全文获取类型
收费全文 | 1950篇 |
免费 | 101篇 |
国内免费 | 21篇 |
专业分类
测绘学 | 84篇 |
大气科学 | 152篇 |
地球物理 | 718篇 |
地质学 | 685篇 |
海洋学 | 155篇 |
天文学 | 131篇 |
综合类 | 9篇 |
自然地理 | 138篇 |
出版年
2022年 | 12篇 |
2021年 | 22篇 |
2020年 | 49篇 |
2019年 | 34篇 |
2018年 | 61篇 |
2017年 | 51篇 |
2016年 | 83篇 |
2015年 | 72篇 |
2014年 | 69篇 |
2013年 | 115篇 |
2012年 | 92篇 |
2011年 | 118篇 |
2010年 | 104篇 |
2009年 | 126篇 |
2008年 | 102篇 |
2007年 | 71篇 |
2006年 | 68篇 |
2005年 | 45篇 |
2004年 | 42篇 |
2003年 | 52篇 |
2002年 | 31篇 |
2001年 | 51篇 |
2000年 | 31篇 |
1999年 | 36篇 |
1998年 | 30篇 |
1997年 | 30篇 |
1996年 | 23篇 |
1995年 | 19篇 |
1994年 | 17篇 |
1993年 | 12篇 |
1992年 | 18篇 |
1990年 | 14篇 |
1989年 | 14篇 |
1988年 | 19篇 |
1987年 | 12篇 |
1986年 | 21篇 |
1985年 | 22篇 |
1984年 | 19篇 |
1983年 | 26篇 |
1982年 | 21篇 |
1981年 | 18篇 |
1980年 | 15篇 |
1979年 | 18篇 |
1978年 | 13篇 |
1977年 | 14篇 |
1976年 | 13篇 |
1975年 | 17篇 |
1973年 | 14篇 |
1972年 | 10篇 |
1969年 | 9篇 |
排序方式: 共有2072条查询结果,搜索用时 312 毫秒
21.
Jan Kohlmeyer 《Marine Ecology》1984,5(4):329-378
Abstract. Marine Ascomycetes, Basidiomycetes and Deuteromycetes were collected in tropical and subtropical regions (Australia, Belize, Fiji, Hawaii, Marshall Islands, Mexico, New Zealand, Palau, Thailand), and the known range of distribution for these fungi was extended. Exclusively tropical are 27 taxa, 9 are probably restricted to the tropics also, and 11 are cosmopolitan. Distribution maps are given for 5 taxa. New species (4), varieties (3), and combinations (2) of Ascomycetes are proposed, and keys to the taxa of Halosarpheia and Lulworthia are presented. Most of the species are decomposers of mangrove parts or of detritus in sandy beaches. Nine new host plants were found. Marine Ascomycetes were discovered for the first time living in shells of foraminifera. 相似文献
22.
23.
Modest observations and numerical experiments were conducted to investigate circulation and brackish water dispersal in a
coastal lagoon southwest of Taiwan. The Chi-Ku Lagoon, partially shielded from the sea by a string of sandbar barriers with
two entrances among them, receives modest and episodic runoff from Chi-Ku Stream. Flood and ebb tidal streams entering and
leaving the two entrances are found to converge and diverge in a flow stagnation area inside the lagoon. Under weak wind conditions,
brackish water is preferentially retained in the flow stagnation area. Besides the observations, scenario runs using a three-dimensional
numerical model also indicate strong modulation by monsoon winds. Both summer southwest monsoon and winter northeast monsoon
reduce brackish water retention; the latter is found to be more effective.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
24.
25.
26.
27.
The seaweeds Fucus vesiculosus, Fucus serratus, Ascophyllum nodosum and Cladophora glomerata and crustaceans of the Idothea and Gammarus families have proven to be excellent bioindicators for radioactive corrosion products released from a nuclear power plant into the marine environment. These bioindicators have been used to map the spatial and temporal distribution of the released radioactivity. The activity has been followed up to 150 km from the power plant, and the decrease in activity concentration C(z) in the bioindicators with distance z can be expressed by a power function C(z) = α. z?1·4 where α is a constant.The variation with time of activity concentration very well reflects the amount of activity discharged from the power plant, with surprisingly good resolution in time.The bioindicators exhibit different uptake patterns of the radionuclides detected, and variations from summer to winter for the crustaceans Idothea, when compared to Fucus, has been found. 相似文献
28.
Glacial-interglacial relationship between carbonate components and sediment reflectance in the North Atlantic 总被引:2,自引:0,他引:2
A high-resolution composite sediment record from intermediate water depths in the North Atlantic, dating back to marine isotope stage (MIS) 13, was investigated in order to determine the relationship between sediment reflectance (gray level%) and carbonate content (weight%). For this purpose, a detailed analysis of the coarse (>20 µm) and fine (<20 µm) carbonate components was carried out to assess which of the two carbonate components drives glacial-interglacial changes in sediment gray level. The results indicate that the bulk carbonate component is clearly dominated by the fine carbonate fraction, regardless of glacial or interglacial climatic mode, suggesting that the sediment gray level is usually controlled by fluctuations of the fine carbonate content. However, a comparison of MIS 1 and 5.5 indicates that, besides this difference in the contents of the two carbonate size fractions, changing modes in carbonate preservation, i.e., the preservational state of planktonic Foraminifera, may also have a profound influence on total sediment reflectance. 相似文献
29.
Wind and waves are major forces affecting the geomorphology and biota in coastal areas. We present a generally applicable method for measuring and calculating fetch length, fetch direction and wave exposure. Fetch length and direction, measured by geographic information system-based methods, are used along with wind direction and wind speed data to estimate wave height and period by applying forecasting curves. The apparent power of waves approaching the shore, used as a proxy for wave exposure, is then calculated by a linear wave model. We demonstrate our method by calculating fetch lengths and wave exposure indices for five areas with varying exposure levels and types of meteorological conditions in the Finnish Archipelago Sea, situated in the northern Baltic Sea. This method is a rapid and accurate means of estimating exposure, and is especially applicable in areas with geomorphologically varying and complicated shorelines. We expect that our method will be useful in several fields, such as basic biogeographical and biodiversity research, as well as coastal land-use planning and management. 相似文献
30.
Jan E. Vermaat Rene N. Rollon Cristina Day A. Lacap Claire Billot Filipe Alberto Hildie M.E. Nacorda Frank Wiegman Jorge Terrados 《Journal of Sea Research》2004,52(4):201
Flower and fruit production of the abundant, tall, long-lived, dioecious, surface-pollinating seagrass species Enhalus acoroides (L.) Royle were estimated at seven sites in the reef flats off Bolinao (NW Luzon, The Philippines) featuring different fragmentation of the seagrass meadows. Fragmentation of the seagrass meadow was quantified as cover of E. acoroides and all seagrass species present in 20×20 m plots. E. acoroides and overall seagrass cover were correlated positively. The proportion of female flowers of E. acoroides that developed a fruit increased sharply as overall seagrass cover was around 50%. Apparent sex ratio bore no relationship with overall seagrass cover. This threshold-type of relationship suggests that fragmentation of seagrass meadows can have a major effect on the reproductive output of this species. A possible mechanism underlying these results would be a non-linear increase of the efficiency of trapping the surface-dispersed pollen with increasing seagrass canopy density. This provides the first evidence based on real data that fragmentation can affect the population dynamics of seagrass species. 相似文献