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   35282篇
  免费   2222篇
  国内免费   204篇
耳鼻咽喉   325篇
儿科学   593篇
妇产科学   465篇
基础医学   4935篇
口腔科学   924篇
临床医学   3688篇
内科学   7436篇
皮肤病学   681篇
神经病学   3876篇
特种医学   2048篇
外国民族医学   1篇
外科学   5649篇
综合类   198篇
一般理论   10篇
预防医学   1531篇
眼科学   737篇
药学   2066篇
中国医学   69篇
肿瘤学   2476篇
  2024年   28篇
  2023年   271篇
  2022年   525篇
  2021年   905篇
  2020年   641篇
  2019年   832篇
  2018年   955篇
  2017年   832篇
  2016年   952篇
  2015年   1157篇
  2014年   1397篇
  2013年   1704篇
  2012年   2754篇
  2011年   2875篇
  2010年   1724篇
  2009年   1539篇
  2008年   2440篇
  2007年   2438篇
  2006年   2286篇
  2005年   2247篇
  2004年   2006篇
  2003年   1850篇
  2002年   1704篇
  2001年   357篇
  2000年   260篇
  1999年   320篇
  1998年   333篇
  1997年   256篇
  1996年   204篇
  1995年   178篇
  1994年   147篇
  1993年   141篇
  1992年   122篇
  1991年   107篇
  1990年   117篇
  1989年   87篇
  1988年   89篇
  1987年   68篇
  1986年   70篇
  1985年   77篇
  1984年   79篇
  1983年   74篇
  1982年   57篇
  1981年   48篇
  1980年   42篇
  1979年   41篇
  1978年   26篇
  1977年   25篇
  1975年   26篇
  1974年   35篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
21.
Background: Neuraxial blockade is used as primary anesthetic technique in one third of surgical procedures. The authors tested whether bisoprolol would protect patients at risk for cardiovascular complications undergoing surgery with spinal block.

Methods: The authors performed a double-blinded, placebo-controlled, multicenter trial to compare the effect of bisoprolol with that of placebo on 1-yr composite outcome including cardiovascular mortality, nonfatal myocardial infarction, unstable angina, congestive heart failure, and cerebrovascular insult. Bisoprolol was given orally before and after surgery for a maximum of 10 days. Adrenergic receptor polymorphisms and safety outcome measures of bisoprolol therapy were also determined.

Results: A total of 224 patients were enrolled. Spinal block could not be established in 5 patients. One hundred ten patients were assigned to the bisoprolol group, and 109 patients were assigned to the placebo group. The mean duration of treatment was 4.9 days in the bisoprolol group and 5.1 days in the placebo group. Bisoprolol therapy reduced mean heart rate by 10 beats/min. The primary outcome was identical between treatment groups and occurred in 25 patients (22.7%) in the bisoprolol group and 24 patients (22.0%) in the placebo group during the 1-yr follow-up (hazard ratio, 0.97; 95% confidence interval, 0.55-1.69; P = 0.90). However, carriers of at least one Gly allele of the [beta]1-adrenergic receptor polymorphism Arg389Gly showed a higher number of adverse events than Arg homozygous (32.4% vs. 18.7%; hazard ratio, 1.87; 95% confidence interval, 1.04-3.35; P = 0.04).  相似文献   

22.
PURPOSE: To present a case of laryngeal damage in an infant caused by a too large and inappropriately designed cuffed tracheal tube. CLINICAL FEATURES: A 13-month-old child undergoing cardiac surgery was intubated with an uncuffed endotracheal tube with an internal diameter (ID) of 4.0 mm. Because of an important air leak around the tracheal tube during mechanical ventilation, a cuffed endotracheal tube ID 4.0 mm was inserted. The air leak with the tube cuff not inflated was acceptable at 25 cm H2O airway pressure. After extubation on the third postoperative day, the patient showed increasing stridor and respiratory deterioration. Fibreoptic laryngoscopy of the spontaneously breathing patient showed a large intra-laryngeal web. After surgical removal of the web, the child rapidly recovered and was discharged from the hospital on the 12th postoperative day. Inspection of the 4.0 mm (ID) cuffed tracheal tube revealed a cuff positioned inappropriately high and an increase of 0.7 mm in outer tube diameter compared to the 4.0 mm (ID) uncuffed tracheal tube from the same manufacturer. The tube cuff is likely to be situated within the larynx when placed in accordance to insertion depth formulas or radiological criteria, as used for uncuffed tracheal tubes in children. CONCLUSION: The larger than expected tracheal tube with its intra-laryngeal cuff position in a 13-month-old child likely caused mucosal damage and an inflammatory reaction within the larynx resulting in granulation tissue formation and fibrous healing around the tracheal tube.  相似文献   
23.
24.
We report a case of recurrent inguinal lymphocele formation after inguinal lymphadenectomy treated by lymphographic mapping and selective ligation of the lymphatic vessels. Lymphographic mapping was performed by puncturing a lymphatic vessel at the dorsum of the foot. After isolating the vessels that drained into the lymphocele, they were clipped and divided through a small skin incision. The described technique showed an instant and complete suspension of the lymph secretion with subsequent complete healing. Lymphatic mapping and selective ligation of afferent lymphatic vessels proved to be an effective treatment of a recurrent inguinal lymphocele.  相似文献   
25.
The synthesis and properties of segmented ABA triblock and (AB)n multiblock copolymer systems with 6,6′-disubstituted 2,2′-bipyridine (bpy) building blocks B and poly(oxytetramethylene) soft segments A are described. The access to the disubstituted bipyridines in large scale quantities was achieved by modification of conventional synthetic routes. In the presence of copper(I) ions these polymers formed mononuclear [Cu(I)(bpy)2] complexes in solution through self-assembly. The complexed copolymers were microphase separated systems in bulk with nano to mesoscopic superstructures consisting of copper-bpy complex aggregates in a polyether matrix. The thermal, mechanical and elastomer properties of the block copolymers varied with composition.  相似文献   
26.
We wanted to clarify whether the postprandial intestinal feedback control activated by nutrients in the distal gut exerts different effects on motility, transit of digesta, and absorption of nutrients in the proximal gut. Additionally, interrelationships among motility, transit, and absorption were to be elucidated because these relationships have only been investigated in the fasted state. In five minipigs, a 150-cm segment of the proximal jejunum was isolated by two cannulas. Motility of the jejunal segment was recorded by multiple strain gauges and analyzed by computerized methods. Markers (Cr- and Cu-EDTA) were used for the measurement of the flow rate, transit time, and absorption of nutrients. After a meal, the test segment was perfused with 2 kcal/min of an elemental diet over a period of 90 min. A feedback inhibition was activated by infusion of nutrients into the midgut at rates of 1–4 kcal/min. Saline was infused as control. With increasing energy loads infused into the midgut, the motility index and the length of contraction waves decreased, whereas the incidence of stationary contractions increased, ie, the motility changed from a propulsive to a segmenting pattern. These modulations of motility were associated with a linear decrease in the flow rate and a linear increase in transit time. Flow and transit were linearly correlated with each other. Additionally, the reduction in flow rate and the delay in luminal transit were associated with a linear increase in the absorption of nutrients. However, the increase in absorption induced by the feedback mechanism was small (7.3–13.4%) compared to the marked inhibition of the motility parameters (54–64%), the flow rate (59%), and the delay of transit (5.8-fold). Feedback control primarily modulated motor patterns and luminal flow, whereas the small increase in absorption was only a side effect due to the longer contact time of the nutrients with the mucosa.The study was supported by the Deutsche Forschungsgemeinschaft, grant Eh 64/6-3.  相似文献   
27.
Urinary oxalate and glycolate excretion in healthy infants and children   总被引:2,自引:0,他引:2  
The molar ratios of oxalate and glycolate over creatinine were determined in single urine samples of 26 infants and 27 children aged 1–5 years. In 135 children aged 5–16 years, two urine specimens were collected, one before breakfast and one at noon. Oxalate was determined by oxalate oxidase, and glycolate was measured by a colorimetric method (improved chromatotropic acid-sulphuric acid assay after prior purification by cation and anion exchanger). Both ratios (expressed in mmol/mol creatinine and analysed on a log-normal basis) were highest in infants 0–6 months old [mean oxalate 147 (95% confidence interval: 60–360), mean glycolate 175 (72–425)]. The mean oxalate ratio was 72 mmol/mol (29–174) at the age of 7–24 months, 44 (19–101) at the age of 2–5 years and 22 (12–40) in adolescents aged 16 years. Molar glycolate ratios were higher, but disclosed the same pattern. Oxalate and glycolate ratios in fasting urines did not differ significantly from those in noon samples (except glycolate in the oldest age group). Oxalate ratios correlated well with glycolate ratios in children up to 5 years of age only. Random urine samples are thus suitable for screening. However, interpretation of data requires use of age-specific reference values that are based on comparable methods.  相似文献   
28.
Abstract Purpose: Evaluation of the therapeutic usefulness of the “pelvic C–clamp” (PCC) during emergency treatment of multiply injured patients with unstable disruption of the posterior pelvic ring. Patients and Methods: The data of 28 patients with polytrauma in combination with an unstable fracture of the posterior pelvic ring (average Injury Severity Score [ISS]: 49 points; average Polytrauma Score [PTS]: 41 points) were retrospectively analyzed from the moment they were admitted to the emergency room until 48 h after admittance. The PCC was used immediately for primary stabilization of the pelvis after clinical diagnosis of the unstable pelvic fracture. Main outcome measurements: development of mean blood pressure, development of oxygenation level, period of time until the PCC was placed, number of blood units needed, period of time until circulatory stabilization occurred. Results: The PCC was applied in all cases within an average of 64.7 min after trauma. Seven patients (25%) died within the first 45 min after admission. The surviving patients showed:• an increase in mean blood pressure of 25% 20 min after application of the PCC,• a hemodynamic stabilization 6 h after application of the PCC,• a stabilization of the oxygenation level 6 h after application of the PCC,• a decrease in the number of required blood units 6 h after application of the PCC. Conclusion: The present study shows, that the application of the PCC to critically injured patients with unstable pelvic fractures leads to stabilization of the vital parameters within a short period of time.  相似文献   
29.
30.
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