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   27380篇
  免费   1829篇
  国内免费   154篇
耳鼻咽喉   248篇
儿科学   951篇
妇产科学   722篇
基础医学   3584篇
口腔科学   481篇
临床医学   2661篇
内科学   6035篇
皮肤病学   617篇
神经病学   2930篇
特种医学   571篇
外科学   2595篇
综合类   170篇
一般理论   38篇
预防医学   3414篇
眼科学   399篇
药学   1737篇
  1篇
中国医学   65篇
肿瘤学   2144篇
  2024年   36篇
  2023年   405篇
  2022年   691篇
  2021年   1293篇
  2020年   778篇
  2019年   1071篇
  2018年   1205篇
  2017年   875篇
  2016年   944篇
  2015年   1008篇
  2014年   1279篇
  2013年   1590篇
  2012年   2397篇
  2011年   2418篇
  2010年   1242篇
  2009年   1030篇
  2008年   1634篇
  2007年   1553篇
  2006年   1434篇
  2005年   1331篇
  2004年   1112篇
  2003年   948篇
  2002年   854篇
  2001年   249篇
  2000年   277篇
  1999年   235篇
  1998年   119篇
  1997年   105篇
  1996年   88篇
  1995年   87篇
  1994年   55篇
  1993年   60篇
  1992年   98篇
  1991年   88篇
  1990年   64篇
  1989年   75篇
  1988年   76篇
  1987年   51篇
  1986年   52篇
  1985年   34篇
  1984年   52篇
  1983年   27篇
  1982年   31篇
  1981年   35篇
  1980年   23篇
  1978年   21篇
  1977年   24篇
  1974年   27篇
  1973年   23篇
  1968年   19篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
We studied four patients with ruptured aneurysms of the sinus of Valsalva. All were men with a mean age of 33 years. The presenting illness was insidious in three and of abrupt onset in one. Physical examination showed a continuous murmur in all. Chest X ray film showed moderate cardiomegaly. Electrocardiogram disclosed left ventricular hypertrophy. Echocardiogram revealed the site of the rupture which was corroborated by aortography. Two aneurysms ruptured to the right ventricle and two to the right atrium. All were corrected by surgery. All patients became asymptomatic.  相似文献   
52.
BACKGROUND: Anaphylaxis must be recognized and treated promptly to avoid significant morbidity and mortality. In this clinical setting, electrocardiographic changes can be multifactorial. OBJECTIVE: To discuss vasospasm as a cause of myocardial ischemia and its possible triggering by anaphylaxis itself or by the administration of epinephrine. METHODS: We describe a patient with multiple previous allergies who received intravenous epinephrine to treat suspected anaphylaxis. She immediately developed crushing chest pain with ST-segment elevations in the inferior leads. Throughout the discussion, we address differential diagnoses, physiologic features, and treatment. RESULTS: Her symptoms and electrocardiographic changes were consistent with vasospasm, which resolved after treatment with sublingual nitroglycerin. However, the reaction was sufficient to cause an elevation in the troponin T level and, therefore, myocardial damage on the cellular level. CONCLUSIONS: Cardiovascular complications, including electrocardiographic changes, may be induced by anaphylactic mediators or by medications used for its treatment.  相似文献   
53.
Stapled hemorrhoidopexy is widely accepted to treat hemorrhoids, but serious complications have been reported. In this prospective audit, we correlated clinical outcome with pathological findings. From January 2003 to April 2007, 94 patients underwent hemorrhoidopexy. Macroscopic appearance of the specimen (shape, size, and depth) was recorded. Microscopically, the presence of columnar, transitional, and squamous epithelium, the involvement of circular/longitudinal smooth muscle, and features of mucosal prolapse were assessed. Clinical outcome was evaluated by a validated questionnaire. Postoperative pain, secretion, and bleeding durations were 12.7 +/− 10.6, 5.6 +/− 9.6, and 6.3 +/− 8.4 days. Patient’s return to work averaged 16.7 +/− 10.7 days. Fissure, skin tags, and anal strictures were observed in 23.4%. Seven patients experienced pain for a significantly longer period of time. All specimens contained columnar mucosa, but 29.8% contained columnar and transitional epithelium and 12.8% contained columnar, anal transitional, and stratified squamous epithelium. Smooth muscle was observed in 62.7%. Pain was significantly increased if transitional epithelium was present in the specimen. No correlation or differences were observed if smooth muscle was present, although postoperative bleeding was more frequent. Hemorrhoidopexy is safe and effective. The specimen should always be sent for pathology examination. Only columnar epithelium should be present and, although the presence of smooth muscle does not influence the outcome in terms of functional results, its presence may play a role in postoperative bleeding. Presented as poster at the Digestive Disease Week, May 2007, Washington, USA  相似文献   
54.
55.
56.
57.
The Spanish registry of alpha-1 antitrypsin deficiency was founded in 1993 and became a member of the International Registry (AIR) in 1999. We describe the updating process following its incorporation into AIR and compare the data collected in the first period (1993–1999) and the second period (1999–2005), during which time patients were included exclusively by internet.The registry included 301 patients during period 1, 69% males and 46% had a history of smoking. Their mean age was 46 years (SD = 13) and 284 (94%) had the ZZ phenotype, 49% received augmentation therapy. During period 2, 161 new cases were included, 63% of whom were males with a mean age of 44 years (SD = 16). A total of 126 (78%) had the ZZ phenotype. Only 12% received augmentation therapy. A total of 462 different patients were included in both periods. Significant differences were observed in the number of cases with the SZ phenotype and the severity of FEV1 impairment between the two periods.Implementation of an internet-based collection of data did not result in a lower rate of reporting to the registry. However, data from a significant number of patient included in period 1 could not be actualized in the new data base.  相似文献   
58.
59.
Angiogenesis precedes recovery following spinal cord injury and its extent correlates with neural regeneration, suggesting that angiogenesis may play a role in repair. An important precondition for studying the role of angiogenesis is the ability to induce it in a controlled manner. Previously, we showed that a coculture of endothelial cells (ECs) and neural progenitor cells (NPCs) promoted the formation of stable tubes in vitro and stable, functional vascular networks in vivo in a subcutaneous model. We sought to test whether a similar coculture would lead to the formation of stable functional vessels in the spinal cord following injury. We created microvascular networks in a biodegradable two-component implant system and tested the ability of the coculture or controls (lesion control, implant alone, implant + ECs or implant + NPCs) to promote angiogenesis in a rat hemisection model of spinal cord injury. The coculture implant led to a fourfold increase in functional vessels compared with the lesion control, implant alone or implant + NPCs groups and a twofold increase in functional vessels over the implant + ECs group. Furthermore, half of the vessels in the coculture implant exhibited positive staining for the endothelial barrier antigen, a marker for the formation of the blood–spinal cord barrier. No other groups have shown positive staining for the blood–spinal cord barrier in the injury epicenter. This work provides a novel method to induce angiogenesis following spinal cord injury and a foundation for studying its role in repair.  相似文献   
60.
BACKGROUND: Executive dysfunction has been reported at different ages in autism. It is not clear however, when this impairment emerges or how its expression is affected by development. METHODS: 61 non-mentally retarded autism participants (AUT) and 61 age, gender, and IQ matched typically developing participants (CON) were assessed with two oculomotor executive function tasks, the oculomotor delayed response task (ODR) and the antisaccade task (AS), as well as a visually-guided saccade sensorimotor task (VGS). RESULTS: The AUT group demonstrated impairments in response inhibition and spatial working memory at all ages tested. Developmental improvements in speed of sensorimotor processing and voluntary response inhibition were similar in both groups indicating sparing of some attentional control of behavior. Developmental progression in the speed of initiating a cognitive plan and maintaining information on line over time, however, was impaired in the AUT group indicating abnormal development of working memory. CONCLUSIONS: These results indicate that while executive dysfunction is present throughout development, there is evidence for both typical and atypical developmental progression of executive functions in autism. The plasticity suggested by the developmental improvements may have implications regarding appropriate developmental epochs and types of interventions aimed at enhancing cognitive capacities in individuals with autism.  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