全文获取类型
收费全文 | 6589篇 |
免费 | 270篇 |
国内免费 | 118篇 |
专业分类
测绘学 | 208篇 |
大气科学 | 692篇 |
地球物理 | 1707篇 |
地质学 | 2793篇 |
海洋学 | 327篇 |
天文学 | 899篇 |
综合类 | 95篇 |
自然地理 | 256篇 |
出版年
2022年 | 48篇 |
2021年 | 95篇 |
2020年 | 82篇 |
2019年 | 64篇 |
2018年 | 206篇 |
2017年 | 196篇 |
2016年 | 288篇 |
2015年 | 197篇 |
2014年 | 300篇 |
2013年 | 386篇 |
2012年 | 320篇 |
2011年 | 267篇 |
2010年 | 307篇 |
2009年 | 364篇 |
2008年 | 268篇 |
2007年 | 234篇 |
2006年 | 197篇 |
2005年 | 212篇 |
2004年 | 150篇 |
2003年 | 124篇 |
2002年 | 145篇 |
2001年 | 132篇 |
2000年 | 116篇 |
1999年 | 104篇 |
1998年 | 124篇 |
1997年 | 91篇 |
1996年 | 99篇 |
1995年 | 78篇 |
1994年 | 89篇 |
1993年 | 64篇 |
1992年 | 53篇 |
1991年 | 51篇 |
1990年 | 54篇 |
1989年 | 49篇 |
1987年 | 50篇 |
1986年 | 44篇 |
1985年 | 51篇 |
1984年 | 58篇 |
1983年 | 77篇 |
1982年 | 59篇 |
1981年 | 52篇 |
1980年 | 50篇 |
1979年 | 51篇 |
1978年 | 50篇 |
1977年 | 47篇 |
1976年 | 42篇 |
1975年 | 53篇 |
1974年 | 43篇 |
1973年 | 55篇 |
1972年 | 42篇 |
排序方式: 共有6977条查询结果,搜索用时 234 毫秒
901.
Christian Pfister Emmanuel Garnier Maria-João Alcoforado Dennis Wheeler Jürg Luterbacher Maria Fatima Nunes João Paulo Taborda 《Climatic change》2010,101(1-2):281-310
Three violent eighteenth-century storms that ravaged the North Sea area (1703), western central Europe (1739) and Portugal (1739) are investigated from the point of view of their meteorological setting, their socio-economic impact, and whether and by what means they secured an enduring place in the cultural memory. The evidence draws on individual narrative sources such as chronicles and poems, and institutional sources such as ship’s logbooks and state-organised ‘windthrow’ inventories of tree loss. Each of the three storms had socio-economic impacts that could be described as ‘war-like’ in the damage caused to buildings and the destruction of forests. The “Great Storm” of December 1703 jeopardized English naval supremacy in the War of the Spanish Succession by sinking a number of Royal Navy ships and taking the life of more than 8000 seamen. In January 1739 two similarly destructive storms swept over mainland Europe. The cultural memory of the three events here considered was however strikingly different. The sequence of storms in January 1739 though being the most protracted of the last centuries, and well-chroniceled, did not persist in the collective memories of those in France, Switzerland and elsewhere who experienced them. Likewise, the “Great Storm” was quickly forgotten on the continent, whereas its memory remained deeply rooted in England through the writings of Defoe (1704). In Portugal the 1739 storm won a lasting place in the country’s cultural memory owing to two poems that it inspired. Furthermore, it was recorded in the Kingdom’s official newspaper, in the astronomical prognoses and in written records of the Old Regime’s cultural elite. 相似文献
902.
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
903.
Lisa M. Baldini Frank McDermott James U. L. Baldini Matthew J. Fischer Martin Möllhoff 《Climate Dynamics》2010,35(6):977-993
This two-year study investigates the relative influence of meteorological variables (precipitation amount and temperature),
atmospheric circulation, air mass history, and moisture source region on Irish precipitation oxygen isotopes (δ18Op) on event and monthly timescales. Single predictor correlations reveal that on the event scale, 20% of δ18Op variability is attributable to the amount effect and 7% to the temperature effect while on the monthly timescale the North
Atlantic Oscillation accounts for up to 20% of δ18Op variability and the amount and temperature effects are not significant. In comparison, multivariate linear regression reveals
that the interaction of temperature and precipitation amount explains up to 40% of δ18Op variance at event and monthly timescales. Five-day kinematic back trajectories suggest that the amount-weighted mean δ18Op value of southerly- and northerly-derived events are lower by 2‰ relative to events derived from the west. Because air mass
history and atmospheric circulation appear to influence δ18Op in Ireland, Irish paleo-δ18Op proxy records are best interpreted as reflecting a combination of parameters, not just paleotemperature or paleorainfall. 相似文献
904.
Frédéric Vivier Daniele Iudicone Fabiano Busdraghi Young-Hyang Park 《Climate Dynamics》2010,34(2-3):153-184
We analyze the processes responsible for the generation and evolution of sea-surface temperature anomalies observed in the Southern Ocean during a decade based on a 2D diagnostic mixed-layer model in which geostrophic advection is prescribed from altimetry. Anomalous air–sea heat flux is the dominant term of the heat budget over most of the domain, while anomalous Ekman heat fluxes account for 20–40% of the variance in the latitude band 40°?60°S. In the ACC pathway, lateral fluxes of heat associated with anomalous geostrophic currents are a major contributor, dominating downstream of several topographic features, reflecting the influence of eddies and frontal migrations. A significant fraction of the variability of large-scale SST anomalies is correlated with either ENSO or the SAM, each mode contributing roughly equally. The relation between the heat budget terms and these climate modes is investigated, showing in particular that anomalous Ekman and air–sea heat fluxes have a co-operating effect (with regional exceptions), hence the large SST response associated with each mode. It is further shown that ENSO- or SAM-locked anomalous geostrophic currents generate substantial heat fluxes in all three basins with magnitude comparable with that of atmospheric forcings for ENSO, and smaller for the SAM except for limited areas. ENSO-locked forcings generate SST anomalies along the ACC pathway, and advection by mean flows is found to be a non-negligible contribution to the heat budget, exhibiting a wavenumber two zonal structure, characteristic of the Antarctic Circumpolar Wave. By contrast SAM-related forcings are predominantly zonally uniform along the ACC, hence smaller zonal SST gradients and a lesser role of mean advection, except in the SouthWest Atlantic. While modeled SST anomalies are significantly correlated with observations over most of the Southern Ocean, the analysis of the data-model discrepancies suggests that vertical ocean physics may play a significant role in the nonseasonal heat budget, especially in some key regions for mode water formation. 相似文献
905.
闭合气压系统中心位置指数的计算方案 总被引:1,自引:1,他引:0
王盘兴等在"闭合气压系统环流指数的定义及计算"一文中定义了闭合气压系统的面积指数S、强度指数P和中心位置指数(λc,φc),并给出了它们的计算方案。但其中(λc,φc)的计算方案对低纬系统的计算存在明显误差,误差原因是原方案中的极点球面坐标系不适合低纬系统的计算。本文建立了一套原点位于搜索区Ω中心的新球面坐标系,通过坐标转换实现了低纬闭合气压系统中心位置指数(λc,φc)的准确计算。对7月南亚高压和1月蒙古高压中心位置指数(λc,φc)的实际计算表明,它既消除了低纬系统(南亚高压)(λc,φc)原计算方案的明显误差,又保持了与高纬系统(蒙古高压)(λc,φc)原计算方案计算结果的一致。因此,本文给出了适于计算任意纬度闭合气压系统中心位置指数(λc,φc)的计算方案。 相似文献
906.
Based upon comparisons between published experimental data and simulated results on the vertical sand flux distribution in
the saltation layer, Shao’s similarity saltation model has been greatly improved by correcting the average vertical particle
lift-off velocity and using a more suitable universal roughness length. By the improved model, the vertical sand flux profile
over the bare, dry and loose uniform sandy surface, which is quite representative of real desert surfaces, can be reproduced
very well. Meanwhile, the surface transport rate and the characteristic and average saltation heights have been simulated
and analyzed in detail, disclosing their relationships with friction velocity, particle size and roughness length, and the
possible underlying mechanisms. Besides, the average particle lift-off velocity and the average mean vertical aerodynamic
action upon the ascending particle, which determine the saltation process, are explicitly expressed by parameters involved
in the similarity model, and their relationships with friction velocity, particle size and roughness length are also described
concisely. The corrected average particle lift-off velocity makes it possible to investigate the characteristic particle trajectory,
whose initial velocity equals the average lift-off velocity, so as to estimate the average particle against surface impacting
velocity and the average aerodynamic action upon the saltation process. 相似文献
907.
J. F. Barlow G. G. Rooney S. von Hünerbein S. G. Bradley 《Boundary-Layer Meteorology》2008,127(2):173-191
Profiles of wind and turbulence over an urban area evolve with fetch in response to surface characteristics. Sodar measurements,
taken on 22 April 2002 during the Salford Experiment in the UK (Salfex), are here related to upstream terrain. A logarithmic
layer up to z = 65m was observed in all half-hour averaged profiles. Above this height the profile showed a different vertical gradient,
suggesting a change in surface cover upstream. The drag coefficient varied by a factor of two over only a 20° direction change.
Turbulence intensity (σ
x
) for each wind component (x) decreased with height, but the ratio suggested an underestimate of σ
u
compared to previous results. Mean urban and suburban cover fraction within the source area for each height decreased sharply
between z = 20 and 50m, increasing slightly above. The near-convergence of cover fractions thus occured for source areas of minimum
length ≈ 2,200 m. In comparison, the mean length scale of heterogeneity L
P was calculated from surface cover data to be 1,284 m, and the corresponding mean blending height h
b was 175 m. Finally, the mean streamline angle, α, was negative and the magnitude decreased with height. An exponential fit
to α for z ≤ 65m gave an e-folding height scale of 159 m. A simple relationship between this height scale and L
P was assumed, giving L
P ≈ 1,080 m, which is in reasonable agreement with the estimate from surface cover type. The results suggest that more emphasis
is required on modelling and measuring surface-layer flow over heterogeneous urban canopies. 相似文献
908.
We derive a conceptual model of the flow over heterogeneous terrain consisting of patches with contrasting Bowen ratios. Upward
moving eddies are assumed to carry heterogeneous properties, whereas downward moving eddies carry homogeneous properties.
This results in a decorrelation of temperature and humidity as the contrast between the patches increases. We show that this
model is able to reproduce the relationship developed by Lamaud and Irvine (Boundary-Layer Meteorol. 120:87–109, 2006). Some
details differ from their expression but are in accordance with data obtained over African savannah. We extend the conceptual
model to a combination of any scalars, not necessarily linked through the surface energy balance (as is the case for temperature
and humidity). To this end we introduce a new parameter that describes the surface heterogeneity in surface fluxes. The results
of the current model can be used to predict the discrepancy between similarity relationships for different scalars over heterogeneous
terrain. 相似文献
909.
910.
Jacqueline Flückiger Reto Knutti James W. C. White Hans Renssen 《Climate Dynamics》2008,31(6):633-645
Greenland ice cores, as well as many other paleo-archives from the northern hemisphere, recorded a series of 25 warm interstadial
events, the so-called Dansgaard-Oeschger (D-O) events, during the last glacial period. We use the three-dimensional coupled
global ocean–atmosphere–sea ice model ECBILT-CLIO and force it with freshwater input into the North Atlantic to simulate abrupt
glacial climate events, which we use as analogues for D-O events. We focus our analysis on the Northern Hemisphere. The simulated
events show large differences in the regional and seasonal distribution of the temperature and precipitation changes. While
the temperature changes in high northern latitudes and in the North Atlantic region are dominated by winter changes, the largest
temperature increases in most other land regions are seen in spring. Smallest changes over land are found during the summer
months. Our model simulations also demonstrate that the temperature and precipitation change patterns for different intensifications
of the Atlantic meridional overturning circulation are not linear. The extent of the transitions varies, and local non-linearities
influence the amplitude of the annual mean response as well as the response in different seasons. Implications for the interpretation
of paleo-records are discussed. 相似文献