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81.
Paula Lindgren Martin R. Lee Mahmood R. Sofe Michael E. Zolensky 《Meteoritics & planetary science》2013,48(6):1074-1090
Clasts in the CM2 carbonaceous chondrite Lonewolf Nunataks (LON) 94101 have been characterized using scanning and transmission electron microscopy and electron microprobe analysis to determine their degrees of aqueous alteration, and the timing of alteration relative to incorporation of clasts into the host. The provenance of the clasts, and the mechanism by which they were incorporated and mixed with their host material are also considered. Results show that at least five distinct types of clasts occur in LON 94101, of which four have been aqueously altered to various degrees and one is largely anhydrous. The fact that they have had different alteration histories implies that the main part of aqueous activity occurred prior to the mixing and assimilation of the clasts with their host. Further, the presence of such a variety of clasts suggests complex mixing in a dynamic environment involving material from various sources. Two of the clasts, one containing approximately 46 vol% carbonate and the other featuring crystals of pyrrhotite up to approximately 1 mm in size, are examples of unusual lithologies and indicate concentration of chemical elements in discrete areas of the parent body(ies), possibly by flow of aqueous solutions. 相似文献
82.
伊朗锡斯坦地区沙漠灾害区划(英文) 总被引:1,自引:1,他引:0
Desertification process as a great problem affects most of the countries in the world.This process has a high rate in arid and semiarid areas.Today,human societies are encountering the desertification phenomenon as a serious problem which causes various irreparable damages to economic and social sectors.In order to assess desertification results in production of different regional models for their application in another region the indices should be re-investigated and adjusted to local conditions.Several models have been developed for desertification evaluation.The present study,attempts to assess quantitatively the desertification process has in an area located at Sistan plain of Iran(Niatak region as a case study) by using Modified MEDALUS method.The obtained results indicated that of the whole studied region(comprising 4819.6 acres),2651.56 acres(55%) are located in medium desertification intensity class,1269.48 acres(26.34%) are positioned in severe desertification intensity class,and 898.54 acres(18.64%) are placed in vary severe desertification intensity class. 相似文献
83.
Mohammadreza Gharibreza Mohammad Zaman Mahmood Arabkhedri Shahriar Sobh-Zahedi 《国际泥沙研究》2022,37(3):370-382
Abkenar open water(AOW)has a 35 km2distribution and is the largest part of the Anzali Lagoon in the southern coastal zone of the Caspian Sea.The effects of deforestation in the upstream basin of the AOW were assessed by measuring the rate of sedimentation,sediment contamination,and ecological risk for aquatic life and end-users using radioisotopes Cesium-137 and Lead-210.The chronology of the AOW sediment column was studied using the Constant Rate of Supply model.Correlations between environmental changes and the sedimentary regime of the study area highlight the contribution of the AOW authorized international and local wood harvesting companies pre-and-post 1950 in the catchment in terms of the rate of sediment supply and the influx of toxic metals.Historical evidence shows that two specific layers formed during World Wars I and II with the mean rates of 0.185±0.04(±STD)and 0.32±0.02 kg/(m2·y),respectively.The highest influx of alkali elements and toxic metals(nickel,cadmium,lead,zinc,and copper)into the basin occurred in 1945.Two layers of gray mud(16-50 cm)and organic-rich dark loss mud(0-16 cm)correlated well with the programmed wood harvesting projects.These layers accumulated from 1953 to 2000 with a mean rate of 0.6±0.2 and 2±0.7 kg/(m2·y).Thus,aquatic life and end-users have been exposed to moderate to extremely high levels of toxic metals and a moderate level of contamination since the 1950s. 相似文献
84.
Mureed Hussain Nisar Ahmed Wang Yan Chun Perveiz Khalid Azhar Mahmood Sajid Rashid Ahmad Umair Rasool 《Journal of the Geological Society of India》2017,89(3):331-338
The lower Indus basin is one of the largest hydrocarbon producing sedimentary basins in Pakistan. It is characterized by the presence of many hydrocarbon-bearing fields including clastic and carbonates proven reservoirs from the Cretaceous to the Eocene age. This study has been carried out in the Sanghar oil field to evaluate the hydrocarbon prospects of basal sand zone of lower Goru Formation of Cretaceous by using complete suite of geophysical logs of different wells. The analytical formation evaluation by using petrophysical studies and neutron-density crossplots unveils that litho-facies mainly comprising of sandstone. The hydrocarbons potentialities of the formation zone have been characterized through various isoparameteric maps such as gross reservoir and net pay thickness, net-to-gross ratio, total and effective porosity, shaliness, and water and hydrocarbons saturation. The evaluated petrophysical studies show that the reservoir has net pay zone of thickness range 5 to 10 m, net-togross ratio range of 0.17 to 0.75, effective porosity range of 07 to 12 %, shaliness range of 27 to 40 % and hydrocarbon saturation range of 12 to 31 %. However, in the net pay zone hydrocarbon saturation reaches up to 95%. The isoparametric charts of petrophysically derived parameters reveal the aerial distribution of hydrocarbons accumulation in basal sand unit of the lower Goru Formation which may be helpful for further exploration. 相似文献
85.
Muhammad Imran Ashraf Na Li Xiaori Han Jinfeng Yang Yue Wang Shumao Fan Muhammad Irshad Qaisar Mahmood 《Arabian Journal of Geosciences》2017,10(13):289
In agricultural production, specific elements in soil and plants are very important for the soil quality and plant productivity. Trace elements and rare earth elements enter in agri-environment by the application of fertilizers and, through anthropogenic activities, pose important health impacts even at low concentration due to non-biodegradable nature with long half-life. The micro nutrients are essential for human body in a quantity most of less than 100 mg/day. The nutritional element uptake by plants is regulated by availability of the required elements and element accumulation ability of the plants. Therefore, this study was aimed to investigate the accumulation of trace and rare earth elements after long-term application of different fertilizers in soil and soybean uptake. The inorganic fertilizers (NKP) and pig manure were applied to maize-maize-soybean rotation in Alfisols (brown) soil since 1979. Atomic emission spectrometry along with inductively coupled plasma technique was applied to determine trace and rare earth elements. The accumulation pattern of trace elements (TEs) observed in soil was Ni > Co > Se > Mo and rare earth elements (REEs) was found as La > Nd > Tb > Y > Pr > Gd > Er > Yb > Lu. In soybean stem, the TE and REE concentrations were Se > Ni > Co > Mo and Pr > Gd > Er > Yb > Tb > Nd > Lu > La > Y, respectively. Elemental concentrations in the seed samples were Ni > Se > Mo > Co and Pr > Gd > Er > Yb > Tb > Nd > Lu > Y > La. The seed of soybean accumulated Co, Mo, Ni, Gd, Pr, Er, Lu, and Tb more than the stem. Higher concentrations of Se, Nd, Y, and Yb were found in soil. These elements were higher in soybean stem followed by the seed. However, these elements are within safe toxic level and light pollution level. 相似文献
86.
Fluvial depositional systems constitute diverse host for the hydrocarbons all over the globe. Nevertheless, predicting the hydrocarbon sands within these assorted sand systems is a challenge for the prospect generation. We apply the continuous wavelet transform of spectral decomposition technique to a 3D seismic data of the Miano Gas Field in the Indus Platform, Pakistan. Full spectrum seismic attributes like the amplitude and root mean square (RMS) detect the reservoir sands down to a restricted reservoir compartment. Nonetheless, the continuous wavelet transforms can be advantageous in imaging and enactment of these clastic reservoirs within the whole reservoir zone. Rock physics reveal high-quality reservoir with an average porosity ~25% together with the discrimination of lithology/fluids, signifying the bright chances for ascertaining the potential stratigraphic reservoirs. 相似文献
87.
Mohsin Muhammad Mu Yongtong Memon Aamir Mahmood Kalhoro Muhammad Talib Shah Syed Baber Hussain 《中国海洋湖沼学报》2017,35(4):936-946
Pakistani marine waters are under an open access regime.Due to poor management and policy implications,blind fishing is continued which may result in ecological as well as economic losses.Thus,it is of utmost importance to estimate fishery resources before harvesting.In this study,catch and effort data,1996-2009,of Kiddi shrimp Parapenaeopsis stylifera fishery from Pakistani marine waters was analyzed by using specialized fishery software in order to know fishery stock status of this commercially important shrimp.Maximum,minimum and average capture production of P.stylifera was observed as 15 912 metric tons(mt)(1997),9 438 mt(2009) and 11 667 mt/a.Two stock assessment tools viz.CEDA(catch and effort data analysis) and ASPIC(a stock production model incorporating covariates) were used to compute MSY(maximum sustainable yield) of this organism.In CEDA,three surplus production models,Fox,Schaefer and Pella-Tomlinson,along with three error assumptions,log,log normal and gamma,were used.For initial proportion(IP) 0.8,the Fox model computed MSY as 6 858 mt(CV=0.204,R~2=0.709) and 7 384 mt(CV=0.149,R~2=0.72) for log and log normal error assumption respectively.Here,gamma error produced minimization failure.Estimated MSY by using Schaefer and Pella-Tomlinson models remained the same for log,log normal and gamma error assumptions i.e.7 083 mt,8 209 mt and 7 242 mt correspondingly.The Schafer results showed highest goodness of fit R~2(0.712) values.ASPIC computed MSY,CV,R~2,F_(MSY)and B_(MSY) parameters for the Fox model as 7 219 mt,0.142,0.872,0.111 and 65 280,while for the Logistic model the computed values remained 7 720 mt,0.148,0.868,0.107 and 72 110 correspondingly.Results obtained have shown that P.stylifera has been overexploited.Immediate steps are needed to conserve this fishery resource for the future and research on other species of commercial importance is urgently needed. 相似文献
88.
Simulating sensitivity of soil moisture and evapotranspiration under heterogeneous soils and land uses 总被引:9,自引:0,他引:9
Soil moisture (SM) plays an important role in land surface and atmospheric interactions. It modifies energy balance at the surface and the rate of water cycling between the land and atmosphere. In this paper we provide a sensitivity assessment of SM and ET for heterogeneous soil physical properties and for three land uses including irrigated maize, rainfed maize, and grass at a climatological time-scale by using a water balance model. Not surprisingly, the study finds increased soil water content in the root zone throughout the year under irrigated farming. Soil water depletes to its lowest level under rainfed maize cultivation. We find a ‘land use’ effect as high as 36 percent of annual total evapotranspiration, under irrigated maize compared to rainfed maize and grass, respectively. Sensitivity analyses consisting of comparative simulations using the model show that soil characteristics, like water holding capacity, influence SM in the root zone and affect seasonal total ET estimates at the climatological time-scale. This ‘soils’ effect is smaller than the ‘land use’ effect associated with irrigation but, it is a source of consistent bias for both SM and ET estimates. The ‘climate’ effect basically masks the ‘soils’ effect under wet conditions. These results lead us to conclude that appropriate representation of land use, soils, and climate are necessary to accurately represent the water and energy balance in real landscapes. 相似文献
89.
M.Qaisar T.Mahmood S.A.Khan 《地震学报(英文版)》2003,16(1):59-66
The detectability and reliability analysis for the local seismic network is performed employing by Bungum and Husebye technique.The events were relocated using standard computer codes for hypocentral locations.The de-tectability levels are estimated from the twenty-five years of recorded data in terms of 50%,90%and 100% cumu-lative detectability threshokls,which were derived from frequency-magnitude distribution.From this analysis the 100%level of detectability of the network is ML=1.7 for events which occur within the network.The accuracy in hypocentral solutions of the network is investigated by considering the fixed real hypocenter within the network.The epicentral errors are found to be less than 4km then the events occur within the network.Finally.the prob-lems faced during continuous operation of the local network,which effects its detectability,are discussed. 相似文献
90.
利用Bungum和Husebye的方法,分析了地方地震台网的检测能力和可靠性.用标准的计算机定位程序重新测定了地震位置.根据25年的地震记录,分别由震级-频度关系导出的50%、90%和100%的累积检测率估计了检测水平.对台网内地震,相应于100%检测率的震级下限为ML=1.7.用台网内固定的实际震源,研究了台网对震源位置的测定精度.对网内地震,震中测定误差小于4 km.最后讨论了台网连续工作时可能会遇到的影响检测能力的一些问题. 相似文献