全文获取类型
收费全文 | 10520篇 |
免费 | 1307篇 |
国内免费 | 1345篇 |
专业分类
测绘学 | 2745篇 |
大气科学 | 1051篇 |
地球物理 | 2396篇 |
地质学 | 2744篇 |
海洋学 | 936篇 |
天文学 | 265篇 |
综合类 | 1057篇 |
自然地理 | 1978篇 |
出版年
2024年 | 41篇 |
2023年 | 160篇 |
2022年 | 463篇 |
2021年 | 562篇 |
2020年 | 574篇 |
2019年 | 476篇 |
2018年 | 357篇 |
2017年 | 480篇 |
2016年 | 499篇 |
2015年 | 512篇 |
2014年 | 597篇 |
2013年 | 702篇 |
2012年 | 681篇 |
2011年 | 625篇 |
2010年 | 489篇 |
2009年 | 557篇 |
2008年 | 585篇 |
2007年 | 662篇 |
2006年 | 579篇 |
2005年 | 451篇 |
2004年 | 459篇 |
2003年 | 415篇 |
2002年 | 343篇 |
2001年 | 333篇 |
2000年 | 278篇 |
1999年 | 242篇 |
1998年 | 233篇 |
1997年 | 171篇 |
1996年 | 121篇 |
1995年 | 124篇 |
1994年 | 118篇 |
1993年 | 81篇 |
1992年 | 47篇 |
1991年 | 38篇 |
1990年 | 27篇 |
1989年 | 20篇 |
1988年 | 27篇 |
1987年 | 14篇 |
1986年 | 8篇 |
1985年 | 5篇 |
1984年 | 7篇 |
1983年 | 2篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1979年 | 1篇 |
1977年 | 3篇 |
1954年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
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
72.
1997~ 1 998年出现了 2 0世纪中最强的一次厄尔尼诺事件。根据长江洪水与厄尔尼诺事件的实测资料 ,指出 1 998年的长江巨洪与这次厄尔尼诺事件具有较密切的关系。同时讨论了厄尔尼诺事件影响长江洪水的物理途径 ,这对长江巨洪的长期及超长期预报具有较重要的指示作用 相似文献
73.
A novel method for prediction of the load carrying capacity of a corroded reinforced concrete beam (CRCB) is presented in the paper. Nine reinforced concrete beams, which had been working in an aggressive environment for more than 10 years, were tested in the laboratory. Comprehensive tests, including flexural test, strength test for corroded concrete and rusty rebar, and pullout test for bond strength between concrete and rebar, were condueted. The flexural test results of CRCBs reveal that the distribution of surface cracks on the beams shows a fractal behavior. The relationship between the fractal dimensions and mechanical properties of CRCBs is then studied. A prediction model based on artificial neural network (ANN) is established by the use of the fractal dimension as the corrosion index, together with the basic intbrmation of the beam. The validity of the prediction model is demonstrated through the experimental data, and satisfactory resuits are achieved. 相似文献
74.
75.
76.
77.
78.
基于模糊神经网络(FNN)的赤潮预警预测研究 总被引:1,自引:0,他引:1
为研究各种理化因子与赤潮藻类浓度间的非线性对应规律和有效预测赤潮藻类浓度,构建了基于BP 算法的一个四层模糊神经网络模型。将模糊神经网络(FNN)技术引入赤潮预测研究,并与普通 BP 网络、RBF 网络的结果作比较,结果表明,该模型能够较好地反演出各种理化因子与夜光藻密度的非线性对应变化规律,有更好的预测功能。 相似文献
79.
The effects of free-surface waves on the floating structures are of great importance in the offshore industry. Among the six degrees of motions of a surface ship the absence of restoring forces in surge, sway and yaw led to critical situations for moored ships in the recent times. The order of forces in horizontal plane and their exciting frequencies are matters of interest. The resonance with the presence of moored chains led to many accidents in the recent past. The lines in dry conditions may not give good damping and in wet condition they may trigger the system to chaotic motions and jumps. Two different loading conditions of a container ship model are tested with waves in laboratory conditions in two different drafts. The mooring lines are chosen as per scale law and the energy under the response spectrum is determined from the plots. The results give new insights into the movement of a berthed ships subjected to waves. Response of the moored ship to different loading conditions in different water depths are discussed in this paper. The paper gives the order of energy due to first-order and slowly varying movement of a berthed container model in a towing tank. 相似文献
80.
岬间海湾岸线平衡形态神经网络模型 总被引:1,自引:0,他引:1
讨论了目前海湾岸线平衡形态经验模型存在的不足之处。从沿岸输沙公式入手,阐述了平衡岸线的机理模式,重新定义了平衡海湾的“下岬角”,给出了模型参数与主波向的具体计算方法,并以华南典型海湾为学习样本,建立了岸线平衡形态的神经网络模型。通过模拟海湾与实际稳定海湾——乌场湾间的对比分析,表明所建神经网络模型是较抛物模型更为理想的平衡岸线模型。 相似文献