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81.
ENSO对全球及中国农业气象灾害和粮食产量影响研究进展   总被引:3,自引:0,他引:3  
厄尔尼诺-南方涛动(ENSO)是全球性年际气候变率的主导模式,ENSO通过影响全球的大气环流,对全球许多地区的气温、降水和由气温、降水异常导致的农业气象灾害(如低温冷害、旱涝灾害等)及农作物生长发育、产量形成产生影响。综述前人对ENSO影响研究进展,所得主要结论如下:1)从全球范围来看,厄尔尼诺年,全球气温偏高,陆地平均年降水量减少;拉尼娜年,全球气温偏低,陆地平均年降水量增加;不同季节和不同类型EN-S0对全球气温和降水的影响有差异。在中国,厄尔尼诺年,大部分地区冬春季气温偏高,夏秋季气温偏低,拉尼娜年,大部分地区冬春季气温偏低,夏秋季气温偏高,不同年代下ENSO对我国气温的影响有所变化;厄尔尼诺年,全国降水以偏少为主,且ENSO对我国不同地区降水的影响与ENSO类型、发展阶段和发生年代有关。2)厄尔尼诺年,我国北方大部分地区初霜冻偏早,吉林延迟型冷害增加,黑龙江低温冷害多发,华北和西北地区易发生干旱;拉尼娜年,我国北方大部分地区初霜冻偏晚,西北地区易发生洪涝。气候变暖背景下,厄尔尼诺与东北低温的关系更为复杂。ENSO循环的不同阶段会影响我国旱涝的地区分布。3)厄尔尼诺年和拉尼娜年,全球水稻、小麦和玉米均以减产为主,不同国家和地区影响各异。其中,厄尔尼诺年,美国、巴西和阿根廷玉米产量增加,中国和津巴布韦玉米产量降低,印度小麦和水稻及菲律宾、印度尼西亚的雨季水稻均减产;拉尼娜年,美国、巴西和阿根廷玉米减产,印度小麦和水稻增产。在中国,厄尔尼诺对水稻和小麦产量的影响程度与当地灌溉条件有关。以上结论可为我国防御低温冷害、干旱等农业气象灾害,保障粮食安全,制定科学政策提供理论参考。  相似文献   
82.
伴随方法在海洋数值模式中的应用   总被引:7,自引:0,他引:7  
本文通过对变分资料同化方法在气象学和海洋学方面特别是在海洋数值模式中应用的简单回顾,评价了伴随方法在方法论上的优越性,首先引入包含海洋数值模式控制方程组的拉格朗日乘子,说明变分资料同化的数学原理;介绍伴随方法应用中目标函数的构造方法,简单说明了伴随方法中伴随方程的导出和伴随方法实际应用的步骤,最后就近几年国外研究进展做了简单概括。  相似文献   
83.
Prior studies have revealed that,as a part of the Pacific tropical gyre,the South China Sea throughflow(SCSTF) is strongly influenced by the Pacific low-latitude western boundary current(LLWBC).In this study,ocean general circulation model(OGCM) experiments with and without connection to the South China Sea(SCS) were performed to investigate the impact of the SCSTF on the Pacific LLWBC.These model experiments show that if the SCS is blocked,seasonal variability of the Kuroshio and Mindanao Current becomes stronger,and the meridional migration of the North Equatorial Current(NEC) bifurcation latitude is enhanced.Both in seasonal and interannual time scales,stronger Luzon Strait transport(LST) induces a stronger Kuroshio transport combined with a southward shift of the NEC bifurcation,which is unfavorable for a further increase of the LST;a weaker LST induces a weaker Kuroshio transport and a northward shifting NEC bifurcation,which is also unfavorable for the continuous decrease of the LST.  相似文献   
84.
南海潜热交换年际与年代际变化的分析探讨   总被引:1,自引:0,他引:1  
根据一套客观分析潜热通量、基于绕岛理论诊断的南海贯穿流(LST)、南海热含量等月平均资料,分析南海表层潜热通量的年际和年代际变化特征。南海地区的潜热通量冬季强,春季的潜热通量弱;在秋冬季节,南海北部的潜热通量远大于南部;夏季南海潜热通量南部高于北部;从20世纪80年代初潜热通量逐渐增加。使用EOF经验正交分解,M-K检验方法分析南海潜热通量的多时间尺度变化,前3个模态的方差贡献率分别为:53.01%(主要为长期趋势)、17.4%(年代际变化)、6.71%(年际变化)。分析表明在年际尺度上南海贯穿流(LST)减少导致南海海表温度(SST)增温幅度上升,海气温差比湿差减小,从而导致潜热释放减少,潜热通量呈负异常;反之LST进入南海增多,海气温差比湿差变大,导致南海潜热损失减少,潜热通量呈正异常。  相似文献   
85.
86.
Tropical cyclone (TC) genesis in the South China Sea (SCS) during 1979-2008 underwent a decadal variation around 1993. A total of 55 TCs formed in the SCS from May to September during 1994- 2008, about twice that during 1979-1993 (27). During the TC peak season (July-September, JAS), there were 43TCs from 1994-2008, but only 17 during 1979-1993. For July in particular, 13TCs formed from 1994-2008, but there were none during 1979-1993. The change in TC number is associated with changes of key environmental conditions in atmosphere and ocean. Compared to 1979-1993, the subtropical high was significantly weaker and was displaced more eastward during 1994-2008. In the former period, a stronger subtropical high induced downward flow, inhibiting TC formation. In the latter period, vertical wind shear and outgoing longwave radiation all weakened. Mid-level (850-500hPa) humidity, and relative vorticity were higher. Sea surface temperature and upper layer heat content were also higher in the area. All these factors favor TC genesis during the latter period. The decadal change of TC genesis led to more landfalling TCs in Southern China during the period 1994-2008, which contributed to an abrupt increase in regional rainfall.  相似文献   
87.
The fifth Pennsylvania State University and National Center for Atmospheric Research mesoscale model (MM5) is utilized to study the precipitation and wind speed during Typhoon Chanchu (2006).Five model experiments with different physical parameterizations and sea surface temperature (SST) distributions are carried out.It is found that the control experiment configured with the Blakadar boundary scheme,Resiner2 moisture,the Betts-Miller cumulus scheme and daily updated SST has the most reasonable precipitation.The MRF boundary scheme tends to simulate a dryer boundary layer and stronger vertical mixing,which can greatly reduce the intensity of tropical cyclone (TC),resulting in a smaller maximum wind speed but larger range of medium wind speed (25-30 m/s).Constant SST through the TC cycle provides more energy from ocean surface,which could cause a significant increase in TC’s intensity,thus resulting in the largest overestimation on rainfall and maximum wind speed.Longitudinally-uniform SST distribution before the rapid intensification could reduce TC’s intensity and heat fluxes,which can partially compensate for the overestimation of precipitation in the control experiment.  相似文献   
88.
The Princeton Ocean Model (POM) with generalized coordinate system (POMgcs) is used to study the summer surface-layer thermal response to surface gravity waves in the Yellow Sea (YS). The parameterization schemes of wave breaking developed by Mellor and Blumberg (J Phys Oceanogr 34:693–698, 2004) and Kantha and Clayson (Ocean Model 6:101–124, 2004), respectively, and Stokes production developed by Kantha and Clayson (Ocean Model 6:101–124, 2004) are both included in the Mellor–Yamada turbulence closure model Mellor and Yamada (Rev Geophys 20:851–875, 1982) of POMgcs. Numerical results show that surface gravity waves impact the depth of surface mixed layer of temperature in the YS in summer. The surface mixed layer in the YS cannot be reproduced well and has a visible difference from the observation if the parameterization schemes are not included. A diagnostic analysis of turbulent kinetic energy suggests that both Stokes production and wave breaking play key roles in enhancing the turbulent mixing near the sea surface in the YS. Stokes production seems to have a greater impact throughout the upper mixed layer in the YS in summer than that of wave breaking. In addition, a diagnostic analysis of the momentum balance shows that Coriolis–Stokes forcing has a significant effect on the momentum budget in the upper layer in the YS, and surface gravity waves are able to reduce the velocity of mean flow near the surface and make the mean flow near the surface more homogeneous vertically in the YS.  相似文献   
89.
Barrier layer in the South China Sea during summer 2000   总被引:2,自引:0,他引:2  
Using temperature–salinity profiles obtained from a cruise in summer 2000, the structure and formation of the barrier layer (BL) in the South China Sea (SCS) are investigated. Fresh water flux, ocean circulation, and wind stirring are important for BL formation, depending on regions. In the eastern SCS, Philippine mountains induce heavy rainfall, resulting in a fresh water cap at the surface and the formation of a thick wide spread BL. In the northwestern basin on the lee of the Annam Cordillera range, by contrast, a rain shadow reduces fresh water flux, which along with wind-induced upwelling, prevents the BL forming. Southeast of Vietnam, a thick BL forms as the Mekong River plume is advected by the northeastward western boundary current and its offshore extension. In the southeastern basin, the surface water is mixed deeply under the strong southwesterly monsoon, unfavorable for the BL formation despite heavy rainfall. In the Luzon Strait, the east/southeastward surface Ekman drift carries fresh SCS surface water, riding on the intruding Kuroshio meander that carries well-mixed, warm and saline water. The vertical overlapping of these two water masses gives rise to a thick BL.  相似文献   
90.
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