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701.
Application of an Improved Flow-Stress-Damage Model to the Criticality Assessment of Water Inrush in a Mine: a Case Study 总被引:1,自引:0,他引:1
H. Q. Zhang Y. N. He C. A. Tang Bashir Ahmad L. J. Han 《Rock Mechanics and Rock Engineering》2009,42(6):911-930
This paper presents a case study of water inrush on a mine working face from roof strata. The flow-rock failure process analysis
(F-RFPA2D) code with an improved flow-stress-damage (FSD) model was adopted to perform the failure and coupling analysis. The improved
FSD model was used to represent the permeability variation at the four stages (elastic, damaged, cracked, and crack closure)
of the rock failure process. The fracture initiation, propagation, and coalescence in the stressed strata and the seepage
field evolution in the stress field are represented visually during the whole process of water inrush. The failure zone with
high permeability induced by mining disturbance becomes the water-conducting zone after full excavation of the coal seam.
The height of the water-conducting zone obtained in this study is in reasonable accordance with that predicted by an empirical
formula. It is definitely clarified that the water inrush from the roof strata is induced by the failure zone full of vertical
coalesced mine fractures. It is unlikely that roof accidents resulting in water inrush would occur if the water-conducting
zone does not grow upwards into the aquifer. The main task for mine extraction under a confined aquifer is to locate the aquifer
and find the maximum height of the water-conducting zone, which is very important for mine construction and support design. 相似文献
702.
703.
Muhammad Sadiq Carl C. Tscherning Zulfiqar Ahmad 《Studia Geophysica et Geodaetica》2009,53(3):375-388
This paper deals with the analysis of gravity anomaly and precise levelling in conjunction with GPS-Levelling data for the
computation of a gravimetric geoid and an estimate of the height system bias parameter No for the vertical datum in Pakistan by means of least squares collocation technique. The long term objective is to obtain
a regional geoid (or quasi-geoid) modeling using a combination of local data with a high degree and order Earth gravity model
(EGM) and to determine a bias (if there is one) with respect to a global mean sea surface. An application of collocation with
the optimal covariance parameters has facilitated to achieve gravimetric height anomalies in a global geocentric datum. Residual
terrain modeling (RTM) technique has been used in combination with the EGM96 for the reduction and smoothing of the gravity
data. A value for the bias parameter No has been estimated with reference to the local GPS-Levelling datum that appears to be 0.705 m with 0.07 m mean square error.
The gravimetric height anomalies were compared with height anomalies obtained from GPS-Levelling stations using least square
collocation with and without bias adjustment. The bias adjustment minimizes the difference between the gravimetric height
anomalies with respect to residual GPS-Levelling data and the standard deviation of the differences drops from 35 cm to 2.6
cm. The results of this study suggest that No adjustment may be a good alternative for the fitting of the final gravimetric geoid as is generally done when using FFT methods. 相似文献
704.
S. M. Ahmad D. J. Patil P. S. Rao B. N. Nath B. R. Rao G. Rajagopalan 《Journal of Earth System Science》2000,109(1):153-156
Stable carbon and oxygen isotopic analyses of the planktonic foraminifera (Globigerinoides ruber) from a deep sea sediment core (GC-1) in the Andaman Sea show high glacial-to-Holocene δ18O amplitude of 2.1%o which is consistent with previously published records from this marginal basin and suggest increased
salinity and/or decreased temperature in the glacial surface waters of this region. A pulse of18O enrichment during the last deglaciation can be attributed to a Younger Dryas cooling event and/or to a sudden decrease of
fresh water influx from the Irrawady and Salween rivers into the Andaman Sea. High δ13C values observed during the isotopic stages 2 and 4 are probably due to the enhanced productivity during glacial times in
the Andaman Sea. 相似文献
705.
S. K. Chaulya M. K. Chakraborty M. Ahmad K. K. K. Singh R. S. Singh B. K. Tewary P. K. Gupta 《Environmental Geology》2000,39(10):1155-1162
A study has been conducted at the Bicholim iron-ore mine, North Goa, India to investigate the hydrogeological continuity
between the mine's open pit and surrounding villages. Water resource accounting by demarcating different watersheds has also
been carried out to analyse the major causes of groundwater scarcity in the region during dry periods. A resistivity survey
and a ground penetrating radar survey were completed around the periphery of open pits, the surrounding village areas and
Mayem Lake. The results of the two independent surveys and other related data confirm that there is no observable hydrogeological
continuity between the pits, nearby villages and Mayem Lake. Hence, there may not be any significant effect on surrounding
water resources due to mining or mine dewatering. Water resource accounting has revealed that only 15–20% of 3500 mm precipitation
per annum becomes part of the groundwater resource. The remainder of the annual precipitation is lost as heavy runoff, evapotranspiration
and subsurface capillary moisture. Closely spaced wells in the region have also aggravated the groundwater scarcity problem
due to draw down effects. Therefore, an effective water resource conservation plan is required for the region to overcome
the problem.
Received: 18 January 1999 · Accepted: 17 May 1999 相似文献
706.
Kohistan Sequence has been considered as island arc formed during the subduction of oceanic lithosphere at the leading edge of northward moving Indian continent.. Sedimentary sequences indicate that formation of the intra\|oceanic Kohistan arc began in early Cretaceous time. The isotopic data demonstrate the involvement of enriched, DUPAL type mantle, suggesting that Kohistan arc was formed at or south of the present equator (Khan et al., 1997). The Intra oceanic phase of Kohistan lasted until sometime between 102 and 85 Ma, when Kohistan collided with Asia. From this time until collision with India about 50 Ma ago, Kohistan existed as Andean\|type margin. This paleomagnetic study is from the volcanic and plutonic rocks exposed in Gupis\|Shamran area (west of Gilgit) in northern part of the Kohistan arc. According to geochronological data these rocks were formed 61~55Ma ago (Treloar et al., 1989), when Kohistan was existing as Andean\|type margin. Seven to nine samples were collected from nine sites of Shamran volcanics (58±1)Ma and from five sites of Pingal, Gupis, and Yasin plutons (Ar\|Ar hornblende ages ranges from 61~52Ma). On the basis of one Rb\|Sr age of (59±2)Ma from these plutons, the above\|mentioned Ar/Ar ages may be regarded as reasonable intrusion ages of these plutons (Searle, 1991). 相似文献
707.
708.
709.
710.