全文获取类型
收费全文 | 560篇 |
免费 | 21篇 |
国内免费 | 19篇 |
专业分类
测绘学 | 5篇 |
大气科学 | 36篇 |
地球物理 | 120篇 |
地质学 | 201篇 |
海洋学 | 45篇 |
天文学 | 144篇 |
综合类 | 18篇 |
自然地理 | 31篇 |
出版年
2024年 | 1篇 |
2023年 | 5篇 |
2022年 | 4篇 |
2021年 | 17篇 |
2020年 | 5篇 |
2019年 | 15篇 |
2018年 | 27篇 |
2017年 | 28篇 |
2016年 | 31篇 |
2015年 | 30篇 |
2014年 | 29篇 |
2013年 | 30篇 |
2012年 | 17篇 |
2011年 | 36篇 |
2010年 | 35篇 |
2009年 | 34篇 |
2008年 | 39篇 |
2007年 | 40篇 |
2006年 | 24篇 |
2005年 | 17篇 |
2004年 | 19篇 |
2003年 | 19篇 |
2002年 | 14篇 |
2001年 | 17篇 |
2000年 | 12篇 |
1999年 | 6篇 |
1998年 | 13篇 |
1997年 | 1篇 |
1996年 | 2篇 |
1995年 | 5篇 |
1994年 | 4篇 |
1993年 | 5篇 |
1992年 | 2篇 |
1991年 | 1篇 |
1990年 | 2篇 |
1989年 | 3篇 |
1981年 | 2篇 |
1972年 | 1篇 |
1965年 | 1篇 |
1964年 | 1篇 |
1963年 | 1篇 |
1962年 | 2篇 |
1961年 | 1篇 |
1960年 | 2篇 |
排序方式: 共有600条查询结果,搜索用时 15 毫秒
591.
Resting Stages of Crustaceans in the Crimean Hypersaline Lakes(Ukraine) and Their Ecological Role 总被引:1,自引:0,他引:1
正1 Introduction A presence of resting stages in various aquatic organisms is a long-known phenomenon as a mechanism of species adaptation to exist in unstable aquatic habitats,surviving adverse conditions in the"sleeping"state(Radzikowski,2013).Bank of resting stages of planktonic organisms is an important component of the plankton community,without which we cannot understand community dynamics(Brendonck and De Meester,2003). 相似文献
592.
Asbestos and other fibrous minerals contained in the serpentinites of the Gimigliano-Mount Reventino Unit (Calabria,S-Italy) 总被引:1,自引:1,他引:0
Andrea Bloise Teresa Critelli Manuela Catalano Carmine Apollaro Domenico Miriello Alessandro Croce Eugenio Barrese Francesca Liberi Eugenio Piluso Caterina Rinaudo Elena Belluso 《Environmental Earth Sciences》2014,71(8):3773-3786
Serpentinites are metamorphic rocks with good technological properties and valuable ornamental characteristics, which have been exploited since ancient times. Actually, their use is limited and monitored in several countries worldwide because they can contain fibrous asbestos minerals that may be carcinogenic. Furthermore, certain types of fibrous minerals can be confused with asbestos, and must therefore be carefully investigated. We have investigated the possible presence of the asbestos and non-asbestos fibrous phases contained in serpentinitic rocks in a meta-ophiolitic sequence from the Gimigliano-Mount Reventino Unit (Southern Italy), which had not been previously assessed. The detection and quantification of asbestos and the correct distinction of the fibrous non-asbestos minerals are very important not only from a scientific point of view, but also from a legislative one. This is especially the case for the administrative agencies that have to take decisions with regards to the implementation of public and occupational health protection measures (e.g., in road yards and quarry excavations). As a consequence of this, serpentinitic rock samples have been characterized in detail through X-ray powder diffraction, scanning and transmission electron microscopy combined with energy-dispersive spectrometry, analytical electron microscopy (SEM–EDS and TEM–AEM), differential scanning calorimetry, thermogravimetry and micro-Raman spectroscopy. Two kinds of asbestos and four kinds of non-asbestos fibrous silicates have been detected in the examined samples. In order of decreasing abundance these are polygonal serpentine, chrysotile, fibrous antigorite, tremolite, gedrite and magnesiohornblende. The size, morphology, crystallinity and chemical composition of the fibres were also discussed, in the light of the possible role these properties could play in the carcinogenic effect on human health. 相似文献
593.
Van Lichtervelde Marieke Grand’Homme Alexis de Saint-Blanquat Michel Olivier Philippe Gerdes Axel Paquette Jean-Louis Melgarejo Joan Carles Druguet Elena Alfonso Pura 《Mineralogy and Petrology》2017,111(1):1-21
Mineralogy and Petrology - The Cap de Creus granitic pegmatites in the eastern Catalan Pyrenees were dated using in situ U-Pb geochronology by laser ablation ICP-MS on zircon and columbite-group... 相似文献
594.
Elena Costa Frola Andrea Mazzino Federico Cassola Luca Mortarini Enrico Ferrero 《Boundary-Layer Meteorology》2014,150(1):91-106
A statistical characterization for two-point temperature fluctuations in the planetary boundary layer (PBL) is analyzed and its implications on the long-standing closure problem discussed. Despite the non-triviality of the dynamics of temperature fluctuations, our analysis supports the idea that the most relevant statistical properties can be captured solely in terms of two scaling exponents. They turned out to be weakly dependent on the stability properties of the PBL. Its statistics have been investigated by collecting data from a field experiment carried out in the urban area of Turin (Italy) from January 2007 to March 2008. Our results confirm those from a large-eddy simulation (LES) analysis carried out for the convective PBL with different level of convection. We extend the scenario to the stable PBL, a regime much more difficult to simulate when exploiting LES. 相似文献
595.
Elena Gottardini Fabiana Cristofolini Elena Paoletti Paolo Lazzeri Giancarlo Pepponi 《Journal of Atmospheric Chemistry》2004,49(1-3):149-159
Biological characterization of Corylus avellana L. and Pinus nigra L. pollen samples was carried out to determine the actual value of pollen as a bio-indicator of the effects of atmospheric pollution, using samples from plants naturally developed in sites controlled for air pollution. In Trentino (North Italy), we selected six stations at three different levels of air pollution, which are constantly monitored with automatic gauges by the Environmental Protection Agency of Trento.First results showed that pollen viability of both species, germinability and pollen tube length of P. nigra, were higher in areas with no road traffic compared to heavy traffic ones. Pollen viability of P. nigra was positively correlated to ozone (O3) concentrations and altitude but negatively to sulphur dioxide (SO2), particulate matter with a diameter less than 10 m (PM10), nitrogen oxides (NOx) and nitrogen dioxide (NO2) concentrations. 相似文献
596.
This study analyses the perceptions of Zoque indigenous men and women of changes in climate variability, indicated by rainfall and temperature records from the region. Peasant farmers perceive decreases in rainfall and increases in temperature as these factors are related to modifications in the corn planting season and the introduction of crops which were usually only found in hot regions. The climate changes in the zone are attributed to vegetation loss and the eruption of the Chichón volcano in 1982. The Zoque perception is structured according to cultural and individual experience, tied to agriculture and the annual weather calendar. The volcanic eruption offers a significant chronological reference point in order to explain different environmental transformations, such as climate, within Zoque territory. Perception is the mental picture of local climate variability changes and the responses in seasonal agriculture modifications, utilizing individual and cultural experiences which are vulnerable to economic and environmental change. 相似文献
597.
正Artemia cysts are an extremely important component of aquaculture diets.It is well established that the cultivation of fish and shellfish derive substantial health and growth advantages when Artemia are included in the diets of the 相似文献
598.
599.
华北陆块是中国最大、最古老的克拉通(图la),像世界上其他古老克拉通一样,由上部古老地壳和下部厚的、冷的、耐熔的古老岩石圈地幔组成,自古元古代末东、西部陆块碰撞、拼合、克拉通化后直到奥陶纪,一直保持着相对稳定,缺乏强烈的岩浆、构造活动和显著的大陆地壳生长[1].然而,自古生代以来,随着岩石圈强烈减薄作用,在华北克拉通东部广泛发育强烈的构造、岩浆、成矿作用,形成大面积花岗岩(图1b)和火山岩[2]. 相似文献
600.
This paper presents a morphological and hydrogeological reconstruction of the Murcia Valley at the location of the great Roman stadium Circus Maximus in Rome. We reconstruct a valley segment using ERT (electrical resistivity tomography) and geoarchaeological drilling data that identified three main layers. The basal layer, with high resistivity values and convex shapes, is correlated to alluvial gravel and lithified silt‐clay sediments. The middle layer shows low‐to‐medium resistivity values extending to concavities between the basal convex shapes. The very low resistivity values of this middle layer characterize elliptical to circular morphologies and have been ascribed to the presence of water‐saturated clay‐silt and peaty sediments. The surface layer is characterized by widespread lateral inhomogeneity interpreted as anthropogenic fill. The data indicate a pre‐Roman anastomosed alluvial plain subsequently modified by human intervention. In an effort to reclaim the valley for construction of the Circus, the Romans utilized the natural topography and created a central embankment, later becoming the Spina, by filling depressions with sand taken from adjacent bars. Our study contributes to (1) knowledge of the pre‐Roman landscape, (2) understanding anthropogenic modification of the Murcia Valley flood plain, and (3) archaeological interpretation of the monument. 相似文献