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21.
AbstractThe scour phenomena around vertical piles in oceans and under waves may influence the structure stability. Therefore, accurately predicting the scour depth is an important task in the design of piles. Empirical approaches often do not provide the required accuracy compared with data mining methods for modeling such complex processes. The main objective of this study is to develop three data-driven methods, locally weighted linear regression (LWLR), support vector machine (SVR), and multivariate linear regression (MLR) to predict the scour depth around vertical piles due to waves in a sand bed. It is the first effort to develop the LWLR to predict scour depth around vertical piles. The models simulate the scour depth mainly based on Shields parameter, pile Reynolds number, grain Reynolds number, Keulegan–Carpenter number, and sediment number. 111 laboratory datasets, derived from several experimental studies, were used for the modeling. The results indicated that the LWLR provided highly accurate predictions of the scour depths around piles (R?=?0.939 and RMSE = 0.075). Overall, this study demonstrated that the LWLR can be used as a valuable tool to predict the wave-induced scour around piles. 相似文献
22.
渤海中南部悬浮物海洋调查资料分析 总被引:6,自引:0,他引:6
对于悬浮物 (SPM)的研究目前已引起诸多学者关注。作者利用 1998和 1999年的中德合作海洋调查所获得的资料进行分析。主要进行三个方面的工作 :研究悬浮物与透明度的关系 ;研究悬浮物与浊度的关系 ;估计海底剪切速度。并为研究悬浮物输运提供资料和作前期研究 相似文献
23.
本文对大气运动中垂直速度w计算中的几种校正方法作了分析比较,并在前人工作的基础上,对校正方法作了改进,提出了进行低通滤波、散度校正和法线风分量校正的方法。通过这些校正,使计算出的平均散度和垂直速度的垂直廓线能维持原计算曲线的形式,并能满足整个气层连续方程积分为零的条件,也符合误差随高度增大的情况。 相似文献
24.
In this study, we investigate two internal wave generation methods in numerical modeling of time-dependent equations for water wave propagation, i.e., delta source function method and source term addition method, the latter of which has been called the line source method in literatures. We derive delta source functions for the Boussinesq-type equations and extended mild-slope equations. By applying the fractional step splitting method, we show that the delta source function method is equivalent to the source term addition method employing the energy velocity. This suggests that the energy velocity should be used rather than the phase velocity for the transport of incident wave energy in the source term addition method. Finally, the performance of the delta source function method is verified by accurately generating nonlinear cnoidal waves as well as linear waves for horizontally one-dimensional cases. 相似文献
25.
A series of hydraulic model tests has been carried out in a glass wave flume to investigate the influences of wave height, wave period, wave steepness, surf similarity parameter, roughness, layer thickness and porosity on wave run-up and overtopping of 1:2 sloped impermeable and permeable breakwaters fronted by a 1:10 gentle, smooth beach slope. The analysis of results involves the correlation between the overtopping energy transfer with the relative wall height and the relationship between wave run-up and overtopping rate. Further, measured wave run-up and overtopping rates are compared with the results given in the Shore Protection Manual (1984), Automated Coastal Engineering System (1992)and results of other investigators. 相似文献
26.
A coupled wave–tide–surge model has been developed in this study in order to investigate the effect of the interactions among tides, storm surges, and wind waves. The coupled model is based on the synchronous dynamic coupling of a third-generation wave model, WAM cycle 4, and the two-dimensional tide–surge model. The surface stress, which is generated by interactions between wind and wave, is calculated by using the WAM model directly based on an analytical approximation of the results using the quasi-linear theory of wave generation. The changes in bottom friction are created by the interactions between waves and currents and calculated by using simplified bottom boundary layer model. In consequence, the combined wave–current-induced bottom velocity and effective bottom drag coefficient were increased in the shallow waters during the strong storm conditions. 相似文献
27.
Imaging of Buried Archaeological Materials: The Reflection Properties of Archaeological Wood 总被引:1,自引:0,他引:1
Stephanie H.L. Arnott Justin K. Dix Angus I. Best David J. Gregory 《Marine Geophysical Researches》2005,26(2-4):135-144
Effective marine archaeological site management demands detailed information on not only the spatial distribution of artefacts
but also the degradation state of the materials present. Although sonar methods have frequently been used in an attempt to
detect buried wooden shipwrecks they are currently unable to indicate their degradation state. To assess the sensitivity of
acoustic measurements to changes in the degradation state of such material, and hence the potential for sonars to quantify
degradation, laboratory measurements of compressional wave velocity, as well as bulk density for oak and pine samples, in
varying states of decay, were undertaken. These data enabled the calculation of theoretical reflection coefficients for such
materials buried in various marine sediments. As wood degrades, the reflection coefficients become more negative, resulting
in the hypothesis that the more degraded wood becomes, the easier it should be to detect. Typical reflection coefficients
of the order of −0.43 and −0.52 for the most degraded oak and pine samples in sand are predicted. Conversely, for wood exposed
to seawater the predicted reflection coefficients are large and positive for undegraded material (0.35 for oak, 0.18 for pine)
and decrease to zero or slightly below for the most degraded samples. This indicates that exposed timbers, when heavily degraded,
can be acoustically transparent and so undetectable by acoustic methods. Corroboration of these experimental results was provided
through comparison with high resolution seismic reflection data that has been acquired over two shipwrecks. 相似文献
28.
From the experimental studies in recent years, it has become known that when a wave breaks directly on a vertical faced coastal structure, high magnitude impact pressures are produced. The theoretical and experimental studies show that the dynamic response of such structures under wave impact loading is closely dependent on the magnitude and duration of the load history. The dynamic analysis and design of a coastal structure can be succeeded provided the design load history for the wave impact is available. Since these types of data are very scarce, it is much more convenient to follow a method which is based on static analysis for the dynamic design procedure. Therefore, to facilitate the dynamic design of a vertical plate that is exposed to breaking wave impact, a multiplication factor called “dynamic magnification factor” is herein presented which is defined as the ratio of the maximum value of the dynamic response to that found by static analysis. The computational results of the present study show that the dynamic magnification factor is a useful ratio to transfer the results of static analysis to the dynamic design of a coastal plate for the maximum impact pressure conditions of pmax/γH0≤18. 相似文献
29.
A statistical model is developed to predict wave overtopping volume and rate of extreme waves on a fixed deck. The probability density function for the volume and rate of overtopping water are formulated based on the truncated Weibull distribution with the assumption of local sinusoidal profile for small amplitude waves. Sensitivity to the wave nonlinearity parameter and deck clearance is discussed. The statistical model is compared to laboratory data of the instantaneous free surface elevation measured in front of a fixed deck, and overtopping volume and overtopping rate measured at the leading edge of the deck. The statistical theory compared well with the measured exceedance probability seaward of the deck. The model prediction of the exceedance probability of deck overtopping gave qualitatively good agreement for large overtopping values. 相似文献
30.
In this paper, we analyse the ability of the nonlinear shallow-water (NSW) equations to predict wave distortion and energy dissipation of periodic broken waves in the inner surf zone. This analysis is based on the weak-solution theory for conservative equations. We derive a new one-way model, which applies to the transformation of non-reflective periodic broken waves on gently sloping beaches. This model can be useful to develop breaking-wave parameterizations (in particular broken-wave celerity expression) in both time-averaged wave models and time-dependent Boussinesq-type models. We also derive a new wave set-up equation which provides a simple and explicit relation between wave set-up and energy dissipation. Finally, we compare numerical simulations of both, the NSW model and the simplified one-way model, with spilling wave breaking experiments and we find a good agreement. 相似文献