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981.
Jean-Louis Pinault 《地球物理与天体物理流体动力学》2016,110(6):518-528
The El Niño-Southern Oscillation (ENSO) is characterized based on the date the events are mature. Their time lag defined relative to the central value of successive intervals of 4 years length, e.g. 01/1868–01/1872, 01/1872–01/1876 …, 01/1996–01/2000 … affects their evolution and, for a given amplitude, their variability. It specifies the dynamics of the quadrennial Quasi-Stationary Wave (QSW) in the tropical Pacific since ENSO always occurs at the end of the eastward phase propagation of that QSW. A third of events are unlagged with very low variability, SST anomalies being nearly concomitant between the extreme eastern and the central-eastern Pacific. A third of events are weakly lagged, in phase with the annual QSW, whose variability is much greater. Several months may elapse between the maximum SST anomalies east of the basin and along its equatorial central part. The last third of the events exhibits considerable variability, whether they are out of phase with the annual QSW or strongly lagged. The SST anomaly between 5°N and 20°N plays a key role in the maturation of the events out of phase. The events in phase (10% of the total population) are characterized by a negative SST anomaly in the central-eastern Pacific that reverses just before the maturation stage of ENSO. Sea water temperature 125 m deep in the central-eastern Pacific carries the earliest relevant information with a lead time of one year for forecasting the amplitude of unlagged ENSO while reporting how SST anomalies will develop until ENSO is fully developed. Besides, long-term forecast of the resumption of La Niña can be achieved accurately when weakly lagged events in phase with the annual QSW occur. The well differentiated typology of events vs. their time lag is the best clue to prove the leading role of the quadrennial QSW in the genesis of ENSO, while the related dynamic of the atmosphere ensues. 相似文献
982.
使用断层附近两个数字地震台网记录的重复地震数据研究了发生2008年汶川M7.9灾难性地震的龙门山断裂带的深部滑动速率。通过波形互相关分析,识别出波形高度相似的231组相似地震对和224组多重相似对。大部分相似地震活动表现为非周期性,复发间隔从数分钟到数百天不等。针对每一组多重相似对,我们首先依据在同一地震台站记录的波形来塑造参考地震的波形,用以量取每个地震相对于参考地震的S与P波的相对到时差,并确定每个地震与多重相似对质心的相对距离,从而挑选出每组地震中的重复事件。我们识别出了位于M7.9汶川地震震源区的12组重复微震,大部分重复微震分布在2008汶川地震同震大破裂闭锁区的边缘,揭示了微震活动与未来破坏性大震在空间位置上的密切关系。由重复微震直接获取的滑动速率随深度增加而增大,在4~18km深度范围滑动速率为3.5~9.6mm/a,约为GPS和地质等浅表观测的滑动速率值的2倍。研究结果对于理解断层活动性和地震危险性分析具有重要意义。 相似文献
983.
984.
985.
986.
顺层岩质边坡地震动力响应研究 总被引:1,自引:0,他引:1
地震作用下边坡的动力响应研究是边坡动力稳定分析的基础,利用FLAC3D有限差分软件建立一个顺层岩质边坡动力数值模拟模型,对其在竖向和水平向地震耦合作用下的动力响应全过程进行研究。研究表明,地震竖向和水平向耦合作用模拟比简单的模拟水平向振动更加接近实际情况,对岩土体的破坏更大;顺层岩质边坡在耦合地震作用下存在垂直放大和临空面放大作用;坡面水平向和竖向加速度均随高程增加呈增大趋势,在结构面处增大特别明显;竖向地震波产生的水平与竖向拉裂是触发斜坡体产生初期崩滑破坏的主控因素;边坡动力响应特征值的放大效应表明,其放大系数值从大到小依次是:竖向加速度>水平加速度>竖向速度>水平速度;耦合地震波作用下,随着av /aH的增大,坡面监测各点横向位移基本呈增大趋势,说明竖向地震作用起了重要的破坏作用。 相似文献
987.
Francesca Leonori Enrico Segoloni Sébastien D. Le Picard 《Planetary and Space Science》2008,56(12):1658-1673
The reaction between dicarbon (C2) and acetylene was recently suggested as a possible competitive reaction in the atmospheres of Titan, Saturn and Uranus by rate constant measurements at very low temperatures [see Canosa, A., Páramo, A., Le Picard, S.D., Sims, I.R., 2007. An experimental study of the reaction kinetics of C2(X1Σg+) with hydrocarbons (CH4, C2H2, C2H4, C2H6 and C3H8) over the temperature range 24-300 K: implications for the atmospheres of Titan and the Giant Planets. Icarus 187, 558-568]. We have investigated the reaction of the two low lying electron states of C2 and acetylene by the crossed molecular beam (CMB) technique with mass spectrometric detection. C4H, already identified as a primary product in previous CMB experiments, is confirmed as such, even though the mechanism of formation is inferred to be partly different with respect to the previous study. An experimental setup has been devised to characterize the internal population of C2 and refine the interpretation of the scattering results. The implications for the modelling of the atmospheres of Giant Planets and Titan, as well as cometary comae and the interstellar medium, are discussed. 相似文献
988.
A. JAMBON O. BOUDOUMA M. FONTEILLES C. Le GUILLOU D. BADIA J.‐A. BARRAT 《Meteoritics & planetary science》2008,43(11):1783-1795
Abstract— Northwest Africa (NWA) 1670, contains olivines of up to 5 mm in size representing about 30% of the studied section. With subordinate clinopyroxene and chrome‐spinel microphenocrysts (0.2‐0.5 mm), they represent a xenocrystic association. Phenocrysts are surrounded by a groundmass, predominantly comprising bundles of plagioclase and clinopyroxene (typically 20 × 200 μm crystals). Olivine and kirschsteinite are present in the groundmass in lesser amounts. The olivine xenocrysts (Fo90) are significantly fractured and show mosaicism for their major part, the remaining showing faint undulatory extinction. They are surrounded with a rim of 100–200 μm zoned down to Fo80 and overgrown with serrated olivine, Fo80 to Fo60 (about 100 μm). Olivine in the groundmass is zoned from Mg# 0.55 to 0.15; its CaO content ranges 2.0 to 8.4%. Subcalcic kirschsteinite is zoned from Mg# 0.13 to 0.03, CaO increasing from 15.8 to 21.3%. Pyroxenes xenocrysts (Mg# = 0.77) are superseded in the groundmass by less magnesian pyroxenes, Mg# 0.61 to 0.17, with an average FeO/ MnO of 98. Their compositions range from En30 Fs22 Wo27 Al‐Ts28 Ti‐Ts2 to En2 Fs37 Wo22 Al‐Ts40 Ti‐Ts1. Anorthite microcrysts (An99‐100) are restricted to the groundmass. Accessories are pyrrhotite, kamacite, Ca‐phosphate, titanomagnetite, hercynite and Ca‐carbonate. The bulk chemical composition confirms that NWA 1670 corresponds to a normal angrite melt that incorporated olivine. High Mg olivine xenocrysts and the associated mineralogy are typical of angrites. We suggest that it is an impact melt with relict phenocrysts. The strong silica undersaturation, the presence of Fo90 olivine xenocrysts and carbonate support their derivation as melilite‐like melts in the presence of carbonate. 相似文献
989.
990.
Carlo?CauzziEmail author Yannik?Behr Thomas?Le?Guenan John?Douglas Samuel?Auclair Jochen?Woessner John?Clinton Stefan?Wiemer 《Bulletin of Earthquake Engineering》2016,14(9):2495-2512
Based on our experience in the project REAKT, we present a methodological framework to evaluate the potential benefits and costs of using earthquake early warning (EEW) and operational earthquake forecasting (OEF) for real-time mitigation of seismic risk at nuclear facilities. We focus on evaluating the reliability, significance and usefulness of the aforementioned real-time risk-mitigation tools and on the communication of real-time earthquake information to end-users. We find that EEW and OEF have significant potential for the reduction of seismic risk at nuclear plants, although much scientific research and testing is still necessary to optimise their operation for these sensitive and highly-regulated facilities. While our test bed was Switzerland, the methodology presented here is of general interest to the community of EEW researchers and end-users and its scope is significantly beyond its specific application within REAKT. 相似文献