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991.
中国东部夏季降水型的年代际变化及其与北太平洋海温的关系 总被引:28,自引:12,他引:16
采用中国160站降水资料、NOAA ERSST海温资料以及ERA-40大气再分析资料, 分析了中国东部夏季降水型的年代际变化特征及其与北太平洋海温的可能联系。结果表明: 中国东部夏季降水型在近50年中经历了两次年代际变化, 第1次发生在20世纪70年代中后期, 北太平洋中纬度地区冬季海温由正距平向负距平转变, 太平洋年代际振荡(PDO, Pacific decadal oscillation) 由负位相向正位相转变, 通过影响东亚夏季风环流, 使东亚夏季风减弱, 中国东部夏季降水从北到南呈现出“+-+” 转变为“-+-”的三极分布形态, 这次年代际变化体现了同一模态正负位相的转变; 第2次发生在20世纪80年代末90年代初, 北太平洋海温转变为日本以南西北太平洋的正距平分布, 同时菲律宾群岛附近海温偏暖, 西太平洋副热带高压偏南偏西, 使得中国东部夏季降水由北至南转变成“-+”的偶极分布形态, 这次年代际变化体现了一种模态向另一种模态的转变。 相似文献
992.
重庆市气温变化趋势及其可能原因分析 总被引:3,自引:1,他引:2
通过对重庆市1924~2007年的平均气温、平均最高气温、平均最低气温、极端最高气温、极端最低气温随时间变化特征进行分析发现:近84年来重庆市平均气温微弱变冷,与全国平均温度相比线性变化趋势存在一定差异;平均最高和平均最低气温、极端最高和极端最低气温的非对称性变化显著,最高气温的下降对平均气温的影响很大,平均最低气温除春季外增暖都非常显著,最低温度的增高对气温日较差减小的影响更明显.夏季副热带高压位置偏南,使得我国西南地区东部夏季降水天气增多、云量增加、日照时数减少,加之轻雾日数增多,可能是重庆市夏季最高温度持续下降的主要原因.冬季最低气温的显著升高主要是由于降水天气减少、云量增加和城市热岛效应所致. 相似文献
993.
应用一个嵌套了海洋生物地球化学循环的太平洋环流碳循环模式,分析了1960~2000年太平洋不同海区海气碳通量随时间的变化。模拟结果显示,赤道太平洋为大气CO2的排放区,南、北太平洋(南、北纬15°至模式计算区域南、北边界)为吸收区。3个海区海气碳通量随时间均存在显著的波动,其中赤道太平洋海气碳通量年际波动最显著。3个海区海气碳通量年际波动对气候事件的响应并不一致,在El Niño年赤道太平洋冷舌的强度和总溶解无机碳(DIC)的浓度以及输出生产力均会受到上升流减弱的影响而降低,La Niña年这些海气碳通量控制要素的分布情况则正好相反,但在南北太平洋副热带以及高纬度海区,El Niño和La Niña对这些要素带来的影响却并不一定相反,对输出生产力的影响甚至是一致的。以海表温度(SST)为例考察海气碳通量与物理场之间的关系表明,在赤道太平洋上升流对DIC的影响是控制海气碳通量变化的主要因素,而在其他海区,尤其是副热带海区,由于垂直运动的年际变化较小,且生物生产力水平较低,SST的波动对海气碳通量年际变化的影响更加重要。 相似文献
994.
A 50-year record of the Indonesian throughflow (ITF) was obtained using the Simple Ocean Data Assimilation (SODA) dataset to calculate a timeseries of Pacific-to-Indian Ocean pressure differences, which were calibrated to transport profiles using ARLINDO (1997) and INSTANT (2004–2006) observational data. The 50 year SODA based ITF transport average is 10.4 Sv; the transport weighted temperature (TWT) is 14.6 °C and the internal energy transport (IET) is 0.53 PW. The different configurations of the ITF transport and temperature profiles result in a dissimilarity in the variability of the IET and the TWT, with the IET more closely correlated with both the depth of the 18 °C isotherm in the western equatorial Pacific and the NINO3.4 index. As with the transport, the IET increases during La Niña and decreases during El Niño. The TWT is only weakly correlated with NINO3.4, suggesting that the El Niño-Southern Oscillation signal is transmitted from the Pacific to the Indian Ocean via changes in pressure and thus in transport rather than by changes in temperature. 相似文献
995.
In this study, sensitivity experiments were conducted with the Zebiak-Cane ocean-atmosphere coupled model forced by the wind stress anomaly from the U.S. National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis data to study the impacts of eastern Pacific warm pool on the formation and development of ENSO events. The effects of climatological mean sea surface temperature of the warm pool on forecast skill during the ENSO events of 1982–1999 are more considerable that those of climatological mean meridional winds and ocean currents. The forecast skill for the 1997/1998 El Ni?o event is characterized by sensitivity to climatological mean sea surface temperature and anomalies of northerly winds and currents. The forecast skill is found insensitive to climatological mean northerly meridional winds and currents. 相似文献
996.
1950—2009年夏季菲律宾低空越赤道气流的变化特征 总被引:2,自引:1,他引:1
利用1950—2009年NECP/NCAR的月平均经向风再分析资料,根据夏季(6—8月)菲律宾低空越赤道气流的特征,定义了该支气流的强度指数IS和位置偏移指数IL,并根据这两个指数分析了菲律宾越赤道气流的时间变化特征及对应的环流特征,以及其与亚洲夏季降水的关系。结果表明,IS主要呈现弱、强、弱、强的年代际变化特征,IL主要呈现振荡、稳定、径直转向的年代际变化特征。IS与由低层澳大利亚高压北侧冷空气活跃和西太平洋副热带高压减弱所造成的经向气压梯度的变化有关,IL与澳大利亚地区和赤道低槽区高、低层的南北气压梯度有关。IS与印度尼西亚、孟加拉湾南部、热带西太平洋和澳大利亚东部的降水关系密切,IL与孟加拉湾和中国南海南部的降水关系密切。此外,IL与澳大利亚上空的垂直运动具有密切联系。 相似文献
997.
998.
The East Asia-western North Pacific boreal summer intraseasonal oscillation simulated in GAMIL 1.1.1 总被引:1,自引:0,他引:1
We evaluate the performance of GAMIL1.1.1 in a 27-year forced simulation of the summer
intraseasonal oscillation (ISO) over East Asia (EA)-western North Pacific (WNP). The assessment
is based on two measures: climatological ISO (CISO) and transient ISO (TISO). CISO is the ISO
component that is phase-locked to the annual cycle and describes seasonal march. TISO is the
ISO component that varies year by year.
The model reasonably captures many observed features of the ISO, including the stepwise northward
advance of the rain belt of CISO, the dominant periodicities of TISO in both the South China
Sea-Philippine Sea (SCS-PS) and the Yangtze River Basin (YRB), the northward propagation of 30--50-day
TISO and the westward propagation of the 12--25-day TISO mode over the SCS-PS, and the zonal propagating
features of three major TISO modes over the YRB. However, the model has notable deficiencies. These
include the early onset of the South China Sea monsoon associated with CISO, too fast northward
propagation of CISO from 20oN to 40oN and the absence of the CISO signal south of 10oN,
the deficient eastward propagation of the 30--50-day TISO mode and the absence of a southward propagation
in the YRB TISO modes.
The authors found that the deficiencies in the ISO simulation are closely related to the model's biases in
the mean states, suggesting that the improvement of the model mean state is crucial for realistic
simulation of the intraseasonal variation. 相似文献
999.
Contribution of the sea surface temperature over the Mediterranean-Black Sea to the decadal shift of the summer North Atlantic Oscillation 总被引:2,自引:0,他引:2
Recent observational study has shown that the southern center of the summer North Atlantic
Oscillation (SNAO) was located farther eastward after the late 1970s compared to before. In this study,
the cause for this phenomenon is explored. The result shows that the eastward shift of the SNAO southern
center after the late 1970s is related to the variability of the Mediterranean-Black Sea (MBS) SST. A
warm MBS SST can heat and moisten its overlying atmosphere, consequently producing a negative sea level
pressure (SLP) departure over the MBS region. Because the MBS SST is negatively correlated with the SNAO,
the negative SLP departure can enhance the eastern part of the negative-phase of the SNAO southern center,
consequently producing an eastward SNAO southern center shift. Similarly, a cold MBS SST produces an eastward
positive-phase SNAO southern center shift.
The reason for why the MBS SST has an impact on the SNAO after the late 1970s but why it is not the case
beforehand is also discussed. It is found that this instable relationship is likely to be attributed to
the change of the variability of the MBS SST on the decadal time-scale. In 1951--1975, the variability of
the MBS SST is quite weak, but in 1978--2002, it becomes more active. The active SST can enhance the
interaction between the sea and its overlying atmosphere, thus strengthening the connection between the
MBS SST and the SNAO after the late 1970s. The above observational analysis results are further confirmed
by sensitivity experiments. 相似文献
1000.
ENSO’s effect on the rainfall in eastern China in the following early summer is investigated by using station precipitation data and the ERA-40 reanalysis data from 1958 to 2002. In June, after the El Nino peak, the precipitation is significantly enhanced in the Yangtze River valley while suppressed in the Huaihe River-Yellow River valleys. This relationship between ENSO and the rainfall in eastern China is established possibly through two teleconnections: One is related to the western North Pacific (WNP) ... 相似文献