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91.
P N Ananth Rao V S N Tatavarti J Swain C V K Prasada Rao 《Journal of Earth System Science》1993,102(2):351-366
Directional wave data collected during an experiment at a location on the continental shelf of the south west coast of India
using a WAVEC buoy, have been analysed based on the technique of Kuiket al (1988). The observed wave spectra indicate that the wave field is composed of sea waves (with peaks around 0·18 and 0·23
Hz) travelling nearly in the wind direction (WNW-N), and lower frequency (0·09 Hz) swell waves from the South. The parameterization
of the wave directional spread shows that both local wind conditions and nonlinear wave-wave interactions control the shape
of the directional distribution. The directional distribution is generally bimodal in the transition region between sea and
swell and at higher frequencies when rapid changes in wind speed and direction occur. 相似文献
92.
《中国海洋大学学报(英文版)》2007,(1)
1 Introduction Today, maneuvering the draghead of a trailing suction hopper dredger (TSHD) on a predetermined spot is an operation that demands an increasing degree of accuracy (Cornelis, 1983). As a self-propelled, self-loading and self-discharging seagoing or inland waterway vessel with one or more flexible suction pipes equipped with special dragheads, the TSHD has a wide application area and is therefore called the workhorse of the dredging industry (Ni, 2004). The swell compensator, c… 相似文献
93.
94.
J. Pim C. Peirce A.B. Watts I. Grevemeyer A. Krabbenhoeft 《Earth and Planetary Science Letters》2008,272(1-2):422-428
The Cape Verde Islands are located on a mid-plate topographic swell and are thought to have formed above a deep mantle plume. Wide-angle seismic data have been used to determine the crustal and uppermost mantle structure along a ~ 440 km long transect of the archipelago. Modelling shows that ‘normal’ oceanic crust, ~ 7 km in thickness, exists between the islands and is gently flexed due to volcano loading. There is no direct evidence for high density bodies in the lower crust or for an anomalously low density upper mantle. The observed flexure and free-air gravity anomaly can be explained by volcano loading of a plate with an effective elastic thickness of 30 km and a load and infill density of 2600 kg m− 3. The origin of the Cape Verde swell is poorly understood. An elastic thickness of 30 km is expected for the ~ 125 Ma old oceanic lithosphere beneath the islands, suggesting that the observed height of the swell and the elevated heat flow cannot be attributed to thermal reheating of the lithosphere. The lack of evidence for high densities and velocities in the lower crust and low densities and velocities in the upper mantle, suggests that neither a crustal underplate or a depleted swell root are the cause of the shallower than expected bathymetry and that, instead, the swell is supported by dynamic uplift associated with the underlying plume. 相似文献
95.
研究掺粉煤灰对合肥膨胀土的物理性质指标以及胀缩性指标等的影响,探讨利用粉煤灰改良膨胀土的措施与效果。试验研究结果表明,在膨胀土中掺入适量的粉煤灰可有效降低膨胀土的塑性指数、降低膨胀势、减小线缩率与降低活性。在膨胀土中掺入粉煤灰还可改变膨胀土的击实特性,一定击实功作用下,随着掺灰率的增加,土体的最优含水率与最大干密度均减小,膨胀土中掺入粉煤灰后,膨胀土可在较小的含水率下通过击实或压实达到稳定。掺灰膨胀土的膨胀量与膨胀力随养护龄期的增长而减小;没有经过养护的掺灰土,其无侧限抗压强度随掺灰率的变化几乎没有变化,经过7 d养护后,土的无侧限抗压强度有所增长,并且存在一个峰值点,合肥膨胀土的无侧限抗压强度所对应的最佳掺粉煤灰率约为15 %~20 %。 相似文献
96.
97.
A series of laboratory tests was conducted on a tropical residual soil, which is widespread and readily available over a considerable part of Peninsular Malaysia, to assess whether it could be compacted as hydraulic barriers in waste disposal landfills. Index properties, swelling potential, cation exchange capacity (CEC), compaction characteristics, and hydraulic conductivity of the soil indicate that it is inorganic, very plastic, inactive (activity <0.75), moderately expansive (modified free swell index is about 3.06), and of fair attenuation capacity (for inorganic contaminants). For hydraulic conductivity measurement, the soil was compacted in rigid-wall permeameter moulds at a variety of water contents and compactive efforts and then permeated with de-aired tap water. The results of hydraulic conductivity tests illustrate that hydraulic conductivity lower than 1×10–7 cm/s can be achieved using a broad range of water contents and compactive efforts, including water contents dry of optimum. Its shrinkage and strength properties show that it has minimal potential to shrinkage and has adequate strength to support the overburden pressure imposes by the waste body. These findings suggest that the residual soil can be potentially utilized as compacted soil liner material. 相似文献
98.
Springtime fetch in the Cape Bathurst Polynya System may present opportunities for winds to generate waves capable of propagating into the thick pack ice formed over the winter. A waves-in-ice event at a study site located on the Canadian Shelf in the southern Beaufort Sea that occurred 22–23 May 2011 is presented and analyzed for wave energy attenuation and dissipation characteristics. The event was monitored near the ice edge and, therefore, presents information on attenuation of waves from the ice edge into the pack. Waves of T?=?5?s, λ?=?37.5?m were observed up to approximately 143?m and approximately 77?m away from the ice edge during two separate observation periods of ice edge wave propagation. We estimated reflection coefficients of 53% and 52% and wave attenuation coefficients of α?=?2.4?×?10?2?m?1 and α?=?5.4?×?10?2?m?1, respectively, for the two periods. Estimated attenuation rates are an order of magnitude greater than in comparable studies and are inconsistent with previous findings of a “rollover” effect in attenuation rates for short-period waves. 相似文献
99.
In this study, research was conducted to examine the performance of the lime pile application, a deep chemical stabilization method to improve the engineering characteristics of marine soil deposits. By using a laboratory-scale model, the marine soil sample was compacted into soil blocks in circular steel test tanks, with the installation of lime piles in them. An experimental program examined the effect of lime piles on physical and engineering properties of the soil in terms of curing periods and lime pile radial distances. Test results showed that clay fines, linear shrinkage, compressibility, and swelling pressure decreased, while permeability, preconsolidation pressure, and stiffness increased significantly with an increase in curing periods and within a close distance to the lime piles. Also, the electrical resistivity of the treated soils was examined to monitor the changes in their electrical properties. Finally, the correlation between the measured electrical resistivity and swell pressure values of the tested soils at different curing periods suggested that the electrical resistivity values can be used as a monitoring technique for deep chemical treatments of the subsurface soil. 相似文献
100.
随着船舶大型化和港口建设深水化发展,外海不同周期波浪作用下大型系泊船泊稳问题与小型系泊船相比出现了新的特点。为此,利用数值模型方法研究了在不同入射角度和周期的涌浪作用下港内大型系泊船的水动力响应,针对系泊船的泊稳情况探讨了船舶的运动规律和运动特性。研究发现,在涌浪周期较大的情况下,限定波高的泊稳标准不足以用来确定系泊船的正常作业条件,港内泊船的水平运动(纵荡、横荡和艏摇)极易超出运动标准值并影响装卸作业效率,并且船舶的水平运动表现出主要由次重力波主导的低频运动特性,而垂直运动(垂荡、横摇和纵摇)表现出主要由短波主导的波频运动特性。 相似文献