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   1021篇
  免费   20篇
  2020年   30篇
  2019年   41篇
  2018年   45篇
  2017年   50篇
  2016年   45篇
  2015年   17篇
  2014年   28篇
  2013年   266篇
  2012年   24篇
  2011年   29篇
  2010年   26篇
  2009年   27篇
  2008年   24篇
  2007年   26篇
  2006年   24篇
  2005年   17篇
  2004年   24篇
  2003年   20篇
  2002年   8篇
  2001年   17篇
  2000年   6篇
  1999年   14篇
  1998年   5篇
  1997年   7篇
  1996年   8篇
  1995年   6篇
  1994年   11篇
  1993年   5篇
  1992年   5篇
  1991年   5篇
  1990年   8篇
  1989年   7篇
  1987年   7篇
  1986年   9篇
  1985年   11篇
  1984年   8篇
  1983年   4篇
  1982年   5篇
  1981年   7篇
  1980年   6篇
  1979年   10篇
  1978年   12篇
  1977年   5篇
  1976年   9篇
  1975年   9篇
  1974年   5篇
  1973年   6篇
  1972年   6篇
  1970年   5篇
  1969年   4篇
排序方式: 共有1041条查询结果,搜索用时 31 毫秒
71.
This article explores the Irish migrant experience in Birmingham during and in the wake of terrorist campaigns carried out in Britain between 1969 and 1975 and attributed to the Irish Republican Army (IRA). Beginning with a discussion of the competencies with which Irishness was associated at the close of the 1960s in England, many of which were hinged on a notion of the Irish predisposition towards violence, the article continues on to take the political, cultural and religious “temperature” of the Irish community in Birmingham between 1969 and 1975, and follows on with a discussion of the specific strategies sought out by Irish immigrants to come to terms with the effect of events such as the “Birmingham Bombings” on their daily lives. Principle findings that emerge from the study indicate that IRA terrorism forced the Irish in Birmingham to engage with and adopt a number of distinct linguistic and cultural strategies in the post-1974 period, the cultivation of which indefinitely altered their relationship with Ireland as “home”, their visibility in the public British sphere and their associational patterns and practices within the migrant enclave.  相似文献   
72.
73.
Federalism often creates additional decisions for interest groups in determining how best to advocate for their policy recommendations in the legislative process. Should they focus their advocacy at the local, state, or national level of government? This article examines interest group behaviors in water quality policy in the Great Lakes region from 1960 to 2000. I evaluate the reasons for interest group decisions about which level of government to target, using historical analysis of Great Lakes water quality policy in the United States and Canada. The results of this analysis show that in many cases groups are influenced in their decision-making based on the level of government that has the greatest jurisdiction over the policy, supporting a neoinstitutional argument.  相似文献   
74.
Rock‐magnetic techniques were used to examine the topsoil layer of Kurma archaeological site (in the Olkhon region, on the north‐western coast of Lake Baikal, Siberia) in an effort to determine the possible sources of iron ores for iron‐smelting centres (at about the bc /ad boundary). Measurements have shown a magnetic enhancement of the topsoil due to magnetite grains resulting from weathering of strongly magnetic crystalline rocks. They have also revealed a preliminary picture of the distribution of strongly magnetic topsoils around the ancient iron‐smelting centres. Perhaps, in addition to traditional sources of raw materials, the ancient metallurgists used black sand talus as an ore deposit.  相似文献   
75.
76.
Thermal–hydrological–mechanical coupling processes suggest that fault permeability should undergo dynamic change as a result of seismic slip. In igneous rocks, a fault's slip surface may have much higher permeability than the surrounding rock matrix and therefore operate as a conduit for fluids. We conducted laboratory experiments to investigate changes in fracture permeability (or transmissivity) of a fault in granite due to shear slip and cyclic heating and cooling. Our experiments showed that high initial fracture transmissivity (>10?18 m3) was associated with a high friction coefficient and that transmissivity decreased during slip. We propose that this reduction in transmissivity reflects the presence of gouge in fracture voids, increasing the area of contact in the fault plane and reducing the hydraulic aperture. In contrast, when initial fracture transmissivity was low (<10?18 m3), we observed that friction was lower and transmissivity increased during slip. The high transmissivity and high friction may be explained by large areas of bare rock being in contact on the slip surface. Slip velocity had little influence on the evolution of permeability, probably because gouge produced at different slip velocities had similar grain size distributions, or because gouge leaked from the slip surface. Transmissivity decreased with increasing temperature in heating tests, probably due to thermal expansion increasing normal stress on the fracture. Frictional heating did not influence transmissivity during the shearing tests.  相似文献   
77.
78.
79.
Behavioral ecology is the study of adaptive behavior in relation to social and environmental circumstances. Analysts working from this perspective hold that the reproductive strategies and decision-making capacities of all living organisms—including humans—are shaped by natural selection. Archaeologists have been using this proposition in the study of past human behavior for more than 30 years. Significant insights on variation in prehistoric human subsistence, life history, social organization, and their respective fossil and archaeological consequences have been among the more important results.  相似文献   
80.
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