全文获取类型
收费全文 | 68940篇 |
免费 | 958篇 |
国内免费 | 587篇 |
专业分类
测绘学 | 1613篇 |
大气科学 | 4829篇 |
地球物理 | 13802篇 |
地质学 | 26077篇 |
海洋学 | 5889篇 |
天文学 | 15135篇 |
综合类 | 179篇 |
自然地理 | 2961篇 |
出版年
2022年 | 562篇 |
2021年 | 886篇 |
2020年 | 959篇 |
2019年 | 1040篇 |
2018年 | 2229篇 |
2017年 | 2103篇 |
2016年 | 2444篇 |
2015年 | 1118篇 |
2014年 | 2188篇 |
2013年 | 3534篇 |
2012年 | 2361篇 |
2011年 | 2950篇 |
2010年 | 2738篇 |
2009年 | 3279篇 |
2008年 | 2853篇 |
2007年 | 2907篇 |
2006年 | 2784篇 |
2005年 | 1758篇 |
2004年 | 1620篇 |
2003年 | 1648篇 |
2002年 | 1617篇 |
2001年 | 1504篇 |
2000年 | 1411篇 |
1999年 | 1070篇 |
1998年 | 1048篇 |
1997年 | 1125篇 |
1996年 | 916篇 |
1995年 | 899篇 |
1994年 | 843篇 |
1993年 | 707篇 |
1992年 | 705篇 |
1991年 | 709篇 |
1990年 | 763篇 |
1989年 | 675篇 |
1988年 | 642篇 |
1987年 | 727篇 |
1986年 | 620篇 |
1985年 | 780篇 |
1984年 | 876篇 |
1983年 | 863篇 |
1982年 | 779篇 |
1981年 | 747篇 |
1980年 | 721篇 |
1979年 | 647篇 |
1978年 | 713篇 |
1977年 | 608篇 |
1976年 | 544篇 |
1975年 | 558篇 |
1974年 | 599篇 |
1973年 | 614篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
961.
962.
C.H.K. Williamson 《Applied Ocean Research》1985,7(3):124-127
The present brief paper is intended to show that the fluid forces on a small cylinder can be considerably magnified when it is in the flow field of a larger cylinder. Two cylinders of unequal diameter are oscillated in a tank of fluid, and the lift and in-line forces on the smaller cylinder are measured when the pair of cylinders is placed at various orientations and spacings. 相似文献
963.
The problem of monitoring of the mesoscale variability of hydrophysical fields in the shelf zone is considered. The usefulness of the data available in regional information centres is discussed. The possibility of monitoring the dynamics of the oceanic fields in the tropical Atlantic encompassing separate observation sites is demonstrated using the oceanographic databank of the scientific research centre (CERESCOR) in Conakry-Rogbane as an example. The results of assimilation of the hydrophysical survey data derived on the shelf in a telescopic model of the region are given.Translated by Mikhail M. Trufanov. 相似文献
964.
A series of transient tests were conducted to determine the seafloor coupling characteristics of a new ocean-bottom seismometer (OBS) developed for the United States Office of Naval Research (ONR). The OBS comprises a large recording package and a separate sensor package that is deployed from the recording package. In addition to the coupling characteristics of both the sensor and the recording packages, the seismic energy radiated from the main recording package as a result of motion of the recording package was measured. The observed vertical coupling resonances of both the recording package and the sensor package are in good agreement with those predicted by a simple model of soil-structure interaction. The most important result of this study is that significant energy is radiated from the recording package in response to horizontal motions of the recording package. When the sensor package is 1 m from the recording package, the amplitude of the recorded signal is similar to that recorded in the recording package. In the field, this effect will result in distortion of seismic signals and increased background noise recorded by the sensor package if the recording package is disturbed by seafloor currents or biological activity. The amplitude of this signal attenuates by approximately a factor of two as sensor/recorder separation is increased from 1 to 6 m, suggesting that an improved response can be achieved by increasing the separation between the recording package and the sensors. This effect is much less severe for vertical disturbances of the recording package. 相似文献
965.
The Three Kings Ridge has been described as a remnant arc or an east-facing arc on the western side of the South Fiji Basin
under which symmetric South Fiji Basin magnetic anomaly lineations have been lost. We find evidence of neither arc-trench
morphology on the eastern flank of the ridge nor collision tectonism within the adjacent South Fiji Basin that might have
obliterated it. We believe there is room for the missing magnetic lineations within the South Fiji Basin and we recognize
the distinctive island-arc morphology characteristic of a west-facing arc on the western flank of the Three Kings Ridge. Our
interpretation requires that arc volcanism postdated formation of much of the South Fiji Basin and that oceanic lithosphere
from the adjacent Norfolk Basin must have been subducted beneath the west-facing Three Kings Arc. 相似文献
966.
Dorrik A. V. Stow 《Geo-Marine Letters》1983,3(2-4):217-222
The Brae oilfield reservoir in the North Sea comprises Upper Jurassic resedimented conglomerates and sandstones interbedded with organic-rich silstone and mudstone thin-bedded turbidites. The system represents a series of small overlapping fans that form a thick (300 m) slope-apron accumulation of sediments deposited in a narrow (<10 km wide) belt along an active fault zone. The complex lateral and vertical distribution of facies was due mainly to variable tectonic activity, and partly also to sediment supply and sea-level changes. 相似文献
967.
Climatic effects on plankton and productivity on the Faroe Shelf 总被引:1,自引:0,他引:1
Hansen Bogi; Eliasen Solva K.; Gaard Eilif; Larsen Karin M.H. 《ICES Journal of Marine Science》2005,62(7):1224-1232
968.
969.
Quasi-biennial variations in vertical profiles of ozone, temperature, air pressure, and zonal and meridional wind velocities are analyzed from ozonesonde data obtained at the western European stations of Lindenberg, Hohenpeissenberg, and Payerne. The effect of quasi-biennial variations manifests itself variously in different variables and is nonuniform in altitude. The period of quasi-biennial variations is not constant, and the values of the mean period group mainly around 2 and 2.5 years. As in the North American region, the effects of quasi-biennial variations in different parameters of the stratosphere and troposphere over western Europe are due to a combination of the effects of the quasi-biennial oscillation (QBO) in the equatorial stratosphere, the El Niño-Southern Oscillation (ENSO), and the North Atlantic Oscillation (NAO). The observed 2.5-year variations in stratospheric ozone are related to the equatorial QBO to a larger extent in comparison with variations in other variables. It seems likely that a determining influence on variations in stratospheric wind and temperature is exerted by the ENSO. Variations in tropospheric and stratospheric parameters with a mean period of about 2 years are due to the ENSO and NAO effects. 相似文献
970.
V. R. Neralla 《Ocean Engineering》1987,14(2)
In order to obtain quick initial guidance on a first estimation of motion of the spilled oil, a simple manual procedure incorporating advection and spreading processes has been devised. This procedure involves the utilization of a nomogram based on simplified equations. Spill displacements throughout a given forecast period can be easily read from the nomogram. The technique is demonstrated with a real spill case. 相似文献