全文获取类型
收费全文 | 3216篇 |
免费 | 598篇 |
国内免费 | 1102篇 |
专业分类
测绘学 | 177篇 |
大气科学 | 76篇 |
地球物理 | 1178篇 |
地质学 | 2597篇 |
海洋学 | 395篇 |
天文学 | 85篇 |
综合类 | 323篇 |
自然地理 | 85篇 |
出版年
2023年 | 2篇 |
2021年 | 3篇 |
2018年 | 2篇 |
2017年 | 3篇 |
2016年 | 1篇 |
2015年 | 8篇 |
2014年 | 4篇 |
2013年 | 34篇 |
2012年 | 10篇 |
2011年 | 443篇 |
2010年 | 213篇 |
2009年 | 372篇 |
2008年 | 118篇 |
2007年 | 180篇 |
2006年 | 318篇 |
2005年 | 367篇 |
2004年 | 891篇 |
2003年 | 529篇 |
2002年 | 290篇 |
2001年 | 183篇 |
2000年 | 85篇 |
1999年 | 107篇 |
1998年 | 131篇 |
1997年 | 143篇 |
1996年 | 79篇 |
1995年 | 62篇 |
1994年 | 33篇 |
1993年 | 124篇 |
1992年 | 60篇 |
1991年 | 25篇 |
1990年 | 6篇 |
1989年 | 18篇 |
1988年 | 4篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1982年 | 1篇 |
1979年 | 1篇 |
1950年 | 8篇 |
1944年 | 1篇 |
1943年 | 6篇 |
1942年 | 1篇 |
1940年 | 8篇 |
1937年 | 12篇 |
1934年 | 4篇 |
1933年 | 7篇 |
1931年 | 1篇 |
1928年 | 4篇 |
1927年 | 4篇 |
1926年 | 2篇 |
1924年 | 3篇 |
排序方式: 共有4916条查询结果,搜索用时 15 毫秒
41.
Liu Baohua Wu Jinlong Xin Baisen Peng Chao . First Institute of Oceanography State Oceanic Administration Qingdao China . Ocean University of Qingdao Qingdao China 《海洋学报(英文版)》1999,(2)
INTRODUCTIONTo study the compensation model of sea topography and isostatic states by using toPOgraphicand gravity data, is an imPOrtant mean for further researching deep structures as elastic structure,stress state of lithosphere, and so on. Since Airy and Pratt proPOsed local isostatic model in the1850' s, greater development on the theoretical study has been attained. Veining Meinesz (1941 )introduced regional compensation mechanism by considering it as floating crust in elastic fie… 相似文献
42.
Corrosion and fatigue cracks are major threats to the structural integrity of aging offshore platforms. For the rational estimation of the safety levels of aging platforms, a global reliability assessment approach for aging offshore platforms with corrosion and fatigue cracks is presented in this paper. The base shear capacity is taken as the global ultimate strength of the offshore platforms. It is modeled as a random process that decreases with time in the presence of corrosion and fatigue crack propagati... 相似文献
43.
For the study on the ice-induced vibration of a compliant mono-cone structure,a series of model tests were performed from 2004 to 2006.In these tests,the ice sheet before the compliant conical structure was found to be failed in two-time breaking.Based on this important finding,model tests study of the ice force on a compliant multi-cone structure were performed from 2006 to 2007.in these tests,the ice sheet broke before each single cone non-simultaneously.The exciting energy of the total ice force was found to be in a wide range of frequencies,and the structure can be easily excited with nonlinear resonance. 相似文献
44.
It is necessary to pay more attention to the durability of concrete undergoing freeze-thaw cycles and seawater attack simultaneously.Investigated are the effects of water-binder ratio,fly ash (FA) contents and air-entraining agent on resistance to frost and chloride diffusion of marine concrete blended with FA in natural seawater.The results show that fly ash does not improve the frost resistance of concrete but can improve its resistance to chloride diffusion by addition of less than 30%.The resistance to frost and chloride diffusion of FA concrete can be improved with the decrease of water-binder ratio,and FA may improve both of them simultaneously only being mixed with air-entraining agent.A ratio (named as R) of the frost-resisting durability factor to chloride diffusion coefficient can be used to evaluate the durability of marine concrete.Scanning electron microscope (SEM) analyses are consistent with the evaluations by the value of R. 相似文献
45.
The Yangtze Estuary, the largest estuary in China, is under an obvious interaction between runoff and astronomical tide. The research on the interaction is very important for the exploitation and utilization of water resources in this area. A horizontal 2D hydrodynamic numerical model is established and verified in the present study with the modeling range from Datong to the Yangtze Estuary. Based on the comparison of high water levels under the interaction between different runoff and estuarine dynamics, s... 相似文献
46.
Nonlinear Effect of Wave Propagation in Shallow Water 总被引:5,自引:2,他引:5
LI Ruijie WANG Houjie
Associate Professor Ocean University of Qingdao Qingdao P. R. China.
Graduate Student Ocean University of Qingdao Qingdao P. R. China. 《中国海洋工程》1999,(1)
—In this paper,a nonlinear model is presented to describe wave transformation in shallow wat-er with the zero-vorticity equation of wave-number vector and energy conservation equation.Thenonlinear effect due to an empirical dispersion relation(by Hedges)is compared with that of Dalrymple'sdispersion relation.The model is tested against the laboratory measurements for the case of a submergedelliptical shoal on a slope beach,where both refraction and diffraction are significant.The computation re-sults,compared with those obtained through linear dispersion relation.show that the nonlinear effect ofwave transformation in shallow water is important.And the empirical dispersion relation is suitable for re-searching the nonlinearity of wave in shallow water. 相似文献
47.
The Optimal Design of TMD for Offshore Structures 总被引:15,自引:0,他引:15
This paper presents the optimal design procedure of Tuned Mass Damper(TMD)for re-ducing vibration of an actual steel jacket offshore platform excited by random wave loading.In this study,a frequency domain is taken.The force on the structure is determined by use of the linearized Morisonequation for an input Power Spectral Density(PSD)of wave elevation.The sensitivity of optimum valuesof TMD to characteristic parameters of random wave spectrum is analyzed.An optimized TMD designfor the modeled platform is given based on design conditions and the findings of the study. 相似文献
48.
DING Keqin DUAN Menglan FU Pinsheng LIU Chuntu
Ph. D. Associate Professor Research Department Center of Boiler Pressure Vessel Inspection Research Beijing P. R. China
Ph. D. Research Professor CCS Research Development Center China Classification Society Beijing P. R. China
Lecturer Yumen Petroleum School of Technique Technology Yumen P. R. China Research Professor 《中国海洋工程》1999,(4)
A simple probabilistic model for predicting crack growth behavior under random loading is pre-sented.In the model,the parameters c and m in the Paris-Erdogan Equation are taken as random variables,and their stochastic characteristic values are obtained through fatigue crack propagation tests on an offshorestructural steel under constant amplitude loading.Furthermore,by using the Monte Carlo simulation tech-nique,the fatigue crack propagation life to reach a given crack length is predicted.The tests are conducted toverify the applicability of the theoretical prediction of the fatigue crack propagation. 相似文献
49.
基于国内首次在越南巴达棱湾2007年5月—2008年4月的风、浪现场实测资料,对该海区的风和浪的基本特征进行了初步统计分析,得出如下结论:1)海区季风现象明显,冬季(夏季)盛行东北(西南)季风,东北季风强度大于西南季风强度;2)海区波向与风向基本一致,即冬季(夏季)常浪向和强浪向均是E(SSW)向浪;3)海区以风浪为主,波谱表现为多峰结构,主峰多为单峰和双峰结构,东北季风(西南季风)期间,峰值周期对应的波向为E(SSW)向,台风对海域的波谱影响明显。文章结果对认识与我国同纬度的南沙群岛海域的风、浪特点具有一定参考价值。 相似文献
50.