全文获取类型
收费全文 | 6952篇 |
免费 | 396篇 |
国内免费 | 39篇 |
专业分类
测绘学 | 186篇 |
大气科学 | 738篇 |
地球物理 | 1820篇 |
地质学 | 2724篇 |
海洋学 | 406篇 |
天文学 | 1147篇 |
综合类 | 35篇 |
自然地理 | 331篇 |
出版年
2023年 | 34篇 |
2022年 | 47篇 |
2021年 | 133篇 |
2020年 | 146篇 |
2019年 | 118篇 |
2018年 | 316篇 |
2017年 | 326篇 |
2016年 | 437篇 |
2015年 | 310篇 |
2014年 | 373篇 |
2013年 | 543篇 |
2012年 | 421篇 |
2011年 | 398篇 |
2010年 | 373篇 |
2009年 | 395篇 |
2008年 | 265篇 |
2007年 | 227篇 |
2006年 | 217篇 |
2005年 | 168篇 |
2004年 | 175篇 |
2003年 | 138篇 |
2002年 | 135篇 |
2001年 | 114篇 |
2000年 | 94篇 |
1999年 | 82篇 |
1998年 | 88篇 |
1997年 | 103篇 |
1996年 | 60篇 |
1995年 | 78篇 |
1994年 | 71篇 |
1993年 | 52篇 |
1992年 | 38篇 |
1991年 | 39篇 |
1990年 | 65篇 |
1989年 | 32篇 |
1988年 | 31篇 |
1987年 | 51篇 |
1986年 | 33篇 |
1985年 | 44篇 |
1984年 | 50篇 |
1983年 | 44篇 |
1982年 | 42篇 |
1981年 | 50篇 |
1980年 | 25篇 |
1979年 | 27篇 |
1978年 | 30篇 |
1977年 | 29篇 |
1975年 | 29篇 |
1974年 | 23篇 |
1973年 | 29篇 |
排序方式: 共有7387条查询结果,搜索用时 656 毫秒
881.
Francis Joseph Turk Byung-Ju Sohn Hyun-Jong Oh Elizabeth E. Ebert Vincenzo Levizzani Eric A. Smith 《Meteorology and Atmospheric Physics》2009,105(1-2):99-108
In order to properly utilize remotely sensed precipitation estimates in hydrometeorological applications, knowledge of the accuracy of the estimates are needed. However, relatively few ground validation networks operate with the necessary spatial density and time-resolution required for validation of high-resolution precipitation products (HRPP) generated at fine space and time scales (e.g., hourly accumulations produced on a 0.25° spatial scale). In this article, we examine over-land validation statistics for an operationally designed, meteorological satellite-based global rainfall analysis that blends intermittent passive microwave-derived rainfall estimates aboard a variety of low Earth-orbiting satellite platforms with sub-hourly time sampling capabilities of visible and infrared imagers aboard operational geostationary platforms. The validation dataset is comprised of raingauge data collected from the dense, nearly homogeneous, 1-min reporting Automated Weather Station (network of the Korean Meteorological Administration during the June to August 2000 summer monsoon season. The space-time RMS error, mean bias, and correlation matrices were computed using various time windows for the gauge averaging, centered about the satellite observation time. For ±10 min time window, a correlation of 0.6 was achieved at 0.1° spatial scale by averaging more than 3 days; coarsening the spatial scale to 1.8° produced the same correlation by averaging over 1 h. Finer than approximately 24-h and 1° time and space scales, respectively, a rapid decay of the error statistics was obtained by trading-off either spatial or time resolution. Beyond a daily time scale, the blended estimates were nearly unbiased and with an RMS error of no worse than 1 mm day?1. 相似文献
882.
883.
A novel downscaling approach of the ERA40 (ECMWF 40-years reanalysis) data set has been taken and results for comparison with
observations in Norway are shown. The method applies a nudging technique in a stretched global model, focused in the Norwegian
Sea (67°N, 5°W). The effective resolution is three times the one of the ERA40, equivalent to about 30 km grid spacing in the
area of focus. Longer waves (<T42) in the downscaled solution are nudged towards the ERA40 solution, and thus the large-scale
circulation is similar in the two data sets. The shorter waves are free to evolve, and produce high intensities of winds and
precipitation. The comparison to observations incorporate numerous station data points of (1) precipitation (#357), (2) temperature
(#98) and (3) wind (#10), and for the period 1961–1990, the downscaled data set shows large improvements over ERA40. The daily
precipitation shows considerable reduction in bias (from 50 to 11%), and twofold reduction at the 99.9 percentile (from −59
to −29%). The daily temperature showed a bias reduction of about a degree in most areas, and relative large RMSE reduction
(from 7.5 to 5.0°C except winter). The wind comparison showed a slight improvement in bias, and significant improvements in
RMSE. 相似文献
884.
This article builds on the previous studies on storminess conditions in the northeast North Atlantic–European region. The period of surface pressure data analyzed is extended from 1881–1998 to 1874–2007. The seasonality and regional differences of storminess conditions in this region are also explored in more detail. The results show that storminess conditions in this region have undergone substantial decadal or longer time scale fluctuations, with considerable seasonal and regional differences. The most notable differences are seen between winter and summer, and between the North Sea area and other parts of the region. In particular, winter storminess shows an unprecedented maximum in the early 1990s in the North Sea area and a steady upward trend in the northeastern part of the region, while it appears to have declined in the western part of the region. In summer, storminess appears to have declined in most parts of this region. In the transition seasons, the storminess trend is characterized by increases in the northern part of the region and decreases in the southeastern part, with increases in the north being larger in spring. In particular, the results also show that the earliest storminess maximum occurred in summer (around 1880), while the latest storminess maximum occurred in winter (in the early 1990s). Looking at the annual metrics alone (as in previous studies), one would conclude that the latest storminess maximum is at about the same level as the earliest storminess maximum, without realizing that this is comparing the highest winter storminess level with the highest summer storminess level in the period of record analyzed, while winter and summer storminess conditions have undergone very different long-term variability and trends. Also, storminess conditions in the NE Atlantic region are found to be significantly correlated with the simultaneous NAO index in all seasons but autumn. The higher the NAO index, the rougher the NE Atlantic storminess conditions, especially in winter and spring. 相似文献
885.
Uncertainties in European summer precipitation changes: role of large scale circulation 总被引:2,自引:2,他引:0
Climate models suggest that anthropogenic emissions are likely to induce an important drying during summer over most of Europe in the late 21st century. However, the amplitude of the associated decrease in precipitation strongly varies among the different climate models. In order to reduce this spread, it is first necessary to identify its causes and the associated physical mechanisms. Consequently, the focus of this paper is to better estimate the role of large scale circulation (LSC) in precipitation changes over Europe using a multi-model framework and then to characterize the LSC changes using the weather regime paradigm. We show that LSC changes directly lead to a decrease of precipitation over northwestern Europe. This circulation-driven decrease in rainfall is mainly linked to an increase (decrease) of the occurrence of positive (negative) phase of the North Atlantic Oscillation regime. LSC is also responsible for a significant part of the models spread in precipitation changes over these regions. Over southern Europe, the role of LSC changes on multi-model mean precipitation changes is generally weak. We also show that the precipitation anomalies directly induced by LSC modifications seem to be further amplified through local feedbacks. 相似文献
886.
Detection of external influence on trends of atmospheric storminess and northern oceans wave heights 总被引:1,自引:0,他引:1
Xiaolan L. Wang Val R. Swail Francis W. Zwiers Xuebin Zhang Yang Feng 《Climate Dynamics》2009,32(2-3):189-203
The atmospheric storminess as inferred from geostrophic wind energy and ocean wave heights have increased in boreal winter over the past half century in the high-latitudes of the northern hemisphere (especially the northeast North Atlantic), and have decreased in more southerly northern latitudes. This study shows that these trend patterns contain a detectable response to anthropogenic and natural forcing combined. The effect of external influence is found to be strongest in the winter hemisphere, that is, in the northern hemisphere in January–March and in the southern hemisphere in July–September. However, the simulated response to anthropogenic and natural forcing combined, which was obtained directly from climate models in the case of geostrophic wind energy and indirectly via an empirical downscaling procedure in the case of ocean wave heights, is significantly weaker than the magnitude of the observed changes in these parameters. 相似文献
887.
We show that intermodel variations in the anthropogenically-forced evolution of September sea ice extent (SSIE) in the Arctic stem mainly from two factors: the baseline climatological sea ice thickness (SIT) distribution, and the local climate feedback parameter. The roles of these two factors evolve over the course of the twenty-first century. The SIT distribution is the most important factor in current trends and those of coming decades, accounting for roughly half the intermodel variations in SSIE trends. Then, its role progressively decreases, so that around the middle of the twenty-first century the local climate feedback parameter becomes the dominant factor. Through this analysis, we identify the investments in improved simulation of Arctic climate necessary to reduce uncertainties both in projections of sea ice loss over the coming decades and in the ultimate fate of the ice pack. 相似文献
888.
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
889.
Bernard Fontaine Javier Garcia-Serrano Pascal Roucou Belen Rodriguez-Fonseca Teresa Losada Fabrice Chauvin Sébastien Gervois Sivarajan Sijikumar Paolo Ruti Serge Janicot 《Climate Dynamics》2010,35(1):95-114
Using both empirical and numerical ensemble approaches this study focuses on the Mediterranean/West African relationship in
northern summer. Statistical analyses utilize skin temperature, sea surface temperature, in situ and satellite rainfall, outgoing
longwave radiation (OLR) observations and reanalyzed data winds and specific humidity on isobaric surfaces. Numerical investigations
are based on a large set of sensitivity experiments performed on four atmospheric general circulation models (AGCM): ARPEGE-Climat3,
ECHAM4, LMDZ4 and UCLA7.3. Model outputs are compared to observations, discussed model by model and with an ensemble (multi-model)
approach. As in previous studies the anomalous Mediterranean warm events are associated with specific impacts over the African
monsoon region, i.e., a more intense monsoon, enhanced flux convergence and ascendances around the ITCZ, a strengthening of
low level moisture advection and a more northward location of ascending motion in West Africa. The results show also new features
(1) thermal variability observed in the two Mediterranean basins has unalike impacts, i.e. the western Mediterranean covaries
with convection in Gulf of Guinea, while the eastern Mediterranean can be interpreted as Sahelian thermal-forcing; (2) although
observations show symmetry between warming and cooling, modelling evidences only support the eastern warming influence; (3)
anomalous East warm situations are associated with a more northward migration of the monsoon system accompanied by enhanced
southwertely flow and weakened northeasterly climatological wind; (4) the multi-model response shows that anomalous East warm
surface temperatures generate an enhancement of the overturning circulation in low and high levels, an increase in TEJ (Tropical
Eeasterly Jet) and a decrease in AEJ (African Eeasterly Jet). 相似文献
890.
Virginie Guemas David Salas-Mélia Masa Kageyama Hervé Giordani Aurore Voldoire Emilia Sanchez-Gomez 《Climate Dynamics》2010,34(4):527-546
This study aims at understanding the summer ocean-atmosphere interactions in the North Atlantic European region on intraseasonal
timescales. The CNRMOM1d ocean model is forced with ERA40 (ECMWF Re-Analysis) surface fluxes with a 1-h frequency in solar
heat flux (6 h for the other forcing fields) over the 1959–2001 period. The model has 124 vertical levels with a vertical
resolution of 1 m near the surface and 500 m at the bottom. This ocean forced experiment is used to assess the impact of the
North Atlantic weather regimes on the surface ocean. Composites of sea surface temperature (SST) anomalies associated with
each weather regime are computed and the mechanisms explaining these anomalies are investigated. Then, the SST anomalies related
to each weather regime in the ocean-forced experiment are prescribed to the ARPEGE Atmosphere General Circulation Model. We
show that the interaction with the surface ocean induces a positive feedback on the persistence of the Blocking regime, a
negative feedback on the persistence of the NAO-regime and favours the transition from the Atlantic Ridge regime to the NAO-regime
and from the Atlantic Low regime toward the Blocking regime. 相似文献