全文获取类型
收费全文 | 8277篇 |
免费 | 2029篇 |
国内免费 | 3831篇 |
专业分类
测绘学 | 922篇 |
大气科学 | 973篇 |
地球物理 | 2151篇 |
地质学 | 7068篇 |
海洋学 | 1142篇 |
天文学 | 240篇 |
综合类 | 1009篇 |
自然地理 | 632篇 |
出版年
2024年 | 38篇 |
2023年 | 118篇 |
2022年 | 321篇 |
2021年 | 372篇 |
2020年 | 323篇 |
2019年 | 384篇 |
2018年 | 346篇 |
2017年 | 342篇 |
2016年 | 358篇 |
2015年 | 364篇 |
2014年 | 332篇 |
2013年 | 373篇 |
2012年 | 370篇 |
2011年 | 786篇 |
2010年 | 524篇 |
2009年 | 684篇 |
2008年 | 309篇 |
2007年 | 444篇 |
2006年 | 637篇 |
2005年 | 654篇 |
2004年 | 1211篇 |
2003年 | 805篇 |
2002年 | 561篇 |
2001年 | 463篇 |
2000年 | 312篇 |
1999年 | 282篇 |
1998年 | 333篇 |
1997年 | 304篇 |
1996年 | 214篇 |
1995年 | 170篇 |
1994年 | 149篇 |
1993年 | 330篇 |
1992年 | 301篇 |
1991年 | 150篇 |
1990年 | 49篇 |
1989年 | 73篇 |
1988年 | 29篇 |
1987年 | 65篇 |
1986年 | 38篇 |
1984年 | 12篇 |
1982年 | 12篇 |
1980年 | 11篇 |
1978年 | 9篇 |
1977年 | 17篇 |
1976年 | 14篇 |
1950年 | 8篇 |
1940年 | 9篇 |
1937年 | 15篇 |
1933年 | 13篇 |
1924年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 17 毫秒
91.
Xu Shikai Wang Hongchuan Hong Guangwen
Engineer Nanjing Hydraulic Research Institute Nanjing .
Professor Research Institute of Coastal Ocean Engineering Hohai University Nanjing 《中国海洋工程》1996,(4)
To solve problems concerning wave elements and wave propagation, an effective way is the wave energy balance equation, which is widely applied in oceanography and ocean dynamics for its simple computation. The present papaer advances wave energy balance equations considering lateral energy transmission and energy loss as the governing equation for the study of wave refraction-diffraction. For the mathematical model, numerical simulation is made by means of difference method, and the result is verified with two examples. 相似文献
92.
Discussion on Coastal Erosion Near Xizhuang, Penglai, China 总被引:1,自引:0,他引:1
Wu Guiqiu Li Wei Professor First Institute of Oceanography State Oceanic Administration Qingdao Associate Researcher 《中国海洋工程》1994,(2)
-In this work, on the basis of the characteristics of coastal erosion near Xizhuang (Penglai, Shandong, China) and the in-situ measured data and theoretical calculation, the causes of coastal erosion there are obtained: (1) natural erosion, (2) beach sand borrowing, and (3) sand borrowing at the Dengzhou shoal near Xizhuang, which results in the loss of the function of the wave force resistance of the shoal. Since the wave energy is increased, the longshore sediment transport rate is increased. Coastal erosions are more and more serious. A scientific basis to reduced the calamity of coastal erosion in local area is presented. Some experiences are accumulated for studying coastal erosion. 相似文献
93.
Following Bagnold's approach, a relationship between sediment transport and energy dissipation is developed. The major assumption made in the study is that the near bed velocity plays a dominant role in the process of sediment transport. A general relationship between energy dissipation and sediment transport is first proposed. Then the equations for total sediment transport are derived by introducing the appropriate expression of energy dissipation rate under different conditions, such as open channel flows, combination of wave and current, as well as longshore sediment transport. Within the flows investigated, the derived relationships are fairly consistent with the available data over a wide range of conditions. 相似文献
94.
95.
1 .IntroductionRecentlygreatinteresthasbeenshowninthedevelopmentofverylargefloatingstructuressuchasMegaFloatofJapan (Isobe ,1 999)andMOBofUSA (Remmers ,1 999) .Owingtotheirextremelargesizeandgreatflexibility ,thecouplingbetweenthestructuraldeformationandfluidmotionissignifi cant.Thisisatypicalproblemofhydroelasticity .Efficientandaccurateestimationofthehydroelasticresponseofverylargefloatingstructuresinwavesisveryimportantfordesign .Manymethodshavebeenproposedinliteratureforthepredictiono… 相似文献
96.
97.
Modest observations and numerical experiments were conducted to investigate circulation and brackish water dispersal in a
coastal lagoon southwest of Taiwan. The Chi-Ku Lagoon, partially shielded from the sea by a string of sandbar barriers with
two entrances among them, receives modest and episodic runoff from Chi-Ku Stream. Flood and ebb tidal streams entering and
leaving the two entrances are found to converge and diverge in a flow stagnation area inside the lagoon. Under weak wind conditions,
brackish water is preferentially retained in the flow stagnation area. Besides the observations, scenario runs using a three-dimensional
numerical model also indicate strong modulation by monsoon winds. Both summer southwest monsoon and winter northeast monsoon
reduce brackish water retention; the latter is found to be more effective.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
98.
The large cylinder is a new-type structure that has been applied to harbor and offshore engineering. An analytic method of the relationship between loads and the structure displacement is developed based on the failure mode of deep embedded large cylinder structures. It can be used to calculate directly the soil resistance and the ultirnate bearing capacity of the structure under usage. A new criterion of the large cylinder structure, which discriminates the deep embedded cylinder from the shallow embedded cylinder, is defined. Model tests prove that the proposed method is feasible for the analysis of deep embedded large cylinder structures. 相似文献
99.
采用长期概率预报提供波浪要素设计值是海洋工程中不可缺少的内容之一,文中介绍了一种基於贝叶斯原理的新计算方法,它较传统统计方法有明显的优越性,不仅可以通过补充新信息不断修正原有的估算结果,而且可以避免传统方法带来诸多不确定性,文中以北海中部百年一遇设计波高为例进行了计算。 相似文献
100.
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