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141.
The mid-Pliocene, the most recent warm geological period, is thought to be indicative of the fate of the Earth's climate under global warming. Earlier evidence has suggested that permanent El Nio-like conditions existed in the mid-Pliocene, though the concept of a permanent El Nio remains controversial. Here, the authors analyzed Nio 3.4 SST in pre-industrial and mid-Pliocene simulations with the low-resolution version of the Norwegian Earth System Model (NorESM-L). The simulated mid-Pliocene Nio3.4 SST, with a smaller standard deviation, indicated that a weaker ENSO existed in the mid-Pliocene relative to the pre-industrial experiment. Compared with earlier modeling studies, our simulations show that the problem of ENSO's standard deviations in the mid-Pliocene remains unresolved, although the mean and the period of ENSO in the mid-Pliocene have been resolved by earlier geological and modeling studies. 相似文献
142.
Seasonality of the Lagged Relationship between ENSO and the Northern Hemispheric Polar Vortex Variability 总被引:2,自引:0,他引:2 下载免费PDF全文
REN Rong-Cai 《大气和海洋科学快报》2012,5(2):113-118
143.
BAO Qing 《大气和海洋科学快报》2012,5(1):43-48
Responses of the Asian Summer Monsoon(ASM) in future projections have been studied based on two core future projections of phase five of the Coupled Model Intercomparison Project(CMIP5) coordinated experiments with the IAP-coupled model FGOALS_s2(the Flexible Global Ocean-Atmosphere-Land System Model).The projected changes of the ASM in climatological mean and interannual variability were respectively reported.Both the South Asian Summer Monsoon(SASM) and the East Asian Summer Monsoon(EASM) were intensified in their climatology,featuring increased monsoon precipitation and an enhanced monsoon lower-level westerly jet flow.Accordingly,the amplitude of the annual cycle of rainfall over East Asia(EA) is enhanced,thereby indicating a more abrupt monsoon onset.After the EA monsoon onset,the EASM marched farther northward in the future scenarios than in the historical runs.In the interannual variability,the leading pattern of the EASM,defined by the first multi-variable EOF analysis over EA,explains more of the total variances in the warmest future scenario,specifically,Representative Concentration Pathway(RCP8.5).Also,the correlation coefficients analysis suggests that the relationship between the EASM interannual variations and ENSO was significantly strengthened in the future projections,which may indicate improved predictability of the EASM interannual variations. 相似文献
144.
K. P. Sooraj Daehyun Kim Jong-Seong Kug Sang-Wook Yeh Fei-Fei Jin In-Sik Kang 《Climate Dynamics》2009,33(4):495-507
Recently, there is increasing evidence on the interaction of atmospheric high-frequency (HF) variability with climatic low-frequency
(LF) variability. In this study, we examine this relationship of HF variability with large scale circulation using idealized
experiments with an aqua-planet Atmospheric GCM (with zonally uniform SST), run in different zonal momentum forcing scenarios.
The effect of large scale circulation changes to the HF variability is demonstrated here. The HF atmospheric variability is
enhanced over the westerly forced region, through easterly vertical shear. Our study also manifests that apart from the vertical
wind shear, strong low-level convergence and horizontal zonal wind shear are also important for enhancing the HF variance.
This is clearly seen in the eastern part of the forcing, where the HF activity shows relatively maximum increase, in spite
of similar vertical shear over the forced regions. The possible implications for multi-scale interaction (e.g. MJO–ENSO interaction)
are also discussed. 相似文献
145.
This study examines the PNA associated atmospheric diabatic heating by linearly isolating the influence of ENSO. The analysis
is based on the NCEP–NCAR and ERA-40 reanalyses and a 1,000-year-long integration of the CCCma coupled climate model. Both
the vertically integrated and three-dimensional diabatic heating are examined. The Rossby wave sources in association with
the PNA are also diagnosed. The PNA-related heating is confined outside the tropics and is dominated by anomalies in the eastern
Pacific, with a north–south dipole structure in mid-latitudes and the northern subtropics. The heating anomalies change sign
with height in mid-latitudes but have the same sign throughout the troposphere in the northern subtropics. Relatively weak
heating anomalies also appear in mid-latitudes, downstream of the heating dipole over North America and the western North
Atlantic. The heating anomalies are largely supported by the advections related to the mean state throughout the troposphere,
and partially damped by the advections related to the eddy effect, particularly at the upper troposphere over the North Pacific.
Broadly similar patterns are seen from the NCEP–NCAR and ERA-40 reanalyses. Yet anomalous heating centers are generally located
at relatively lower troposphere for the ERA-40 with respect to the NCEP–NCAR. The tropical heating anomalies are rather weak,
remarkably different from those related to ENSO variability. In addition, the Rossby wave source collocates with the atmospheric
diabatic forcing in the mid-high latitudes over the PNA sector, and shows no forcing source in the tropics. The results demonstrate
possible forcing in the mid-high latitudes, regardless of tropical heating for the PNA teleconnection. The modeled heating
and wave forcing anomalies in association with the modeled PNA compare reasonably well with the reanalysis-based estimates,
increasing confidence in the observational results. The analysis provides further evidence of the independence of the PNA
on ENSO from the diabatic heating point of view. 相似文献
146.
Ingo Heinrich Kathrin Weidner Gerhard Helle Heinz Vos Janette Lindesay John C. G. Banks 《Climate Dynamics》2009,33(1):63-73
Australian climate-proxy reconstructions based on tree rings from tropical and subtropical forests have not been achieved so far due to the rarity of species producing anatomically distinct annual growth rings. Our study identifies the Australian Red Cedar (Toona ciliata) as one of the most promising tree species for tree-ring research in Australasia because this species exhibits distinct annual tree rings, a prerequisite for high quality tropical dendroclimatology. Based on these preliminary studies, we were able, for the first time in subtropical and tropical Australia, to develop a statistically robust, precisely dated and annually resolved chronology back to AD1854. We show that the variability in ring widths of T. ciliata is mainly dependent on annual precipitation. The developed proxy data series contains both high- and low-frequency climate signals which can be associated with the El Niño Southern Oscillation (ENSO) and the Interdecadal Pacific Oscillation (IPO). A comparison of different data sets (Brisbane precipitation, tree rings, coral luminescence record from the Great Barrier Reef, ENSO and IPO) revealed non-stationary correlation patterns throughout the twentieth century but little instability between the new tree-ring chronology and Brisbane precipitation. 相似文献
147.
148.
石家庄春季自然物候对气候变化的响应研究 总被引:1,自引:0,他引:1
分析了石家庄1965-2007年杨絮始落、鸭梨始花和刺槐盛花3种植物物候期的变化特征以及对气候的响应规律。结果表明:(1)石家庄春季物候期普遍提早,早春的物候期提前天数多,晚春物候期提早天数少。石家庄春季物候现象普遍存在着2~3年的周期。(2)通过计算石家庄春季物候与气温、日照和降水量的相关关系,发现与气温的关系最好,与降水日数表现出弱的相关性,与日照关系不明显,说明气温是影响石家座春季物候的主导气象因子,GDD是衡量植物热量供应的较好指标,而日照对物候期影响表现出不同物种和不同物候现象间的差异性特征。(3)石家庄春季物候期与ENSO事件也表现出一定的关系,在暖事件年以物候期偏早为主,在冷事件年无明显早晚趋势。 相似文献
149.
150.
2015/2016年发生的极端El Ni?o事件,与1997/1998年El Ni?o事件具有可比拟的强度,但是2016年事件转变为弱La Ni?a,而1998年事件则为强La Ni?a。本文通过对比这两次极端El Ni?o事件,揭示其转变为不同强度La Ni?a事件的物理机制。混合层热收支分析的结果表明,在El Ni?o衰减年的4~11月,2016年平流反馈和温跃层反馈相对较弱,混合层温度衰减速率慢,其产生的主要原因是赤道中西太平洋的东风异常较弱。进一步分析表明,赤道中西太平洋的东风异常与副热带东北太平洋的海表温度异常(SSTA)有关,该地区的SST在1998年表现为冷异常,2016年为暖异常。副热带东北太平洋冷的SSTA有利于信风加强,从而加强中西太平洋的东风异常;而暖的SSTA使得赤道以北出现西南风异常,从而削弱中西太平洋的东风异常。此外,合成分析也表明,副热带东北太平洋SSTA与转变的La Ni?a的强度具有关联,El Ni?o转变为强La Ni?a的情况在位相转变期伴随着副热带北太平洋冷的SSTA,而El Ni?o转变为弱La Ni?a的情况没有明显的冷SSTA。 相似文献