全文获取类型
收费全文 | 625篇 |
免费 | 12篇 |
国内免费 | 2篇 |
专业分类
测绘学 | 17篇 |
大气科学 | 51篇 |
地球物理 | 284篇 |
地质学 | 113篇 |
海洋学 | 2篇 |
天文学 | 151篇 |
综合类 | 1篇 |
自然地理 | 20篇 |
出版年
2018年 | 11篇 |
2017年 | 13篇 |
2016年 | 17篇 |
2015年 | 12篇 |
2014年 | 21篇 |
2013年 | 23篇 |
2012年 | 17篇 |
2011年 | 29篇 |
2010年 | 22篇 |
2009年 | 15篇 |
2008年 | 12篇 |
2007年 | 16篇 |
2006年 | 17篇 |
2005年 | 16篇 |
2004年 | 8篇 |
2003年 | 8篇 |
2002年 | 9篇 |
2001年 | 7篇 |
2000年 | 7篇 |
1999年 | 16篇 |
1998年 | 6篇 |
1997年 | 6篇 |
1996年 | 16篇 |
1995年 | 16篇 |
1994年 | 15篇 |
1993年 | 7篇 |
1992年 | 12篇 |
1991年 | 10篇 |
1990年 | 16篇 |
1989年 | 22篇 |
1988年 | 11篇 |
1987年 | 9篇 |
1986年 | 9篇 |
1985年 | 11篇 |
1984年 | 12篇 |
1983年 | 9篇 |
1982年 | 8篇 |
1981年 | 11篇 |
1980年 | 10篇 |
1978年 | 11篇 |
1976年 | 7篇 |
1975年 | 6篇 |
1974年 | 6篇 |
1973年 | 6篇 |
1971年 | 10篇 |
1970年 | 7篇 |
1969年 | 8篇 |
1963年 | 5篇 |
1960年 | 5篇 |
1957年 | 5篇 |
排序方式: 共有639条查询结果,搜索用时 265 毫秒
101.
Performance of ENSEMBLES regional climate models over Central Europe using various metrics 总被引:1,自引:1,他引:0
Eva Holtanová Ji?í Mik?ovsky Jaroslava Kalvová Petr Pi?oft Martin Motl 《Theoretical and Applied Climatology》2012,108(3-4):463-470
We show the evaluation of ENSEMBLES regional climate models (RCMs) driven by reanalysis ERA40 over a region centered at the Czech Republic. Attention is paid especially to the model ALADIN-CLIMATE/CZ, being used as the basis of the new climate change scenarios simulation for the Czech Republic. The validation criteria used here are based on monthly or seasonal mean air temperature and precipitation. We concentrate not only on spatiotemporal mean values but also on temporal standard deviation, inter-annual variability, the mean annual cycle, and the skill of the models to represent the observed spatial patterns of these quantities. Model ALADIN-CLIMATE/CZ performs quite well in comparison to the other RCMs; we find its performance satisfactory for further use for impact studies. However, it is also shown that the results of evaluation of the RCMs’ skill in simulating observed climate strongly depend on the criteria incorporated for the evaluation. 相似文献
102.
Martin Mozny Mirek Trnka Zdenek Zalud Petr Hlavinka Jiri Nekovar Vera Potop Michal Virag 《Theoretical and Applied Climatology》2012,107(1-2):99-111
Since 2000, the network of stations that make up the Czech Hydrometeorological Institute (CHMI) has measured the soil moisture content at the 0- to 0.9-m layer using sensors placed within the natural soil profile under closely cropped grass cover. Using information from 8?years of continuous observation at seven stations throughout the Czech Republic, we verified the usefulness of the Soil Moisture Index (SMI). The SMI is a potentially useful index for calculating the water deficit in the Czech Republic and Central Europe. During this period, a statistically significant decrease in moisture content was detected, and negative SMI values predominated. There were frequent occurrences of flash drought, defined as a very rapid decline in soil moisture during a 3-week period. The CHMI can use SMI values below ?3 in the Integrated Warning Service System. The routine calculation of SMI values can alert agricultural producers to the development of flash drought conditions and provide them with information regarding the effectiveness of recent rainfall events. An increase in soil moisture, in contrast, could serve as a warning sign for hydrology because it creates the preconditions for flooding. The complex study of soil humidity regimes is becoming more significant in connection with current global climatic change warnings in hydrological cycles. 相似文献
103.
European floods during the winter 1783/1784: scenarios of an extreme event during the ‘Little Ice Age’ 总被引:1,自引:0,他引:1
Rudolf Brázdil Gaston R. Demarée Mathias Deutsch Emmanuel Garnier Andrea Kiss Jürg Luterbacher Neil Macdonald Christian Rohr Petr Dobrovolný Petr Kolář Kateřina Chromá 《Theoretical and Applied Climatology》2010,100(1-2):163-189
The Lakagígar eruption in Iceland during 1783 was followed by the severe winter of 1783/1784, which was characterised by low temperatures, frozen soils, ice-bound watercourses and high rates of snow accumulation across much of Europe. Sudden warming coupled with rainfall led to rapid snowmelt, resulting in a series of flooding phases across much of Europe. The first phase of flooding occurred in late December 1783–early January 1784 in England, France, the Low Countries and historical Hungary. The second phase at the turn of February–March 1784 was of greater extent, generated by the melting of an unusually large accumulation of snow and river ice, affecting catchments across France and Central Europe (where it is still considered as one of the most disastrous known floods), throughout the Danube catchment and in southeast Central Europe. The third and final phase of flooding occurred mainly in historical Hungary during late March and early April 1784. The different impacts and consequences of the above floods on both local and regional scales were reflected in the economic and societal responses, material damage and human losses. The winter of 1783/1784 can be considered as typical, if severe, for the Little Ice Age period across much of Europe. 相似文献
104.
The paper presents a new method of the estimation of spatial variations of the magnetic field and superthermal electron distribution
in solar cm-radio burst sources. The method is based on minimization of the difference between the theoretical and observed
radio fluxes and on the analysis of several burst spectra recorded in different moments of time. Several solar cm-radio bursts
are analyzed by this method. It is found that the measure of the spatial variations of the superthermal electron distribution
in the radio source is always larger than that for the magnetic field. 相似文献
105.
Jiří Žák Scott R. Paterson Vojtěch Janoušek Petr Kabele 《Contributions to Mineralogy and Petrology》2009,158(4):447-470
The Mammoth Peak sheeted intrusive complex formed in the interior of a ~7–10 km deep magma chamber, specifically in the Half
Dome granodiorite of the Tuolumne batholith, central Sierra Nevada, CA (USA). The sheets consist of fractionated melts with
accumulated hornblende, biotite, magnetite, titanite, apatite, and zircon. The accumulation, especially of titanite, had a
profound effect on minor and trace elements (Nb, Ta, Ti, REE, U, Th, P, Zr, Hf, etc.), increasing their contents up to five
to six times. Our thermal–mechanical modeling using the finite element method shows that cooling-generated tensile stresses
resulted in the inward propagation of two perpendicular sets of dilational cracks in the host granodiorite. We interpret the
sheeted complex to have formed by a crack-seal mechanism in a high strength, crystal-rich mush, whereby outward younging pulses
of fractionated magma were injected into these syn-magmatic cracks at the margin of an active magma chamber. Thermal–mechanical
instabilities developed after the assembly of the sheeted complex, which was then overprinted by late ~NW–SE magmatic foliation.
This case example provides a cautionary note regarding the interpretation that sheeted zones in large granitoid plutons imply
a diking mechanism of growth because the sheeted/dike complexes in plutons (1) may display inverse growth directions from
the growth of the overall intrusive sequence; (2) need not record initial chamber construction and instead may reflect late
pulsing of magma within an already constructed magma chamber; (3) have an overprinting magmatic fabric indicating the continued
presence of melt after construction of sheeted complexes and thus a prolonged thermal history as compared to dikes; and (4)
because the scale of the observed sheeted complexes may be small (<1%) in comparison to large homogenous parts of plutons,
in which there is no evidence for sheeting or diking. Thus, where extensive dike complexes in plutons are absent, such as
in much of the Tuolumne batholith, the application of an incremental diking model to explain chamber construction is at best
speculative. 相似文献
106.
We report exceptional fireball activity of the Orionid meteor shower in 2006. During four nights in October 2006 the autonomous
fireball observatories of the Czech part of the European Fireball Network (EN) recorded 48 fireballs belonging to the Orionids.
This is significantly more than the total number of Orionids recorded during about five decades long continuous operation
of the EN. Based on precise multi-station photographic and radiometric data we present accurate atmospheric trajectories,
heliocentric orbits, light curves and basic physical properties of 10 Orionid fireballs with atmospheric trajectories that
were long enough and, with one exception, were observed from at least three stations. Seven were recorded in within a 2-h
interval in the night of 20/21 October. Their basic parameters such as radiant positions and heliocentric orbits are very
similar. This high fireball activity originated from a very compact geocentric radiant defined by α = 95.10° ± 0.10° and
δ = 15.50° ± 0.06°. These fireballs most likely belonged to a distinct filament of larger meteoroids trapped in 1:5 resonance
with Jupiter. From detailed light curves and basic fireball classification we found that these meteoroids appertain to the
weakest component of interplanetary matter. 相似文献
107.
Miroslav Šifta Pavel Chromý 《Norsk geografisk tidsskrift. Norwegian journal of geography》2017,71(2):98-113
The aim in the article is to conceptualize the general foundations of research on the importance of regional symbolism in the process of region and regional identity formation. The article is founded on a critical analysis of works pertaining not only to the field of the new regional geography, but also to the field of regional marketing and/or branding, sociology, and semiology. The authors focus on meanings attributed to symbols and symbolism in literature, and observe which elements are viewed as regional symbols and how these symbols contribute to the process of regional development and institutionalization, especially in the formation of its symbolic shape. They examine the thematic and theoretical grounds, looking at identity, regional identity, and regional institutionalization. Next, regional symbols are defined and classified according to their types and forms, and their importance in the process of regional formation and institutionalization is discussed. The results show that symbols of any type can play an important role in a region’s marketing, and become the key image associated with a region. The authors conclude that regional symbols are a significant feature of the formation of a region and its identity, both outwardly (the external image of a region) and inwardly (concerning the inhabitants’ relationships with their region). 相似文献
108.
Petr Holota 《Studia Geophysica et Geodaetica》1999,43(2):228-228
109.
A set of outcrop samples from the Lokoja and Patti Formations of the southern Bida Basin (Nigeria) was examined for grain size distribution, sedimentary and hydraulic characteristics. Most of the samples are well-sorted with an uniformity coefficient (U) ranging between 1.3 and 6.3. The mean effective grain diameter (d10) is in the order of 0.11 mm, the mean value of d90 was determined as 0.66 mm (both geometric mean) and the median grain size (d50) as 0.23 mm. Based on these values, the sedimentary sequence can be described as ‘fine to medium sized sand’, having minor amounts of either silt, or coarse sand and some gravel. The total porosity of the samples was determined by laboratory methods to be in the range of 9–29%. The hydraulic conductivity (K) was determined according to Hazen.and Beyer, and by Shepherd's formula, the last resulting in a geometric mean of 3.3 m d−1 or 3.3 darcy. The results are used to estimate local groundwater potential. The entire pore space (potential groundwater reservoir) for the area under study is estimated to be in the order of 290–430 km3. Because of higher hydraulic conductivities, it is recommended that the Lokoja Formation is concentrated on as a target for groundwater exploration. 相似文献
110.
Luděk Sýkora 《GeoJournal》1999,49(1):79-89
The article overviews the most important changes in the internal urban structure of Prague since 1989. Post-communist urban
development has been influenced by government-directed reforms of political and economic system, internationalisation and
globalisation, public policies favouring unregulated market development, economic restructuring in terms of deindustrialisation
and growth of producer services, and increasing social differentiation. The three most transparent processes of urban change
in Prague have been (1) commercialisation of the historical core; (2) revitalisation of some inner city neighbourhoods; and
(3) residential and commercial suburbanisation in the outer city.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献