全文获取类型
收费全文 | 3500篇 |
免费 | 624篇 |
国内免费 | 729篇 |
专业分类
测绘学 | 108篇 |
大气科学 | 139篇 |
地球物理 | 1090篇 |
地质学 | 1330篇 |
海洋学 | 1649篇 |
天文学 | 102篇 |
综合类 | 212篇 |
自然地理 | 223篇 |
出版年
2024年 | 10篇 |
2023年 | 32篇 |
2022年 | 88篇 |
2021年 | 110篇 |
2020年 | 130篇 |
2019年 | 163篇 |
2018年 | 127篇 |
2017年 | 146篇 |
2016年 | 150篇 |
2015年 | 130篇 |
2014年 | 202篇 |
2013年 | 221篇 |
2012年 | 196篇 |
2011年 | 197篇 |
2010年 | 185篇 |
2009年 | 246篇 |
2008年 | 250篇 |
2007年 | 248篇 |
2006年 | 203篇 |
2005年 | 223篇 |
2004年 | 200篇 |
2003年 | 182篇 |
2002年 | 150篇 |
2001年 | 112篇 |
2000年 | 104篇 |
1999年 | 106篇 |
1998年 | 74篇 |
1997年 | 86篇 |
1996年 | 89篇 |
1995年 | 91篇 |
1994年 | 82篇 |
1993年 | 65篇 |
1992年 | 53篇 |
1991年 | 36篇 |
1990年 | 30篇 |
1989年 | 26篇 |
1988年 | 20篇 |
1987年 | 14篇 |
1986年 | 8篇 |
1985年 | 12篇 |
1984年 | 14篇 |
1983年 | 16篇 |
1982年 | 10篇 |
1981年 | 15篇 |
1973年 | 1篇 |
排序方式: 共有4853条查询结果,搜索用时 31 毫秒
91.
Zhang Jinshan Yu Guohua
Research Engineer River Harbour Department Nanjing Hydraulic Research Institute Nanjing Research Senior Engineer River Harbour Department Nanjing Hydraulic Research Institute Nanjing 《中国海洋工程》1995,(3)
- Based on field investigations, this paper analyzes three types of harbour basinns and navigation channel excavated on seabed in Jiaozhou Bay, get a general rule of deposition for excavated trough, it found that pollution is one of crucial factors resulting in the deposition of the excavated trough in the east shore of Jiaozhou Bay. With these results, it predicted the annual deposition thickness for the excavated trough and disclosed the fact that it can't be deposited deadly during one storm. At the same time, with two-dimensional numerical model, it studied the effects of the excavated trough and the reclamation near shore on tidal cureent and said that the excavated trough can decrease the current velocity passing through the trough about 10- 15%, but only limited inside and near the trough and there are no effect on other regions; reclamation can cut off the pollution sources and no obvious effect on the currents of the Jiaozhou Bay. Connecting the deep trough and Cangkou tidal channel with a new 相似文献
92.
本文对青岛—石臼所沿岸潮流特征进行了分析。实际观测资料表明,这一带潮流具有典型的往复流性质,并有较明显的不对称性和较大的垂直变化。文中指出涨落潮流不对称性是由于余流和分潮流影响的结果。讨论了不对称性随余流和分潮流的变化和潮流垂直梯度的特征。不对称和垂直梯度对泥沙运动和污染扩散的影响在文中也作了阐述。 相似文献
93.
Using an idealized ocean general circulation model, we examine the effect of “mixing hotspots” (localized regions of intense
diapycnal mixing) predicted based on internal wave-wave interaction theory (Hibiya et al., 2006) on the meridional overturning circulation of the Pacific Ocean. Although the assumed diapycnal diffusivity in the
mixing hotspots is a little larger than the predicted value, the upwelling in the mixing hotspots is not sufficient to balance
the deep-water production; out of 17 Sv of the downwelled water along the southern boundary, only 9.2 Sv is found to upwell
in the mixing hotspots. The imbalance as much as 7.8 Sv is compensated by entrainment into the surface mixed layer in the
vicinity of the downwelling region. As a result, the northward transport of the deep water crossing the equator is limited
to 5.5 Sv, much less than estimated from previous current meter moorings and hydrographic surveys. One plausible explanation
for this is that the magnitude of the meridional overturning circulation of the Pacific Ocean has been overestimated by these
observations. We raise doubts about the validity of the previous ocean general circulation models where diapycnal diffusivity
is assigned ad hoc to attain the current magnitude suggested from current meter moorings and hydrographic surveys. 相似文献
94.
A comprehensive numerical study on the three-dimensional structure of a turbulent jet in crossflow is performed. The jet-to-crossflow velocity ratio (R) varies in the range of 2 - 16; both vertical jets and inclined jets without excess streamwise momentum are considered. The numerical results of the Standard two-equation k-ε model show that the turbulent structure can be broadly categorised according to the jet-to-crossflow velocity ratio. For strong to moderate jet discharges, i.e. R> 4, the jet is characterized by a longitudinal transition through a bent-over phase during which the jet becomes almost parallel with the main freestream, to a sectional vortex-pair flow with double concentration maxima; the computed flow details and scalar mixing characteristics can be described by self-similar relations beyond a dimensionless distance of around 20-60. The similarity coefficients are only weakly dependent on R. The cross-section scalar field is kidney-shaped and bifurcated, vvith distinct double concentr 相似文献
95.
96.
INTRODUCTIONTheDenglouCape ,inthesouthwestoftheLeizhouPeninsula ,isatthenorthmarginoftropicalzone .SeveralresearchesandcartographiesoftheregionalgeomorphologyandQuater narygeology ,whichwerecarriedoutinthepast,allincludethisarea (MGL ,SCSIO ,CAS ,1 978;GPCSGRCZT… 相似文献
97.
1 .IntroductionTheglobalairtemperatureroseabout 0 .5~ 0 .6°Coverthepast 2 0thcentury ,andtheglobalmeansealevelincreasedbyabout2 0cmduringtheperiod .Theregionalmeansealevelriseswiththerisingglobalmeansealevel.Zuoetal.( 1 997)indicatedthatthemeanrisingrateofabsolutemeansealevelalongtheChinacoastontheassumptionofunifiedisostaticdatumis 2mm a .Woodworth( 1 999)analyzedsealevelspanning 1 76 8tothepresentinLiverpool,andobtainedaseculartrendforheperiodupto 1 880of0 .39± 0 .1 7mm a ,andatrendfort… 相似文献
98.
99.
100.
Abstract. Two sediment cores were collected in the southern Baltic Sea and sliced into 1.0cm-thick layers. Sediments of each layer were analysed for activities of 210Pb, 137Cs, 134Cs and for the density of meiobenthic organisms (meiofauna). Zones with the rapid mixing occur in the uppermost layers (0–3 cm) of the cores based on I34Cs profiles. The extent and density of meiofauna confirmed the rapid mixing and revealed layers with slow mixing (4–8 cm). Sedimentation rates were derived from 210Pb profiles below the mixing zones (1.21 and 1.72 mm a-I) and were confumed by 137Cs distribution. Of twenty-one major meiofauna taxa commonly found in the Baltic sediments, three were present in the cores. 相似文献