全文获取类型
收费全文 | 42731篇 |
免费 | 768篇 |
国内免费 | 342篇 |
专业分类
测绘学 | 1009篇 |
大气科学 | 3061篇 |
地球物理 | 8304篇 |
地质学 | 14700篇 |
海洋学 | 3954篇 |
天文学 | 10045篇 |
综合类 | 82篇 |
自然地理 | 2686篇 |
出版年
2021年 | 422篇 |
2020年 | 425篇 |
2019年 | 477篇 |
2018年 | 979篇 |
2017年 | 888篇 |
2016年 | 1123篇 |
2015年 | 644篇 |
2014年 | 1045篇 |
2013年 | 2150篇 |
2012年 | 1173篇 |
2011年 | 1678篇 |
2010年 | 1533篇 |
2009年 | 2054篇 |
2008年 | 1709篇 |
2007年 | 1784篇 |
2006年 | 1644篇 |
2005年 | 1344篇 |
2004年 | 1316篇 |
2003年 | 1276篇 |
2002年 | 1244篇 |
2001年 | 1081篇 |
2000年 | 1014篇 |
1999年 | 827篇 |
1998年 | 838篇 |
1997年 | 854篇 |
1996年 | 685篇 |
1995年 | 675篇 |
1994年 | 629篇 |
1993年 | 588篇 |
1992年 | 546篇 |
1991年 | 508篇 |
1990年 | 519篇 |
1989年 | 505篇 |
1988年 | 482篇 |
1987年 | 573篇 |
1986年 | 505篇 |
1985年 | 624篇 |
1984年 | 678篇 |
1983年 | 615篇 |
1982年 | 559篇 |
1981年 | 600篇 |
1980年 | 494篇 |
1979年 | 479篇 |
1978年 | 442篇 |
1977年 | 448篇 |
1976年 | 398篇 |
1975年 | 386篇 |
1974年 | 391篇 |
1973年 | 393篇 |
1971年 | 231篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
431.
The Solomon Sea Plate was widely developed during late Oligocene, separating the proto-West Melanesian Arc from the proto-Trobriand Arc. Spreading in the Bismarck Sea and in the Woodlark Basin resulted from interaction between the Pacific and Australian Plates, specifically from the collision of the proto-West Melanesian Arc with north New Guinea, which occurred after arc reversal. This model explains the extensive Miocene, Pliocene, and Quaternary volcanism of the Papua New Guinea mainland as it related to southward subduction of the Trobriand Trough. Our interpreted plate motions are concordant with the geological evidence onshore and also with complex tectonic features in the Solomon Sea Basin Region. 相似文献
432.
433.
434.
435.
436.
437.
438.
R.E. Rossi P.M. Belles P.A.A. Laura S. La Malfa L. Ercoli D. Pasqua 《Ocean Engineering》1996,23(3):271-276
A numerical solution is obtained for the title problem by means of the popular finite element method. An experimental investigation of the problem is also presented for plates of square planform. The agreement between theoretical and experimental values is very good in the case of the fundamental frequency, and reasonably good when the second and third normal modes of transverse vibration are considered. It is concluded that beneficial effects are obtained in the sense that one generates a lighter structural element with higher fundamental frequency of transverse vibration. Hence, dynamic stiffening is achieved. 相似文献
439.
Based on the MEGAPOLYGON data, it is shown that the large-scale elements of the thermohaline structure and the fields of currents in the baroclinic layer (down to 1200 m) are well coordinated. The circulation has a two-layer structure with a transitory layer at a depth of 1200 m. The topography of the isopycnic surface of the layer's core is formed under the influence of small-scale and mesoscale processes which realize the trans-frontal exchange.Translated by Mikhail M. Trufanov. 相似文献
440.
Hance D Smith 《Marine Policy》1995,19(6)
The environmental management of shipping requires systematic consideration of the geography of shipping routes, ship types and cargoes, and environments which can form the basis of a classificatory approach to Environmental Impact Assessment (EIA). Beyond this, effective environmental management depends in the first instance upon sound information management including monitoring of the environment, surveillance of shipping and information technology, followed by information assessment including, in particular, risk and environmental impact. The general management dimension includes co-ordination of technical management and organisational aspects related to shipping. It is suggested that effective environmental management of shipping may depend upon a regionalisation of the marine environment for EIA purposes akin to that found in the loadline rules, together with rationalisation of the increasing number of special areas in existence or proposed for this purpose. EIA will have to become an integral part of the overall management system in the shipping industry. 相似文献