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151.
Das Sarat Kumar Mohanty Ranajeet Mohanty Madhumita Mahamaya Mahasakti 《Natural Hazards》2020,103(2):2371-2393
Natural Hazards - The prediction of liquefaction susceptibility for highly unbalanced database with limited and important input parameters is a crucial issue. The proposed multi-objective feature... 相似文献
152.
Estimation of Coda Wave Attenuation for the National Capital Region, Delhi, India Using Local Earthquakes 总被引:1,自引:0,他引:1
William K. Mohanty Rajesh Prakash G. Suresh A. K. Shukla M. Yanger Walling J. P. Srivastava 《Pure and Applied Geophysics》2009,166(3):429-449
Attenuation of seismic waves is very essential for the study of earthquake source parameters and also for ground-motion simulations,
and this is important for the seismic hazard estimation of a region. The digital data acquired by 16 short-period seismic
stations of the Delhi Telemetric Network for 55 earthquakes of magnitude 1.5 to 4.2, which occurred within an epicentral distance
of 100 km in an area around Delhi, have been used to estimate the coda attenuation Qc. Using the Single Backscattering Model, the seismograms have been analyzed at 10 central frequencies. The frequency dependence
average attenuation relationship Qc = 142f 1.04 has been attained. Four Lapse-Time windows from 20 to 50 seconds duration with a difference of 10 seconds have been analyzed
to study the lapse time dependence of Qc. The Qc values show that frequency dependence (exponent n) remains similar at all the lapse time window lengths. While the change
in Q0 values is significant, change in Q0 with larger lapsetime reflects the rate of homogeneity at the depth. The variation of Qc indicates a definitive trend from west to east in accordance with the geology of the region. 相似文献
153.
Saroja Kumar Barik Satyanarayan Bramha Tapan Kumar Bastia Dibakar Behera Pratap Kumar Mohanty Prasanta Rath 《国际泥沙研究》2019,34(3):251-261
The current study focuses on the vertical profile of different geochemical fractions of phosphorus-loosely bound(Lo–P),aluminium bound(Al–P),iron bound(Fe–P),calcium bound(Ca–P),and organic bound phosphorus(O–P)along with ecological risk assessment of sediment cores from Chilika Lake,eastcoast of India.The percentage contribution of the different fractions to the sedimentary phosphorus in the sediment column of the whole lake are on the order:O–P(33.2%)>Ca–P(20.3%)>Fe–P(18%)>Al–P(6.7%)>Lo–P(0.35%).The Phosphorus Pollution Index(PPI)revealed the contamination of lake sediment with phosphorus.The principal component and cluster analyses highlighted the anthropogenic contribution of phosphorus.The negative loading of Ca–P with Ca points towards its origin from marine shells.The discriminate analysis showed that the variables like Ca–P,bio-available phosphorus(BAP),and pH were able to effectively discriminate the sectors in a significant manner. 相似文献
154.
155.
—The thermodynamic characteristics of the Asian summer monsoon are examined with a global analysis-forecast system. In this study, we investigated the large-scale balances of heat and moisture by making use of operational analyses as well as forecast fields for June, July and August (JJA), 1994. Apart from elucidating systematic errors in the temperature and moisture fields, the study expounds the influence of these errors on the large-scale budgets of heat and moisture over the monsoon region. The temperature forecasts of the model delineate predominant cooling in the middle and lower tropospheres over the monsoon region. Similarly, the moisture forecasts evince a drying tendency in the lower troposphere. However, certain sectors of moderate moistening exist over the peninsular India and adjoining oceanic sectors of the Arabian Sea and Bay of Bengal.¶The broad features of the large-scale heat and moisture budgets represented by the analysis/forecast fields indicate good agreement with the observed aspects of the summer monsoon circulation. The model forecasts fail to retain the analyzed atmospheric variability in terms of the mean circulation, which is indicated by underestimation of various terms of heat and moisture budgets with an increase in the forecast period. Further, the forecasts depict an anomalous diabatic cooling layer in the lower middle troposphere of the monsoon region which inhibits vertical transfer of heat and moisture from the mixed layer of the atmospheric boundary layer to the middle troposphere. In effect, the monsoon circulation is considerably weakened with an increase in the forecast period. The treatment of shallow convection and the use of interactive clouds in the model can reduce the cooling bias considerably. 相似文献
156.
The present study is based on the observed features of the MBL (Marine Boundary Layer) during the Bay of Bengal and Monsoon
Experiment (BOBMEX) — Pilot phase. Conserved Variable Analysis (CVA) of the conserved variables such as potential temperature,
virtual potential temperature, equivalent potential temperature, saturation equivalent potential temperature and specific
humidity were carried out at every point of upper air observation obtained on board ORV Sagar Kanya. The values are estimated
up to a maximum of 4 km to cover the boundary layer. The Marine Boundary Layer Height is estimated from the conserved thermodynamic
profiles. During the disturbed period when the convective activity is observed, the deeper boundary layers show double mixing
line structures. An attempt is also made to study the oceanic heat budget using empirical models. The estimated short-wave
radiation flux compared well with the observations. 相似文献
157.
In this paper, a diagnostic study is carried out with global analysis data sets to determine how the large scale atmospheric circulation affecting the anomalous drought of the Indian summer monsoon 2002. The daily analysis obtained from National Centre for Environmental Prediction/National Centre for Atmospheric Research (NCEP/NCAR) for the month of July is used to investigate the mean circulation characteristics and the large scale energetics over the Indian monsoon domain. Examination of rainfall revealed that the summer monsoon (JJAS) rainfall of 2002 over India is 22% below normal in which the large deficit of 56% below normal rainfall in July. The recent past drought during summer season of 2004 and 2009 are 12 and 23%, respectively, below normal rainfall. The large deficit of rainfall in 2009 is from the June month with 48% below normal rainfall, where as 2004 drought contributed from July (19%) and August (24%). Another significant facet of the rainfall in July 2002 is lowest ever recorded in the past 138 years (1871–2008). The circulation features illustrated weak low level westerly wind at 850 hPa (Somali Jet) in July during large deficit rainfall years of 1987 and 2002 with a reduction of about 30% when compared with the excess and normal rainfall years of 1988 and 2003. Also, tropical easterly jet at 150 hPa reduced by 15% during the deficit rainfall year of 2002 against the excess rainfall year of 1988. Both the jet streams are responsible for low level convergence and upper level divergence leading to build up moisture and convective activity to sustain the strength of the monsoon circulation. These changes are well reflected in reduction of tropospheric moisture profile considerably. It is found that the maximum number of west pacific cyclonic system during July 2002 is also influenced for large deficit rainfall over India. The dynamic, thermodynamic and energetic clearly show the monsoon break type situation over India in the month of July 2002 resulting less convective activity and the reduction of moisture. The large diabatic heating, flux convergence of heat and moisture over south east equatorial Indian Ocean are also responsible for drought situation in July 2002 over the Indian region. 相似文献
158.
K. Alapaty S. Raman R. V. Madala U. C. Mohanty 《Meteorology and Atmospheric Physics》1994,53(1-2):33-49
Summary Two numerical experiments are performed using a nested grid regional model to study the performance of the Kuo and the Betts-Miller cumulus parameterization schemes in simulating the rainfall during an active monsoon period. Results indicate that the monsoon circulation features, such as the Somali jet and monsoon depression are better simulated with the Kuo scheme. With the Kuo scheme, predicted intensity and associated rainfall of the monsoon depression are in good agreement with the observations. Uncertainty in the adjustment parameters in the Betts-Miller scheme appears to have lead to the poor prediction of rainfall. Also, the Betts-Miller scheme showed considerable sensitivity to the convergence in the lower troposphere in the initial conditions over the Arabian Sea, leading to a prediction of a spurious intense tropical cyclone. This cyclone replaced the normal heat-low over the desert region. Rainfall distribution and its maximum along the west coast of India were predicted better with the Kuo scheme. Area-averaged convective heating rates indicated that the cumulus convection is deeper and more intense with the Kuo scheme. Also, area averaged evaporation rates far exceeded the rainfall rates with the Betts-Miller scheme while with the Kuo scheme these rates are in balance after the spinup period. Forecast erros in the zonally averaged specific humidities indicate that the model atmosphere is more humid with the Betts-Miller scheme.With 14 Figures 相似文献
159.
Makarand A. Kulkarni Ankita Singh U. C. Mohanty 《Theoretical and Applied Climatology》2012,109(3-4):497-505
The regional trends are evaluated in the frequency of various rain events using the daily gridded (1°?×?1°) rainfall dataset for the time period 1901–2004, prepared by the India Meteorological Department (IMD). In terms of intensity, the events are classified as low, moderate, heavy and extreme heavy, while short and long spells are classified on the basis of duration of rainfall. The analytical (parametric) and the empirical (bootstrap) techniques were used to incorporate the impact of spatial correlation in regional trends. It is observed that, consideration of spatial correlation reduces the significance level of the trends and the effective number of grid points falling under each category. Especially, the noticeable cross-correlation have reduced the significance of the trends in moderate and long spell rain events to a large extent, while the significance of trends in the extreme heavy and short spell events is not highly affected because of small cross-correlation. 相似文献
160.
In this paper we present an experimental approach aimed at assessing the correlation between fracture toughness (K
IC) and fracture roughness of two granitic rocks (Barre and Stanstead granites) exhibiting significant fracture toughness anisotropy.
Roughness values have been estimated for fractured surfaces obtained from Chevron Cracked Notch Brazilian Disc samples failed
under mode I along three orthogonal planes with respect to their microstructural fabrics. There exists a clear correlation
between roughness and toughness within each rock examined along the three planes. Specific orientation of micro-crack alignment
could result in preferred out-of-plane propagation of the test-crack irrespective of grain-size distribution. These experimental
observations reinforce the hypothesis of the existence of a link among pre-existing petrofabric anisotropy, fracture toughness,
fracture roughness, and the evolution and extent of the associated induced fractures within the process zone of granitic rocks
along specific directions. This study also highlights the need for employment of pre-failure and advanced post-failure diagnostic
techniques in quantifying these inter-relationships. 相似文献