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961.
Earthquake-related hydrochemical changes in thermal springs have been widely observed; however, quantitative modeling of the reactive transport process is absent. In the present study, we apply reactive transport simulation to capture the hydrochemical responses in a thermal spring following the Wenchuan Ms 8.0 and Lushan Ms 7.0 earthquakes. We first constrain deep reservoir geothermal fluid compositions and temperature by multicomponent geothermometry, and then a reactive geochemical transport model is constructed to reproduce the hydrochemical evolution process. The results show that the recharge from the shallow aquifer increases gradually until it reaches a peak because of the permeability enhancement caused by the Lushan earthquake, which may be the mechanism to explain the earthquake-related hydrochemical responses. In contrast to the postseismic effect of the Wenchuan earthquake, the chemical evolution can be considered as hydrochemical anomalies related to the Lushan earthquake. This study proves that the efficient simulation of reactive transport processes is useful for investigating earthquake-related signals in hydrochemical time series. 相似文献
962.
We propose a semi-empirical model for the relation between global mean surface temperature and global sea-levels. In contradistinction to earlier approaches to this problem, the model allows for valid statistical inference and joint estimation of trend components and interaction term of temperature and sea-level. Estimation of the model on the data set used in Rahmstorf (2007) yields a proportionality coefficient of 4.6 mm/year per °C at a one-sided significance level of 7.6 percent or higher. Long-term simulations of the model result in a two-sided 90-percent confidence interval for the sea-level rise in the year 2100 of [15 cm, 150 cm] above the 1990 level. This is a wider margin of error than was reported in the previous literature, and it reflects the substantial uncertainty in relating two trending time series. 相似文献
963.
Two numerical experiments were performed by using the Community Atmosphere Model version 3 (CAM3) with different sea ice datasets to assess the contribution of the decline of Arctic sea ice to warming in the Northern Hemisphere. One experiment was driven by observed sea ice cover data; for the other one, the authors used the sea ice data of the 4×CO2 scenario simulated by the fourth-generation European Centre Hamburg atmospheric general circulation Model of Istituto Nazionale di Geofisica e Vulcanologia, Italy (INGV_ECHAM4). The comparison of the two experiments indicates that the decline of the Arctic sea ice leads to a dramatic warming over the high latitudes of the Northern Hemisphere, characterized by a maximum warming of more than 26℃ over the Arctic region. The significant warming is closely related to the enhanced atmospheric heat source. A 40-60 Wm-2 increase in the apparent heat source was simulated in winter due to the decline of Arctic sea ice. In contrast, no significant change was found in the atmospheric apparent heat source in summer. As a result, the summer temperature change induced by the decline of Arctic sea ice appears to be weak. This study suggests that accurate sea ice cover data is crucial for future climate projection of air temperature in high latitudes. 相似文献
964.
965.
Maximum sustainable yield (MSY) has been adopted as the primary management goal by several inter-government fishery organisations, and in the United States it forms the cornerstone of federal fishery management policy. MSY became a strategic goal for the management of Europe's fisheries following the resolution of the World Summit on Sustainable Development in 2002 to restore or maintain fish stocks to MSY levels by 2015. Calculation of MSY requires information on the rate at which biomass increases through growth and reproduction and the rate at which it decreases through natural mortality and fishing. Population-selection, which measures the age-specific rates of fishing mortality, is a key component for the calculation of yield as a function of fishing mortality and MSY, yet selection rarely features in either management advice or sensitivity analyses. Effective management of selection can potentially lead to increases in long-term yield, but before taking action managers need to understand what long-term increases are possible. Using a hypothetical stock, equilibrium yield curves were calculated for three scenarios in which the shape of the population-selection curve varied. The results illustrate the potential extent of variation in MSY and the corresponding fishing mortality required to achieve it (FMSY) that may result solely due to changes in population selectivity. They show that relatively subtle changes in selection can produce substantial differences in MSY and FMSY. The results are discussed with specific reference to the development of long-term management targets and the mechanisms by which managers might try to influence population-selection. 相似文献
966.
Ingrid Kröncke 《Estuarine, Coastal and Shelf Science》2011,94(3):234-245
The macrofauna communities on the Dogger Bank (North Sea) from the 1920s, the 1950s and the 1980s to the 2000s were compared and identified five communities with similar spatial distribution throughout the 20th century. The abundance of dominant species in the five communities varied with time. Most obvious in the 1950s was the loss of the extensive Spisula and Mactra patches, which covered most of the shallow parts of the Bank in the 1920s. Since the 1980s, they have been found only as juveniles. The biological regime shift in the late 1980s caused an increase in macrofauna abundance, species numbers, diversity and southern species in most of the communities. The climate regime shift in 2001 had opposite effects in which the abundance, species numbers, diversity and southern species decreased in most of the communities. The increase in interface-feeding species and the decrease in sand-licking amphipods in the 2000s especially in the shallow Bank Community give evidence for climate driven changes in water masses, currents, storms, turbidity and food availability via planktonic or benthic primary production. Both fishing impact and climate change are hypothesised as explaining the changes in the Dogger Bank macrofauna communities. 相似文献
967.
968.
Design of an offshore wind turbine requires estimation of loads on its rotor, tower and supporting structure. These loads are obtained by time-domain simulations of the coupled aero-servo-hydro-elastic model of the wind turbine. Accuracy of predicted loads depends on assumptions made in the simulation models employed, both for the turbine and for the input wind and wave conditions. Currently, waves are simulated using a linear irregular wave theory that is not appropriate for nonlinear waves, which are even more pronounced in shallow water depths where wind farms are typically sited. The present study investigates the use of irregular nonlinear (second-order) waves for estimating loads on the support structure (monopile) of an offshore wind turbine. We present the theory for the irregular nonlinear model and incorporate it in the commonly used wind turbine simulation software, FAST, which had been developed by National Renewable Energy Laboratory (NREL), but which had the modeling capability only for irregular linear waves. We use an efficient algorithm for computation of nonlinear wave elevation and kinematics, so that a large number of time-domain simulations, which are required for prediction of long-term loads using statistical extrapolation, can easily be performed. To illustrate the influence of the alternative wave models, we compute loads at the base of the monopile of the NREL 5MW baseline wind turbine model using linear and nonlinear irregular wave models. We show that for a given environmental condition (i.e., the mean wind speed and the significant wave height), extreme loads are larger when computed using the nonlinear wave model. We finally compute long-term loads, which are required for a design load case according to the International Electrotechnical Commission guidelines, using the inverse first-order reliability method. We discuss a convergence criteria that may be used to predict accurate 20-year loads and discuss wind versus wave dominance in the load prediction. We show that 20-year long-term loads can be significantly higher when the nonlinear wave model is used. 相似文献
969.
近50a来天山博格达峰地区四工河4号冰川表面高程变化特征 总被引:5,自引:3,他引:2
基于GIS技术,利用GPS测量数据和1962年地形图分别建立两期DEM,通过对比重点研究了四工河4号冰川1962-2009年冰舌区的表面高程变化特征。结果表明:1962-2009年间,冰舌区平均减薄15±10 m,年均减薄约0.32±0.2 m,冰储量亏损达(14.3±9.5)×10-3km3,折合水当量(12.9±8.6)×10-3km3。不同海拔、坡度区间冰面高程变化差异显著,海拔较低、坡度较缓区域的变化最为强烈。在气候变暖的趋势下,四工河4号冰川发生强烈消融,标志着博格达峰地区的冰川正处于物质严重亏损的状态,直接影响到流域水资源状况。 相似文献
970.
H. Rovithis-Livaniou 《Astrophysics and Space Science》2005,296(1-4):91-99
A brief review of the physical mechanisms that could produce the observed orbital period changes in close binaries, the methods
used to study them, and a general discussion is given. 相似文献