish species,particularly those that are prone to overexploitation and/or market substitution. In the present study, however, an attempt has been taken to identify two locally adapted fish species, Siganus sutor(Valenciennes, 1835) and Seriolina nigrofasciata(Rüppell, 1829) of order Perciformes, which happens to be the first record in Odisha coast,Bay of Bengal. The diagnostic characteristics of Siganus sutor are: dorsal fin XIII-10, anal fin VII-9, pectoral fin 15,pelvic fin II-3, while that of Seriolina nigrofasciata dorsal fin VI-I-35, anal fin I-17, pectoral fin 16, pelvic fin 5. All COI barcodes generated in this study were matched with reference sequences of expected species, according to morphological identification. Bayesian and likelihood phylogenetic trees were drawn based on DNA barcodes and all the specimens clustered in agreement with their taxonomic classification at the species level. The phylogeographic studies based on haplotype network and migration rates suggest that both the species were not panmitic and the high-frequency population distribution indicates successful migration. The result of this study provides an important validation of the use of DNA barcode sequences for monitoring species diversity and changes within a complex marine ecosystem. 相似文献
15.
Nihar R. Tripathy Hari B. Srivastava Manish A. Mamtani 《Journal of Asian Earth Sciences》2009,34(1):26-37
The footwall of the Main Central Thrust (MCT) Zone along the Bhagirathi valley comprises a wide zone of mylonitic quartzite and deep-level tectonites. The systematic variation of finite strain parameters (Es, k and v) in the mylonites indicates heterogeneous deformation, which is determined to vary between, simple shear and non-coaxial flattening type. In such a strain regime the outer boundary of the quartz clasts are no longer preserved thus leading to an error in finite strain measurement.In order to supplement the finite strain studies, Anisotropy of Magnetic Susceptibility (AMS) analyses were carried out on the mylonitic quartzites. A systematic variation in degree of anisotropy (P′) with distance from the MCT is documented and is interpreted to be tectonic in origin. Based on these results it is concluded that P′ can be used as a strain-intensity gauge at least on an outcrop scale, where a systematic variation in P′ values from one part of the outcrop to the other can be established. However, the quantitative relation between principal axes of finite strain ellipsoid and AMS axes, magnitude of principal susceptibility difference (ΔK1 and ΔK3) and finite strain magnitude (ε1=ln 1 + e1 and ε3=ln 1 + e3) were related by a logarithmic relationship with a correlation coefficient of 0.844. 相似文献
16.
Phenomenal storm surge levels associated with cyclones are common in East Coast of India. The coastal regions of Andhra Pradesh
are in rapid stride of myriad marine infrastructural developments. The safe elevations of coastal structures need a long-term
assessment of storm surge conditions. Hence, past 50 years (1949–1998), tropical cyclones hit the Bay are obtained from Fleet
Naval Meteorological & Oceanographic Center, USA, and analyzed to assess the storm surge experienced around Kakinada and along
south Andhra Pradesh coast. In this paper, authors implemented Rankin Hydromet Vortex model and Bretschneider’s wind stress
formulation to hindcast the surge levels. It is seen from the hindcast data that the November, 1977 cyclone has generated
highest surge of the order of 1.98 m. Extreme value analysis is carried out using Weibull distribution for long-term prediction.
The results reveal that the surge for 1 in 100-year return period is 2.0 m. Further the highest surge in 50 years generated
by the severe cyclone (1977) is numerically simulated using hydrodynamic model of Mike-21. The simulation results show that
the Krishnapatnam, Nizampatnam and south of Kakinada have experienced a surge of 1.0, 1.5 and 0.75 m, respectively. 相似文献
17.
We investigate the spatial and temporal variations of the high-degree mode frequencies calculated over localized regions of the Sun during the extended minimum phase between solar cycles 23 and 24. The frequency shifts measured relative to the spatial average over the solar disk indicate that the correlation between the frequency shift and magnetic field strength during the low-activity phase is weak. The disk-averaged frequency shifts computed relative to a minimal activity period also reveal a moderate correlation with different activity indices, with a maximum linear correlation of about 72?%. From the investigation of the frequency shifts at different latitudinal bands, we do not find a consensus period for the onset of solar cycle 24. The frequency shifts corresponding to most of the latitudes in the northern hemisphere and 30° south of the equator indicate the minimum epoch to be February 2008, which is earlier than inferred from solar activity indices. 相似文献
18.
We have obtained empirical relations between the p-mode frequency shift and the change in solar activity indices. The empirical relations are determined on the basis of frequencies obtained from BBSO and GONG stations during solar cycle 22. These relations are applied to estimate the change in mean frequency for the cycle 21 and 23. A remarkable agreement between the calculated and observed frequency shifts for the ascending phase of cycle 23, indicates that the derived relations are independent of epoch and do not change significantly from cycle to cycle. We propose that these relations could be used to estimate the shift in p-mode frequencies for past, present and future solar activity cycles, if the solar activity index is known. The maximum frequency shift for cycle 23 is estimated to be 265±90 nHz, corresponding to a predicted maximum smoothed sunspot number 118.1±35. 相似文献
19.
S. Panigrahy J. S. Parihar N. K. Patel V. K. Dadhwal T. T. Medhavy B. K. Ghose N. Ravi K. C. Pani B. K. Panigrahy V. N. Sridhar R. R. Mohanty S. K. Nanda D. P. Tripathy P. K. Mishra H. P. Bhatt S. R. Oza S. Sudhakar K. S. Sudha P. Kumar N. K. Das 《Journal of the Indian Society of Remote Sensing》1991,19(1):17-26
Rice is one of the most important foodgrains grown in India. Attempts have been made to estimate kharif rice acreage of Orissa state since 1986 using digital remote sensing data from Landsat MSS/TM and/or IRS-1A. Accuracies of the estimates obtained have been evaluated against BES (Bureau of Economics and Statistics) estimate. This paper describes the methodology adopted for rice acreage estimation of Orissa state, the results obtained for three years, i.e. 1986–87, 1988–89 and 1989–90, and their accuracy. 相似文献
20.
Y. Zhu J. Ishizaka S. C. Tripathy S. Wang Y. Mino T. Matsuno D. J. Suggett 《Journal of Oceanography》2016,72(5):761-776
Fast repetition rate fluorometry (FRRf) provides a potential means to examine marine primary productivity; however, FRRf-based productivity estimations require knowledge of the electron requirement (K) for carbon (C) uptake (K C) to scale an electron transfer rate (ETR) to the CO2 uptake rate. Most previous studies have derived K C from parallel measurements of ETR and CO2 uptake over relatively short incubations, with few from longer-term daily-integrated periods. Here we determined K C by comparing depth-specific, daily ETRs and CO2-uptake rates obtained from 24-h on-deck incubation experiments undertaken on seven cruises in Ariake Bay, Japan, from 2008 to 2010. The purpose of this study was to determine the extent of variability of K C and to what extent this variability could be reconciled with the prevailing environmental conditions and ultimately to develop a method for determining net primary productivity (NPP) based on FRRf measurements. Both daily ETR and K C of the upper layer varied considerably, from 0.5 to 115.7 mmol e? mg Chl-a ?1 day?1 and 4.1–26.6 mol e? (mol C)?1, respectively, throughout the entire data set. Multivariate analysis revealed a strong correlation between daily photosynthetically active radiation (PAR) and K C (r 2 = 0.94). A simple PAR-dependent relationship derived from the data set was used for generating K C, and this relationship was validated by comparing the FRRf-predicted NPP with the 13C uptake measured in 2007. These new observations demonstrate the potential application of FRRf for estimating regional NPP from ETR. 相似文献