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   37021篇
  免费   1239篇
  国内免费   282篇
耳鼻咽喉   271篇
儿科学   655篇
妇产科学   414篇
基础医学   4803篇
口腔科学   1008篇
临床医学   2173篇
内科学   9094篇
皮肤病学   867篇
神经病学   2528篇
特种医学   1279篇
外科学   6535篇
综合类   147篇
一般理论   1篇
预防医学   1014篇
眼科学   633篇
药学   2098篇
  5篇
中国医学   124篇
肿瘤学   4893篇
  2024年   139篇
  2023年   249篇
  2022年   543篇
  2021年   935篇
  2020年   551篇
  2019年   769篇
  2018年   854篇
  2017年   657篇
  2016年   779篇
  2015年   804篇
  2014年   1081篇
  2013年   1378篇
  2012年   2238篇
  2011年   2613篇
  2010年   1475篇
  2009年   1215篇
  2008年   2239篇
  2007年   2471篇
  2006年   2314篇
  2005年   2483篇
  2004年   2394篇
  2003年   2395篇
  2002年   2405篇
  2001年   365篇
  2000年   303篇
  1999年   434篇
  1998年   580篇
  1997年   457篇
  1996年   434篇
  1995年   374篇
  1994年   324篇
  1993年   297篇
  1992年   220篇
  1991年   191篇
  1990年   189篇
  1989年   171篇
  1988年   148篇
  1987年   109篇
  1986年   101篇
  1985年   92篇
  1984年   107篇
  1983年   89篇
  1982年   72篇
  1981年   87篇
  1980年   83篇
  1979年   60篇
  1978年   41篇
  1977年   29篇
  1976年   25篇
  1975年   24篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
High-age patients have higher rates of comorbidity that are associated with a poor prognosis. It is important to correctly evaluate their preoperative status to avoid mortality. The aim of this study was to clarify whether the Charlson comorbidity index (CCI) was useful for predicting postoperative outcomes. This retrospective study collected data from 250 consecutive patients over 75 years of age. The CCI takes into account 19 comorbid conditions. Inflammation-based scores, including the Glasgow prognostic score (GPS) and the platelet to lymphocyte ratio (PLR), are other preoperative scoring systems. The relationships among these scores and postoperative outcomes were evaluated. The patients were classified according to their vital status (dead, n = 30 or alive, n = 220). Comorbidities, the presence of double cancer, and lymph node metastases were significantly different between the groups (p < 0.01, p = 0.01, and p < 0.01). In regard to the scoring systems, the CCI, GPS, and PLR were significantly different (p = 0.02, p = 0.03, and p = 0.05). Multivariate analysis identified CCI ≥ 2 (hazard ratio (HR) = 5.24, 95 % confidence interval (CI) = 1.30–12.1, p = 0.01) as a significant determinant of postoperative outcome (p < 0.01). The overall survival tended to be lower in patients with high CCI scores group (p = 0.03). The CCI was useful to predict postoperative outcomes in high-age colorectal cancer patients.  相似文献   
102.
103.
The purpose of this study was to clarify the differences between adolescent and collegiate baseball pitchers in the kinematic and kinetic profiles of the trunk and lower limbs during the pitching motion. The subjects were thirty-two adolescent baseball pitchers aged 12-15 years (APG) and thirty collegiate baseball pitchers aged 18-22 years (CPG). Three-dimensional motion analysis with a comprehensive lower-extremity model was used to evaluate kinematic and kinetic parameters during baseball pitching. The ground reaction forces (GRFs) of the pivot and stride legs during pitching were determined using two multicomponent force plates. The joint torques of hip, knee, and ankle were calculated by the inverse-dynamics computation of musculoskeletal human models using motion-capture data. To eliminate any effect of variation in body size, kinetic and GRFs data were normalized by dividing them by body mass. The velocity of a pitched ball was significantly higher (p < 0.01) in CPG (35.2 ± 1.9 m·s-1) than in the APG (30.7 ± 2.7 m·s-1). Most kinematic parameters for the lower limbs were similar between the CPG and the APG. Maximum Fy (toward the throwing direction) on the pivot leg and Fy and resultant forces on the stride leg at ball release were significantly greater in the CPG than in the APG (p < 0.05). Hip and knee joint torques on the lower limbs were significantly greater in the CPG than in the APG (p < 0.05). The present study indicates that the kinematics of lower limbs during baseball pitching are similar between adolescent and collegiate pitchers, but the momentum of the lower limbs during pitching is lower in adolescent pitchers than in collegiate ones, even when the difference in body mass is considered.

Key points

  • Collegiate baseball pitchers can generate the hip and knee joint torques on the pivot leg for accelerating the body forward.
  • Collegiate baseball pitchers can generate the hip and knee joint torques to control/stabilize the stride leg in order to increase momentum on the stride leg during the arm acceleration phase.
  • The kinematics of the lower limbs during baseball pitching are similar between adolescent and collegiate pitchers, but the momentum of the lower limbs during pitching is lower in adolescent pitchers than in collegiate ones, even when the difference in body mass is considered.
  • Adolescent baseball pitchers cannot generate the hip and knee joint torques in the pivot and stride leg for transfer of the energy of trunk and the arm.
Key words: Pitching ball velocity, the open kinetic chain, joint moment, ground-reaction force, motion analysis  相似文献   
104.
105.
Preconditioning is a preventative approach, whereby minimized insults generate protection against subsequent larger exposures to the same or even different insults. In immune cells, endotoxin preconditioning downregulates the inflammatory response and yet, preserves the ability to contain infections. However, the protective mechanisms of preconditioning at the tissue level in organs such as the kidney remain poorly understood. Here, we show that endotoxin preconditioning confers renal epithelial protection in various models of sepsis in vivo. We also tested the hypothesis that this protection results from direct interactions between the preconditioning dose of endotoxin and the renal tubules. This hypothesis is on the basis of our previous findings that endotoxin toxicity to nonpreconditioned renal tubules was direct and independent of immune cells. Notably, we found that tubular protection after preconditioning has an absolute requirement for CD14-expressing myeloid cells and particularly, macrophages. Additionally, an intact macrophage CD14-TRIF signaling pathway was essential for tubular protection. The preconditioned state was characterized by increased macrophage number and trafficking within the kidney as well as clustering of macrophages around S1 proximal tubules. These macrophages exhibited increased M2 polarization and upregulation of redox and iron-handling molecules. In renal tubules, preconditioning prevented peroxisomal damage and abolished oxidative stress and injury to S2 and S3 tubules. In summary, these data suggest that macrophages are essential mediators of endotoxin preconditioning and required for renal tissue protection. Preconditioning is, therefore, an attractive model to investigate novel protective pathways for the prevention and treatment of sepsis.  相似文献   
106.
107.
108.
109.
110.
A number of remote robotic catheter systems have been developed to protect physicians from X-ray exposure in endovascular surgery. However, the teleoperation prevents the physicians sensing the force directly which may easily result in healthy vessels injured. To realize the safe operation, a tissue protection-based VR training system has been developed in this paper to prevent collateral damage by collision. The integrated VR simulator cannot only remind the novice possible collisions by visual signs, but also cooperate with the newly designed tissue protection mechanism to remit collision trauma beforehand. Such mechanism exploits the diameter variable pulley in order to implement the safe interaction between catheter and vasculature. To testify the effectiveness of the tissue protection in training system, we invited four non-medical students to participate the successive 5 days training session. The evaluation results show that the average impingement distance (representing tissue damage) to vascular wall has been reduced to 0.6 mm, and the collision frequency is greatly decreased which implies the realization of relative safe catheterization.  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