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241.
Features of the Extremely Severe Drought in the East of Southwest China and Anomalies of Atmospheric Circulation in Summer 2006 总被引:1,自引:0,他引:1 下载免费PDF全文
The spatial-temporal features of the extremely severe drought and the anomalous atmospheric circulation in summer 2006 are
analyzed based on the NCEP/NCAR reanalysis data, the characteristic circulation indices given by the National Climate Center
of China, and the daily precipitation data of 20 stations in the east of Southwest China (ESC) from 1959 to 2006. The results
show that the rainless period started from early June and ended in early September 2006 with a total of more than 80 days,
and the rainfall was especially scarce from around 25 July to 5 September 2006. Precipitation for each month was less than
normal, and analysis of the precipitation indices shows that the summer precipitation in 2006 was the least since 1959. The
extremely severe drought in the ESC in summer 2006 was closely related to the persistent anomalies of the atmospheric circulation
in the same period, i.e., anomalies of mid-high latitude atmospheric circulation, western Pacific subtropical high (WPSH),
westerlies, South Asian high, lower-level flow, water vapor transport, vertical motion, and so on. Droughts usually occur
when the WPSH lies anomalously northward and westward, or anomalously weak and eastward. The extreme drought in summer 2006
was caused by the former. When the WPSH turned stronger and shifted to the north and west of its normal position, and the
South Asian high was also strong and lay eastward, downdrafts prevailed over the ESC and suppressed the water vapor transfer
toward this area. At the same time, the disposition of the westerlies and the mid-high latitude circulation disfavored the
southward invasion of cold air, which jointly resulted in the extremely severe drought in the ESC in summer 2006. The weak
heating over the Tibetan Plateau and vigorous convective activities over the Philippine area were likely responsible for the
strong WPSH and its northwestward shift in summer 2006. 相似文献
242.
243.
Light-induced bird strikes are known to occur when vessels navigate during darkness in icy waters using powerful searchlight. In Southwest Greenland, which is important internationally for wintering seabirds, we collected reports of incidents of bird strikes over 2-3 winters (2006-2009) from navy vessels, cargo vessels and trawlers (total n = 19). Forty-one incidents were reported: mainly close to land (<4 km, 78%), but one as far offshore as 205 km. Up to 88 birds were reported killed in a single incident. All occurred between 5 p.m. and 6 a.m. and significantly more birds were involved when visibility was poor (snow) rather than moderate or good. Among five seabird species reported, the common eider (Somateria mollissima) accounted for 95% of the bird casualties. Based on spatial analyses of data on vessel traffic intensity and common eider density we are able to predict areas with high risk of bird strikes in Southwest Greenland. 相似文献
244.
川滇及其邻区中强地震烈度衰减关系适用性研究 总被引:6,自引:0,他引:6
本文选取川滇及邻区作为研究区域,根据地震构造环境和震害分布特点,将该地区分为西南地区和盆地地区,选取该地区6级以上的典型历史震例,将其数字化得到等震线数据,通过对这些数据的统计回归分析,分别建立两个区域的地震烈度沿长轴与短轴的衰减关系、各烈度面积与地震震级的关系、破裂长度与震级的关系.同时,综合利用上述关系建立不同的地... 相似文献
245.
246.
A Method of Initial Vortex Relocation and Numerical Simulation Experiments on Tropical Cyclone Track 总被引:3,自引:2,他引:1
Using the technique of smooth filtering and cylindrical filtering, the initial vortex circulation and large-scale environmental field were separated from the background field. Then the separated initial vortex circulation was translated and reinserted in the location where it was observed. This led to the determination of a method of initial vortex relocation. For seven tropical cyclones at 23 points of measurement time in the years of 2006 and 2007, two schemes, either directly adding a tropical cyclone bogus model in the background or adding it after the relocation of the initial vortex in the background field, were employed. Simulation experiments were compared. The results showed that the mean errors of the simulated tropical cyclone tracks at 24 and 48 hours were both smaller with the scheme of adding tropical cyclone bogus model after the relocation of the initial vortex in the background field. The relocation method of the initial vortex decreases the error caused by the deviation of the initial tropical cyclone location in tropical cyclone models. The relocation method is conducive to improving the track forecast of tropical cyclone models and has a good perspective for operational application. 相似文献
247.
利用常规气象资料和NCEP 1°×1°再分析资料,结合自动站加密资料对2009年9月29日20:00至10月1日20:00发生在浙江东部沿海的一次东风波暴雨过程进行了分析.结果发现:0916号台风"凯萨娜"外围环流为此次东风波的形成提供了扰动作用,副热带高压的加强使得低层形成了明显的东南急流,为暴雨或强降水的发生提供了... 相似文献
248.
The Possible Mechanism of a Type of Vortex Heavy Rainfall during the Pre-Rainy Season in South China 总被引:2,自引:0,他引:2 下载免费PDF全文
In this paper,NCEP reanalysis data,intensive observation data collected from field experiment,model simulation data,and topographic trial data are fully analyzed to study a severe heavy rainfall event during 5 6 June 2008 in South China.Unlike most warm region rainfall cases,this one is associated with an obvious vortex system,which draws in water vapor and energy from the southwest monsoon surges ahead of a low trough above the Bengal Bay (BLT,Bengal Low Trough).At the lower troposphere,three currents,especially the southwest current and the east current,converge into the southeast of the vortex.Thus,the distributions of strong vorticity,water vapor,and ascending motion cause frequently occurrence and growth of convection there.The possible reasons for this rainfall event are summarized as a conceptual model. 相似文献
249.
Sedimentological analyses of 289 years (AD 1718-2006) of varved sediment from Shadow Bay, southwest Alaska, were used to investigate hydroclimate variability during and prior to the instrumental period. Varve thicknesses relate most strongly to total annual discharge (r2 = 0.75, n = 43, p < 0.0001). Maximum annual grain size depends most strongly on maximum spring daily discharge (r2 = 0.63, n = 43, p < 0.0001) and maximum annual daily discharge (r2 = 0.61, n = 43, p < 0.0001), while varve thickness is poorly correlated with maximum annual grain size (r2 = 0.004, n = 287, p = 0.33). Relations between varve thickness and annual climate variables (temperature, precipitation, North Pacific (NP) and Pacific Decadal Oscillation (PDO) indices) are insignificant. On multidecadal timescales, however, regime shifts in varve thickness and total annual discharge coincide with shifts in NP and PDO indices. Periods with increased varve thickness and total annual discharge were associated with warm PDO phases and a strengthened Aleutian Low. The varve-inferred record of PDO suggests that any periodicity in the PDO varied over time, and that the early 19th century marked a transition to a more frequent or detectable shifts. 相似文献
250.