全文获取类型
收费全文 | 1430篇 |
免费 | 372篇 |
国内免费 | 693篇 |
专业分类
测绘学 | 29篇 |
大气科学 | 747篇 |
地球物理 | 442篇 |
地质学 | 556篇 |
海洋学 | 494篇 |
天文学 | 20篇 |
综合类 | 93篇 |
自然地理 | 114篇 |
出版年
2024年 | 10篇 |
2023年 | 27篇 |
2022年 | 65篇 |
2021年 | 83篇 |
2020年 | 92篇 |
2019年 | 78篇 |
2018年 | 64篇 |
2017年 | 70篇 |
2016年 | 83篇 |
2015年 | 85篇 |
2014年 | 121篇 |
2013年 | 138篇 |
2012年 | 91篇 |
2011年 | 112篇 |
2010年 | 108篇 |
2009年 | 103篇 |
2008年 | 121篇 |
2007年 | 118篇 |
2006年 | 126篇 |
2005年 | 112篇 |
2004年 | 95篇 |
2003年 | 63篇 |
2002年 | 56篇 |
2001年 | 63篇 |
2000年 | 59篇 |
1999年 | 49篇 |
1998年 | 72篇 |
1997年 | 45篇 |
1996年 | 34篇 |
1995年 | 28篇 |
1994年 | 31篇 |
1993年 | 26篇 |
1992年 | 13篇 |
1991年 | 15篇 |
1990年 | 5篇 |
1989年 | 13篇 |
1988年 | 3篇 |
1987年 | 6篇 |
1986年 | 4篇 |
1985年 | 3篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1978年 | 2篇 |
排序方式: 共有2495条查询结果,搜索用时 15 毫秒
11.
夏季南海上层环流动力机制的数值研究 总被引:10,自引:0,他引:10
通过利用一个分区性的正压-斜压衔接模式来探讨夏季南海的上层环流特征及其动力机制,结果表明:夏季期间,由于风生环流的不稳定性促使在东沙群岛附近的气旋涡的强度及位置发生变化,并间接导致黑潮侵入南海北部的程度变化以及气旋涡南侧的反气旋式环流、西沙群岛西南侧的气旋涡的强度和范围出现波动现象;在南海南部的北向西边界流由于离岸的西南季风所驱动在中南半岛中部沿岸脱离岸线往东北方向的流动,导致沿岸的水体大量流失而在沿岸形成一支南向补偿流并在西沙群岛西南侧诱生一气旋涡,而上述的离岸西边界流则作顺时针方向流动,从而在南海南部形成反气旋式大环流;在南沙海槽附近出现的局地气旋涡和万安滩附近的气旋涡分别受β效应、底形效应的作用而形成. 相似文献
12.
13.
宋丽娜 《中国海洋大学学报(自然科学版)》1987,(2)
本文将流速分解模型应用于作为超浅海风暴潮的渤海风潮,并讨论了变湍粘性系数的确定。作为一个初步的,但较为成功的数值试验例子,描述了实际风场作用下的渤海风潮,比较了变湍粘性系数模型与常湍粘性系数模型的计算结果间的差异。 相似文献
14.
Amodeloftheformationanddevelopmentofoceanshearwave¥QiaoFangliandZhangQinghua(FirstInstituteofOceanography,stateoceanicAdminis... 相似文献
15.
Radiocarbon and total carbonate data were obtained near the 1973 GEOSECS stations in the North Pacific along 30°N and along 175°E between 1993 and 1994. In these stations, we estimated radiocarbon originating from atomic bomb tests using tritium, trichlorofluoromethane and silicate contents. The average penetration depth of bomb radiocarbon during the two decades has deepened from 900 m to 1300 m. Bomb radiocarbon inventories above the average value for the whole North Pacific were found widely in the western subtropical region around 30°N both in the 1970s and 1990s, and its area in the 1990s was broader than that in the 1970s. In most of the North Pacific, while the bomb radiocarbon has decreased above 25.4, the bomb radiocarbon flux below 25.4 was over 1 × 1012 atom m-2yr-1 in the subtropical region around 30°N. In the tropical area south of 20°N, the bomb radiocarbon inventory below 25.4 increased from zero to over 10 × 1012 atom m-2 during the last three decades. These distributions suggest that the bomb radiocarbon removed from the surface is currently accumulated with bomb 14C flux of over 1 × 1012 atom m-2yr-1 below 25.4 in the subtropical region, mainly by advection from the higher latitude, and that part of the accumulated bomb 14C gradually spread southward with about 30 years. 相似文献
16.
The influences of mesoscale eddies on variations of the Kuroshio path south of Japan have been investigated using time series
of the Kuroshio axis location and altimeter-derived sea surface height maps for a period of seven years from 1993 to 1999,
when the Kuroshio followed its non-large meander path. It was found that both the cyclonic and anticyclonic eddies may interact
with the Kuroshio and trigger short-term meanders of the Kuroshio path, although not all eddies that approached or collided
with the Kuroshio formed meanders. An anticyclonic eddy that revolves clockwise in a region south of Shikoku and Cape Shionomisaki
with a period of about 5–6 months was found to propagate westward along about 30°N and collide with the Kuroshio in the east
of Kyushu or south of Shikoku. This collision sometimes triggers meanders which propagate over the whole region south of Japan.
The eddy was advected downstream, generating a meander on the downstream side to the east of Cape Shionomisaki. After the
eddy passed Cape Shionomisaki, it detached from the Kuroshio and started to move westward again. Sometimes the eddy merges
with other anticyclonic eddies traveling from the east. Coalescence of cyclonic eddies, which are also generated in the Kuroshio
Extension region and propagate westward in the Kuroshio recirculation region south of Japan, into the Kuroshio in the east
of Kyushu, also triggers meanders which mainly propagate only in a region west of Cape Shionomisaki.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
17.
Breaking wave induced nearsurface turbulence has important consequences for many physical and biochemical processes including water column and nutrients mixing,heat and gases exchange across air-sea interface.The energy loss from wave breaking and the bubble plume penetration depth are estimated.As a consequence,the vertical distribution of the turbulent kinetic energy(TKE),the TKE dissipation rate and the eddy viscosity induced by wave breaking are also provided.It is indicated that model results are found to be consistent with the observational evidence that most TKE generated by wave breaking is lost within a depth of a few meters near the sea surface.High turbulence level with intensities of eddy viscosity induced by breaking is nearly four orders larger than υwl(=κuwz),the value predicted for the wall layer scaling close to the surface,where uw is the friction velocity in water,κ with 0.4 is the von Kármán constant,and z is the water depth,and the strength of the eddy viscosity depends both on wind speed and sea state,and decays rapidly through the depth.This leads to the conclusion that the breaking wave induced vertical mixing is mainly limited to the near surface layer,well above the classical values expected from the similarity theory.Deeper down,however,the effects of wave breaking on the vertical mixing become less important. 相似文献
18.
Patrick F. Cummins Gary S.E. Lagerloef 《Deep Sea Research Part I: Oceanographic Research Papers》2004,51(12):365
Interannual variability of the sea surface height (SSH) over the northeast Pacific Ocean is hindcast with a reduced-gravity, quasi-geostrophic model that includes linear damping. The model is forced with monthly Ekman pumping fields derived from the NCEP reanalysis wind stresses. The numerical solution is compared with SSH observations derived from satellite altimeter data and gridded at a lateral resolution of 1 degree. Provided that the reduced gravity parameter is chosen appropriately, the results demonstrate that the model has significant hindcast skill over interior regions of the basin, away from continental boundaries. A damping time scale of 2 to 3 years is close to optimal, although the hindcast skill is not strongly dependent on this parameter.A simplification of the quasi-geostrophic model is considered in which Rossby waves are eliminated, yielding a Markov model driven by local Ekman pumping. The results approximately reproduce the hindcast skill of the more complete quasi-geostrophic model and indicate that the interannual SSH variability is dominated by the local response to wind forcing. There is a close correspondence the two leading empirical orthogonal modes of the local model and those of the observed SSH anomalies. The latter account for over half of the variance of the interannual signal over the region. 相似文献
19.
20.
Konstantin V. Lebedev Max Yaremchuk Humio Mitsudera Iwao Nakano Gang Yuan 《Journal of Oceanography》2003,59(6):751-763
A finite-difference quasigeostrophic (QG) model of an open ocean region has been employed to produce a dynamically constrained
synthesis of acoustic tomography and satellite altimetry data with in situ observations. The assimilation algorithm is based upon the 4D variational data interpolation scheme controlled by the model's
initial and boundary conditions. The data sets analyzed include direct and differential travel times measured at the array
of five acoustic transceivers deployed by JAMSTEC in the region of the Kuroshio Extension in 1997, Topex/Poseidon altimetry,
CTD soundings, and ADCP velocity profiles. The region monitored is located within the area 27.5°–36.5°N, 143°–155°. The results
of assimilation show that mesoscale variability can be effectively reconstructed by five transceivers measuring direct and
reciprocal travel times supported by relatively sparse in situ measurements. The misfits between model and data lie within the observational error bars for all the data types used in assimilation.
We have compared the results of assimilation with the statistical inversion of travel time data and analyzed energy balances
of the optimized model solution. Energy exchange between the depth-averaged and shear components of the observed currents
reveals a weak decay of the barotropic mode at the rate of 0.2 ± 0.7⋅10−5 cm2/s3 due to topographic interaction. Mean currents in the region are unstable with an estimate of the available potential energy
flux from the mean current to the eddies of 4.7 ± 2.3⋅10−5 cm2/s3. Kinetic energy transition has the same sign and is estimated as 2.8 ± 2.5⋅10−5 cm2/s3. Potential enstrophy is transferred to the mesoscale at a rate of 5.5 ± 2.7⋅10−18 s−3. These figures provide observational evidence of the properties of free geostrophic turbulence which were predicted by theory
and observed in numerical experiments.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献