全文获取类型
收费全文 | 623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 | 235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 | 2篇 |
1970年 | 1篇 |
排序方式: 共有665条查询结果,搜索用时 31 毫秒
241.
Anna Milillo Valeria Mangano Alessandro Mura Stefano Orsini Elisabetta De Angelis Andrea M. Di Lellis Stefano Massetti Christina Plainaki Rosanna Rispoli Stefano Selci Nello Vertolli 《Experimental Astronomy》2011,32(1):37-49
Observation of the lunar exosphere is a tool for remote sensing of the surface properties. The sources of this exosphere are related to the interactions of the lunar surface with the solar radiation, with the solar wind or Earth??s magnetospheric plasma, and with the interplanetary dust and meteorites. In fact, the exospheric particles are continuously created and subsequently lost in the interplanetary space, photo-ionized or re-adsorbed by the surface. Eventually, the estimation of the surface composition is not possible without the knowledge of the active release mechanisms. The relative weight of the different release processes of the various atoms, ions and molecules from the surface is still an open debate. Investigation of the Moon??s release processes and interaction with the near-Earth environment is of crucial importance for both determining the relative process release contribution and understanding the surface evolution of other airless bodies, like Mercury and the giant planets?? moons. In this work, an attempt to analyze the processes that take place on the surface of these small airless bodies, as a result of their exposure to the space environment, has been realized by means of the MonteCarlo Environment Simulation Tool (EST), applied to the Moon. The model results show that the different release processes can be identified by analysing the exospheric energy distribution. Finally, the instrument concept of the ??Analizzatore Lunare di ENA?? (ALENA), part of the MAGIA payload and specifically designed for detecting the high-energy particles released from the lunar surface is presented. 相似文献
242.
In the standard afterglow model, the swept electrons have a single power-law energy distribution dn/dγe ∝ γ−p e (p ∼ 2.3), owing to the first order Fermi acceleration process. However, in some events people find a lot of evidence for a flat electron spectrum (i.e., p < 2). In this work, the analytical afterglow light curves in the case of a flat electron energy distribution are presented respectively for a single power-law spectrum and a broken power-law spectrum, then the results are applied to the specific burst GRB 060908. Besides, we have also speculated a possible solution of the so-called low energy spectrum crisis of Gamma-ray Bursts 相似文献
243.
Timothy D. Jones Ian T. Lawson Jane M. Reed Graham P. Wilson Melanie J. Leng Merle Gierga Stefano M. Bernasconi Rienk H. Smittenberg Irka Hajdas Charlotte L. Bryant P. C. Tzedakis 《Journal of Paleolimnology》2013,49(2):185-204
The character and impact of climate change since the last glacial maximum (LGM) in the eastern Mediterranean region remain poorly understood. Here, two new diatom records from the Ioannina basin in northwest Greece are presented alongside a pre-existing record and used to infer past changes in lake level, a proxy for the balance between precipitation and evaporation. Comparison of the three records indicates that lake-level fluctuations were the dominant driver of diatom assemblage composition change, whereas productivity variations had a secondary role. The reconstruction indicates low lake levels during the LGM. Late glacial lake deepening was underway by 15.0 cal kyr BP, implying that the climate was becoming wetter. During the Younger Dryas stadial, a lake-level decline is recorded, indicating arid climatic conditions. Lake Ioannina deepened rapidly in the early Holocene, but long-term lake-level decline commenced around 7.0 cal kyr BP. The pattern of lake-level change is broadly consistent with an existing lake-level reconstruction at Lake Xinias, central Greece. The timing of the apparent change, however, is different, with delayed early Holocene deepening at Xinias. This offset is attributed to uncertainties in the age models, and the position of Xinias in the rain shadow of the Pindus Mountains. 相似文献
244.
ROckfall risk MAnagement assessment: the RO.MA. approach 总被引:1,自引:1,他引:0
The analysis of risk for vehicles and drivers as a result of rockfall on a road is relevant to design management in geotechnical engineering. This process is very complex due to the large number of parameters involved. In this paper, we discuss risk analysis and management procedures for roads subject to rockfall phenomena. To this aims, we are proposing a quantitative method (the RO.MA. approach). We developed an abacus to define the threshold values of acceptable rockfall risk for a given road. Rockfall risk is calculated using an Event Tree approach and compared with the abacus thresholds to evaluate road safety and the need for additional protective measures to reduce the risk to an acceptable level. The approach was successfully applied at a test site located in Bard, Aosta Valley, north-western Italy. 相似文献
245.
Sediment load plays a major role in the morphological evolution of rivers.Therefore,the analysis of the sediment load interaction with hydraulic structures is of main importance in order to enhance the preservation of fish habitats and river morphological characteristics.The present study analyzes the scour mechanisms downstream of a block ramp in live bed conditions,when the sediment supplied by the approaching flow is balanced by the sediment transported out of the scour hole.Experiments were performed in a model flume and the effect of the approaching sediment concentration on the scour geometry was analyzed.It was observed that the scour features depend deeply on the approaching sediment concentration and four main profile configurations were distinguished.The experimental data were analyzed and empirical relationships were developed in order to evaluate the depth and length of a scour hole,the dune height and the distance of the transversal section of maximum dune height from the ramp toe for different hydraulic and geometric conditions.It was also proved that the dynamic equilibrium shape of a scour hole does not depend on the sediment load time history. 相似文献
246.
247.
The authors thank the discusser for his interest and careful review of the paper and his valuable comments.They also welcome this discussion,because it gives the authors the opportunity to clarify several points which were not explained in sufficient detail in the paper,due to space limitations.
The paper does not provide any personal or professional criticism of the discusser or his work and if any statement may have raised an ambiguous interpretation,this should be clarified and dismissed.Any inaccuracy in the reference's citation was not intentional.Some of the authors do not speak Italian;therefore they could not read directly and understand the paper cited by the discusser,which is in Italian. 相似文献
248.
249.
Michael Rowan-Robinson Tom Babbedge Seb Oliver Markos Trichas Stefano Berta Carol Lonsdale Gene Smith David Shupe Jason Surace Stephane Arnouts Olivier Ilbert Olivier Le Févre Alejandro Afonso-Luis Ismael Perez-Fournon Evanthia Hatziminaoglou Mari Polletta Duncan Farrah Mattia Vaccari 《Monthly notices of the Royal Astronomical Society》2008,386(2):697-714
250.
Stefano Tinti 《Marine Geodesy》2013,36(3-4):243-254
Abstract In the Mediterranean Sea, tsunamigenic sources may be found in several areas in the belt running from Gibraltar up to the Black Sea, but they are concentrated mainly around Italy and Greece. Most of the sources are located close to the coasts and excite tsunamis reaching the coasts soon after the generation time. Tsunami research and tsunami mitigation programs are only in a very initial stage in the Mediterranean area. The present activities are focused chiefly to tsunami potential evaluation and on tsunami propagation modeling. The establishment of efficient observational networks, centers for data management and services, and systems for issuing tsunami warnings are some of the most urgent needs. In this context, the envisaged contribution of marine geodesy is twofold. First, monitoring of submarine active faults and submarine volcanic areas by means of systems capable of detecting seafloor deformation may contribute in identifying periods in which the probability of tsunami generation increases beyond a threshold value, especially in those tsunamigenic zones where geodetic observations on land are insufficient (for example, eastern Sicily in Italy and the Hellenic Arc in southern Greece). Second, since most of the active sources are close to the coastline, computations of tsunami propagation and run‐up may be significantly enhanced by a better knowledge of the bathymetry of the seabelt facing the coasts. 相似文献