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271.
272.
The accuracy of automatic procedures for locating earthquakes is influenced by several factors such as errors in picking seismic phases, network geometry, modeling errors and velocity model uncertainties. The main purpose of this work is to improve the performances of the automatic procedure employed for the “quasi-real-time” location of seismic events in North Western Italy by developing a procedure based on a waveform similarity analysis and by using only one seismic station.To detect “earthquake families” a cross-correlation technique was applied to a data set of seismic waveforms recorded in the period 1985-2002, in a small test area (1600 km2) located in the South Western Alps (Italy). Normalized cross-correlation matrices were calculated using about 2700 seismic events, selected on the basis of the signal to noise ratio, manually picked and located by using the Hypoellipse code. The waveform similarity analysis, based on the bridging technique, allowed grouping about 65% of the selected events into 80 earthquake families (multiplets) located inside the area considered. For each earthquake family a master event is selected, manually re-picked and re-located by using Hypoellipse code. Having chosen a reference station (STV) on the basis of the completeness of the available data set, an automatic procedure has been developed with the aim of cross-correlating new seismic recordings (automatically picked) to the waveforms of the events belonging to the detected families. If the new event is proved to belong to a family (on the basis of the cross-correlation values), its hypocenter co-ordinates are defined by the location of the master event of the associated family. The performance of the proposed procedure is tested and demonstrated using a data set of 104 selected earthquakes recorded in the period January 2003-June 2004 and located in the test area. The automatic procedure is able to locate, associating events with the multiplets detected by the waveform similarity analysis, about 50% of the test events, almost independently of the accuracy of the automatic phase picker and without the biasing of the network geometry and of the velocity model uncertainties. 相似文献
273.
Seismic response of a lightly reinforced stiff shear‐wall structure subjected to ground motions grouped as near‐ or far‐field according to their distance to causative faults is investigated. A model structure that had earlier been studied both experimentally and analytically in the context of a co‐ordinated research project is re‐examined. The structure is a five‐storey lightly reinforced shear‐wall model subjected analytically to 55 ground motion records from firm soil sites. Several response parameters are obtained by linear and non‐linear analyses. Additional analyses are performed to ascertain the validity and range of applicability of current approximate displacement‐based analysis procedures. The procedures considered in this study are found to be inadequate in representing the anticipated response of the structure employed here regardless of the type of excitation, so modifications are suggested for improved results. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
274.
275.
Mahendra P. Verma 《Geostandards and Geoanalytical Research》2004,28(3):391-409
A statistical evaluation of the results of HCO3‐ determinations in geothermal waters during the interlaboratory comparison programmes of the International Association of Geochemistry and Cosmochemistry (IAGC) and International Atomic Energy Agency (IAEA) indicated that the analytical uncertainty increases with decreasing concentration of HCO3‐ and was ? 25% for 50 μg ml‐1 and ? 60% for 25 μg ml‐1 of HCO3‐. The analytical method (Method 1) used by chemists and hydrologists works well for waters containing carbonic alkalinity, whereas Method 2 used by geochemists is conceptually incorrect. A stepwise comparison between the theoretical and experimental titration results for a given concentration Na2CO3 (0.0988 mol l‐1) solution was performed to understand the limitations of the titration method for geothermal water analysis. Backward titration from the carbonic acid equivalence point (H2CO3EP) to the original pH after CO2 removal, as had been practised earlier in the geothermal industry, in order to estimate the contribution of silicic and boric alkalinities to the total alkalinity, is incorrect because the amount of standard base (NaOH) added is equivalent to silicic and boric alkalinities plus some OH‐ alkalinity. In a Na2CO3 solution, the added NaOH is equivalent to OH‐ alkalinity only. Backward titration is only needed from the forward titration end point to the H2CO3EP in order to correct the total alkalinity for the excess of standard acid (HCl) added during the forward titration. In the case of a Na2CO3 solution, the H2CO3EP, after removal of CO2 during the forward titration, is at pH = 7, not at pH = 4.5 (3.8) as has been considered in literature. Similarly, the liberation of CO2 during titration occurs well before the point expected theoretically and it is less for shorter titration time. The revised procedure for the determination of carbonic species concentration is presented and illustrated for a water sample from Alchichica Lake, Puebla, Mexico. 相似文献
276.
海底沉积物中碳酸钙分析方法的研究 总被引:4,自引:0,他引:4
探讨了海底沉积物中CaCO3的测定方法。用1mol/LNaAc+HAc做碳酸盐相+离子交换相的浸取剂,1mol/LNaAc做离子交换相的浸取液,在沸水浴中30min分解样品,然后用AAS或ICPAES分别测定离子交换相+碳酸盐相及离子交换相中的Ca,差减法计算样品中CaCO3含量。方法经深海沉积物、水系沉积物等国家标准物质验证,结果与标准值相符。对同一样品进行12次测定,相对标准偏差小于5%。 相似文献
277.
278.
泌阳断陷陡坡带陆相层序发育的可容空间图解探讨 总被引:9,自引:1,他引:8
泌阳断陷湖盆基底构造沉降为非线性函数或间断函数,且呈“反铰链式”沉降。在湖平面变化和构造沉降共同作用下,泌阳断陷湖盆陡坡带的可容空间变化仅有三种可能性:a.南缘及北缘减小,中央带增加;b.南缘不变,中央带及北缘增加;c.南缘、中央带及北缘均增加。针对这三种情况,分别在不同的物源供给速率条件下,分析了断陷湖盆陡坡带不同构造部位的剩余可容空间变化规律及其相应沉积特征。文中以泌阳断陷双河-赵凹地区为例,探讨了参照井选择的可容空间机理,对下第三系核三一段的陆相层序进行了划分,建立了其等时层序框架模式。 相似文献
279.
The performance‐based philosophy has been accepted as a more reasonable design concept for engineering structures. For this purpose, capacity evaluation and demand prediction procedures for civil engineering structures under earthquake excitations are of great significance. This work presents a displacement‐based seismic performance verification procedure including capacity and seismic demand predictions for steel arch bridges and investigates its applicability. Pushover analyses is employed as a basis in this method to investigate the structure's behaviors. A failure criterion for steel members accounting for the effect of local buckling is involved and an equivalent single‐degree‐of‐freedom (ESDOF) system with a simplified bilinear hysteretic model formulated using pushover analyses results is introduced to estimate the displacement capacity and maximum demand of steel arch bridges under major earthquakes. To check the accuracy of the proposed method, seismic capacities and demands from multi‐degree‐of‐freedom (MDOF) time‐history analyses with Level‐II design earthquake record inputs modeling major earthquakes are used as benchmarks for comparison. By a case study, it is clarified that the proposed prediction procedure can give accurate estimations of displacement capacities and demands of the steel arch bridge in the transverse direction, while insufficient for the longitudinal direction, which confirms the conclusion drawn in other structure types about the applicability of pushover analyses. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
280.
金融地理学视角下的证券市场投资潜力分析 总被引:4,自引:0,他引:4
本文从金融地理学的全新视角,采用2001年全年的数据,用实证的方法,对全国31个省、自治区、直辖市的证券市场投资潜力进行了分析预测、通过建立模型,得出不同地域的证券投资发展潜力,并在此基础上进行了聚类分析,将全国31个地区分为七类,揭示了区域金融发展的块状结构。鉴于金融地理学在国内研究的薄弱局面,本文对运用新兴边缘学科——金融地理学进行实际经济问题的数量分析做出了初步尝试。 相似文献