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   7457篇
  免费   383篇
  2020年   119篇
  2019年   176篇
  2018年   234篇
  2017年   211篇
  2016年   286篇
  2015年   180篇
  2014年   166篇
  2013年   1964篇
  2012年   237篇
  2011年   265篇
  2010年   235篇
  2009年   225篇
  2008年   191篇
  2007年   207篇
  2006年   175篇
  2005年   175篇
  2004年   123篇
  2003年   108篇
  2002年   116篇
  2001年   146篇
  2000年   105篇
  1999年   114篇
  1998年   90篇
  1997年   82篇
  1996年   85篇
  1995年   69篇
  1994年   59篇
  1993年   73篇
  1992年   71篇
  1991年   60篇
  1990年   60篇
  1989年   56篇
  1988年   55篇
  1987年   60篇
  1986年   62篇
  1985年   71篇
  1984年   79篇
  1983年   84篇
  1982年   68篇
  1981年   67篇
  1980年   66篇
  1979年   62篇
  1978年   66篇
  1977年   67篇
  1976年   61篇
  1975年   71篇
  1974年   42篇
  1973年   38篇
  1972年   41篇
  1971年   38篇
排序方式: 共有7840条查询结果,搜索用时 15 毫秒
991.
The study of ancient DNA (aDNA) using molecular methods is an increasingly valuable tactic in bioarchaeology. While this method must be carefully undertaken to ensure that the molecules detected are representative of the ancient sample and not modern contaminates, there is a danger that a ‘one size fits all’ approach to validation will lead to misinterpretation and/or missed opportunities of valuable findings. When comparing human and pathogen aDNA, there are many shared technical means that can ensure best practice. However, there are a number of assumptions that should not be used for both scenarios. We discuss these aspects in reference to a recent article published by this journal and highlight some of the latest advances in molecular detection of ancient pathogen DNA that can further improve this endeavour. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   
992.
The paper explores interpretations of two sets of pathological horse vertebrae identified during analyses of animal bones from recent excavations at the castle at Malbork in northern Poland (formerly Marienburg in Prussia). One specimen dates to the 18th century and the other to the medieval period. The castle was initially constructed by the Teutonic Order from the late 13th century and occupied by military institutions into the 19th century, and is one of the largest fortified structures in Europe. The pathological vertebrae are attributed to prolonged load‐bearing. The problematic interpretation of the remains from the medieval context as belonging to a warhorse is discussed. Warhorses are widely described in contemporary documentary sources which indicate that mares were typically kept in farms on the Order's estates in late‐medieval Prussia, while studs were separately stabled at castles. There is not enough data to confirm the medieval specimen as a warhorse, and both vertebrae may simply represent riding animals. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   
993.
994.
995.
996.
997.
998.
The aim of this article is to establish the extent to which the history of music can offer new perspectives on the modern period. We need a change of perspective, moving away from the aesthetic debates on music to an investigation of actual experiences and practices of participants. Audience behaviour provides a link between musical production and society. In order to make opera houses and concert halls visible as social spheres, this article draws on examples from the musical life of Berlin and London in the 1800s. Music should no longer be regarded as a peripheral phenomenon, but instead as a potential historical question. The analysis of musical performances prompts at least one: music matters.  相似文献   
999.
1000.
Understanding hydrothermal processes during production is critical to optimal geothermal reservoir management and sustainable utilization. This study addresses the hydrothermal (HT) processes in a geothermal research doublet consisting of the injection well E GrSk3/90 and production well Gt GrSk4/05 at the deep geothermal reservoir of Groß Schönebeck (north of Berlin, Germany) during geothermal power production. The reservoir is located between ?4050 to ?4250 m depth in the Lower Permian of the Northeast German Basin. Operational activities such as hydraulic stimulation, production (T = 150°C; Q = ?75 m3 h?1; C = 265 g l?1) and injection (T = 70°C; Q = 75 m3 h?1; C = 265 g l?1) change the HT conditions of the geothermal reservoir. The most significant changes affect temperature, mass concentration and pore pressure. These changes influence fluid density and viscosity as well as rock properties such as porosity, permeability, thermal conductivity and heat capacity. In addition, the geometry and hydraulic properties of hydraulically induced fractures vary during the lifetime of the reservoir. A three‐dimensional reservoir model was developed based on a structural geological model to simulate and understand the complex interaction of such processes. This model includes a full HT coupling of various petrophysical parameters. Specifically, temperature‐dependent thermal conductivity and heat capacity as well as the pressure‐, temperature‐ and mass concentration‐dependent fluid density and viscosity are considered. These parameters were determined by laboratory and field experiments. The effective pressure dependence of matrix permeability is less than 2.3% at our reservoir conditions and therefore can be neglected. The results of a three‐dimensional thermohaline finite‐element simulation of the life cycle performance of this geothermal well doublet indicate the beginning of thermal breakthrough after 3.6 years of utilization. This result is crucial for optimizing reservoir management. Geofluids (2010) 10 , 406–421  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