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   3388篇
  免费   163篇
  3551篇
  2020年   34篇
  2019年   62篇
  2018年   102篇
  2017年   80篇
  2016年   149篇
  2015年   78篇
  2014年   78篇
  2013年   783篇
  2012年   105篇
  2011年   137篇
  2010年   93篇
  2009年   104篇
  2008年   76篇
  2007年   87篇
  2006年   85篇
  2005年   109篇
  2004年   69篇
  2003年   60篇
  2002年   39篇
  2001年   63篇
  2000年   51篇
  1999年   58篇
  1998年   49篇
  1997年   43篇
  1996年   39篇
  1995年   32篇
  1994年   20篇
  1993年   46篇
  1992年   33篇
  1991年   22篇
  1990年   32篇
  1989年   36篇
  1988年   27篇
  1987年   35篇
  1986年   29篇
  1985年   32篇
  1984年   25篇
  1983年   48篇
  1982年   36篇
  1981年   33篇
  1980年   33篇
  1979年   28篇
  1978年   34篇
  1977年   37篇
  1976年   32篇
  1975年   30篇
  1974年   27篇
  1973年   26篇
  1972年   29篇
  1971年   25篇
排序方式: 共有3551条查询结果,搜索用时 0 毫秒
121.
Telepresence-enabled exploration of deep sea environments has developed over the past 30 years, providing access to archaeologists, scientists, and the general public to sites otherwise inaccessible due to depth. Pioneered through the inception of the JASON Project in the late 1980 s, telepresence missions have expanded to two dedicated ships of exploration, NOAA Ship Okeanos Explorer and exploration vessel Nautilus, and has been implemented on a series of opportunistic missions on other vessels. This paper chronicles the history of the use of telepresence for the exploration of shipwrecks in deep water as well as how this capability has allowed the public to engage with such missions. Broadening the scope of who can explore the deep sea, telepresence has also expanded what is observed and documented in the deep, which speaks to humanity’s use of the maritime world and an archaeology of discard through our material disposed of into the deep sea.  相似文献   
122.
123.
Very small, green colored, partially mummified remains of a perinate individual were found buried in a ceramic pot with a copper coin in the Late Medieval cemetery of Nyárl?rinc-Hangár út (“Nyárl?rinc 3. lel?hely”) in southern Hungary. The remains must date back to the second half of the nineteenth century AD. In this paper; we present data gathered in a series of multidisciplinary investigations targeted to the partially mummified remains (ind. no. 14426) and two other non-mummified perinates (ind. no. 10662 and no. 14336) possibly buried under similar circumstances in the cemetery. Besides standard macromorphological and stereomicroscopic examinations, we compared Cu concentrations in the remains using ICP-AES and mapped Cu concentration changes using μXRF. The partially mummified perinate showed the highest Cu concentrations, while the individual buried without a possible Cu source showed the lowest. Body parts in the closer proximity of the copper coins always showed higher concentration. The mummified individual showed 497 times higher Cu values than average, and even the perinate buried without copper coin measured higher than the otherwise normal Cu content of the soil. Extremely high Cu values may be related to the corrosion of the coins included in the burials. Mummification must have been facilitated by copper deriving from the coins. Uneven Cu concentrations and only partial mummification of one of the individuals refer to the importance of other environmental factors involved in a possible quasi-natural mummification process. However, the Nyárl?rinc perinate burial no. 14426 may be the first solely copper-driven mummification case ever reported, and hopefully, more cases are to appear in the future.  相似文献   
124.
125.
126.
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   
127.
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   
128.
129.
This article evaluates the results of almost a decade of experience with regional R&D development and implementation for enhanced innovation in the county of Nordland, Norway. Following a 2002 national devolution initiative, the county of Nordland was the first among Norwegian counties to coin and implement a distinct R&D policy for business-related innovation and development. This was done by setting up a broad regional partnership, framing a regional strategy and by coordinating substantial budgetary resources to implement the strategy. The evaluation describes the results of this process as ambiguous. This article looks at the process from three perspectives. First, we look at the organizational side of how the policy formation and implementation processes have performed. Second, we evaluate the business community response to the policy initiative to see whether any signs of altered behaviour can be found. Third, we look at how the partnership dynamic can explain policy outcomes. Theoretically and policy-wise we then discuss how our findings contribute to new insights in the field of analysing and generating regional innovation policy.  相似文献   
130.
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