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21.
22.
The origin of hydrodynamic turbulence in rotating shear flow is a long standing puzzle.Resolving it is especially important in astrophysics when the flow's angular momentum profile is Keplerian which forms an accretion disk having negligible molecular viscosity.Hence,any viscosity in such systems must be due to turbulence,arguably governed by magnetorotational instability,especially when temperature T ≥10 5.However,such disks around quiescent cataclysmic variables,protoplanetary and star-forming disks,and t... 相似文献
23.
Natural Hazards - The timely and accurate assessment of casualties is the key for and basis of emergency rescue work after an earthquake. In this paper, through exponential fitting of historical... 相似文献
24.
25.
Amitabha Mukhopadhyay 《Ground water》1999,37(3):458-464
26.
Eman Al-Awadi Michael Quinn Amitabha Mukhopadhyay Andre Hauser Adnan Akber Adel Al-Haddad Majed Al-Rashedi 《Environmental Geology》2009,56(5):877-889
A study, aimed at characterizing the nature of anthropogenic and biogenic hydrocarbon contamination in the groundwater of
Kuwait, was carried out using fluorescence spectroscopy and other analytical techniques. The results of these analyses have
demonstrated that the groundwater in certain areas of northern Kuwait has been significantly impacted by contamination originating
from the oil-contaminated surface soils. The study revealed that a water-soluble fraction (WSF) of the crude oil surface contamination
appeared to be slowly leaching into the freshwater lenses located in the area. The study also showed that hydrocarbon pollutants
were practically absent in the brackish water areas of central and southern Kuwait, except for a few isolated sites. However,
nonpetroleum hydrocarbons, with ultraviolet-visible absorption characteristics and fluorescence characteristics typically
associated with humic substances, were observed at a few sites in the brackish water fields. 相似文献
27.
Estimates of motion and strain rates across active faults in the frontal part of eastern Himalayas in North Bengal from GPS measurements 总被引:1,自引:0,他引:1
Within the 2500 km stretch of the Himalayas, a narrow window between longitudes 88.185°E and 88.936°E in the frontal Himalayas in North Bengal, crisscrossed by several active fault traces, presents an interesting region for crustal deformation study. We have estimated velocities of 8 GPS stations located in this area and the accumulating strain rate by two different methods. A total shortening of 11.1 ±1.5 mm yr−1 is occurring across a set of four E–W running faults: Gorubathan, Matiali, Chalsa and Baradighi. The strain rate becomes higher in the NE part of the network, reaching −(0.25 ± 0.12) μstrain yr−1 with azimuth 21°. A statistically significant extension of 10.9 ± 1.6 mm yr−1 is estimated across the Gish transverse fault with a maximum strain rate of 0.36 ± 0.08 μstrain yr−1 with azimuth 103°. The accumulating strain will be probably released through future earthquakes. 相似文献
28.
Coda of local earthquakes that occurred during 2006–2007 are used to study the attenuation characteristics of the Garhwal–Kumaun
Himalayas. The coda attenuation characteristics are represented in terms of coda Q or Q
c
. It is observed that Q
c
increases with frequency. Q
c
also varies with increase in lapse time of coda waves. Q
c
increases up to an 85-s average lapse time. This is similar to observations around the world reported by many workers who
have interpreted this as a manifestation of the fact that heterogeneity decreases with depth. However, around a 90-s average
lapse time Q
c
is lower than its values for lower and higher average lapse times. This is interpreted as an indication of possible presence
of a fluid-filled medium or a medium having partial melts at around a 160-km depth. Q
0, i.e., Q
c
at 1 Hz, increases, and frequency parameter n decreases with increasing lapse time, barring around a 90-s lapse time. This
again shows that in general, heterogeneity decreases with increasing depth. The Q
0 and n values for smaller lapse times are similar to those for tectonically active areas. By comparing Q
c
values obtained in this study with those obtained by us using the 1999 Chamoli earthquake aftershocks, it is concluded that
the crust is turbid and the mantle is more transparent. However, whether the variation in Q
c
values between 1999 and 2006–2007 is temporal or not cannot be definitely established from the available data set. 相似文献
29.
Saddle-shaped reticulate Nummulites from the Early Oligocene rocks of Khari area, SW Kutch, India is reported here for the first time. Unusual shape of this
Nummulites is due to the curved nature of the coiling plane, indicating space constrained postembryonic test growth. With regular development
of chambers, septa and septal filaments, the saddle-shaped Nummulites constitutes the third morphotype of N. cf. fichteli Michelotti form A. Other morphotypes of the species reported earlier include inflated lenticular and conical tests. Multiple
morphotypes of N. cf. fichteli form A indicates varied test growth in response to substrate conditions. Morphological variability exhibited by N. cf. fichteli form A from Kutch and some Early Oligocene reticulate Nummulites from the Far East are comparable. This faunal suite is morphologically distinct from the contemporary reticulate Nummulites of the European localities. 相似文献
30.
Basab Mukhopadhyay Manoj Mukhopadhyay Sujit Dasgupta 《Journal of the Geological Society of India》2011,78(2):131-146
The plate margin features defining the Arabian Sea Triple Junction (ASTJ) are: the Aden Ridge (AR), Sheba Ridge (SR) with
their intervening Alula-Fartak Transform (AFT), Carlsberg Ridge (CR) and Owen Fracture Zone (OFZ). Exact nature of ASTJ is
presently debated: whether it is RRF (ridge-ridge-fault) or RRR (ridge-ridge-ridge) type. A revised seismicity map for ASTJ
is given here using data for a period little more than a century. “Point density spatial statistical criterion” is applied
to short-listed 742 earthquakes (mb ≥ 4.3), 10 numbers of spatio-temporal seismic clusters are identified for ASTJ and its
arms. Relocated hypocentres help better constraining the cluster identification wherever such data exist. Seismic clusters
actually diagnose the most intense zones of strain accumulation due to far field as well as the local stress operating at
ASTJ. An earthquake swarm emanating from a prominent seismic cluster below SR provides an opportunity to investigate the pore
pressure diffusion process (due to the active source) by means of “r-t plot”. Stress and faulting pattern in the active zones
are deduced from 43 CMT solutions. While normal or lateral faulting is characteristic for these arms, an anomalous thrust
earthquake occurs in the triangular ‘Wheatley Deep’ deformation zone proximal to ASTJ. The latter appears to have formed due
to a shift of the deformational front from OFZ towards a transform that offsets SR. Though ASTJ is still in the process of
evolution, available data favour that this RRF triple junction may eventually be converted to a more stable RRR type. 相似文献