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   6948篇
  免费   340篇
  国内免费   62篇
耳鼻咽喉   55篇
儿科学   111篇
妇产科学   136篇
基础医学   786篇
口腔科学   109篇
临床医学   539篇
内科学   1884篇
皮肤病学   111篇
神经病学   707篇
特种医学   362篇
外科学   1031篇
综合类   15篇
预防医学   297篇
眼科学   53篇
药学   377篇
中国医学   12篇
肿瘤学   765篇
  2024年   8篇
  2023年   52篇
  2022年   116篇
  2021年   199篇
  2020年   140篇
  2019年   138篇
  2018年   187篇
  2017年   136篇
  2016年   183篇
  2015年   195篇
  2014年   266篇
  2013年   323篇
  2012年   571篇
  2011年   564篇
  2010年   303篇
  2009年   309篇
  2008年   487篇
  2007年   470篇
  2006年   449篇
  2005年   458篇
  2004年   387篇
  2003年   368篇
  2002年   349篇
  2001年   40篇
  2000年   32篇
  1999年   41篇
  1998年   68篇
  1997年   54篇
  1996年   43篇
  1995年   48篇
  1994年   31篇
  1993年   39篇
  1992年   37篇
  1991年   20篇
  1990年   30篇
  1989年   35篇
  1988年   23篇
  1987年   20篇
  1986年   15篇
  1985年   13篇
  1984年   8篇
  1983年   11篇
  1982年   9篇
  1981年   7篇
  1980年   20篇
  1978年   4篇
  1977年   4篇
  1976年   3篇
  1971年   5篇
  1902年   3篇
排序方式: 共有7350条查询结果,搜索用时 0 毫秒
101.
Following the spread of the SARS-CoV-2 B.1.1.7 variant, social distancing was strengthened in France in January 2021. Using a two-strain mathematical model calibrated on genomic surveillance, we estimated that curfew measures allowed hospitalisations to plateau by decreasing transmission of the historical strains while B.1.1.7 continued to grow. School holidays appear to have further slowed down progression in February. Without progressively strengthened social distancing, a rapid surge of hospitalisations is expected, despite the foreseen increase in vaccination rhythm.  相似文献   
102.
103.
Purpose  This study was designed to assess the long-term results of stapled hemorrhoidopexy in 291 patients with Grade III and Grade IV hemorrhoids after a minimum follow-up of five years. Methods  Records of patients submitted to stapled hemorrhoidopexy for Grade III and Grade IV hemorrhoids between January 1999 and December 2002 were retrospectively analyzed. Long-term outcome was evaluated with a standardized questionnaire and an office visit, including anorectal examination and rigid proctoscopy. Results  A total of 291 patients with Grade III (57.4 percent) and Grade IV (42.6 percent) hemorrhoids were evaluated. Intraoperative (20.3 percent) and postoperative (4.8 percent) bleeding was the most frequent complication. The questionnaire was submitted to all patients at a median follow-up of 73 (range 60–93) months. There were no symptoms related to hemorrhoids in 65.3 percent of patients, moderate symptoms in 25.4 percent of patients, and severe symptoms in 9.3 percent of patients. Fifty-three (18.2 percent) patients had recurrence. Reoperation was necessary in 21 (7.2 percent) patients (4 in Grade III hemorrhoids and 17 in Grade IV hemorrhoids; P < 0.001), with no recurrent symptoms and/or prolapse. Patient satisfaction for operation was 89.7 percent. Conclusions  Stapled hemorrhoidopexy is a safe and effective treatment for Grade III and Grade IV hemorrhoids. Recurrence requiring reoperation was higher in Grade IV hemorrhoids than in Grade III hemorrhoids. Reprints are not available.  相似文献   
104.
A recently discovered variant in the prothrombin gene (20210A) has been found in approximately 5–10% of patients with venous thromboembolism. It has been shown that patients with this variant present with high levels of prothrombin in plasma and this is maintained to be the most likely mechanism by which the risk of thrombosis is increased. We have evaluated prothrombin antigen levels in 50 carriers of the 20210A allele and compared with non-carriers. 327 subjects were subdivided according to deficiency status and previous thrombosis. 30 symptomatic and 20 asymptomatic carriers had increased mean prothrombin levels as compared to symptomatic ( n  = 178) or asymptomatic ( n  = 99) non-carriers. The percentage of subjects with prothrombin levels above cut-off values of 1.15 u/ml or 1.30 u/ml was significantly higher in carriers of the prothrombin variant as compared to non-carriers, regardless of a previous thrombosis. However, among non-carriers the percentage of those with prothrombin levels above cut-off values was significantly higher in the group of symptomatic as compared to asymptomatic individuals. In conclusion, increased prothrombin antigen levels, as detected by a specific ELISA, were found among 50 symptomatic and asymptomatic carriers of the 20210A prothrombin variant as well as among a large group of symptomatic non-carriers. The data are in agreement with those found by using functional tests for the determination of prothrombin levels in these patients.  相似文献   
105.
International Journal of Legal Medicine - Synthetic cathinones are a class of psychoactive drugs that have become, in recent years, of quite common observation in medical and toxicological forensic...  相似文献   
106.
BACKGROUND: The aim of the study is to analyze pancreatic metastases and their clinical, radiological, therapeutic and prognostic features. METHODS: Three cases of pancreatic metastases observed and a world literature review of 333 cases were recorded. RESULTS: Pancreatic metastases are due more frequently to renal cell carcinoma; they are usually metachronous and characterized by a long period of time between the resection of the primary tumor and their detection. The differential diagnosis with other pancreatic masses is difficult, but an accurate anamnesis, some peculiar findings of imaging techniques and percutaneous fine needle aspiration could allow preoperative diagnosis. Pancreatic resections are the treatment of choice allowing the better palliation and improving survival. 150/234 pancreatic metastases underwent pancreatic resections (resectability index = 64.1%); 88/132 patients are alive with a mean follow-up of 27.1 months; of the 44 dead patients the mean survival time was 21.3 months. Among pancreatic metastases the primary tumor with better prognosis is renal cell carcinoma. CONCLUSION: Pancreatic metastases are rare; their preoperative diagnosis is difficult but useful and possible. Surgical resection is suggested because the patient still may have a prolonged survival.  相似文献   
107.
108.
Type 3 iodothyronine deiodinase (D3) is the major physiologic inactivator of thyroid hormone. This selenoenzyme, previously identified in human placenta and brain, catalyzes the inner-ring deiodination of T(4) to reverse T(3) and T(3) to 3, 3'-diiodothyronine, both of which are biologically inactive. We analyzed D3 expression in several human adult and fetal tissues by immunohistochemistry and correlated the results with D3 activity assays where possible. High D3 expression was present in the placental syncytiotrophoblasts and cytotrophoblasts, endothelium of fetal vessels, and maternal decidua. D3 was also present at other sites of maternal-fetal interface, including the umbilical arteries and vein and the fetal respiratory, digestive, and urinary tract epithelium. Surprisingly, D3 was also present in the endometrial glands of nonpregnant human uteri, and endometrial activity approximated that of term placenta. The presence of D3 at maternal-fetal interfaces is consistent with its role in modulating the thyroid status of the human fetus and its expression in endometrium suggests that local regulation of thyroid status is important in implantation.  相似文献   
109.
In diabetic patients, the pathophysiologic mechanisms of exercise-induced left ventricular (LV) dysfunction remain controversial. In this study, the role of myocardial contractility recruitment in determining an abnormal LV response to isometric or dynamic exercise has been investigated in 14 diabetic patients with autonomic dysfunction. Ischemic heat disease was excluded by the absence of LV wall motion abnormalities induced by isotonic and isometric exercise and by coronary angiography. Left ventricular and myocardial function were studied at rest, and during isometric and isotonic exercise, by two-dimensional echocardiography; moreover, recruitment of an inotropic reserve was assessed by postextra-systolic potentiation at rest and at peak handgrip. An abnormal response of LV ejection fraction to isometric (9/14) or to dynamic (8/14) exercise was frequent in study patients. In these patients, baseline myocardial contractility was normal, and the significant increase in ejection fraction by postextrasystolic potentiation indicated a normal contractile reserve (65 ± 7% vs. 74 ± 6%, p=0.001). Nevertheless, the downward displacement of LV ejection fraction-systolic wall stress relationships during exercise suggests an inadequate increase in myocardial contractility. However, the abnormal ejection fraction at peak handgrip was completely reversed by postextrasystolic potentiation (67 ± 6% vs. 58.1 ± 10%, p=0.008), a potent inotropic stimulation independent of the integrity of adrenergic cardiac receptors. A defective inotropic recruitment, despite the presence of a normal LV contractile reserve, plays an important role in deexercise LV dysfunction in diabetic patients with autonomic neuropathy.  相似文献   
110.
BackgroundRisk stratification for ventricular arrhythmias (VA) and sudden death in nonischemic dilated cardiomyopathy (DCM) remains suboptimal.ObjectivesThe goal of this study was to provide an improved risk stratification algorithm for VA and sudden death in DCM.MethodsThis was a retrospective cohort study of consecutive patients with DCM who underwent cardiac magnetic resonance with late gadolinium enhancement (LGE) at 2 tertiary referral centers. The combined arrhythmic endpoint included appropriate implantable cardioverter-defibrillator therapies, sustained ventricular tachycardia, resuscitated cardiac arrest, and sudden death.ResultsIn 1,165 patients with a median follow-up of 36 months, LGE was an independent and strong predictor of the arrhythmic endpoint (hazard ratio: 9.7; p < 0.001). This association was consistent across all strata of left ventricular ejection fraction (LVEF). Epicardial LGE, transmural LGE, and combined septal and free-wall LGE were all associated with heightened risk. A simple algorithm combining LGE and 3 LVEF strata (i.e., ≤20%, 21% to 35%, >35%) was significantly superior to LVEF with the 35% cutoff (Harrell’s C statistic: 0.8 vs. 0.69; area under the curve: 0.82 vs. 0.7; p < 0.001) and reclassified the arrhythmic risk of 34% of patients with DCM. LGE-negative patients with LVEF 21% to 35% had low risk (annual event rate 0.7%), whereas those with high-risk LGE distributions and LVEF >35% had significantly higher risk (annual event rate 3%; p = 0.007).ConclusionsIn a large cohort of patients with DCM, LGE was found to be a significant, consistent, and strong predictor of VA or sudden death. Specific high-risk LGE distributions were identified. A new clinical algorithm integrating LGE and LVEF significantly improved the risk stratification for VA and sudden death, with relevant implications for implantable cardioverter-defibrillator allocation.  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