全文获取类型
收费全文 | 12422篇 |
免费 | 1117篇 |
国内免费 | 1348篇 |
专业分类
测绘学 | 390篇 |
大气科学 | 1703篇 |
地球物理 | 2985篇 |
地质学 | 5130篇 |
海洋学 | 1061篇 |
天文学 | 2098篇 |
综合类 | 503篇 |
自然地理 | 1017篇 |
出版年
2023年 | 119篇 |
2022年 | 261篇 |
2021年 | 318篇 |
2020年 | 270篇 |
2019年 | 314篇 |
2018年 | 507篇 |
2017年 | 448篇 |
2016年 | 544篇 |
2015年 | 386篇 |
2014年 | 528篇 |
2013年 | 677篇 |
2012年 | 517篇 |
2011年 | 675篇 |
2010年 | 560篇 |
2009年 | 730篇 |
2008年 | 596篇 |
2007年 | 562篇 |
2006年 | 498篇 |
2005年 | 480篇 |
2004年 | 426篇 |
2003年 | 383篇 |
2002年 | 373篇 |
2001年 | 342篇 |
2000年 | 363篇 |
1999年 | 417篇 |
1998年 | 345篇 |
1997年 | 345篇 |
1996年 | 322篇 |
1995年 | 288篇 |
1994年 | 219篇 |
1993年 | 216篇 |
1992年 | 158篇 |
1991年 | 144篇 |
1990年 | 106篇 |
1989年 | 136篇 |
1988年 | 102篇 |
1987年 | 125篇 |
1986年 | 79篇 |
1985年 | 77篇 |
1984年 | 85篇 |
1983年 | 77篇 |
1982年 | 84篇 |
1981年 | 76篇 |
1980年 | 60篇 |
1979年 | 54篇 |
1977年 | 50篇 |
1976年 | 48篇 |
1975年 | 37篇 |
1974年 | 32篇 |
1973年 | 41篇 |
排序方式: 共有10000条查询结果,搜索用时 312 毫秒
141.
Observations of the countercurrent on the inshore side of the Kuroshio northeast of Taiwan 总被引:4,自引:0,他引:4
Intensive current measurements in the area northeast of Taiwan indicate subsurface, southwestward flow existed between the inshore edge of the Kuroshio and the East China Sea continental slope. At 70 km away from Taiwan, this countercurrent has a mean speed about 30 cm s–1 at mid-depth. Closer to Taiwan, the flow turns along with the topography, and subjects to sidewall and bottom friction. Both the magnitude and the vertical shear of this countercurrent are comparable with that inferred from hydrographic survey. The wind field features short-period (a few days) fluctuations associated with the cold front passages, however, this is not reflected on the current records. It appears that the countercurrent is fairly steady. Together with similar reversing flow found at places much further to the north, the overall pattern seems to be a general quasi-steady feature along most part of the shelf edge of the East China Sea. 相似文献
142.
刍论大连湾底质地化环境 总被引:6,自引:0,他引:6
本文根据1987年的调查资料,总结阐述了大连湾底质地化环境诸要素的分布规律及其特征,运用相关分析法,通过多元回归计算求得了诸要素之间的关系。经过综合因素分析,得出了大连湾氧化还原环境分区、还原环境的成因及发展趋势。 相似文献
143.
Two different and physically separated chemosynthetic communities of bacteria are responsible for the formation of the Beeri native sulfur deposit hosted in a Late Quaternary sandstone on the southern coastal plain of Israel. The enriched concentrations are distributed over an area of about 1 km2, within a zone 2–3 m thick at 1–13 m below surface. Two hundred fifty meters below the sulfur deposit, sulfur-reducing bacteria, thriving on methane generated in Neogene marls, reduced the Messinian gypsum to generate hydrogen sulfide, which subaqueously vented together with methane into the siliciclastic Quaternary sequence. Another, different chemosynthetic community ofBeggiatoa-like and unidentified bacteria oxidized the hydrogen sulfide into native sulfur and secondary gypsum, alunite, and iron sulfates. The coupled chemical and bacterial processes attributed to the formation of the sulfur deposit at Beeri are strikingly similar to the processes occurring today in the context of submarine hydrocarbon vents associated with the salt diapirs in the Gulf of Mexico. 相似文献
144.
145.
Ma Liming 《海洋学报(英文版)》1997,16(2):201-214
On the basis of the data of the partial pressure of CO2 (PCO2)and the concentration of the total dissolved CO2(TCO2) in surface water during the expeditions in Nov.-Dec. 1991, the world ocean circulation experiment (WOCE) and Oct. 1992-Mar. 1993, the tropical ocean-global atmosphere coupled ocean-atmosphere response experiment (TOGA COARE) in the western tropical Pacific and of the comparison with data from 1986 to 1990 TOGA expeditions and that from Japan Meteorological Agency, the response of CO2 in surface water to ENSO event is proved. The CO2 signals indicated that the air-sea system in the western and central tropical Pacific from 1991 to 1993, except for a short period in autumn of 1992, was in a strong state of ENSO.
The change of CO2 in the floating stations near 2°S, 155°E from Nov. 1992 to Mar. 1993 reflected the change of currents, water mass and its thermal and salt content during the forming and developing of ENSO. 相似文献
The change of CO2 in the floating stations near 2°S, 155°E from Nov. 1992 to Mar. 1993 reflected the change of currents, water mass and its thermal and salt content during the forming and developing of ENSO. 相似文献
146.
Based on the ray theory and Longuet-Higgins’s linear model of sea waves, the joint distribution of wave envelope and apparent wave number vector is established. From the joint distribution, we define a new concept, namely the outer wave number spectrum, to describe the outer characteristics of ocean waves. The analytical form of the outer wave number spectrum, the probability distributions of the apparent wave number vector and its components are then derived. The outer wave number spectrum is compared with the inner wave number spectrum for the average status of wind-wave development corresponding to a peakness factor P = 3. Discussions on the similarity and difference between the outer wave number spectrum and inner one are also presented in the paper. 相似文献
147.
In this study, the dynamic stresses within the seabed induced by non-linear progressive waves were explored through a series of hydraulic model tests on a movable bed within a wave flume. By comparing Stokes’ 2nd-order wave theory with the theory of wave-induced dynamic stresses within the seabed as proposed by Yamamoto et al. [1978. On the response of a poro-elastic bed to water waves. Journal of Fluid Mechanics 87 (1), 193–206.] and Hsu and Jeng [1994. Wane-induced soil response in an unsaturated anisotropic seabed of finite thickness. International Journal for Numerical and Analytical Methods in Geomechanics 18, 785–807], the experimental results show that the pressure on the seabed surface, the pore water pressure within the seabed as well as the vertical and the horizontal stresses are all smaller than their theoretical values. If we were to obtain the characteristics of seabed soil, the analytical solution of Hsu and Jeng [1994. Wane-induced soil response in an unsaturated anisotropic seabed of finite thickness. International Journal for Numerical and Analytical Methods in Geomechanics 18, 785–807] might agree to the simulation of the wave-induced effective stresses and shear stress in the sandy seabed. A different phase shift exists among all the three soil stresses. Their influences on the three dynamic stresses within seabed soil are important for seabed stability, and can be used in the verification of numerical models. In the whole, the non-linear progressive waves and the naturally deposited seabed are found to have a strong interaction, and the behavior of the induced dynamic stresses within the seabed is very complicated, and should be investigated integrally. 相似文献
148.
Effects of the presence of a circumpolar region on buoyancy-driven circulation are investigated by using an idealized numerical ocean model. Comparison of circulation and meridional density (heat) transport is made between a closed ocean and an ocean with a cyclic gap near its southern boundary. The presence of the circumpolar region leads to disconnection of the meridional overturning across the circumpolar region. And the circumpolar eastward flow reaches the bottom of the ocean. It is essential for this that the pycnocline is deeper than the bottom of the gap. Since the amount of the mass transported northward must return southward at the levels deeper than the bottom of the cyclic gap, the weak stratification, hence weak vertical geostrophic shear, at the deeper levels leads to inactive communication across the circumpolar region. Meridional heat transport across the circumpolar region is made mainly by horizontal diffusion for the ocean with the cyclic gap, while the contribution of the advection is dominant for the closed ocean. Sensitivity of meridional heat transport to change in horizontal diffusivity is studied. The meridional heat transport for the ocean with the cyclic gap is more sensitive than for the closed ocean. The change in heat transport occurs not only in the circumpolar region but also in the rest of the ocean. It is suggested that subgrid scale phenomena, especially mesoscale eddies, in the circumpolar region controls the whole ocean to a great extent. 相似文献
149.
J. -M. Auzende L. Géli H. Ondréas J. -Y. Collot Y. Lafoy J. -P. Eissen E. Gracia M. B. Larue C. Olisukulu D. Tolia N. Biliki 《Geo-Marine Letters》1994,14(4):232-237
During the SOPACMAPS 2 crusie carried out by IFREMER (Institut Français de Recherche pour l'Exploitation de la Mer) and ORSTOM (Institut Français de Recherche Scientifique pour le dévelopement en Coopération) on theR/V L'Atalante, in the Central Solomon Arc area, multibeam bathymetric and imagery data and single-channel seismic reflection profiles were collected from an area of about 3500 km2, to evaluate regional tectonics. Structural data geophysical profiles interpretation provide evidence for left-lateral transtensional tectonics on the southern edge of the Central Solomon Trough. This transtensional deformation is represented by faulting, block tilting, and rhombohedral deformation. The regional geology and the analysis of the sedimentary cover allow us to demonstrate that this tectonic occurred in two different phases during Oligocene to Miocene and Pliocene to Pleistocene times. 相似文献
150.
K. S. Jeong J. K. Kang K. Y. Lee H. S. Jung S. B. Chi S. J. Ahn 《Geo-Marine Letters》1996,16(2):123-131
In the northwestern margin of the Clarion and Clipperton fracture zones, manganese nodules are latitudinally variable in character, resulting from the progressive (re)generation of nodules since the Oligocene as the Pacific Plate migrates northwestward beneath the equatorial production zone. Complemented by the surface water productivity, bottom current activities have concentrated nodules in the Oligocene to Miocene siliceous clay. Resedimentation processes on nodules form three types of nodules with concentric structures and 10 Å-manganaterich bottoms, by periodically causing the diagenetic growth of nodules within the topmost sediment layer. 相似文献