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   725篇
  免费   14篇
测绘学   21篇
大气科学   40篇
地球物理   183篇
地质学   243篇
海洋学   28篇
天文学   178篇
自然地理   46篇
  2019年   10篇
  2018年   7篇
  2017年   9篇
  2016年   10篇
  2014年   8篇
  2013年   21篇
  2012年   16篇
  2011年   14篇
  2010年   14篇
  2009年   29篇
  2008年   20篇
  2007年   16篇
  2006年   22篇
  2005年   27篇
  2004年   17篇
  2003年   12篇
  2002年   17篇
  2001年   14篇
  2000年   7篇
  1999年   13篇
  1998年   10篇
  1997年   16篇
  1996年   8篇
  1995年   21篇
  1994年   24篇
  1993年   12篇
  1992年   11篇
  1991年   17篇
  1990年   14篇
  1989年   13篇
  1988年   10篇
  1987年   13篇
  1986年   12篇
  1985年   16篇
  1984年   17篇
  1983年   19篇
  1982年   13篇
  1981年   15篇
  1980年   18篇
  1979年   9篇
  1978年   10篇
  1977年   17篇
  1975年   7篇
  1974年   8篇
  1973年   17篇
  1972年   6篇
  1971年   10篇
  1969年   6篇
  1963年   6篇
  1956年   5篇
排序方式: 共有739条查询结果,搜索用时 718 毫秒
231.
232.

Volume Contents

Contents of Volume 48  相似文献   
233.
We present new photometric observations of 15 symbiotic stars covering their last orbital cycle(s) from 2003.9 to 2007.2. We obtained our data by both classical photoelectric and CCD photometry. Main results are: EG And brightened by ∼0.3 mag in U from 2003. A ∼0.5 mag deep primary minimum developed in the U light curve (LC) at the end of 2006. ZAnd continues its recent activity that began during the 2000 autumn. A new small outburst started in summer of 2004 with a peak U magnitude of ∼ 9.2. During the spring of 2006 the star entered a massive outburst. It reached its historical maximum at U ∼ 8.0 in 2006 July. AEAra erupted in 2006 February with Δmvis ∼ 1.2 mag. BF Cyg entered a new active stage in 2006 August. A brightness maximum (U ∼ 9.4) was measured during 2006 September. CH Cyg persists in a quiescent phase. During 2006 June–December a ∼ 2 mag decline in all colours was measured. CI Cyg started a new active phase during 2006 May–June. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   
234.
235.
During the melting of a snowpack, snow water equivalent (SWE) can be correlated to snow‐covered area (SCA) once snow‐free areas appear, which is when SCA begins to decrease below 100%. This amount of SWE is called the threshold SWE. Daily SWE data from snow telemetry stations were related to SCA derived from moderate‐resolution imaging spectroradiometer images to produce snow‐cover depletion curves. The snow depletion curves were created for an 80 000 km2 domain across southern Wyoming and northern Colorado encompassing 54 snow telemetry stations. Eight yearly snow depletion curves were compared, and it is shown that the slope of each is a function of the amount of snow received. Snow‐cover depletion curves were also derived for all the individual stations, for which the threshold SWE could be estimated from peak SWE and the topography around each station. A station's peak SWE was much more important than the main topographic variables that included location, elevation, slope, and modelled clear sky solar radiation. The threshold SWE mostly illustrated inter‐annual consistency. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   
236.
In 2005, a German research project was started to develop a novel approach to prove safety for a HLW repository in a salt formation, to refine the safety concept, to identify open scientific issues and to define necessary R&D work. This project aimed at identifying the key information for a HLW repository in salt. One important question is how this information may be best fulfilled by natural analogue studies. This question is answered by starting a review of the required key information needs of the safety case (post-closure phase) in order to assess whether or not these requirements can be supported by natural analogues information. In order to structure the review and to address the key elements of the safety concepts, three types of natural analogues are distinguished: (i) natural analogues for the integrity of the geological barrier, (ii) natural analogues for the integrity of the geotechnical barriers and (iii) natural analogues for release scenarios. For the safety case in salt type (i) and (ii) are of highest importance and are treated in this paper. The assessment documented in this paper on the one hand indicates the high potential benefit of natural analogues for a safety case in salt and on the other hand helps to focus the available human and financial resources for the safety case on the most safety-relevant aspects.  相似文献   
237.
Concentrations of CO2 in soil atmosphere and CO2 efflux were measured across a marine terrace soil chronosequence near Santa Cruz, California. Soil development, specifically the formation of an argillic horizon, has created a two-tier soil gas profile in the older terrace soils. The soil above the argillic horizon has seasonal variations in soil CO2 associated with plant respiration. The older soils with dense argillic horizons maintain a year round ~1%CO2 below the argillic horizon. The CO2efflux during the growing season is higher on the older terraces.  相似文献   
238.
239.
This article is essentially the text of lectures presented September 7, 1982 at the Max Born Centenary Conference held in Edinburgh, Scotland and October 21, 1982 at the Max Born Symposium held during the Annual Meeting of the Optical Society of America.Emil Wolf is Wilson Professor of Optical Physics at the University of Rochester. Reprinted fromOptics News, November/December 1983 with permisssion from the author and the Optical Society of America  相似文献   
240.
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