全文获取类型
收费全文 | 6882篇 |
免费 | 871篇 |
国内免费 | 1347篇 |
专业分类
测绘学 | 223篇 |
大气科学 | 705篇 |
地球物理 | 2131篇 |
地质学 | 3330篇 |
海洋学 | 1542篇 |
天文学 | 251篇 |
综合类 | 265篇 |
自然地理 | 653篇 |
出版年
2024年 | 32篇 |
2023年 | 92篇 |
2022年 | 175篇 |
2021年 | 209篇 |
2020年 | 328篇 |
2019年 | 347篇 |
2018年 | 288篇 |
2017年 | 407篇 |
2016年 | 338篇 |
2015年 | 367篇 |
2014年 | 462篇 |
2013年 | 627篇 |
2012年 | 469篇 |
2011年 | 328篇 |
2010年 | 304篇 |
2009年 | 382篇 |
2008年 | 458篇 |
2007年 | 422篇 |
2006年 | 377篇 |
2005年 | 304篇 |
2004年 | 277篇 |
2003年 | 265篇 |
2002年 | 243篇 |
2001年 | 206篇 |
2000年 | 204篇 |
1999年 | 210篇 |
1998年 | 184篇 |
1997年 | 162篇 |
1996年 | 136篇 |
1995年 | 108篇 |
1994年 | 77篇 |
1993年 | 72篇 |
1992年 | 59篇 |
1991年 | 57篇 |
1990年 | 25篇 |
1989年 | 32篇 |
1988年 | 16篇 |
1987年 | 11篇 |
1986年 | 10篇 |
1985年 | 9篇 |
1984年 | 6篇 |
1983年 | 1篇 |
1982年 | 4篇 |
1981年 | 2篇 |
1980年 | 4篇 |
1979年 | 1篇 |
1977年 | 1篇 |
1954年 | 2篇 |
排序方式: 共有9100条查询结果,搜索用时 15 毫秒
91.
AbstractWith the large-scale development and utilization of ocean resources and space, it is inevitable to encounter existing submarine facilities in pile driving areas, which necessitates a safety assessment. In this article, by referring to a wharf renovation project as a reference, the surrounding soil response and buried pipe deformation during pile driving in a near-shore submarine environment are investigated by three-dimensional (3D) numerical models that consider the pore water effect. Numerical studies are carried out in two different series: one is a case of a single pile focusing on the effect of the minimum plane distance of the pile–pipe, and the other is a case of double piles focusing on the effect of the pile spacing. 相似文献
92.
Various offshore structures, especially large structures such as Tension Leg Platforms (TLP), are usually supported by concrete piles as the foundation elements. The stress distribution within such a large structure is a dominant factor in the design procedure of an offshore pile. To provide a more accurate and effective design for offshore foundation systems under axial and lateral wave loads, a finite element model is employed herein to determine the stresses and displacements in a concrete pile under similar loading conditions. A parametric study is also performed to examine the effects of the stress distribution due to the changing loading conditions. 相似文献
93.
94.
In 1995, Suh and Park developed a numerical model that computes the reflection of regular waves from a fully perforated-wall caisson breakwater. This paper describes how to apply this model to a partially perforated-wall caisson and irregular waves. To examine the performance of the model, existing experimental data are used for regular waves, while a laboratory experiment is conducted in this study for irregular waves. The numerical model based on a linear wave theory tends to over-predict the reflection coefficient of regular waves as the wave nonlinearity increases, but such an over-prediction is not observed in the case of irregular waves. For both regular and irregular waves, the numerical model slightly over- and under-predicts the reflection coefficients at larger and smaller values, respectively, because the model neglects the evanescent waves near the breakwater. 相似文献
95.
An unsteady wave driver for narrowbanded waves: modeling nearshore circulation driven by wave groups
In this paper, we derive an unsteady refraction–diffraction model for narrowbanded water waves for use in computing coupled wave–current motion in the nearshore. The end result is a variable coefficient, nonlinear Schrödinger-type wave driver (describing the envelope of narrow-banded incident waves) coupled to forced nonlinear shallow water equations (describing steady or unsteady mean flows driven by the short-wave field). Comparisons with experimental data show that good accuracy can be obtained for cases of nonbreaking wave transformation. Numerical simulations show that the interaction of wave groups with longshore topographic nonuniformities generates strong edge wave resonances, providing a generating mechanism for low-order edge waves. 相似文献
96.
97.
The relevant theory is presented and numerical results are compared with the analytical solution for the interaction of non-breaking waves with an array of vertical porous circular cylinders on a horizontal bed. The extension to the cases of unidirectional and multidirectional waves is obtained by means of a transfer function. The influence of the mechanical properties of porous structures and wave irregularity on wave transformation is analysed. Results for unidirectional and multidirectional wave spectra are compared to those obtained for regular waves. The model presented reproduces well the analytical results and provides a tool for analysing several engineering problems. 相似文献
98.
研究具有窄谱和Weibull波高分布的波群对非线性桩柱系统作用力的统计性质。求得了桩桩的波浪峰力的各种特征值及其比值。指出这些数值不仅是阻力一惯性力参数bH的函数,也随着波群因子而变化。本文模式更具广泛性。文中给出了一系列计算图表,可从理论计算波群作用于桩柱的波浪峰力。 相似文献
99.
Numerical simulations of gravity waves with high-order nonlinearities in two-dimensional domain are performed by using the pseudo spectral method. High-order nonlinearities more than third order excite apparently chaotic evolutions of the Fourier energy in deep water random waves. The high-order nonlinearities increase kurtosis, wave height distribution and Hmax/H1/3 in deep water and decrease these wave statistics in shallow water. Moreover, they can generate a single extreme high wave with an outstanding crest height in deep water. High-order nonlinearities (more than third order) can be regarded as one cause of freak waves in deep water. 相似文献
100.
A model for solving the two-dimensional enhanced Boussinesq equations is presented. The model equations are discretised in space using an unstructured finite element technique. The standard Galerkin method with mixed interpolation is applied. The time discretisation is performed using an explicit three-step Taylor–Galerkin method. The model is extended to the surf and swash zone by inclusion of wave breaking and a moving boundary at the shoreline. Breaking is treated by an existing surface roller model, but a new procedure for the detection of the roller thickness is devised. The model is verified using four test cases and the results are compared with experimental data and results from an existing finite difference Boussinesq model. 相似文献