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   167339篇
  免费   12035篇
  国内免费   428篇
医药卫生   179802篇
  2023年   754篇
  2022年   968篇
  2021年   2957篇
  2020年   2048篇
  2019年   2875篇
  2018年   3585篇
  2017年   3099篇
  2016年   3448篇
  2015年   3776篇
  2014年   5108篇
  2013年   6891篇
  2012年   10491篇
  2011年   10708篇
  2010年   5836篇
  2009年   5819篇
  2008年   9280篇
  2007年   9761篇
  2006年   9181篇
  2005年   8904篇
  2004年   7802篇
  2003年   7346篇
  2002年   6710篇
  2001年   4803篇
  2000年   4697篇
  1999年   4328篇
  1998年   2047篇
  1997年   1693篇
  1996年   1723篇
  1995年   1430篇
  1994年   1333篇
  1993年   1228篇
  1992年   2885篇
  1991年   2595篇
  1990年   2465篇
  1989年   2323篇
  1988年   2122篇
  1987年   1851篇
  1986年   1774篇
  1985年   1739篇
  1984年   1276篇
  1983年   1118篇
  1982年   700篇
  1981年   599篇
  1980年   525篇
  1979年   966篇
  1978年   636篇
  1977年   552篇
  1975年   444篇
  1974年   493篇
  1973年   469篇
排序方式: 共有10000条查询结果,搜索用时 343 毫秒
991.
Forty-three elderly patients with an intracapsular hip fracture were selected for a prospective randomised trial comparing osteosynthesis (DHS) versus primary hemiarthroplasty (HA) with a 3-year follow-up. The duration of the operation and the perioperative blood loss were significantly shorter in DHS, but inadequate reduction and/or fixation led to serious problems in this group. Clinical morbidity was lower after DHS. No difference could be demonstrated in the mortality rates, fracture- or operation-related complications or the need for secondary intervention. Reintervention could be carried out without additional risk in both groups and did not lead to poor end results. Comparable results were obtained with both methods up to 24 months. At the 36-month follow-up, a significantly worse outcome could be demonstrated in the HA group. We conclude that osteosynthesis is justified as the primary treatment of displaced intracapsular hip fractures in elderly patients. Endoprosthetic replacement can be safely used in cases where osteosynthesis has failed.  相似文献   
992.
993.
994.
Testing the capacity of the trunk extensor muscles may be useful in the diagnosis of low back pain. In the present study, the reproducibility of measurements of maximum trunk extension force, trunk extension endurance, and related electromyographic parameters was investigated. Intraclass correlations indicated that the reproducibility of maximum force and endurance time was satisfactory. Nevertheless, the smallest difference in these parameters that could be attributed, with 95% confidence, to a change in the condition of a patient was, in general, more than 20%. On the electromyograms, the slopes of amplitude and frequency content appeared to be related to endurance time. The reproducibility of these parameters in terms of the intraclass correlation was again satisfactory; however, the smallest detectable difference generally exceeded 50%. The clinical applicability of the parameters studied is severely limited by a lack of reproducibility.  相似文献   
995.
996.
During the initial stages of B lymphocyte differentiation heavy chain variable (VH), diversity (DH) and joining (JH) gene segments recombine to form a functional heavy chain variable region (VDJ) gene. Evidence for genetic polymorphism of the human JH gene segments has been obtained from mature rearranged VDJ sequences. We conducted an analysis of the published rearranged JH gene sequences and found that the JH alleles present in the two published germ-line JH region sequences were rare (approx. 2%) in the rearranged sequences. As an attempt to explain this discrepancy a 2.5-kb strech of DNA containing all the six heavy chain JH region genes and the most 3' DH gene segment, DHQ52, was amplified by the polymerase chain reaction from 39 individuals and analyzed for restriction fragment length polymorphism. Five new JH region haplotypes were found and sequenced. These new haplotypes contained the coding segment alleles that were frequent in antibody genes. Surprisingly, a high number of interallelic differencies in the non-coding sequence was found between the new and the two previously published haplotypes implying that the haplotypes had been separated early in evolution. In this respect the JH locus resembles HLA loci.  相似文献   
997.
998.
Objective To assess the maternal and neonatal effects of upright compared with recumbent positions during delivery, in terms of defined outcome variables.
Design A randomised controlled trial.
Setting St Monica's Nursing Home, a midwife based maternity unit in Cape Town, South Africa.
Participants Five hundred and seventeen women of low obstetrical risk assigned to deliver at the nursing home.
Results The trial showed that women who adopted the upright posture for delivery experienced less pain, perineal trauma and fewer episiotomies than those who delivered in the supine position.
Conclusion The data suggest that in women of low obstetrical risk, choice of posture during delivery may be encouraged.  相似文献   
999.
1000.
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