全文获取类型
收费全文 | 6436篇 |
免费 | 1661篇 |
国内免费 | 2086篇 |
专业分类
测绘学 | 899篇 |
大气科学 | 1180篇 |
地球物理 | 1531篇 |
地质学 | 3935篇 |
海洋学 | 1148篇 |
天文学 | 87篇 |
综合类 | 586篇 |
自然地理 | 817篇 |
出版年
2024年 | 26篇 |
2023年 | 121篇 |
2022年 | 333篇 |
2021年 | 356篇 |
2020年 | 304篇 |
2019年 | 388篇 |
2018年 | 346篇 |
2017年 | 350篇 |
2016年 | 349篇 |
2015年 | 425篇 |
2014年 | 418篇 |
2013年 | 535篇 |
2012年 | 604篇 |
2011年 | 567篇 |
2010年 | 584篇 |
2009年 | 574篇 |
2008年 | 504篇 |
2007年 | 501篇 |
2006年 | 510篇 |
2005年 | 387篇 |
2004年 | 352篇 |
2003年 | 261篇 |
2002年 | 241篇 |
2001年 | 239篇 |
2000年 | 191篇 |
1999年 | 151篇 |
1998年 | 81篇 |
1997年 | 106篇 |
1996年 | 74篇 |
1995年 | 53篇 |
1994年 | 50篇 |
1993年 | 42篇 |
1992年 | 32篇 |
1991年 | 25篇 |
1990年 | 21篇 |
1989年 | 17篇 |
1988年 | 13篇 |
1987年 | 8篇 |
1986年 | 6篇 |
1985年 | 7篇 |
1984年 | 5篇 |
1983年 | 2篇 |
1982年 | 3篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1958年 | 1篇 |
1957年 | 2篇 |
1954年 | 7篇 |
1927年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
71.
The North Yellow Sea Basin ( NYSB ), which was developed on the basement of North China (Huabei) continental block, is a typical continental Mesozoic Cenozoic sedimentary basin in the sea area. Its Mesozoic basin is a residual basin, below which there is probably a larger Paleozoic sedimentary basin. The North Yellow Sea Basin comprises four sags and three uplifts. Of them, the eastern sag is a Mesozoic Cenozoic sedimentary sag in NYSB and has the biggest sediment thickness; the current Korean drilling wells are concentrated in the eastern sag. This sag is comparatively rich in oil and gas resources and thus has a relatively good petroleum prospect in the sea. The central sag has also accommodated thick Mesozoic-Cenozoic sediments. The latest research results show that there are three series of hydrocarbon source rocks in the North Yellow Sea Basin, namely, black shales of the Paleogene, Jurassic and Cretaceous. The principal hydrocarbon source rocks in NYSB are the Mesozoic black shale. According to the drilling data of Korea, the black shales of the Paleogene, Jurassic and Cretaceous have all come up to the standards of good and mature source rocks. The NYSB owns an intact system of oil generation, reservoir and capping rocks that can help hydrocarbon to form in the basin and thus it has the great potential of oil and gas. The vertical distribution of the hydrocarbon resources is mainly considered to be in the Cretaceous and then in the Jurassic. 相似文献
72.
渤海南部表层沉积的相特征 总被引:1,自引:0,他引:1
通过海上调查及实验室分析,查明渤海南部表层沉积物在结构类型、矿物组合、生物组分及沉积构造等相特征方面具有明显的分区性。渤海南部存在五种沉积相:黄河水下三角洲相、陆架盆地相、海湾相、潮流浅滩相及古滨岸相。黄河水下三角洲相从河口延至水深15—20米处,沉积速率很高,沉积物富含碎屑云母及CaCo_3。陆架盆地相的沉积为粉砂质粘土,具有生物扰动构造。 相似文献
73.
1 .Introduction Submarine pipelines are one of the safest and the least environmentally disruptive means for ma-rine gas or oil transport . With the development of exploitation of submarine oil or gas ,the safety ofsubmarine pipelines has becomethe major … 相似文献
74.
闽江河口区湿地生态旅游环境容量研究 总被引:3,自引:0,他引:3
本文讨论了生态旅游环境容量的定义及内涵,分析了生态旅游环境容量的特征及构成,在此基础上估算了闽江河口区湿地生态旅游环境容量.结果表明:闽江河口区湿地生态旅游环境容量的限制因子是鳝鱼滩自然保护区生态旅游环境空间容量.鳝鱼滩旅游步行道可分成南路和北路,北路为水路游线,南路为陆路游线.北路游线环境空间日容量为800人次/d,南路游线环境空间日容量为1144人次/d.鳝鱼滩湿地生态旅游环境空间年容量为451202人次/a.这一环境容量可作为闽江河口区湿地生态旅游活动环境容量的最高限制量. 相似文献
75.
土工布充砂袋的应用及其研究进展 总被引:10,自引:1,他引:10
对土工布充砂袋技术和国内外的应用进行了介绍。鉴于土工布充砂袋属于一种新兴起的土工新材料和新技术,在设计和工程实际中还存在着许多急待解决的问题,着重对各种典型状态和典型环境下的土工布充砂袋的变形、应力和土工布充砂袋堆的稳定性研究进展进行综述,最后提出进一步研究的思路。 相似文献
76.
77.
The floating oil storage system has been proposed as a new facility for Strategic Petroleum Reserve (SPR) in China. Mooring is one of the key technologies to ensure the safety, reliability, and performance of the oil storage system. This paper describes the concept, analysis, design and reliability of the mooring system. For mooring system design of these oil vessels, analysis is essential of the behavior of the vessel in connection with mooring facilities of nonlinear resilience. A nonlinear mathematical model for analyzing a moored vessel is established and solved. Some results of numerical simulations are presented. Assessment of the safety regarding the mooring system in terms of failure probability is carried out. Another simulation model for calculating the failure probability of the mooring system is proposed. The design parameters that have an influence on the characteristics of the failure probability have been identified. The simulation results show that the mooring system has an annual reliab 相似文献
78.
Ping Chang 《Journal of Oceanography》1993,49(5):477-489
The effects of short waves on the propagration of velocity discontinuity along the interface of two uniform potential vorticity, zones on anf-plane is examined. It is shown, using a multiple scale analysis, that the dispersion introduced by the short waves can balance the nonlinear steepening effects predicted by the semigeostrophic theory. The time evolution of a shear disturbance along the front is governed by a Korteweg-de Vries equation. Numerical solutions of the solitary waves along the front are presented. 相似文献
79.
80.