全文获取类型
收费全文 | 5051篇 |
免费 | 836篇 |
国内免费 | 934篇 |
专业分类
测绘学 | 746篇 |
大气科学 | 285篇 |
地球物理 | 1598篇 |
地质学 | 2765篇 |
海洋学 | 653篇 |
天文学 | 62篇 |
综合类 | 266篇 |
自然地理 | 446篇 |
出版年
2024年 | 28篇 |
2023年 | 104篇 |
2022年 | 155篇 |
2021年 | 171篇 |
2020年 | 218篇 |
2019年 | 230篇 |
2018年 | 207篇 |
2017年 | 267篇 |
2016年 | 255篇 |
2015年 | 237篇 |
2014年 | 352篇 |
2013年 | 378篇 |
2012年 | 297篇 |
2011年 | 356篇 |
2010年 | 234篇 |
2009年 | 361篇 |
2008年 | 394篇 |
2007年 | 377篇 |
2006年 | 317篇 |
2005年 | 266篇 |
2004年 | 260篇 |
2003年 | 185篇 |
2002年 | 193篇 |
2001年 | 143篇 |
2000年 | 172篇 |
1999年 | 110篇 |
1998年 | 107篇 |
1997年 | 90篇 |
1996年 | 70篇 |
1995年 | 60篇 |
1994年 | 41篇 |
1993年 | 42篇 |
1992年 | 36篇 |
1991年 | 13篇 |
1990年 | 24篇 |
1989年 | 11篇 |
1988年 | 11篇 |
1987年 | 14篇 |
1986年 | 8篇 |
1985年 | 5篇 |
1984年 | 4篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1980年 | 3篇 |
1979年 | 1篇 |
1978年 | 5篇 |
1977年 | 2篇 |
1976年 | 1篇 |
1954年 | 3篇 |
排序方式: 共有6821条查询结果,搜索用时 15 毫秒
101.
102.
Autoregressive models have been shown to adequately model the time series of significant wave height. However, since this series exhibits a seasonal component and has a non-gaussian nature, it is necessary to transform the series before a model can be fit to the data. Two different transformations that have been used in earlier work are shown not to be appropriate for all types of applications. A third transformation is proposed here, which combines the better features of the two earlier ones and which is appropriate for simulation work. This is demonstrated with an example of a series from Figueira da Foz, a location of the Portuguese Coast. 相似文献
103.
海岸河口潮流数值模拟的研究与进展 总被引:45,自引:2,他引:45
对海岸河口地区潮流场的数值模拟方法进行了较为系统的归纳总结和评述,对潮流数值模拟的发展趋势进行了分析. 相似文献
104.
速度在地震勘探中十分重要,压制多次波、偏移成像和地震反演都需要准确的速度模型。为了高效和准确的获取速度模型,基于时间域精细速度建模方法,利用疑似含气区的二维多道地震资料,针对初始模型、层位约束和基于人工速度拾取的速度反演3个方面开展了试验,探讨实际资料中时间域精细速度建模方法的关键点和效果。试验表明:无需人工速度拾取,时间域精细速度建模能够实现浅地层速度的准确反演,进而高效地完成浅地层速度异常的识别;层位约束能提高速度建模的效率和精度;在地层结构复杂区域,人工速度拾取有利于时间域精细速度建模。 相似文献
105.
In this paper, effort is made to demonstrate the quality of high-resolution regional ocean circulation model in realistically simulating the circulation and variability properties of the northern Indian Ocean(10°S–25°N,45°–100°E) covering the Arabian Sea(AS) and Bay of Bengal(BoB). The model run using the open boundary conditions is carried out at 10 km horizontal resolution and highest vertical resolution of 2 m in the upper ocean.The surface and sub-surface structure of hydrographic variables(temperature and salinity) and currents is compared against the observations during 1998–2014(17 years). In particular, the seasonal variability of the sea surface temperature, sea surface salinity, and surface currents over the model domain is studied. The highresolution model's ability in correct estimation of the spatio-temporal mixed layer depth(MLD) variability of the AS and BoB is also shown. The lowest MLD values are observed during spring(March-April-May) and highest during winter(December-January-February) seasons. The maximum MLD in the AS(BoB) during December to February reaches 150 m (67 m). On the other hand, the minimum MLD in these regions during March-April-May becomes as low as 11–12 m. The influence of wind stress, net heat flux and freshwater flux on the seasonal variability of the MLD is discussed. The physical processes controlling the seasonal cycle of sea surface temperature are investigated by carrying out mixed layer heat budget analysis. It is found that air-sea fluxes play a dominant role in the seasonal evolution of sea surface temperature of the northern Indian Ocean and the contribution of horizontal advection, vertical entrainment and diffusion processes is small. The upper ocean zonal and meridional volume transport across different sections in the AS and BoB is also computed. The seasonal variability of the transports is studied in the context of monsoonal currents. 相似文献
106.
A regional ocean circulation model with four-dimensional variational data assimilation scheme is configured to study the ocean state of the Indian Ocean region (65°E–95°E; 5°N–20°N) covering the Arabian Sea (AS) and Bay of Bengal (BoB). The state estimation setup uses 10 km horizontal resolution and 5 m vertical resolution in the upper ocean. The in-situ temperature and salinity, satellite-derived observations of sea surface height, and blended (in-situ and satellite-derived) observations of sea surface temperature alongwith their associated uncertainties are used for data assimilation with the regionally configured ocean model. The ocean state estimation is carried out for 61 days (1 June to 31 July 2013). The assimilated fields are closer to observations compared to other global state estimates. The mixed layer depth (MLD) of the region shows deepening during the period of assimilation with AS showing higher MLD compared to the BoB. An empirical forecast equation is derived for the prediction of MLD using the air–sea forcing variables as predictors. The surface and sub-surface (50 m) heat and salt budget tendencies of the region are also investigated. It is found that at the sub-surface, only the advection and diffusion temperature and salt tendencies are important. 相似文献
107.
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
108.
109.
110.