全文获取类型
收费全文 | 668篇 |
免费 | 30篇 |
国内免费 | 5篇 |
专业分类
测绘学 | 15篇 |
大气科学 | 29篇 |
地球物理 | 185篇 |
地质学 | 285篇 |
海洋学 | 50篇 |
天文学 | 111篇 |
综合类 | 2篇 |
自然地理 | 26篇 |
出版年
2022年 | 5篇 |
2021年 | 12篇 |
2020年 | 12篇 |
2019年 | 19篇 |
2018年 | 21篇 |
2017年 | 24篇 |
2016年 | 29篇 |
2015年 | 14篇 |
2014年 | 29篇 |
2013年 | 34篇 |
2012年 | 24篇 |
2011年 | 44篇 |
2010年 | 26篇 |
2009年 | 40篇 |
2008年 | 37篇 |
2007年 | 34篇 |
2006年 | 35篇 |
2005年 | 21篇 |
2004年 | 25篇 |
2003年 | 16篇 |
2002年 | 15篇 |
2001年 | 8篇 |
2000年 | 12篇 |
1999年 | 8篇 |
1998年 | 9篇 |
1997年 | 10篇 |
1996年 | 6篇 |
1995年 | 5篇 |
1994年 | 6篇 |
1993年 | 3篇 |
1992年 | 6篇 |
1991年 | 4篇 |
1990年 | 6篇 |
1989年 | 4篇 |
1988年 | 5篇 |
1987年 | 3篇 |
1986年 | 6篇 |
1985年 | 6篇 |
1984年 | 12篇 |
1983年 | 5篇 |
1982年 | 5篇 |
1981年 | 5篇 |
1979年 | 3篇 |
1976年 | 5篇 |
1971年 | 3篇 |
1970年 | 4篇 |
1967年 | 2篇 |
1964年 | 2篇 |
1956年 | 2篇 |
1920年 | 2篇 |
排序方式: 共有703条查询结果,搜索用时 31 毫秒
591.
592.
S. Covino E. Molinari P. Bruno M. Cecconi P. Conconi P. D'Avanzo L. di Fabrizio D. Fugazza M. Giarrusso E. Giro F. Leone V. Lorenzi S. Scuderi 《Astronomische Nachrichten》2014,335(2):117-123
We describe a new polarimetric facility available at the Istituto Nazionale di AstroFisica / Telescopio Nazionale Galileo at La Palma, Canary islands. This facility, PAOLO (Polarimetric Add‐On for the LRS Optics), is located at a Nasmyth focus of an alt‐az telescope and requires a specific modeling in order to remove the time‐ and pointing position‐dependent instrumental polarization. We also describe the opto‐mechanical structure of the instrument and its calibration and present early examples of applications. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
593.
Zoltan Balog Thomas Müller Markus Nielbock Bruno Altieri Ulrich Klaas Joris Blommaert Hendrik Linz Dieter Lutz Attila Moór Nicolas Billot Marc Sauvage Koryo Okumura 《Experimental Astronomy》2014,37(2):129-160
This paper provides an overview of the PACS photometer flux calibration concept, in particular for the principal observation mode, the scan map. The absolute flux calibration is tied to the photospheric models of five fiducial stellar standards (α Boo, α Cet, α Tau, β And, γ Dra). The data processing steps to arrive at a consistent and homogeneous calibration are outlined. In the current state the relative photometric accuracy is ~2 % in all bands. Starting from the present calibration status, the characterization and correction for instrumental effects affecting the relative calibration accuracy is described and an outlook for the final achievable calibration numbers is given. After including all the correction for the instrumental effects, the relative photometric calibration accuracy (repeatability) will be as good as 0.5 % in the blue and green band and 2 % in the red band. This excellent calibration starts to reveal possible inconsistencies between the models of the K-type and the M-type stellar calibrators. The absolute calibration accuracy is therefore mainly limited by the 5 % uncertainty of the celestial standard models in all three bands. The PACS bolometer response was extremely stable over the entire Herschel mission and a single, time-independent response calibration file is sufficient for the processing and calibration of the science observations. The dedicated measurements of the internal calibration sources were needed only to characterize secondary effects. No aging effects of the bolometer or the filters have been found. Also, we found no signs of filter leaks. The PACS photometric system is very well characterized with a constant energy spectrum νF ν = λF λ = const as a reference. Colour corrections for a wide range of sources SEDs are determined and tabulated. 相似文献
594.
595.
596.
Abstract A reflectivity‐rainfall rate (Z‐R) relationship is derived from Carvel radar and Edmonton rain gauge measurements. Our analysis indicates that the traditional point‐by‐point comparison method is not accurate for Alberta summertime precipitation due to timing errors in fast moving convective storms. The Window Probability Matching Method (WPMM) was superior and provided a robust Z‐R relationship in the form of Z = 32.5 R1.65. 相似文献
597.
Aurélia Mouret Pierre Anschutz Pascal Lecroart Gwénaëlle Chaillou Christelle Hyacinthe Jonathan Deborde Frans J. Jorissen Bruno Deflandre Sabine Schmidt Jean-Marie Jouanneau 《Geo-Marine Letters》2009,29(3):133-149
Manganese is a major redox reactive element of benthic metabolism. We have built a database of existing knowledge on the benthic
geochemistry of Mn in the Bay of Biscay, in order to comprehensively assess the behaviour of Mn in a variety of environments
during early diagenesis. The database contains vertical profiles of particulate and dissolved Mn species of 59 cores collected
during 17 cruises between 1997 and 2006 at nine stations positioned between 140 and 4,800 m water depths. At all studied stations,
Mn species follow the conventional distribution, where Mn(III,IV) species are enriched in the oxic layer, and dissolved Mn
is present in the anoxic sediments. A minor part of Mn-oxides originates from sedimenting particles. The major part is of
diagenetic origin, and derives from the oxidation of upward-diffusing dissolved Mn(II). Mn-oxide inventories are higher at
the deeper stations than at the shallower ones. This difference cannot be attributed to different sources of sedimenting particles,
but it must depend on sedimentation rate and diagenetic processes. At depth, dissolved Mn(II) concentrations are constant.
This probably reflects equilibrium with an authigenic Mn(II) phase, which is the ultimate phase into which Mn is fossilized.
The Mn content of deeper anoxic sediments is similarly low in all the cores studied, associated with corresponding trends
of Mn content in sedimenting particles of the Bay of Biscay. Bioturbation, rather than redox oscillations, can convey Mn(III,IV)
species downwards into the anoxic sediments where they are reduced, associated with a peak of dissolved Mn. Because dissolved
Mn(II) is re-oxidized when it diffuses towards the oxic layer, the inventory of the diagenetic Mn(III,IV) phase remains at
steady state, especially at stations where the oxic layer is thick. It then becomes possible to calculate the residence time
of diagenetic Mn(III,IV) particles within the oxic layer, using the upward-directed flux of pore water Mn(II). By applying
this residence time to the accumulation of sediments within the oxic layer, we obtain the sediment mass accumulation rate.
The values calculated for the sediments of the Bay of Biscay fit well with accumulation rates obtained from radionuclides
or sediment traps. The method has also been validated with data collected in other marine sedimentary environments.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
598.
The Gold Coast sandy beaches of Queensland (Australia) are exposed to energetic wave conditions. Storms, particularly tropical
cyclones, have a high potential of destruction. The Gold Coast has not experienced excessive erosive events over the past
30 years. However, some climate indicators suggest that cyclone frequency is likely to increase in response to global climate
change within the near future. Over a 2-month period in early 2006, beach surveys were undertaken with a theodolite total
station at four different sites. Offshore wave conditions were provided by SWAN regional wave modelling. During this study,
the Gold Coast was exposed to three major storms, the first one being the second most energetic over the past 30 years. Results
show a substantial variability of the beach response to these events along the Gold Coast, and that engineering structures
do not have marked effects. Easterly swells have the greatest impact on the Gold Coast sub-aerial beach morphology. When low
wave-energy conditions prevail, the southern Gold Coast beaches recover more quickly than the northern ones, as they are sheltered
from high SE waves and draw advantage from the artificial sand bypassing system. Nevertheless, the data show that the Gold
Coast beaches are exceedingly fragile. For instance, the early March decadal event considerably weakened the beaches, which
resulted in surprisingly high erosion rates all along the Gold Coast during the two following annual wave events. This study
suggests that the Gold Coast beaches would not be able to withstand the impact of an increased frequency of extreme events
similar in scale to those of 1967. 相似文献
599.
砂质海滩是最变化莫测和脆弱的海岸带类型之一。众所周知,海滩在高能环境中会被侵蚀,但海滩上不同位置点对于极端事件的抵御能力则大不相同。而且,侵蚀速率通常受控于海滩状况、机械结构和前期补给。 相似文献
600.
Seismic reliability‐based ductility demand evaluation for inelastic base‐isolated structures with friction pendulum devices 下载免费PDF全文
The aim of this work is to propose seismic reliability‐based relationships between the strength reduction factors and the displacement ductility demand of nonlinear structural systems equipped with friction pendulum isolators (FPS) depending on the structural properties. The isolated structures are described by employing an equivalent 2dof model characterized by a perfectly elastoplastic rule to account for the inelastic response of the superstructure, whereas, the FPS behavior is described by a velocity‐dependent model. An extensive parametric study is carried out encompassing a wide range of elastic and inelastic building properties, different seismic intensity levels and considering the friction coefficient as a random variable. Defined a set of natural seismic records and scaled to the seismic intensity corresponding to life safety limit state for L'Aquila site (Italy) according to NTC08, the inelastic characteristics of the superstructures are designed as the ratio between the average elastic responses and increasing strength reduction factors. Incremental dynamic analyses (IDAs) are developed to evaluate the seismic fragility curves of both the inelastic superstructure and the isolation level assuming different values of the corresponding limit states. Integrating the fragility curves with the seismic hazard curves related to L'Aquila site (Italy), the reliability curves of the equivalent inelastic base‐isolated structural systems, with a design life of 50 years, are derived proposing seismic reliability‐based regression expressions between the displacement ductility demand and the strength reduction factors for the superstructure as well as seismic reliability‐based design (SRBD) abacuses useful to define the FPS properties. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献