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   1887篇
  免费   61篇
  国内免费   6篇
测绘学   43篇
大气科学   117篇
地球物理   975篇
地质学   413篇
海洋学   34篇
天文学   319篇
综合类   3篇
自然地理   50篇
  2021年   22篇
  2020年   25篇
  2019年   20篇
  2018年   46篇
  2017年   58篇
  2016年   72篇
  2015年   63篇
  2014年   77篇
  2013年   87篇
  2012年   39篇
  2011年   52篇
  2010年   59篇
  2009年   50篇
  2008年   46篇
  2007年   49篇
  2006年   45篇
  2005年   28篇
  2004年   32篇
  2003年   31篇
  2002年   35篇
  2001年   26篇
  2000年   26篇
  1999年   25篇
  1998年   30篇
  1996年   35篇
  1995年   28篇
  1994年   33篇
  1993年   25篇
  1992年   30篇
  1991年   26篇
  1990年   28篇
  1989年   22篇
  1988年   30篇
  1987年   27篇
  1986年   31篇
  1985年   18篇
  1984年   32篇
  1983年   31篇
  1982年   37篇
  1981年   26篇
  1980年   23篇
  1979年   39篇
  1978年   28篇
  1977年   25篇
  1975年   22篇
  1974年   24篇
  1973年   24篇
  1972年   26篇
  1971年   26篇
  1970年   18篇
排序方式: 共有1954条查询结果,搜索用时 15 毫秒
991.
Summary The boundary problem of the potential theory is treated for the case in which the values of the vertical derivative of the gravity anomaly are known. There boundary conditions are derived and alternatives are also treated.Dedicated to RNDr. Jan Pícha, CSc., on his 60th Birthday  相似文献   
992.
Summary The method of spectral analysis has been modified to render the spectrum not only a function of frequency, but also of damping. The generalized spectra of damped geomagnetic pulsations, recorded at the observatories of Budkov and Dymer, are computed. The degree of damping of these pulsations in the X and Y-components at both stations is determined. The results are compared with results obtained using other methods.  相似文献   
993.
Summary With the aid of a simplified model, the gravitational effect of the anomalous part of the atmosphere was analysed theoretically and formulae were derived for numerical computation. It was found that under extreme meteorological conditions this effect is of the same order as the present accuracy of absolute gravity observations, i.e. ±100–150 nm s–2. It is, therefore, recommended to reduce these observations to some model of the normal atmosphere by introducing computational corrections.  相似文献   
994.
995.
Summary The space (time) delay of transmitted waves in the vicinity of the interface beyond the critical point is investigated on two-dimensional seismic models of a low velocity channel; results of laboratory experiments are compared with the conclusions of the theory. The effect of the time delay in field measurements is demonstrated by means of two typical geological formations.  相似文献   
996.
Summary The method of treatment of the macroseismic data obtained on the territory of the CSSR after the main 1976 Friuli earthquake is described and the preliminary results are confronted with the geologic structure.  相似文献   
997.
Summary The paper discusses the obvious experimental relation between the laboratory determinations of total gamma-ray activity, expressed in equilibrium uranium concentration, and heat production due to radioactive decay. The heat production data were calculated by means of the concentrations of uranium, thorium and potassium determined spectrometrically, together with the conversion factors into the rate of heat generation. The obtained relation may help define the typical heat production for characteristic surface rocks and estimate their contribution in heat flow study. Between the gamma-ray activity recorded during aeroradiometric mapping and the laboratory radiometric measurements of surface rock samples, there is also an experimental relation, which can be used further in estimating the value of surface heat production at a chosen locality.  相似文献   
998.
Summary Meteorological microseisms, recorded at the Prague seismic station and, similarly, at other Central Europe stations, reflect certain meteorological situations in the North Atlantic frontal zone. Meteorological elements in this zone are affected by some factors of extra-terrestrial origin, among others by the interplanetary magnetic field (IMF) sector structure. The analysis of the 68 IMF sector boundary passage effects in microseismic activity, expressed in microseismic amplitudes, showed a well-developed minimum of microseismic activity on the day of the boundary passage in winter, but no such effect in spring and autumn. In spring and autumn, however, a tendency was observed to slightly higher microseismic activity in the away (+) sector, whereas no such tendency was observed in winter. These results agree with the IMF effect found in the troposphere. Generally, the IMF sector structure is only a modulating rather than a major factor controlling the microseismic activity.  相似文献   
999.
1000.
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