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   3875篇
  免费   274篇
  国内免费   3篇
耳鼻咽喉   32篇
儿科学   142篇
妇产科学   88篇
基础医学   492篇
口腔科学   279篇
临床医学   447篇
内科学   686篇
皮肤病学   36篇
神经病学   341篇
特种医学   264篇
外科学   427篇
综合类   199篇
一般理论   2篇
预防医学   290篇
眼科学   53篇
药学   149篇
肿瘤学   225篇
  2021年   66篇
  2020年   24篇
  2019年   42篇
  2018年   32篇
  2017年   42篇
  2016年   33篇
  2015年   50篇
  2014年   73篇
  2013年   108篇
  2012年   167篇
  2011年   168篇
  2010年   109篇
  2009年   90篇
  2008年   161篇
  2007年   137篇
  2006年   183篇
  2005年   165篇
  2004年   167篇
  2003年   126篇
  2002年   122篇
  2001年   128篇
  2000年   107篇
  1999年   124篇
  1998年   68篇
  1997年   60篇
  1996年   66篇
  1995年   53篇
  1994年   65篇
  1993年   31篇
  1992年   99篇
  1991年   107篇
  1990年   74篇
  1989年   94篇
  1988年   99篇
  1987年   89篇
  1986年   81篇
  1985年   75篇
  1984年   60篇
  1983年   60篇
  1982年   42篇
  1981年   40篇
  1980年   39篇
  1979年   55篇
  1978年   37篇
  1977年   37篇
  1976年   35篇
  1975年   27篇
  1974年   25篇
  1972年   21篇
  1969年   21篇
排序方式: 共有4152条查询结果,搜索用时 14 毫秒
1.
2.
PURPOSE: The purpose of this study was to measure spectrophotometrically the color stability of pigmented A-2186 silicone maxillofacial elastomer with 10% by volume of titanium white dry earth opacifier before and after exposure to microwave energy over a simulated 1.5-year period of microwave sterilization. Materials AND METHODS: A-2186 silicone elastomer opacified with titanium white dry earth pigment, pigmented with 5 cosmetic dry earth pigment colors [no pigment (control) group (Pc), red (Pr), yellow ochre (Py), burnt sienna (Po), and a mixture of Pr + Py + Po color group (P3)], was used in this study. Each of the 5 experimental groups consisted of 5 specimens. All specimens were placed in a 250 ml glass beaker filled with 150 ml of water (replenished for each microwave exposure). An exposure of 6 minutes was used 18 times (simulating 1.5 years of microwave sterilization with one 6 minute exposure monthly). Reflectance values were measured by spectrophotometer. Three- and two-way analyses of variance with repeated measures were performed for the color difference (DeltaE*) with the factors of group/color/months, and group/months, respectively. Means were compared by Tukey Honest Significant Difference (HSD) multiple range test calculated at the 0.05 level of significance using SPSS. RESULTS: The trained human eye can detect color changes (DeltaE*) greater than 1.0. Most DeltaE* values of the red pigment group at all intervals and the mixed pigment group at 15- and 18- month intervals increased significantly greater than 1.0 (p < 0.001) compared with the control group. Yellow and burnt sienna groups remained the most color stable over time with DeltaE* values below 0.35. CONCLUSIONS: Lack of color stability of red dry earth pigmented A-2186 silicone maxillofacial elastomers was clinically significant after 12-month exposure to microwave energy as compared with yellow, burnt sienna, and opacified A-2186 dry earth pigments.  相似文献   
3.
4.
OBJECTIVE: To examine the influence of in-season injury prevention training on hip and knee kinematics during a landing task. DESIGN: Longitudinal pre-post intervention study. SETTING: Testing sessions were conducted in a biomechanics research laboratory. PARTICIPANTS: Eighteen female soccer players between the ages of 14 and 17 participated in this study. All subjects were healthy with no current complaints of lower extremity injury. INTERVENTIONS: Testing sessions were conducted prior to and following a season of soccer practice combined with injury prevention training. MAIN OUTCOME MEASUREMENTS: During each testing session three-dimensional kinematics were collected while each subject performed a drop landing task. Peak hip and knee joint angles were measured during the early deceleration phase of landing and compared between pre- and post-training using paired t-tests. RESULTS: Following a season of soccer practice combined with injury prevention training, females demonstrated significantly less hip internal rotation (7.1 degrees vs. 1.9 degrees; P = 0.01) and significantly greater hip abduction (-4.9 degrees vs. -7.7 degrees; P = 0.02). No differences in knee valgus or knee flexion angles were found post-season. CONCLUSIONS: Female soccer players exhibited significant changes in hip kinematics during a landing task following in-season injury prevention training. Our results support the premise that a season of soccer practice combined with injury prevention training is effective in altering lower extremity motions that may play a role in predisposing females to ACL injury.  相似文献   
5.
6.
7.
Guidelines for design of clinical trials evaluating behavioral headache treatments were developed to facilitate production of quality research evaluating behavioral therapies for management of primary headache disorders. These guidelines were produced by a Workgroup of headache researchers under auspices of the American Headache Society. The guidelines are complementary to and modeled after guidelines for pharmacological trials published by the International Headache Society, but they address methodologic considerations unique to behavioral and other nonpharmacological treatments. Explicit guidelines for evaluating behavioral headache therapies are needed as the optimal methodology for behavioral (and other nonpharmacologic) trials necessarily differs from the preferred methodology for drug trials. In addition, trials comparing and integrating drug and behavioral therapies present methodological challenges not addressed by guidelines for pharmacologic research. These guidelines address patient selection, trial design for behavioral treatments and for comparisons across multiple treatment modalities (eg, behavioral vs pharmacologic), evaluation of results, and research ethics. Although developed specifically for behavioral therapies, the guidelines may apply to the design of clinical trials evaluating many forms of nonpharmacologic therapies for headache.  相似文献   
8.
Volumes of medial and lateral temporal lobe structures were assessed using magnetic resonance imaging (MRI) in 11 patients with late-life onset schizophrenia (LOS), 18 normal elderly controls and 12 patients with moderate cognitive impairment due to Alzheimer's disease (AD) who had no non-cognitive symptoms. While both patient groups has smaller volumes of several medial temporal regions (e.g. entorhinal cortex, left hippocampus), schizophrenics had significantly smaller anterior superior temporal gyri (STG) than normal controls, but AD patients did not. We have previously demonstrated anterior STG volume to be reduced in early life onset schizophrenia.  相似文献   
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