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991.
以东亚酸沉降监测网近地面O3资料,结合NCEP/NCAR的全球再分析风场、NOAA总云量及全球降水气候项目降水资料,分析2000~2007年东亚西太平洋地区近地层O3的区域和季节变化,重点分析不同站点O3月均浓度最大值时间差异的原因。结果表明,东亚以及大部分北半球中纬度清洁背景地区,近地层O3春季最高、夏季最低是广泛存在的现象。东亚夏季风的推进过程造成不同地区春季O3月均最大值出现的时间略有不同,Ogasawara和Hedo站O3浓度在3月达最大值,而Rishiri、Happo、Oki和Cheju站在4、5月达最大值。2007年副热带高压西进较晚且推进过程受阻导致Happo站2007年春季O3浓度高于气候平均值,Cheju地区2007年5月O3浓度达最大;2004年东亚夏季风爆发较早导致Hedo站2004年春季O3浓度明显低于平均值。 相似文献
992.
993.
东亚夏季风建立前青藏高原地气温差变化特征 总被引:6,自引:1,他引:5
利用青藏高原地区112个站1980~2001年和部分站点1960~2000年的气温、地温资料,采用经验正交EOF和旋转经验正交REOF等方法,对东亚夏季风爆发前青藏高原地气温差的变化特征进行分析,并对其与东亚夏季风之间的联系进行了分析.结果表明,青藏高原地气温差一般超前气温、地温1个月达到全年最大值,比中国中东部同纬度... 相似文献
994.
海陆热力差异的季节性变化是季风产生的原始驱动力,因此海洋和大陆任何一方的变化必然会影响季风环流出现异常。本文探讨了欧亚大陆高、低层气温、南亚大陆和印度洋之间海陆热力差异的变化特征,发现南亚大陆的印度半岛区域下垫面的季节性增暖出现最早,其增暖从春季就开始出现,比对流层上层增暖偏早约两个月,相应的低层经向海陆温度梯度由冬季型转为夏季型最早的区域出现在80°E附近。进一步分析了印度半岛下垫面热力异常的变化特征及其与季风环流异常的关系,初步揭示了南亚区域高、低层气温变化的相互联系,发现印度半岛下垫面的迅速增温引起了大气的强感热加热,进而影响高、低层季风环流的异常变化。结果表明,春末夏初印度半岛暖下垫面的加热作用有利于亚洲夏季型季风环流建立偏早,同时也有利于亚洲夏季季风环流的加强,而冷下垫面的作用则相反。 相似文献
995.
Based on reconstructions of precipitation events from the rain and snowfall archives of the Qing Dynasty (1736–1911),the drought/flood index data mainly derived from Chinese local gazettes from 1736–2000, and the observational data gathered since 1951,the spatial patterns of monsoon rainbands are analyzed at different time scales.Findings indicate that monsoon rainfall in northern China and the middle-lower reaches of the Yangtze River have significant inter-annual(e.g.,5–7-yr and 2–4-yr)as well as inter-de... 相似文献
996.
Improving multimodel weather forecast of monsoon rain over China using FSU superensemble 总被引:3,自引:0,他引:3
In this paper we present the current capabilities for numerical weather prediction of precipitation
over China using a suite of ten multimodels and our superensemble based forecasts. Our suite of models includes
the operational suite selected by NCARs TIGGE archives for the THORPEX Program. These are: ECMWF, UKMO, JMA,
NCEP, CMA, CMC, BOM, MF, KMA and the CPTEC models. The superensemble strategy includes a training and a forecasts
phase, for these the periods chosen for this study include the months February through September for the years 2007
and 2008. This paper addresses precipitation forecasts for the medium range i.e. Days 1 to 3 and extending out to
Day 10 of forecasts using this suite of global models. For training and forecasts validations we have made use of
an advanced TRMM satellite based rainfall product. We make use of standard metrics for forecast validations that
include the RMS errors, spatial correlations and the equitable threat scores. The results of skill forecasts of
precipitation clearly demonstrate that it is possible to obtain higher skills for precipitation forecasts for Days
1 through 3 of forecasts from the use of the multimodel superensemble as compared to the best model of this suite.
Between Days 4 to 10 it is possible to have very high skills from the multimodel superensemble for the RMS error of
precipitation. Those skills are shown for a global belt and especially over China. Phenomenologically this product
was also found very useful for precipitation forecasts for the Onset of the South China Sea monsoon, the life cycle
of the mei-yu rains and post typhoon landfall heavy rains and flood events. The higher skills of the multimodel
superensemble make it a very useful product for such real time events. 相似文献
997.
998.
利用大气环流、海洋、天文以及宜昌单站气象资料,对2008年初宜昌市出现的低温雨雪冰冻灾害成因进行分析.结果表明,2008年1月欧亚地区出现持续而稳定的大气环流异常形势,是导致2008年初宜昌市乃至我国南方大范嗣持续低温雨雪冰冻灾害天气的直接原因.南海夏季风的季节转换偏迟与这次灾害天气的出现有着密不可分的关系.拉尼娜事件对这次过程的发生发展起到了推波助澜的作用.太阳黑子的异常活动对这次灾害天气的影响是不可忽视的一个重要因素. 相似文献
999.
How Well do Existing Indices Measure the Strength of the East Asian Winter Monsoon? 总被引:44,自引:7,他引:37
Defining the intensity of the East Asian winter monsoon (EAWM) with a simple
index has been a difficult task. This paper elaborates on the meanings of 18
existing EAWM strength indices and classifies them into four categories: low
level wind indices, upper zonal wind shear indices, east-west pressure
contrast indices, and East Asian trough indices. The temporal/spatial
performance and prediction potential of these indices are then analyzed for
the 1957--2001 period. It reveals that on the decadal timescale, most
indices except the east--west pressure contrast indices can well capture the
continuous weakening of the EAWM around 1986. On the interannual timescale,
the low level wind indices and East Asian trough indices have the best
predictability based on knowledge of the El Nino-Southern Oscillation
and Arctic Oscillation, respectively. All the 18 existing indices can well
describe the EAWM-related circulation, precipitation, and lower tropospheric
air temperature anomalies. However, the variations of surface air
temperature over large areas of central China cannot be well captured by
most indices, which is possibly related to topographic effects. The results
of this study may provide a possible reference for future studies of the
EAWM. 相似文献
1000.
The Role of Land–sea Distribution and Orography in the Asian Monsoon. Part I: Land–sea Distribution 总被引:3,自引:3,他引:0
A number of AGCM simulations were performed by including various land--sea
distributions (LSDs), such as meridional LSDs, zonal LSDs, tropical
large-scale LSDs, and subcontinental-scale LSDs, to identify their effects
on the Asian monsoon. In seven meridional LSD experiments with the
continent/ocean located to the north/south of a certain latitude, the LSDs
remain identical except the southern coastline is varied from 40o to
4oN in intervals of 5.6o. In the experiments with the coastline
located to the north of 21oN, no monsoon can be found in the subtropical
zone. In contrast, a summer monsoon is simulated when the continent extends
to the south of 21oN. Meanwhile, the earlier onset and stronger
intensity of the tropical summer monsoon are simulated with the southward
extension of the tropical continent. The effects of zonal LSDs were
investigated by including the Pacific and Atlantic Ocean into the model
based on the meridional LSD run with the coastline located at 21oN. The
results indicate that the presence of a mid-latitude zonal LSD induces a
strong zonal pressure gradient between the continent and ocean, which in
turn results in the formation of an East Asian subtropical monsoon. The
comparison of simulations with and without the Indian Peninsula and
Indo-China Peninsula reveals that the presence of two peninsulas remarkably
strengthens the southwesterly winds over South Asia due to the tropical
asymmetric heating between the tropical land and sea. The tropical zonal LSD
plays a crucial role in the formation of cumulus convection. 相似文献