全文获取类型
收费全文 | 1571篇 |
免费 | 71篇 |
国内免费 | 81篇 |
专业分类
耳鼻咽喉 | 5篇 |
儿科学 | 81篇 |
妇产科学 | 12篇 |
基础医学 | 172篇 |
口腔科学 | 37篇 |
临床医学 | 267篇 |
内科学 | 362篇 |
皮肤病学 | 38篇 |
神经病学 | 64篇 |
特种医学 | 340篇 |
外科学 | 74篇 |
综合类 | 26篇 |
预防医学 | 48篇 |
眼科学 | 12篇 |
药学 | 113篇 |
肿瘤学 | 72篇 |
出版年
2022年 | 5篇 |
2021年 | 14篇 |
2020年 | 6篇 |
2019年 | 16篇 |
2018年 | 13篇 |
2017年 | 15篇 |
2016年 | 13篇 |
2015年 | 27篇 |
2014年 | 19篇 |
2013年 | 38篇 |
2012年 | 36篇 |
2011年 | 29篇 |
2010年 | 55篇 |
2009年 | 58篇 |
2008年 | 36篇 |
2007年 | 68篇 |
2006年 | 37篇 |
2005年 | 40篇 |
2004年 | 15篇 |
2003年 | 25篇 |
2002年 | 23篇 |
2001年 | 25篇 |
2000年 | 32篇 |
1999年 | 37篇 |
1998年 | 96篇 |
1997年 | 94篇 |
1996年 | 112篇 |
1995年 | 90篇 |
1994年 | 88篇 |
1993年 | 78篇 |
1992年 | 28篇 |
1991年 | 34篇 |
1990年 | 34篇 |
1989年 | 40篇 |
1988年 | 49篇 |
1987年 | 41篇 |
1986年 | 40篇 |
1985年 | 36篇 |
1984年 | 19篇 |
1983年 | 22篇 |
1982年 | 21篇 |
1981年 | 27篇 |
1980年 | 21篇 |
1979年 | 7篇 |
1978年 | 11篇 |
1977年 | 18篇 |
1976年 | 13篇 |
1975年 | 7篇 |
1971年 | 3篇 |
1935年 | 2篇 |
排序方式: 共有1723条查询结果,搜索用时 140 毫秒
1.
2.
3.
Floriano P Silva-Junior Herbert L M Guedes Laura C Garvey Aniesse S Aguiar Saulo C Bourguignon Enrico Di Cera Salvatore Giovanni-De-Simone 《Toxicon》2007,50(1):18-31
BJ-48, a serine protease from the venom of Bothrops jararacussu, was purified to homogeneity using affinity chromatography on p-aminobenzamidine-agarose followed by HPLC gel filtration. BJ-48 presented 52kDa by SDS-PAGE analysis and 48,036Da by electron spray mass spectrometry. The enzyme was shown to be highly glycosylated with 42% of N-linked carbohydrates composed of Fuc(1):GalN(4):GlcN(5):Gal(1):Man(2) and a high content of sialic acid residues (8-12%). BJ-48 had optimal esterase activity at pH 7.5 and displayed maximum catalytic rate at 50 degrees C. Its hydrolytic activity was strongly inhibited by aprotinin and dithiothreitol while N-tosyl-l-phenylalanine chloromethyl ketone, 6-aminocaproic acid, E-64 and soybean trypsin inhibitor (SBTI) were ineffective. The kinetics of BJ-48 with chromogenic substrates revealed an unprecedented selectivity (10(4)-fold) for Arg over Lys in P1. BJ-48 proved to be a thrombin-like enzyme (TLE) with a specific fibrinogen-clotting activity of 73.4NIH units/mg. The TLE rapidly digested human fibrinogen Bbeta chain, but the Aalpha chain was cleaved specifically to release fibrinopeptide A with k(cat)/K(m)=2.1muM(-1)s(-1). The TLE showed no activity toward other thrombin substrates like protein C, protease-activated receptor-1 or inhibitors such as hirudin and antithrombin. A non-denaturing procedure using PNGase F and neuraminidase followed by hydrophobic interaction chromatography was employed to obtain active BJ-48 forms with variable carbohydrate content. Compared to the native enzyme, total or partially deglycosylated BJ-48 forms presented up to 2-fold reduction in their specific activities upon heating at 55/65 degrees C or treatment with SBTI. These results point out a role for BJ-48 glycosylation in thermostability and controlling the access of some canonical protein inhibitors to the active site. 相似文献
4.
5.
6.
7.
8.
The prevalence of antibodies to 13 antigens of Legionellaceae were compared in three populations: 583 blood donors, 140 tuberculosis patients and 66 patients with acute non Legionellosis pneumonia. Antibody levels were determined by indirect immunofluorescence (IFA) using formalized antigens prepared from bacteria developed in embryonated hen yolk sac. The very weak prevalence of anti L. pneumophila antibodies in a healthy population [almost nil for serogroups 2, 3, 4 and 5; 1.5% for serogroup 6, maximum of 2.5% for serogroup 1 (titres of 16)] confirms the positive and presumptive criteria that have been recommended by Centers for Disease Control (CDC). But as regards the other Legionellae studied, these criteria cannot be applied owing to the prevalences that are higher in healthy populations (until 14.5% with levels of 16-32 and 1% with levels of 64-128 for L. bozemanii) and clearly amplified in tuberculosis patients and in acute pneumonia. Although the significance of these antibodies remains to be discussed, with formalized antigens, it seems reasonable as regards these species to assign a threshold of 256 for the presumptive and positive criteria following seroconversion. 相似文献
9.
Y Leskinen JP Salenius T Lehtim?ki H Huhtala H Saha 《American journal of kidney diseases》2002,40(3):472-479
BACKGROUND: Knowledge of the prevalence of peripheral arterial disease (PAD) in patients with chronic renal failure (CRF) is limited because of a lack of uniformity in disease definition and recognition. Furthermore, little is known of the prevalence of medial arterial calcification (MAC) in patients with CRF. Our goal is to study the prevalence of PAD and MAC defined by ankle brachial index (ABI) or toe brachial index (TBI) measurements in a Finnish population of patients with CRF consisting of predialysis and dialysis patients, as well as renal transplant recipients. METHODS: We examined 136 patients with CRF and 59 control subjects. Fifty-nine of the patients with CRF had moderate to severe predialysis CRF, 36 patients were on dialysis treatment, and 41 were renal transplant recipients. Mean age of patients was 51.9 +/- 11.5 years, and 39 patients (29%) had diabetes. ABI and TBI were measured by means of photoplethysmography. The definition of PAD required an ABI value of 0.90 or less, a TBI value of 0.60 or less, or a previous positive lower-extremity angiogram result. ABI values of 1.3 or greater or incompressible arteries at ankle level indicated MAC. The presence of claudication was determined by an interview. RESULTS: Prevalences of PAD on this study were 22.0% in patients with predialysis CRF, 30.6% in patients on dialysis treatment, 14.6% in renal transplant recipients, and 1.7% in the control group (P = 0.001). Prevalences of MAC were 23.7%, 41.7%, 23.1%, and 3.4% (P < 0.001), respectively. Only 9 patients had claudication, and 6 of those patients had PAD. CONCLUSION: Both asymptomatic PAD and MAC are common in patients with CRF. Therefore, we recommend the use of both ABI and TBI measurements in the evaluation of PAD in patients with CRF. 相似文献
10.
We used arthrotomography to study the glenoid labrum in 114 patients. Sixty-nine of the patients had anatomic instability of the shoulder (including recurrent dislocation and subluxation of the shoulder), and 45 patients had functional instability of the shoulder (denoted by chronic pain, clicking of the joint, and the sensation that an unstable condition exists without the objective signs of it). Labral tears were revealed arthrotomographically in 86% of the patients with anatomic instability, while only 40% of the patients with functional instability had labral abnormalities, and these were primarily of minor severity. Fifty-six patients (44 of whom had anatomic instability; 12, functional instability) required surgery. The surgical findings were correlated with the arthrotomographic findings, and no false-positive results were revealed. However, arthrotomography demonstrated only part of the pathologic condition of two patients. These results confirm that there is a strong correlation between labral pathologic conditions and anatomic instability of the shoulder. Arthrotomographic studies have a great impact on the selection of therapy in cases of both anatomic and functional instability of the shoulder. 相似文献