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231.
Erik Swietlicki Jingchuan Zhou David S. Covert Kaarle Hämeri Bernhard Busch Minna Väkeva Ulrike Dusek Olle H. Berg Alfred Wiedensohler Pasi Aalto Jyrki Mäkelä Bengt G. Martinsson Giorgos Papaspiropoulos Besim Mentes Göran Frank Frank Stratmann 《Tellus. Series B, Chemical and physical meteorology》2000,52(2):201-227
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234.
Spatial heterogeneity and temporal stability of throughfall under individual Quercus brantii trees 下载免费PDF全文
Pedram Attarod Richard F. Keim Alfred Stein Ghavamudin Zahedi Amiri Ali Asghar Darvishsefat 《水文研究》2014,28(3):1124-1136
Spatio‐temporal patterns of throughfall (TF) have often been studied under forest canopies. Few reports, however, have been made on small‐scale TF variability in deciduous forest stands. In the present research, the spatial heterogeneity and temporal stability of TF under five individual persian oak trees (Quercus brantii var. Persica) was quantified. The research site was in the Zagros forests in western Iran, where mean annual precipitation and temperature are equal to 587.2 mm and 16.9 °C, respectively. Data from 23 rainfall events were aggregated to assess the spatial correlation of TF. Variograms for TF beneath two of the five trees reached a stable sill at the range of 5–6 m. The redistribution of TF within the canopy was highly variable in time, attributable to seasonal variation in canopy foliation and meteorological factors. As the length of the sampling period increased, the spatial variability of TF decreased and the temporal stability of the TF pattern increased. Time stability plots of TF normalized with respect to mean and variance showed a moderate general persistence for all individual trees. We conclude that single trees modify the spatial distribution of TF reaching the forest floors. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
235.
Ebrahim Ahmadisharaf Alfred J. Kalyanapu Jason R. Lillywhite Gina L. Tonn 《水文科学杂志》2013,58(12):1776-1790
ABSTRACTThis study presents a probabilistic framework to evaluate the impact of uncertainty of design rainfall depth and temporal pattern as well as antecedent moisture condition (AMC) on design hydrograph attributes – peak, time to peak, duration and volume, as well as falling and rising limb slopes – using an event-based hydrological model in the Swannanoa River watershed in North Carolina, USA. Of the six hydrograph attributes, falling limb slope is the most sensitive to the aforementioned uncertainties, while duration is the least sensitive. In general, the uncertainty of hydrograph attributes decreases in higher recurrence intervals. Our multivariate analysis revealed that in most of the return periods, AMC is the most important driver for peak, duration and volume, while time to peak and falling limb slope are most influenced by rainfall pattern. In higher return periods, the importance of rainfall depth and pattern increases, while the importance of AMC decreases. 相似文献
236.
Alfred Jahn 《Geoforum》1976,7(2):121-137
Geomorphological processes of the cold climate zone can be divided into natural and accelerated. In the former group the following processes are being discussed: frost weathering, mass wasting, solifluction, landslides, slopewash and linear erosion and wind action. Processes of accelerated action are due to natural and artificial stimuli. To the former belong for instance heavy rains which sometimes occur in polar zones (as in Spitsbergen in July 1972). More frequent however, are, artificial causes which are connected with man's activities.The action of geomorphological processes is indicated by the denudational balance which can be either positive or negative. The author has determined this balance for some regions of the Arctic and Subarctic, especially for Siberia. The balance is positive (degradation) in the zone of polar desert and in the oceanic part of the Arctic, and also in high mountains of this zone. Negative denudation balance prevails in the continental section of the Subarctic. The areas of positive denudational balance are threatened with nature destruction and therefore particularly deserve to be covered by a nature protection scheme. 相似文献
237.
Xi Zhao Alfred Stein Xiaoling Chen 《Stochastic Environmental Research and Risk Assessment (SERRA)》2010,24(5):713-723
Remotely sensed images as a major data source to observe the earth, have been extensively integrated into spatial-temporal
analysis in environmental research. Information on spatial distribution and spatial-temporal dynamic of natural entities recorded
by series of images, however, usually bears various kinds of uncertainties. To deepen our insight into the uncertainties that
are inherent in these observations of natural phenomena from images, a general data modeling methodology is developed to embrace
different kinds of uncertainties. The aim of this paper is to propose a random set method for uncertainty modeling of spatial
objects extracted from images in environmental study. Basic concepts of random set theory are introduced and primary random
spatial data types are defined based on them. The method has been applied to dynamic wetland monitoring in the Poyang Lake
national nature reserve in China. Four Landsat images have been used to monitor grassland and vegetation patches. Their broad
gradual boundaries are represented by random sets, and their statistical mean and median are estimated. Random sets are well
suited to estimate these boundaries. We conclude that our method based on random set theory has a potential to serve as a
general framework in uncertainty modeling and is applicable in a spatial environmental analysis. 相似文献
238.
Guilherme A. R. Gualda Alfred T. AndersonJr 《Contributions to Mineralogy and Petrology》2007,153(6):733-742
Little is known about the presence, distribution and size of bubbles in rhyolitic magmas prior to eruption. Using X-ray tomography
to study pumice from early-erupted Bishop rhyolite, we discovered a large vesicle with abundant magnetite crystals attached
to its walls. Attachment of magnetite crystals to bubble walls under pre-eruptive conditions can explain the cluster of magnetite
crystals as a result of bubbles rising and collecting magnetite crystals. Alternatively, bubbles may have nucleated on magnetite
crystals and then coalesced to form one large bubble with multiple magnetite crystals attached to it. We argue that the clusters
of magnetite crystals could not have formed during or after eruptive decompression, and conclude that this vesicle corresponds
to a bubble present prior to eruptive decompression. The inferred presence of pre-eruptive bubbles in the Bishop magma confirms
the interpretation that the magma was volatile-saturated prior to eruption. The pre-eruptive size of this bubble is estimated
based on three independent approaches: (1) the current size of the vesicle, (2) the total cross-sectional area of the magnetite
crystals, and (3) the bubble size required for the aggregate to be neutrally buoyant. These approaches suggest a pre-eruptive
bubble 300–850 μm in diameter, with a preferred value of 600–750 μm.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
239.
Lee H. Spangler Laura M. Dobeck Kevin S. Repasky Amin R. Nehrir Seth D. Humphries Jamie L. Barr Charlie J. Keith Joseph A. Shaw Joshua H. Rouse Alfred B. Cunningham Sally M. Benson Curtis M. Oldenburg Jennifer L. Lewicki Arthur W. Wells J. Rodney Diehl Brian R. Strazisar Julianna E. Fessenden Thom A. Rahn James E. Amonette Jon L. Barr William L. Pickles James D. Jacobson Eli A. Silver Erin J. Male Henry W. Rauch Kadie S. Gullickson Robert Trautz Yousif Kharaka Jens Birkholzer Lucien Wielopolski 《Environmental Earth Sciences》2010,60(2):227-239
A controlled field pilot has been developed in Bozeman, Montana, USA, to study near surface CO2 transport and detection technologies. A slotted horizontal well divided into six zones was installed in the shallow subsurface. The scale and CO2 release rates were chosen to be relevant to developing monitoring strategies for geological carbon storage. The field site was characterized before injection, and CO2 transport and concentrations in saturated soil and the vadose zone were modeled. Controlled releases of CO2 from the horizontal well were performed in the summers of 2007 and 2008, and collaborators from six national labs, three universities, and the U.S. Geological Survey investigated movement of CO2 through the soil, water, plants, and air with a wide range of near surface detection techniques. An overview of these results will be presented. 相似文献
240.
The occurrence of high‐pressure (HP) garnet‐bearing metamorphic rocks in the southern Barberton granitoid–greenstone terrane (BGGT), South Africa, has been proposed as a key indicator of the onset of modern plate tectonics at ca. 3.2 Ga. Here, we report new zircon/titanite U–Pb ages of garnet‐bearing HP metamorphic rocks and associated granitoids in the BGGT that argue against such an interpretation. The results show that HP metamorphism occurred synchronously with granitoid magmatism in the Stolzburg domain, the supposed subducted plate, during two episodes at 3.4 and 3.2 Ga, and that these two episodes of magmatism occurred on both sides of the assumed suture zone, a feature that cannot easily be explained by the subduction model. In contrast, the coupled magmatism and metamorphism probably resulted from partial convective overturn (PCO), another viable mechanism for production and differentiation of continental crust during early Archean. 相似文献