全文获取类型
收费全文 | 11179篇 |
免费 | 2756篇 |
国内免费 | 5236篇 |
专业分类
测绘学 | 1386篇 |
大气科学 | 1511篇 |
地球物理 | 2674篇 |
地质学 | 8845篇 |
海洋学 | 2163篇 |
天文学 | 275篇 |
综合类 | 1122篇 |
自然地理 | 1195篇 |
出版年
2024年 | 66篇 |
2023年 | 163篇 |
2022年 | 380篇 |
2021年 | 482篇 |
2020年 | 384篇 |
2019年 | 503篇 |
2018年 | 413篇 |
2017年 | 404篇 |
2016年 | 349篇 |
2015年 | 526篇 |
2014年 | 461篇 |
2013年 | 600篇 |
2012年 | 610篇 |
2011年 | 1087篇 |
2010年 | 889篇 |
2009年 | 1057篇 |
2008年 | 723篇 |
2007年 | 843篇 |
2006年 | 1070篇 |
2005年 | 1031篇 |
2004年 | 1525篇 |
2003年 | 1004篇 |
2002年 | 773篇 |
2001年 | 631篇 |
2000年 | 432篇 |
1999年 | 328篇 |
1998年 | 334篇 |
1997年 | 317篇 |
1996年 | 203篇 |
1995年 | 164篇 |
1994年 | 140篇 |
1993年 | 341篇 |
1992年 | 317篇 |
1991年 | 154篇 |
1990年 | 54篇 |
1989年 | 77篇 |
1988年 | 23篇 |
1987年 | 61篇 |
1986年 | 33篇 |
1984年 | 13篇 |
1982年 | 9篇 |
1979年 | 15篇 |
1978年 | 10篇 |
1977年 | 15篇 |
1976年 | 18篇 |
1950年 | 10篇 |
1940年 | 9篇 |
1937年 | 15篇 |
1934年 | 9篇 |
1933年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
121.
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
122.
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
123.
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
124.
郑平胜 《海洋学报(英文版)》1986,5(3):456-456
Some unusual features have been analysed in this paper on the sea conditions ofnorthwestern East China Sea and the fisheries of Mackerel, Round Scad, Sardines off Zhejiangin the autumn of 1983, based on the data of the past years. The findings are as follows: 1. The low-salinity water area formed by the Changjiang River runoff emptying intothe sea expanded by three times as campared with that of 1978 (a poor runoff year). The 相似文献
125.
126.
1 .IntroductionRecentlygreatinteresthasbeenshowninthedevelopmentofverylargefloatingstructuressuchasMegaFloatofJapan (Isobe ,1 999)andMOBofUSA (Remmers ,1 999) .Owingtotheirextremelargesizeandgreatflexibility ,thecouplingbetweenthestructuraldeformationandfluidmotionissignifi cant.Thisisatypicalproblemofhydroelasticity .Efficientandaccurateestimationofthehydroelasticresponseofverylargefloatingstructuresinwavesisveryimportantfordesign .Manymethodshavebeenproposedinliteratureforthepredictiono… 相似文献
127.
128.
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
129.
中国台湾地区地处欧亚板块与菲律宾海板块之间,地震活动频繁.本文报道了 我国台湾地区及其邻近海域1985~2002年间5.5级以上地震的条带内外频度比分 布,并着重研究了1999—2002年中发生的3次7.5级以上地震前的条带现象.其结 果表明:台湾地区近期发生的3次7.5级以上大地震前,5.5级以上地震呈条带分 布.这些条带符合条带内地震个数Nin≥6的条件,符合条带内、外频度比Nin/(Nin Nout)≥75%的条件,也符合条带长宽比大于5的要求,只是与板内地震条带相比,条 带的长度较短. 相似文献
130.
氮磷营养盐与有机汞联合作用对微氏海链藻生长的影响 总被引:1,自引:1,他引:1
探讨在高营养盐(氮、磷、硅分别为浮游植物生长的营养盐阚值≥40、50、9倍)条件下,氮浓度及氮磷摩尔比值[n(N)/n(P)]变化、汞(甲基汞和乙基汞)对微氏海链藻(Thalassiosira weissflogii)生长的影响。结果表明,高营养盐区海链藻的生长遵循营养盐限制的唯一因子论;氮浓度和氮磷比提高促进生长,当n(N)/n(P)=64则呈抑制效应;生长初期,甲基汞和乙基汞均产生毒性抑制作用,生长中后期,适量甲基汞(浓度≤1.0μg/L)、乙基汞(浓度≤0.5μg/L)却呈兴奋效应,促进生长;汞形态不同,剂量-效应关系不同。氮和有机汞是海链藻生长的刺激因子。适度有机汞污染与氮富营养化对微氏海链藻的生长产生协同效应。 相似文献