全文获取类型
收费全文 | 323篇 |
免费 | 19篇 |
国内免费 | 4篇 |
专业分类
测绘学 | 16篇 |
大气科学 | 15篇 |
地球物理 | 113篇 |
地质学 | 91篇 |
海洋学 | 34篇 |
天文学 | 54篇 |
综合类 | 2篇 |
自然地理 | 21篇 |
出版年
2024年 | 1篇 |
2021年 | 11篇 |
2020年 | 9篇 |
2019年 | 7篇 |
2018年 | 11篇 |
2017年 | 15篇 |
2016年 | 26篇 |
2015年 | 14篇 |
2014年 | 17篇 |
2013年 | 21篇 |
2012年 | 24篇 |
2011年 | 23篇 |
2010年 | 22篇 |
2009年 | 27篇 |
2008年 | 17篇 |
2007年 | 15篇 |
2006年 | 11篇 |
2005年 | 18篇 |
2004年 | 11篇 |
2003年 | 11篇 |
2002年 | 7篇 |
2001年 | 5篇 |
2000年 | 7篇 |
1999年 | 3篇 |
1998年 | 2篇 |
1997年 | 3篇 |
1996年 | 2篇 |
1995年 | 1篇 |
1994年 | 2篇 |
1988年 | 2篇 |
1983年 | 1篇 |
排序方式: 共有346条查询结果,搜索用时 17 毫秒
341.
342.
Simona Ghizzardi Martino Marelli David Salvetti Fabio Gastaldello Silvano Molendi Andrea De Luca Alberto Moretti Mariachiara Rossetti Andrea Tiengo 《Experimental Astronomy》2017,44(3):273-285
A detailed characterization of the particle induced background is fundamental for many of the scientific objectives of the Athena X-ray telescope, thus an adequate knowledge of the background that will be encountered by Athena is desirable. Current X-ray telescopes have shown that the intensity of the particle induced background can be highly variable. Different regions of the magnetosphere can have very different environmental conditions, which can, in principle, differently affect the particle induced background detected by the instruments. We present results concerning the influence of the magnetospheric environment on the background detected by EPIC instrument onboard XMM-Newton through the estimate of the variation of the in-Field-of-View background excess along the XMM-Newton orbit. An important contribution to the XMM background, which may affect the Athena background as well, comes from soft proton flares. Along with the flaring component a low-intensity component is also present. We find that both show modest variations in the different magnetozones and that the soft proton component shows a strong trend with the distance from Earth. 相似文献
343.
Scribano Vittorio Carbone Serafina Manuella Fabio C. Hovland Martin Rueslåtten Håkon Johnsen Hans-K. 《International Journal of Earth Sciences》2017,106(7):2595-2608
International Journal of Earth Sciences - Worldwide marine salt deposits ranging over the entire geological record are generally considered climate-related evaporites, derived from the... 相似文献
344.
The medium-sized cities of Brazil are those with populations of between 100,000 and 500,000 inhabitants. These cities are growing rapidly, and are characterized by poor urban planning, a loss of biodiversity and decreasing health prospects for residents. Historically, urbanization in Brazil has been associated with incentives to increase the use of private vehicles for local transport. The air pollution resulting from this “car dependency” has been quantified in some major cities in Brazil, such as the megacity of São Paulo. In this paper, we demonstrate through a bioindication study carried out in the Brazilian city of Rondonópolis, that atmospheric pollution resulting from vehicular emissions is also a measurable reality for medium-sized cities. Most Brazilian cities lack air quality measurement equipment, and we used an inexpensive and easy to apply bioindication assay to measure air pollution, and this approach could be easily implemented in those cities and beyond. 相似文献
345.
Fabio Ciabarri Alfredo Mazzotti Eusebio Stucchi Nicola Bienati 《Geophysical Prospecting》2015,63(2):296-314
Least squares Fourier reconstruction is basically a solution to a discrete linear inverse problem that attempts to recover the Fourier spectrum of the seismic wavefield from irregularly sampled data along the spatial coordinates. The estimated Fourier coefficients are then used to reconstruct the data in a regular grid via a standard inverse Fourier transform (inverse discrete Fourier transform or inverse fast Fourier transform). Unfortunately, this kind of inverse problem is usually under‐determined and ill‐conditioned. For this reason, the least squares Fourier reconstruction with minimum norm adopts a damped least squares inversion to retrieve a unique and stable solution. In this work, we show how the damping can introduce artefacts on the reconstructed 3D data. To quantitatively describe this issue, we introduce the concept of “extended” model resolution matrix, and we formulate the reconstruction problem as an appraisal problem. Through the simultaneous analysis of the extended model resolution matrix and of the noise term, we discuss the limits of the Fourier reconstruction with minimum norm reconstruction and assess the validity of the reconstructed data and the possible bias introduced by the inversion process. Also, we can guide the parameterization of the forward problem to minimize the occurrence of unwanted artefacts. A simple synthetic example and real data from a 3D marine common shot gather are used to discuss our approach and to show the results of Fourier reconstruction with minimum norm reconstruction. 相似文献
346.
This work focuses on developing multidisciplinary research on weathering profiles of granitoid rocks related to the tectonic and landscape evolution of the Capo Vaticano area, Calabria, southern Italy. During the Pleistocene, the Mediterranean climate plays, on the already decomposed plutonic rocks, important processes of alteration, on both the highest and inland areas and the coastal areas of the Calabrian region, such as the studied area. Field observations coupled to chemical, minero‐petrographical features and geochemical modelling are used to characterize the weathering processes affecting the granitoid complex. The granitoid cut slopes show a generally simple weathering profile characterized by a progressive increase in weathering towards the top of the slopes. The completely weathered rocks (class V) and residual soil (class VI) contain a high percentage of altered minerals, microfractures, and voids. The main mineralogical changes are the partial transformation of biotite and the partial destruction of feldspars (mainly plagioclase) that are associated with the neoformation of secondary clay minerals and ferruginous products during the most advanced stage of weathering. These transformations produce a substitution of the original rock fabric. Geochemical modelling showing the precipitation of kaolinite, illite, vermiculite, ferrihydrite and calcite. These secondary solid phases are similar to those found in this natural system. Thus, the final results of the weathering process is a soil‐like material mainly characterized by mostly a sand to gravel grain‐size fractions related to microfabric changes and mineralogical and chemical variations. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献