全文获取类型
收费全文 | 12771篇 |
免费 | 1676篇 |
国内免费 | 1515篇 |
专业分类
测绘学 | 3425篇 |
大气科学 | 1076篇 |
地球物理 | 2510篇 |
地质学 | 4339篇 |
海洋学 | 1175篇 |
天文学 | 152篇 |
综合类 | 1234篇 |
自然地理 | 2051篇 |
出版年
2024年 | 39篇 |
2023年 | 143篇 |
2022年 | 450篇 |
2021年 | 547篇 |
2020年 | 519篇 |
2019年 | 592篇 |
2018年 | 317篇 |
2017年 | 498篇 |
2016年 | 485篇 |
2015年 | 501篇 |
2014年 | 667篇 |
2013年 | 766篇 |
2012年 | 821篇 |
2011年 | 816篇 |
2010年 | 632篇 |
2009年 | 732篇 |
2008年 | 760篇 |
2007年 | 854篇 |
2006年 | 838篇 |
2005年 | 699篇 |
2004年 | 626篇 |
2003年 | 627篇 |
2002年 | 490篇 |
2001年 | 453篇 |
2000年 | 390篇 |
1999年 | 314篇 |
1998年 | 306篇 |
1997年 | 229篇 |
1996年 | 176篇 |
1995年 | 154篇 |
1994年 | 128篇 |
1993年 | 103篇 |
1992年 | 73篇 |
1991年 | 44篇 |
1990年 | 44篇 |
1989年 | 37篇 |
1988年 | 33篇 |
1987年 | 23篇 |
1986年 | 8篇 |
1985年 | 7篇 |
1984年 | 9篇 |
1983年 | 3篇 |
1982年 | 1篇 |
1980年 | 3篇 |
1978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 105 毫秒
51.
Toru?Iwata Keiko?Yoshikawa Katsutoshi?Nishimura Yoshihisa?Higuchi Takao?Yamashita Shigeru?Kato Eiji?OhtakiEmail author 《Journal of Oceanography》2004,60(6):995-1000
The measurements of the vertical transport of CO2 were carried out over the Sea of Japan using the specially designed pier of Kyoto University on September 20 to 22, 2000. CO2 fluxes were measured by the eddy correlation and aerodynamic techniques. Both techniques showed comparable CO2 fluxes during sea breeze conditions: −0.001 to −0.08 mg m−2s−1 with the mean of −0.05 mg m−2s−1. This means that the measuring site satisfies the fetch requirement for meteorological observations under sea breeze conditions. Moreover, the eddy diffusivity coefficient used in the aerodynamic technique is found to be consistent with the coefficient used in the eddy correlation technique. The present result leads us to conclude that the aerodynamic technique may be applicable to underway CO2 flux measurements over the ocean and may be used in place of the bulk technique. The important point is the need to maintain a measuring accuracy of CO2 concentration difference of the order of 0.1 ppmv on the research vessels or the buoys. 相似文献
52.
Information systems developed for different applications within the environmental domain have common characteristics, which can potentially be abstracted for sharing and reuse of design and software modules. This article presents an approach to designing for reuse by abstracting commonalities in the design of a Marine Information System (MIS), facilitating data management in a prototype operational monitoring, forecasting, and management system for the North Atlantic and the Nordic Seas. A detailed study of the requirements and data analysis was carried out, and Object-Oriented Technology (OOT) is employed to encapsulate abstractions and to promote reuse of code and design. This article identifies the Object-Oriented Frameworks (OOFW) required to build the MIS. It also provides guidelines to environmental scientists for restructuring legacy software and employing modern programming techniques. 相似文献
53.
1 .IntroductionAshiptravelingatseaundergoesundesirablewave inducedmotions ,namely ,surge ,sway ,heav ing ,rolling ,pitchingandyaw .Thesemotionsoftencauseproblemstothecrew ,theonboardequip mentand ,intheworstcase ,thesafetyofthevessel.Tominimizethewave inducedshipmotions ,controlsystemsmaybeapplied .Theaccuratemodelingofshipmotionsisthereforeveryimportantforshipdesignanddesignofmotioncontrolsystems .Manyresearchershavedevelopedshipmotionpredictionmethodsbasedonthepotentialflowtheo ries (Dong ,… 相似文献
54.
1 .IntroductionWiththedevelopmentofoceantechnology ,moreandmoreextremelylargeandlongflexibleoff shoreplatformsusedforoilexplorationanddrillingoperationarebuiltinhostileoceanenvironments .Ingeneral,thiskindofplatformsisanonlineardistributedparametersystemanditsnaturalfrequencyfallsclosertothedominantwavefrequencieswiththeincreaseofwaterdepth .Besides ,itsstructureisverycomplexandtheexternalwaveforceontheplatformisuncertain .Thus ,theseplatformsarepronetoexcessivewave inducedoscillationsunderbot… 相似文献
55.
56.
57.
随着Linux技术逐步走向成熟,嵌入式Linux技术在海洋自动观测系统中的应用将全面提高海洋观测系统整体性能,降低系统开发成本,进一步推进我国海洋自动观测系统产权自主化的建设。文章就如何研制适用于海洋自动观测系统的嵌入式Linux系统进行了论述。 相似文献
58.
点带石斑鱼人工育苗技术 总被引:21,自引:0,他引:21
通过58批次的人工育苗试验,总结点带石斑鱼人工育苗技术;阐述了育苗池、育苗的环境条件、鱼苗不同生长阶段的饵料及投喂方法、育苗水质管理及生产中的操作方法等;讨论了如何解决开口饵料问题和出现3个危险期的原因等。 相似文献
59.
地形坡度对多金属结核分布的控制作用 总被引:3,自引:3,他引:3
选取我国东太平洋多金属结核开辟区内的一个区域作为研究区,利用人工神经网络中应用最为广泛的BP网络,建立控制多金属结核分布的地质因素与多金属结核分布之间的映射关系,探讨地形坡度对多金属结核分布的控制作用.结果表明,在经度、纬度、水深、坡度四个因素中,坡度对结核分布影响程度最大;多金属结核主要分布于坡度小于5°的地方;当坡度小于5°时,丰度与地形坡度呈正相关,品位与地形坡度呈负相关,丰度与品位呈负相关;品位与坡度似呈指数关系,坡度增大,品位降低. 相似文献
60.
You Yage
YuZhi Associated Professor Guangzhou Institute of Energy Conversion Chinese Academy of Sciences Guangzhou
. Professor Guangzhou Institute of Energy Conversion Chinese Academy of Sciences Guangzhou 《中国海洋工程》1995,(4)
In this paper, the extreme wave loads on an on-shore wave power device are investigated. First, boundary element method is applied to solve the three dimensional potential problem based on the small amplitude wave assumption. Then the motion of the Oscillating Water Column (OWC) inside the device and its laods on the device are calculated in time domain. Several protective techniques often applied are simulated by changing the constraint of the upper end of the chamber of the device. Numerical results are used to judge the effectiveness of these techniques. The investigation shows that damping can not effectively restrain the motion of OWC when the period of incident wave is long, which may cause dangerous loads on the structure. The shut chamber can effectively restrain the motion of OWC, but alternatively cause high pressure in the chamber. A Contracting opening with a Taper (CT) can exhaust a great amount of kinetic energy of OWC, and significantly decrease the loads. It is a promising protective tec 相似文献