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901.
902.
903.
西沙永兴岛珊瑚砂场地工程性质研究 总被引:2,自引:0,他引:2
现场载荷试验及轻型触探(N10)试验结果显示,珊瑚砂场地土颗粒之间存在着胶结作用,这是珊瑚砂地基的主要特点之一。颗粒大小、级配及水质条件与土的力学性质密切相关,水位的存在使地基具有上硬下软的双元结构特点,与相对密度相同的石英砂地基相比,其沉降变形要小几十倍。 相似文献
904.
Radiocarbon analyses were carried out in the annual bands of a 40 year old coral collected from the Gulf of Kutch (22.6°N,
70°E) in the northern Arabian Sea and in the annual rings of a teak tree from Thane (19°14′N, 73°24′E) near Bombay. These
measurements were made in order to obtain the rates of air-sea exchange of CO2 and the advective mixing of water in the Gulf of Kutch. The Δ14C peak in the Thane tree occurs in the year 1964, with a value of ∼630‰, significantly lower than that of the mean atmospheric
Δ14C of the northern hemisphere (∼ 1000‰). The radiocarbon time series of the coral was modelled considering the supply of carbon
and radiocarbon to the gulf through air-sea exchange and advective water transport from the open Arabian Sea. A reasonable
fit for the coral data was obtained with an air-sea CO2 exchange rate of 11–12 mol m−2 yr−1, and an advective velocity of 28 m yr−1 between the Arabian Sea and the Gulf of Kutch; this was based on a model generated time series for radiocarbon in the Arabian
Sea. The deduced velocity (∼ 28 m yr−1) of the advective transport of water between the gulf and the Arabian Sea is much lower than the surface tidal current velocity
in this region, but can be understood in terms of net fluxes of carbon and radiocarbon to the gulf to match the observed coral
Δ14C time series. 相似文献
905.
四川龙门山石炭纪珊瑚组合序列 总被引:2,自引:0,他引:2
四川龙门山地区石炭系发育完整,生物化石丰富,是研究石炭系良好的地区之一。本文依据珊瑚化石演化序列,提出本区石炭系8个珊瑚组合序列。本区石炭系厚约220m,以碳酸盐岩沉积为主。上界与二叠系为假整合;下界和泥盆系连续沉积。在其下伏的地层中发现有孔虫Quasiendothyra Communis(Rauser),可归入上泥盆统,相当于西欧的艾特隆层。因此本区的下界和西欧的泥盆—石炭界线是接近的。 相似文献
906.
As is well-known, Nansha Islands in the South China Sea (SCS) are of important strategic position and invaluable ecological value. Therefore, many attentions are paid to either the political and legal aspects of exposed features that matter in the maritime delimitation, or the physical and geographical characteristics of coral reefs that are the predominant structures of these islands. However, it seems that they consistently lose the connection of sciences and humanities in the research of Nansha Islands in the SCS. In this study, we carry out a combinative research, based on remote sensing data using satellite imagery analysis together with historical materials using literature investigation, so as to reconsider to the geographical characteristics of Nansha Islands from a standpoint of the United Nations Convention on the Law of the Sea (UNCLOS). After thoroughly appraising the statuses of these newly formed sand cays, several high tide features of Nansha Islands are identified. By means of the comparison of satellite images coupled with reference to nautical charting and sailing directions during different time periods, we can conclude that the statuses of these high tide features formed on reef platforms are relatively stable due to the growth of reef-building organisms although their migration patterns are subject to external disturbances, and hence the cursory judgment pursuant to the relevant provisions of the UNCLOS about whether a coral reef belongs to a low tide elevation only based on outdated references or ex parte evidences is not reliable. Moreover, it is accordingly justified to improve further development and perfection of the maritime legislation by eliminating such ambiguities with the growth of coral reefs and the evolution of sand cays being both taken into account. 相似文献
907.
908.
909.
《Geomechanics and Geoengineering》2013,8(3):185-194
In this paper, a model for the analysis of footings having finite flexural rigidity resting on a granular bed on top of stone columns improved saturated soft (clayey) soil has been proposed. Soft soil has been modeled as a Kelvin–Voigt body to represent its time dependent behavior. Pasternak shear layer has been used to represent the granular layer and the stone columns have been idealized by means of nonlinear Winkler springs. Nonlinear behavior of granular fill, soft soil and stone columns has been invoked by means of hyperbolic constitutive relationships. Governing differential equations for the soil–foundation system have been obtained and finite difference method has been adopted for solving these, using the Gauss-elimination iterative scheme. Detailed parametric study for a combined footing has been carried out to study the influence of parameters, like magnitude of applied load, flexural rigidity of footing, diameter of stone column, spacing of stone column, ultimate bearing capacity of granular fill, poor foundation soil and stone column, relative stiffness of stone columns and degree of consolidation, on flexural response of the footing. 相似文献
910.
The sedimentological and chronological analysis of the last deglacial reef sequences of Tahiti (French Polynesia), drilled during the Integrated Ocean Drilling Program Expedition 310, provide a high‐resolution data set allowing a well‐constrained forward modelling study. This study represents the first attempt to model in three dimensions the coral reef development of Tahiti during the last deglacial sea‐level rise (23 000 to 6000 cal yr bp ) using the software dionisos developed by IFP Energies nouvelles. It allows the testing of the reconstructed last deglacial sea‐level curve and the different environmental parameters (for example, wave energy and sediment fluxes) that could have influenced the reef development. These last deglacial reef sequences form two prominent ridges occurring seaward of the living barrier reef that consist of successive submerged reefs. These reefs have been prone to drowning because the window of maximum carbonate production rate is inhibited by high water turbidity (sediment supply from a nearby river), shallow depth of wave action and substrate availability. These factors, combined with rapid sea‐level rise, have driven the growth of retrograding reef pinnacles. Local factors (substratum nature, sediment supply and wave energy) were the main processes that induced the drowning of the inner ridge, whereas interplay of local and global factors (acceleration of the sea‐level rise) was responsible for the drowning of the outer ridge. This particular acceleration of sea‐level rise of 16 m between 14·6 ka and 14 ka bp corresponds to meltwater pulse 1A. 相似文献