全文获取类型
收费全文 | 350篇 |
免费 | 21篇 |
国内免费 | 12篇 |
专业分类
测绘学 | 23篇 |
大气科学 | 53篇 |
地球物理 | 92篇 |
地质学 | 91篇 |
海洋学 | 81篇 |
天文学 | 20篇 |
综合类 | 8篇 |
自然地理 | 15篇 |
出版年
2022年 | 2篇 |
2021年 | 9篇 |
2020年 | 6篇 |
2019年 | 3篇 |
2018年 | 11篇 |
2017年 | 7篇 |
2016年 | 13篇 |
2015年 | 13篇 |
2014年 | 10篇 |
2013年 | 17篇 |
2012年 | 16篇 |
2011年 | 20篇 |
2010年 | 17篇 |
2009年 | 20篇 |
2008年 | 24篇 |
2007年 | 21篇 |
2006年 | 11篇 |
2005年 | 10篇 |
2004年 | 15篇 |
2003年 | 12篇 |
2002年 | 13篇 |
2001年 | 9篇 |
2000年 | 8篇 |
1999年 | 5篇 |
1998年 | 8篇 |
1997年 | 4篇 |
1996年 | 4篇 |
1995年 | 5篇 |
1994年 | 5篇 |
1993年 | 3篇 |
1992年 | 5篇 |
1990年 | 3篇 |
1989年 | 3篇 |
1987年 | 2篇 |
1986年 | 3篇 |
1985年 | 2篇 |
1984年 | 4篇 |
1983年 | 4篇 |
1982年 | 3篇 |
1981年 | 2篇 |
1980年 | 3篇 |
1979年 | 7篇 |
1978年 | 4篇 |
1976年 | 3篇 |
1974年 | 2篇 |
1959年 | 1篇 |
1954年 | 1篇 |
1953年 | 1篇 |
1942年 | 1篇 |
1936年 | 1篇 |
排序方式: 共有383条查询结果,搜索用时 39 毫秒
21.
Vindell Hsu Charles E. Helsley Eduard Berg David A. Novelo-Casanova 《Pure and Applied Geophysics》1984,122(6):878-893
A close correlation in spatial distribution of local seismic activity and energy release patterns before and after the 1979 Petatlan, Mexico earthquake suggests heterogeneity within the fault plane of this major low-angle thrust event associated with subduction along the Middle America Trench. A simple two-asperity model is proposed to account for the complexity. Foreshocks and aftershocks of the neighboring 1981 Playa Azul earthquake showed a similar pattern. As both events occurred at the junction of the Orozco Fracture Zone and the Middle America Trench, we speculate that the observed complex fault plane is caused by subduction of the rugged ocean floor of the Orozco Fracture Zone. Short-term precursory seismicity prior to the Petatlan earthquake can be explained by using the asperity model and migration of a slip front from the south-east to the north-west across the main shock source region. 相似文献
22.
S.A. Hsu 《Dynamics of Atmospheres and Oceans》1984,8(3-4)
Field experiments have shown that an internal boundary layer (IBL) can develop when the wind blows perpendicularly from the cold-water side of a warm oceanic current to the warmer side. The height of this IBL downwind from the thermal front as computed by an equation originally developed by Venkatram is in excellent agreement with observations. 相似文献
23.
The major advantage of using either the analytic‐signal or the Euler‐deconvolution technique is that we can determine magnetic‐source locations and depths independently of the ambient earth magnetic parameters. In this study, we propose adopting a joint analysis of the analytic signal and Euler deconvolution to estimate the parameters of 2D magnetic sources. The results can avoid solution bias from an inappropriate magnetic datum level and can determine the horizontal locations, depths, structural types (indices), magnetization contrasts and/or structural dips. We have demonstrated the feasibility of the proposed method on 2D synthetic models, such as magnetic contacts (faults), thin dikes and cylinders. However, the method fails to solve the parameters of magnetic sources if there is severe interference between the anomalies of two adjacent magnetic sources. 相似文献
24.
Prediction of surface horizontal displacements, and gravity and tilt changes caused by filling the Three Gorges Reservoir 总被引:11,自引:0,他引:11
Horizontal displacements, and gravity and tilt changes induced by filling the Three Gorges Reservoir are modeled using elastic
loading Green functions. When the water surface reaches its highest level, the effects become maximum on the reservoir banks.
The longitudinal and latitudinal components of the horizontal displacements reach −8.2 and 7.7 mm respectively, gravity is
increased by up to 3.4 mGal, and the prime vertical and meridian components of the tilt changes are −7.8 and −17.5 arcseconds
respectively. Accordingly, the filling of the reservoir will influence values observed from global positioning system (GPS),
gravimetry and tilt measurements in the area. The results given can be used to provide important corrections for extracting
earthquake-related signals from observed data.
Received: 19 January 2001 / Accepted: 3 September 2001 相似文献
25.
The stability of merwinite (Mw) and its equivalent assemblages, akermanite (Ak)+calcite (Cc), diopside (Di)+calcite, and wollastonite (Wo)+monticellite (Mc)+calcite was determined at T=500–900° C and P
f=0.5–2.0 kbar under H2O–CO2 fluid conditions with X
CO
2=0.5, 0.1, 0.05, and 0.02. Merwinite is stable at P
f=0.5 kbar with T>700° C and X
CO
2<0.1. At P
f=2.0 kbar, the assemblage Di+Cc replaces merwinite at all T and X
CO
2 conditions. At intermediate P
f=1 kbar, the assemblage Ak+Cc is stable above 707° C and Wo+Mc+Cc is stable below 707° C. The univariant curve for the reaction Di+Cc=Wo+Mc+CO2 is almost parallel to the T axis and shifts to low P
f with increasing X
CO
2, with the assemblage Di+Cc on the high-P
f side. The implications of the experimental results in regard to contact metamorphism of limestone are discussed using the aureole at Crestmore, California as an example. 相似文献
26.
较详细地介绍了LSQRD(Least Square QR Decomposition) 反演方法以及“检测版”分辨分析方法,并举实例检验其应用。对于大型稀疏方程组的求解,LSQRD 是一种内存需求小、计算效率高和抗噪能力较强的算法。“检测版”试验表明,LSQRD也可以对迭代解进行有效的可靠性估计,以指导对反演结果的利用。 相似文献
27.
Wavelet filter analysis of atmospheric pressure effects in the long-period seismic mode band 总被引:2,自引:0,他引:2
The importance of the reduction of atmospheric pressure effects becomes very clear when investigating seismic normal-mode spectra below 1.5 mHz. The usual simple correction method consists in subtracting a term converted from local atmospheric pressure (pressure multiplied by a frequency-independent admittance) from the gravity record in time domain. Thus, estimating an efficient admittance is the key for an improved correction. Band-pass filters derived from dyadic orthogonal wavelet transform, having narrow pass-bands with good frequency response but without Gibbs phenomenon and causing no phase lag, are very helpful to estimate an efficient admittance, which is both time and frequency-dependent. Processing of high quality superconducting gravimeter (SG) records for the great Sumatra earthquake (Mw = 9.3, Dec 26, 2004) with wavelet filters reveal the three very well resolved splitting singlets of overtone 2S1 with a single gravity record after correction with time-dependent and frequency-dependent admittances. We also observe all coupled toroidal modes below 1.5 mHz, except 0T5, 0T7 and 1T1, with good signal-to-noise ratio (SNR); moreover, toroidal modes 1T2 and 1T3 are for the first time unambiguously revealed in vertical components. 相似文献
28.
Observed pollutants are of both primary and secondary origins, influenced by local topography and meteorology. Identifying
sources and relative contribution often require vast detailed data collection and complicated models. This study applied a
statistical time series analysis to two selected pollution events, spring and fall, at two sites in northern Taiwan. Vector
moving average representations were used to quantitatively examine relationships among chemical pollutants and estimate their
lifetimes. Results from impulse responses show that wind direction change alters the characteristic of pollution observed
in opposite sites of Taipei City, from chemical dominant system to transport dominant one and vice versa. Chemicals are clearly
separated into photochemical pollutants and primary pollutants. Results pointed out that Taipei City is the major source of
photochemical smog, but not these primary pollutants. Derived chemical lifetimes at same location vary from 20% to four times
under different meteorological condition. Estimated concentrations of hydroxyl radical range between 2 to 8 × 107 cm−3. Photochemical pollutants are responsible for parts of PM10 collected in both station observed. Oxidation of SO2 is only important in PM10 observed at one station. This study provides a simpler tool to derive information usually from
complex models, therefore, is suitable as complement in decision-making process. 相似文献
29.
水准椭球的纬向密度分布 总被引:9,自引:1,他引:8
本文推导了旋转椭球极点重力与赤道重力的密度积分公式。按照1980大地参考系统及水准椭球的“极点重力条件”和“赤道重力条件”,从数学上证明了地球的“赤道径向平均密度”大于“极点径向平均密度”,并给出了水准椭球纬向密度分布的估算公式;进而提出了“地球的径向平均密度按纬向正常分布”的假说。 相似文献
30.
A comparison of estimated and calculated effective porosity 总被引:1,自引:1,他引:0
Daniel B. Stephens Kuo-Chin Hsu Mark A. Prieksat Mark D. Ankeny Neil Blandford Tracy L. Roth James A. Kelsey Julia R. Whitworth 《Hydrogeology Journal》1998,6(1):156-165
Effective porosity in solute-transport analyses is usually estimated rather than calculated from tracer tests in the field
or laboratory. Calculated values of effective porosity in the laboratory on three different textured samples were compared
to estimates derived from particle-size distributions and soil–water characteristic curves. The agreement was poor and it
seems that no clear relationships exist between effective porosity calculated from laboratory tracer tests and effective porosity
estimated from particle-size distributions and soil–water characteristic curves. A field tracer test in a sand-and-gravel
aquifer produced a calculated effective porosity of approximately 0.17. By comparison, estimates of effective porosity from
textural data, moisture retention, and published values were approximately 50–90% greater than the field calibrated value.
Thus, estimation of effective porosity for chemical transport is highly dependent on the chosen transport model and is best
obtained by laboratory or field tracer tests.
Received, March 1997 · Revised, August 1997 · Accepted, August 1997 相似文献