全文获取类型
收费全文 | 29957篇 |
免费 | 2202篇 |
国内免费 | 60篇 |
专业分类
耳鼻咽喉 | 181篇 |
儿科学 | 1200篇 |
妇产科学 | 954篇 |
基础医学 | 3474篇 |
口腔科学 | 376篇 |
临床医学 | 4612篇 |
内科学 | 5577篇 |
皮肤病学 | 489篇 |
神经病学 | 2949篇 |
特种医学 | 599篇 |
外科学 | 2559篇 |
综合类 | 573篇 |
一般理论 | 33篇 |
预防医学 | 4187篇 |
眼科学 | 492篇 |
药学 | 1988篇 |
1篇 | |
中国医学 | 35篇 |
肿瘤学 | 1940篇 |
出版年
2023年 | 205篇 |
2022年 | 285篇 |
2021年 | 613篇 |
2020年 | 419篇 |
2019年 | 680篇 |
2018年 | 795篇 |
2017年 | 615篇 |
2016年 | 684篇 |
2015年 | 728篇 |
2014年 | 999篇 |
2013年 | 1559篇 |
2012年 | 2202篇 |
2011年 | 2147篇 |
2010年 | 1260篇 |
2009年 | 1185篇 |
2008年 | 1824篇 |
2007年 | 1998篇 |
2006年 | 1877篇 |
2005年 | 1928篇 |
2004年 | 1812篇 |
2003年 | 1636篇 |
2002年 | 1587篇 |
2001年 | 333篇 |
2000年 | 318篇 |
1999年 | 328篇 |
1998年 | 345篇 |
1997年 | 258篇 |
1996年 | 219篇 |
1995年 | 227篇 |
1994年 | 211篇 |
1993年 | 180篇 |
1992年 | 191篇 |
1991年 | 161篇 |
1990年 | 172篇 |
1989年 | 165篇 |
1988年 | 124篇 |
1987年 | 132篇 |
1986年 | 138篇 |
1985年 | 146篇 |
1984年 | 153篇 |
1983年 | 108篇 |
1982年 | 140篇 |
1981年 | 108篇 |
1980年 | 102篇 |
1979年 | 83篇 |
1978年 | 77篇 |
1977年 | 67篇 |
1975年 | 61篇 |
1974年 | 47篇 |
1972年 | 52篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
Workplace status and risk of hypertension among hourly and salaried aluminum manufacturing employees
Jane Ellen Clougherty Ellen A. Eisen Martin D. Slade Ichiro Kawachi Mark R. Cullen 《Social science & medicine (1982)》2009
An inverse relationship between workplace status and morbidity is well established; higher job status has been associated with reduced risks of heart disease, hypertension, and injury. Most research on job status, however, has focused on salaried populations, and it remains unclear whether job status operates similarly among hourly workers. Our objectives were to examine whether hourly status itself influences risk of hypertension after adjustment for socioeconomic confounders, and to explore the role of fine-scale job grade on hypertension incidence within hourly and salaried groups. We examined data for 14,999 aluminum manufacturing employees in 11 plants across the U.S., using logistic regression with adjustment for age, sex, race/ethnicity and other individual characteristics. Propensity score restriction was used to identify comparable groups of hourly and salaried employees, reducing confounding by sociodemographic characteristics. Job grade (coded 1 through 30, within hourly and salaried groups) was examined as a more refined measure of job status. Hourly status was associated with an increased risk of hypertension, after propensity restriction and adjustment for confounders. The observed effect of hourly status was stronger among women, although the propensity-restricted cohort was disproportionately male (96%). Among salaried workers, higher job grade was not consistently associated with decreased risk; among hourly employees, however, there was a significant trend, with higher job grades more protective against hypertension. Increasing the stringency of hypertension case criteria also increased the risk of severe or persistent hypertension for hourly employees. 相似文献
32.
33.
A cross-sectional survey of patients' beliefs about stress and their help-seeking behaviour
下载免费PDF全文
![点击此处可从《The British journal of general practice》网站下载免费的PDF全文](/ch/ext_images/free.gif)
BACKGROUND: Stress has become an increasingly common presentation in general practice. This may relate to an increase in stress in people's lives or a change in the meaning of stress and its conceptualisation as a legitimate problem for the GP. AIM: To explore patients' beliefs about stress, their association with help-seeking behaviour, and to examine differences by ethnic group. DESIGN OF STUDY: Cross-sectional survey of general practice patients attending to see their GP. SETTING: An inner-city London practice. METHOD: Consecutive general practice patients completed a questionnaire, which involved rating a series of symptoms for the extent to which they were associated with stress and describing their help-seeking behaviour. In total, 548 patients completed the questionnaire. Most patients described themselves as black Caribbean (n = 163), black African (n = 48), or white British (n = 187). RESULTS: The symptoms most frequently associated with stress were sleeping problems, feeling depressed, feeling panicky, having high blood pressure and feeling anxious; feeling ashamed, experiencing indigestion, having diarrhoea, feeling hot or cold, and suffering from constipation were least commonly associated to stress. This model of stress did not vary by ethnic group. Ethnic group differences were found for the association between the model of stress and help-seeking behaviour. Although white British patients consistently reported that the more a symptom was seen as indicative of stress, the more likely they would be to visit the doctor for that symptom, this association was not found for either black Caribbean or black African patients. CONCLUSIONS: The belief that stress-related symptoms are a legitimate problem for the GP is not universal and varies according to ethnic group. Stress is used by different patients in different ways and offers a variable pathway to the doctor. 相似文献
34.
Insect pest species can have devastating effects on crops. Control of these insect pests is usually achieved by using chemical insecticides. However, there has been much cause for concern with their overuse. Consequently, research has been carried out into alternative forms of control, in particular biological control methods. Recent laboratory studies have indicated that these natural forms of control can induce resistant strains of insect pest. In this paper we present a discrete-time host-pathogen model to describe the interaction between a host (insect species) that can develop a resistant strain and a pathogen (biological control) that can be externally applied to the system. For this model we use a single-state variable for the host population. We show that the proportion of resistance in the population impacts on the viability of the host population. Moreover, when the host population does persist, we explore the interaction between host susceptibility and host population levels. The different scenarios which arise are explained ecologically in terms of trade-offs in intrinsic growth rates, disease susceptibility and intraspecific host competition for the resistant subclass. 相似文献
35.
36.
37.
Katie S Lekx Maryam Fathimani Yves Bureau Gerald Wisenberg Jane Sykes Frank S Prato 《Journal of cardiovascular magnetic resonance》2006,8(5):731-739
PURPOSE: To evaluate qualitative wall motion assessment vs. quantitative wall thickening for the assessment of subtle changes in myocardial systolic function using cine MRI. METHODS: Cine MR images were obtained in 5 canines with a significant coronary artery stenosis and in 2 controls on a 1.5T scanner. Qualitative results were obtained using a numerical scoring system; quantitative analysis was performed using a semi-automatic segmentation program. The techniques were matched and compared using Spearman correlations. RESULTS: All correlations in the experimental group revealed significant but weak to moderate relationships between the qualitative and quantitative results (e.g., at-risk tissue rho = 0.363, p < 0.0001; remote tissue rho = 0.275, p = 0.0002), with each identifying changes in regional function that ensued following creation of the stenosis. Intra-observer variability was reasonable in both methods when repeat analysis on a subset of the data was performed, with both techniques showing a significant correlation between the repeated measurements (quantitative - rho = 0.52, p < 0.0001; qualitative - rho = 0.54, p < 0.0001). CONCLUSION: Both methods were able to detect very limited wall motion abnormalities present in the canines with significant stenosis and either method gives comparable results. 相似文献
38.
K Parsi T Exner D E Connor D D F Ma J E Joseph 《European journal of vascular and endovascular surgery》2007,34(6):731-740
OBJECTIVES: To investigate the in vitro effects of Sodium Tetradecyl Sulphate (STS) and Polidocanol (POL) on clotting tests, clotting factors, platelets and microparticles. MATERIALS AND METHODS: Platelet rich (PRP) and platelet poor (PPP) plasmas were incubated with varying concentrations of STS and POL. Clotting tests, platelet/plasma turbidity, and microparticle studies were performed. Specimens were mixed with individual factor deficient plasmas and clotting factor activities were studied. RESULTS: STS at high concentrations (>0.3%) destroyed platelets, microparticles and the clotting factors V, VII and X. It prolonged all clotting tests including prothrombin time (PT), activated partial thromboplastin time (APTT), non-activated partial thromboplastin time (NAPTT), thrombin time (TT), factor Xa clotting time (XACT) and surface activated clotting time (SACT). Higher concentrations of POL were required to achieve some anticoagulant activity. Low sclerosant concentrations shortened XACT and SACT, and induced release of procoagulant platelet derived microparticles. Increased exposure time resulted in increased procoagulant activity. STS at concentrations higher than 0.5% precipitated a complex containing apolipoprotein b and fibrinogen. CONCLUSIONS: Detergent sclerosants affect the clotting mechanism by interfering with clotting factor activities, procoagulant phospholipids and platelet derived microparticles. STS has more anticoagulant activity than POL in high concentrations. Low concentration sclerosants demonstrate procoagulant activity. 相似文献
39.
Hung-Fat Tse Sukumaran Thambar Yok-Lam Kwong Philip Rowlings Greg Bellamy Jane McCrohon Paul Thomas Bruce Bastian John K F Chan Gladys Lo Chi-Lai Ho Wing-Sze Chan Raymond Y Kwong Anthony Parker Thomas H Hauser Jenny Chan Daniel Y T Fong Chu-Pak Lau 《European heart journal》2007,28(24):2998-3005
AIMS: Experimental studies have demonstrated that bone marrow (BM) cells can induce angiogenesis in ischaemic myocardium. Recently, several non-randomized pilot studies have also suggested that direct BM cells implantation appears to be feasible and safe in patients with severe coronary artery diseases (CAD). METHODS AND RESULTS: We performed a randomized, blinded, and placebo-controlled trial in 28 CAD patients. After BM harvesting, we assigned patients to receive low dose (1 x 10(6) cells/0.1 mL, n = 9), high dose (2 x 10(6) cells/0.1 mL, n = 10) autologous BM cells or control (0.1 mL autologous plasma/injection, n = 9) catheter-based direct endomyocardial injection as guided by electromechanical mapping. Our primary endpoint was the increase in exercise treadmill time and our secondary endpoints were changes in Canadian Cardiovascular Society (CCS) and New York Heart Association (NYHA) class, and myocardial perfusion and left ventricular ejection fraction (LVEF) assessed by single-photon emission computed tomography and magnetic resonance imaging, respectively. A total 422 injections (mean 14.6 +/- 0.7 per patient) were successfully performed at 41 targeted ischaemic regions without any acute complication. Baseline exercise treadmill time was 439 +/- 182 s in controls and 393 +/- 136 s in BM-treated patients, and changed after 6 months to 383 +/- 223s and 464 +/- 196 s [BM treatment effect +0.43 log seconds (+53%), 95% CI 0.11-0.74, P = 0.014]. Compared with placebo injection, BM implantation was associated with a significant increase in LVEF (BM treatment effect +5.4%, 95% CI 0.4-10.3, P = 0.044) and a lower NYHA class (odds ratio for treatment effect 0.12, 95% CI 0.02-0.73, P = 0.021) after 6 months, but CCS reduced similarly in both groups. We observed no acute or long-term complications, including ventricular arrhythmia, myocardial damage, or development of intramyocardial tumour or calcification associated with BM implantation. CONCLUSION: Direct endomyocardial implantation of autologous BM cells significantly improved exercise time, LVEF, and NYHA functional class in patients with severe CAD who failed conventional therapy. 相似文献
40.