首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   99720篇
  免费   1538篇
  国内免费   912篇
测绘学   2464篇
大气科学   7043篇
地球物理   19968篇
地质学   35079篇
海洋学   8811篇
天文学   22517篇
综合类   267篇
自然地理   6021篇
  2022年   506篇
  2021年   965篇
  2020年   1057篇
  2019年   1128篇
  2018年   2485篇
  2017年   2289篇
  2016年   2943篇
  2015年   1701篇
  2014年   2803篇
  2013年   5248篇
  2012年   3021篇
  2011年   4103篇
  2010年   3547篇
  2009年   4758篇
  2008年   4257篇
  2007年   4102篇
  2006年   3866篇
  2005年   3154篇
  2004年   3102篇
  2003年   2926篇
  2002年   2764篇
  2001年   2483篇
  2000年   2370篇
  1999年   1923篇
  1998年   2025篇
  1997年   1948篇
  1996年   1594篇
  1995年   1595篇
  1994年   1390篇
  1993年   1294篇
  1992年   1231篇
  1991年   1145篇
  1990年   1219篇
  1989年   1102篇
  1988年   1016篇
  1987年   1233篇
  1986年   1053篇
  1985年   1303篇
  1984年   1420篇
  1983年   1309篇
  1982年   1252篇
  1981年   1170篇
  1980年   1033篇
  1979年   972篇
  1978年   955篇
  1977年   909篇
  1976年   854篇
  1975年   815篇
  1974年   817篇
  1973年   794篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
961.
Natural Hazards - Socially vulnerable communities experience disproportionately negative outcomes following natural disasters and underscoring a need for well-validated measures to identify those...  相似文献   
962.
Summary Offshore areas are sometimes found in which seismic record assumes the appearance of a sine wave or a simple combination of sine waves. It is more interesting to note that the dominant frequency on the singing records is the third harmonic of a fundamental whose wave length is four times the water depth. In this paper it has been proved that this peculiar phenomenon happens due to the slope of the sedimentary layer near the observational points. Using the method introduced byCovert (1958) of finding the Green's function for built in bodies, pressure field has been obtained in the water layer for a two dimensional point source in the same medium and it has been proved that due to the slope of the sedimentary layer singing is caused by waves of wave-length equal to four times the water depth.  相似文献   
963.
964.
965.
966.
Summary The morphology of the Wadati-Benioff zone in the region of Central America, based on the distribution of 1377 earthquake foci, verified the existence of an intermediate aseismic gap and its relation to active andesitic volcanism, and the non-uniformity of subduction due to the hampering effect of the main structural features of the subducting Cocos plate. Four deep seismically active fracture zones, genetically connected with the process of subduction, and three fracture zones manifesting the possible boundary between the Americas and Caribbean plates were identified in the continental wedge.  相似文献   
967.
The paper presents the results of 2D inversion of deep magnetotelluric (MT) and magnetovariational (MV) soundings along the Naryn Line. The method of partial (sequential) inversions is used. According to this method, at the first stage, magnetovariation responses are used for the localization of deep anomalies of electrical conductivity, and then the magnetotelluric sounding data are invoked to refine the structure of the host medium and the structural details in the upper part of the section. It is shown that this approach enables one to estimate the informativeness of separate components of the electromagnetic field, to reduce the distorting influence of the near-surface geoelectric inhomogeneities, and to increase the stability of the final solution of the inverse problem.  相似文献   
968.
Izvestiya, Physics of the Solid Earth - Abstract—When solving direct and inverse problems of magnetotellurics, magnetic permeability throughout model medium is conventionally assumed to be...  相似文献   
969.
Yerevan State University; Institute of Applied Physics Problems, Armenian Academy of Sciences. Translated fromAstrofizika, Vol. 35, No. 1, pp. 121–129, July–August, 1991.  相似文献   
970.
Extensive mud deposits superimposed on the predominantly sandy inner continental shelf adjacent to the Patos Lagoon estuary, indicates that the Lagoon is a potential source of fine sediments to the coastal sedimentary system. The lagoon is large and shallow, and the water movement is mainly controlled by wind-driven set-up and set-down. The mean river inflow is around 2000 m3 s−1, although peak flow rates exceeding 20,000 m3 s−1 have been observed during El Niño periods. Though the tidal elevations are small, tidal velocities in the lagoon's inlet can be significant due to the large extension of the backwaters. Moreover, significant exchange flows can be generated between the estuary and coastal area due to barotropic pressure gradients established as a function of wind and freshwater discharge. The predominant net flow is seawards, but opposite near-bed flows due to pronounced vertical salinity stratification can also be observed. The coastal area is characterized by small tidal effects, large scale ocean circulation, wind-induced residual flows and wave-driven currents, where the waves originate from swell or are locally generated.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号