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   48937篇
  免费   2587篇
  国内免费   139篇
耳鼻咽喉   685篇
儿科学   978篇
妇产科学   1083篇
基础医学   6279篇
口腔科学   2397篇
临床医学   3779篇
内科学   12472篇
皮肤病学   894篇
神经病学   4182篇
特种医学   925篇
外科学   6356篇
综合类   255篇
一般理论   17篇
预防医学   4148篇
眼科学   1046篇
药学   3331篇
中国医学   190篇
肿瘤学   2646篇
  2024年   26篇
  2023年   305篇
  2022年   266篇
  2021年   968篇
  2020年   535篇
  2019年   1078篇
  2018年   1881篇
  2017年   1190篇
  2016年   1195篇
  2015年   1489篇
  2014年   1640篇
  2013年   2363篇
  2012年   4409篇
  2011年   4504篇
  2010年   2367篇
  2009年   1732篇
  2008年   3738篇
  2007年   3827篇
  2006年   3703篇
  2005年   3528篇
  2004年   3084篇
  2003年   2833篇
  2002年   2622篇
  2001年   210篇
  2000年   161篇
  1999年   182篇
  1998年   168篇
  1997年   150篇
  1996年   136篇
  1995年   118篇
  1994年   97篇
  1993年   96篇
  1992年   94篇
  1991年   88篇
  1990年   54篇
  1989年   57篇
  1988年   39篇
  1987年   31篇
  1986年   35篇
  1985年   44篇
  1984年   60篇
  1983年   39篇
  1982年   62篇
  1981年   44篇
  1980年   55篇
  1978年   26篇
  1977年   20篇
  1976年   22篇
  1975年   23篇
  1974年   33篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
961.
BACKGROUND AND OBJECTIVES: In vitro studies have shown that the rate of prothrombin activation is linearly related to the concentration of factor II (FII) in the assay system, suggesting a key role of prothrombin levels in the expression of the antithrombotic activity of oral anticoagulant treatment (OAT). We investigated the in vivo relationship between prothrombin activation and vitamin K-dependent clotting factor levels during the early and steady phases of OAT in patients and in healthy volunteers. DESIGN AND METHODS: The changes in international normalizezd ratio (INR) and in the plasma levels of FVII, FX, FII, protein C (PC) and prothrombin fragment 1.2 (F1+2) induced by OAT were monitored over 9 days in 10 patients not on heparin starting warfarin after heart valve replacement (HVR) and in 9 healthy volunteers submitted to an 8-day course of warfarin treatment. FII and F1+2 plasma levels were also measured in 100 patients on stable oral anticoagulant treatment with INRs ranging from 1.2 to 6.84. RESULTS: Because HVR patients had subnormal FVII, FX and FII levels after surgery, INR values > 2.0 were attained already 24 hours after the first warfarin dose. In healthy volunteers, INR values greater than 2.0 were first observed after 72 hours. Nadir levels of FVII, PC, FX and FII were reached between 40 and 88 hours in HVR patients and between 72 and 192 hours in healthy volunteers. The FII apparent half-disappearance time (t/2) was 99 hours in HVR patients and 115 hours in healthy volunteers (p = ns). In HVR patients there was no normalization of initially elevated F1+2 levels until day 7 with an apparent t/2 of 132 hours. In healthy volunteers, a decrease to subnormal F1+2 levels was observed by day 8 of treatment (apparent t/2 = 107 hours). In both HVR patients and healthy volunteers, FII and PC levels were independent predictors of the changes in F1+2 levels (p = 0.0001). In patients on stable OAT, only FII levels were independent predictors of the variation in F1+2 levels (p = 0.0001). INTERPRETATION AND CONCLUSIONS: During the early phase of oral anticoagulant treatment in vivo prothrombin activation is a function of the balance between FII and PC levels and is not significantly prevented until nadir levels of FII are obtained. This provides an explanation for the requirement of overlapping heparin and oral anticoagulant treatment for at least 48 hours after the achievement of therapeutic INR values in patients with thromboembolic diseases. In addition, in vivo prothrombin activation is a function of FII levels rather than INR values also in patients on stable oral anticoagulant treatment.  相似文献   
962.
Endothelin has been identified as a potent vasoconstrictor. The aim of this study was to evaluate urinary endothelins and their relation to other markers of renal damage, such as microalbuminuria, creatinine, and N-acetyl-beta-glucosaminidase (NAG), in a group of recently diagnosed (less than 1 year) hypertensive subjects and a control group. We selected 50 subjects and divided them into two groups: 27 hypertensive patients (15 females and 12 males) without previous pharmacologic therapy, and 23 healthy, normotensive subjects (12 females and 11 males). All patients underwent a history and physical examination, chest x-ray, electrocardiography, funduscopy, and hematologic and biochemical analyses. Endothelins, microalbuminuria, creatinine, and NAG values were also determined in 24-hour urine samples. Creatinine, microalbuminuria, and NAG values were found to be higher in hypertensive than in normotensive subjects. The hypertensive group showed a nonsignificant elevation of total endothelin. In conclusion, the determination of elevated urinary endothelin does not appear to be an early marker of organ damage in hypertensive subjects. The urinary excretion of protein, creatinine, and NAG was higher in hypertensive subjects. A positive correlation was found between the urinary excretion of endothelins and markers of renal damage, microalbuminuria and NAG values. The relationship between endothelins and hypertension was without statistical significance.  相似文献   
963.
A prospective series of 65 patients with surgically confirmed lung cystic hydatid disease was evaluated in terms of their radiologic characteristics, serologic response, and presence of cysts in other organs. Cysts were mostly single and located in lower lung lobes. Liver compromise was found in 34% of the patients. Despite a systematic search, no patient showed brain cysts in this series. Twelve patients had previous hydatid disease: six in the liver and eight in the lung (two had involvement of both organs in the past). Serology using bovine cyst fluid in an immunoblot assay was 85% sensitive. Serologic response was not associated with number or cyst or compromise of other organs but was clearly associated to the presence of at least one complicated cyst. Cyst status in terms of complications should be described to allow appropriate assessment of serologic evaluations.  相似文献   
964.
A 1-day meeting, attended by invited respiratory and primary-care specialists all of whom had an international profile and a specific interest in Chronic Obstructive Pulmonary Disease (COPD), considered specific research recommendations from the Global Initiative in Obstructive Lung Disease (GOLD) workshop report. Attendees discussed developing a tool to complement spirometry and help primary-care physicians assess treatment success in patients with chronic obstructive pulmonary disease. Discussion focused on the requirement of such a tool, and the limitations of existing tools. Proposals followed for a simple, cost-effective checklist for primary-care. This paper is a consensus report of the discussions from the meeting. Decisions reached on the proposed questionnaire were unanimous.  相似文献   
965.
The aim of this study was to examine the possible relationship between the plasma levels of leptin and tumor necrosis factor (TNF)- and the stage of hepatic fibrosis in a cohort of patients with chronic hepatitis C. Leptin and TNF levels were measured by RIA in 135 patients and in 75 age- and sex-matched controls. Liver disease was evaluated by the stage of fibrosis and the extent of inflammatory infiltrate in the liver biopsy. Leptin levels correlated with BMI values in healthy controls and in patients with chronic hepatitis C (men, r = 0.61, P = 0.0001; women, r = 0.68, P = 0.003). Leptin levels increased as hepatic fibrosis stage progressed both in male and in female patients (P < 0.001); also, TNF levels were higher in patients with an advanced stage of fibrosis (P = 0.006). In these patients, levels of leptin increased according to the progression of the stage of fibrosis; these data suggest that leptin may play a role in the regulation of hepatic fibrosis.  相似文献   
966.
967.

Purpose

“Endometriosis” is defined such as the presence of endometrial glands and stroma outside the uterine cavity. This ectopic condition may develop as deeply infiltrating endometriosis (DIE) when a solid mass is located deeper than 5 mm underneath the peritoneum including the intestinal wall. The ideal surgical treatment is still under search, and treatment may range from simple shaving to rectal resection. The aim of the present systematic review is to report and analyze the postoperative outcomes after rectosigmoid resection for endometriosis.

Methods

We performed a systematic review according to Meta-analysis of Observational Studies in Epidemiology guidelines. The search was carried out in the PubMed database, using the keywords: “rectal resection” AND “endometriosis” and “rectosigmoid resection” AND “endometriosis.” The search revealed 380 papers of which 78 were fully analyzed.

Results

Thirty-eight articles published between 1998 and 2017 were included. Three thousand seventy-nine patients (mean age 34.28?±?2.46) were included. Laparoscopic approach was the most employed (90.3%) followed by the open one (7.9%) and the robotic one (1.7%). Overall operative time was 238.47?±?66.82. Conversion rate was 2.7%. In more than 80% of cases, associated procedures were performed. Intraoperative complications were observed in 1% of cases. The overall postoperative complications rate was 18.5% (571 patients), and the most frequent complication was recto-vaginal fistula (74 patients, 2.4%). Postoperative mortality rate was 0.03% and mean hospital stay was 8.88?±?3.71 days.

Conclusions

Despite the large and extremely various number of associated procedures, rectosigmoid resection is a feasible and safe technique to treat endometriosis.
  相似文献   
968.
BACKGROUND/AIMS: Cirrhotic patients with spontaneous bacterial peritonitis show a marked activation of the cytokine cascade, and cytokines induce the synthesis of nitric oxide in vitro. Our aim was to assess whether patients with ascitic fluid infection show increased levels of nitric oxide, and whether this is related to the development of renal impairment. METHODS: Retrospective analysis of prospectively collected specimens from 168 patients with cirrhosis and presence of sterile or infected ascitic fluid. Routine biochemical data together with nitric oxide metabolites, tumour necrosis factor and interleukin-6 were measured. Univariate and multivariate analyses were performed to identify factors related to the development of renal impairment. RESULTS: Patients with infected ascites showed increased serum and ascitic-fluid levels of nitric oxide metabolites and cytokines compared with patients with sterile ascites. A significant direct correlation was observed between serum and ascitic fluid nitric oxide metabolite levels. Multivariate analysis identified ascitic-fluid nitric oxide metabolites as an independent predictor of renal impairment. CONCLUSIONS: The increased serum and ascitic fluid nitric oxide found in patients with infected ascites might induce a deterioration of the increased peripheral vasodilation found in this setting, leading to the development of renal impairment in a series of patients with spontaneous bacterial peritonitis.  相似文献   
969.
AIM: To analyze the risk of cardiovascular complications in patients with indication for surgical treatment of Chagasic esophageal achalasia and to correlate the surgical risks with the degree of esophageal dilation, thereby proposing a risk scale index. METHODS: One hundred and twenty-four patients with Chagasic esophageal achalasia, who received surgical treatment at the Hospital das Clinicas of the Federal University of Goias, were included in this study. The patients were mostly related to the postoperative complications due to the cardiovascular system. All the patients were submitted to: (1) clinical history to define the cardiac functional class (New York Heart Association); (2) conventional 12-lead electrocardiogram at rest; and (3) contrast imaging of the esophagus to determine esophageal dilatation according to Rezende's classification of Chagasic megaesophagus. RESULTS: An assessment of the functional classification (FC) of heart failure during the preoperative period determined that 67 patients (54.03%) were assigned functional class I (FC I), 46 patients (37.09%) were assigned functional class II (FC II), and 11 patients (8.87%) were assigned functional class III (FC III). None of the patients were assigned to functional class IV (FC IV). There was a positive correlation between the functional class and the postoperative complications (FC IXFC II: P<0.001; FC IXFC III: P<0.001). The ECG was normal in 44 patients (35.48%) and presented abnormalities in 80 patients (64.52%). There was a significant statistical correlation between abnormal ECG (arrhythmias and primary change in ventricular repolarization) and postoperative complications (P<0.001). With regard to the classification of the Chagasic esophageal achalasia, the following distribution was observed: group II, 53 patients (42.74%); group III, 37 patients (29.83%); and group IV, 34 patients (27.41%). There was a positive correlation between the degree of esophageal dilation and the increase in postoperative complications (grade IIXgrade III achalasia: P<0.001; grade IIXgrade IV achalasia: P<0.001; and grade IIIXgrade IV achalasia: P = 0.017). Analyzing these results and using a multivariate regression analysis associated with the probability decision analysis, a risk scale was proposed as follows: up to 21 points (mild risk); from 22 to 34 points (moderate risk); and more than 34 points (high risk). The scale had 82.4% accuracy for mild risk patients and up to 94.6% for the high risk cases. CONCLUSION: The preoperative evaluation of the cardiovascular system, through a careful anamnesis, an ECG and contrast imaging of the esophagus, makes possible to estimate the surgical risks for Chagas' disease patients who have to undergo surgical treatment for esophageal achalasia.  相似文献   
970.
Pilonidal cyst   总被引:8,自引:4,他引:8  
PURPOSE: The treatment of sacrococcygeal pilonidal cyst, despite being considered a well-defined clinical entity and opinion as to its acquired origin being almost unanimous, has some controversial aspects. Surgery is the principal method of treatment, and several techniques have been proposed. All of them try to reduce morbidity, to offer conditions of fast cicatrization, to have a low recurrence rate, and to offer cure. This study was undertaken to review the available data in the literature about the cause of the disease and to determine the current optimal method of treatment, evaluating morbidity, healing, recurrence, and cure. METHODS: Data available on the topic of pilonidal cyst in the English-language literature were obtained from Index Medicus and MEDLINE and were reviewed and analyzed. RESULTS: There is nearly a consensus that pilonidal cyst is acquired, hair being the agent that causes the disease. Presently, the most-used surgical procedure is excision of the cyst, with open or closed wound for healing. However, many authors prefer to use the method of incision and curettage. New surgical techniques are being proposed. CONCLUSION: The majority of authors conclude that sacrococcygeal pilonidal cyst is an acquired disease, although a minority believe it is congenital. Although excision is the method of choice for most surgeons, in our experience the incision and curettage procedure is the best surgical treatment with regard to morbidity, healing, recurrence, and cure of the disease.  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