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   2492篇
  免费   359篇
  2024年   7篇
  2023年   24篇
  2022年   9篇
  2021年   21篇
  2020年   70篇
  2019年   135篇
  2018年   172篇
  2017年   167篇
  2016年   210篇
  2015年   134篇
  2014年   138篇
  2013年   565篇
  2012年   129篇
  2011年   135篇
  2010年   96篇
  2009年   78篇
  2008年   98篇
  2007年   80篇
  2006年   66篇
  2005年   40篇
  2004年   47篇
  2003年   41篇
  2002年   36篇
  2001年   34篇
  2000年   38篇
  1999年   16篇
  1998年   27篇
  1997年   24篇
  1996年   19篇
  1995年   23篇
  1994年   18篇
  1993年   14篇
  1992年   14篇
  1991年   12篇
  1990年   11篇
  1989年   10篇
  1988年   9篇
  1987年   10篇
  1986年   12篇
  1985年   7篇
  1982年   8篇
  1981年   5篇
  1980年   3篇
  1979年   4篇
  1977年   8篇
  1976年   3篇
  1974年   3篇
  1969年   3篇
  1959年   2篇
  1950年   3篇
排序方式: 共有2851条查询结果,搜索用时 140 毫秒
81.
An upper molar of a small bat, here described from an early Miocene freshwater lime-stone deposit at Riversleigh, northwestern Queensland, is the oldest record in Australia of the microchiropteran family Vespertilionidae. The new taxon is referred to the cosmopolitan genus Leuconoe, but it does not appear to be closely related to the two extant Australian species of this genus.  相似文献   
82.
Under Communism, Albania and North Korea rejected de-Stalinisation, clung to leader cults, and, after the acrimonious break between Moscow and Beijing, championed ‘self-reliance’. Often mentioned in passing, the Albanian–North Korean parallel has seldom been analysed. This article highlights three aspects that shaped the Communist regimes' insecurity: the social dynamics of war and early threats; the challenge presented by de-Stalinisation in 1956; and the momentous Sino–Soviet split in the early 1960s. Like the boisterous language of Marxism-Leninism and the drive to engineer a non-capitalist society, insecurity was also built into the Communist international system. Clinging to Stalinist methods, then, was also a reflection of the self-destructive potential of calls for reforming the Communist system, which threatened to tear the Eastern bloc apart. Tirana and Pyongyang pursued different paths to ‘self-reliance’, yet they could not help speaking a similar language and facing similar problems. North Korea ultimately joined the Non-Aligned Movement but achieved little success in the Third World. The irony is that tiny, isolated Albania, which shunned the Movement, ultimately ended up non-aligned: violently critical of Moscow, Beijing, and Washington, and distrustful of practically everyone else.  相似文献   
83.
Accurate simulation of multiphase flow in fractured porous media remains a challenge. An important problem is the representation of the discontinuous or near discontinuous behaviour of saturation in real geological formations. In the classical continuum approach, a refined mesh is required at the interface between fracture and porous media to capture the steep gradients in saturation and saturation‐dependent transport properties. This dramatically increases the computational load when large numbers of fractures are present in the numerical model. A discontinuous finite element method is reported here to model flow in fractured porous media. The governing multiphase porous media flow equations are solved in the adaptive mesh computational fluid dynamics code IC‐FERST on unstructured meshes. The method is based on a mixed control volume – discontinuous finite element formulation. This is combined with the PN+1DG‐PNDG element pair, which has discontinuous (order N+1) representation for velocity and discontinuous (order N) representation for pressure. A number of test cases are used to evaluate the method's ability to model fracture flow. The first is used to verify the performance of the element pair on structured and unstructured meshes of different resolution. Multiphase flow is then modelled in a range of idealised and simple fracture patterns. Solutions with sharp saturation fronts and computational economy in terms of mesh size are illustrated.  相似文献   
84.
Abstract

This paper aims at analyzing what the author calls the “hidden nexus between” Metz and Schmitt. Relying on a Schmittean reference to Metz, pointing to certain conceptual and theoretical, as well as historical components, the paper argues that it is a shared concern about the mistaken modern — utopian reworking of eschatology. The paper also demonstrates how the more recent Metzean rethinking of the problem of theodicy works further this eschatological theme.  相似文献   
85.
86.
At Nunalleq, a pre-contact Yup'ik Eskimo village site in Alaska (14th–17th century AD), abundant insect remains from highly organic substrates preserved within permafrost offer a unique opportunity to investigate past ecological and living conditions. This paper presents the preliminary results obtained from the analysis of two samples collected from floor layers in sod houses. The numerous and diverse insect remains highlight the exciting potential of archaeoentomology for reconstructing past ecological conditions, resource exploitation and the use of space at northern hunter–gatherer sites and have permitted the development of a strategy for the future collection of archaeoentomological data at permafrost-preserved sites in Alaska and elsewhere.  相似文献   
87.
88.
89.
90.
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