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51.
Hydro carbon fields beyond the shelf break are presently being explored and developed, which has increased the scientific
focus in this area. Measurements from the slopes reveal large variability in temperature and velocity, and some of the observed
events are due to interactions between large-amplitude oscillations of the thermocline and the topography. The present study
focuses on the strong currents that are generated near the seabed during shoaling and breaking of internal waves along shelf
slopes. The parameter regime used is similar to the one for the Nordic Seas. The results show that, during shoaling of large
internal waves along (gentle) slopes, the energy is transferred towards smaller scales and strong velocities (over 1 m s − 1) can be generated. To resolve all scales involved is still not feasible, and therefore, the model results are sensitive to
the grid size and the subgrid scale closure. 相似文献
52.
53.
Öivind Hauge 《Solar physics》1970,11(1):17-21
Europium has two stable isotopes, Eu 151 and Eu 153. The high isotope shift and the different hyperfine splitting of the energy levels of the two isotopes make it possible to study the isotope ratio by an analysis of the spectral line profiles. From five spectral lines the solar isotope ratio is found to be equal to the terrestrial ratio within an error limit of about 10 %. 相似文献
54.
Numerical simulation of upwelling currents in pockmarks,and data from the Inner Oslofjord,Norway 总被引:5,自引:3,他引:2
The deflection of oceanic or tidal currents into pockmarks has been studied by both general three-dimensional computational
fluid dynamics simulations and acoustic measurements in a number of pockmarks in the Inner Oslofjord, Norway. The modeling
demonstrates upstream convergence of flow lines, followed by upwelling over the pockmark. This upwelling is an effect of deflected
regional currents, not of expulsion of fluids or gas from the seafloor, and is sufficiently strong to prevent the settling
of fine particles. The field measurements, although noisy at low vertical velocities, are consistent with the hypothesis of
upwelling. The reduction in sedimentation rate inferred over the pockmarks (relative to that of the flat surrounding seabed)
can explain the maintenance, or even deepening of pockmarks in the absence of fluid or gas seepage. The current pattern may
also have consequences for the marine biology of pockmarks. 相似文献
55.
F. RIIS E. KALLESON H. DYPVIK S. O. KRØGLI O. NILSEN 《Meteoritics & planetary science》2011,46(5):748-761
Abstract– The Ritland structure is a newly discovered impact structure, which is located in southwestern Norway. The structure is the remnant of a simple crater 2.5 km in diameter and 350 m deep, which was excavated in Precambrian gneissic rocks. The crater was filled by sediments in Cambrian times and covered by thrust nappes of the Caledonian orogen in the Silurian–Devonian. Several succeeding events of uplift, erosion, and finally the Pleistocene glaciations, disclosed this well‐preserved structure. The erosion has exposed brecciated rocks of the original crater floor overlain by a thin layer of melt‐bearing rocks and postimpact crater‐filling breccias, sandstones, and shales. Quartz grains with planar deformation features occur frequently within the melt‐bearing unit, confirming the impact origin of the structure. The good exposures of infilling sediments have allowed a detailed reconstruction of the original crater morphology and its infilling history based on geological field mapping. 相似文献
56.
A. Ahmad C.S. Jeffery J.-E. Solheim R. Østensen 《Astrophysics and Space Science》2004,291(3-4):435-439
We present results of the pulsation monitoring of helium-rich subdwarf B (He-sdB) stars using high-speed differential photometry observations made with the SAAO (1.0m), NOT (2.6m) and the IAC80 (0.8m) telescopes. Although we did not find a pulsator in our sample of He-sdB stars, some of the stars show hints of pulsations which need further investigation. 相似文献
57.
Elizabeth M. Green Keith Callerame Ivo R. Seitenzahl Brooke A. White Elaina A. Hyde Melissa Giovanni Mike Reed Gilles Fontaine Roy Østensen 《Astrophysics and Space Science》2003,284(1):65-68
During the course of an ongoing CCD monitoring program to investigate low-level light variations in subdwarf B (sdB) stars, weserendipitously discovered a new class of multimode pulsators withperiods of the order of an hour. These periods are a factor of tenlonger than those of previously known multimode sdB pulsators (EC14026 stars), implying the new pulsations are due to gravity modes rather than pressure modes. The iron opacity instability that drives the short period EC 14026 stars is effective in hot sdB's. Thelong period pulsators are found only among cooler sdB stars, wherethey are surprisingly common. The mechanism responsible for excitingthe deeper g-modes in cool sdB's is currently unknown, but thetemperature and gravity range in which these stars occur must be animportant clue. We present the first observational results for thisnew class of pulsating sdB stars, and discuss some possible implications. 相似文献
58.
C.A. Karl U. Heber H. Drechsel R. Napiwotzki M. Altmann R. Østensen S. Folkes J.E. Solheim O. Cordes B. Voss D. Koester 《Astrophysics and Space Science》2004,291(3-4):283-289
We report the discovery of a binary, HS 2233 + 3927, consisting of an sdB star with a faint companion. From its lightcurve the orbital period of 14,844 s, the mass ratio, the inclination, and other system parameters are derived. The companion does not contribute to the optical light of the system except through a strong reflection effect. The semi-amplitude of the radial velocity curve K 1= 89.6 km/s?1 and a mass function of f(m) = 0.013 M ⊙ are determined. A preliminary spectroscopic analysis of the blue spectra using NLTE model atmospheres results in Teff= 36 500 K, log g= 5.70, and log(n He/n H) =?2.15. These parameters are typical for sdB stars, the companion is probably an M dwarf. 相似文献
59.
60.
J.-E. Solheim R. Østensen R. Silvotti U. Heber 《Astrophysics and Space Science》2004,291(3-4):419-426
A search program for pulsating sdBs was conducted with the Nordic Optical Telescope in the years 1999–2001. Possible candidates were selected from the HS, HE and PG surveys. In total 10 pulsators were found, some quite bright. In addition one more was found from a small SDSS sample observed in Oct. 2002. 相似文献