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261.
262.
Linear anisotropic elasticity has been applied to interpret the dislocation stability and ease of slip in wadsleyite. It
is shown that wadsleyite is very isotropic from the elastic point of view. The influence of crystal chemistry and bonding
on the choice of the slip plane is discussed. It is shown that slip is predominantly achieved on planes that do not shear
Si–O bonds. It is suggested that dissociation of dislocations is essential in determining the ease of slip among the various
slip systems.
Received: 15 July 2002 / Accepted: 14 February 2003
Acknowledgements High-pressure experiments were performed at the Bayerisches Geoinstitut under the EU IHP – Access to Research Infrastructures
Programme (Contract no. HPRI-1999-CT-00004 to D.C. Rubie). Enlightening discussions with A. Coujou and J. Rabier are gratefully
acknowledged. 相似文献
263.
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The Influence of pH and Calcium Concentration on Metal-Fulvic Acid Bonds – Stripping Voltammetric and Chemometric Investigations. Electrochemically available metal concentrations of Cd, Cu and Zn were analyzed in dependence of different concentrations of calcium, fulvic acids and pH by Differential Pulse Anodic Stripping Voltammetry (DPASV). A statistical experimental design was the base to minimize the number of experiments and to include the multifarious interactions between the independent variables (Ca concentration, concentration of fulvic acids and the pH value) and otherwise the electrochemically available metal concentrations of Cd, Cu and Zn. At first analysis of experimental data was carried out by multiple linear regression. The main influence on available metal concentrations is the pH value especially for Cu. The Ca ion influence has not competitive effect and is only significant for Cd and Cu. It has an effect on the metal-fulvic acid-bonds. Two factor interactions exist for pH/fulvic acids and for Ca/fulvic acids too. The partial least squares regression (PLS) model was used to include the interactions between the metals Cd, Cu and Zn. For proving these two models the three parameters pH, Ca and fulvic acid were varied within the calibration range of the models and predicted values were compared with the experimental values. The approach with the PLS model is better than the approach with the multiple linear regression (normally used mathematical method of analysis of a factorial plan) with a relative error of 9.7% for modelling of Cd, 6.0% for Zn and 58% for Cu in relation to multiple linear regression with errors of 12% for Cd, 8.6% for Zn and 65% for Cu. The PLS modelling is a suited tool for modelling chemical interactions also in simulated natural matrices. 相似文献
266.
Matiu Prebble Marc Schallenberg John Carter James Shulmeister 《Journal of Paleolimnology》2002,27(4):393-413
An analysis of modern phytolith assemblages is presented.Phytolith assemblages were studied in modern surface soils and sediments of 28sites from east Otago, New Zealand, within a range of vegetation types andmicroclimates. No simple distinction could be made between vegetation types onthe basis of phytolith assemblage composition. A Principal Components Analysis(PCA) of the phytolith data set revealed that festucoid, chloridoid andspherical phytolith morphotypes formed strong associations with sites fromwetland, grassland, and forest vegetation types, respectively. Moreimportantly, a comparison of sample replicates from each field site using Squared ChordDistance (SCD) assemblage analysis showed that wetland and grassland sitestended to produce more internally consistent phytolith assemblages than forestsites. Environmental variables including pH, conductivity, altitude,precipitation and temperature were also gathered for each site. The ability ofeach environmental variable to reflect variance in the entire phytolithdata set was estimated by a series of Redundancy Analyses (RDA) with MonteCarlo permutation tests of statistical significance. After a forward selectionprocess, transfer functions were generated using Partial Least Squares (PLS)regression and calibration with jack-knife validation. The final transferfunctions have root mean squared errors of prediction for pH (0.47), logconductivity (0.38 S cm), average annual precipitation (63mm), and average annual (0.28 °C), spring (0.38 °C) andautumn temperature (0.41 °C); the smallest group of environmental variablesexplaining the most variance in the modern phytolith data set. The most usefultransfer functions for application to fossil phytolith data andpaleoenvironmental interpretation are pH, log conductivity and annualprecipitation. The relationship between changes in pH and annual precipitationand phytolith assemblage composition found in this study presents aprima facie relationship with the potential to providedirect proxies for soil weathering and indirectly for paleoenvironmentalreconstruction. 相似文献
267.
线阵探测器(LDA)的现状及发展趋势 总被引:7,自引:1,他引:7
本文概述了当前的线阵探测器(LDA)技术及未来发展,同时详细说明了LDA的重要性能特征,并对不同应用下不同的阵列设计进行了讨论。目前芬兰探测技术公司已将该项技术成功应用于大型集装箱检测系统,工业CT,医用CT,L型双能探测器等工业医学应用中. 相似文献
268.
269.
Rock cut stability assessment in mountainous regions 总被引:1,自引:0,他引:1
Gorka Uribe-Etxebarria Tomás Morales Jesús A. Uriarte Valentín Ibarra 《Environmental Geology》2005,48(8):1002-1013
Ensuring stability of rock slopes is an essential requirement in the progress of our societies today. Rock determined to be
loose or with potential for failure must be removed or restrained in some way. In our work, after doing an inventory of the
instabilities that occurred in the last 5 years in the Basque Country, we analyse the different factors, in slope stability.
The potential for failure is evaluated for different classes of rock mass, characterized previously by their geomechanical
properties. The characterization of potential risk of each one is undertaken by considering 10 parameters that define the
nature of mass rock, relative orientation and morphological features of the slope (interaction rock massif-slope) and infrastructure
features (interaction rock massif-slope-infrastructure). Each of these parameters is evaluated separately and a Risk Factor
(RF) is determined. The RF reaches a maximum value of 10,000 and allows to differentiate four categories of slopes; each category
has its own priority. Rock mass characteristics also determine the potential damage from instability and the associated correction
measures. The systematic evaluation of instabilities must allow establishing a priority in the correction measures and thus
optimise the available economic resources. 相似文献
270.
在应用最优分割法对地震活动性分类研究的基础上引进线性模型,扩大最优分割法在地震活动性分类中的应用范围,并将聚类问题与建模问题有机地结合起来,以揭示地震活动的某种内在规律,这对于探索地震预报和地震的发生规律有一定实际意义。 相似文献