全文获取类型
收费全文 | 56557篇 |
免费 | 724篇 |
国内免费 | 486篇 |
专业分类
测绘学 | 1217篇 |
大气科学 | 3095篇 |
地球物理 | 10757篇 |
地质学 | 21255篇 |
海洋学 | 5348篇 |
天文学 | 13830篇 |
综合类 | 149篇 |
自然地理 | 2116篇 |
出版年
2022年 | 599篇 |
2021年 | 893篇 |
2020年 | 1013篇 |
2019年 | 1077篇 |
2018年 | 2184篇 |
2017年 | 2022篇 |
2016年 | 2280篇 |
2015年 | 976篇 |
2014年 | 2021篇 |
2013年 | 3130篇 |
2012年 | 2256篇 |
2011年 | 2765篇 |
2010年 | 2523篇 |
2009年 | 2968篇 |
2008年 | 2617篇 |
2007年 | 2798篇 |
2006年 | 2538篇 |
2005年 | 1469篇 |
2004年 | 1364篇 |
2003年 | 1290篇 |
2002年 | 1256篇 |
2001年 | 1209篇 |
2000年 | 1069篇 |
1999年 | 802篇 |
1998年 | 844篇 |
1997年 | 836篇 |
1996年 | 666篇 |
1995年 | 653篇 |
1994年 | 655篇 |
1993年 | 527篇 |
1992年 | 522篇 |
1991年 | 530篇 |
1990年 | 602篇 |
1989年 | 455篇 |
1988年 | 443篇 |
1987年 | 497篇 |
1986年 | 374篇 |
1985年 | 569篇 |
1984年 | 547篇 |
1983年 | 506篇 |
1982年 | 519篇 |
1981年 | 424篇 |
1980年 | 464篇 |
1979年 | 375篇 |
1978年 | 425篇 |
1977年 | 341篇 |
1976年 | 323篇 |
1975年 | 336篇 |
1974年 | 314篇 |
1973年 | 341篇 |
排序方式: 共有10000条查询结果,搜索用时 906 毫秒
671.
672.
673.
Effect of ice cover on oscillations of fluid in a closed basin 总被引:1,自引:0,他引:1
I. V. Sturova 《Izvestiya Atmospheric and Oceanic Physics》2007,43(1):112-118
Within the framework of the linear theory of long waves, the problem of the effect of ice cover on seiche oscillations of fluid in a two-dimensional constant-depth basin is solved. The eigenfrequencies and eigenfunctions of seiche oscillations are obtained for different boundary conditions at ice edges: rigid coupling and free edges. The forced oscillations of fluid and ice under the action of a moving disturbance of atmospheric pressure are investigated. The change in the stress of ice bending is considered and it is shown that the coast ice can be broken. 相似文献
674.
675.
The analysis is performed on the basis of comparison of the hydrological characteristics of prestrait regions of the Sea of
Marmara. It is shown that, in summer, the Black-Sea waters are weakly mixed with the Mediterranean waters and the levels of
salinity in the prestrait regions differ by 0.6–0.9‰. In winter, the indicated difference increases and the level of salinity
near the entrance of Dardanelles reaches 29‰ and exceeds the level observed near the entrance of Bosporus by 5.5‰. In the
analyzed regions, we observe local temperature maxima and minima near the interface of two water masses. This is explained
by the presence of strong seasonal variations of temperature for the Black-Sea waters and their absence for the Mediterranean
waters. The physical mechanisms responsible for the seasonal variations of the intensity of transformations of the Black-Sea
waters are discussed.
__________
Translated from Morskoi Gidrofizicheskii Zhurnal, No. 2, pp. 49–55, March–April, 2007. 相似文献
676.
The sandy quartzose parts of the Utsira Formation, the Middle Miocene to mid Pliocene Utsira Sand, extends north–south along the Viking Graben near the UK/Norwegian median line for more than 450 km and 75–130 km east–west. The Utsira Sand is located in basin-restricted seismic depocentres, east of and below prograding sandy units from the Shetland Platform area with Hutton Sands. The Utsira Sand reaches thicknesses up to ca. 300 m in the southern depocentre and 200 m in the two northern depocentres with sedimentation rates up to 2–4 cm/ka. Succeeding Plio–Pleistocene is divided into seismic units, including Base Upper Pliocene, Shale Drape, Prograding Complex and Pleistocene. The units mainly consist of clay, but locally minor sands occur, especially at toes of prograding clinoforms (bottom-set sands) and in the Pleistocene parts, and the total thickness covering the Utsira Sand is in most places more than 800 m, but thins towards the margins. 相似文献
677.
Changes in climatic parameters and in temperature and precipitation extremes in northern Eurasia in the late 20th century are analyzed. A spatial distribution of temperature and precipitation anomalies and of a set of indices of climate extremes is presented. Changes in climate extremes show a tendency toward a milder climate, mainly in winter. At the same time, the frost-free period has substantially decreased in the eastern, northern, and central parts of European Russia. In some regions during summer, there is an increase in the frequency of extreme events such as heavy rains, droughts, and sharp cooling. It is shown that the geographic pattern of present-day climate anomalies is linked to variations in the large-scale atmospheric circulation. The main mechanism of the current warming in northern Eurasia is a winter intensification of zonal flow linked to the increased frequency of positive anomalies of the North Atlantic Oscillation index. 相似文献
678.
Parameter sensitivity of three Kalman filter schemes for assimilation of water levels in shelf sea models 总被引:2,自引:0,他引:2
In applications of data assimilation algorithms, a number of poorly known assimilation parameters usually need to be specified. Hence, the documented success of data assimilation methodologies must rely on a moderate sensitivity to these parameters. This contribution presents a parameter sensitivity study of three well known Kalman filter approaches for the assimilation of water levels in a three dimensional hydrodynamic modelling system. The filters considered are the ensemble Kalman filter (EnKF), the reduced rank square root Kalman filter (RRSQRT) and the steady Kalman filter. A sensitivity analysis of key parameters in the schemes is undertaken for a setup in an idealised bay. The sensitivity of the resulting root mean square error (RMSE) is shown to be low to moderate. Hence the schemes are robust within an acceptable range and their application even with misspecified parameters is to be encouraged in this perspective. However, the predicted uncertainty of the assimilation results are sensitive to the parameters and hence must be applied with care. The sensitivity study further demonstrates the effectiveness of the steady Kalman filter in the given system as well as the great impact of assimilating even very few measurements. 相似文献
679.
D. S. Drozdov F. M. Rivkin V. Rachold G. V. Ananjeva-Malkova N. V. Ivanova I. V. Chehina M. M. Koreisha Yu. V. Korostelev E. S. Melnikov 《Geo-Marine Letters》2005,25(2-3):81-88
A set of digital maps including geology, Quaternary sediments, landscapes, engineering-geological, vegetation, geocryological and the series of regional sources have been selected to characterize the Russian Arctic coast. Based on this data, new maps of engineering geocryological zoning and zoning of the coast with respect to the intensity of exogenous geological processes and risk of technogenic impacts have been generated at the scales of 1:4,000,000–1:8,000,000. These maps are a tool to assess the impact of industry on the Arctic coast of the country. 相似文献
680.
Hydrodynamic implications of large offshore mussel farms 总被引:2,自引:0,他引:2
Plew D.R. Stevens C.L. Spigel R.H. Hartstein N.D. 《Oceanic Engineering, IEEE Journal of》2005,30(1):95-108