全文获取类型
收费全文 | 28629篇 |
免费 | 492篇 |
国内免费 | 248篇 |
专业分类
测绘学 | 610篇 |
大气科学 | 2234篇 |
地球物理 | 5896篇 |
地质学 | 9896篇 |
海洋学 | 2318篇 |
天文学 | 6348篇 |
综合类 | 53篇 |
自然地理 | 2014篇 |
出版年
2021年 | 211篇 |
2020年 | 260篇 |
2019年 | 268篇 |
2018年 | 564篇 |
2017年 | 545篇 |
2016年 | 675篇 |
2015年 | 527篇 |
2014年 | 701篇 |
2013年 | 1400篇 |
2012年 | 850篇 |
2011年 | 1168篇 |
2010年 | 991篇 |
2009年 | 1356篇 |
2008年 | 1195篇 |
2007年 | 1187篇 |
2006年 | 1104篇 |
2005年 | 926篇 |
2004年 | 925篇 |
2003年 | 894篇 |
2002年 | 817篇 |
2001年 | 738篇 |
2000年 | 692篇 |
1999年 | 613篇 |
1998年 | 612篇 |
1997年 | 608篇 |
1996年 | 472篇 |
1995年 | 450篇 |
1994年 | 401篇 |
1993年 | 362篇 |
1992年 | 323篇 |
1991年 | 293篇 |
1990年 | 321篇 |
1989年 | 310篇 |
1988年 | 247篇 |
1987年 | 334篇 |
1986年 | 272篇 |
1985年 | 377篇 |
1984年 | 402篇 |
1983年 | 395篇 |
1982年 | 349篇 |
1981年 | 333篇 |
1980年 | 324篇 |
1979年 | 298篇 |
1978年 | 328篇 |
1977年 | 273篇 |
1976年 | 275篇 |
1975年 | 282篇 |
1974年 | 247篇 |
1973年 | 250篇 |
1972年 | 163篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
971.
P. Braconnot F. Hourdin S. Bony J. L. Dufresne J. Y. Grandpeix O. Marti 《Climate Dynamics》2007,29(5):501-520
The simulation of the mean seasonal cycle of sea surface temperature (SST) remains a challenge for coupled ocean–atmosphere
general circulation models (OAGCMs). Here we investigate how the numerical representation of clouds and convection affects
the simulation of the seasonal variations of tropical SST. For this purpose, we compare simulations performed with two versions
of the same OAGCM differing only by their convection and cloud schemes. Most of the atmospheric temperature and precipitation
differences between the two simulations reflect differences found in atmosphere-alone simulations. They affect the ocean interior
down to 1,000 m. Substantial differences are found between the two coupled simulations in the seasonal march of the Intertropical
Convergence Zone in the eastern part of the Pacific and Atlantic basins, where the equatorial upwelling develops. The results
confirm that the distribution of atmospheric convection between ocean and land during the American and African boreal summer
monsoons plays a key role in maintaining a cross equatorial flow and a strong windstress along the equator, and thereby the
equatorial upwelling. Feedbacks between convection, large-scale circulation, SST and clouds are highlighted from the differences
between the two simulations. In one case, these feedbacks maintain the ITCZ in a quite realistic position, whereas in the
other case the ITCZ is located too far south close to the equator. 相似文献
972.
Extreme midlatitude cyclone characteristics, precipitation, wind speed events, their inter-relationships, and the connection
to large-scale atmospheric patterns are investigated in simulations of a prolonged cold period, known as the Maunder Minimum
from 1640 to 1715 and compared with today. An ensemble of six simulations for the Maunder Minimum as well as a control simulation
for perpetual 1990 conditions are carried out with a coupled atmosphere-ocean general circulation model, i.e., the Climate
Community System Model (CCSM). The comparison of the simulations shows that in a climate state colder than today the occurrence
of cyclones, the extreme events of precipitation and wind speed shift southward in all seasons in the North Atlantic and the
North Pacific. The extremes of cyclone intensity increases significantly in winter in almost all regions, which is related
to a stronger meridional temperature gradient and an increase in lower tropospheric baroclinicity. Extremes of cyclone intensity
in subregions of the North Atlantic are related to extremes in precipitation and in wind speed during winter. Moreover, extremes
of cyclone intensity are also connected to distinct large-scale atmospheric patterns for the different subregions, but these
relationships vanish during summer. Analyzing the mean 1,000 hPa geopotential height change of the Maunder Minimum simulations
compared with the control simulation, we find a similar pattern as the correlation pattern with the cyclone intensity index
of the southern Europe cyclones. This illustrates that changes in the atmospheric high-frequency, i.e., the simulated southward
shift of cyclones in the North Atlantic and the related increase of extreme precipitation and wind speed in particular in
the Mediterranean in winter, are associated with large-scale atmospheric circulation changes. 相似文献
973.
T. Naszradi A. Badacsonyi N. Németh Z. Tuba F. Batiĉ 《Journal of Atmospheric Chemistry》2004,49(1-3):593-603
The heavy metal content was investigated in meadow plants located in a cultivated area and situated along the M3 motorway (Hungary). In addition to the meadow plants used as passive bioindicators, active bioindicators were also exposed to examine the accumulation rate of air pollutants. Tortula ruralis (Hedw.) Geartn. ssp. ruralis was applied to monitor the status of the environment. Meadow plant samples were collected at distances of 5, 10, 25, 50 and 100 m from the motorway and moss samples were exposed at the same distances. The zinc, lead and cadmium content of meadow plants and moss samples were analysed by ICP spectrophotometry. It was found that the zinc, lead and cadmium contents of the meadow plants decreased as the distance increased from the motorway. There was a significant difference even between values measured at the distances of 5 m and 10 m. The heavy metal contents in the moss samples exceeded those of the meadow plants. The heavy metal content in moss samples decreased with distance from the motorway. On comparing the data with Hungarian standards, it was found that measured values did not exceed the maximum allowed concentration levels. 相似文献
974.
R. D. Kouznetsov V. F. Kramar F. Beyrich D. Engelbart 《Meteorology and Atmospheric Physics》2004,85(1-3):93-99
Summary A simple parameterization for the estimation of turbulent kinetic energy (TKE) and momentum flux profiles under near-neutral stratification based on sodar measurements of the vertical velocity variance has been tested using data from the LINEX-2000 experiment. Measurements included operation of a phased-array Doppler sodar DSDPA.90 and of a sonic anemometer USA-1 mounted at a meteorological tower at a height of 90m. Good agreement has been found between the TKE and momentum flux values derived from the sonic and sodar data (with correlation coefficients r>0.90 and a slope of the regression lines of about 1.01.1) suggesting the possible use of sodar measurements of w 2 to derive turbulence parameter profiles above the tower range. 相似文献
975.
976.
977.
F. N. Lisetskii Ya. V. Pavlyuk Zh. A. Kirilenko V. I. Pichura 《Russian Meteorology and Hydrology》2014,39(8):550-557
Presented are the development of the concept and projects of the basin nature management and the organization of their implementation in the whole region using the basin-administrative approach. Based on the multidimensional analysis and forecast of river runoff variations using the artificial neural networks, the typification of catchments is carried out mainly defined by such factors as its area, order of the river, and degree of anthropogenic load. Depending on the hydrological functioning type, the adapted complexes of Hydroecological activities are determined. The need in the integration of the geodata for each river basin with the inherent morphological and process characteristics as well as of the results of Hydroecological monitoring enables to recommend the structure of the database of the basin organization of nature management in the regions of Russia based on the European experience in the river network monitoring in the context of the EU Water Framework Directive and of the creation of the single infrastructure of the spatial data. 相似文献
978.
J.?García-SerranoEmail author V.?Guemas F.?J.?Doblas-Reyes 《Climate Dynamics》2015,44(9-10):2539-2555
Identifying regions sensitive to external radiative changes, including anthropogenic (sulphate aerosols and greenhouse gases) and natural (volcanoes and solar variations) forcings, is important to formulate actionable information at multi-year time-scales. Internally-generated climate variability can overcome this radiative forcing, especially at regional level, so that detecting the areas for this potential dominance is likewise critical for decadal prediction. This work aims to clarify where each contribution has the largest effect on North Atlantic sea surface temperature (SST) predictions in relation to the Atlantic multi-decadal variability (AMV). Initialized decadal hindcasts and radiatively-forced historical simulations from the fifth phase of the Climate Model Intercomparison Project are analysed to assess multi-year skill of the AMV. The initialized hindcasts reproduce better the phase of the AMV index fluctuations. The radiatively-forced component consists of a residual positive trend, although its identification is ambiguous. Initialization reduces the inter-model spread when estimating the level of AMV skill, thus reducing its uncertainty. Our results show a skilful performance of the initialized hindcasts in capturing the AMV-related SST anomalies over the subpolar gyre and Labrador Sea regions, as well as in the eastern subtropical basin, and the inability of the radiatively-forced historical runs to simulate the horseshoe-like AMV signature over the North Atlantic. Initialization outperforms empirical predictions based on persistence beyond 1–4 years ahead, suggesting that ocean dynamics play a role in the AMV predictability beyond the thermal inertia. The initialized hindcasts are also more skilful at reproducing the observed AMV teleconnection to the West African monsoon. The impact of the start date frequency is also described, showing that the standard of 5-year interval between start dates yields the main features of the AMV skill that are robustly detected in hindcasts with yearly start date sampling. This work updates previous studies, complementing them, and concludes that skilful initialized multi-model forecasts of the AMV-related climate variability can be formulated, improving uninitialized projections, until 3–6 years ahead. 相似文献
979.
R. García-Herrera D. Barriopedro E. Hernández D. Paredes J. F. Correoso L. Prieto 《Meteorology and Atmospheric Physics》2005,90(3-4):225-243
Summary This paper characterizes Mesoscale Convective Systems (MCSs) during 2001 over Iberia and the Balearic Islands and their meteorological
settings. Enhanced infrared Meteosat imagery has been used to detect their occurrence over the Western Mediterranean region
between June and December 2001 according to satellite-defined criteria based on the MCS physical characteristics.
Twelve MCSs have been identified. The results show that the occurrence of 2001 MCSs is limited to the August–October period,
with September being the most active period. They tend to develop during the late afternoon or early night, with preferred
eastern Iberian coast locations and eastward migrations. A cloud shield area of 50.000 km2 is rarely exceeded. When our results are compared with previous studies, it is possible to assert that though 2001 MCS activity
was moderate, the convective season was substantially less prolonged than usual, with shorter MCS life cycles and higher average
speeds. The average MCS precipitation rate was 3.3 mm·h−1 but a wide range of values varying from scarce precipitation to intense events of 130 mm·24 h−1 (6 September) were collected. The results suggest that, during 2001, MCS rainfall was the principal source of precipitation
in the Mediterranean region during the convective season, but its impact varied according to the location.
Synoptic analysis based on NCEP/NCAR reanalysis show that several common precursors could be identified over the Western Mediterranean
Sea when the 2001 MCSs occurred: a low-level tongue of moist air and precipitable water (PW) exceeding 25 mm through the southern
portion of the Western Mediterranean area, low-level zonal warm advection over 2 °C·24 h−1 towards eastern Iberia, a modest 1000–850 hPa equivalent potential temperature (θe) difference over 20 °C located close to the eastern Iberian coast, a mid level trough (sometimes a cut-off low) over Northern
Africa or Southern Spain and high levels geostrophic vorticity advection exceeding 12·10−10 s−2 over eastern Iberia and Northern Africa. Finally, the results suggest that synoptic, orographic and a warm-air advection
were the most relevant forcing mechanisms during 2001. 相似文献
980.
William F. Ruddiman 《Climatic change》2005,69(2-3):427-434