首页 | 官方网站   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   3248580篇
  免费   278842篇
  国内免费   13265篇
医药卫生   3540687篇
  2021年   49800篇
  2020年   35057篇
  2019年   57917篇
  2018年   70832篇
  2017年   53669篇
  2016年   59397篇
  2015年   73606篇
  2014年   107872篇
  2013年   173010篇
  2012年   88183篇
  2011年   87388篇
  2010年   115604篇
  2009年   120378篇
  2008年   74284篇
  2007年   76754篇
  2006年   87837篇
  2005年   82862篇
  2004年   84677篇
  2003年   75682篇
  2002年   64893篇
  2001年   106380篇
  2000年   98819篇
  1999年   96426篇
  1998年   59204篇
  1997年   57001篇
  1996年   54681篇
  1995年   55581篇
  1994年   49584篇
  1993年   46330篇
  1992年   67608篇
  1991年   64270篇
  1990年   61243篇
  1989年   60332篇
  1988年   55262篇
  1987年   53818篇
  1986年   51014篇
  1985年   50764篇
  1984年   46355篇
  1983年   42266篇
  1982年   40324篇
  1981年   37934篇
  1980年   35853篇
  1979年   37315篇
  1978年   33026篇
  1977年   30905篇
  1976年   27770篇
  1975年   26721篇
  1974年   26977篇
  1973年   25986篇
  1972年   24478篇
排序方式: 共有10000条查询结果,搜索用时 31 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.
Aristodemou  E.  Retzepi  M.  Calciolari  E.  Donos  N. 《Clinical oral investigations》2022,26(8):5223-5235
Clinical Oral Investigations - To evaluate the effect of membrane occlusiveness and experimental diabetes on early and late healing following guided bone regeneration. A total of 30 Wistar rats...  相似文献   
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-23

京公网安备 11010802026262号