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31.
In this study, we have investigated the seasonality and long-term trends of major biomass burning (BB) sources over South and Southeast Asia (S-SE Asia). The activities of BB and related emissions show bi-modal seasonality in S-SE Asia. From January to May period, the BB dominates in the northern hemisphere parts of S-SE Asia. From July to September, the activities shift to the southern hemisphere where the emissions from Indonesian and Malaysian islands make largest contributions. Overall, the activities of BB are lowest during October–December period in S-SE Asia. The seasonality of BB intensity and rain are just opposite in the phase over India. The climatological (1997–2008) emissions of carbon monoxide (CO), oxides of nitrogen (NOx) and non-methane hydrocarbons (NMHCs) show strong spatio-temporal variation. The trends show large inter-annual variations with highest and lowest values during years 1997 and 2000, respectively. In the southern hemisphere parts of S-SE Asia mainly in Indonesia, the intensity of biomass fires has been modulated by the large scale climatic phenomena like El Niño and Southern Oscillation (ENSO). The annual emissions of trace gases in southern hemisphere region during the El Niño years exceed to those for the normal years. The estimates for northern hemisphere region during the La Niña years were significantly higher than those for the normal years. The Model for Ozone And Related Chemical Tracers (MOZART) simulations of columnar CO and NOx tend to capture the prominent features of BB emissions in S-SE Asia. The impacts of extensive fires in Indonesia during El Niño year of 2006 compared to a normal year of 2005 were clearly seen in the MOZART-4 simulations of both CO and NOx. 相似文献
32.
In this paper, the problem of spatially homogeneous and an isotropic Bianchi type-1 space time with perfect fluid distribution
is considered in Barber's second theory of gravitation. To obtain determinate solutions, we have assumed the equation of statep= γρ, 0 ≤ γ ≤ 1. It is observed that the general fluid distribution degenerates isotropic vacuum model whenγ = 1 and Λ < 0.
Further it is observed that the vacuum model obtained in case of γ = 0, ρ = 0 andΛ = 0, reduces to well known Kasner model
in Einstein's theory. Some physical and geometrical aspects of the models together with singularities in the models are also
discussed
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
33.
34.
Using the standard reductive perturbation technique, nonlinear cylindrical and spherical Kadomtsev-Petviashvili (KP) equations are derived for the propagation of ion acoustic solitary waves in an unmagnetized collisionless plasma with nonthermal electrons and warm ions. The influence of nonthermally distributed electrons and the effects caused by the transverse perturbation on cylindrical and spherical ion acoustic waves (IAWs) are investigated. It is observed that the presence of nonthermally distributed electrons has a significant role in the nature of ion acoustic waves. In particular, when the nonthermal distribution parameter ?? takes certain values the usual cylindrical KP equation (CKPE) and spherical KP equation (SKPE) become invalid. One then has to have recourse to the modified CKPE or SKPE. Analytical solutions of both CKPE and SKPE and their modified versions are discussed in the present paper. The present investigation may have relevance in the study of propagation of IAWs in space and laboratory plasmas. 相似文献
35.
Tapan K. Barik Surya N. Swain Bijayalaxmi Sahu Bibarani Tripathy Usha R. Acharya 《Marine Ecology》2021,42(1):e12632
Individual specimens of Myripristis jacobus Cuvier, 1829 and Scarus taeniopterus Lesson, 1829 were collected from Gopalpur‐on‐sea, Odisha coast, Bay of Bengal. Both the fish samples were assigned species level tags using the conventional taxonomic methods. The capture of both the fish species is of particular interest in that they were new to the Bay of Bengal. Molecular analysis using the mitochondrial cytochrome oxidase subunit I (COI) gene showed high confidence sequence similarity in species identification. The resultant phylogenetic relationships strongly support the monophyly of both the genus with congruent clustering of both the species according to their morphological identification. In addition, the time tree produced is in complete agreement with the recent studies. These studies conclusively prove that both the species might have been originated during the middle to the late Miocene period. Furthermore, both fish species are typical inhabitants of stigmatized coral reefs, confined to the reef regions. These fish species perhaps migrated to the Bengal Bay from the Andaman and Nicobar Islands reef regions because of climatic changes. 相似文献
36.
Biraja Kumar Sahu Sanjiba Kumar Baliarsingh Aneesh A. Lotliker Chandanlal Parida Suchismita Srichandan Kali Charan Sahu 《Ocean Science Journal》2017,52(2):301-306
Clear thermal inversion was observed with cold surface waters (< 24°C) overlying the warm (> 26°C) subsurface water in the coastal waters of the northwestern Bay of Bengal during winter (January 2015). Simultaneously, preponderance of the cyanobacteria Trichodesmium erythraeum was observed dominating the phytoplankton community with > 90% of total population, reaching maximum density of 9.8 × 105 filaments/L. Further, the Trichodesmium predominance was associated with low water temperature (< 24°C). 相似文献
37.
Baskar Balakrishnan Biraja Kumar Sahu Jayappriyan Kothilmozhian Ranishree Arockia Vasanthi Lourduraj Marimuthu Nithyanandam Nandakumar Packiriswamy Prabakaran Panchatcharam 《Environmental Earth Sciences》2017,76(1):58
Heavy metals are known to pose a potential threat to terrestrial and aquatic flora and fauna. Due to increasing human influence, heavy metal concentrations are rising in many mangrove ecosystems. Therefore, an assessment of heavy metal (Cd, Cr, Cu, Ni, Pb, Fe, Mn, and Zn) concentrations was conducted within the bulk soil and rhizosphere soil of Avicennia marina at the Pichavaram Mangrove Forest in India. The rhizosphere soil showed higher concentrations of metals than the bulk soil. Compared to the bulk soil, the metals Cd, Fe, Mn, and Zn were 6.0–16.7% higher, whereas Cr, Cu, Ni, and Pb were 1.7–2.8% higher concentration. Among the three selected sampling sites (dense mangrove forest, estuarine region, and sea region), the sea region had the highest concentration of all heavy metals except Zn. The trend of the mean metal concentration was Fe > Mn > Cr > Ni > Cu > Pb > Zn > Cd. Heavy metals concentrations elevated by the 2004 tsunami were persistent even after 4 years, due to sedimentary soil processes, the rhizosphere effect of mangroves, and anthropogenic deposition. Analysis of the heavy metal-resistant bacteria showed highest bacterial count for Cr-resistant bacteria and rhizosphere soil. The maximum level of heavy metal-resistant bacteria was observed at the site with the highest heavy metal contamination. The heavy metal-resistant bacteria can be used as indicator of heavy metal pollution and furthermore in bioremediation. 相似文献
38.
A. J. Litta U. C. Mohanty S. Kiran Prasad M. Mohapatra Ajit Tyagi S. C. Sahu 《Natural Hazards》2012,61(3):1219-1242
A severe thunderstorm produced a tornado (F3 on the Fujita-Pearson scale), which affected Rajkanika block of Kendrapara district
of Orissa in the afternoon of March 31, 2009. The devastation caused by the tornado consumed 15 lives and left several injured
with huge loss of property. The meteorological conditions that led to this tornado have been analyzed. An attempt is also
made to simulate this rare event using Non-hydrostatic Mesoscale Model (NMM) core of the Weather Research and Forecasting
(WRF) system with a spatial resolution of 4 km for a period of 24 h, starting at 0000 UTC of March 31, 2009. The atmospheric
settings resulted from synoptic, surface, upper air, satellite and radar echo studies were favorable for the occurrence of
a severe thunderstorm activity over Rajkanika. The model-simulated meteorological parameters are consistent with each other,
and all are in good agreement with the observation in terms of the region of occurrence of the intense convective activity.
The model has well captured the vertical motion. The core of the strongest winds is shown to be very close to the site of
actual occurrence of the event. The wind speed is not in good agreement with the observation as it has shown the strongest
wind of only 20 ms−1, against the estimated wind speed of 70 ms−1. The spatial distributions as well as intensity of rainfall rates are in good agreement with the observation as model simulated
35.4 mm against the observed rainfall of 41 mm over Chandbali. The results of these analyses demonstrated the capability of
high-resolution WRF–NMM model in simulation of severe thunderstorm events. 相似文献
39.
Sudip Jyoti Sahu Bibhash Nath Sharmi Roy Biswapati Mandal Debashis Chatterjee 《Environmental Earth Sciences》2012,65(3):813-821
Groundwater contaminated with arsenic (As), when extensively used for irrigation, causes potentially long-term detrimental
effects to surface soils. Such contamination can also directly affect human health when irrigated crops, such as rice, vegetable
and fruits, are used for human consumption. Therefore, an understanding of the leaching behavior of As in surface soils is
of high importance, because such behavior may increase the bioavailability of As in the soil horizon. In this study, we have
investigated the role of phosphate ions in leaching and bioavailability of As in the soil horizon, where drinking groundwater
contains elevated levels of As (≥50 μg/L). Soil and groundwater samples were characterized in the laboratory and measured
for physical and chemical constituents. The soils are generally neutral to slightly alkaline in character (pH range 7.5–8.1)
with low to moderate levels of free Fe2O3, Al2O3, CaCO3, organic carbon, and clay content. The measured electrical conductivity (mean 599 μS/cm) of the soils demonstrates their
non-saline nature. The Eh values (range −37 to −151 mV) of the groundwater indicate anoxic condition with low to moderate
levels of bicarbonate (range 100–630 mg/L) and phosphate (range 0.002–4.0 mg/L). The arsenic content (range 50–690 μg/L; mean
321 μg/L) in groundwater has exceeded both WHO recommended guideline values (10 μg/L) and the National safe drinking water
limit (50 μg/L). Regression analyses demonstrate that the bioavailability of As in the soil horizon is mainly controlled by
the composition of free Fe2O3 and CaCO3 content of the soils. However, application of P could increase bioavailability of As in the soil horizon and become available
to plants for uptake. 相似文献
40.
In this paper, we have investigated plane symmetric inhomogeneous cosmological models in the presence of massless scalar field
in modified theory of general relativity when source of the gravitational field is a perfect fluid. The physical and geometrical
aspects of the models together with singularity involved in the models are also discussed.
PACS Nos.: 04.50. + h•4.20.Cv• 4.20.Dw 相似文献