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   1338491篇
  免费   112526篇
  国内免费   6371篇
耳鼻咽喉   16707篇
儿科学   43008篇
妇产科学   36554篇
基础医学   183621篇
口腔科学   36295篇
临床医学   120690篇
内科学   278506篇
皮肤病学   31886篇
神经病学   110501篇
特种医学   55536篇
外国民族医学   274篇
外科学   210337篇
综合类   31533篇
现状与发展   2篇
一般理论   414篇
预防医学   106630篇
眼科学   28087篇
药学   93732篇
  5篇
中国医学   2227篇
肿瘤学   70843篇
  2018年   13375篇
  2017年   10632篇
  2016年   12796篇
  2015年   14297篇
  2014年   19946篇
  2013年   29733篇
  2012年   36234篇
  2011年   38885篇
  2010年   24371篇
  2009年   23902篇
  2008年   36365篇
  2007年   38775篇
  2006年   39898篇
  2005年   38491篇
  2004年   36723篇
  2003年   35822篇
  2002年   33832篇
  2001年   66054篇
  2000年   67919篇
  1999年   56593篇
  1998年   16725篇
  1997年   15017篇
  1996年   16016篇
  1995年   16232篇
  1994年   15099篇
  1993年   14153篇
  1992年   47101篇
  1991年   45750篇
  1990年   43972篇
  1989年   41815篇
  1988年   38760篇
  1987年   38082篇
  1986年   35861篇
  1985年   34637篇
  1984年   26358篇
  1983年   22109篇
  1982年   13851篇
  1981年   12447篇
  1980年   11720篇
  1979年   23544篇
  1978年   17072篇
  1977年   14388篇
  1976年   13183篇
  1975年   13722篇
  1974年   16095篇
  1973年   15397篇
  1972年   14173篇
  1971年   13037篇
  1970年   11880篇
  1969年   11102篇
排序方式: 共有10000条查询结果,搜索用时 8 毫秒
981.
982.
This study aimed to determine whether a weight-adjusted dose of subcutaneous enoxaparin is as effective and safe as oral acenocoumarol for the secondary prophylaxis of pulmonary embolism. Three hundred and eighty consecutive noncancer outpatients hospitalized with an episode of symptomatic pulmonary embolism selected treatment with acenocoumarol or enoxaparin at a dose of 1 mg/kg once daily after being informed of the type of administration and expected frequency of laboratory monitoring for both medicinal products. Endpoints were symptomatic recurrent thromboembolic events evaluated by standard objective testing, and a composite endpoint of recurrent venous thromboembolism, major bleeding, and death from any cause. One hundred and ninety-nine patients (52%) chose acenocoumarol therapy and 181 chose enoxaparin monotherapy. Four patients in the enoxaparin group (2.2%) and six patients in the acenocoumarol group (3%) had an objective thromboembolic recurrence (hazard ratio, 1.35; 95% confidence interval, 0.38-4.79; P = 0.64). Nine patients in the enoxaparin group (5.0%) had a hemorrhagic complication compared with 11 in the acenocoumarol group (5.5%) (P = 0.81). The hospital length of stay was shorter with enoxaparin compared with acenocoumarol (11 versus 16 days, P = 0.0001). Enoxaparin is as effective and safe as acenocoumarol in the secondary prevention of recurrent thromboembolic disease and is associated with shorter hospitalization.  相似文献   
983.
Pulmonary arterial hypertension (PAH) is a disease of the small vessels in which there is a substantial increase in pulmonary vascular resistance leading to right ventricle failure and death. Invasive haemodynamic evaluation is mandatory not only for diagnosis confirmation but also to address prognosis and eligibility for the use of calcium-channel blockers through an acute vasodilator challenge. Noninvasive surrogate response markers to the acute vasodilator test have been sought. In the present study, the relationship between pulmonary artery distensibility, assessed using magnetic resonance imaging (MRI), and response to acute vasodilator tests was investigated. In total, 19 patients diagnosed with idiopathic PAH without any specific treatment were evaluated. Within a 48-h window after pulmonary artery catheterisation, patients underwent cardiac MRI. Cardiac index, calculated after the determination (invasively and noninvasively) of cardiac output, showed excellent correlation, as did right atrial pressure and right ventricle ejection fraction. Pulmonary artery distensibility was significantly higher in responders. A receiver operating characteristic curve analysis has shown that 10% distensibility was able to differentiate responders from nonresponders with 100% sensitivity and 56% specificity. The present findings suggest that magnetic resonance imaging and pulmonary artery distensibility may be useful noninvasive tools for the evaluation of patients with pulmonary hypertension.  相似文献   
984.
985.
986.
987.
Primary squamous cell carcinoma is an extremely rare tumour of the thyroid gland. A case of an elderly lady who was diagnosed to have primary squamous cell carcinoma of the thyroid gland is presented and the role of radiotherapy is discussed.  相似文献   
988.
989.
Pleural effusion is a common complication of various diseases. Conventional methods are not always capable of establishing the cause of pleural effusion, so alternative tests are needed. The aim of this study was to explore means of discriminating between different pleural effusion groups, malignant, parapneumonic and tuberculous, based on the combined function of seven biological markers. Adenosine deaminase (ADA), interferon-gamma, C-reactive protein (CRP), carcinoembryonic antigen, interleukin-6, tumour necrosis factor-alpha and vascular endothelial growth factor concentration levels were measured in pleural fluid from 45 patients with malignant, 15 with parapneumonic and 12 with tuberculous pleural effusion. Receiver operating characteristic curve analysis, multinomial logit modelling and canonical variate analysis were applied to discriminate the pleural effusion groups. The three groups could be discriminated successfully using the measured markers. The most important parameters for discrimination were ADA and CRP concentration levels. An individual with an ADA concentration level of >45 U.L(-1) and a CRP concentration of <4 mg.dL(-1) was more likely to belong to the tuberculous pleural effusion group, whereas one with an ADA concentration level of <40 U.L(-1) and a CRP concentration of >6 mg.dL(-1) was more likely to belong to the parapneumonic pleural effusion group, and one with a CRP concentration of <4 mg.dL(-1) to the malignant pleural effusion group. The combination of adenosine deaminase and C-reactive protein levels might be sufficient for discriminating between the three different groups of exudative pleural effusion: malignant, tuberculous and parapneumonic.  相似文献   
990.
Steroid hormones play an essential role in the ovarian cyclicity control and the progress of pregnancy. One of the crucial enzymes in the steroidogenesis is 3beta-hydroxysteroid dehydrogenase/Delta5-Delta4 isomerase (3betaHSD). The aim of the present study was to localize both 3betaHSD mRNA and protein in the ovary of pregnant swine. The immunolocalization of 3betaHSD was performed on paraplast sections of follicles and corpora lutea obtained on various days of gestation: 10, 18, 32, 50, 71 and 90 POST COITUM (p.c.). The obtained results were compared with those concerning follicular and luteal development in the ovaries of the cycling pig. Differences in 3betaHSD distribution between the ovarian follicles of cycling and pregnant pigs were concerned mainly in the pattern of immunostaining of the theca interna cells. In the porcine ovaries obtained on various days of pregnancy, some follicles exhibited positive immunostaining in most theca interna cells, while in other follicles this enzyme was expressed only in a relatively small percentage of theca interna cells. In the corpora lutea of the estrous cycle and pregnancy changes in the pattern of immunostaining were observed. At early and mid pregnancy (up to 71 day p.c.) 3betaHSD was observed in the large luteal cells while on day 71 p.c. the enzyme was present exclusively in the small luteal cells. The expression of 3betaHSD mRNA was detected by the use of RT-PCR technique in all investigated samples isolated at different stages of pregnancy.  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