全文获取类型
收费全文 | 66402篇 |
免费 | 1181篇 |
国内免费 | 592篇 |
专业分类
测绘学 | 1919篇 |
大气科学 | 4663篇 |
地球物理 | 13090篇 |
地质学 | 23952篇 |
海洋学 | 5671篇 |
天文学 | 15107篇 |
综合类 | 224篇 |
自然地理 | 3549篇 |
出版年
2021年 | 669篇 |
2020年 | 722篇 |
2019年 | 839篇 |
2018年 | 1693篇 |
2017年 | 1661篇 |
2016年 | 1957篇 |
2015年 | 1112篇 |
2014年 | 1865篇 |
2013年 | 3321篇 |
2012年 | 2054篇 |
2011年 | 2710篇 |
2010年 | 2356篇 |
2009年 | 2968篇 |
2008年 | 2639篇 |
2007年 | 2641篇 |
2006年 | 2548篇 |
2005年 | 1915篇 |
2004年 | 1833篇 |
2003年 | 1852篇 |
2002年 | 1736篇 |
2001年 | 1527篇 |
2000年 | 1428篇 |
1999年 | 1296篇 |
1998年 | 1239篇 |
1997年 | 1261篇 |
1996年 | 1086篇 |
1995年 | 1056篇 |
1994年 | 939篇 |
1993年 | 843篇 |
1992年 | 757篇 |
1991年 | 802篇 |
1990年 | 807篇 |
1989年 | 740篇 |
1988年 | 691篇 |
1987年 | 793篇 |
1986年 | 738篇 |
1985年 | 913篇 |
1984年 | 981篇 |
1983年 | 958篇 |
1982年 | 898篇 |
1981年 | 775篇 |
1980年 | 760篇 |
1979年 | 685篇 |
1978年 | 656篇 |
1977年 | 651篇 |
1976年 | 580篇 |
1975年 | 582篇 |
1974年 | 589篇 |
1973年 | 643篇 |
1972年 | 415篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
931.
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
932.
933.
934.
To improve resolution of seismic-reflection profiles in continental slope water depths of 900 to 1500 m, a single hydrophone
was towed about 150 m off the bottom to receive reflected signals from a surface-towed sparker sound source. That deep-towed
hydrophone data show that valleys which appear V-shaped in records from a surface-towed hydrophone are flat-bottomed, and
that subbottom reflections from an erosional unconformity can be much better resolved. The data produced by this technique
are very hepful when used in conjunction with records from conventional surface-towed seismic-profiling equipment. 相似文献
935.
936.
937.
Abandonment and recovery solution of submarine pipelines 总被引:1,自引:0,他引:1
T.K. Datta 《Applied Ocean Research》1982,4(4):247-252
938.
K. T. Pickering 《Geo-Marine Letters》1982,2(1-2):41-46
Deep-water siliciclastic systems are classified primarily on their shape as: submarine fans with well developed or poorly
developed morphology, slope drapes, for example, over relatively stable basin margins, fault-scarp aprons, canyons and large
channels, under-supplied sheet systems such as abyssal plains, non-fan ponded systems such as over-supplied perched basins,
and fan deltas. Collectively, or separately, these systems may form sedimentary basin fills that can be over or under-supplied
with respect to the sediment input although most systems will tend toward over-supply/overflow with time. Finally, the sum
total of the siliciclastic systems and basins can be used to define the tectonic milieux such as passive, strike-slip and
convergent margins. 相似文献
939.
Seismic noise induced by the seismic source during continuous profiling reduces the signal-to-noise ratio and hence the data quality. This noise is largely dependent on the shot interval. In this paper, the noise amplitude of refraction seismic records from a special experiment is analysed as a function of the shot interval. An empirical exponential relationship between mean peak noise amplitude and shot interval is deduced. By increasing the shot interval, the induced noise can be minimized on all successive records. This results in an improvement of the data, predominantly the signal-to-noise ratio. Because the seismic signal and the shot-induced noise have nearly the same spectra, the chance of improving the signal-to-noise ratio by stacking is significantly reduced. 相似文献
940.