全文获取类型
收费全文 | 945篇 |
免费 | 150篇 |
国内免费 | 418篇 |
专业分类
测绘学 | 44篇 |
大气科学 | 101篇 |
地球物理 | 87篇 |
地质学 | 677篇 |
海洋学 | 474篇 |
天文学 | 1篇 |
综合类 | 56篇 |
自然地理 | 73篇 |
出版年
2024年 | 5篇 |
2023年 | 23篇 |
2022年 | 34篇 |
2021年 | 44篇 |
2020年 | 40篇 |
2019年 | 48篇 |
2018年 | 40篇 |
2017年 | 56篇 |
2016年 | 46篇 |
2015年 | 44篇 |
2014年 | 66篇 |
2013年 | 81篇 |
2012年 | 45篇 |
2011年 | 50篇 |
2010年 | 62篇 |
2009年 | 57篇 |
2008年 | 63篇 |
2007年 | 60篇 |
2006年 | 63篇 |
2005年 | 60篇 |
2004年 | 72篇 |
2003年 | 64篇 |
2002年 | 53篇 |
2001年 | 37篇 |
2000年 | 37篇 |
1999年 | 49篇 |
1998年 | 45篇 |
1997年 | 37篇 |
1996年 | 30篇 |
1995年 | 16篇 |
1994年 | 26篇 |
1993年 | 18篇 |
1992年 | 17篇 |
1991年 | 5篇 |
1990年 | 1篇 |
1989年 | 10篇 |
1988年 | 4篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1985年 | 1篇 |
排序方式: 共有1513条查询结果,搜索用时 31 毫秒
991.
992.
993.
分析MW组合观测值的噪声特性,评价其实际周跳探测性能,提出利用EMD阈值消噪方法进行降噪。对于EMD的端点效应问题,在MW递推均值上增加虚拟噪声构成虚拟观测值对数据进行延拓。估计MW组合经EMD分解后各层分量的阈值,削弱噪声影响。分析消噪后含周跳MW组合所发生的变化,指出周跳具有"扩散"现象,提出基于消噪后MW组合的探测方案。 相似文献
994.
采用高分辨率的海表温度资料定义了春季黑潮延伸体北侧海洋锋区的南北位置,并采用EOF分析、相关分析、合成分析、带通滤波等方法,探讨了其南北向位置变动与高空急流、风暴轴以及后期东亚降水之间的关系。结果表明,春季黑潮延伸体北侧海洋锋区位置的南北变动存在明显的年际、年代际变化,其与6月东亚高空急流、太平洋区域风暴轴的南北位置具有很好的对应关系。当春季黑潮延伸体海洋锋区偏北时,6月东亚高空急流、太平洋区域风暴轴偏北,反之亦然。进一步的研究还表明,春季黑潮延伸体海洋锋区经向位置的变动可通过影响东亚大气环流对6月东亚地区的降水产生影响,黑潮延伸体海洋锋区偏北(南)年,6月雨带有显著的北(南)移。 相似文献
995.
Application of the Conditional Nonlinear Optimal Perturbation Method to the Predictability Study of the Kuroshio Large Meander 总被引:2,自引:0,他引:2
A reduced-gravity barotropic shallow-water model was used to simulate the Kuroshio path variations.The results show that the model was able to capture the essential features of these path variations.We used one simulation of the model as the reference state and investigated the effects of errors in model parameters on the prediction of the transition to the Kuroshio large meander (KLM) state using the conditional nonlinear optimal parameter perturbation (CNOP-P) method.Because of their relatively large uncertainties,three model parameters were considered:the interfacial friction coefficient,the wind-stress amplitude,and the lateral friction coefficient.We determined the CNOP-Ps optimized for each of these three parameters independently,and we optimized all three parameters simultaneously using the Spectral Projected Gradient 2 (SPG2) algorithm.Similarly,the impacts caused by errors in initial conditions were examined using the conditional nonlinear optimal initial perturbation (CNOP-I) method.Both the CNOP-I and CNOP-Ps can result in significant prediction errors of the KLM over a lead time of 240 days.But the prediction error caused by CNOP-I is greater than that caused by CNOP-P.The results of this study indicate not only that initial condition errors have greater effects on the prediction of the KLM than errors in model parameters but also that the latter cannot be ignored.Hence,to enhance the forecast skill of the KLM in this model,the initial conditions should first be improved,the model parameters should use the best possible estimates. 相似文献
996.
Chen-Tung Arthur Chen 《Journal of Oceanography》2008,64(5):737-751
Surface maps of nitrate, phosphate and silicate of the East China Sea (ECS) have been constructed and are described. Reports
on exchanges of material between the ECS and the South China Sea (SCS) through the Taiwan Strait are reviewed. Recent advances
seem to have reversed the earlier view that the SCS exports nutrients to the ECS through the Taiwan Strait. This is because
the northward flow of seawater in the summer carries little nutrient. On the other hand, the waters flowing southward along
the coast of China in winter carry orders of magnitude higher nutrient concentrations. The outflow of subsurface waters from
the SCS, however, is the major source of new nutrients to the ECS continental shelves because these subsurface waters flow
out of the Luzon Strait, join the northwardly flowing Kuroshio and enter the Okinawa trough. Around 10% of the nutrients exported
from the SCS through the Luzon Strait upwell onto the ECS shelf. These inputs are larger than the aggregate of all the rivers
that empty into the ECS, contributing 49% of the externally sourced nitrogen, 71% of the phosphorous, and 54% of the silica
for the ECS. 相似文献
997.
The Kuroshio near the Luzon Strait and circulation in the northern South China Sea during August and September 1994 总被引:3,自引:0,他引:3
Wind data from NCEP and hydrographic data obtained from August 28 to September 10, 1994 have been used to compute circulation
in the northern South China Sea and near Luzon Strait using three-dimensional diagnostic models with a modified inverse method.
The numerical results are as follows: the main Kuroshio is located above 400 m levels near Taiwan’s eastern coast and above
800 m levels away from it. Near Luzon Strait above 400 m levels a branch of the Kuroshio joins with a part of the northward
current, which comes from an area west of Luzon’s western coast and intrudes northwestward, then it branchs into western and
eastern parts near 20°30′ N. The eastern part flows northward into an area east of Taiwan, while its western part continues
to intrude northwestward, flowing through an area southwest of Taiwan. Net westward intruded volume transport through longitude
Section AB at 121°00′ E from 19°00′ N to 21° 43′ N is about 3.5 × 106 m3s−1 in a layer above 400 m levels. The anticyclonic eddies W1 and W3 exist above 700 m levels east of Dongsha Islands and below
200 m levels in the eastern part of the region, respectively. The circulation in the middle region is dominated mainly by
a basin-scale cyclonic gyre, and consists of three cyclonic eddies. Strong upwelling occurs in the middle region. The joint
effect of baroclinity and relief and interaction between wind stress and relief both are important for real forcing of flow
across contours of fH
−1 in effecting the circulation pattern. 相似文献
998.
基于2014年5—6月对黑潮主流径及毗邻东海陆架海区的调查,研究了该区域水体中无机碳体系参数(p H、总碱度TAlk、溶解无机碳DIC及DIC/TAlk)的垂直与水平分布,在此基础上定量评估了黑潮输入对东海陆架海区无机碳收支的影响。结果表明,黑潮水体中DIC、TAlk与DIC/TAlk总体而言随水深增加而升高,p H降低,综合体现了浮游植物生产、海-气界面交换、有机物降解及Ca CO3溶解等过程的影响;上升流中心站位无机碳参数均受较深层水体上涌影响,与黑潮主流径其它站位略有不同。东海陆架海区外侧站位表层、30m层无机碳主要受台湾海峡暖流影响,高p H、低DIC/TAlk的黑潮表层水影响区域局限于东南部;而在底层,低p H、高DIC/TAlk的黑潮入侵流离开黑潮主流径向正北方延伸并抬升至钱塘江口附近;上升流对无机碳的影响持续至表层,其携带的黑潮中层水因此也可能进入陆架海区。水量模型估算黑潮水在5—10月间跨域陆架边缘向东海陆架区输入溶解无机碳总计58798.9×109mol,净输入达37382.9×109mol,而东海向外输出的无机碳绝大部分经由对马海峡进入日本海。 相似文献
999.
冬季黑潮延伸体海表温度变率的年代际变化及其与阿留申大气低压系统的关系 总被引:2,自引:1,他引:1
By utilizing multiple datasets from various sources available for the last 100 years, the existence for the interdecadal change of the winter sea surface temperature(SST) variability in the Kuroshio Extension(KE) region is investigated. And its linkage with the Aleutian Low(AL) activity changes is also discussed. The results find that the KE SST variability exhibits the significant ~6 a and ~10 a oscillations with obvious interdecadal change. The ~6 a oscillation is mainly detected during 1930–1950, which is largely impacted by the anomalous surface heat flux forcing and Ekman heat transport associated with the AL intensity variation. The ~10 a oscillation is most evident after the 1980s, which is predominantly triggered by the AL north-south shift through the bridge of oceanic Rossby waves. 相似文献
1000.
黑潮延伸体海表温度锋位置的变化特征 总被引:2,自引:1,他引:1
High spatial resolution sea surface temperature(SST) data from 1993 to 2013 are used to detect the position of the Kuroshio Extension sea surface temperature front(KEF) from 141°E to 158°E,and the seasonal,monthly and interannual-to-decadal variations of the KEF position are investigated.The latitudinal position of the KEF varies with longitudes:the westernmost part of the KEF from 141°E to 144°E is relatively stable,whereas the easternmost part from 153°E to 158°E exhibits the largest amplitude of its north-south displacement.In the light of the magnitudes of the standard deviations at longitudes,then the KEF is divided into three sections:western part of the KEF(KEFw,141°–144°E),central part of the KEF(KEFc,144°–153°E) and eastern part of the KEF(KEFe,153°–158°E).Further analysis reveals that the KEFw position is dominated by the decadal variability,while the KEFc and KEFe positions change significantly both on interannual and decadal time scales.In addition,the KEFw position is well correlated with the KEF path length.The possible mode leading to the decadal oscillation of the KEFw is further discussed.The KEFw position exhibits significant connections with the Pacific decadal oscillation(PDO) index and the north Pacific gyre oscillation(NPGO) index with a time lag of 40 and 33 months,respectively. 相似文献