全文获取类型
收费全文 | 61633篇 |
免费 | 469篇 |
国内免费 | 1134篇 |
专业分类
测绘学 | 2092篇 |
大气科学 | 3724篇 |
地球物理 | 11658篇 |
地质学 | 26119篇 |
海洋学 | 4595篇 |
天文学 | 10437篇 |
综合类 | 2253篇 |
自然地理 | 2358篇 |
出版年
2022年 | 503篇 |
2021年 | 738篇 |
2020年 | 780篇 |
2019年 | 852篇 |
2018年 | 6359篇 |
2017年 | 5473篇 |
2016年 | 4210篇 |
2015年 | 889篇 |
2014年 | 1545篇 |
2013年 | 2117篇 |
2012年 | 2604篇 |
2011年 | 4583篇 |
2010年 | 3783篇 |
2009年 | 4298篇 |
2008年 | 3641篇 |
2007年 | 4309篇 |
2006年 | 1818篇 |
2005年 | 1104篇 |
2004年 | 1237篇 |
2003年 | 1211篇 |
2002年 | 1010篇 |
2001年 | 821篇 |
2000年 | 689篇 |
1999年 | 440篇 |
1998年 | 463篇 |
1997年 | 482篇 |
1996年 | 343篇 |
1995年 | 361篇 |
1994年 | 337篇 |
1993年 | 284篇 |
1992年 | 288篇 |
1991年 | 291篇 |
1990年 | 340篇 |
1989年 | 274篇 |
1988年 | 259篇 |
1987年 | 264篇 |
1986年 | 192篇 |
1985年 | 306篇 |
1984年 | 304篇 |
1983年 | 298篇 |
1982年 | 278篇 |
1981年 | 269篇 |
1980年 | 285篇 |
1979年 | 207篇 |
1978年 | 244篇 |
1977年 | 207篇 |
1976年 | 184篇 |
1975年 | 185篇 |
1974年 | 173篇 |
1973年 | 207篇 |
排序方式: 共有10000条查询结果,搜索用时 11 毫秒
951.
Specific features of variations in the bottom topography of the mid-ocean rift zones with intermediate spreading rates are considered in this work. The rift zones with a transition morphology are analyzed, and the main features of the transition topography are distinguished. Several successive stages of topographic variations, each of which is characterized by a specific relative position of the topographic features of the rift zone cross section, have been distinguished based on an analysis of the character of rift zone topographic variations in going from axial rises to rift valleys. The specific features of variations in the structural segmentation of rift zones with intermediate spreading rates, depending on the morphological changes, have been established. The thermal models of the structure of the rift zone magmatic formations have been considered, and the geodynamic relations of the magmatic systems with the specific features of the morphology and the structural segmentation of the mid-ocean axial zones with the intermediate spreading rates have been discussed. 相似文献
952.
953.
D. V. Kulyamin E. M. Volodin V. P. Dymnikov 《Izvestiya Atmospheric and Oceanic Physics》2009,45(1):37-54
The problem of simulating quasi-biennial oscillations (QBOs) of zonal velocity in the equatorial stratosphere in atmospheric general circulation models is considered. In accordance with the results from Part I of this study on the basis of the models developed at the Institute of Numerical Mathematics of the Russian Academy of Sciences (INM RAS), the possibility of implementing (in these models) mechanisms of QBO excitation through both the interaction of planetary waves with the mean flow and breaking of short gravity waves is investigated. A new high-resolution 2° × 2.5° × 80 version of the INM RAS model is designed, a climate simulation with the two 2° × 2.5° × 39 and 2° × 2.5° × 80 versions of the INM RAS model is briefly described, results of spectral analysis of equatorial wave activity are presented, and the QBO formation processes in these models are considered in detail. For the new 2° × 2.5° × 80 model, realistic QBOs of zonal wind are obtained as the result of the action of both mechanisms. 相似文献
954.
A. V. Vivchar K. B. Moiseenko R. A. Shumskii A. I. Skorokhod 《Izvestiya Atmospheric and Oceanic Physics》2009,45(3):302-313
The task of identifying climatically significant regional anthropogenic emissions and estimating their contribution to the variability of nitrogen oxides observed at a monitoring station is considered on the basis of NO and NO2 surface concentrations measured at the Zotino background observation station (60°26′ N, 89°24′ E, Krasnoyarsk Territory). The approach used is based on an estimation of the conditional probability of polluted air arriving from individual regions by using the results of calculating backward Lagrangian trajectories in the lower troposphere. It is established that the contribution of air masses supplied from industrial regions in the south of the Krasnoyarsk Territory to episodes of high concentrations of nitrogen oxides (>0.7 ppb) is larger than the contribution from cities and towns located in the south of Western Siberia. The results indicate that anthropogenic sources of pollution substantially affect the balance of minor gases in the lower troposphere on a regional scale and that this factor must be taken into account when observational data from the Zotino background station are analyzed and interpreted. 相似文献
955.
Pockmarks in the inner Oslofjord,Norway 总被引:2,自引:3,他引:2
Multibeam bathymetric surveys of the Inner Oslofjord, Norway have revealed a high density of pockmarks in the 179-km2 inner fjord area, which contains over 500 pockmarks of varying size, typically 20–50 m in diameter and 2–10 m deep. These
pockmarks have been investigated with a variety of techniques, including acoustic subbottom profiling, sedimentological and
geochemical analyses of cores, remotely operated vehicle observation, and morphometry. Both the distribution and shapes of
the pockmarks suggest that they are related to structures in the bedrock underlying relatively thin (<50 m) unconsolidated
glacial and postglacial sediments. The data provide no direct indication of a particular mode of pockmark formation, but release
of large amounts of biogenic, shallow methane seems unlikely. Several lines of evidence point to a continuous process of pockmark
formation followed by inactivity, with some pockmarks recently active whereas others have been inactive for a considerable
time. Some pockmarks are characterised by coarse sediment in their centres. The density, variety and easy access make this
pockmark field an ideal model area for pockmark research.
John S. Gray is deceased. 相似文献
956.
R. Len L. Somoza C.J. Gimnez-Moreno C.J. Dabrio G. Ercilla D. Praeg V. Díaz-del-Río M. Gmez-Delgado 《Marine and Petroleum Geology》2009,26(8):1564-1579
This paper presents a computational model for mapping the regional 3D distribution in which seafloor gas hydrates would be stable, that is carried out in a Geographical Information System (GIS) environment. The construction of the model is comprised of three primary steps, namely: (1) the construction of surfaces for the various variables based on available 3D data (seafloor temperature, geothermal gradient and depth-pressure); (2) the calculation of the gas function equilibrium functions for the various hydrocarbon compositions reported from hydrate and sediment samples; and (3) the calculation of the thickness of the hydrate stability zone. The solution is based on a transcendental function, which is solved iteratively in a GIS environment.The model has been applied in the northernmost continental slope of the Gulf of Cadiz, an area where an abundant supply for hydrate formation, such as extensive hydrocarbon seeps, diapirs and fault structures, is combined with deep undercurrents and a complex seafloor morphology. In the Gulf of Cadiz, the model depicts the distribution of the base of the gas hydrate stability zone for both biogenic and thermogenic gas compositions, and explains the geometry and distribution of geological structures derived from gas venting in the Tasyo Field (Gulf of Cadiz) and the generation of BSR levels on the upper continental slope. 相似文献
957.
Ye. V. Zhuleva 《Oceanology》2010,50(1):107-112
The volumes of formed volcanoes are an important indicator of the formation intensity of the ocean floor volcanogenic morphostructure
under different geodynamic conditions. The distribution of the volumes of volcanoes that formed within the oceanic lithosphere
of different geological ages is considered to analyze the spatial and time dynamics of the scopes of the seamount formation.
The greatest volumes of effused rocks concentrate in volcanoes of different heights on the different-age segments of the lithosphere.
The total volumes of volcanogenic substance growing with increasing age and thickness of the lithosphere is caused by the
increasing range of the heights of the formed volcanoes and the growing number of big seamounts. Despite that the volcanic
seamounts formed within the mid-oceanic ridges, on the divergent boundaries of the lithospheric plates and in the transform
faults most often, half of the volcanogenic material was emitted to the earth’s surface during the spreading of the intraplate
volcanism. A leading part in the formation of the volcanogenic morphostructure of the ocean floor belongs to the formation
of big seamounts with heights of 4–6 km and volumes from 1500 to 5100 km3, respectively, in the provinces with ages from 60 to 90 mln years. 相似文献
958.
The results of the complex study of the sedimentary cover (continuous seismic profiling and diatom analysis) in the northeastern
part of the Sea of Japan, including the Bogorov Rise, the adjacent part of the Japan Basin, and the continental slope, are
presented. Two varied-age complexes were distinguished in the sedimentary cover of Primorye’s continental slope, namely, the
Middle Miocene and Late Miocene-Pleistocene; these complexes were formed in a stable tectonic environment with no significant
vertical movements. The depression in the acoustic basement is located along the continental slope and it is divided from
the Japan Basin by a group of volcanic structures, the most uplifted part of which forms the Bogorov Rise. The depression
was formed, probably, before the Middle Miocene. In the Middle Miocene, the Bogorov Rise was already at the depths close to
the modern ones. In the sedimentary cover near the Bogorov Rise, buried zones were found, which probably were channels for
gas transportation in the pre-Pleistocene. Deformations of sediments that occurred in the beginning of the Pleistocene are
established in the basin. 相似文献
959.
The structure of the assemblages associated with the mussel aggregations of Bathymodiolus azoricus was investigated. The mussel beds were found on the hydrothermal vent fields on the Mid-Atlantic Ridge (the Menez Gwen, Lucky
Strike, and Rainbow areas) at the depths of 850–2400 m. The community structure of the mussel bed assemblages varied between
the studied areas. Large number of species was unique to Menez Gwen mussel beds; the most observed taxa were not specialized
hydrothermal species. All the other, nonunique species were found for the Lucky Strike region. The lowest mussel assemblage
structure evenness was observed in the shallowest area, the Menez Gwen area (850 m depth). We assume that two types of mussel
assemblages—nematode-dominated and copepod-dominated ones—exist in the Lucky Strike field. The assemblages of B. azoricus differ significantly from the assemblages of B. thermophilus inhabiting the Pacific hydrothermal vents. 相似文献
960.
Multiyear time series obtained by the continuous instrumental monitoring of the electrical activity (EA) of weakly electric
fish Gnathonemus leopoldianus and the motor activity (MA) of the freshwater catfish Hoplosternum thoracatum and the cockroach Blaberus craniifer are compared to the parameters of the lunisolar gravitational tide. These curves are observed to be very similar for a large
number of time intervals. However, a more detailed analysis shows this to be only a superficial resemblance caused by the
closeness of the periods of diurnal and semidiurnal rhythms of bioindicator activity (the dominant rhythms in EA and MA patterns)
and the periods of main gravitational tidal waves. It is concluded that the lunisolar gravitational tide has no significant
effect on animal behavior in our experiment. 相似文献