全文获取类型
收费全文 | 104296篇 |
免费 | 1733篇 |
国内免费 | 709篇 |
专业分类
测绘学 | 2329篇 |
大气科学 | 7076篇 |
地球物理 | 20250篇 |
地质学 | 37694篇 |
海洋学 | 9449篇 |
天文学 | 23663篇 |
综合类 | 256篇 |
自然地理 | 6021篇 |
出版年
2022年 | 687篇 |
2021年 | 1178篇 |
2020年 | 1268篇 |
2019年 | 1394篇 |
2018年 | 2918篇 |
2017年 | 2744篇 |
2016年 | 3203篇 |
2015年 | 1649篇 |
2014年 | 3110篇 |
2013年 | 5496篇 |
2012年 | 3391篇 |
2011年 | 4413篇 |
2010年 | 3985篇 |
2009年 | 5042篇 |
2008年 | 4401篇 |
2007年 | 4495篇 |
2006年 | 4212篇 |
2005年 | 3044篇 |
2004年 | 2971篇 |
2003年 | 2768篇 |
2002年 | 2745篇 |
2001年 | 2444篇 |
2000年 | 2372篇 |
1999年 | 1915篇 |
1998年 | 1945篇 |
1997年 | 1863篇 |
1996年 | 1581篇 |
1995年 | 1571篇 |
1994年 | 1370篇 |
1993年 | 1261篇 |
1992年 | 1206篇 |
1991年 | 1218篇 |
1990年 | 1219篇 |
1989年 | 1069篇 |
1988年 | 1019篇 |
1987年 | 1162篇 |
1986年 | 1017篇 |
1985年 | 1264篇 |
1984年 | 1380篇 |
1983年 | 1373篇 |
1982年 | 1270篇 |
1981年 | 1172篇 |
1980年 | 1100篇 |
1979年 | 1017篇 |
1978年 | 972篇 |
1977年 | 846篇 |
1976年 | 843篇 |
1975年 | 816篇 |
1974年 | 809篇 |
1973年 | 861篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
971.
We present a numerical model of the dynamics of Lake Donuzlav, which enables one to perform simultaneous numerical analyses
of the currents, sea level, waves, and sediment transport. The model is based on the hydrodynamic block and the spectral wave
model. For typical storm situations, we study the specific features of the integral circulation of waters and the three-dimensional
structure of currents, investigate the wind-induced wave fields, and evaluate the flows of sediments and deformations of the
bottom. The presence of intense eddy structures is revealed in the field of currents caused by the bottom topography. A significant
intensification of waves in the south part of the lake is established in the case of penetration of storm waves through the
strait. It is shown that the account of waves leads to qualitative changes in the structure of circulation in the lake and
to the formation of well-pronounced areas of wave-induced elevations and lowerings of the sea level.
__________
Translated from Morskoi Gidrofizicheskii Zhurnal, No. 2, pp. 43–65, March–April, 2006. 相似文献
972.
C. Riedel A. Tryggvason B. Brandsdottír T. Dahm R. Stéfansson M. Hensch R. Böðvarsson K. S. Vogfjord S. Jakobsdottír T. Eken R. Herber J. Holmjarn M. Schnese M. Thölen B. Hofmann B. Sigurdsson S. Winter 《Marine Geophysical Researches》2006,27(4):267-281
Between June 2004 and September 2004 a temporary seismic network was installed on the northern insular shelf of Iceland and onshore in north Iceland. The seismic setup aimed at resolving the subsurface structure and, thus, the geodynamical transition from Icelandic crust to typical oceanic crust along Kolbeinsey Ridge. The experiment recorded about 1,000 earthquakes. The region encloses the Tjörnes Fracture Zone containing the Husavik–Flatey strike-slip fault and the extensional seismic Grimsey Lineament. Most of the seismicity occurs in swarms offshore. Preliminary results reveal typical mid-ocean crust north of Grimsey and a heterogeneous structure with major velocity anomalies along the seismic lineaments and north–south trending subsurface features. Complementary bathymetric mapping highlight numerous extrusion features along the Grimsey Lineament and Kolbeinsey Ridge. The seismic dataset promises to deliver new insights into the tectonic framework for earthquakes in an extensional transform zone along the global mid-ocean ridge system. 相似文献
973.
Loop Current Frontal Eddies (LCFE) in the Gulf of Mexico are simulated with a regional configuration of the Princeton Ocean Model using a feature-oriented initialization technique. The initialization procedure is based on a prior investigation of stability characteristics of the Loop Current (LC). Zonal channel experiments conducted with a multi-layer intermediate equations model allowed to identify conditions necessary for formation and growth of frontal eddies. The simulations were able to reproduce key features of LCFE-topography interaction in the DeSoto Canyon region observed during the “Eddy Intrusion” study. 相似文献
974.
Surface waves are the roughness element of the ocean surface. The parameterization of the drag coefficient of the ocean surface is simplified by referencing to wind speed at an elevation proportional to the characteristic wavelength. The dynamic roughness is analytically related to the drag coefficient. Under the assumption of fetch limited wave growth condition, various empirical functions of the dynamic roughness can be converted to equivalent expressions for comparison. For datasets covering a wide range of the dimensionless frequency (inverse wave age), it is important to account for the variable rate of wave development at different wave ages. As a result, the dependence of the Charnock parameter on wave age is nonmonotonic. Finally, the analysis presented here suggests that the significant wave steepness is a sensitive property of the ocean surface and a single variable normalization of the dynamic roughness using a wavelength or wave height parameter actually produces more robust functions than bi-variable normalizations using wave height and wave slope. 相似文献
975.
Page DS Boehm PD Brown JS Neff JM Burns WA Bence AE 《Marine environmental research》2005,60(4):422-436
Polycyclic aromatic hydrocarbons (PAH) were measured in mussels (Mytilus trossulus) collected between 1990 and 2002 from 11 sites on the shores of Prince William Sound (PWS), Alaska, that were heavily oiled by the 1989 Exxon Valdez oil spill (EVOS). This study, utilizing the methods of the NOAA Status and Trends Mussel Watch Program, found that concentrations of PAH released from spill remnants have decreased dramatically with time and by 2002 were at or near the range of total PAH (TPAH) of 3-355 ng/g dry weight obtained for mussels from unoiled reference sites in PWS. Time-series TPAH data indicate a mean TPAH half-life in mussel tissues of 2.4 years with a range from 1.4 to 5.3, yielding an annual mean loss of bioaccumulated TPAH of 25%. The petroleum-derived TPAH fraction in mussel tissues has decreased with time, reflecting the decreasing release of EVOS residues in shoreline sediments. These results show that PAH from EVOS residues that remain buried in shoreline sediments after the early 1990s are in a form and at locations that have a low accessibility to mussels living in the intertidal zone. 相似文献
976.
977.
This paper discusses the results obtained through numerical modelling of the annual course of circulation and thermohaline field evolution in the tropical Atlantic under the impact of real wind forcing (from March 1982 to March 1983) and compares them with the calculation of seasonal variability induced by the climatic wind. Changes in the pattern of the equatorial currents and related temperature fields induced by the specific peculiarities in the wind field are analysed.Translated by Vladimir A. Puchkin. 相似文献
978.
The Apennine Chain provides the first example of stratigraphic (time) and synsedimentary tectonic (space) distribution of the calcari aLucina Miocene equivalents of modern cold-vent carbonates. Chemosynthetic faunal assemblages and related carbonate deposits are found at different stratigraphic levels, with peaks during Langhian-Serravallian and late Tortonian-early Messinian times. A general increase in frequency and volume occurs with time. A genetic link between venting and the Messinian Evaporite event is difficult to demonstrate. However,Lucina limestones are limited to preevaporitic times, and their maximum abundance is reached just before the onset of the Messinian Evaporite accumulation.Lucina limestones occur in almost all tectofacies of the orogen, from backland to foreland. 相似文献
979.
A. A. Abrashkin 《Physical Oceanography》1993,4(6):503-505
A non-linear stabilized vortical wave on the surface of an infinitely-deep fluid is considered. The angle between the tangents at the apex of the limiting symmetric wave, similar to the Stokes limiting, is shown to equal 120°.Translated by V. Puchkin. 相似文献
980.
Glauconitic minerals range from green smectite to 10Å glauconite, occur mainly in peloids (most of which were fecal pellets), and apparently were produced largely by neoformation replacing several kinds of substrate. Chamositic minerals, berthierine and chamosite, occur in Recent and ancient peloids, but mostly in ancient ooids, and they developed by alteration of a precursor Al-rich clay mineral. Ooid sheaths were built by rolling of cores on ue sea floor. Glauconitic greensands and chamositic oolitic ironstones are condensed sequences deposited as sandwaves during long periods of reduced influx of sediment. Some are associated with hardgrounds. 相似文献