全文获取类型
收费全文 | 7443篇 |
免费 | 258篇 |
国内免费 | 99篇 |
专业分类
测绘学 | 167篇 |
大气科学 | 615篇 |
地球物理 | 1653篇 |
地质学 | 2576篇 |
海洋学 | 686篇 |
天文学 | 1320篇 |
综合类 | 24篇 |
自然地理 | 759篇 |
出版年
2021年 | 85篇 |
2020年 | 100篇 |
2019年 | 111篇 |
2018年 | 158篇 |
2017年 | 159篇 |
2016年 | 186篇 |
2015年 | 150篇 |
2014年 | 176篇 |
2013年 | 391篇 |
2012年 | 236篇 |
2011年 | 334篇 |
2010年 | 313篇 |
2009年 | 348篇 |
2008年 | 321篇 |
2007年 | 303篇 |
2006年 | 311篇 |
2005年 | 238篇 |
2004年 | 265篇 |
2003年 | 220篇 |
2002年 | 219篇 |
2001年 | 167篇 |
2000年 | 141篇 |
1999年 | 137篇 |
1998年 | 131篇 |
1997年 | 99篇 |
1996年 | 99篇 |
1995年 | 113篇 |
1994年 | 99篇 |
1993年 | 78篇 |
1992年 | 101篇 |
1991年 | 76篇 |
1990年 | 100篇 |
1989年 | 94篇 |
1988年 | 78篇 |
1987年 | 112篇 |
1986年 | 81篇 |
1985年 | 100篇 |
1984年 | 138篇 |
1983年 | 114篇 |
1982年 | 104篇 |
1981年 | 108篇 |
1980年 | 94篇 |
1979年 | 102篇 |
1978年 | 75篇 |
1977年 | 91篇 |
1976年 | 74篇 |
1975年 | 73篇 |
1974年 | 60篇 |
1973年 | 65篇 |
1972年 | 36篇 |
排序方式: 共有7800条查询结果,搜索用时 15 毫秒
81.
82.
83.
Eric Wolanski David Williams Simon Spagnol Hubert Chanson 《Estuarine, Coastal and Shelf Science》2004,60(4):629-636
Measurements in the macro-tidal Daly Estuary show that the presence of an undular tidal bore contributed negligibly to the dissipation of tidal energy. No recirculation bubble was observed between a trough and the following wave crest in the lee waves following the undular bore. This differs to stationary undular bores in laboratory experiments at larger Froude numbers where a recirculation bubble exists. Secondary motions and the turbulence generated by the undular bore had no measurable influence on the sediment transport. This situation contrasts with the intense sediment resuspension observed in breaking tidal bores. The tidally averaged sediment budget in the Daly Estuary was controlled by the asymmetry of tidal currents. The undular bore may widen the river by breaking along the banks that it undercuts, leading to bank slippage. A patch of river-wide macro-turbulence of 3-min duration occurred about 20 min after the passage of the bore during accelerating tidal currents. 相似文献
84.
G. Randy Cutter Jr Robert J. Diaz John Lee 《Deep Sea Research Part II: Topical Studies in Oceanography》1994,41(4-6)
The recent benthic meiofaunal foraminiferal assemblage from the continental slope (590-2 003 m) off Cape Hatteras, North Carolina exhibits high species richness and evenness, moderate diversity values, and lacks numerically dominant species. The preserved planktic assemblage has relatively low species richness, high evenness, low diversity, and a few numerically dominant species. Approximately 9% of the benthic species are those that typically live within continental shelf depth ranges. The benthic assemblage abundances and diversities do not follow depth patterns or geophysical characteristics. No biogeographic boundary can be described within the study area for meiofaunal foraminifera. Oxygen limitation does not appear to be a factor affecting the benthos of the North Carolina continental slope based upon the community structure of the benthic foraminifera, if total assemblage is assumed to reflect the recently living community. The high carbonate content of sediments in the area may be explained by foraminiferal tests. Within the study area, the foraminiferal assemblages are uniform, and probably reflect relative consistency of primary environmental variables as well as dynamic downslope transport and high influx of material from the water column in the vicinity where the Gulf Stream and the Western Boundary Undercurrent cross. 相似文献
85.
86.
87.
88.
A giant three-stage submarine slide off Norway 总被引:8,自引:0,他引:8
Tom Bugge Stein Befring Robert H. Belderson Tor Eidvin Eystein Jansen Neil H. Kenyon Hans Holtedahl Hans Petter Sejrup 《Geo-Marine Letters》1987,7(4):191-198
One of the largest submarine slides known, The Storegga Slide, is located on the Norwegian continental margin. The slide is up to 450 m thick and has a total volume of about 5,600 km3. The headwall of the slide scar is 290 km long and the total run-out distance is about 800 km. The slide involved sediments of Quaternary to Early Tertiary age and occurred in three stages. Earthquakes combined with decomposition of gas hydrates are believed to be the main triggering agents for the slides. The first slide event is tentatively dated to be about 30,000 to 50,000 years B.P. and the two last major events are dated to be at 6,000 to 8,000 years B.P. 相似文献
89.
Christopher L. Dupont James. W. Moffett Robert R. Bidigare Beth A. Ahner 《Deep Sea Research Part I: Oceanographic Research Papers》2006,53(12):1961-1974
Dissolved and particulate concentrations of the biogenic thiols cysteine (Cys), arginine–cysteine (Arg–Cys), glutamine–cysteine (Gln–Cys), γ-glutamate–cysteine (γ-Glu–Cys) and glutathione (GSH) were measured in the subartic Pacific Ocean in the summer of 2003 using high performance liquid chromatography (HPLC) with precolumn derivatization as reported in previous work. In this study, a preconcentration protocol for the derivatized thiols was utilized to extend detection limits of dissolved thiols to picomolar levels. The measured concentrations of particulate and dissolved thiols were uncoupled, with distinctive depth profiles and large differences in the particulate to dissolved ratios between individual compounds. Glutathione was the most abundant particulate thiol whereas the most abundant dissolved thiol was γ-Glu–Cys, with concentrations as high as 15 nM. Given the relatively small pool of intracellular γ-Glu–Cys and the very low dissolved concentrations of GSH, we hypothesize that glutathione released from cells is rapidly converted to the potentially degradation resistant γ-Glu–Cys outside the cell. The relatively high concentrations of other dissolved thiols compared to particulate concentrations implies both biological exudation and slow degradation rates. Some thiols appear to vary with changes in nutrient availability but this effect is difficult to decouple from changes in community structure inferred from pigment analyses. Dissolved thiol concentrations also exceed typical metal concentrations in the subartic Pacific, supporting previous arguments that they may be important in metal speciation. 相似文献
90.