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   4896篇
  免费   298篇
  国内免费   22篇
耳鼻咽喉   76篇
儿科学   112篇
妇产科学   67篇
基础医学   746篇
口腔科学   91篇
临床医学   461篇
内科学   1044篇
皮肤病学   68篇
神经病学   363篇
特种医学   192篇
外科学   897篇
综合类   66篇
一般理论   5篇
预防医学   310篇
眼科学   78篇
药学   293篇
中国医学   8篇
肿瘤学   339篇
  2023年   19篇
  2022年   41篇
  2021年   85篇
  2020年   69篇
  2019年   82篇
  2018年   71篇
  2017年   76篇
  2016年   88篇
  2015年   89篇
  2014年   130篇
  2013年   218篇
  2012年   260篇
  2011年   312篇
  2010年   176篇
  2009年   173篇
  2008年   319篇
  2007年   311篇
  2006年   311篇
  2005年   305篇
  2004年   303篇
  2003年   296篇
  2002年   273篇
  2001年   63篇
  2000年   59篇
  1999年   60篇
  1998年   63篇
  1997年   56篇
  1996年   52篇
  1995年   53篇
  1994年   47篇
  1993年   38篇
  1992年   54篇
  1991年   46篇
  1990年   50篇
  1989年   50篇
  1988年   43篇
  1987年   40篇
  1986年   37篇
  1985年   35篇
  1984年   35篇
  1983年   29篇
  1982年   21篇
  1981年   25篇
  1980年   22篇
  1979年   17篇
  1978年   21篇
  1976年   13篇
  1975年   15篇
  1974年   14篇
  1973年   22篇
排序方式: 共有5216条查询结果,搜索用时 15 毫秒
81.
BACKGROUND: Infectious diseases are among the most morbid events in uremia. The uremic toxin p-cresol may play a role in the immunodeficiency of uremia by depressing phagocyte functional capacity. Leukocyte adhesion to endothelium, a key event in the immune response, is mediated by endothelial adhesion molecules. These include intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1) and E-selectin, which are induced by various inflammatory cytokines. We asked whether p-cresol alters endothelial adhesion molecule expression and modifies endothelial/leukocyte adhesion. METHODS: Human umbilical vein endothelial cells (HUVEC) were incubated with p-cresol in the presence or absence of tumor necrosis factor (TNF) or interleukin-1beta (IL-1beta). Thereafter, the endothelial molecules ICAM-1, VCAM-1, and E-selectin were quantitated and the monocyte (THP-1) adhesion to HUVEC measured. RESULTS: P-cresol decreased cytokine-induced protein and mRNA expression of ICAM-1 and VCAM-1. In addition, p-cresol significantly decreased the adhesion of THP-1 to cytokine-stimulated HUVEC. CONCLUSIONS: P-cresol may play a role in the immune defect of uremic patients by inhibiting cytokine-induced endothelial adhesion molecule expression and endothelium/monocyte adhesion.  相似文献   
82.

Objective

Patients with end-stage renal disease have multiple comorbidities and are at increased risk for postoperative complications and resource utilization. Our goal was to determine the rate and causes of 30-day and 90-day hospital readmissions after the creation of outpatient hemodialysis access.

Methods

We retrospectively reviewed all outpatient upper extremity hemodialysis access creations performed at our medical center from 2008 to 2015. Readmission was defined as any inpatient status admission ≤30 and 90 days. Reasons for such admissions were analyzed, and multivariate analyses assessed risk factors.

Results

We identified 537 patients (60% male). Average age was 59 years. Access type included radiocephalic (4.5%), brachiocephalic (50.7%), brachiobasilic (22.5%), and prosthetic (20%) arteriovenous fistulas. The 90-day mortality rate was 0.7%. Postoperative hospital readmission rates were 25.5% at 30 days and 47.7% at 90 days. Reasons for admission were access related in 10.9% and dialysis catheter related in 6.9%. Other reasons for admission included shortness of breath/volume overload (15.8%), gastrointestinal (11.9%), cardiac/chest pain (10.9%), unrelated infectious causes (11.9%), failure to thrive (5%), altered mental status (4%), electrolyte abnormalities (3%), and musculoskeletal (2.5%). Preoperative predictors of all cause 30-day readmission included dementia (odds ratio [OR], 5.76; 95% confidence interval [CI], 1.34-24.8; P = .018), hypertension (OR, 3.92; 95% CI, 1.07-14.4; P = .039), chronic obstructive pulmonary disease (OR, 2.19; 95% CI, 1.01-4.76; P = .046), and current smoking (OR, 2.14; 95% CI, 1.32-3.47; P = .002). Predictors of all cause 90-day readmission were hepatic insufficiency (OR, 6.08; 95% CI, 1.2-30.8; P = .029), hypertension (OR, 3.43; 95% CI, 1.36-8.65; P = .009), black race (OR, 2.47; 95% CI, 1.48-4.14; P = .001), Hispanic ethnicity (OR, 2.04; 95% CI, 1.01-4.11; P = .046), and obesity (OR, 1.5; 95% CI, 1.02-2.19; P = .039). Predictors of 90-day access-related readmission included chronic obstructive pulmonary disease (OR, 5.27; 95% CI, 1.38-20.0; P = .015), previous stroke (OR, 3.76; 95% CI, 1.5-9.4; P = .005), being on dialysis at time of the operation (OR, 2.8; 95% CI, 1.17-6.84; P = .022), and prosthetic graft placement (OR, 2.86; 95% CI, 1.07-7.6; P = .036). An additional 9.7% had at least one emergency department presentation ≤90 days but were not admitted.

Conclusions

Patients undergoing placement of hemodialysis access are at high risk for readmission mostly from causes unrelated to their operation. This has an effect for global care for these patients as well as care of these patients in accountable care organizations.  相似文献   
83.
The optimal dose of vitamin D to optimize bone metabolism in the elderly is unclear. We tested the hypothesis that vitamin D, at a dose higher than recommended by the Institute of Medicine (IOM), has a beneficial effect on bone remodeling and mass. In this double‐blind trial we randomized 257 overweight elderly subjects to receive 1000 mg of elemental calcium citrate/day, and the daily equivalent of 3750 IU/day or 600 IU/day of vitamin D3 for 1 year. The subjects’ mean age was 71 ± 4 years, body mass index 30 ± 4 kg/m2, 55% were women, and 222 completed the 12‐month follow‐up. Mean serum 25 hydroxyvitamin D (25OHD) was 20 ng/mL, and rose to 26 ng/mL in the low‐dose arm, and 36 ng/mL in the high‐dose arm, at 1 year (p < 0.05). Plasma parathyroid hormone, osteocalcin, and C‐terminal telopeptide (Cross Laps) levels decreased significantly by 20% to 22% in both arms, but there were no differences between the two groups for any variable, at 6 or 12 months, with the exception of serum calcitriol, which was higher in the high‐dose group at 12 months. Bone mineral density (BMD) increased significantly at the total hip and lumbar spine, but not the femoral neck, in both study arms, whereas subtotal body BMD increased in the high‐dose group only, at 1 year. However, there were no significant differences in percent change BMD between the two study arms at any skeletal site. Subjects with serum 25OHD <20 ng/mL and PTH level >76 pg/mL showed a trend for higher BMD increments at all skeletal sites, in the high‐dose group, that reached significance at the hip. Adverse events were comparable in the two study arms. This controlled trial shows little additional benefit in vitamin D supplementation at a dose exceeding the IOM recommendation of 600 IU/day on BMD and bone markers, in overweight elderly individuals. © 2017 American Society for Bone and Mineral Research.  相似文献   
84.
Paediatric complex wounds pose a challenge to the reconstructive surgeon due to the intricacy of reconstructive options required. Developments in microsurgery and microsurgical technique have brought free tissue transfer ever closer to the comfort zone of the reconstructive surgeon for reconstruction of paediatric traumatic complex wounds. We present our experience of microsurgical reconstruction in Lebanon for complex traumatic wounds in paediatric patients under the age of 10 years using the free anterolateral thigh (ALT) flap. The ALT flap has proven its value as a safe, adaptable, and aesthetically acceptable reconstructive option in paediatric complex trauma.  相似文献   
85.
BACKGROUND/PURPOSE: Children with gastroesophageal reflux disease (GERD) often have associated feeding difficulties that warrant the insertion of a feeding gastrostomy at the time of the antireflux procedure. Options for gastrostomy tube insertion at the time of laparoscopic Nissen fundoplication (LNF) include laparoscopic gastrostomy, percutaneous endoscopic gastrostomy (PEG), and classic open gastrostomy. The complication rate of PEG may be decreased if it is placed under laparoscopic supervision. The purpose of this paper is to describe our experience with laparoscopically supervised PEG tube placement at the time of antireflux procedure. METHODS: A retrospective chart review was conducted on all children undergoing a PEG tube placement at the time of the LNF. Perioperative complications were recorded. RESULTS: Forty-four patients had attempted PEG tube placement at the time of the LNF. In 3 (7%) cases, laparoscopic supervision was crucial in the prevention of a complication. No major PEG-related complications were recorded. In 43% of patients, minor PEG tube problems arose in the postoperative period: all were transient and/or easily correctable. Management of all these problems was in an outpatient setting. Follow-up ranged from 11 to 41 months. CONCLUSIONS: PEG tube placement at the time of a LNF is safe and effective. A combined laparoscopic and endoscopic approach minimizes complications. This method also allows for an intra- and extraluminal evaluation of the fundoplication at its completion.  相似文献   
86.
87.

OBJECTIVES

To determine the technical feasibility and reproducibility of pure natural orifice transluminal endoscopic surgery (NOTES) transvaginal nephrectomy using NOTES‐specific instrumentation, with no transabdominal assistance.

MATERIALS AND METHODS

Five female farm pigs (mean weight 45 kg) had a right NOTES nephrectomy, using a single‐channel gastroscope in the first three pigs and a dual‐channel gastroscope in the remaining two. The peritoneal cavity was accessed through the posterior fornix of the vagina. Dissection was started at the lower pole of the kidney, and the ureter was retracted laterally and followed towards the hilum. An XL articulated 60 cm endo‐GIA stapler (US Surgical, Norwalk, CO, USA), inserted transvaginally via a separate vaginal incision, was used for tissue retraction and renal hilar transection. The kidney was freed, entrapped in an impermeable sac, and extracted intact transvaginally.

RESULTS

All five procedures were successful with no addition of a transabdominal laparoscopic port or open conversion. The total operative duration decreased from 200 min in the first pig to 60 min in the last (mean 113 min); the mean blood loss was <50 mL, the mean kidney length was 13.9 cm and the weight was 142 g. There were no intraoperative complications; at autopsy, there was no pelvic or bowel injury.

CONCLUSIONS

Pure NOTES transvaginal nephrectomy is feasible in the porcine model. It has the potential of a less morbid approach, providing truly scar‐less surgery. Further development of instrumentation is necessary.  相似文献   
88.

Background

Limited prospective data on the anatomic and functional outcome after laparoscopic sacrocolpopexy (LSC) are available in the literature.

Objective

To describe the medium-term anatomic and functional outcome of LSC.

Design, setting, and participants

Prospective consecutive series of 132 women with vaginal vault prolapse undergoing LSC between 2001 and 2006, which was after our learning curve. Patients with urodynamically proven stress incontinence (SI) underwent a concomitant tension-free vaginal tape (TVT) procedure.

Intervention

Patients underwent LSC with a polypropylene implant.

Measurements

Principal outcome measures were anatomic cure (stage 1 or lower) assessed by the Pelvic Organ Prolapse Quantification (POPQ) system and subjective cure and impact on quality of life measured by a standardised interview and, since its introduction in 2004, by a prolapse-specific quality-of-life questionnaire (P-QOL).

Results and limitations

At a mean follow-up of 12.5 mo, the anatomic cure rate for the apex was 98%. Anatomic failures elsewhere were mainly at the posterior compartment (18%). Subjective prolapse cure rate was 91.7%, and no patients required reoperation for recurrent prolapse. Symptoms of preoperative SI, urge incontinence, or constipation were cured in 43%, 46%, and 42% of patients, respectively. The rate of de novo SI was 7.3%. De novo constipation developed in 5% and de novo dyspareunia developed in 19%. Patients’ quality of life improved significantly. Erosions occurred in 4.5%, all within 1 yr. A limitation of the study is that the quality-of-life assessment score became available halfway through the study, limiting the number of preoperative observations (n = 36).

Conclusions

We demonstrated that LSC results in good anatomic outcome and subjective cure of prolapse symptoms at medium term. The posterior compartment was most vulnerable for recurrence.  相似文献   
89.
Prenatal forms of autosomal dominant polycystic kidney disease (ADPKD) are rare but can be recurrent in some families, suggesting a common genetic modifying background. Few patients have been reported carrying, in addition to the familial mutation, variation(s) in polycystic kidney disease 1 (PKD1) or HNF1 homeobox B (HNF1B), inherited from the unaffected parent, or biallelic polycystic kidney and hepatic disease 1 (PKHD1) mutations. To assess the frequency of additional variations in PKD1, PKD2, HNF1B, and PKHD1 associated with the familial PKD mutation in early ADPKD, these four genes were screened in 42 patients with early ADPKD in 41 families. Two patients were associated with de novo PKD1 mutations. Forty patients occurred in 39 families with known ADPKD and were associated with PKD1 mutation in 36 families and with PKD2 mutation in two families (no mutation identified in one family). Additional PKD variation(s) (inherited from the unaffected parent when tested) were identified in 15 of 42 patients (37.2%), whereas these variations were observed in 25 of 174 (14.4%, P=0.001) patients with adult ADPKD. No HNF1B variations or PKHD1 biallelic mutations were identified. These results suggest that, at least in some patients, the severity of the cystic disease is inversely correlated with the level of polycystin 1 function.  相似文献   
90.
OBJECTIVE: Dobutamine is commonly used to improve ventricular performance in cardiac surgery. The aim of this prospective randomised controlled study was to assess the effectiveness of using low doses of dobutamine during off-pump coronary artery bypass (OPCAB) surgery in order to reduce haemodynamic compromise due to heart displacement. METHODS: Thirty-two patients undergoing elective coronary artery bypass grafting (CABG) surgery using OPCAB technique for more than two vessels were approached and recruited. We analysed the changes in the thoracic aortic blood flow (TABF) during OPCAB using transoesophageal Doppler and by other conventional monitoring methods as cardiac output, invasive pulmonary and radial pressures and mixed venous oxygen saturation. RESULTS: The two groups were similar in preoperative characteristics. No postoperative complications were observed in the study patients. The heart rate, right atrial pressure, cardiac output measured by thermodilution and TABF changed significantly during the procedure. Also significant changes in descending thoracic aortic diameter were observed. The postoperative creatinine was significantly lower in the dobutamine group (P=0.04). Dobutamine was found responsible for the improvement in the descending TABF (P=0.006). CONCLUSIONS: This study showed that intra-operative intravenous infusion of dobutamine at 5 microg/kg per min in routine OPCAB patients safely increased cardiac output even without such changes been detected by conventional monitoring methods.  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