首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   54篇
  免费   3篇
  国内免费   1篇
测绘学   2篇
大气科学   1篇
地球物理   19篇
地质学   22篇
海洋学   3篇
天文学   4篇
综合类   3篇
自然地理   4篇
  2023年   2篇
  2022年   2篇
  2018年   6篇
  2017年   7篇
  2016年   6篇
  2015年   1篇
  2014年   5篇
  2013年   6篇
  2012年   3篇
  2011年   3篇
  2010年   3篇
  2009年   5篇
  2008年   1篇
  2006年   2篇
  2002年   1篇
  1991年   1篇
  1989年   1篇
  1983年   2篇
  1982年   1篇
排序方式: 共有58条查询结果,搜索用时 0 毫秒
1.
In laboratory investigations with model waters, the behaviour of selected cation-exchange resins (Amberlite 200 C, Duolite C-25, Lewatit S-100, Wofatit KPS and Wofatit KS-10) is tested. The usable volume capacity of the resins in the forms of H, Na and NH4 as well as the water content and the total volume capacity after 25 cycles of loading/regeneration are determined. It is recommended to use Amberlite 200 C and Wofatit KS-10.  相似文献   
2.
3.
Marine sediments from the Integrated Ocean Drilling Project (IODP) Site U1314 (56.36°N, 27.88°W), in the subpolar North Atlantic, were studied for their planktonic foraminifera, calcium carbonate content, and Neogloboqudrina pachyderma sinistral (sin.) δ13C records in order to reconstruct surface and intermediate conditions in this region during the Mid‐Pleistocene Transition (MPT). Variations in the palaeoceanography and regional dynamics of the Arctic Front were estimated by comparing CaCO3 content, planktonic foraminiferal species abundances, carbon isotopes and ice‐rafted debris (IRD) data from Site U1314 with published data from other North Atlantic sites. Site U1314 exhibited high abundances of the polar planktonic foraminifera N. pachyderma sin. and low CaCO3 content until Marine Isotope Stage (MIS) 26, indicating a relatively southeastward position of the Arctic Front (AF) and penetration of colder and low‐salinity surface arctic water‐masses. Changing conditions after MIS 25, with oscillations in the position of the AF, caused an increase in the northward export of the warmer North Atlantic Current (NAC), indicated by greater abundances of non‐polar planktonic foraminifera and higher CaCO3. The N. pachyderma sin. δ13C data indicate good ventilation of the upper part of the intermediate water layer in the eastern North Atlantic during both glacial and interglacial stages, except during Terminations 24/23, 22/21 and 20/1. In addition, for N. pachyderma (sin.) we distinguished two morphotypes: non‐encrusted and heavily encrusted test. Results indicate that increases in the encrusted morphotype and lower planktonic foraminiferal diversity are related to the intensification of glacial conditions (lower sea‐surface temperatures, sea‐ice formation) during MIS 22 and 20.  相似文献   
4.
The paper presents the testing of the possibility of determining the heights of GPS points in the homogeneous field in the new Croatian Height Reference System (HVRS71) by using the method of height transformation. The testing was made in the area of Zagreb. As part of the field works, normal orthometric heights of 27 GPS points were determined according to the new height system, by transferring the benchmark heights using the geometric levelling method, thus obtaining GPS/levelling points of known ellipsoidal and normal orthometric heights. The GPS/levelling points served as the basis for determining the transformation models that enabled the computation of normal orthometric heights from ellipsoidal heights of any GPS point in the observed area. The empirical data used for modelling were reduced undulation dN values of GPS/levelling points. As part of the dN modelling with parametric functions, the approximation surfaces were obtained on the basis of three polynomials: FN310, FN312 and FN318. The transformation models were also tested using non-parametric Watson and Loess algorithms. The FN318 and Loess models yielded the best results.  相似文献   
5.
Izvestiya, Physics of the Solid Earth - Abstract—When solving direct and inverse problems of magnetotellurics, magnetic permeability throughout model medium is conventionally assumed to be...  相似文献   
6.
Spatially-explicit estimation of aboveground biomass(AGB) plays an important role to generate action policies focused in climate change mitigation,since carbon(C) retained in the biomass is vital for regulating Earth’s temperature.This work estimates AGB using both chlorophyll(red,near infrared) and moisture(middle infrared) based normalized vegetation indices constructed with MCD43A4 MODerate-resolution Imaging Spectroradiometer(MODIS) and MOD44B vegetation continuous fields(VCF) data.The study area is located in San Luis Potosí,Mexico,a region that comprises a part of the upper limit of the intertropical zone.AGB estimations were made using both individual tree data from the National Forest Inventory of Mexico and allometric equations reported in scientific literature.Linear and nonlinear(expo-nential) models were fitted to find their predictive potential when using satellite spectral data as explanatory variables.Highly-significant correlations(p = 0.01) were found between all the explaining variables tested.NDVI62,linked to chlorophyll content and moisture stress,showed the highest correlation.The best model(nonlinear) showed an index of fit(Pseudo-r2) equal to 0.77 and a root mean square error equal to 26.00 Mg/ha using NDVI62 and VCF as explanatory variables.Validation correlation coefficients were similar for both models:lin-ear(r = 0.87**) and nonlinear(r = 0.86**).  相似文献   
7.
The paper presents the results of 2D inversion of deep magnetotelluric (MT) and magnetovariational (MV) soundings along the Naryn Line. The method of partial (sequential) inversions is used. According to this method, at the first stage, magnetovariation responses are used for the localization of deep anomalies of electrical conductivity, and then the magnetotelluric sounding data are invoked to refine the structure of the host medium and the structural details in the upper part of the section. It is shown that this approach enables one to estimate the informativeness of separate components of the electromagnetic field, to reduce the distorting influence of the near-surface geoelectric inhomogeneities, and to increase the stability of the final solution of the inverse problem.  相似文献   
8.
Enhanced oil recovery based on CO2 injection is expected to increase recovery from Croatian oil fields. Large quantities of CO2 are generated during hydrocarbon processing produced from gas and gas condensate fields situated in the north-western part of Croatia. First CO2 injection project will be implemented on the Ivani? Oil Field. Numerical modelling based on Upper Miocene sandstone core samples testing results have shown the decrease of oil viscosity during CO2 injection. Some of the characteristics of the testing samples are porosity 21.5–23.6 %, permeability 14–80 × 10?15 m2 and initial water saturation 28–38.5 %. Water alternating foam (WAF) and water alternating gas (WAG) simulations have provided satisfactory results. The WAF injection process has provided better results, but due to the process sensitivity and costs WAG is recommended for future application. During the pilot project 16 × 106 m3 CO2 and 5 × 104 m3 of water were injected. Additional amounts of hydrocarbons (4,440 m3 of oil and 2.26 × 106 m3 of gas) were produced which confirmed injection of CO2 as a successful tertiary oil recovery mechanism in Upper Miocene sandstone reservoirs in the Croatian part of the Pannonian Basin System.  相似文献   
9.
10.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号