全文获取类型
收费全文 | 6167篇 |
免费 | 240篇 |
国内免费 | 32篇 |
专业分类
测绘学 | 261篇 |
大气科学 | 750篇 |
地球物理 | 1681篇 |
地质学 | 2387篇 |
海洋学 | 342篇 |
天文学 | 706篇 |
综合类 | 25篇 |
自然地理 | 287篇 |
出版年
2021年 | 85篇 |
2020年 | 107篇 |
2019年 | 77篇 |
2018年 | 186篇 |
2017年 | 196篇 |
2016年 | 287篇 |
2015年 | 195篇 |
2014年 | 252篇 |
2013年 | 355篇 |
2012年 | 200篇 |
2011年 | 273篇 |
2010年 | 266篇 |
2009年 | 334篇 |
2008年 | 251篇 |
2007年 | 185篇 |
2006年 | 188篇 |
2005年 | 141篇 |
2004年 | 110篇 |
2003年 | 129篇 |
2002年 | 122篇 |
2001年 | 131篇 |
2000年 | 108篇 |
1999年 | 103篇 |
1998年 | 104篇 |
1997年 | 98篇 |
1996年 | 74篇 |
1995年 | 88篇 |
1994年 | 94篇 |
1993年 | 46篇 |
1992年 | 50篇 |
1991年 | 40篇 |
1990年 | 61篇 |
1989年 | 52篇 |
1988年 | 49篇 |
1987年 | 44篇 |
1986年 | 40篇 |
1985年 | 65篇 |
1984年 | 63篇 |
1983年 | 83篇 |
1982年 | 63篇 |
1981年 | 59篇 |
1980年 | 54篇 |
1979年 | 48篇 |
1978年 | 69篇 |
1977年 | 45篇 |
1976年 | 44篇 |
1975年 | 62篇 |
1974年 | 60篇 |
1973年 | 65篇 |
1969年 | 35篇 |
排序方式: 共有6439条查询结果,搜索用时 859 毫秒
51.
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
52.
53.
54.
Jörn Thiede Stephanie Pfirman Hans-Werner Schenke Wolfgang Reil 《Marine Geophysical Researches》1990,12(3):197-214
The sea floor of Fram Strait, the over 2500 m deep passage between the Arctic Ocean and the Norwegian-Greenland Sea, is part of a complex transform zone between the Knipovich mid-oceanic ridge of the Norwegian-Greenland Sea and the Nansen-Gakkel Ridge of the Arctic Ocean. Because linear magnetic anomalies formed by sea-floor spreading have not been found, the precise location of the boundary between the Eurasian and the North American plate is unknown in this region. Systematic surveying of Fram Strait with SEABEAM and high resolution seismic profiling began in 1984 and continued in 1985 and 1987, providing detailed morphology of the Fram Strait sea floor and permitting better definition of its morphotectonics. The 1984 survey presented in this paper provided a complete set of bathymetric data from the southernmost section of the Svalbard Transform, including the Molloy Fracture Zone, connecting the Knipovich Ridge to the Molloy Ridge; and the Molloy Deep, a nodal basin formed at the intersection of the Molloy Transform Fault and the Molloy Ridge. This nodal basin has a revised maximum depth of 5607 m water depth at 79°8.5N and 2°47E. 相似文献
55.
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
56.
Erdal Dolu Erkan Gökaşan Engin Meriç Mustafa Ergin Tolga Görüm Hüseyin Tur Berkan Ecevitoğlu Niyazi Avşar Muhittin Görmüş Fatmagül Batuk Buğser Tok Oktay Çetin 《Geo-Marine Letters》2007,27(6):355-381
The Quaternary evolution of the Gulf of İzmit, situated on the tectonically active North Anatolian Fault Zone (NAFZ), was
investigated using seismic reflection, paleontologic, and sediment textural data. On the basis of seismic stratigraphic and
sedimentologic-paleontologic interpretations, four depositional units were distinguished within the Plio-Quaternary sequence
of the Gulf of İzmit. According to these data, Plio-Quaternary deposits supplied from the northern terrestrial area started
to accumulate during a progradational phase, in a south-facing half-graben. A coarse-grained sedimentary unit prograding into
the gulf from the south since 200 ka b.p. indicates a dramatic variation in the evolution of the gulf, with the initiation of a new strike-slip fault of the NAFZ
and a corresponding uplift of the Armutlu Peninsula in the south of the gulf. During the evolution of this fault from a wide
shear zone consisting of right-stepped strike-slip faults and pull-apart basins to a localized principal fault zone, sediments
were deposited under the influence of northerly prograding terrestrial and shallow-marine conditions due to relative sea-level
fluctuations in the Marmara Sea. During this period, the Gulf of İzmit was invaded mainly by Mediterranean and partly by Black
Sea waters. In the latest glacial period, shallow areas in the gulf became subaerially exposed, whereas the central and western
sub-basins of the gulf turned into lakes. The present evolution of the Gulf of İzmit is controlled by the after effects of
the new rupture of the NAFZ and the estuarine nature of the gulf environment. 相似文献
57.
58.
59.
60.
The lake Hunnebotn (A=1 km2, zmax=11 m) has become separated from the sea by isostasis, but a 1.5-m-deep channel is held open by periodic dredging. Water exchange is minor due to the small tidal range (21 cm) and the length of the channel (1.8 km), but there may be an inflow of seawater at spring tides. The terrestrial watershed runoff may be fertilized by sewage and agricultural runoff despite some measures taken to prevent this. Historical and new records of biological communities indicate variations in sensitivity to different phases of the isolation and eutrophication process. The native oyster was most sensitive and disappeared first. Later, the eelgrass disappeared possibly due to overgrowth by epiphytic algae, and finally there was a massive littoral–sublittoral invasion of green algae. The lake should not be left in this condition, for aesthetic reasons and because marine inlets and eutrophic brackish water may serve as refugia for spore populations of toxic microalgae. Improving surface water quality will require better control of anthropogenic sources, but bursts and leaks of nutrients from the anoxic monimolimnion cannot be controlled. 相似文献