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   32711篇
  免费   442篇
  国内免费   406篇
测绘学   1240篇
大气科学   2470篇
地球物理   6375篇
地质学   11560篇
海洋学   2545篇
天文学   7696篇
综合类   146篇
自然地理   1527篇
  2021年   291篇
  2020年   285篇
  2019年   335篇
  2018年   832篇
  2017年   795篇
  2016年   1038篇
  2015年   601篇
  2014年   995篇
  2013年   1734篇
  2012年   1054篇
  2011年   1320篇
  2010年   1099篇
  2009年   1417篇
  2008年   1242篇
  2007年   1187篇
  2006年   1197篇
  2005年   1005篇
  2004年   889篇
  2003年   896篇
  2002年   877篇
  2001年   787篇
  2000年   754篇
  1999年   690篇
  1998年   628篇
  1997年   639篇
  1996年   586篇
  1995年   545篇
  1994年   523篇
  1993年   439篇
  1992年   391篇
  1991年   416篇
  1990年   419篇
  1989年   392篇
  1988年   364篇
  1987年   441篇
  1986年   367篇
  1985年   454篇
  1984年   488篇
  1983年   472篇
  1982年   451篇
  1981年   359篇
  1980年   367篇
  1979年   317篇
  1978年   312篇
  1977年   297篇
  1976年   264篇
  1975年   256篇
  1974年   281篇
  1973年   308篇
  1972年   194篇
排序方式: 共有10000条查询结果,搜索用时 10 毫秒
231.
The three-dimensional flow of an electrically conducting and incompressible viscous fluid past a uniformly accelerated infinite vertical porous plate is studied in a rotating fluid. The flow is assumed to be at small magnetic Reynolds number so that the induced magnetic field is neglected. An exact solution has been obtained by defining a complex velocity with the help of the Laplace transform method for the Prandtl number equal to unity. The effects of rotation, magnetic and free-convection parameters are discussed for the whole problem. Also, the skin-friction components on the plate are discussed.  相似文献   
232.
The discovery of Mercury's magnetosphere by Mariner 10 was surprising since the conventional view of regenerative planetary dynamos had been that the spin requirement would likely have been in excess of the observed spin rate of Mercury. Also internal fluid motions were not expected to be sufficiently large. This paper explores the alternative model of the formation of Mercury's magnetosphere via electromagnetic induction forced by the solar wind. It is shown, however, that the constraints are so severe as to limit severely the applicability of such a model. Although induction is easily observed on the Moon, the modification of the magnetic boundary condition associated with a plasma magnetosphere on Mercury rules out its formation via induction except for interplanetary driving fields which are decreasing in amplitude. That model is explored but retains the difficulty that induced magnetospheres tend to be of small radial and temporal extent compared to that inferred by Ness et al. for Mercury.  相似文献   
233.
Preliminary investigations have been made on two separate pieces from the Aïoun el Atrouss meteorite that fell on April 17, 1974 in southeast Mauritania. The major portion of the meteorite is a brecciated hypersthene achondrite with orthopyroxene (En74) as the major phase. Clasts of eucrite, up to 7 percent in volume within a single slice, occur within the hypersthene achondrite host. No evidence has been found of reaction between the two meteorite types, nor of the presence of any materials intermediate in composition.  相似文献   
234.
235.
Tidal effects of a Schmidt (1965) model galaxy on a typical globular cluster moving in an orbit along the axis of symmetry of the spheroid is studied under the impulsive approximation. Ann-body simulation is made for comparison. Results show that in both cases, a high concentration cluster gains enough energy to be totally dissolved within a distance of 2 kpc. A significant mass loss occurs as the cluster approaches the Roche distance.  相似文献   
236.
Observations from a surface mooring, in a weak-flow regime over the southeastern Bering Sea shelf, were used to derive surface heat fluxes for the period May–July 1996. Changes in heat content of the water column also were determined from subsurface temperature measurements. Agreement of net surface heat flux and change in heat content was within 2%. This result provides additional evidence that heat advection and diffusion are small in this region.  相似文献   
237.
Temperature and radiation effects of the 2010 summer fires are estimated on the basis of measurements at the Zvenigorod Scientific Station (ZSS) of the Obukhov Institute of Atmospheric Physics, Russian Academy of Sciences (RAS), in the Moscow region. The surface air temperature during the 2010 summer smoke varied in antiphase with the aerosol mass concentration, and the thermal radiation balance in the surface layer of the atmosphere varied in phase. Under extreme smoke of the surface layer in August 2010, the reduction in surface air temperature at ZSS has been found to reach 4 K with an increase in the downward flux of thermal radiation by an average of 20 W/m2 and a decrease in the difference between upward and downward fluxes of thermal radiation by an average of 24 W/m2.  相似文献   
238.
This review covers the most significant Russian studies in atmospheric chemistry conducted from 2011 to 2014. This is part of the Russian National Report on the Meteorology and Atmospheric Sciences prepared for the International Association of Meteorology and Atmospheric Sciences (IAMAS). The report was considered and approved by the XXVI General Assembly of the International Union of Geodesy and Geophysics (IUGG).1 The review is appended by a list of publications by Russian scientists for 2011–2014 covering the field of atmospheric chemistry research.  相似文献   
239.
240.
In this paper, data obtained by the Vernov satellite are discussed in comparison with the data obtained by Universitetsky–Tatiana-1, 2 satellites. The advanced instrumentation onboard the Vernov satellite improved the capabilities of the data-transmission system, providing an opportunity to acquire more detailed information on transient atmospheric events (TAEs), including a wider range of TAE photon numbers (event brightness) down to lower photon numbers, the opportunity to observe the events in ultraviolet range without the considerable inclusion of red–infrared photons (which indicates the substantial contribution of electric discharges, lightning precursors, at the altitudes of thunderstorm clouds), and the observation of TAE series at a rate of about 10–100 occurrences per second with a period from tens of seconds to several minutes.  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