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   50133篇
  免费   4020篇
  国内免费   135篇
耳鼻咽喉   433篇
儿科学   1817篇
妇产科学   1204篇
基础医学   6717篇
口腔科学   682篇
临床医学   6424篇
内科学   9100篇
皮肤病学   1055篇
神经病学   5170篇
特种医学   1363篇
外科学   5786篇
综合类   866篇
一般理论   75篇
预防医学   5606篇
眼科学   878篇
药学   3202篇
中国医学   28篇
肿瘤学   3882篇
  2023年   317篇
  2022年   477篇
  2021年   1024篇
  2020年   759篇
  2019年   1047篇
  2018年   1230篇
  2017年   951篇
  2016年   975篇
  2015年   1032篇
  2014年   1499篇
  2013年   2208篇
  2012年   3155篇
  2011年   3298篇
  2010年   1757篇
  2009年   1595篇
  2008年   2758篇
  2007年   2886篇
  2006年   2688篇
  2005年   2592篇
  2004年   2398篇
  2003年   2158篇
  2002年   2163篇
  2001年   992篇
  2000年   1009篇
  1999年   898篇
  1998年   521篇
  1997年   433篇
  1996年   384篇
  1995年   344篇
  1994年   331篇
  1993年   313篇
  1992年   699篇
  1991年   693篇
  1990年   685篇
  1989年   662篇
  1988年   519篇
  1987年   579篇
  1986年   568篇
  1985年   540篇
  1984年   413篇
  1983年   442篇
  1982年   263篇
  1979年   394篇
  1978年   268篇
  1977年   224篇
  1976年   253篇
  1975年   221篇
  1974年   244篇
  1973年   228篇
  1972年   206篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
31.
BACKGROUND: Studies suggest that patients who undergo off-pump coronary artery bypass grafting (OPCABG) have fewer short-term complications and use fewer inpatient resources than do patients who undergo standard coronary artery bypass grafting (CABG) with extracorporeal circulation. However, dissimilarity between groups in risk factors for complications has hindered interpretation of results. OBJECTIVES: To compare the prevalence of selected complications (atrial fibrillation, stroke, reoperation, and bleeding) and inpatient resource utilization (length of stay, discharge disposition, total charges) between subjects undergoing primary isolated CABG or OPCABG who were matched with respect to key risk factors. METHODS: Retrospective, causal-comparative survey conducted in 1 center for 18 months. Patients who underwent primary isolated CABG or OPCABG were matched for sex, age (within 2 years), left ventricular ejection fraction (within 0.05), and graft-patient ratio (exact match) and compared for prevalence of new-onset atrial fibrillation, stroke, reoperation within 24 hours, and bleeding. Statistical analysis included Wilcoxon and t tests for paired comparisons. RESULTS: The sample (107 matched pairs) was 63% male, with a mean age of 66 (SD 9.5) years, a mean left ventricular ejection fraction of 0.51 (SD 0.13), and a mean graft-patient ratio of 3.41 (SD 0.74). The 2 groups did not differ significantly in New York Heart Association class (P = .43), Acute Physiology and Chronic Health Evaluation III score (P = .22), postoperative beta-blocker use (P = .73), or comorbid conditions. None of the complications examined differed significantly between pairs. CONCLUSION: Patients with comparable risk profiles have similar prevalences of selected complications after CABG and OPCABG.  相似文献   
32.
33.
Renal cell carcinomas may extend into the vena cava and the tumor thrombus occasionally involves the right atrium. The operative approach depends upon precise preoperative and intraoperative staging and thrombus localization. We report a case of renal cell carcinoma with complete inferior vena caval and hepatic vein occlusion with tumor extension into the right atrium. Preoperatively, transesophageal echocardiography provided superior images of the tumor and its extension, and intraoperatively allowed continuous monitoring of cardiac function and the removal of tumor from the atrium and inferior vena cava. Its use obviated the need for more costly and invasive preoperative and intraoperative procedures.  相似文献   
34.
Lymphoscintigraphy in lymphedema: an aid to microsurgery   总被引:3,自引:0,他引:3  
The role of lymphoscintigraphy, performed with 99mTc-labeled antimony sulfur colloid, in the diagnosis of lymphedema and as a test for selection of patients for microvascular operation was evaluated in 32 patients with primary and secondary lymphedema and four patients with other causes of leg edema. Lymphoscintigraphy clearly demonstrated if edema was of lymphatic origin. Five different image patterns were identified; abnormal image patterns could not be predicted from clinical history or physical findings. Quantitative evaluation of removal of the radioactive colloid from the injection site and appearance in lymph node sites and liver was of limited usefulness. Nine patients underwent various surgical procedures before or after lymphoscintigraphy. Lympho-venous anastomoses were possible only in patients who had patent lymph channels visible on lymphoscintigrams. Based on initial experience, lymphoscintigraphy seems to be useful to select patients for microvascular operation.  相似文献   
35.
36.
37.
A 20-year-old woman with a 13-year history of insulin-dependent diabetes mellitus presented with a history of malaise, fever, a non-healing ulcer of the great toe, and an insect bite incurred during recent travel to a foreign country. Milky white infiltrates accompanied by inflammatory cells located within close proximity to neovascular fronds in both vitreous cavities led to the suspicion of bilateral metastatic endophthalmitis. Studies conducted during hospitalization failed to show evidence of systemic blood born infection. A diagnostic vitrectomy in one eye failed to grow organisms, though lipid laden macrophages were identified by electron microscopy. The clinical appearance improved in both eyes during her hospitalization coincident with improved diabetic control. It was later concluded that the milky white infiltrates were associated with hyperlipidemia as a consequence of poorly controlled diabetes and a familial tendency toward hyperlipidemia.  相似文献   
38.
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   
39.
Late-life migraine accompaniments--further experience   总被引:3,自引:0,他引:3  
In 1980, 120 cases with late-life migrainous accompaniments resembling transient ischemic attacks were presented. In the present paper, 85 further cases examined in the past five years are analyzed. The findings support the concept advanced previously. In general, the cases are divided into the same categories: visual--21 cases, visual and paresthesias--6, visual and speech disturbance--2, visual, paresthesias and speech disturbance--3, visual, paresthesias, speech disturbance, and weakness--20, visual and brainstem symptoms--3, and cases without visual symptoms--32. The ages ranged from 40 to 73 years. Headache occurred in association with the episodes in only 40% of cases. There was a history of recurrent headache in 65%. The condition can justifiably be regarded as benign. Migrainous accompaniments account for some of the cases of transient ischemia with normal angiograms. Knowledge of the condition helps in the planning of rational management.  相似文献   
40.
Background and Objective: To investigate Photofrin® (PII) and CASPc for photodynamic therapy (PDT) of the ciliary body in rabbits. Study Design/Materials and Methods: PII (10 mg/kg) or CASPc (1 mg/kg) was given by ear vein. Pharmacokinetics were studied in frozen sections by fluorescence microscopy (CCD camera based low light detection system with digital image processing) at 1 and 24 h (8 rabbits;16 eyes). Laser light was delivered (argon pumped dye laser;630 and 675 nm;8 rabbits;16 eyes) by contact fiberoptic. To compensate for iris attenuation, irradiance was 125 mW/cm2 (20, 40, 80, or 160 J/cm2). Controls (4 rabbits;8 eyes) received laser light without photochemicals (OD) and for comparison, continuous wave Nd:YAG laser by fiberoptic (0.8–1.2J;OS). Results: Localization studies showed intravascular distribution with some selective ciliary body distribution at 24 h (PII > CASPc). Rabbits treated with PII or CASPc exhibited variable amounts of gross ciliary body edema, infarction, and necrosis by 24–48 h. This response was not seen in PDT control tissues;damage was seen in the iris and ciliary body, with partial vacuolization of the pigment epithelium. Conclusion: PDT may offer a more selective approach to ciliary body destruction. A small but significant thermal effect was seen during PDT from melanin photon uptake with damage to iris and ciliary body. Thermal damage and potential interaction with ocular visual pigments may limit use of these photochemicals and wavelengths for PDT of the ciliary body © 1995 Wiley-Liss, Inc.  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