全文获取类型
收费全文 | 6547篇 |
免费 | 1299篇 |
国内免费 | 1943篇 |
专业分类
测绘学 | 1042篇 |
大气科学 | 537篇 |
地球物理 | 2348篇 |
地质学 | 3162篇 |
海洋学 | 1267篇 |
天文学 | 72篇 |
综合类 | 556篇 |
自然地理 | 805篇 |
出版年
2024年 | 26篇 |
2023年 | 68篇 |
2022年 | 227篇 |
2021年 | 260篇 |
2020年 | 345篇 |
2019年 | 389篇 |
2018年 | 327篇 |
2017年 | 303篇 |
2016年 | 360篇 |
2015年 | 417篇 |
2014年 | 462篇 |
2013年 | 441篇 |
2012年 | 492篇 |
2011年 | 511篇 |
2010年 | 432篇 |
2009年 | 495篇 |
2008年 | 433篇 |
2007年 | 455篇 |
2006年 | 497篇 |
2005年 | 414篇 |
2004年 | 402篇 |
2003年 | 323篇 |
2002年 | 250篇 |
2001年 | 220篇 |
2000年 | 197篇 |
1999年 | 185篇 |
1998年 | 140篇 |
1997年 | 125篇 |
1996年 | 104篇 |
1995年 | 106篇 |
1994年 | 90篇 |
1993年 | 73篇 |
1992年 | 47篇 |
1991年 | 34篇 |
1990年 | 20篇 |
1989年 | 28篇 |
1988年 | 15篇 |
1987年 | 17篇 |
1986年 | 11篇 |
1985年 | 15篇 |
1984年 | 5篇 |
1983年 | 7篇 |
1982年 | 5篇 |
1981年 | 2篇 |
1980年 | 5篇 |
1979年 | 4篇 |
1976年 | 1篇 |
1972年 | 1篇 |
1971年 | 1篇 |
1954年 | 1篇 |
排序方式: 共有9789条查询结果,搜索用时 31 毫秒
41.
1 .Introduction Wave breaking and associated whitecapping have long beeninteresting due totheir close relationto many fields of ocean study,including air-sea interaction,remote sensing,ocean engineering,aswell as wave dynamics .The breaking probabilityBan… 相似文献
42.
43.
44.
渤、黄、东海内潮的数值模拟 总被引:2,自引:0,他引:2
在全球的海洋中,中国东海和临近海域是最显著的内潮生成地之一。本文采用NODC(Levitus) World Ocean Atlas 1998提供的季平均温、盐资料,计算海水的密度,并计算垂向密度梯度的最大值点,得到一个较符合海水实际的密度分层。使用三维非线性数值模型(将海洋分为2层)研究了潮汐(M2,S2,K1,O1分潮)作用下渤黄东海的内潮,揭示了整个海区内潮起伏的空间分布,结果发现大振幅的波动均发生在台湾东北(冲绳海槽)海域和中国近海地形突变之处,其中前者更显著。对于各分潮模拟得到的表面潮与TOPEX/Poseidon高度计资料基本一致。研究结果表明上层海水的深度和厚度的梯度对内潮有一定的影响;冬季分布区域比夏季小,强度比夏季大。 相似文献
45.
本文从动力学的角度研究了台风流场与台风运动的关系,在实际预报中考虑地形摩擦改变的流场对台风移动的影响取得了明显的效果。 相似文献
46.
The upper layer (above 140 m depth) temperature in the western Philippine Sea near Taiwan was sampled using a coastal monitoring
buoy (CMB) with 15 attached thermistors during July 28–August 7, 2005. The data were collected every 10 min at 1, 3, 5, 10,
15, and 20 m using the CMB sensors, and every 15 sec at 15 different depths between 25 m and 140 m. Internal waves and solitons
were identified from the time-depth plot of the temperature field. Without the internal waves and solitons, the power spectra,
structure functions, and singular measures (representing the intermittency) of temperature field satisfy the power law with
multi-scale characteristics at all depths. The internal waves do not change the basic characteristics of the multifractal
structure. However, the internal solitons change the power exponent of the power spectra drastically, especially in the low
wave number domain; they also break down the power law of the structure function and increase the intermittency parameter.
The physical mechanisms causing these different effects need to be explored further. 相似文献
47.
V.Hachemi Safai 《Applied Ocean Research》1983,5(4):215-225
The paper presents a theoretical and numerical approach to the dynamical behaviour of risers in deep water which takes into account two types of nonlinearity; that due to viscous drag forces and that due to the large displacements of the riser when submitted to strong axial loads. As the second nonlinearity may have a significant influence upon the behaviour of risers in deep water, a method for automatically updating the structural geometry during the dynamic analysis is given. A computer programme has been written for this purpose. 相似文献
48.
利用历史资料和Landsat TM卫星遥感图像,研究了唐山市沿海地区湿地结构自上世纪80年代以来的演变特征,着重对1987~2004年陡河——滦河之间的湿地结构类型进行了识别,绘制了不同时期的湿地面积解译图。利用Mapinfo制图软件计算出两个时期的面积转化矩阵,对该区主要湿地类型浅海水域、滩涂、芦苇沼泽、水稻田、养殖场、盐田等湿地的面积进行了年份比较,从而分析得出唐山市沿海湿地结构从80年代至今以来破碎化加重,应该加强湿地结构的动态监测。 相似文献
49.
50.
Waterfront retaining walls supporting dry backfill are subjected to hydrostatic pressure on upstream face and earth pressure on the downstream face. Under seismic conditions, if such a wall retains a submerged backfill, additional hydrodynamic pressures are generated. This paper pertains to a study in which the effect of earthquakes along with the hydrodynamic pressure including inertial forces on such a retaining wall is observed. The hydrodynamic pressure is calculated using Westergaard's approach, while the earth pressure is calculated using Mononobe-Okabe's pseudo-static analysis. It is observed that when the horizontal seismic acceleration coefficient is increased from 0 to 0.2, there is a 57% decrease in the factor of safety of the retaining wall in sliding mode. For investigating the effect of different parameters, a parametric study is also done. It is observed that if φ is increased from 30° to 35°, there is an increase in the factor of safety in the sliding mode by 20.4%. Similar observations were made for other parameters as well. Comparison of results obtained from the present approach with [Ebeling, R.M., Morrison Jr, E.E., 1992. The seismic design of waterfront retaining structures. US Army Technical Report ITL-92-11. Washington DC] reveal that the factor of safety for static condition (kh=0), calculated by both the approaches, is 1.60 while for an earthquake with kh=0.2, they differ by 22.5% due to the consideration of wall inertia in the present study. 相似文献