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   3440372篇
  免费   293874篇
  国内免费   14535篇
耳鼻咽喉   48655篇
儿科学   106517篇
妇产科学   91603篇
基础医学   538867篇
口腔科学   97083篇
临床医学   305217篇
内科学   605891篇
皮肤病学   93248篇
神经病学   293613篇
特种医学   139330篇
外国民族医学   453篇
外科学   541714篇
综合类   107345篇
现状与发展   25篇
一般理论   2278篇
预防医学   277901篇
眼科学   79759篇
药学   242837篇
  18篇
中国医学   10130篇
肿瘤学   166297篇
  2021年   49900篇
  2020年   35391篇
  2019年   58401篇
  2018年   71338篇
  2017年   54130篇
  2016年   60042篇
  2015年   74298篇
  2014年   108598篇
  2013年   173866篇
  2012年   91754篇
  2011年   90818篇
  2010年   116254篇
  2009年   121379篇
  2008年   78292篇
  2007年   81777篇
  2006年   92581篇
  2005年   87836篇
  2004年   89849篇
  2003年   80905篇
  2002年   70736篇
  2001年   108853篇
  2000年   101558篇
  1999年   99130篇
  1998年   59485篇
  1997年   57353篇
  1996年   54771篇
  1995年   55561篇
  1994年   49899篇
  1993年   46573篇
  1992年   71398篇
  1991年   68018篇
  1990年   64915篇
  1989年   64220篇
  1988年   60025篇
  1987年   58732篇
  1986年   56191篇
  1985年   55849篇
  1984年   50206篇
  1983年   45392篇
  1982年   41881篇
  1981年   39343篇
  1980年   37170篇
  1979年   42614篇
  1978年   37034篇
  1977年   33847篇
  1976年   30669篇
  1975年   30385篇
  1974年   32194篇
  1973年   30906篇
  1972年   29431篇
排序方式: 共有10000条查询结果,搜索用时 109 毫秒
1.
2.
3.
Numerous studies showed that postural balance improves through light touch on a stable surface highlighting the importance of haptic information, seemingly downplaying the mechanical contributions of the support. The present study examined the mechanical effects of canes for assisting balance in healthy individuals challenged by standing on a beam. Sixteen participants supported themselves with two canes, one in each hand, and applied minimal, preferred, or maximum force onto the canes. They positioned the canes in the frontal plane or in a tripod configuration. Statistical analysis used a linear mixed model to evaluate the effects on the center of pressure and the center of mass. The canes significantly reduced the variability of the center of pressure and the center of mass to the same level as when standing on the ground. Increasing the exerted force beyond the preferred level yielded no further benefits, although in the preferred force condition, participants exploited the altered mechanics by resting their arms on the canes. The tripod configuration allowed for larger variability of the center of pressure in the task-irrelevant anterior–posterior dimension. High forces had a destabilizing effect on the canes: the displacement of the hand on the cane handle increased with the force. Given this static instability, these results show that using canes can provide not only mechanical benefits but also challenges. From a control perspective, effort can be reduced by resting the arms on the canes and by channeling noise in the task-irrelevant dimensions. However, larger forces exerted onto the canes can also have destabilizing effects and the instability of the canes needs to be counteracted, possibly by arm and shoulder stiffness. Insights into the variety of mechanical effects is important for the design of canes and the instructions of how to use them.  相似文献   
4.
In the last decade, the development of new radiopharmaceuticals for the imaging and therapy of prostate cancer has been a highly active and important area of research, especially focusing on the prostate-specific membrane antigen (PSMA), an antigen which is upregulated in prostate, as well as in other tumor cells. A large variety of PSMA ligands have been radiolabeled, to date. Among the various derivatives, PSMA-617 resulted to be one of the most interesting in terms of interaction with the antigen and clinical properties, and its lutetium-177 labeled version has recently been approved by regulatory agencies for therapeutic purposes. For this reasons, the radiolabeling with fluorine-18 of a PSMA-617 derivative might be of interest. Beside other methodologies to radiolabel macromolecules with fluorine-18, the “click-chemistry” approach resulted to be very useful, and the copper-catalyzed azide-alkyne cycloaddition (CuAAC) is considered one of most efficient and reliable. This paper proposes the synthesis of a suitable precursor for the radiolabeling with fluorine-18 of a new PSMA-617 derivative. The whole radiosynthetic procedure has been fully automated, and the final product, which proved to be stable in plasma, has been obtained with radiochemical yield and purity suitable for subsequent preclinical studies.  相似文献   
5.
6.
7.
8.
9.
10.
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