全文获取类型
收费全文 | 961篇 |
免费 | 185篇 |
国内免费 | 240篇 |
专业分类
测绘学 | 157篇 |
大气科学 | 51篇 |
地球物理 | 350篇 |
地质学 | 449篇 |
海洋学 | 163篇 |
天文学 | 37篇 |
综合类 | 77篇 |
自然地理 | 102篇 |
出版年
2024年 | 5篇 |
2023年 | 9篇 |
2022年 | 35篇 |
2021年 | 36篇 |
2020年 | 36篇 |
2019年 | 47篇 |
2018年 | 26篇 |
2017年 | 51篇 |
2016年 | 58篇 |
2015年 | 52篇 |
2014年 | 76篇 |
2013年 | 66篇 |
2012年 | 61篇 |
2011年 | 54篇 |
2010年 | 58篇 |
2009年 | 63篇 |
2008年 | 64篇 |
2007年 | 74篇 |
2006年 | 63篇 |
2005年 | 57篇 |
2004年 | 50篇 |
2003年 | 43篇 |
2002年 | 39篇 |
2001年 | 29篇 |
2000年 | 36篇 |
1999年 | 24篇 |
1998年 | 34篇 |
1997年 | 21篇 |
1996年 | 17篇 |
1995年 | 12篇 |
1994年 | 15篇 |
1993年 | 15篇 |
1992年 | 8篇 |
1991年 | 8篇 |
1990年 | 5篇 |
1989年 | 12篇 |
1988年 | 5篇 |
1987年 | 8篇 |
1986年 | 7篇 |
1984年 | 2篇 |
1983年 | 3篇 |
1982年 | 1篇 |
1980年 | 1篇 |
排序方式: 共有1386条查询结果,搜索用时 15 毫秒
81.
In this paper, the dynamic stress concentration and scattering of SH-waves by bi-naterial structures that possess an interface elliptic cavity are investigated. First, by using the complex function method, the Green‘s function is constructed. This yields the solution of the displacement field for an elastic half space with a semi-elliptic canyon impacted by an anti-plane harmonic line source loading on the horizontal surface. Then, the problem is divided into an upper and lower half space along the horizontal interface, regarded as a harmony model. In order to satisfythe integral continuity condition,the unknown anti-plane forces are applied to the interface. The integral equations with unknown forces can be established through the continuity condition, and after transformation, the algebraic equations are solved numerically. Finally, the distribution of the dynamic stress concentration factor (DSCF) around the elliptic cavity is given and the effect of different parameters on DSCF is discussed. 相似文献
82.
泊松曲线是一种精度较高的沉降预测方法,但是它只能在等时距数据条件下方能使用,在工程实际中很难满足这一要求。本文采用插值法将非等时距数据转化成等时距数列,并结合高层建筑沉降监测工程实例分析,结果表明,用泊松曲线模型预测建筑物沉降量与实际沉降量比较接近,具有较高的应用价值。 相似文献
83.
84.
积分方程法三维模拟井地电法并行算法研究 总被引:1,自引:1,他引:1
在积分方程法模拟三维电磁响应原理的基础上,对井地电法三维正演模拟并行算法做了研究。同时,还利用Fortran 6.5和消息传递接口(MPI)开发了井地电法三维正演模拟并行计算程序。在求解大型线性方程组时,采用的是稳定的双共轭梯度(BICGSTAB)算法,单机正演程序与并行正演程序的计算结果有着很好的一致性,这说明了并行算法的正确性,为进一步开发井地电法三维反演并行程序奠定了基础,也为井地电法三维正、反演程序实用化提供了技术支持。 相似文献
85.
针对起伏地表条件下的地震波数值模拟问题,提出将起伏的地表映射到一个规则的长方形网格坐标系中,并在此基础上推导出变换域中的波动方程。根据导出来的波动方程应用有限余弦变换有限差分方法进行地震波场的数值模拟,以解决起伏地表条件下的数值模拟。 相似文献
86.
Accurate upward continuation of gravity anomalies supports future precision, free-inertial navigation systems, since the latter
cannot by themselves sense the gravitational field and thus require appropriate gravity compensation. This compensation is
in the form of horizontal gravity components. An analysis of the model errors in upward continuation using derivatives of
the standard Pizzetti integral solution (spherical approximation) shows that discretization of the data and truncation of
the integral are the major sources of error in the predicted horizontal components of the gravity disturbance. The irregular
shape of the data boundary, even the relatively rough topography of a simulated mountainous region, has only secondary effect,
except when the data resolution is very high (small discretization error). Other errors due to spherical approximation are
even less important. The analysis excluded all measurement errors in the gravity anomaly data in order to quantify just the
model errors. Based on a consistent gravity field/topographic surface simulation, upward continuation errors in the derivatives
of the Pizzetti integral to mean altitudes of about 3,000 and 1,500 m above the mean surface ranged from less than 1 mGal
(standard deviation) to less than 2 mGal (standard deviation), respectively, in the case of 2 arcmin data resolution. Least-squares
collocation performs better than this, but may require significantly greater computational resources. 相似文献
87.
88.
河南省地热资源丰富,在开封、周口、舞阳、济源、南阳盆地以及濮阳凹陷、汤阴地堑有望找到很好的热储层。现已开发的热储层为埋深800~1300m的第三系中细砂层,水温40~50℃,水质优良。如果加深钻井深度至2000m,则有望找到70℃以上的高温地热水,届时省内地热资源开发利用将上一个新台阶,达到供热采暖水平。文中对河南省地热资源的开发利用现状作一简要介绍,并对如何提高开发利用水平和资源保护提出建议。 相似文献
89.
Tilmann Gneiting 《Mathematical Geology》1998,30(4):379-390
The turning bands method generates realizations of isotropic Gaussian random fields by means of appropriately summed line processes. For two-dimensional simulations the relation between the isotropic correlation function of the random field and the correlation function to be simulated along the lines is given by an integral equation of Abel type. We present closed form solutions of this integral equation for almost all two-dimensional correlation models encountered in practice and discuss their numerical implementation. As an additional benefit, our tables and illustrations serve as a concise guide to correlation models useful in geostatistics. 相似文献
90.
FBocchio 《Geophysical Journal International》1998,133(1):207-208
The potentialities of the so-called 'Poisson relation', which holds for uniformly magnetized bodies of constant density, for showing the connections between the gravitational and the magnetic fields of such bodies are considered. In particular, it is seen that the same characteristic ratios occur among the components of the magnetic field intensity and the components of the gradient tensors of the two fields, both locally and non-locally. It is also shown that along the magnetization axis of the body the gradient tensor of the magnetic field displays a 'tidal' structure. 相似文献