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   5330篇
  免费   245篇
  2020年   73篇
  2019年   101篇
  2018年   139篇
  2017年   120篇
  2016年   168篇
  2015年   118篇
  2014年   119篇
  2013年   1557篇
  2012年   170篇
  2011年   177篇
  2010年   166篇
  2009年   162篇
  2008年   140篇
  2007年   139篇
  2006年   136篇
  2005年   77篇
  2004年   65篇
  2003年   75篇
  2002年   62篇
  2001年   92篇
  2000年   73篇
  1999年   69篇
  1998年   66篇
  1997年   43篇
  1996年   51篇
  1995年   61篇
  1994年   55篇
  1993年   49篇
  1992年   48篇
  1991年   37篇
  1990年   36篇
  1989年   39篇
  1988年   44篇
  1987年   52篇
  1986年   43篇
  1985年   55篇
  1984年   56篇
  1983年   61篇
  1982年   56篇
  1981年   56篇
  1980年   55篇
  1979年   47篇
  1978年   46篇
  1977年   50篇
  1976年   42篇
  1974年   46篇
  1973年   27篇
  1971年   30篇
  1970年   27篇
  1968年   28篇
排序方式: 共有5575条查询结果,搜索用时 508 毫秒
941.
942.
943.
From the early twentieth century, the ideological hegemony of Malay monarchy has been challenged by emerging Malay nationalism. Despite the more radical manifestations, however, nationalism has rarely sought to overturn monarchy. Indeed, monarchy and nationalism have co-existed, sometimes uneasily, until the present. This co-existence has been facilitated by a number of factors, not least the linkages between the two: during the colonial period and beyond many prominent nationalists came from aristocratic, even royal backgrounds, while the Malay Rulers themselves were prepared to give their patronage to conservative forms of nationalism. Mutual interest in maintaining political and religious conservatism, nevertheless, has not prevented periodic disputes between princes and politicians as the two have competed for the loyalty of the Malay community. Despite such controversies, the continuing hold exercised by monarchy over Malays has placed a limit on the extent to which the Rulers have been supplanted by alternative representations of loyalty and identity. The ability of Malay monarchy to ‘move a little with the tide’, moreover, has assisted its weathering of the nationalist challenge during Malaya's transition from colonialism to independence.  相似文献   
944.
ABSTRACT

From measurements of the graticules on Saxton's two general maps of England and Wales—the atlas map Anglia and the wall map Britannia—together with other evidence, it is argued that neither map was drawn according to any specific projection, but that both were effectively produced as ‘flat-earth’ maps with the graticules superimposed afterwards. Digital versions of Saxton's maps and of a modern map, the 1:1 million Ordnance Survey transport map, are used in a number of comparisons by means of the computer program MapAnalyst. These comparisons allow the scales of the two Saxton maps to be determined. They also show that the maps are of almost the same accuracy in terms of the positioning of settlements, typically within about 4.6 kilometres, in spite of a difference in scale of a factor of about 3.6. This fact and the direct comparison of the two Saxton maps in MapAnalyst show that they are basically the same map, and it is concluded that a version of the wall map was the first to be drawn and that Anglia is a reduced copy prepared for the atlas. The lengths of Saxton's miles as used on the two maps are calculated and compared with other determinations. The relationship between the two general maps and the county maps is briefly considered, and it is provisionally concluded that the relationship is a close one.  相似文献   
945.
946.
Zhuravlev, A. Yu., & Gravestock, D. I., 1994:03:28. Archaeayaths from Yorke Peninsula, South Australia and archaeocyathan Early Cambrian zonation. Alcheringa 18, 1–54. ISSN 0311-5518.

Two assemblages of archaeocyaths are documented from Lower Cambrian outcrops and drillholes on Yorke Peninsula. South Australia. The older assemblage (11 species) occurs in the uppermost Kulpara Formation and conformably overlying basal Parara Limestone, and is equivalent to Lower Faunal Assemblage II in the Flinders Ranges. The younger assemblage (28 species plus Acanthhcyathus and Rodiocyathus) occurs in the Koolywurtie Member near the top of the Parara Limestone. Equivalent taxa are widespread in the Flinders Ranges, western New South Wales and Antarctica. Archaeocyathan distribution is now sufficiently well known to propose three assemblage zones and two informal assemblages for regional correlation. No new taxa have been added, but Erugatocyathus scutatus (Hill) and Pycnoidocyathus latiloculatus (Hill), hitherto known only from Antarctica, are found in the upper assemblage on Yorke Peninsula. Irregular archaeocyathan systematics are discussed, the ontogeny of Archaeopharetra irregularis (Tylor) clarified, and Kruseicnema Debrenne. Gravestock & Zhuravlev, represented by K. gracilis (Gordon), is fully described.  相似文献   
947.
A fossil described as Lepidostrobus muelleri Johnston is referred to temnospondyl amphibians and is shown to have affinities with either the Rhinesuchidae or the Rhytidosteidae.  相似文献   
948.
Over one hundred years of palaeontological research in northwestern Argentina has provided extensive knowledge of Andean lower Palaeozoic fossil assemblages, with trilobites, graptolites, brachiopods and echinoderms being among the most prominent groups. This record is enriched by the recent discovery of soft-bodied worms in Cambrian outcrops of northwestern Argentina. Palaeoscolex sp. cf. P. ratcliffei from the Furongian Lampazar Formation in Jujuy is described, considerably expanding the biogeographical range of this genus and filling the distributional gap, between the well-known early–middle Cambrian occurrences of Palaeoscolex and those of its Ordovician species.  相似文献   
949.
A meagre ischnacanthid acanthodian fauna, known from fragmentary dentigerous jawbones from Lake Burrinjuck, Yass district, New South Wales, consists of three taxa: Taemasacanthus narrengullenensis, Taemasacanthus cooradigbeensis and an indeterminate ischnacanthid. The fossils are from three Early Devonian (Emsian) units at Taemas: the Bloomfield Limestone Member, the Currajong Limestone Member and the Warroo Limestone Member, which constitute the middle-upper parts of the Taemas Limestone (Murrumbidgee Group); and from Unit 6 of the ‘Upper Reef formation’ at Wee Jasper. Whereas ischnacanthid acanthodian remains are increasingly rarer in the higher levels of the Taemas Limestone, remains of onychodontid and osteolepidid fishes are relatively abundant; Onychodus yassensis sp. nov., Onychodus sp. and isolated osteolepidid teeth are locally common.  相似文献   
950.
Characteristic features of the pelves of 15 species of extant New Guinean highland frogs (Hylidae and Microhylidae) are described and figured. Ilia among species in these families were found to be relatively invariate with similar sized species often indistinguishable; thus fossil species diversity is therefore likely to be underestimated in such deposits. Nine-two disarticulated ilia from the highland Nombe rockshelter deposit represent a minimum of six species: two Hylidae and four Microhylidae; most of these ilia were deposited in the late Pleistocene before significant human activity at the site. Problems of drawing conclusions about the Pleistocene frog fauna of the area, especially what the main predator was, from such a small sample and limited understanding of the site taphonomy are discussed.  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