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   18692篇
  免费   1099篇
  国内免费   52篇
耳鼻咽喉   213篇
儿科学   490篇
妇产科学   344篇
基础医学   3241篇
口腔科学   463篇
临床医学   1552篇
内科学   3861篇
皮肤病学   692篇
神经病学   1971篇
特种医学   829篇
外国民族医学   2篇
外科学   1996篇
综合类   92篇
一般理论   9篇
预防医学   1024篇
眼科学   368篇
药学   1215篇
中国医学   31篇
肿瘤学   1450篇
  2023年   93篇
  2022年   235篇
  2021年   388篇
  2020年   246篇
  2019年   376篇
  2018年   446篇
  2017年   334篇
  2016年   502篇
  2015年   514篇
  2014年   630篇
  2013年   839篇
  2012年   1212篇
  2011年   1218篇
  2010年   686篇
  2009年   703篇
  2008年   1054篇
  2007年   1116篇
  2006年   1069篇
  2005年   998篇
  2004年   929篇
  2003年   845篇
  2002年   812篇
  2001年   424篇
  2000年   382篇
  1999年   414篇
  1998年   235篇
  1997年   179篇
  1996年   119篇
  1995年   126篇
  1994年   87篇
  1993年   81篇
  1992年   172篇
  1991年   172篇
  1990年   153篇
  1989年   148篇
  1988年   103篇
  1987年   124篇
  1986年   101篇
  1985年   109篇
  1984年   80篇
  1983年   94篇
  1982年   54篇
  1981年   49篇
  1979年   85篇
  1977年   46篇
  1975年   46篇
  1974年   52篇
  1973年   63篇
  1972年   48篇
  1971年   48篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
21.
OBJECTIVE: Biventricular pacing has demonstrated improvement in cardiac function in treating congestive heart failure (CHF). Two different operative strategies (coronary sinus vs. epicardial stimulation) for left ventricular (LV) pacing were compared. METHODS: Since April 1999, a total of 86 patients (pts, age: 63+/-10 years) with depressed systolic LV function (mean ejection fraction 24+/-9%), left bundle-branch-block (mean QRS 182+/-22 ms) and congestive heart failure NYHA III or higher were enrolled. For biventricular stimulation coronary sinus (CS) leads were placed in 79 pts. Nine of these devices were converted to surgical epicardial LV-leads, because of CS-lead failure. In 7 patients epicardial LV-leads were initially implanted surgically, accounting for a total of 16 pts with surgical placed epicardial steroid-eluting LV-leads. For these, a limited left-lateral thoracotomy (7+/-4 cm) was used. Thirty-three (38%) pts had an indication for a defibrillator. The mean follow-up time was 16.4+/-15.4 months (0.1-45 months), representing 107.1 patient-years. RESULTS: In the biventricular pacing mode, QRS duration decreased to 143+/-16 ms (P<0.001). Threshold capture of the CS-leads increased significantly compared to surgically placed epicardial leads (18 month control: 2.2+/-1.4V/0.5 ms vs. 0.7+/-0.3V/0.5 ms), which had no increase in threshold (P<0.001). At the 18 month follow-up 7 CS-leads had a threshold of >4V/0.5 ms vs. epicardial leads which were under 1.1V/0.5 ms, except for one (1.8V/0.5 ms). After CS-lead implantation 25 LV-lead related complications occurred, (failed implantation, CS-dissection, loss of pacing capture, diaphragm stimulation or lead dislodgment), vs. one dislodgement after surgical epicardial lead placement (P<0.05). Correct lead positioning (obtuse marginal branch area) was achieved in all surgical epicardial placements but only in 70% with CS-leads (P<0.03). In the follow up period, 9 pts died (4 cardiac related). Heart transplantation was necessary in 4 pts due to deterioration of the cardiomyopathy. CONCLUSIONS: Surgical epicardial lead placement revealed excellent long-term results and a lower LV-related complication rate compared to CS-leads. Although, the approach via limited thoracotomy for biventricular pacing is associated with 'more surgery', it is a safe and reliable technique and should be considered as an equal alternative.  相似文献   
22.
A group of 34 consecutive patients with coronary artery disease (n = 29) or dilated cardiomyopathy (n = 5) (3 women, 31 men, age 38-80 yr) who had severely impaired left ventricular function (left ventricular ejection fraction less than or equal to 40%) and high-grade ventricular ectopic activity (sustained or nonsustained ventricular tachycardia or ventricular fibrillation) were treated with amiodarone (mean dose: 206 mg/d) and followed for 1-117 (mean: 49) months. In the total group, there were seven sudden deaths, five deaths due to pump failure, one non-cardiac death, and two successful heart transplantations during follow-up. Thus the annual cardiac mortality in these carefully selected and followed patients was 8, 6%, the annual cardiac event rate was 10, 1%. The cumulative cardiac survival-rate was 62% after 5 years and 41% after 10 years. In five patients, treatment was interrupted after 10 to 43 months, three of the patients were alive at follow-up and two suffered cardiac death, resulting in an annual cardiac death rate of 12% in this subgroup of treatment. Based on the results of this retrospective analysis we conclude that in patients with low left ventricular ejection fraction and nonsustained or sustained ventricular tachycardia treated with low dose amiodarone, mortality was unexpectedly low. Thus, it may be the antiarrhythmic treatment to be considered in patients with ventricular tachycardia and severe left ventricular dysfunction.  相似文献   
23.
Gallstone shock wave therapy at the University Hospital of Zurich is a joint venture between the Medical Clinic, Medical Policlinic and Surgical Clinic. Patients with symptomatic cholecystolithiasis willing to submit themselves to a long period of treatment, were accepted for ESWL, should no contraindications be present. From October 1988 through May 1989 we treated 48 patients. In approximately two thirds of our patients we were successful with one ESWL alone, in one third 2 sessions and in two patients even 3 sessions were needed. In 42 patients course after therapy was as planned. Six had to be cholecystectomized later on. Best results were achieved in patients with single gallstones. In 2 of 5 cases there was disagreement between the number of gallstones found sonographically and the intraoperative findings. Histologic examination of gallbladders after ESWL showed no pathologic changes.  相似文献   
24.
Study Objectives . To evaluate the pharmacodynamic antibacterial activity of ticarcillin-clavulanic acid (T-C) and ampicillin-sulbactam (A-S) combinations against reference bacterial strains in patients with end-stage renal disease maintained on long-term hemodialysis. Design . Randomized, crossover, controlled study. Setting . National Institutes of Health-funded general clinical research unit in a Veterans Administration Medical Center. Patients . Nine adult men with end-stage renal disease maintained on long-term hemodialysis. Two subjects did not complete the study due to problems of vascular access, and another withdrew for personal reasons. Interventions . On a nondialysis day, each subject was randomly administered either T-C 3.1 g or A-S 3 g as a slow intravenous infusion over 30 minutes. Serial blood samples were collected for measurement of antibiotic serum concentrations and determination of serum bactericidal titers. Following a washout period, the study was repeated with the alternative antibiotic combination. Measurements and Main Results . The mean observed apparent β-half-life of clavulanic acid was substantially shorter than that for the other three drugs. The bactericidal activity of both A-S and T-C against non-β-lactamase-producing (Nβ-LP) strains of S. aureus and E. coli was consistently high, as indicated by geometric mean SBTs of at least 1:5 at 24 hours. Against β-lactamase-producing (β-LP) S. aureus, the geometric mean SBTs for A-S were at least 1:25 throughout the study period, while the geometric mean SBTs for T-C decreased over 24 hours from 1:29 to 1:6. Against β-LP E. coli, the bactericidal activities for both A-S and T-C were poor, with geometric mean peak SBTs of only 1:6 and 1:3, respectively. The geometric mean SBT for T-C against this E. coli strain had declined to 1:1 at 6 hrs. Conclusion . Increasing the dosing interval for T-C in patients with end-stage renal disease may lead to periods of insufficient clavulanic acid to protect ticarcillin from β-lactamase degradation.  相似文献   
25.
Between 1979 and 1988 43 percutaneous transluminal angioplasties (PTA) of the deep femoral artery were performed for treatment of severe claudication (n = 15) or for limb salvage (n = 28). Ateriographically, all patients had a long occlusion of the superficial femoral artery. Additional PTA of significant obstructions in the iliac and common femoral artery were performed in 6 patients of each group. Technical success was achieved in 41 of the 43 procedures (95%). Early clinical success was 60% for claudicants and 68% for patients with limb threatening ischemia. Success rates tended to be higher if additional PTA of the inflow tract was performed (75% versus 61%, n.s.). Patient with a good distal outflow benefited more frequently from PTA if they were treated for limb salvage (p less than 0.05). Within a follow-up period up to 24 months (mean 18.0 months) 5 patients died and one late failure occurred. Life table analysis lasting success in patients dilated for limb salvage, whereas success rate decreased to 48% in claudicants. PTA of the deep femoral artery is a less invasive and efficient treatment particularly for patients with limb threatening ischemia, an appropriate obstruction morphology provided.  相似文献   
26.
Objectives: In this study, the authors tested whether electromagnetic interference (EMI) is able to impair correct electrocardiogram analysis and produce false‐positive shock advice from automated external defibrillators (AEDs) when the true rhythm is sinus. Methods: Nineteen healthy subjects were used to test five AEDs available on the Austrian market in a prospective, open, and sequence‐randomized study. The primary outcome variable was the absolute number of shocks advised in the presence of EMI. The secondary outcome was the number of impaired analyses caused by incorrectly detected patient movements or electrode failure. Results: Of 760 tests run, 18 (2.37%) cases of false‐positive results occurred, and two of five AEDs recommended shocks in the presence of sinus rhythm. Of 760 tests run, no electrode failures occurred. There were 27 occurrences (3.55%) of motion detected by an AED in the presence of strong electromagnetic fields. Conclusions: AED models differ in their response to EMI; it may be useful to consider specific safety requirements for areas with such fields present. Working personnel and emergency medical services staff should be informed about potential risks and the possible need for patient evacuation before AEDs are attached and shock recommendations are followed.  相似文献   
27.
INTRODUCTION: A torn labial frenum is widely regarded as pathognomonic of abuse. METHODS: We systematically reviewed the evidence for this, and to define other intra-oral injuries found in physical abuse. Nine studies documented abusive torn labial frena in 27 children and 24 [corrected] were fatally abused: 22 were less than 5 years old. Only a direct blow to the face was substantiated as a mechanism of injury. RESULTS: Two studies noted accidentally torn labial frena, both from intubation. Abusive intra-oral injuries were widely distributed to the lips, gums, tongue and palate and included fractures, intrusion and extraction of the dentition, bites and contusions. CONCLUSIONS: Current literature does not support the diagnosis of abuse based on a torn labial frenum in isolation. The intra-oral hard and soft tissue should be examined in all suspected abuse cases, and a dental opinion sought where abnormalities are found.  相似文献   
28.
In the various types of lymphatic disease the use of roentgen therapy is recognized as the best type of treatment. In some cases the beneficial effects are only temporary and it is necessary to repeat the treatment from time to time. Many of these diseases are really neoplastic and in the long run their prognosis is uniformly bad.Local metastatic lesions caused by malignant neoplasms may be treated by roentgen therapy as a palliative measure, but it must be recognized that the ultimate prognosis in such cases also is bad.  相似文献   
29.
30.
Tension pneumomediastinum after severe vomiting in a 21-year-old female.   总被引:1,自引:0,他引:1  
A 21-year-old female with chronic membranoproliferative nephritis was admitted for suspected esophageal disruption and asthma after severe, prolonged vomiting. At the time of admission she presented with dyspnea, tachypnea, arterial hypotension and tachycardia. Physical examination showed discrete signs of ectopic air at the neck and distended cervical veins. CT-scan of the chest showed severe mediastinal emphysema with compression of the right atrium. After cervical mediastinotomy the cardiorespiratory parameters normalized immediately. Esophagoscopy showed multiple longitudinal mucosal tears between 25 and 45 cm; fluoroscopically, there was no leakage of contrast medium. Following conservative treatment the patient recovered completely and was discharged on day 8.  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