全文获取类型
收费全文 | 128篇 |
免费 | 9篇 |
专业分类
测绘学 | 2篇 |
大气科学 | 9篇 |
地球物理 | 29篇 |
地质学 | 26篇 |
海洋学 | 25篇 |
天文学 | 32篇 |
综合类 | 1篇 |
自然地理 | 13篇 |
出版年
2024年 | 1篇 |
2021年 | 1篇 |
2020年 | 4篇 |
2019年 | 3篇 |
2018年 | 3篇 |
2017年 | 3篇 |
2016年 | 3篇 |
2014年 | 3篇 |
2013年 | 4篇 |
2012年 | 3篇 |
2011年 | 5篇 |
2010年 | 1篇 |
2009年 | 7篇 |
2008年 | 2篇 |
2007年 | 2篇 |
2006年 | 5篇 |
2005年 | 4篇 |
2004年 | 4篇 |
2003年 | 5篇 |
2002年 | 7篇 |
2001年 | 3篇 |
2000年 | 3篇 |
1999年 | 1篇 |
1998年 | 1篇 |
1997年 | 3篇 |
1996年 | 8篇 |
1995年 | 9篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1992年 | 3篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 3篇 |
1981年 | 5篇 |
1980年 | 3篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1975年 | 4篇 |
1974年 | 3篇 |
1973年 | 2篇 |
1972年 | 1篇 |
1967年 | 1篇 |
1961年 | 1篇 |
排序方式: 共有137条查询结果,搜索用时 15 毫秒
71.
Multiple detachment levels and their control on fold styles in the compressional domain of the deepwater west Niger Delta 总被引:2,自引:0,他引:2
Sepribo E. Briggs Richard J. Davies† Joe A. Cartwright Richard Morgan‡ 《Basin Research》2006,18(4):435-450
We interpret recently acquired two‐dimensional (2D) and 3D seismic data from the contractional domain of the Tertiary deepwater west Niger Delta, which is an area of current hydrocarbon exploration and development to show that during its gravitational collapse, multiple detachments were active. Detachments are located within (1) what we herein refer to as the ‘Dahomey unit’, (2) the transition between the Agbada and Akata formations (Top Akata) and (3) the Akata formation. Seismic interpretation and quantitative measurements of fault displacements show that the utilisation of different detachments results in contrasting styles of thrust propagation and fold growth. Two geographical zones are defined. In zone A (NW sector of the study area), the stratigraphically shallowest Dahomey detachment is dominant and is associated with thrust truncated folds. In zone B (SE sector of the study area), a stratigraphically lower detachment approximately at the Agbada–Akata formation boundary is associated with thrust propagation folds. A third detachment, within the Akata formation, is locally developed and is also associated with thrust propagation folds. The different deformational histories are probably related to the mechanical stratigraphy and the pore‐pressure characteristics of the succession. 相似文献
72.
73.
Göğüş E Woods PM Kouveliotou C van Paradijs J Briggs MS Duncan RC Thompson C 《The Astrophysical journal》2000,532(2):L121-L124
We present statistics of SGR 1806-20 bursts, combining 290 events detected with the Rossi X-Ray Timing Explorer/Proportional Counter Array, 111 events detected with the Burst and Transient Source Experiment, and 134 events detected with the International Cometary Explorer. We find that the fluence distribution of bursts observed with each instrument are well described by power laws with indices 1.43, 1.76, and 1.67, respectively. The distribution of time intervals between successive bursts from SGR 1806-20 is described by a lognormal function with a peak at 103 s. There is no correlation between the burst intensity and either the waiting times until the next burst or the time elapsed since the previous burst. In all these statistical properties, SGR 1806-20 bursts resemble a self-organized critical system, similar to earthquakes and solar flares. Our results thus support the hypothesis that the energy source for soft gamma repeater bursts is crustquakes due to the evolving, strong magnetic field of the neutron star, rather than any accretion or nuclear power. 相似文献
74.
Near-surface sediment geoacoustic and physical properties were measured in gas-rich, muddy sediments of Eckernförde Bay, Baltic Sea, and in hard-packed, sandy sediments of the northeastern Gulf of Mexico. Values of compressional and shear wave velocity are much lower in muddy compared to sandy sediments. The spatial and temporal variability of sediment physical and geoacoustic properties and, as a consequence, the scattering and propagation of high-frequency acoustic waves are primarily related to the presence and absence of free methane gas bubbles at the muddy site and to the abundance and distribution of shell material on sandy sediments. 相似文献
75.
Shallow-water bottom reverberation measurements 总被引:2,自引:0,他引:2
Stanic S. Goodman R.R. Briggs K.B. Chotiros N.P. Kennedy E.T. 《Oceanic Engineering, IEEE Journal of》1998,23(3):203-210
High-frequency bottom reverberation measurements were made at an experimental site in the Gulf of Mexico. The acoustic data were taken as a function of frequency (40-180 kHz) and grazing angle (40-33°). The measured acoustic reverberation results are compared to predictions made by models developed by Jackson et al. (1986, 1996) and Boyle and Chotiros (1995). The models used inputs from the analysis of sediment cores and stereophotography. The model predictions show differences from each other and from the data. The results show reverberation-level variabilities as a function of frequency that cannot be accurately predicted by these models 相似文献
76.
Improved Vertical Streambed Flux Estimation Using Multiple Diurnal Temperature Methods in Series
下载免费PDF全文
![点击此处可从《Ground water》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Analytical solutions that use diurnal temperature signals to estimate vertical fluxes between groundwater and surface water based on either amplitude ratios (Ar) or phase shifts (Δ?) produce results that rarely agree. Analytical solutions that simultaneously utilize Ar and Δ? within a single solution have more recently been derived, decreasing uncertainty in flux estimates in some applications. Benefits of combined (ArΔ?) methods also include that thermal diffusivity and sensor spacing can be calculated. However, poor identification of either Ar or Δ? from raw temperature signals can lead to erratic parameter estimates from ArΔ? methods. An add‐on program for VFLUX 2 is presented to address this issue. Using thermal diffusivity selected from an ArΔ? method during a reliable time period, fluxes are recalculated using an Ar method. This approach maximizes the benefits of the Ar and ArΔ? methods. Additionally, sensor spacing calculations can be used to identify periods with unreliable flux estimates, or to assess streambed scour. Using synthetic and field examples, the use of these solutions in series was particularly useful for gaining conditions where fluxes exceeded 1 m/d. 相似文献
77.
78.
K. R. Briggs J. P. Pye R. D. Jeffries E. J. Totten 《Monthly notices of the Royal Astronomical Society》2000,319(3):826-836
Using deep exposures (∼105 s) with the ROSAT High Resolution Imager, we have performed flux-limited surveys for X-ray sources in the vicinity of the Hyades-age open stellar clusters NGC 6633 and IC 4756, detecting 31 and 13 sources, respectively. Our primary aim is to search for so-far unrecognized cluster members. We propose identifications or classifications (cluster member, field star, extragalactic field object) for the X-ray sources, based on published membership lists, and on X-ray:optical flux ratios and optical colour–magnitude diagrams. Results of simulating the expected X-ray-emitting source populations are compared with the ROSAT measurements and with the expected capabilities of the XMM mission. The simulations provide a novel method of comparing the activity levels of NGC 6633 and IC 4756 with that of the Hyades. The measurements and simulations confirm that cluster members are the major class of X-ray emitter in these fields at flux levels (0.1–2.4 keV), contributing ∼40 per cent of the total X-ray sources. We find six possible new members in NGC 6633 and four candidates in IC 4756; all require further observation to establish membership probability. 相似文献
79.
J.A. Briggs D.A. Brain M.L. Cartwright J.P. Eastwood J.S. Halekas 《Planetary and Space Science》2011,59(13):1498-1505
Using minimum variance analysis of the circular mapping data from the Mars Global Surveyor (MGS) spacecraft during four selected weeks of observation, we identify 360 magnetic field structures in the Martian topside ionosphere with characteristic signatures of flux ropes. Physical parameters including size, peak field strength, helicity, orientation, and external conditions at the time of each observation are compiled for the events in each population. We observe that Martian flux ropes typically have a peak field amplitude of ∼15 nT and a diameter of ∼80–100 km assuming they are stationary. Flux ropes tend to be aligned approximately parallel to the planetary surface, and perpendicular to the direction from which the solar wind flows. They are more frequently observed during times of low solar wind pressure, but do not show a clear preference for a particular Interplanetary Magnetic Field (IMF) draping direction. Flux rope characteristics of peak field amplitude, diameter, and helicity vary with solar zenith angle. Amplitudes tend to be higher during periods of high solar wind pressure. The events are sorted into three populations based on the location at which they were observed, possibly corresponding to distinct formation mechanisms. Flux ropes observed in eclipse tend to have smaller peak amplitudes and are larger than those observed in sunlight, and are less likely to be oriented parallel to the planetary surface. Proximity to crustal fields does not appear to influence the characteristics of flux ropes observed at the 400 km spacecraft altitude. The frequent observation of flux rope structures near Mars in a variety of locations suggests that the low-altitude plasma environment is quite dynamic, with magnetic shear playing a prominent role in determining magnetic field structure near the planet. 相似文献
80.
Derek E.G. Briggs 《Geology Today》2014,30(6):227-231
Adolf (Dolf) Seilacher, who died earlier this year at the age of 89, was a major figure in palaeontology on both sides of the Atlantic. His interests were diverse, including trace fossils, the processes involved in exceptional preservation, and the evolution of invertebrate morphology. But it is for his views on the nature of the extraordinary fossils of the Ediacaran that he is perhaps best known. His ideas—compelling and provocative—will continue to stimulate research for years to come, not least through the wide use of his terminology (e.g. Lagerstätten, morphodynamics, constructional morphology, vendobiont). 相似文献