全文获取类型
收费全文 | 403篇 |
免费 | 9篇 |
国内免费 | 4篇 |
专业分类
测绘学 | 17篇 |
大气科学 | 41篇 |
地球物理 | 86篇 |
地质学 | 125篇 |
海洋学 | 28篇 |
天文学 | 69篇 |
综合类 | 2篇 |
自然地理 | 48篇 |
出版年
2024年 | 5篇 |
2021年 | 4篇 |
2020年 | 3篇 |
2019年 | 5篇 |
2018年 | 13篇 |
2017年 | 5篇 |
2016年 | 9篇 |
2015年 | 8篇 |
2014年 | 15篇 |
2013年 | 16篇 |
2012年 | 17篇 |
2011年 | 18篇 |
2010年 | 4篇 |
2009年 | 11篇 |
2008年 | 10篇 |
2007年 | 15篇 |
2006年 | 22篇 |
2005年 | 14篇 |
2004年 | 8篇 |
2003年 | 6篇 |
2002年 | 17篇 |
2001年 | 13篇 |
2000年 | 6篇 |
1999年 | 8篇 |
1998年 | 14篇 |
1996年 | 6篇 |
1995年 | 3篇 |
1994年 | 6篇 |
1993年 | 5篇 |
1992年 | 7篇 |
1991年 | 10篇 |
1990年 | 7篇 |
1988年 | 8篇 |
1986年 | 6篇 |
1985年 | 4篇 |
1984年 | 8篇 |
1983年 | 4篇 |
1982年 | 3篇 |
1981年 | 5篇 |
1979年 | 3篇 |
1977年 | 4篇 |
1976年 | 3篇 |
1975年 | 4篇 |
1973年 | 5篇 |
1970年 | 4篇 |
1962年 | 4篇 |
1961年 | 3篇 |
1960年 | 4篇 |
1955年 | 3篇 |
1930年 | 2篇 |
排序方式: 共有416条查询结果,搜索用时 15 毫秒
51.
K. G. Strassmeier M. Weber T. Granzer L. Schanne J. Bartus I. Ilyin 《Astronomische Nachrichten》2014,335(9):904-934
We present continuous and time‐resolved R = 55 000 optical échelle spectroscopy of ε Aurigae from 2006–2013. Data were taken with the STELLA Echelle Spectrograph of the robotic STELLA facility at the Observatorio del Teide in Tenerife. Contemporaneous photometry with the Automatic Photoelectric Telescopes at Fairborn Observatory in Arizona is presented for the years 1996–2013. Spectroscopic observations started three years prior to the photometric eclipse and are still ongoing. A total of 474 high‐resolution échelle spectra are analyzed and made available in this paper. We identify 368 absorption lines of which 161 lines show the characteristic sharp disk lines during eclipse. Another 207 spectral lines appeared nearly unaffected by the eclipse. From spectrum synthesis, we obtained the supergiant atmospheric parameters Teff = 7395 ± 70 K, log g ≈ 1, and [Fe/H] = +0.02 ± 0.2 with ξt = 9 km s–1, ζRT = 13 km s–1, and v sin i = 28 ± 3 km s–1. The residual average line broadening expressed in km s–1 varies with a period of 62.6 ± 0.7 d, in particular at egress and after the eclipse. Two‐dimensional line‐profile periodograms show several periods, the strongest with ≈110 d evident in optically thin lines as well as in the Balmer lines. Center‐of‐intensity weighted radial velocities of individual spectral lines also show the 110‐d period but, again, additional shorter and longer periods are evident and are different in the Balmer lines. The two main spectroscopic Hα periods, ≈ 116 d from the line core and ≈ 150 d from the center‐of‐intensity radial velocities, appear at 102 d and 139 d in the photometry. The Hβ and Johnson V I photometry on the other hand shows two well‐defined and phase‐coherent periods of 77 d and 132 d. We conclude that Hα is contaminated by changes in the circumstellar environment while the Hβ and V I photometry stems predominantly from the non radial pulsations of the F0 supergiant. We isolate the disk‐rotation profile from 61 absorption lines and found that low disk eccentricity generally relates to low disk rotational velocity (but not always) while high disk eccentricity always relates to high velocity. There is also the general trend that the disk‐absorption in spectral lines with higher excitation potential comes from disk regions with higher eccentricity and thus also with higher rotational velocity. The dependency on transition probability is more complex and shows a bi‐modal trend. The outskirts of the disk is distributed asymmetrically around the disk and appears to have been built up mostly in a tail along the orbit behind the secondary. Our data show that this tail continues to eclipse the F0 Iab primary star even two years after the end of the photometric eclipse. High‐resolution spectra were also taken of the other, bona‐fide, visual‐binary components of ε Aur (ADS 3605BCDE). Only the C‐component, a K3‐4‐giant, appears at the same distance than ε Aur but its radial velocity is in disagreement with a bound orbit. The other components are a nearby (≈ 7 pc) cool DA white dwarf, a G8 dwarf, and a B9 supergiant, and not related to ε Aur. The cool white dwarf shows strong DIB lines that suggest the existence of a debris disk around this star. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
52.
Zsolt Kővári Katalin Oláh János Bartus Klaus G. Strassmeier Michael Weber Albert Washuettl John B. Rice Szilárd Csizmadia 《Astrophysics and Space Science》2006,304(1-4):375-377
Doppler images are presented for the RS CVn-type binary ζ And. Our upgraded Doppler imaging code TempMapε takes into account the distorted geometry of the primary giant component. On the maps several low latitude spots are restored with a temperature contrast of about 1000 K. Some weak polar features are also found. Cross-correlation of the consecutive Doppler-maps suggests solar-like differential surface rotation. 相似文献
53.
54.
E. J. Weber 《Solar physics》1970,14(2):480-488
The solutions of a radially symmetrical solar wind model with thermal conductivity are discussed in the neighborhood of the loci of the critical points, called the critical line, and at infinity. It is shown that for constant mass and total energy flux the conditions at infinity are related uniquely to the conditions at the critical line. Furthermore the requirement that the solution is continuous and has the proper behavior at infinity will determine uniquely one specific point on the critical line through which the solution has to pass.Operated by the Association of Universities for Research in Astronomy, Inc., under contract with the National Science Foundation. 相似文献
55.
Richard R. Weber 《Solar physics》1978,59(2):377-385
Flux density spectra have been determined for ninety-one simple type III solar bursts observed by the Goddard Space Flight Center radio astronomy experiment on the IMP-6 spacecraft during 1971 and 1972. Spectral peaks were found to occur at frequencies ranging from 44 kHz up to 2500 kHz. Half of the bursts peaked between 250 kHz and 900 kHz, corresponding to emission at solar distances of about 0.3 to 0.1 AU. Maximum burst flux density sometimes exceeds 10–14 W m–2 Hz–1. The primary factor controlling the spectral peak frequency of these bursts appears to be variation in intrinsic power radiated by the source as the exciter moves outward from the Sun, rather than radio propagation effects between the source and IMP-6. Thus, a burst spectrum strongly reflects the evolution of the properties of the exciting electron beam, and according to current theory, beam deceleration could help account for the observations. 相似文献
56.
57.
Multi-metal contaminant dynamics in temporarily flooded soil under sulfate limitation 总被引:3,自引:0,他引:3
Frank-Andreas Weber Andreas Voegelin Ruben Kretzschmar 《Geochimica et cosmochimica acta》2009,73(19):5513-5527
In many river basins, floodplain soils have accumulated a variety of metal contaminants, which might be released during periods of flooding. We investigated the dynamics of copper, cadmium, lead, zinc, and nickel in a contaminated freshwater floodplain soil under a realistic sulfate-limited flooding regime in microcosm experiments. We found that most contaminants were initially mobilized by processes driven by the reductive dissolution of Fe(III) and Mn(IV, III) (hydr)oxides. Subsequently, bacterial sulfate respiration resulted in the transformation of the entire available sulfate (2.3 mmol/kg) into chromous reducible sulfur (CRS). Cu K-edge X-ray absorption fine structure (XAFS) spectroscopy revealed that the soil Cu speciation changed from predominantly Cu(II) bound to soil organic matter (SOM) intermittently to 14% metallic Cu(0) and subsequently to 66% copper sulfide (CuxS). These CuxS precipitates accounted for most of the formed CRS, suggesting that CuxS was the dominant sulfide phase formed in the flooded soil. Sequential metal extractions, in agreement with CRS results, suggested that easily mobilizable Cd was completely and Pb partially sequestered in sulfide precipitates, controlling their dissolved concentrations to below detection limits. In contrast, Zn and Ni (as well as Fe) were hardly sequestered into sulfide phases, so that micromolar levels of dissolved Zn and Ni (and millimolar dissolved Fe(II)) persisted in the reduced soil. The finding that Cu, Cd, and Pb were sequestered (but hardly any Zn, Ni, and Fe) is consistent with the thermodynamically predicted sulfide ladder following the increasing solubility products of the respective metal sulfides. The observation that Cd and Pb were sequestered in sulfides despite the presence of remaining SOM-bound Cu(II) suggested that the kinetics of Cu(II) desorption, diffusion, and/or CuxS precipitation interfered with the sulfide ladder. We conclude that the dynamics of multiple metal contaminants are intimately coupled under sulfate limitation by the relative thermodynamic stabilities and formation kinetics of the respective metal sulfides. 相似文献
58.
A. Oliveira F. Rocha A. Rodrigues J. Jouanneau A. Dias O. Weber C. Gomes 《Progress in Oceanography》2002,52(2-4)
The Northern Iberian margin is a typical example of a continental margin subjected to seasonal highly energetic regime (waves and tides) and receiving inputs of continental sediments via riverine discharges. The principal goal of this study has been to use clay minerals as indicators of sedimentary dynamics in the open shelf system. The distributions of clay mineral in the top layer of the sedimentary cover are shown to be related to their continental sources, but also reflect the influences of winter storms and longshore currents in determining the pathways of sediment transport.The mineralogical composition of the material issuing from the rivers is very similar to the general mineralogical composition of the fine fractions of the seabed sediments. Those deposits that are directly influenced by riverine discharges have higher contents of kaolinite (>20%), whereas those that are not have higher contents of illite (>80%). The available data indicate no significant quantities of terrigenous particles are being discharged from the Spanish rias. Therefore, we conclude that physical processes are controlling the clay mineral distributions and that, despite contributions from the Minho River, the main source of fine detrital particles to the shelf region is the Douro River discharge. These particles settle on the middle shelf, below the 60 m isobath. During storm events these particles are re-suspended and advected northwards to the Galician shelf or into deeper domains. Thus the distributions of the clays indicate there is a net transport of fine sediments both northwards and off-shelf. 相似文献
59.
Our study deals with the correlations between the solar activity on the one hand and the solar irradiance above the Earth’s
atmosphere and at ground level on the other. We analyzed the combined ACRIM I+II time series of the total solar irradiance
(TSI), the Mauna Loa time series of terrestrial insolation data, and data of terrestrial cosmic ray fluxes. We find that the
correlation between the TSI and the sunspot number is strongly non-linear. We interpret this as the net balance between brightening
by faculae and darkening by sunspots where faculae dominate at low activity and sunspots dominate at high activity. Such a
behavior is hitherto known from stellar analogs of the Sun in a statistical manner. We perform the same analysis for the Mauna
Loa data of terrestrial insolation. Here we find that the linear relation between sunspot number and insolation shows more
than 1% rise in insolation by sunspot number variations which is much stronger than for the TSI. Our conclusion is that the
Earth atmosphere acts as an amplifier between space and ground, and that the amplification is probably controlled by solar
activity. We suspect the cosmic rays intensity as the link between solar activity and atmospheric transparency. A Fourier
analysis of the time series of insolation shows three dominant peaks: 10.5, 20.4, and 14.0 years. As a matter of fact, the
cosmic rays data show the same pattern of significant peaks: 10.7, 22.4, and 14.9 years. This analogy supports our idea that
the cosmic rays variation has influence on the transparency of the Earth atmosphere. 相似文献
60.
Maximilian Weber 《International Journal of Earth Sciences》1924,14(4):337-351
Ohne Zusammenfassung 相似文献