全文获取类型
收费全文 | 622篇 |
免费 | 39篇 |
国内免费 | 3篇 |
专业分类
测绘学 | 12篇 |
大气科学 | 35篇 |
地球物理 | 234篇 |
地质学 | 211篇 |
海洋学 | 41篇 |
天文学 | 92篇 |
综合类 | 6篇 |
自然地理 | 33篇 |
出版年
2023年 | 1篇 |
2022年 | 10篇 |
2021年 | 13篇 |
2020年 | 25篇 |
2019年 | 19篇 |
2018年 | 33篇 |
2017年 | 27篇 |
2016年 | 40篇 |
2015年 | 28篇 |
2014年 | 30篇 |
2013年 | 30篇 |
2012年 | 40篇 |
2011年 | 53篇 |
2010年 | 31篇 |
2009年 | 35篇 |
2008年 | 34篇 |
2007年 | 24篇 |
2006年 | 39篇 |
2005年 | 23篇 |
2004年 | 27篇 |
2003年 | 16篇 |
2002年 | 16篇 |
2001年 | 9篇 |
2000年 | 7篇 |
1999年 | 7篇 |
1998年 | 5篇 |
1997年 | 3篇 |
1996年 | 5篇 |
1995年 | 8篇 |
1994年 | 3篇 |
1993年 | 6篇 |
1992年 | 1篇 |
1991年 | 2篇 |
1990年 | 3篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1987年 | 2篇 |
1985年 | 3篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1973年 | 1篇 |
1970年 | 1篇 |
排序方式: 共有664条查询结果,搜索用时 828 毫秒
301.
302.
303.
Stefano Mottola William D. Sears Anders Erikson Alan W. Harris Jim W. Young Gerhard Hahn Mats Dahlgren Beatrice E. A. Mueller Bill Owen Ricardo Gil-Hutton Javier Licandro M. Antonietta Barucci Claudia Angeli Gerhard Neukum Claes-Ingvar Lagerkvist J. Felix Lahulla 《Planetary and Space Science》1995,43(12)
CCD photometry of the NEAR mission fly-by target 253 Mathilde is presented. Measurements taken during 52 nights of observations, from February to June 1995, allow a rotation period of 17.406±0.010 days and a lightcurve amplitude of 0.45±0.02 mag to be determined. A B-V color index of 0.67±0.02 and a V-R of 0.35±0.02 are measured, which are compatible with C-type membership. The determination of the phase relation results in H = 10.28±0.03 and G = 0.12±0.06. Indications that the lightcurve is not strictly singly-periodic are found. A power-spectrum analysis detects a secondary frequency f2 = 0.0322±0.0010 d−1, which is interpreted as evidence for a complex rotation state. 相似文献
304.
Cesare Barbieri Carlo Blanco Beatrice Bucciarelli Regina Coluzzi Andrea Di Paola Luciano Lanteri Gian Luca Li Causi Ettore Marilli Piero Massimino Vincenzo Mezzalira Stefano Mottola Roberto Nesci Alessandro Omizzolo Fernando Pedichini Francesca Rampazzi Corinne Rossi Ruggero Stagni Milcho Tsvetkov Roberto Viotti 《Experimental Astronomy》2003,15(1):29-43
There is a widespread interest to digitize the precious information contained in the astronomical plate archives, both for
the preservation of their content and for its fast distribution to all interested researchers in order to achieve their better
scientific exploitation. This paper presents the first results of our large-scale project to digitize the archive of plates
of the Italian Astronomical Observatories and of the Specola Vaticana. Similar systems, composed by commercial flat-bed retro-illuminated
scanners plus dedicated personal computers and acquisition and analysis software, have been installed in all participating
Institutes. Ad-hoc codes have been developed to acquire the data, to test the suitability of the machines to our scientific needs, and to reduce
the digital data in order to extract the astrometric, photometric and spectroscopic content. Two more elements complete the
overall project: the provision of high quality BVRI CCD sequences in selected fields with the Campo Imperatore telescopes,
and the distribution of the digitized information to all interested researchers via the Web. The methods we have derived in
the course of this project have been already applied successfully to plates taken by other Observatories, for instance at
Byurakan and at Hamburg. 相似文献
305.
The eastern flank of Mt. Etna volcano rests on Pleistocene marine sediments, which unconformably cover the Apenninic–Maghrebian Chain units. A quantitative biostratigraphic analysis was carried out based on the calcareous nannofossil content of the Pleistocene deposits outcropping along the S and NE periphery of the volcano. Sediments were constrained to the MNN19e and MNN19f biozones, deposited from 1.2 to 0.589 Ma. According to the depth of deposition and the present altitude of the Pleistocene succession, uplift rates are estimated between 1.1 and 1.7 mm yr−1 for the northeastern sector of the Etna edifice, and between 0.36 and 0.61 mm yr−1 for the southern one. This inhomogeneous long-term uplift rate affecting the Etna region, probably results from a buried thrust below the northern flank of Etna, which is related to the post-Tortonian geodynamic evolution of NE Sicily. 相似文献
306.
Kenji Satake Alexander Rabinovich Utku Kano?lu Stefano Tinti 《Pure and Applied Geophysics》2011,168(6-7):963-968
Eighteen papers are included in Volume 1 of a PAGEOPH topical issue Tsunamis in the World Ocean: Past, Present, and Future. These papers are briefly introduced. They are grouped into three categories: case studies of earthquake-generated tsunamis; tsunami forecast and hazard assessments; and theoretical and computational modeling of tsunami generation, propagation, and coastal behavior. Most of the papers were presented at the 24th International Tsunami Symposium held 14?C16 July 2009 in Novosibirsk, Russia, and reflect the current state of tsunami science. 相似文献
307.
Kenji?SatakeEmail author Alexander?Rabinovich Utku?Kano?lu Stefano?Tinti 《Pure and Applied Geophysics》2011,168(11):1913-1917
Fifteen papers are included in Volume 2 of a PAGEOPH topical issue Tsunamis in the World Ocean: Past, Present, and Future. These papers are briefly introduced. They are grouped into three categories: reports and studies of recent tsunamis, studies
on tsunami statistics and application to tsunami warning, and modeling studies of tsunami runup and inundation. Most of the
papers were presented at the 24th International Tsunami Symposium held 14–16 July 2009 in Novosibirsk, Russia, and reflect
the current state of tsunami science. 相似文献
308.
Sebastiano Foti Stefano Parolai Dario Albarello Matteo Picozzi 《Surveys in Geophysics》2011,32(6):777-825
Surface-wave dispersion analysis is widely used in geophysics to infer a shear wave velocity model of the subsoil for a wide
variety of applications. A shear-wave velocity model is obtained from the solution of an inverse problem based on the surface
wave dispersive propagation in vertically heterogeneous media. The analysis can be based either on active source measurements
or on seismic noise recordings. This paper discusses the most typical choices for collection and interpretation of experimental
data, providing a state of the art on the different steps involved in surface wave surveys. In particular, the different strategies
for processing experimental data and to solve the inverse problem are presented, along with their advantages and disadvantages.
Also, some issues related to the characteristics of passive surface wave data and their use in H/V spectral ratio technique
are discussed as additional information to be used independently or in conjunction with dispersion analysis. Finally, some
recommendations for the use of surface wave methods are presented, while also outlining future trends in the research of this
topic. 相似文献
309.
Stefano Covelli Andrea EmiliAlessandro Acquavita Ne?a Koron Jadran Faganeli 《Continental Shelf Research》2011,31(16):1777-1789
Previous research recognized most of the Northern Adriatic coastal lagoon environments as contaminated by mercury (Hg) from multiple anthropogenic sources. Among them, the Pialassa Baiona (P.B.) Lagoon, located near the city of Ravenna (Italy), received between 100 and 200 tons of Hg, generated by an acetaldehyde factory in the period 1957-1977. Further east, the Grado Lagoon has been mainly affected by a long-term Hg input from the Idrija mine (western Slovenia) through the Isonzo River since the 16th century. Hg cycling at the sediment-water interface (SWI) of the two lagoons was investigated and compared by means of an in situ benthic chamber, estimating diffusive Hg and Methyl-Hg fluxes in the summer season. Major chemical features in porewaters (Fe, Mn, H2S, dissolved inorganic (DIC) and organic carbon (DOC), nutrients) and in the solid phase (Corg, N and S) were also explored to understand the general biogeochemical conditions of the system in response to benthic respiration. The daily integrated flux for the methylated Hg form was extremely low in P.B. Lagoon, accounting for only 7% of the corresponding flux calculated for the Grado Lagoon. Despite a higher sedimentary Hg content in the P.B. Lagoon (14.4-79.0 μg g−1) compared to the Grado Lagoon (10.7-12.5 μg g−1), the in situ fluxes of Hg in the two experimental sites appeared similar. A selective sequential extraction procedure was applied to the solid phase, showing that the stable crystalline mineral phase cinnabar (HgS) is the predominant Hg fraction (about 50%) in the Grado Lagoon surface sediments. Conversely, Hg mobilization and sequestration in the P.B. Lagoon is related to the extremely anoxic redox conditions of the system where the intense sulfate reduction, by the release of sulfur and the formation of sulfides, limits the metal recycling at the SWI and its availability for methylation processes. Thus, the environmental conditions at the SWI in the P.B. Lagoon seem to represent a natural “barrier” for the potential risk of Hg transfer to the aquatic trophic chain. 相似文献
310.
Sediment load plays a fundamental role in natural river morphology evolution. Therefore, the correct assessment of the role
of the sediment load on natural or anthropic pools morphology downstream of river grade control structures, such as rock chute
or block ramps, is of fundamental interest for preserving the fish habitat and the river morphology. This work presents an
experimental study on the sediment load influence on rectangular expanding pools downstream of block ramps in live-bed conditions.
Several longitudinal and transversal expanding ratios have been tested. Ramp slopes were varied between 0.083 and 0.25. The
effect of the pool geometry and the sediment load on hydraulic jump downstream of block ramp as well as scour morphologies
and flow patterns have been analyzed. Equations were derived to evaluate the maximum scour hole depth, the longitudinal distance
of the section in which it occurs, and the maximum water elevations both in the pool and in the downstream contraction. 相似文献