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61.
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
62.
63.
The cold event 8200 years ago documented in oxygen isotope records of precipitation in Europe and Greenland 总被引:14,自引:0,他引:14
Stable oxygen isotope ratios of ostracod valves in Late Glacial and Holocene sediments of core AS 92-5 from deep lake Ammersee
(southern Germany) reflect variations of mean oxygen isotope ratios in past atmospheric precipitation. The record reconfirms
the strong similarity of climate evolution in Europe and Greenland during the last deglaciation. For the first time in Europe,
we find a 200-year-long negative δ18O-excursion, which is contemporaneous with the strongest negative δ18O-excursion in the Greenland ice around 8.2 ky before present. The 8.2 ky isotopic event on both sides of the North Atlantic
ocean is interpreted as a cold period, most probably induced by a perturbation of the North Atlantic thermohaline circulation.
We discuss two possible triggering mechanisms: (1) weak forcing (as proposed by Alley et al.), and (2) forcing by a strong
and sudden freshwater pulse from the collapse of the Hudson Ice Dome.
Received: 27 May 1997 / Accepted: 21 July 1997 相似文献
64.
65.
Graczyk Dariusz Pińskwar Iwona Kundzewicz Zbigniew W. Hov Øystein Førland Eirik J. Szwed Małgorzata Choryński Adam 《Theoretical and Applied Climatology》2017,129(1-2):459-471
Theoretical and Applied Climatology - On the basis of temperature observations at 60 meteorological stations in Poland, changes in the indices associated with the presence of extremely high air... 相似文献
66.
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
67.
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
68.
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
69.
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
70.