全文获取类型
收费全文 | 7457篇 |
免费 | 383篇 |
出版年
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.
Sven Oliver Müller 《European Review of History》2010,17(6):835-859
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.
M. G. Blöcher G. Zimmermann I. Moeck W. Brandt A. Hassanzadegan F. Magri 《Geofluids》2010,10(3):406-421
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