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21.
1999年11月29日岫岩5.4级地震序列震源参数测定及标度关系分析 总被引:1,自引:1,他引:0
根据Andrews谱积分的方法, 采用近震源Brune圆盘模型, 测定了1999年11月29日辽宁岫岩MS5.4地震序列的震源参数。 结果表明, 得到辐射能量与震级的关系, 与古登堡-里克特给出的关系基本一致; 地震矩与震级的关系中斜率和截距都小于陈培善等给出的全球结果; 视应力与震级呈半对数线性关系; 在双对数坐标下视应力随地震矩的增加而增加; 地震矩随拐角频率的7次方衰减, 在地震序列的不同阶段各参数的拟合关系斜率也不完全相同。 相似文献
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基于融合技术的结构性栅格时空数据平台的构建 总被引:6,自引:0,他引:6
时空数据融合是当前研究地理现象空间格局的数据存储、处理方法与有效途径。在构建国家资源环境时空数据平台过程中 ,我们设计了基于 1 km栅格单元的土地利用现状与变化数据库。这种时空数据表达方式的优点 :(1 )在保持面积信息不损失情况下明显减少了数据存储量 ,并且满足区域分析的空间尺度要求 ;(2 )便于多时间序列的数据存储与变化分析 ,以及变化专题信息提取与结果显示 ;(3)有利于区域土地利用变化环境背景与驱动力分析 ,可以实现与其他多源数据的有效融合 ;(4 )从小尺度到大尺度的空间尺度转换非常便利 ,在空间聚合的基础上能够快速实现从区域分析扩大至国家尺度、全球尺度的分析。 相似文献
24.
In this paper we consider an anisotropic scaling approach to understanding rock density and surface gravity which naturally
accounts for wide range variability and anomalies at all scales. This approach is empirically justified by the growing body
of evidence that geophysical fields including topography and density are scaling over wide range ranges. Theoretically it
is justified, since scale invariance is a (geo)dynamical symmetry principle which is expected to hold in the absence of symmetry
breaking mechanisms. Unfortunately, to date most scaling approaches have been self-similar, i.e., they have assumed not only
scale invariant but also isotropic dynamics. In contrast, most nonscaling approaches recognize the anisotropy (e.g., the strata),
but implicitly assume that the latter is independent of scale. In this paper, we argue that the dynamics are scaling but highly
anisotropic, i.e., with scale dependent differential anisotropy.
By using empirical density statistics in the crust and a statistical theory of high Prandtl number convection in the mantle,
we argue that
is a reasonable model for the 3-D spectrum (K is the horizontal wavevector and K is its modulus, k
z
is a vertical wavenumber), (s,H
z
) are fundamental exponents which we estimate as (5.3,3), (3,3) in the crust and mantle, respectively. We theoretically derive
expressions for the corresponding surface gravity spectrum. For scales smaller than ≈100 km, the anisotropic crust model of
the density (with flat top and bottom) using empirically determined vertical and horizontal density spectra is sufficient
to explain the (Bouguer) g
z
spectra. However, the crust thickness is highly variable and the crust-mantle density contrast is very large. By considering
isostatic equilibrium, and using global gravity and topography data, we show that this thickness variability is the dominant
contribution to the surface g
z
spectrum over the range ≈100–1000 km. Using estimates of mantle properties (viscosity, thermal conductivity, thermal expansion
coefficient, etc.), we show that the mantle contribution to the mean spectrum is strongest at ≈1000 km and is comparable to
the variable crust thickness contribution. Overall, we produce a model which is compatible with both the observed (horizontal
and vertical) density heterogeneity and surface gravity anomaly statistics over a range of meters to several thousand kilometers. 相似文献
25.
The scaling law linking the strength of the meridional overturning to the surface meridional temperature gradient is re-examined in two ocean general circulation models at coarse resolution in an idealised single-hemisphere setting. Two sets of results are presented, where the surface meridional temperature gradient is decreased either by increasing the northernmost temperature and keeping the equator temperature fixed, or by decreasing the equator temperature and keeping the northernmost temperature fixed. The maximum of the meridional overturning first increases and then decreases when the northernmost temperature is gradually increased, whereas the maximum overturning decreases monotonically when the equator temperature is decreased. No scaling law can be derived when the northernmost temperature is increased, whereas a 2/3 power law is found when the temperature is decreased at the equator. The behaviour of the overturning is strongly influenced by the vigour and, particularly, the spatial patterns of convection, which vary substantially between the two sets and which control the horizontal and vertical density gradients at high latitudes. 相似文献
26.
Kevin Housen 《Planetary and Space Science》2009,57(2):142-153
Laboratory impact experiments were performed to investigate the conditions that produce large-scale damage in rock targets. Aluminum cylinders (6.3 mm diameter) impacted basalt cylinders (69 mm diameter) at speeds ranging from 0.7 to 2.0 km/s. Diagnostics included measurements of the largest fragment mass, velocities of the largest remnant and large fragments ejected from the periphery of the target, and X-ray computed tomography imaging to inspect some of the impacted targets for internal damage. Significant damage to the target occurred when the kinetic energy per unit target mass exceeded roughly of the energy required for catastrophic shattering (where the target is reduced to one-half its original mass). Scaling laws based on a rate-dependent strength were developed that provide a basis for extrapolating the results to larger strength-dominated collisions. The threshold specific energy for widespread damage was found to scale with event size in the same manner as that for catastrophic shattering. Therefore, the factor of four difference between the two thresholds observed in the lab also applies to larger collisions. The scaling laws showed that for a sequence of collisions that are similar in that they produce the same ratio of largest fragment mass to original target mass, the fragment velocities decrease with increasing event size. As a result, rocky asteroids a couple hundred meters in diameter should retain their large ejecta fragments in a jumbled rubble-pile state. For somewhat larger bodies, the ejection velocities are sufficiently low that large fragments are essentially retained in place, possibly forming ordered “brick-pile” structures. 相似文献
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Sheng?YueEmail author Chun Yuan?Wang 《Stochastic Environmental Research and Risk Assessment (SERRA)》2004,18(5):291-305
Scaling properties of Canadian low flows, namely annual minimum mean 1-, 5- and 7-day flows, are evaluated across Canada and in its sub-climatic regions. Across the entire country, the log relationship between the kth product moments (PMs, E[Qik]) of low flows and drainage area (Ai) can be represented by: ln(E[Qik])=ak+bkln(Ai)and bk=k, with = 0.86, 0.94 and 0.93 for annual minimum mean 1-, 5- and 7-day flows, respectively. The log linear relationships between the kth probability weighted moments (PWMs, ) and Ai are ln()=ck+Hln(Ai), in which H is constant and is independent of k. The values of H are 0.87, 0.97, and 0.96 for annual minimum mean 1-, 5- and 7-day flows, respectively, which are almost the same as the values. The coefficients of variation (Cv) are almost independent of drainage area. These results demonstrate that Canadian low flows generally exhibit simple scaling and drainage area alone describes most of the variability in the moments of the low flows. Low flows in each of the sub-climatic regions also obey a simple scaling law. The values of , H and Cv are different in each region, which may stem from physiographical and climatological differences among these regions. The finding lays a basis for applying the index flood method to conduct regional low flow frequency analysis as simple scaling is equivalent to the index flood method.Acknowledgements The authors thank Prof. Thian Yew Gan of University of Alberta, Canada for providing additional pristine data sites for regions 4 and 10. A constructive comments provided by an anonymous reviewer improved the quality of the paper. 相似文献