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51.
52.
Natural Hazards - Investigations of micro- and low-magnitude earthquakes in the Kangra-Chamba region of the NW Himalaya were performed to evaluate the relationship between earthquake source,... 相似文献
53.
This paper deals with kinetics and equilibrium studies on the adsorption of arsenic species from simulated groundwater containing arsenic (As(III)/As(V), 1:1), Fe, and Mn in concentrations of 0.188, 2.8, and 0.6 mg/L, respectively, by Ca2+ impregnated granular activated charcoal (GAC‐Ca). Effects of agitation period and initial arsenic concentration on the removal of arsenic species have also been described. Although, most of the arsenic species are adsorbed within 10 h of agitation, equilibrium reaches after ~24 h. Amongst various kinetic models investigated, the pseudo second order model is more adequate to explain the adsorption kinetics and film diffusion is found to be the rate controlling step for the adsorption of arsenic species on GAC‐Ca. Freundlich isotherm is adequate to explain the adsorption equilibrium. However, empirical polynomial isotherm gives more accurate prediction on equilibrium specific uptakes of arsenic species. Maximum specific uptake (qmax) for the adsorption of As(T) as obtained from Langmuir isotherm is 135 µg/g. 相似文献
54.
Evaluation of performance of non‐invasive upgrade strategy for beam–column sub‐assemblages of poorly designed structures under seismic type loading
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Beam–column sub‐assemblages are the one of the most vulnerable structural elements to the seismic loading and may lead to devastating consequences. In order to improve the performance of the poorly/under‐designed building structures to the critical loading scenarios, introduction of steel bracing at the RC beam–column joint is found to be one of the modern and implementable techniques. In the present work, a diagonal metallic single haunch/bracing system is introduced at the beam–column joints to provide an alternate load path and to protect the joint zone from extensive damage because of brittle shear failure. In this paper, an investigation is reported on the evaluation of tae influence of different parameters, such as angle of inclination, location of bracing and axial stiffness of the single steel bracing on improving the performance through altering the force transfer mechanism. Numerical investigations on the performance of the beam–column sub‐assemblages have been carried out under cyclic loading using non‐linear finite element analysis. Experimentally validated numerical models (both GLD and upgraded specimen) have been further used for evaluating the performance of various upgrade schemes. Cyclic behaviour of reinforcement, concrete modelling based on fracture energy, bond‐slip relations between concrete and steel reinforcement have been incorporated. The study also includes the numerical investigation of crack and failure patterns, ultimate load carrying capacity, load displacement hysteresis, energy dissipation and ductility. The findings of the present study would be helpful to the engineers to develop suitable, feasible and efficient upgrade schemes for poorly designed structures under seismic loading. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
55.
Sisir K. Mondal 《Journal of the Geological Society of India》2009,73(1):36-51
The Archaean cratonic nuclei of the continents are important as they contain the most significant evidences for the evolution
of Earth e.g. the greenstone sequences. In the Indian Shield, one of the important cratons is the Singhbhum craton, where
nearly 95% of the Indian chromite deposits and only PGE deposits are located which are hosted within Mesoarchaean ultramafic-mafic
rock sequences. The ultramafic units occur as sill like intrusions within the Iron Ore Group (IOG) greenstone belts and often
associated with gabbroic intrusions. In the Nuasahi and Sukinda mining districts of these occurrences, detailed petrological,
geochemical and isotopic studies have been carried out in the last decades. Petrological and geochemical studies indicate
a supra-subduction zone (SSZ) tectonic settings in Archaean for the origin of these ultramafic-mafic sequences. The Os isotopic
and platinum group element (PGE) geochemical studies of chromites from the two mining districts indicate presence of a subchondritic
source mantle domain beneath and within the Singhbhum craton similar to the Zimbabwean craton of southern African continent.
The Os model age calculation indicates melt extraction from a subcontinental lithospheric mantle (SCLM) before 3.7 Ga which
is similar to the other ancient cratons. As a whole the study supports the premise that India was part of the African continent
in pre-Gondwana times and even in early Archaean and suggest possible amalgamation and building up of a supercontinent during
late Archaean. However, in comparison with other occurrences, the Singhbhum craton of the Indian Shield and the Zimbabwean
craton in southern Africa are characterized by the presence of subchondritic lithospheric mantle domains within the SCLM,
which were developed prior to 3.7 Ga. 相似文献
56.
S. Mondal J.D.A. Piper L. Hunt G. Bandyopadhyay S. Basu Mallik 《Journal of Asian Earth Sciences》2009,34(4):493-506
Palaeomagnetic and magnetomineralogical results are reported from charnockites in basement terrane at the eastern sector of the WSW–ENE granulite belt of South India. Magnetite is the dominant ferromagnet identified by rock magnetic and optical study; it is present in several phases including large homogeneous titanomagnetites and disseminated magnetite in microfractures linked to growth stages ranging from primary charnockite formation to uplift decompression and exhumation within the interval ~2500–2100 Ma. Several components of magnetization are resolved by thermal demagnetization and summarized by four pole positions; in the northern (Pallavaram) sector these are P1 (33°N, 99°E, dp/dm = 8/9°) and P2 (79°N, 170°E, dp/dm = 3/6°), and in the southern (Vandallur) sector they are V1 (23°N, 116°E, dp/dm = 8/9°) and V2 (26°S, 136°E, dp/dm = 5/10°). These magnetizations are linked to uplift cooling of the basement and unblocking temperature spectra suggest acquisition sequences P1 → P2 and V1 → V2 in each case implying movement of the shield from higher to lower palaeolatitudes sometime between 2500 and 2100 Ma. Palaeomagnetic poles from the cratonic nuclei of Africa, Australia and India all identify motion from higher to lower palaeolatitudes in Early Palaeoproterozoic times, and this is dated ~2400 and ~2200 Ma in the former two shields. The corresponding apparent polar wander (APW) segments match the magnetization record within the charnockite basement terranes of southern India to yield a preliminary reconstruction of the ‘Ur’ protocontinent, the oldest surviving continental protolith with origins prior to 3000 Ma. Although subject to later relative movements these nuclei seem to have remained in proximity until the Mesozoic break-up of Gondwana. 相似文献
57.
Aquifer characteristics and its modeling around an industrial complex,Tuticorin, Tamil Nadu,India: A case study 总被引:3,自引:0,他引:3
Anthropogenic pollution of shallow groundwater resources due to industrial activities is becoming a cause of concern in the
east coastal belt of the state of Tamil Nadu, India. Integrated hydrogeological, geophysical and tracer studies were carried
out in the coastal region encompassing an industrial complex. The objective has been to gain knowledge of aquifer characteristics,
ascertaining groundwater movement and its flow direction, which would in turn reveal the possibility of contamination of groundwater
regime and its better management. The results of multi-parameters and model study indicate that the velocity of groundwater
flow ranges from 0.013 m/d to 0.22m/d in and around the industrial complex in upstream western part of the catchment and 0.026
m/d to 0.054m/d in the downstream eastern part, near the coast. These parameters are vital for the development of groundwater
management scheme. 相似文献
58.
Improvement of groundwater quality due to fresh water ingress in Potharlanka Island, Krishna delta, India 总被引:1,自引:0,他引:1
Hydrochemical study had been carried out on the groundwater resources of Potharlanka Island, Krishna delta, India. Groundwater
samples were collected and analyzed at 42 sites in December 2001 and October 2006. A comparative study of hydrochemical data
indicates: groundwater is mildly alkaline with a pH of 7.0–8.2; electrical conductivity (EC) varies from 605 to 5,770 μS/cm
in December 2001, and 652–5,310 μS/cm in October 2006. More than 62% of the groundwater samples in 2006 have TDS value <2,000 mg/l,
which is within permissible limit of potable water, but 57% of the samples in 2001, are higher than the maximum permissible
limit. Extremely low HCO3/Cl and variable high Mg/Ca (molar ratios) had been indicated the transformation of the fresh groundwater aquifer systems
to saline in 2001. Groundwater of this Island is mainly classified as Na–Cl and mixed types. A high percentage of Na–Cl type
of these waters indicates the possibility of seawater ingression/intrusion process during 2001 and comparatively mixed water
type indicates the dilution activities of groundwater. Excessive withdrawal of groundwater has caused the increase of saline
water intrusion. Improvement of groundwater quality in this Island due to artificial recharge structures made by NGRI under
RGNDWM project and affects of the flood due to heavy rainfall of the months of September–October 2005 are discussed in this
paper. 相似文献
59.
Md. Surabuddin Mondal A. C. Pandey R. D. Garg 《Journal of the Indian Society of Remote Sensing》2008,36(1):69-76
Water is the most important natural resource which forms the core of the ecological system. The advent of remote sensing has
opened up new vistas in groundwater prospect evaluation, exploration and management. The groundwater resources of the study
area, Rishikesh region of Garhwal Himalayas, are under threat due to population pressure caused by expanding tourism in this
region. This entails sustainable and judicious use of this precious resource. The groundwater prospect evaluation in Rishikesh
region has been attempted based on hydrogeomorphological mapping of the area consisting of thematic maps of hydrogeomorphology,
geology, drainage, lineament, slope and relief using high resolution IRS-1C LISS III and PAN merged satellite images. The
Rishikesh region exhibits diverse hydrogeomorphological conditions where the groundwater regime is controlled mainly by topography
and geology. A probability-weighted approach has been applied during overlay analysis in ArcMap GIS environment. The overlay
analysis allows a linear combination of weights of each thematic map with respect to ground water potential. Good groundwater
prospects dominate in the area with more than 50% of the study area showing moderate to excellent potential. The study shows
that the remote sensing and geoinformatics techniques can be applied effectively for groundwater prospect evaluation. 相似文献
60.
The variation of temporal fractal dimension D2 (t) value may be well applied for understanding the future large earthquakes. In this present analysis the time series of inter-occurrence of earthquakes of consecutive hundred events window in Himalayan region is analyzed. We observed the variation in D2 (t) values in the range of 0.19 to 0.68 indicating the variation of clustering of events with respect to time. The multifractal nature of earthquakes is also investigated by plotting Dq(t) versus q. The result shows the temporal distribution of earthquakes have multifractal structure of definitive pattern rather than random pattern. 相似文献