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991.
Jaccard Camille-Jean Abbruzzese Jacopo Maria Howald Erika Prina 《Natural Hazards》2020,100(1):459-459
Natural Hazards - Rock falls threaten human lives and assets in mountainous regions all over the world. Protection measures are one of the most effective solutions for mitigating rock fall-related... 相似文献
992.
Ali Syeda Maria Khalid Bushra Akhter Asma Islam Aneeza Adnan Shahzada 《Natural Hazards》2020,103(2):2533-2559
Natural Hazards - Frequency and intensity of extreme weather events are immensely changing throughout the world. This study aims to give insight into the changing climatic patterns leading to... 相似文献
993.
Concentration of damage of buildings near the edge of cliff-type topographies has been observed during a number of recent
earthquakes and interpreted by numerical dynamic analyses that illustrate the amplification of the horizontal acceleration
and the generation of parasitic vertical acceleration near the tip of slopes. The paper performs a detailed parametric numerical
analysis to investigate the ability of mitigating this topographic effect using anchors and piles. A typical field case, the
Aegion slope of Greece, is considered. Different input motions are applied. The results illustrated that anchors and piles
can be effective in mitigating the topographic effect. The main issue is that if the part of the slope in which topographic
amplification occurs is connected to that at larger depths, in which the acceleration is smaller, then the accelerations at
the top of the slope have to become more uniform and smaller. For typical diameter and material properties of anchors/piles
the effectiveness of the mitigation depends on the length, inclination, location and number of anchors/piles. An optimum configuration
of anchors/piles mitigating the topographic effect is proposed. 相似文献
994.
Luciana de Souza Soler Maria Isabel S. Escada Peter H. Verburg 《Applied geography (Sevenoaks, England)》2009,29(2):182-193
Spatial patterns of deforested areas and secondary forest are analyzed in terms of the spatial variation in location factors at different spatial extents. The spatial extents considered are old and new agrarian colonization projects and the administrative units of two different municipalities in Rondonia: Vale do Anari and Machadinho d'Oeste. A grid database was constructed including land cover and potential location factors based on biophysical, accessibility, socioeconomic and policy data. Results of the spatial analyses confirmed the hypothesis that different extents yield different relationships between land use/cover patterns and their location factors, particularly between old and new agrarian colonization projects. It emphasizes that current patterns of forest, secondary forest and pasture/agriculture can only be understood with a combination of policy, accessibility, biophysical and socioeconomic factors while accounting for the historical pathways of change. Because we are dealing with different trajectories of land use/cover change, static analysis of the spatial pattern without acknowledging these trajectories will lead to erroneous interpretations of the current and future land use/cover dynamics. 相似文献
995.
Photostability and photolability of dissolved organic matter upon irradiation of natural water samples under simulated sunlight 总被引:2,自引:0,他引:2
996.
Enrico Conte Renato Maria CosentiniAntonello Troncone 《Soil Dynamics and Earthquake Engineering》2009
The primary objective of this study is for presenting some simple-to-use expressions relating the shear and dilatational wave velocities (VS and VP) to some physical and constitutive parameters of unsaturated soils. To this purpose, a simplified formulation is developed using the theory of linear poroelasticity in conjunction with some constitutive parameters widely used in geotechnical engineering. The derived expressions are of practical interest in view of the fact that they could be employed for evaluating the involved soil parameters from VS and VP measurements by in-situ or laboratory geophysical tests. 相似文献
997.
The GEF/UNDP/IMO/PEMSEA project identifies Manila Bay as among the marine pollution hot spots in the Seas of East Asia. 210Pb dating of its sediment can provide a historical perspective of its pollution loading. However, the validity of 210Pb dating in a complex dynamic coastal system of Manila Bay may come into question. Land-based sediment input can be high and physical and biological processes can possibly disturb the sediment layers. In this report, the 210Pb profiles of sediment cores from different parts of the bay are presented. The linear sedimentation rates are shown to be higher in the recent past and are also variable across the bay. The largest change in sedimentation rate, coincided with the occurrence of a volcanic eruption in 1991 and is shown by applying a variant of the CIC model in sedimentation rate calculations. The data suggest that 210Pb dating can be useful in estimating relative magnitudes of sedimentation rates, even in a complex dynamic coastal system like Manila Bay. 相似文献
998.
Cyanobacterial toxins in Italian freshwaters 总被引:1,自引:0,他引:1
Valentina Messineo Serena Melchiorre Antonella Lugliè Maria Antonietta Mariani Antonio Di Corcia Ermanno Carloni 《Limnologica》2009,39(2):95-106
This study focuses on the occurrence and distribution of cyanobacterial toxins from 1989 to 2006 in several Italian lakes of different characteristics and human uses, the latter including drinking water abstraction and recreation. Phytoplankton and LC/MS/MS toxin analyses were performed on surface water samples collected from 28 lakes. The most widespread species associated with toxin production belonged to the genera Microcystis, Planktothrix and Anabaena. Extracellular concentrations varied from non-detectable values up to 226.16 ng/mL for microcystins (sum of all variants), to 126 ng/mL for total cylindrospermopsin, and to 100 μg/g (dry weight) for anatoxin-a.The toxin concentrations in the lake waters did not always correlate with the cyanobacteria cell densities. This implies a need for control studies including toxin detection in water together with microscopic cell evaluations, in order to avoid possible toxin underestimates. 相似文献
999.
Silvia Maria Caglierani Casanova Eliana Aparecida Panarelli Raoul Henry 《Limnologica》2009,39(4):292-301
Rotifera density, biomass, and secondary production on two marginal lakes of Paranapanema River were compared after the recovery of hydrologic connectivity with the river (São Paulo State, Brazil). Daily samplings were performed in limnetic zone of both lakes during the rainy season immediately after lateral inflow of water and, in the dry period, six months after hydrologic connectivity recovery. In order to identify the factors that affect rotifer population dynamics, lake water level, volume, depth, temperature, transparency, dissolved oxygen, pH, alkalinity, conductivity, suspended solids, nutrients, and chlorophyll-a were determined. Variations of water physical and chemical factors that affect rotifer population were related to the lake-river degree of connection and to water level rising after drought. The water lateral inflow from the river resulted in an increase in lake water volume, depth, and transparency and a decrease in water pH, alkalinity, and suspended solids. The lake with the wider river connection, more frequent biota exchange, and larger amount of particulate and dissolved materials was richer and more diverse, while rotifer density, biomass, and productivity were lower in both periods studied. Density, biomass, and secondary production were higher in the lake with the smaller river connection and the higher physical and chemical stability. Our results show that the connectivity affects the limnological stability, associated to seasonality. Stable conditions, caused by low connectivity in dry periods, were related with high density, biomass and secondary production. Conversely, instability conditions in rainy periods were associated to elevated richness and diversity values, caused by exchange biota due to higher connectivity. 相似文献
1000.
The aim of this work is to estimate the fundamental translational frequencies and relative damping of a large number of existing buildings, performing ambient vibration measurements. The first part of the work is devoted to the comparison of the results obtained with microtremor measurements with those obtained from earthquake recordings using four different techniques: horizontal‐to‐vertical spectral ratio, standard spectral ratio, non‐parametric damping analysis (NonPaDAn) and half bandwidth method. We recorded local earthquakes on a five floors reinforced concrete building with a pair of accelerometers located on the ground and on top floor, and then collected microtremors at the same location of the accelerometers. The agreement between the results obtained with microtremors and earthquakes has encouraged extending ambient noise measurements to a large number of buildings. We analysed the data with the above‐mentioned methods to obtain the two main translational frequencies in orthogonal directions and their relative damping for 80 buildings in the urban areas of Potenza and Senigallia (Italy). The frequencies determined with different techniques are in good agreement. We do not have the same satisfactory results for the estimates of damping: the NonPaDAn provides estimates that are less dispersed and grouped around values that appear to be more realistic. Finally, we have compared the measured frequencies with other experimental results and theoretical models. Our results confirm, as reported by previous authors, that the theoretical period–height relationships overestimate the experimental data. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献