全文获取类型
收费全文 | 6267篇 |
免费 | 1216篇 |
国内免费 | 1750篇 |
专业分类
测绘学 | 549篇 |
大气科学 | 1107篇 |
地球物理 | 1561篇 |
地质学 | 3537篇 |
海洋学 | 992篇 |
天文学 | 161篇 |
综合类 | 632篇 |
自然地理 | 694篇 |
出版年
2024年 | 38篇 |
2023年 | 147篇 |
2022年 | 273篇 |
2021年 | 311篇 |
2020年 | 264篇 |
2019年 | 291篇 |
2018年 | 340篇 |
2017年 | 303篇 |
2016年 | 341篇 |
2015年 | 347篇 |
2014年 | 406篇 |
2013年 | 398篇 |
2012年 | 480篇 |
2011年 | 466篇 |
2010年 | 514篇 |
2009年 | 485篇 |
2008年 | 428篇 |
2007年 | 416篇 |
2006年 | 386篇 |
2005年 | 313篇 |
2004年 | 294篇 |
2003年 | 237篇 |
2002年 | 199篇 |
2001年 | 201篇 |
2000年 | 209篇 |
1999年 | 191篇 |
1998年 | 145篇 |
1997年 | 158篇 |
1996年 | 114篇 |
1995年 | 99篇 |
1994年 | 85篇 |
1993年 | 68篇 |
1992年 | 61篇 |
1991年 | 51篇 |
1990年 | 43篇 |
1989年 | 30篇 |
1988年 | 24篇 |
1987年 | 20篇 |
1986年 | 17篇 |
1985年 | 9篇 |
1984年 | 5篇 |
1983年 | 6篇 |
1982年 | 5篇 |
1981年 | 2篇 |
1980年 | 3篇 |
1979年 | 1篇 |
1968年 | 1篇 |
1958年 | 4篇 |
1954年 | 4篇 |
排序方式: 共有9233条查询结果,搜索用时 15 毫秒
851.
Observational and Modeling Studies of Impacts of the South China Sea Monsoon on the Monsoon Rainfall in the Middle-Lower Reaches of the Yangtze River During Summer 总被引:1,自引:0,他引:1 下载免费PDF全文
Based on the ERA-40 and NCEP/NCAR reanalysis data,the NOAA Climate Prediction Center’s merged analysis of precipitation(CMAP),and the fifth-generation PSU/NCAR Mesoscale Model version 3(MM5v3),we defined a monsoon intensity index over the East Asian tropical region and analyzed the impacts of summer(June-July) South China Sea(SCS) monsoon anomaly on monsoon precipitation over the middle-lower reaches of the Yangtze River(MLRYR) using both observational data analysis and numerical simulation methods.The results from the data analysis show that the interannual variations of the tropical monsoon over the SCS are negatively correlated with the southwesterly winds and precipitation over the MLRYR during June-July.Corresponding to stronger(weaker) tropical monsoon and precipitation,the southwesterly winds are weaker(stronger) over the MLRYR,with less(more) local precipitation.The simulation results further exhibit that when changing the SCS monsoon intensity,there are significant variations of monsoon and precipitation over the MLRYR.The simulated anomalies generally consist with the observations,which verifies the impact of the tropical monsoon on the monsoon precipitation over the MLRYR.This impact might be supported by certain physical processes.Moreover,when the tropical summer monsoon is stronger,the tropical anomalous westerly winds and positive precipitation anomalies usually maintain in the tropics and do not move northward into the MLRYR,hence the transport of water vapor toward southern China is weakened and the southwest flow and precipitation over southern China are also attenuated.On the other hand,the strengthened tropical monsoon may result in the weakening and southward shift of the western Pacific subtropical high through self-adjustment of the atmospheric circulation,leading to the weakening of the monsoon flows and precipitation over the MLRYR. 相似文献
852.
利用NCEP、ERA-40再分析资料和中国160个观测站逐月降水资料,分析了同期和前期亚洲-太平洋涛动(APO)与中国南方地区冬季1月降水异常的关系,并讨论了相应的联系机制.研究发现,1月亚洲-太平洋涛动指数能够很好地反映同期中国南方地区降水异常.亚洲-太平洋涛动的异常变化可能影响对流层低层位势高度场,进而通过影响亚洲中、低纬度地区的对流层低层风场与中国南方地区降水紧密联系.当亚洲-太平洋涛动指数偏低(高)时,对应在东亚南部及其邻近海域对流层低层位势高度偏高(低),东太平洋位势高度偏低(高).相应地,南海以及华南沿海地区为异常西南(东北)风控制,且该异常风向北逐渐减弱,进而在中国南方地区辐合(辐散),这既有(不)利于暖湿气流向中国南方地区输送,同时也造成了该地区的水汽辐合(辐散),从而导致降水偏多(少).亚洲-太平洋涛动具有很好的持续性,上一年10月亚洲-太平洋涛动异常可一直持续至当年1月,表现出连续的显着相关特征.因此,其与中国南方地区1月降水异常也具有显着联系,可以作为指示1月中国南方地区降水多寡的一个前兆因子. 相似文献
853.
854.
考虑一个方程和非线性边界条件耦合的半线性抛物型方程组,运用Scaling方法、Green函数、Schauder估计等方法,研究该方程组解的爆破速率,并给出非线性反应项和吸收项对爆破速率的影响。 相似文献
855.
856.
HE Jinhai ZHAO Ping ZHU Congwen ZHANG Renhe TANG Xu CHEN Longxun ZHOU Xiuji 《Acta Meteorologica Sinica》2008,22(4):419-434
Based on NCEP/NCAR gridded reanalysis, TRMM precipitation data, CMAP, and rainfall observations in East China, a study is conducted with focus on the timing and distinctive establishment of the rainy season of the East Asian subtropical monsoon (EASM) in relation to the South China Sea (SCS) tropical summer monsoon (SCSM). A possible mechanism for the EASM is investigated. The results suggest that 1) the EASM rainy season begins at first over the south of the Jiangnan region to the north of South China in late March to early April (i.e., pentads 16-18), and then the early flooding period in South China starts when southerly winds enhance and convective rainfall increases pronouncedly; 2) the establishment of the EASM rainy season is earlier than that of its counterpart, the SCSM. The EASM and the SCSM each is featured with its own independent rain belt, strong southwesterly wind, intense vertical motion, and robust low-level water vapor convergence. The SCSM interacts with the EASM, causing the EASM rainy belt to move northward. The two systems are responsible for the floods/droughts over the eastern China; and 3) in mid-late March, the eastern Asian landmass (especially the Tibetan Plateau) has its thermal condition changing from a cold to a heat source for the atmosphere. A reversal of the zonal thermal contrast and related temperature and pressure contrasts between the landmass and the western Pacific happens. The argument about whether or not the dynamic and thermal effects of the landmass really act as a mechanism for the earlier establishment of the EASM rain belt is discussed and to be further clarified. Finally, the article presents some common understandings and disagreements regarding the EASM. 相似文献
857.
858.
江苏冬夏季人体舒适度指数异常的背景场研究 总被引:2,自引:1,他引:2
利用江苏地区37个气象观测站1980—2009年逐日资料,及同时段美国NCEP/NCAR再分析资料以及北太平洋海温资料,通过合成和遥相关法,研究了当江苏冬、夏季人体舒适度指数(CIHB)出现异常偏高和偏低时,大气环流与北太平洋海温场的基本特征。结果表明:(1)CIHB偏高年较偏低年,冬季,东亚大槽偏浅,冬季风明显偏弱,尤其是北风分量偏弱最为明显,江苏上空下沉气流偏弱,均不利于冷空气东移南压以及向下入侵;夏季,副热带高压偏西、偏强,南亚高压偏东、偏北、偏强,夏季风明显偏强,尤其是南风分量偏强显著,导致往北的暖湿气流强盛,垂直运动总体偏弱,不利于夏季对流活动的发生。(2)冬季,CIHB偏高年中西太平洋的海温高于偏低年,尤其是在我国东部近海的黑潮区,偏暖幅度最为明显,无论是超前相关还是同期相关,西太平洋海温与冬季CIHB都是以正相关为主,其中暖池区的正相关最为显著。 相似文献
859.
Modulation of Western North Pacific Tropical Cyclone Genesis by
Intraseasonal Oscillation of the ITCZ: A Statistical Analysis 总被引:1,自引:0,他引:1
The present study investigates modulation of western North Pacific(WNP) tropical cyclone(TC) genesis in relation to different phases of the intraseasonal oscillation(ISO) of ITCZ convection during May to October in the period 1979-2008.The phases of the ITCZ ISO were determined based on 30-80-day filtered OLR anomalies averaged over the region(5-20 N,120-150 E).The number of TCs during the active phases was nearly three times more than during the inactive phases.The active(inactive) phases of ISO were characterized by low-level cyclonic(anticyclonic) circulation anomalies,higher(lower) midlevel relative humidity anomalies,and larger(smaller) vertical gradient anomalies of relative vorticity associated with enhanced(weakened) ITCZ convection anomalies.During the active phases,TCs tended to form in the center of the ITCZ region.Barotropic conversion from the low-level mean flow is suggested to be the major energy source for TC formation.The energy conversion mainly depended on the zonal and meridional gradients of the zonal flow during the active phases.However,barotropic conversion weakened greatly during the inactive phases.The relationship between the meridional gradient of absolute vorticity and low-level zonal flow indicates that the sign of the absolute vorticity gradient tends to be reversed during the two phases,whereas the same sign between zonal flow and the absolute vorticity gradient is more easily satisfied in the active phases.Thus,the barotropic instability of low-level zonal flow might be an important mechanism for TC formation over the WNP during the active phases of ISO. 相似文献
860.
利用梵净山周边区域自动站逐小时降水资料和铜仁雷达观测资料,对2017—2018年铜仁市梵净山周边区域暴雨过程中逐小时分级降水的雷达类型和回波特征进行分析。结果表明:(1)梵净山区域暴雨过程中小雨、中雨、大雨年均总站次的日变化均呈双峰型分布,而暴雨年均总站次呈单锋型,并且具有明显的夜雨特征。(2)造成梵净山区域暴雨天气的雷达回波类型可分为本地发展型、移入型和合并加强型3种。(3)小时雨强与回波强度呈正相关,而与移动速度呈反相关。(4)径向速度图上中雨量级降水有弱辐合特征,大雨量级降水出现弱的逆风区结构,暴雨量级降水有明显的辐合辐散和速度对特征,且存在逆风区结构,逆风区位置对应强回波中心。(5)垂直累计液态水含量大值区及回波顶高度与反射率因子大值区有较好的对应。 相似文献