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   558篇
  免费   16篇
  国内免费   7篇
测绘学   6篇
大气科学   67篇
地球物理   121篇
地质学   193篇
海洋学   46篇
天文学   105篇
自然地理   43篇
  2023年   3篇
  2021年   5篇
  2020年   13篇
  2019年   12篇
  2018年   11篇
  2017年   11篇
  2016年   20篇
  2015年   8篇
  2014年   19篇
  2013年   33篇
  2012年   24篇
  2011年   27篇
  2010年   17篇
  2009年   27篇
  2008年   17篇
  2007年   29篇
  2006年   26篇
  2005年   18篇
  2004年   23篇
  2003年   20篇
  2002年   16篇
  2001年   16篇
  2000年   14篇
  1999年   15篇
  1998年   17篇
  1997年   12篇
  1996年   3篇
  1995年   7篇
  1994年   7篇
  1993年   5篇
  1992年   7篇
  1991年   4篇
  1990年   11篇
  1989年   4篇
  1987年   5篇
  1986年   3篇
  1985年   6篇
  1984年   9篇
  1983年   6篇
  1982年   4篇
  1981年   5篇
  1979年   3篇
  1978年   3篇
  1977年   3篇
  1976年   3篇
  1975年   3篇
  1973年   5篇
  1972年   4篇
  1968年   2篇
  1957年   2篇
排序方式: 共有581条查询结果,搜索用时 15 毫秒
561.
562.
563.
Hot cluster horizontal branch (HB) stars and field subdwarf B (sdB) stars are core helium burning stars that exhibit abundance anomalies that are believed to be due to atomic diffusion. Diffusion can be effective in these stars because they are slowly rotating. In particular, the slow rotation of the hot HB stars (Teff > 11000 K), which show abundance anomalies, contrasts with the fast rotation of the cool HB stars, where the observed abundances are consistent with those of red giants belonging to the same cluster. The reason why sdB stars and hot HB stars are rotating slowly is unknown. In order to assess the possible role of magnetic fields on abundances and rotation, we investigated the occurrence of such fields in sdB stars with Teff < 30 000 K, whose temperatures overlap with those of the hot HB stars. We conclude that large‐scale organised magnetic fields of kG order are not generally present in these stars but at the achieved accuracy, the possibility that they have fields of a few hundred Gauss remains open. We report the marginal detection of such a field in SB 290; further observations are needed to confirm it (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   
564.
The Triassic through to the Middle Jurassic (Bathonian) stratigraphy of the Kerr McGee 97/12-1 exploration well is described using petrophysical logs, in association with lithological and palaeontological analyses. Over 6210′ of sediment was penetrated, with sixteen Triassic and fourteen Lower–Middle Jurassic sedimentary units recognised, with a total measured depth (T.D) of 7310′ within the Sherwood Sandstone Group, Budleigh Salterton Pebble Beds of Early/Middle Triassic, Olenekian/Anisian age. As expected the sedimentary sequences are comparable to those described from the Wessex Basin, especially the Portland–Wight and Dorset (sub) basins. Of particular note, however, is the very thick halite sequence (1074′) within the Carnian, Dunscombe Mudstone Formation and also an expanded “Paper Shales” (27′) sequence within the earliest Toarcian. A normal fault is noted at 1260′ with the Late Bajocian, Inferior Oolite Group in fault contact with the latest Toarcian, Bridport Sand Formation, Down Cliff Clay Member. The Late Triassic (Rhaetian) to Middle Jurassic (Bathonian) yielded rich microfaunal and palynomorph assemblages, all of which have been previously described throughout northwest Europe. Four microfossils groups (foraminifera, ostracods, dinocysts and miospores) have been used to interpret stratigraphic ages and palaeoenvironments.This study provides new lithological and microfossil data for the Triassic to Middle Jurassic (Bathonian) sequences preserved in the offshore Portland–Wight Basin and provides a key tie-point/reference section for future offshore drilling.  相似文献   
565.
566.
567.
Fellow and Eddington Medallist of the RAS, Fellow of the Royal Society, MBE,pioneer in radar and radio astromy.
Click HERE to view the article.  相似文献   
568.
569.
The Benares meteorite is an LL4 chondrite, not LL6 as recorded in the literature. Some specimens labelled Benares are misidentified.  相似文献   
570.
A common problem faced by geography departments, particularly during times of fiscal compression and mounting pressure for accountability, is how to compare themselves and their faculty with others. The recent revolution in bibliometrics provides a growing volume of data that can be used in benchmarking exercises. In this article, we assess the production and citation of journal articles and books by tenure-track and tenured faculty in selected U.S. and Canadian geography departments (n = 17) according to a set of readily derived and transparent performance indicators derived from publicly available data. Scopus was used to assess article production and citation; Google Scholar was used for book citation. Results point to significant heterogeneity in department characteristics, productivity, and citation of published work. The number of publications, citations, and h-Index scores among scholars in the sample (n = 369) is related strongly to academic age and subfield of enquiry (i.e., physical or human geography) but not—despite apparently marked differences in output and citations—to gender.  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