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   1634篇
  免费   107篇
  国内免费   38篇
耳鼻咽喉   4篇
儿科学   66篇
妇产科学   81篇
基础医学   189篇
口腔科学   76篇
临床医学   149篇
内科学   293篇
皮肤病学   128篇
神经病学   82篇
特种医学   122篇
外国民族医学   1篇
外科学   306篇
综合类   5篇
预防医学   78篇
眼科学   26篇
药学   86篇
中国医学   2篇
肿瘤学   85篇
  2022年   13篇
  2021年   44篇
  2020年   26篇
  2019年   25篇
  2018年   45篇
  2017年   44篇
  2016年   25篇
  2015年   52篇
  2014年   54篇
  2013年   62篇
  2012年   85篇
  2011年   93篇
  2010年   63篇
  2009年   60篇
  2008年   72篇
  2007年   88篇
  2006年   79篇
  2005年   53篇
  2004年   56篇
  2003年   58篇
  2002年   73篇
  2001年   34篇
  2000年   50篇
  1999年   32篇
  1998年   39篇
  1997年   48篇
  1996年   39篇
  1995年   27篇
  1994年   18篇
  1993年   16篇
  1992年   24篇
  1991年   19篇
  1990年   29篇
  1989年   26篇
  1988年   20篇
  1987年   7篇
  1986年   28篇
  1985年   13篇
  1984年   11篇
  1983年   16篇
  1982年   6篇
  1981年   8篇
  1980年   7篇
  1979年   10篇
  1978年   8篇
  1977年   12篇
  1976年   6篇
  1975年   4篇
  1973年   8篇
  1972年   12篇
排序方式: 共有1779条查询结果,搜索用时 906 毫秒
61.
62.
63.
64.

Introduction

This in vitro study compared cone-beam computed tomography (CBCT) exam with different voxel sizes with digital periapical radiography in the detection of vertical root fractures in teeth with and without intracanal metallic posts.

Methods

Eighteen single-rooted human teeth were endodontically treated, prepared for cast metal posts, and artificially fractured. After positioning the teeth in dry mandibular sockets, the samples were subjected twice (with and without posts) to digital periapical radiography at 3 different angles and to CBCT examinations with 2 voxel sizes, 0.125 and 0.25 mm. The images were evaluated by 3 oral radiologists. Indices of sensitivity, specificity, and positive and negative predictive values, in addition to the areas under the receiver operating characteristic curves (accuracy), were calculated. Comparison of the accuracy of the imaging methods was assessed by using the χ2 test. Comparison of the accuracy between teeth with and without posts was determined by using the Fisher exact test.

Results

The accuracy of the imaging methods showed no significant differences (P = .08). The comparison between teeth with and without posts in each examination revealed significant differences for CBCT with a voxel of 0.125 mm (P = .04) and for periapical radiography (P = .04).

Conclusions

No significant differences were observed between CBCT and periapical radiography in the detection of vertical root fractures, except for teeth with metallic posts in images from CBCT with a voxel of 0.125 mm and in digital periapical radiography. Furthermore, voxel size did not significantly influence the diagnosis of vertical root fractures.  相似文献   
65.

Introduction

Fine needle aspiration (FNA) is a safe and quick method of diagnosing superficial lumps, which aids preoperative planning. However, FNA of the parotid gland has not gained the widespread acceptance noted in other head and neck lumps. The aim of this study was to determine the ability of FNA of the parotid gland to differentiate benign and malignant disease, and to determine the impact on surgical outcome.

Methods

A retrospective analysis of 201 consecutive parotid operations with preoperative FNA in a large district hospital in the UK was performed. The diagnostic characteristics were calculated for benign and malignant disease, and the impact on surgical procedure was determined.

Results

In identifying benign disease, FNA has a sensitivity of 85% and a specificity of 76%. In detecting malignant disease, FNA has a sensitivity and specificity of 52% and 92% respectively. A false positive on FNA was associated with a higher incidence of neck dissection.

Conclusions

FNA is a useful diagnostic test. However, owing to low sensitivity, it is necessary to interpret it in the context of all other clinical information.  相似文献   
66.
67.
Genetic predisposition to celiac disease (CD) is determined primarily by the human leukocyte antigen (HLA) genes (CELIAC1 region; 6p21), although many loci are involved in disease susceptibility. First, we have analysed a large series of CD patients from the Spanish Mediterranean region who had previously been characterised for the HLA complex. We have investigated how relevant regions contribute to CD susceptibility: CELIAC3 (CD28/CTLA4/ICOS region on 2q33) and CELIAC4 (19p13) as well as the tumour necrosis factor alpha (TNF-alpha) and the linfotoxin loci by case-control and association analyses. We highlight the association with the +49*A allele of cytotoxic T-lymphocyte-associated antigen 4 locus (P = 0.01), and the -308*A of TNF-alpha locus (P = 0.0008) in DQ2 individuals, although an independent role for TNF-alpha as risk factor has not been proven. Moreover, we do not confirm the association with the CELIAC4 region polymorphisms described in other populations.  相似文献   
68.
Intra-operative hypotension is a known predictor of adverse events and poor outcomes following major surgery. Hypotension often occurs on induction of anaesthesia, typically attributed to hypovolaemia and the haemodynamic effects of anaesthetic agents. We assessed the efficacy of fluid optimisation for reducing the incidence of hypotension on induction of anaesthesia. This prospective trial enrolled 283 patients undergoing radical cystectomy and randomly allocated them to goal-directed fluid therapy (n = 142) or standard fluid therapy (n = 141). Goal-directed fluid therapy patients received fluid optimisation based on stroke volume response to passive leg raise before induction; those with positive passive leg raise received intravenous crystalloid fluid boluses until stroke volume was optimised. Baseline mean arterial pressure was measured on the morning of surgery and on arriving in the operating theatre. This post-hoc analysis defined haemodynamic instability as either a > 30% relative drop in mean arterial pressure compared with baseline or absolute mean arterial pressure < 55 mmHg, within 15 min of induction. Forty-two (30%) goal-directed fluid therapy patients underwent fluid optimisation after finding an intravascular fluid deficit via passive leg raise testing; 106 (75%) goal-directed fluid therapy and 112 (79%) standard fluid therapy patients met criteria for haemodynamic instability. There was no significant difference in the incidence of haemodynamic instability between the goal-directed fluid therapy and standard fluid therapy groups using absolute mean arterial pressure drop below 55 mmHg (p = 0.58) or using pre-surgical testing or pre-surgical mean arterial pressure values as baseline (p = 0.21, p = 0.89, respectively); however, the difference in the incidence of haemodynamic instability was significant using the operating theatre baseline mean arterial pressure (p = 0.004). We conclude that fluid optimisation before induction of general anaesthesia did not significantly impact haemodynamic instability.  相似文献   
69.
OBJECTIVE: The aim of the study was to assess whether coadministration of S(+) ketamine or ketorolac would enhance or prolong local analgesic effect of bupivacaine after inguinal hernia repair. DESIGN: Prospective double-blind randomized study evaluating pain intensity after surgery under general anesthesia. SETTING: Outpatient facilities of the University Hospital of Lausanne. PATIENT: Thirty-six ASA I-II outpatients scheduled for elective day-case inguinal herniorraphy. INTERVENTION: Analgesia strategy consisted of a wound infiltration and an inguinal field block either with 30 mL bupivacaine (0.5%) or with the same volume of a mixture of 27 mL bupivacaine (0.5%) + 3 mL S(+) ketamine (75 mg) or a 28 mL bupivacaine (0.5%) + 2 mL ketorolac (60 mg). Postoperative analgesic regimen was standardized. OUTCOME MEASURES: Pain intensity was assessed with a Visual Analog Scale, a verbal rating score, and by pressure algometry 2, 4, 6, 24, and 48 hours after surgery. RESULTS: The 3 groups of patients experienced the highest Visual Analog Scale pain score at 24 hours, which was different from those at 6 and 48 hours (P < 0.05). Apart from a significantly lower pain sensation (verbal rating score) in the ketorolac group at 24 and 48 hours and only at 48 hours with ketamine, there were no other differences in pain scores, pain pressure thresholds, or rescue analgesic consumption between groups throughout the 48-hour study period. CONCLUSION: The addition of S(+)-ketamine or ketorolac only minimally improves the analgesic effect of bupivacaine. This may be related to the tension-free hernia repair technique associated with low postoperative pain.  相似文献   
70.
ObjectivesSurveillance after radical cystectomy is recommended to detect tumor recurrence and treatment complications. We evaluated adherence to National Comprehensive Cancer Network (NCCN) guidelines using a large population-based database.Methods and materialsThe Surveillance, Epidemiology, and End Results–Medicare database was used to identify patients aged ≥66 years diagnosed with nonmetastatic bladder cancer who had undergone radical cystectomy between 2000 and 2007. Medicare claims information identified recommended surveillance tests for 2 years after cystectomy as outlined in the NCCN guidelines. Adherence was defined as receipt of urine cytology and imaging of the chest, abdomen, and pelvis in each year. We evaluated the effect of patient and provider characteristics on adherence, controlling for demographic and disease characteristics.ResultsOf 3,757 patients who had undergone radical cystectomy, 2,990 (80%) were alive after 2 years. Adherence to all recommended investigations was 17% for the first and the second years following surgery. Among patients surviving 2 years, only 9% had complete surveillance in both years. In either year, adherence was less likely in patients with advanced pathologic stage (III/IV) (adjusted odds ratio [AOR] = 0.74, 95% CI: 0.60–0.91) and unmarried patients (AOR = 0.82, 95% CI: 0.68–0.99). Adherence was more likely in patients treated by high-volume surgeons (AOR = 2.00, 95% CI: 1.70–2.36) and those who saw a medical oncologist (AOR = 1.52, 95% CI: 1.27–1.82). We also observed significant geographic variability in adherence.ConclusionPatterns of surveillance after radical cystectomy deviate considerably from NCCN recommendations. Despite increased utilization of radiographic imaging investigations, the omission of urine cytology significantly contributed to the low rate of overall adherence to surveillance guidelines. Uniform adherence to surveillance guidelines was observed in patients treated by high-volume surgeons. This suggests an important opportunity for quality improvement in bladder cancer care.  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