全文获取类型
收费全文 | 75997篇 |
免费 | 1326篇 |
国内免费 | 906篇 |
专业分类
测绘学 | 1926篇 |
大气科学 | 5326篇 |
地球物理 | 14293篇 |
地质学 | 27611篇 |
海洋学 | 7202篇 |
天文学 | 17969篇 |
综合类 | 272篇 |
自然地理 | 3630篇 |
出版年
2022年 | 556篇 |
2021年 | 926篇 |
2020年 | 1035篇 |
2019年 | 1074篇 |
2018年 | 2314篇 |
2017年 | 2222篇 |
2016年 | 2666篇 |
2015年 | 1428篇 |
2014年 | 2481篇 |
2013年 | 4125篇 |
2012年 | 2668篇 |
2011年 | 3427篇 |
2010年 | 3038篇 |
2009年 | 3831篇 |
2008年 | 3293篇 |
2007年 | 3358篇 |
2006年 | 3129篇 |
2005年 | 2217篇 |
2004年 | 2244篇 |
2003年 | 2117篇 |
2002年 | 2097篇 |
2001年 | 1872篇 |
2000年 | 1724篇 |
1999年 | 1366篇 |
1998年 | 1427篇 |
1997年 | 1310篇 |
1996年 | 1141篇 |
1995年 | 1073篇 |
1994年 | 1000篇 |
1993年 | 850篇 |
1992年 | 823篇 |
1991年 | 831篇 |
1990年 | 890篇 |
1989年 | 688篇 |
1988年 | 682篇 |
1987年 | 753篇 |
1986年 | 658篇 |
1985年 | 886篇 |
1984年 | 931篇 |
1983年 | 816篇 |
1982年 | 794篇 |
1981年 | 673篇 |
1980年 | 676篇 |
1979年 | 639篇 |
1978年 | 648篇 |
1977年 | 513篇 |
1976年 | 502篇 |
1975年 | 515篇 |
1974年 | 471篇 |
1973年 | 489篇 |
排序方式: 共有10000条查询结果,搜索用时 250 毫秒
941.
Positive gravity anomalies indicate two dense conduits or eruptive centers beneath the northern summit of Sio Guyot, western Mid-Pacific Mountains. The low amplitude of the positive anomalies and the gravity lows flanking the guyot can be explained by crust 2.5 times the normal Pacific Ocean crustal thickness extending to a depth of 22 ± 2 km. The excess mass of the seamount is 100% locally isostatically compensated by the mass deficit below; this compensation may result from flexural loading and voluminous sill injection near a former ridge-crest transform fault system trending roughly ENE and NNW. 相似文献
942.
943.
Observations of fluid mud were made in the lower North Passage of the Yangtze Estuary in February 2000, on 10 -11 August 2000, on 30 - 31 August 2000 (after two strong typhoons), on 21 - 24 August 2000 (neap tide) and on 3 -6 September 2000 (mean tide) respectively. In situ data show that the fluid mud in this area consists of fine cohesive sediment (median size 7.23 μm). The formation and movement of fluid mud varied during the neap-spring and flood-ebb tidal cycle. Observations suggest that fluid mud phenomena in this area may be categorised in a three-fold manner as slack water, storm and saltwedge features. The thickness of the fluid mud layer of slack water during the neap tide ranged from 0.2 to 0.96 m, whereas during the mean tide, the thickness ranged from 0.17 to 0.73 m, and the thickness of the fluid mud layer was larger during slack water than at the flood peak. Shoals cover an area of 800 km^2 with a water depth smaller than 5 m. Erosion of these extensive intertidal mudflats due to storm action provides an abundant sediment source. This is particularly significant in this estuary when the tidal level is lower than 5 m. The lower North Passage is a typical zone of saltwater wedging, so the saltwedge fluid mud has the most extensive spatial range in the estuary. 相似文献
944.
R. S. Bortkovskii B. N. Egorov V. M. Kattsov T. V. Pavlova 《Izvestiya Atmospheric and Oceanic Physics》2007,43(3):378-383
Annual mean fluxes of CO2 and oxygen across the sea surface are estimated with the use of numerical modeling for several regions located in the Gulf Stream and Kuroshio zones. The present-day climatic conditions and the climatic conditions expected in the middle and at the end of the 21st century are considered. Specific features of gas exchange under a strong wind that are associated with gas exchange by bubbles and with changes in the air-water difference of the gas concentrations were taken into account in the calculations. The estimates obtained differ substantially from the results based on the traditional approach, which disregards the above features. A considerable increase in the absorption of CO2 by the ocean, which is mainly caused by the continuing increase in the CO2 concentration in the air during its small changes in the ocean, is expected in the 21st century. At the same time, no trends are revealed in the annual mean fluxes of oxygen across the ocean surface. The conclusion is made that, in calculations of CO2 absorption by the world ocean, it is necessary to take into account both specific features of gas transfer under a strong wind and an increase in the atmospheric concentration of CO2. 相似文献
945.
The results of continuous seismic profiling thermodynamics performed in the northern part of the Japan Basin in the region of the Tarasov Rise and the data of a micropaleontological examination of the diatom remains encountered in the sediment samples from the rise and continental slope are presented. In the area studied, the topography of the acoustic basement features a vast rise (plateau) buried under the sedimentary cover outlined by the depth contour 5.8 s. The plateau has a relatively smooth top surface crossed by a series of rises of the acoustic basement. The two largest rises are represented by the ridges of the Tarasov Rise. The plateau is separated from the continental slope by a depression in the acoustic basement with a depth up to 6.8 s. From the end of the Middle Miocene up to the beginning of the Paleocene, the region of the plateau represented an area of active volcanism; it coincided in time with the stage of subsidence of the floor of the acoustic basement depression. At the end of the Late Miocene, the ridges of the Tarasov Rise started to sink. In the Pliocene, this process accelerated, and, at the beginning of the Pleistocene, it stopped. In the Middle Miocene-Early Pleistocene time, the portion of the continental slope adjacent to the plateau remained stable and suffered no significant vertical movements. 相似文献
946.
O. O. Trusenkova S. V. Stanichnyi Yu. B. Ratner 《Izvestiya Atmospheric and Oceanic Physics》2007,43(5):634-648
The expansion of wind fields observed at fixed times (four times daily) in complex empirical orthogonal functions is performed for the Japan Sea area (34°–53° N, 127°–143° E). The wind fields are taken from the 1998–2004 NCEP/NCAR Reanalysis data with better spatial resolution (1° × 1°) than the standard product, which are publicly available on the Internet. Major modes of wind variability in the Japan Sea area are identified. The modes determine a general direction of air-mass transport throughout a year, zonal and meridional modulation, and a cyclonic and an anticyclonic eddy component. Objective classification of wind fields with respect to the prevailing flow direction is performed, and wind stress and wind-curl patterns are obtained for major events in the cold and warm periods of the year. The pattern obtained can be used in hydrodynamic numerical models of the general circulation of the Japan Sea. 相似文献
947.
948.
光生物反应器中光衰减特征与螺旋藻生长动力学研究 总被引:3,自引:0,他引:3
分析了光照强度在光生物反应器中的分布特征,结果表明,当光波长及光传播的路径确定时,光生物反应器中光衰减特征主要受培养物生物量浓度的影响,由回归的模型对实验数据的拟合可分析光衰减特征与培养物生物量浓度的相关性,为光生物反应器中平均光照强度的确定奠定基础。在光生物反应器中,当营养底物和环境温度不是螺旋藻生长限制因子时,通过平均光照强度对螺旋藻比生长速率的影响分析,结果表明,在实验条件下,螺旋藻比生长速率与平均光照强度的动力学模型可用Aiba光生长抑制方程描述,光亲和系数Ks为238.29umol/(m^2.s),光抑制系数Ki为0.00493s.m^2/umol,光生物反应器中螺旋藻生长的饱和光照强度出现在190-272umol/(m^2.s)的范围内。 相似文献
949.
The mechanism of the effect of a collapsing turbulent eddy on diapycnal transport in a stably stratified fluid is considered. It is shown that at small Richardson turbulent numbersRi
0 the mixing efficiency increases asRi
0, and at large numbers it decreases in proportion toRi
0
–1/2
.Translated by Mikhail M. Trufanov. UDK 551.465.15. 相似文献
950.
Peculiarities of the dynamics and the structure formation in the estuary run-off lenses have been analysed based on field data obtained at the Guinean coast (the central eastern Atlantic Ocean). Attention was paid to the processes of restratification, internal mixing, and exchange in the areas of the frontal zone of the run-off lens and the tidal frontal zone. The stabilization of the front of the estuary run-off lens by means of the periodic washing out of its forepart by tidal upwelling is described. The mechanisms of the energy transformation in the leading part of the lens have been revealed. Effects of run-off and loczalization of transformed waters in the small-scale frontal zones are found. The energy estimations represented will be useful in considering analogous phenomena in other coastal regions.Translated by Mikhail M. Trufanov. 相似文献