全文获取类型
收费全文 | 77925篇 |
免费 | 767篇 |
国内免费 | 589篇 |
专业分类
测绘学 | 2152篇 |
大气科学 | 5005篇 |
地球物理 | 14568篇 |
地质学 | 30780篇 |
海洋学 | 6265篇 |
天文学 | 17261篇 |
综合类 | 351篇 |
自然地理 | 2899篇 |
出版年
2022年 | 602篇 |
2021年 | 891篇 |
2020年 | 937篇 |
2019年 | 1035篇 |
2018年 | 4214篇 |
2017年 | 3757篇 |
2016年 | 3430篇 |
2015年 | 1208篇 |
2014年 | 2190篇 |
2013年 | 3411篇 |
2012年 | 3071篇 |
2011年 | 4664篇 |
2010年 | 4084篇 |
2009年 | 4688篇 |
2008年 | 4003篇 |
2007年 | 4555篇 |
2006年 | 2741篇 |
2005年 | 1968篇 |
2004年 | 1805篇 |
2003年 | 1817篇 |
2002年 | 1698篇 |
2001年 | 1428篇 |
2000年 | 1308篇 |
1999年 | 1014篇 |
1998年 | 988篇 |
1997年 | 1022篇 |
1996年 | 850篇 |
1995年 | 829篇 |
1994年 | 786篇 |
1993年 | 651篇 |
1992年 | 629篇 |
1991年 | 650篇 |
1990年 | 693篇 |
1989年 | 607篇 |
1988年 | 576篇 |
1987年 | 651篇 |
1986年 | 521篇 |
1985年 | 705篇 |
1984年 | 739篇 |
1983年 | 725篇 |
1982年 | 669篇 |
1981年 | 576篇 |
1980年 | 607篇 |
1979年 | 493篇 |
1978年 | 521篇 |
1977年 | 474篇 |
1976年 | 417篇 |
1975年 | 415篇 |
1974年 | 430篇 |
1973年 | 488篇 |
排序方式: 共有10000条查询结果,搜索用时 109 毫秒
941.
Physical oceanography 总被引:2,自引:0,他引:2
942.
Existing methods for the determination of the various forms of iodine present in seawater are laborious or unwieldy in use. This paper describes modified forms of the iodate and total iodine methods described by Barkley and Thompson (1960), a spectrophotometric procedure for iodate determination derived from Johannesson's (1958) work, and an automatic method for total iodine determination. Procedures for iodate and total-iodine determination which are suitable for use aboard ship, are recommended. Both procedures for iodate determination returned a standard deviation close to 0.5 μg/l when several replicate samples of a seawater containing approximately 30 μg/l of iodate-iodine were analysed. The automatic method for total iodine determination yielded a standard deviation of 0.8 μg/l by the repeated analysis of a seawater containing a total of approximately 50 μg/l of iodine. Suitable methods for the filtration and storage of seawater are also described. 相似文献
943.
944.
945.
946.
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
947.
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
948.
Dorrik A. V. Stow 《Geo-Marine Letters》1985,5(1):17-23
There appears to be a continuum of processes affecting the transport and deposition of fine-grained sediments in the deep
sea. This results in a facies continuum within which we can recognize three broadly different facies groups: turbidites, contourites,
and pelagites/hemipelagites. Several distinct facies models can be defined for each group on the basis of their chief structural,
textural, and compositional attributes. 相似文献
949.
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
950.
The finite-elements technique is applied to study the effect of a basin’s geometry (bays, harbours) and location of the characteristics
of seiche oscillations in the basin and in the gulf proper. An increase of the length of the bay is shown to contribute to
the periods of natural oscillations and to cause their restructuring.
Translated by Vladimir A. Puchkin. 相似文献