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   812081篇
  免费   88089篇
  国内免费   470篇
  900640篇
  2018年   8582篇
  2017年   8088篇
  2016年   11142篇
  2015年   14473篇
  2014年   16860篇
  2013年   23973篇
  2012年   26799篇
  2011年   26835篇
  2010年   18005篇
  2009年   16356篇
  2008年   23437篇
  2007年   23863篇
  2006年   22733篇
  2005年   21506篇
  2004年   21256篇
  2003年   20327篇
  2002年   19553篇
  2001年   40543篇
  2000年   40673篇
  1999年   31530篇
  1998年   10073篇
  1997年   10606篇
  1996年   9889篇
  1995年   9127篇
  1994年   8851篇
  1993年   8888篇
  1992年   24983篇
  1991年   24100篇
  1990年   23258篇
  1989年   22707篇
  1988年   20989篇
  1987年   19628篇
  1986年   18118篇
  1985年   17935篇
  1984年   14570篇
  1983年   12393篇
  1982年   9148篇
  1981年   8228篇
  1980年   7863篇
  1979年   13617篇
  1978年   10473篇
  1977年   9699篇
  1976年   8688篇
  1975年   9771篇
  1974年   10568篇
  1973年   10242篇
  1972年   9239篇
  1971年   8443篇
  1970年   7465篇
  1969年   7204篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
62.
63.
The goal of this study was to develop a new implantable transducer for measuring anterior cruciate ligament (ACL) graft tension postoperatively in patients who have undergone ACL reconstructive surgery. A unique approach was taken of integrating the transducer into a femoral fixation device. To devise a practical in vivo calibration protocol for the fixation device transducer (FDT), several hypotheses were investigated: (1) The use of a cable versus the actual graft as the means for applying load to the FDT during calibration has no significant effect on the accuracy of the FDT tension measurements; (2) the number of flexion angles at which the device is calibrated has no significant effect on the accuracy of the FDT measurements; (3) the friction between the graft and femoral tunnel has no significant effect on measurement accuracy. To provide data for testing these hypotheses, the FDT was first calibrated with both a cable and a graft over the full range of flexion. Then graft tension was measured simultaneously with both the FDT on the femoral side and load cells, which were connected to the graft on the tibial side, as five cadaver knees were loaded externally. Measurements were made with both standard and overdrilled tunnels. The error in the FDT tension measurements was the difference between the graft tension measured by the FDT and the load cells. Results of the statistical analyses showed that neither the means of applying the calibration load, the number of flexion angles used for calibration, nor the tunnel size had a significant effect on the accuracy of the FDT. Thus a cable may be used instead of the graft to transmit loads to the FDT during calibration, thus simplifying the procedure. Accurate calibration requires data from just three flexion angles of 0, 45, and 90 deg and a curve fit to obtain a calibration curve over a continuous range of flexion within the limits of this angle group. Since friction did not adversely affect the measurement accuracy of the FDT, the femoral tunnel can be drilled to match the diameter of the graft and does not need to be overdrilled. Following these procedures, the error in measuring graft tension with the FDT averages less than 10 percent relative to a full-scale load of 257 N.  相似文献   
64.
We propose a mathematical model for pendelluft flow in a single airway bifurcation. The model is motivated by an apparatus used in an experimental study of the pendelluft by Ultman et al. (1988). We derive differential equations governing the fluid flow, which directly connect physiological parameters to the variables determining the pendelluft; this approach allows us to include nonlinearity in the model. If nonlinearity is neglected, our model is identical to the R-I-C circuits used by previous investigators. If nonlinearity is retained, we show that pendelluft can occur even in perfectly symmetric airway bifurcations. For the specific apparatus used in the experiments of High et al. (1991), we demonstrate that two qualitatively different pendelluft flows can occur in the system.  相似文献   
65.
66.
67.
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   
68.
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