全文获取类型
收费全文 | 36167篇 |
免费 | 455篇 |
国内免费 | 390篇 |
专业分类
测绘学 | 956篇 |
大气科学 | 2493篇 |
地球物理 | 6965篇 |
地质学 | 12927篇 |
海洋学 | 3355篇 |
天文学 | 8463篇 |
综合类 | 101篇 |
自然地理 | 1752篇 |
出版年
2022年 | 229篇 |
2021年 | 388篇 |
2020年 | 404篇 |
2019年 | 494篇 |
2018年 | 1077篇 |
2017年 | 966篇 |
2016年 | 1159篇 |
2015年 | 576篇 |
2014年 | 1072篇 |
2013年 | 1861篇 |
2012年 | 1196篇 |
2011年 | 1537篇 |
2010年 | 1466篇 |
2009年 | 1833篇 |
2008年 | 1637篇 |
2007年 | 1660篇 |
2006年 | 1550篇 |
2005年 | 1144篇 |
2004年 | 1117篇 |
2003年 | 1027篇 |
2002年 | 963篇 |
2001年 | 843篇 |
2000年 | 864篇 |
1999年 | 711篇 |
1998年 | 716篇 |
1997年 | 673篇 |
1996年 | 503篇 |
1995年 | 513篇 |
1994年 | 524篇 |
1993年 | 407篇 |
1992年 | 380篇 |
1991年 | 354篇 |
1990年 | 403篇 |
1989年 | 338篇 |
1988年 | 330篇 |
1987年 | 379篇 |
1986年 | 312篇 |
1985年 | 424篇 |
1984年 | 430篇 |
1983年 | 430篇 |
1982年 | 393篇 |
1981年 | 327篇 |
1980年 | 360篇 |
1979年 | 301篇 |
1978年 | 286篇 |
1977年 | 293篇 |
1976年 | 239篇 |
1975年 | 255篇 |
1974年 | 248篇 |
1973年 | 234篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
931.
932.
933.
934.
M. B. de Groot H. den Adel T. P. Stoutjesdijk C. J. van Westenbrugge 《Coastal Engineering》1995,26(3-4)
Flow slides may affect the stability of dikes. A flow slide is an instability of a submerged slope caused by liquefaction of loose, (medium) fine sand. Whether a flow slide will occur depends on the properties of the sand, which are a function of its density, and the geometry of the slope, as determined by wave and current induced scour and sedimentation. The influence of sand properties and the geometry parameters on the risk of flow slides are discussed. The application of a flow slide prediction method to an example and a risk analysis is briefly discussed. 相似文献
935.
E. A. Agafonov S. T. Kaminsky A. S. Kukushkin Yu. A. Prokhorenko 《Physical Oceanography》2000,10(4):351-364
On the basis of the results of simultaneous observations of parameters of currents, attenuation factor of light, and temperature
performed aboard a moving vessel, we established the main characteristics and features of the circulation of waters and the
structure of transparency and temperature fields in the surface layer of the northwest part of the Black Sea. We investigate
the correlation between the variability of fluid dynamics and redistribution of transparency and temperature fields. The measured
currents are compared with those calculated using the actual field of atmospheric pressure during the time of observation.
It is shown that the results obtained in the areas of steady currents in the west and central regions are in good agreement.
Translated by Peter V. Malyshev and Dmitry V. Malyshev 相似文献
936.
We analyze the seasonal variability of the climatic hydrophysical fields of the Black Sea reporduced in three numerical experiments
carried out according to the model of circulation. The numerical predictions are performed for a period of 12.5 yr on the
basis of the hydrological data accumulated in 1983–1995. The monthly average climatic fields of the current speed are reconstructed
according to the data on the climatic fields of temperature and salinity by the method of hydrodynamic adaptation (standard).
It is shown that, in prognostic calculations, the seasonal variability of temperature and salinity is qualitatively close
to the “standard” dependence. At the same time, the quantitative difference between the climatic behavior of the model and
the standard dependence may be significant. The annual cycle of the currents is characterized by the intensification of the
Main Black-Sea Current in winter. The structure of the hydrophysical fields of the sea in the model becomes much more realistic
if it is based on the actual hydrological data.
Translated by Peter V. Malyshev and Dmitry V. Malyshev 相似文献
937.
J P Shaw A T Large J K Chipman D R Livingstone L D Peters 《Marine environmental research》2000,50(1-5):405-409
Mytilus edulis digestive gland microsomes were prepared from indigenous populations sampled from a clean reference site (Port Quin) and an urban-industrial contaminated site (Blackpool) in the UK. Samples were collected in March/April, May, August and December 1998. Western blot analysis was performed using polyclonal antibodies to fish CYP1A and rat CYP2E using partially purified M. edulis CYP as a positive control, to aid identification. CYP1A- and CYP2E-immunopositive protein levels showed different site-specific seasonal variation with higher levels of CYP2E determined in May (P < 0.05). At both sites, lower levels of CYP1A-immunopositive protein but not CYP2E-immunopositive protein were observed in the samples collected in December (P < 0.05). This correlated with lower levels of nuclear DNA damage (Comet assay expressed as per cent tail DNA) observed in December compared to August (P < 0.05). 相似文献
938.
939.
940.
J. F. Read M. I. Lucas S. E. Holley R. T. Pollard 《Deep Sea Research Part I: Oceanographic Research Papers》2000,47(12):2341-2367
A survey was made of the Southwest Indian Ocean frontal region between 30 and 50°E containing the Agulhas Return, Subtropical and Subantarctic Fronts. From CTD, SeaSoar and extracted samples the distribution of nitrate, silicate and chlorophyll a is shown to be strongly linked to the front and water mass structure, varying zonally and meridionally. Surface chlorophyll a concentrations were low to the north and south leaving a band of elevated chlorophyll between the Subtropical and Subantarctic Fronts. The low concentration of chlorophyll a to the north, in Subtropical Water, was clearly due to nitrate limitation. Between the Subtropical and Subantarctic Fronts, where the chlorophyll a concentrations were highest, the surface layer showed silicate depletion limiting diatom growth. South of the Subantarctic Front there were deep extending, low concentrations of chlorophyll a, but despite plentiful supplies of macro-nutrients and a well-stratified surface layer, high concentrations of chlorophyll a were absent. Changes from west to east were associated with the meandering of the Southern Ocean Fronts, especially the Subtropical Front, and their strength and proximity to each other. Concentrations of chlorophyll a peaked where the Agulhas Return, Subtropical and Subantarctic Fronts were in close proximity. Combined frontal structures appear to have particularly pronounced vertical stability and are associated with enhanced upwelling of nutrients and leakage of nutrients across the front. Light levels are high within the shallow stable layer. Such conditions are clearly favourable for biological growth and support the development of larger-celled phytoplankton communities. 相似文献