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   23225篇
  免费   407篇
  国内免费   32篇
教育   16772篇
科学研究   2002篇
各国文化   220篇
体育   1794篇
综合类   34篇
文化理论   198篇
信息传播   2644篇
  2022年   132篇
  2021年   236篇
  2020年   376篇
  2019年   509篇
  2018年   725篇
  2017年   792篇
  2016年   735篇
  2015年   438篇
  2014年   591篇
  2013年   4452篇
  2012年   582篇
  2011年   641篇
  2010年   500篇
  2009年   471篇
  2008年   538篇
  2007年   513篇
  2006年   454篇
  2005年   398篇
  2004年   386篇
  2003年   349篇
  2002年   388篇
  2001年   441篇
  2000年   403篇
  1999年   408篇
  1998年   214篇
  1997年   235篇
  1996年   260篇
  1995年   218篇
  1994年   220篇
  1993年   200篇
  1992年   308篇
  1991年   310篇
  1990年   336篇
  1989年   325篇
  1988年   305篇
  1987年   254篇
  1986年   260篇
  1985年   332篇
  1984年   276篇
  1983年   261篇
  1982年   210篇
  1981年   213篇
  1980年   190篇
  1979年   249篇
  1978年   226篇
  1977年   199篇
  1976年   165篇
  1975年   131篇
  1974年   125篇
  1973年   155篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
141.
ABSTRACT

The length of telomeres is an objective measure of biologic ageing. This study evaluated the extent minutes of walking per week are associated with leukocyte telomere length (LTL) in a random sample of 5,823 U.S. adults. The investigation was cross-sectional and data were obtained from the National Health and Nutrition Examination Survey (NHANES). LTL was measured by the quantitative polymerase chain reaction method. Walking minutes was calculated from walking frequency and duration measures. Results showed that for each year of chronological age, telomeres were 15.6 base pairs shorter (P < 0.0001). With walking minutes and LTL treated as continuous variables, the relationship was quadratic, not linear (F = 11.2, P = 0.0023). With walking time divided into three categories, adults who performed ≥ 150 minutes of walking per week had longer telomeres than those who did no regular walking, and those who did some, but less than the recommendation (F = 5.0, P = 0.0137). Regular walkers were estimated to have a biologic ageing advantage associated with 6.5–7.6 years less biologic ageing compared to non-walkers, after adjusting for covariates. Additional investigations designed to study causality and the mechanisms associated with the walking and LTL relationship are needed.  相似文献   
142.
143.
ABSTRACT

Amid rising controversy around the alleged distinctions between merit and excellence lies a familiar refrain, scarcity. The narrative of academic scarcity, proclaiming the insufficient numbers of scholars and academics of color, permeates conversations in higher education. We suggest that the academic scarcity narrative, a remnant of stagnant logics of diversity, circulates as a contemporary mechanism of what we name disciplinary containment. Extending disciplinary conversations around rhetorical containment, we argue that disciplinary containment perpetuates whiteness.  相似文献   
144.
This paper demonstrates the application of module arithmetic for controlling the level of information security by a new technique referred as integer splitting. The basic definitions and concepts of the method are provided. The mathematical function of arising transformation is described in detail; its properties were studied and the basic theorems were proven that justify the use of splitting in practical applications. An active system was designed and characteristic cases of its operation are considered.  相似文献   
145.
146.
147.
148.
149.
150.
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