全文获取类型
收费全文 | 21576篇 |
免费 | 2701篇 |
国内免费 | 3212篇 |
专业分类
测绘学 | 5132篇 |
大气科学 | 2589篇 |
地球物理 | 3178篇 |
地质学 | 8090篇 |
海洋学 | 2929篇 |
天文学 | 432篇 |
综合类 | 1937篇 |
自然地理 | 3202篇 |
出版年
2024年 | 71篇 |
2023年 | 223篇 |
2022年 | 467篇 |
2021年 | 627篇 |
2020年 | 692篇 |
2019年 | 769篇 |
2018年 | 573篇 |
2017年 | 891篇 |
2016年 | 785篇 |
2015年 | 943篇 |
2014年 | 1149篇 |
2013年 | 1262篇 |
2012年 | 1341篇 |
2011年 | 1435篇 |
2010年 | 1191篇 |
2009年 | 1242篇 |
2008年 | 1318篇 |
2007年 | 1530篇 |
2006年 | 1440篇 |
2005年 | 1341篇 |
2004年 | 1212篇 |
2003年 | 1006篇 |
2002年 | 1000篇 |
2001年 | 778篇 |
2000年 | 700篇 |
1999年 | 608篇 |
1998年 | 540篇 |
1997年 | 451篇 |
1996年 | 375篇 |
1995年 | 336篇 |
1994年 | 309篇 |
1993年 | 216篇 |
1992年 | 165篇 |
1991年 | 129篇 |
1990年 | 103篇 |
1989年 | 93篇 |
1988年 | 58篇 |
1987年 | 48篇 |
1986年 | 23篇 |
1985年 | 18篇 |
1984年 | 13篇 |
1983年 | 3篇 |
1982年 | 4篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1979年 | 3篇 |
1978年 | 1篇 |
1971年 | 1篇 |
1954年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
92.
Combining indicator trends to assess ongoing changes in exploited fish communities: diagnostic of communities off the coasts of France 总被引:1,自引:1,他引:1
93.
The accurate prediction of extreme excursion and mooring force of floating offshore structures due to multi-variete environmental conditions which requires the joint probability analysis of environmental conditions for the worst case situation is still impractical as the processing of large amount of met-ocean data is required. On the other hand, the simplified multiple design criteria (e.g. the N-year wave with associated winds and currents) recommended by API known as traditional method does lead neither to the N-year platform response nor to the N-year mooring force. Therefore, in order to reduce the level of conservatism as well as uncertainties involved in the traditional method the response-based method can be used as a reliable alternative approach. In this paper this method is described. In order to perform the calculations faster using large databases of sea states, Artificial Neural Networks (ANN) is designed and employed. In the paper the response-based method is applied to a 200,000 tdw FPSO and the results are discussed. 相似文献
94.
95.
REEdistributioninwater-sedimentinterfacesystematdeepoceanfloor¥ZhangLijie;LiuJihuaandYaoDe(ReceivedFebruary1,1994;acceptedMay... 相似文献
96.
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
97.
98.
INTRODUCTIONTheDenglouCape ,inthesouthwestoftheLeizhouPeninsula ,isatthenorthmarginoftropicalzone .SeveralresearchesandcartographiesoftheregionalgeomorphologyandQuater narygeology ,whichwerecarriedoutinthepast,allincludethisarea (MGL ,SCSIO ,CAS ,1 978;GPCSGRCZT… 相似文献
99.
100.
研究了连续变量函数的全局最优化问题 ,给出了动态隧道方法。该动态隧道方法由局部搜索和动态隧道 2个阶段构成。在局部搜索阶段用了动态系统方法。对全局最优化问题的实例进行了数值实验 ,数值结果表明了该方法的稳健性和有效性。 相似文献