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   679008篇
  免费   77404篇
  国内免费   223篇
  2016年   7587篇
  2015年   9867篇
  2014年   12063篇
  2013年   17122篇
  2012年   19092篇
  2011年   19679篇
  2010年   13233篇
  2009年   12352篇
  2008年   17556篇
  2007年   18544篇
  2006年   17286篇
  2005年   16630篇
  2004年   16701篇
  2003年   16118篇
  2002年   15628篇
  2001年   29062篇
  2000年   29675篇
  1999年   23341篇
  1998年   8248篇
  1997年   8670篇
  1996年   8230篇
  1995年   7858篇
  1994年   7816篇
  1993年   7777篇
  1992年   20263篇
  1991年   20319篇
  1990年   19847篇
  1989年   19439篇
  1988年   18116篇
  1987年   17321篇
  1986年   16163篇
  1985年   16454篇
  1984年   13713篇
  1983年   12046篇
  1982年   9005篇
  1981年   8361篇
  1980年   7932篇
  1979年   13521篇
  1978年   10584篇
  1977年   9703篇
  1976年   9161篇
  1975年   10382篇
  1974年   10999篇
  1973年   10762篇
  1972年   10179篇
  1971年   8971篇
  1970年   7895篇
  1969年   7431篇
  1968年   6816篇
  1967年   6023篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
62.
Although phorbol 12-myristate 13-acetate (PMA) inhibits apoptosis and promotes the growth of some types of cells, it induces apoptosis in other cells. We evaluated the apoptotic effects of PMA on murine fibroblasts (L-929) that had been exposed to ultraviolet-B (UV-B) radiation at 312 nm, which promotes tumor cell growth. Exposure to PMA alone did not induce Fas, Fas-L, or apoptosis. Cells exposed to mild UV-B irradiation (80 J/m(2)) alone exhibited a slight expression of Fas and Fas-L 36 to 48 h after the exposure, and exhibited apoptosis as evidenced by DNA fragmentation 72 h after exposure. The addition of PMA (0.8 x 10(-5) to 3.2 x 10(-5) M) to the medium 24 h after the UV-B exposure markedly and dose-dependently enhanced these cell responses. Confluent untreated cells, cells cocultured with PMA, and cells cocultured with PMA for 24 h after the UV-B exposure consistently expressed mRNAs for wild-type p53, bcl-2, and ICE. Expression of c-myc mRNA was initially observed, but became undetectable in the cells cocultured for 24 h with a high concentration of PMA (3.2 x 10(-5) M) following UV-B exposure. Such cells subsequently exhibited the maximal apoptotic response. We conclude that mild exposure to UV-B altered murine fibroblast cells in such a way as to facilitate their death by apoptosis upon addition of PMA.  相似文献   
63.
64.
Over the past 10 years the AIDS crisis has produced a large volume of writing. Much of this is documentary. Dozens of studies of AIDS from various clinical and political perspectives have been complemented by just as many published diaries, autobiographies, novels, plays, and poems. A few of these works have risen to the surface not only as extraordinarily valuable testimonies to the changes AIDS has wrought in individual and collective life but also as first-rate literary works, worth reading because beyond their immediate purposes they articulate with extraordinary lucidity and compassion some deep truths about the human--and the modern--condition. Paul Monette's Borrowed Time is among the most distinctive of those. It speaks not only for the community of people with AIDS and those who support them but for a generation.  相似文献   
65.
66.
67.
68.
Trigger finger is a relatively common clinical entity, most frequently caused by stenosing tenosynovitis. Several other conditions not related to tenosynovitis also have been described as a cause of triggering, and these have been reviewed. We present a rare anomaly of the fourth lumbrical muscle insertion as a cause of triggering of the right little finger. This was completely relieved following excision of the anomalous muscle. This rare anatomic variant should be added to the list of potential causes of trigger finger.  相似文献   
69.
70.
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