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   2559篇
  免费   145篇
  国内免费   11篇
耳鼻咽喉   12篇
儿科学   187篇
妇产科学   61篇
基础医学   368篇
口腔科学   108篇
临床医学   220篇
内科学   433篇
皮肤病学   129篇
神经病学   241篇
特种医学   70篇
外科学   238篇
综合类   17篇
一般理论   2篇
预防医学   202篇
眼科学   88篇
药学   192篇
中国医学   4篇
肿瘤学   143篇
  2023年   13篇
  2022年   28篇
  2021年   50篇
  2020年   38篇
  2019年   56篇
  2018年   68篇
  2017年   50篇
  2016年   69篇
  2015年   56篇
  2014年   104篇
  2013年   138篇
  2012年   172篇
  2011年   187篇
  2010年   99篇
  2009年   93篇
  2008年   170篇
  2007年   187篇
  2006年   170篇
  2005年   144篇
  2004年   163篇
  2003年   127篇
  2002年   143篇
  2001年   23篇
  2000年   21篇
  1999年   23篇
  1998年   22篇
  1997年   33篇
  1996年   21篇
  1995年   35篇
  1994年   22篇
  1993年   19篇
  1992年   20篇
  1991年   16篇
  1990年   13篇
  1989年   15篇
  1988年   5篇
  1987年   8篇
  1986年   9篇
  1985年   7篇
  1984年   15篇
  1983年   14篇
  1982年   10篇
  1981年   4篇
  1980年   7篇
  1979年   3篇
  1977年   6篇
  1975年   2篇
  1974年   4篇
  1973年   3篇
  1965年   2篇
排序方式: 共有2715条查询结果,搜索用时 0 毫秒
21.
Hepatobiliary cystadenomas and cystadenocarcinomas are rare tumors. Differentiating between these tumors and benign hepatic cysts may be difficult. Because of their rarity, diagnosis is often delayed and may result in inaccurate treatment, resulting in unnecessary morbidity and mortality. The purpose of this report is to draw attention to these entities and their complications. We report on two cases with spontaneous rupture of hepatobiliary cystadenoma and cystadenocarcinoma cysts, initially treated as simple hepatic cysts by aspiration, or by aspiration combined with sclerotherapy. The spontaneous rupture of the cysts appeared years after the initial treatment of the cysts, leading in one case to a prolonged stay in an intensive care unit. In both cases, a formal liver resection was carried out and microscopic investigations revealed a mucinous cystadenocarcinoma and cystadenoma. In conclusion, although hepatobiliary cystadenomas and cystadenocarcinomas are rare findings, they should not be forgotten in the diagnostic workshop when examining patients with hepatic cysts. If hepatobiliary cystadenomas and cystadenocarcinomas cannot be excluded following radiological imaging, surgery is recommended.  相似文献   
22.
We studied the role of endogenous activated protein C (APC), the major physiological anti-coagulant with concomitant anti-inflammatory properties, on ischemia/reperfusion (I/R) in 45 patients participating in a larger trial comparing three immunosuppressive protocols in cadaveric renal transplantation: perioperative anti-thymocyte globulin (ATG, Fresenius AG, Bad Homburg, Germany), perioperative basiliximab and conventional triple therapy. Blood samples for assessing plasma APC, protein C, and lactoferrin concentrations, neutrophil CD11b and L-selectin expressions and blood leukocyte differential counts were obtained preoperatively and before reperfusion from central venous cannula, complemented with simultaneous samples from iliac artery and graft vein for calculation of transrenal differences (Delta) of study parameters at 1 and 5 min after reperfusion. Unlike basiliximab or conventional therapy groups, ATG infusion induced a substantial increase in plasma APC concentration (119 [88-144]% before infusion vs. 232 [85-1246]% after infusion, p<0.001), resulting in renal graft sequestration of APC at 1 min after reperfusion (Delta=-72 [-567 to 12]%, p<0.001). Graft APC consumption was associated with transrenal reduction of neutrophil activation markers (L-selectin r=0.7, p=0.01; lactoferrin r=-0.6, p=0.02; CD11b r=-0.8, p=0.001), and with both warm (r=0.6, p=0.01) and cold ischemia time (r=0.6, p=0.02) and donor age (r=0.6, p=0.01). These findings suggest that APC has an anti-inflammatory role in I/R injury in clinical renal transplantation.  相似文献   
23.

Introduction

Paraesophageal hernia repair is often performed in an elderly population. Few studies have evaluated perioperative mortality in this group. We identified predictors of inpatient mortality using a nationally representative sample.

Methods

Patients ≥80 years old undergoing transabdominal paraesophageal hernia repair were identified in the 2005 Nationwide Inpatient Sample. Congenital diaphragmatic defects and traumatic injuries were excluded.

Results

One thousand five discharges (73% female) with mean age 84.7 met inclusion criteria. Mean length of stay was 10.1 days (95% confidence interval 8.9–11.3) with a mortality of 8.2%. Non-elective repair was performed in 43%. For these patients, mortality and mean length of stay (16%; 14.3 days) were increased compared to elective repair (2.5%; 7.0 days, p?<?0.05). Non-elective repair was the sole predictor of inpatient mortality in adjusted analyses (odds ratio 7.1, 95% confidence interval 1.9–26.3, p?<?0.05).

Conclusion

Non-elective repair was associated with a six to sevenfold increase in mortality and longer length of stay. Earlier elective repair of paraesophageal hernia may reduce mortality.  相似文献   
24.
This study compared the performance of risk adjustment for congenital heart surgery (RACHS-1) score with paediatric risk of mortality (PRISM) score in operative risk prediction after open-heart surgery in children. This was a retrospective analysis of a non-selected patient population from the paediatric intensive care unit of Helsinki University Hospital. All consecutive congenital open-heart surgery patients operated in Finland between the years 2000 and 2004, who were under 18 years of age, were included in this retrospective analysis. Predicted probability of mortality was calculated using the published algorithms for RACHS-1 and PRISM. Those were compared with observed mortality at day 30 postoperatively. Of the 1001 patients, 42 patients died (4.2%) within 30 days of open-heart surgery. The discrimination power, evaluated by AUC (area under curve) for RACHS-1 was moderate: 0.74 (95% CI 0.66-0.82). The AUC-value for PRISM was poor, namely 0.66 (95% CI 0.57-0.75). Both risk scoring systems overestimated the mortality with calculated standardised mortality ratios (SMR) of 0.48 for PRISM and 0.39 for RACHS-1. With only a moderate discriminating AUC, RACHS-1 failed to adequately predict death after paediatric open-heart surgery. The predictive power of PRISM in this patient group was poor. Both scores overestimated the actual mortality rate.  相似文献   
25.
To investigate tissue metabolism during suboptimal blood perfusion, we used in situ microdialysis in an experimental model of myocutaneous flaps. We assessed concentrations of glucose, lactate, and pyruvate in flaps subjected to partial pedicle obstruction and to hemorrhagic shock. When the arterial flow was restricted, the glucose concentration decreased in the flap muscle, and the lactate concentration increased in all flap components. The restriction ofvenous outflow resulted in lactate overproduction and a decrease of glucose in skin and muscle. The lactate-to-pyruvate ratio remained normal during arterial obstruction but increased during venous obstruction. During hypovolemic shock, the lactate production increased and the glucose concentration decreased or remained normal. The metabolic changes occurring during partial pedicle obstruction and hypovolemic shock are moderate and different from those seen in total pedicle obstruction. Microdialysis is a feasible method for assessing local tissue metabolism and can be used to monitor flap ischemia.  相似文献   
26.
OBJECTIVE: To evaluate the peripheral mechanisms of erectile dysfunction (ED) in a rat model of triple-binge cocaine administration. METHODS: Adult male Sprague-Dawley rats (n=24) were divided into two groups: group 1, control rats receiving vehicle (saline); group 2, rats receiving binge cocaine injections. After completion of triple-binge cocaine or saline injections, both groups underwent an in vivo, neurogenic-mediated erectile response protocol to assess intracavernosal pressure (ICP). Penile endothelin-A and -B receptors (ET(A)R and ET(B)R), plasma levels of big endothelin-1 (big-ET-1), and endothelial nitric oxide synthase (eNOS) protein expression were assessed. To analyze nitric oxide (NO) production, we measured plasma nitrate-nitrite levels and quantitated myeloperoxidase (MPO) activity in cavernosal tissues to determine reactive oxygen species generation. Endothelium-dependent and -independent relaxation responses were evaluated in vitro. Data were analyzed with Student t test. RESULTS: Triple-binge cocaine administration caused significantly decreased erectile responses as measured by ICP in vivo. Plasma big-ET-1 levels were significantly increased in the triple-binge cocaine treatment group compared with control animals. In the penis, triple-binge cocaine administration significantly increased ET(A)R expression compared with saline controls, while ET(B)R expression was not altered. Cocaine-treated rats had significantly decreased eNOS expression and NO production. The activity of tissue MPO was significantly increased in the cocaine group compared with control rats. Organ bath studies demonstrated that triple-binge cocaine resulted in a 64% reduction in maximal relaxation compared with the control group. CONCLUSION: This study demonstrates that triple-binge cocaine administration significantly reduces erectile function in rats. The pathophysiologic mechanisms that are likely involved include increased plasma big-ET-1 levels, increased penile ET(A)R expression, increased penile MPO activity, and reduced penile eNOS expression.  相似文献   
27.
OBJECTIVE: A policy of universal leukocyte reduction of the blood supply in Finland was implemented at the beginning of 2003. The aim of the present evaluation was to determine the potential role of leukocyte-reduced red blood cells in decreasing postoperative infections. DESIGN: A retrospective cohort study. SETTING: A major university clinic. PARTICIPANTS: Consecutive patients undergoing cardiac surgery during the years 2002 and 2003. INTERVENTIONS: Transfused patients received either buffy-coat-depleted red blood cells before leukocyte reduction (n = 782) or leukocyte-reduced red blood cells after leukocyte reduction (n = 632). MEASUREMENTS AND MAIN RESULTS: The evaluated outcome parameters were culture-proven postoperative infections, 90-day mortality, and length of stay in the intensive care unit. The percentage of patients transfused with red blood cells (56% v 53%, p = 0.16) and amounts of transfused red blood cells (4.3 +/- 6.7 [3.0] units v 4.3 +/- 6.6 [2.0] units, means +/- standard deviation [median], p = 0.48) were comparable between the study groups (buffy-coat-depleted group and leukocyte-reduced group, respectively). The 90-day mortality (6.6% v 6.3%, p = 0.28), the length of intensive care stay (3.6 +/- 4.7 [2.0] days v 4.3 +/- 7.1 [2.0] days, p = 0.34), and the number of patients with culture-proven infections (8.8% v 10.9%, p = 0.19) were unchanged after universal leukocyte reduction. In multivariate comparisons, the leukocyte reduction was not associated with culture-proven postoperative infections and 90-day mortality. CONCLUSION: No beneficial effect of the universal leukocyte reduction in cardiac surgery was found for culture-positive infection rates, 90-day mortality, or length of intensive care stay.  相似文献   
28.
PURPOSE: We evaluated the effect of spinal cord abnormalities on lower urinary tract function in patients with anorectal abnormalities. MATERIALS AND METHODS: We examined 30 patients with anorectal anomalies mainly because of fecal or urinary incontinence. All patients underwent spinal magnetic resonance imaging and urodynamic investigation. RESULTS: Major lumbosacral abnormalities were detected in 57% of patients, including 13, 4 and 3 with a tethered cord, syringomyelia and caudal regression, respectively. Significant dysfunction of the lower urinary tract in 57% of the cases involved an overactive detrusor in 11, detrusor-sphincter dyssynergia in 4, distended bladder in 4 and lazy bladder in 1. When the spinal cord was normal, 54% of the patients had abnormal urodynamic findings but when the spinal cord was abnormal, 59% had abnormal urodynamics. When the bony spine was normal, 33% of the patients had an abnormal spinal cord but when the bony spine was abnormal, 69% had an abnormal spinal cord. CONCLUSIONS: Patients with anorectal abnormalities and fecal or urinary incontinence problems often have an abnormal spinal cord and abnormal urodynamic findings. However, the state of the spinal cord is not the only factor explaining lower urinary tract function. Thus, the possibility of lower urinary tract dysfunction should be considered in each patient with anorectal abnormalities. If the patient has symptoms or findings suggesting abnormal lower urinary tract function urodynamic evaluation should be performed.  相似文献   
29.

Summary

Peripheral bone strength and fracture risk were studied in young adult Finns. Peripheral bone measures were associated with risk factors of osteoporosis in young adults and discriminated between those with and without low-energy fractures. In men, trabecular bone loss at peripheral bone sites starts before the age of 40 years.

Purpose

This is a cross-sectional study of the determinants of bone strength and fracture risk in young Finns using peripheral quantitative computed tomography (pQCT) and quantitative ultrasound (QUS).

Methods

pQCT scans were performed in 1,884 subjects at distal and shaft sites of non-dominant radius and left tibia, and QUS measures (n?=?1,415) at the left calcaneus. Lifestyle factors and medical conditions affecting bone health were assessed with questionnaires.

Results

In men, the youngest age cohort had the lowest trabecular volumetric bone mineral density (vBMD) at radius and tibia (difference between the youngest and the oldest, 4.4% and 5.6%, respectively, P?<?0.001) and lowest speed of ultrasound at the calcaneus (difference 0.5%, P?=?0.016). In women, bone traits did not differ by age groups. When sexes were pooled, underweight (relative risk (RR)?=?2.95, P?<?0.001), excess alcohol intake (1.52, P?=?0.036), smoking (1.29, P?=?0.025), Crohn’s disease or inflammatory bowel syndrome (2.43, P?=?0.016), epilepsy (2.54, P?=?0.011), use of corticosteroids (2.01, P?<?0.001) and inactivity (1.34, P?=?0.045) increased the risk of low trabecular vBMD. RRs for low-energy fractures were excess alcohol intake (2.58, P?=?<0.001), anorexia (3.74, P?=?0.041) and hypogonadism (2.08, P?=?0.015). Same risk factors predicted BMD and fractures in both sexes. Trabecular bone mineral content, vBMD and bone strength index showed greatest differences (4–9%; P?<?0.05) between those with and without low-energy fractures.

Conclusions

Peripheral QCT traits are associated with common risk factors of osteoporosis in young Finns and discriminate between those with and without low-energy fractures. In men, trabecular bone loss at peripheral bone sites starts before the age of 40 years.  相似文献   
30.
Fifty patients with clefts (30 unilateral cleft lip and palate (UCLP), 9 bilateral cleft lip and palate (BCLP), and 11 cleft palate only (CP), mean age 25 years) treated with Le Fort I osteotomy were compared retrospectively from cephalograms taken shortly before operation, and at six months and one year postoperatively. Patients with bimaxillary surgery or previous velopharyngoplasty, or both, were excluded. Maxillary advancement was moderate in all groups. One year postoperatively there was a significant change (73%–90% of the surgical advancement) in the sagittal depth of the nasopharyngeal airway but not in the depth of the oropharyngeal airway, the length of the soft palate or the position of the hyoid bone. The nasopharyngeal airway was largest in the CP group both preoperatively and postoperatively. Eleven patients (7 CP, 4 UCLP) had a velopharyngoplasty after the osteotomy to improve their speech. There was no difference in the nasopharyngeal airway in the patients treated by velopharyngoplasty compared with those not so treated, but they seemed to have the shortest maxillas and the greatest surgical changes vertically.  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