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991.
992.
Yinhe Luo Jianghai Xia Yixian Xu Chong Zeng Richard D. Miller Qingsheng Liu 《Pure and Applied Geophysics》2009,166(3):353-374
Multichannel analysis of surface waves (MASW) method is a non-invasive geophysical technique that uses the dispersive characteristic
of Rayleigh waves to estimate a vertical shear (S)-wave velocity profile. A pseudo-2D S-wave velocity section is constructed
by aligning 1D S-wave velocity profiles at the midpoint of each receiver spread that are contoured using a spatial interpolation
scheme. The horizontal resolution of the section is therefore most influenced by the receiver spread length and the source
interval. Based on the assumption that a dipping-layer model can be regarded as stepped flat layers, high-resolution linear
Radon transform (LRT) has been proposed to image Rayleigh-wave dispersive energy and separate modes of Rayleigh waves from
a multichannel record. With the mode-separation technique, therefore, a dispersion curve that possesses satisfactory accuracy
can be calculated using a pair of consecutive traces within a mode-separated shot gather. In this study, using synthetic models
containing a dipping layer with a slope of 5, 10, 15, 20, or 30 degrees and a real-world example, we assess the ability of
using high-resolution LRT to image and separate fundamental-mode Rayleigh waves from raw surface-wave data and accuracy of
dispersion curves generated by a pair of consecutive traces within a mode-separated shot gather. Results of synthetic and
real-world examples demonstrate that a dipping interface with a slope smaller than 15 degrees can be successfully mapped by
separated fundamental waves using high-resolution LRT. 相似文献
993.
三维地震观测系统共聚焦分辨率特性分析突破传统以点论证为基础的观测系统分辨率分析方法,面向地质目标定量预测三维观测系统地震成像的空间分辨率和振幅精度.基于Fourier有限差分(FFD)大步长波场延拓和Born-Kirchhoff小步长波场插值递推方法,本文介绍了一种复杂介质条件下三维地震观测系统共聚焦分辨率特性快速分析方法.对给定的速度模型,该方法能够分析拟采用的三维地震观测系统设计方案对复杂构造的成像分辨率与AVP属性,从而为进一步的偏移成像与储层分析提供保证.最后本文以SEG/EAGE三维盐丘模型为例设计满覆盖为16次的三维地震观测系统,并实施三维共聚焦分辨率特性分析. 相似文献
994.
海洋可控源电磁法已经成为海洋油气勘探一个重要工具,但是其资料处理和解释还处于定性和一维模拟阶段.在积分方程三维模拟的基础上对Troll油田实测数据进行了处理,采用人机交互三维模拟寻找背景模型和异常体初始模型,最后对异常体电阻率采用准线性近似快速反演,取得了定量的结果.同时,说明对于二维测线和二维模型依然可以用三维来模拟,其结果优于二维反演.在电子计算机技术快速发展的今天,可以预计三维反演将成为资料处理解释的主流. 相似文献
995.
应用三维非均匀交错网格有限差分程序模拟了多极子随钻声波测井的波场,考察了硬地层中单极子随钻声波测井响应及软地层中声源频率对多极子随钻声波测井的影响;计算了接收阵列波形的时域相干谱及频散特征,结果表明随钻测井仪器居中时,在硬地层中可以直接利用单极子声系得到地层横波速度,但地层纵波受到钻铤波的极大干扰.而在软地层中可以利用单极子声系直接测得地层纵波速度,但地层横波速度则需要使用工作在较低频率下的四极子随钻声波仪来测得,此时测井频段又会落入钻井噪声频带而受到影响.为此本文提出数值模拟手段结合物理实验的方法得到钻铤波的影响,在实际测井中通过信号处理方法而不是用在仪器本体上刻槽的方式来更完全地消除钻铤的影响.为了避免钻井噪声的影响,本文提出六极子随钻声波仪更适合软地层的横波测量.本文用数值实验结果来说明这些方法的可行性. 相似文献
996.
Google Earth在地震应急中的应用 总被引:12,自引:0,他引:12
Google Earth是当前非常流行的三维虚拟地球仪软件, 以在全球范围内提供丰富的遥感影像资源而著称, 得到了许多行业的普遍应用。 我国目前地震应急指挥工作的GIS数据还是以二维展示为主, 引入新技术具有重要的意义。 Google Earth在我国的地震应急指挥工作中可以采取如下应用方案: 制作并加载行政区划图, 发布公众地震信息; 与GPS结合, 进行救援路线导航与跟踪; 根据现场资料建立三维模型, 展现地震灾区现场立体场景变化。 该应用方案对我国的地震应急指挥改革具有借鉴意义。 相似文献
997.
Margherita Polacci Don R. Baker Liping Bai Lucia Mancini 《Bulletin of Volcanology》2008,70(9):1023-1029
Volcanic degassing is directly linked to magma dynamics and controls the style of eruptive activity. To better understand
how gas is transported within basaltic magma we perform a 3D investigation of vesicles preserved in scoria from the 2005 activity
at Stromboli volcano (Italy). We find that clasts are characterized by the ubiquitous occurrence of one to a few large vesicles,
exhibiting mostly irregular, tortuous, channel-like textures, orders of magnitude greater in volume than all the other vesicles
in the sample. We compare observations on natural samples with results from numerical simulations and experimental investigations
of vesicle size distributions and demonstrate that this type of vesicle invariably forms in magmas with vesicularities > 0.30
(and possibly > 0.10). We suggest that large vesicles represent pathways used by gas to flow non-explosively to the surface
and that they indicate the development of an efficient system that sustains persistent degassing in basaltic systems. 相似文献
998.
This paper presents a 3D model in sigma coordinates. Although the principles it is based on have been established for some time, some original aspects for this type of 3D mode splitting model are presented here. The model was designed to simulate flows in various coastal areas from the regional scale down to the inshore scale of small bays or estuaries where circulation is generally driven by a mix of processes. The processes to be modeled enable simplifications of the Navier–Stokes equations on the classic Boussinesq and hydrostatic hypotheses. These equations are transformed within a sigma framework to make free surface processing easier. The main point of our demonstration focuses on the original aspect of the coupling between barotropic and baroclinic modes especially designed for ADI. It explains how full consistency of the transport calculated within the 2D and 3D equation sets was obtained. Lastly, we describe the physical processes simulated on a realistic configuration at a regional scale in the Bay of Biscay. 相似文献
999.
Corinne Lacave Pierre-Yves Bard Marc Kham Martin G. Koller 《Bulletin of Earthquake Engineering》2008,6(2):197-211
In the framework of the Sismovalp European project, an equivalent linear 2D code was developed to compute the response of
a valley to SH waves, using the discrete wave-number method proposed by Aki and Larner (Aki K, Larner KL (1970) J Geophys
Res 75:5). To overcome the frequency upper bound limitation, the Aki and Larner’s method is combined with a one-dimensional
computation using a classical multi-layer method (Aki K, Richards PG (1980) Quantitative Seismology: Theory and Methods, vols.
1 & 2. W.H. Freeman & Co, San Francisco). The so-called “Aki–Larner extended method” is associated to an iterative algorithm,
as proposed by Seed and Idriss (Seed HB, Idriss IM (1969) Report No. EERC 70–10, Earthquake Research Center, University of
California, Berkeley, California) which accounts for the modulus and damping degradation using a linear visco-elastic model.
A comparison of the results in the linear and the equivalent linear cases, for a magnitude 6.0 earthquake, shows that the
account for the equivalent linear behaviour of the soil significantly reduces the amplification level, especially at frequencies
higher than the fundamental resonance frequency of the site. In the case of site effects or microzonation studies devoted
to produce design spectra for engineering structures, this can have a major impact on the associated results and costs, depending
on the frequency of interest for the considered structure. As a first application of the developed technique, 2D equivalent
linear Aki–Larner computations are used to perform the seismic microzonation study of the upper Rhone valley, in the Visp
area (Switzerland), a typical 2D alpine valley. These investigations made it possible to determine site specific spectra,
associated with different zones, to be used instead of the code spectra that do not take into account the local 2D amplification. 相似文献
1000.