全文获取类型
收费全文 | 11279篇 |
免费 | 1817篇 |
国内免费 | 2374篇 |
专业分类
测绘学 | 600篇 |
大气科学 | 2409篇 |
地球物理 | 2799篇 |
地质学 | 5247篇 |
海洋学 | 1293篇 |
天文学 | 942篇 |
综合类 | 1022篇 |
自然地理 | 1158篇 |
出版年
2024年 | 27篇 |
2023年 | 137篇 |
2022年 | 373篇 |
2021年 | 427篇 |
2020年 | 361篇 |
2019年 | 449篇 |
2018年 | 498篇 |
2017年 | 476篇 |
2016年 | 605篇 |
2015年 | 478篇 |
2014年 | 612篇 |
2013年 | 619篇 |
2012年 | 573篇 |
2011年 | 591篇 |
2010年 | 660篇 |
2009年 | 602篇 |
2008年 | 573篇 |
2007年 | 541篇 |
2006年 | 438篇 |
2005年 | 414篇 |
2004年 | 315篇 |
2003年 | 336篇 |
2002年 | 304篇 |
2001年 | 361篇 |
2000年 | 364篇 |
1999年 | 556篇 |
1998年 | 498篇 |
1997年 | 448篇 |
1996年 | 461篇 |
1995年 | 390篇 |
1994年 | 328篇 |
1993年 | 311篇 |
1992年 | 254篇 |
1991年 | 202篇 |
1990年 | 162篇 |
1989年 | 133篇 |
1988年 | 136篇 |
1987年 | 77篇 |
1986年 | 63篇 |
1985年 | 48篇 |
1984年 | 35篇 |
1983年 | 31篇 |
1982年 | 43篇 |
1981年 | 35篇 |
1980年 | 21篇 |
1979年 | 20篇 |
1976年 | 9篇 |
1974年 | 10篇 |
1973年 | 11篇 |
1958年 | 18篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
J. M. Lort W. Q. Limond J. Segoufin Ph. Patriat J. R. Delteil B. Damotte 《Marine Geophysical Researches》1979,4(1):71-89
This paper presents seismic reflection and refraction data from the Mozambique Channel, collected between 1971 and 1973. A deep sedimentary basin (up to 5 km of sediments) opens southwards to the Mozambique Basin, and is bounded to the east by the Davie Ridge and beyond by the marginal plateau of Malagasy. A continuous reflector (C), possibly of Cretaceous age, is identified between layers having seismic interval velocities of 2.4–2.8 km/s and 3.1–3.4 km/s. The deepest sediments have velocities of 4.5–4.9 km/s and overlie a layer with velocity 5.5 km/s, which may be volcanic in the north-east of the Channel.The crust occupying most of the Channel is probably pre-Cretaceous in age, and may be largely continental in nature. This is supported by subdued magnetic anomalies and the possibility of a continuous Karroo sedimentary section across the northern Channel. The oceanic crust of the Mozambique Basin may extend as far north as 24°S, into the western Channel only. The problem of the origin of the Mozambique Channel remains unresolved, although a long sedimentary history indicates that Malagasy may have separated from Mainland Africa prior to Karroo times. The Davie Ridge may possibly represent a relict strike-slip fault, which permitted movement along a north-south line. 相似文献
102.
西沙群岛及其附近海域多毛类动物地理学的研究 总被引:5,自引:1,他引:5
西沙群岛及其附近海域蕴藏着极其丰富的水产资源,是我国的良好渔场之一,自古以来就是我国渔民的渔捞基地.解放以来,在党的领导下,对我国神圣领土西沙群岛进行了大规模的开发和建设.中国科学院海洋研究所和中国科学院南海海洋研究所等单位,进行了多次海洋生物资源调查,我们曾报告过113种浮游和底栖多毛类.根据1975-1976年补充调查的标本,又发现了过去未报告过的多毛类70种,截至目前西沙群岛及其附近海域的多毛类共有183种.本文根据现在掌握的资料对我国西沙群岛及其附近海域多毛类动物地理学做一初步分析. 相似文献
103.
本文报道了1990年在平湖对虾养殖场用几种药物治疗聚缩虫病所做的试验。结果表明,高锰酸钾和新洁尔灭的疗效较为显著。 相似文献
104.
Q. Huggett 《Marine Geophysical Researches》1990,12(1-2):69-81
Although the optical properties of seawater at extreme depths are more suitable for underwater photography than those at the surface or on continental shelves, they still impose severe limitations on long-range wide area bottom photography. Additionally, deep ocean operations impose technical limitations on control, power and bandwidth. This chapter reviews the approaches contemplated or made towards improving the camerato-target range in underwater photography in the deep ocean. Further significant improvements await advances in control, power/light sources and bandwidth reduction. With the developments now contemplated, TV and video systems will eventually present a strong challenge to emulsion film techniques. 相似文献
105.
A new three-dimensional, non-hydrostatic free surface flow model is presented. For simulating water wave motions over uneven bottoms, the model employs an explicit project method on a Cartesian the staggered gird system to solve the complete three-dimensional Navier–Stokes equations. A bi-conjugated gradient method with a pre-conditioning procedure is used to solve the resulting matrix system. The model is capable of resolving non-hydrostatic pressure by incorporating the integral method of the top-layer pressure treatment, and predicting wave propagation and interaction over irregular bottom by including a partial bottom-cell treatment. Four examples of surface wave propagation are used to demonstrate the capability of the model. Using a small of vertical layers (e.g. 2–3 layers), it is shown that the model could effectively and accurately resolve wave shoaling, non-linearity, dispersion, fission, refraction, and diffraction phenomena. 相似文献
106.
On the radiation and diffraction of linear water waves by an infinitely long rectangular structure submerged in oblique seas 总被引:1,自引:0,他引:1
The radiation and diffraction of linear water waves by an infinitely long rectangular structure submerged in oblique seas of finite depth is investigated. The analytical expressions for the radiated and diffracted potentials are derived as infinite series by use of the method of separation of variables. The unknown coefficients in the series are determined by the eigenfunction expansion matching method. The expressions for wave forces, hydrodynamic coefficients and reflection and transmission coefficients are given and verified by the boundary element method. Using the present analytical solution, the hydrodynamic influences of the angle of incidence, the submergence, the width and the thickness of the structure on the wave forces, hydrodynamic coefficients, and reflection and transmission coefficients are discussed in detail. 相似文献
107.
Sloshing in a two-dimensional rectangular tank in horizontal motion is analysed based on the velocity potential theory. It is found that even when the first-order excitation is away from all the natural frequencies of the tank, second-order resonance can still occur when the sum-frequency or the difference-frequency is equal to one of the natural frequencies corresponding to the even mode. However, such resonance is not excited when the sum or difference frequency is equal to the natural frequency of an odd mode. 相似文献
108.
109.
根据海南岛榆林验潮站1954~1992年连续39a潮位观测资料,经过统一基准面校正后,运用多种统计分析方法研究,得出近40a来海南岛南岸的相对海平面变化呈上升趋势,相应的平均上升速率为0.64mm/a,这一数值较近百年来1~2mm/a的全球海平面上升速率明显偏小,反映出同期海南岛南岸的地面是微弱抬升的。 相似文献
110.
本文采用1985年12月12日至1986年2月8日“向阳红14”号调查船在太平洋调查所获海洋水文气象资料,计算了四种热交换量。结果表明:海-气热输送与天气系统和海洋水文条件关系密切。冬季,在各种天气系统条件下西太平洋及中太平洋的大气主要是从海洋得到热量,其中以黑潮流经的海域最为明显,而热交换的方式主要是海洋以潜热的形式把热量输送给大气。 相似文献