全文获取类型
收费全文 | 14965篇 |
免费 | 1193篇 |
国内免费 | 38篇 |
专业分类
耳鼻咽喉 | 81篇 |
儿科学 | 387篇 |
妇产科学 | 188篇 |
基础医学 | 1959篇 |
口腔科学 | 296篇 |
临床医学 | 1612篇 |
内科学 | 2929篇 |
皮肤病学 | 162篇 |
神经病学 | 1483篇 |
特种医学 | 611篇 |
外科学 | 2116篇 |
综合类 | 165篇 |
一般理论 | 32篇 |
预防医学 | 1762篇 |
眼科学 | 250篇 |
药学 | 1044篇 |
中国医学 | 20篇 |
肿瘤学 | 1099篇 |
出版年
2023年 | 132篇 |
2022年 | 211篇 |
2021年 | 488篇 |
2020年 | 299篇 |
2019年 | 423篇 |
2018年 | 467篇 |
2017年 | 374篇 |
2016年 | 391篇 |
2015年 | 459篇 |
2014年 | 566篇 |
2013年 | 786篇 |
2012年 | 1196篇 |
2011年 | 1187篇 |
2010年 | 719篇 |
2009年 | 604篇 |
2008年 | 1039篇 |
2007年 | 990篇 |
2006年 | 938篇 |
2005年 | 932篇 |
2004年 | 862篇 |
2003年 | 779篇 |
2002年 | 651篇 |
2001年 | 146篇 |
2000年 | 100篇 |
1999年 | 114篇 |
1998年 | 127篇 |
1997年 | 102篇 |
1996年 | 86篇 |
1995年 | 68篇 |
1994年 | 68篇 |
1993年 | 52篇 |
1992年 | 57篇 |
1991年 | 57篇 |
1990年 | 56篇 |
1989年 | 38篇 |
1988年 | 32篇 |
1987年 | 44篇 |
1986年 | 34篇 |
1985年 | 33篇 |
1984年 | 48篇 |
1983年 | 38篇 |
1982年 | 36篇 |
1981年 | 32篇 |
1980年 | 27篇 |
1979年 | 38篇 |
1978年 | 42篇 |
1977年 | 23篇 |
1976年 | 22篇 |
1973年 | 26篇 |
1972年 | 22篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
5.
Thomas Asendorf Robin Henderson Heinz Schmidli Tim Friede 《Statistics in medicine》2019,38(9):1503-1528
In some diseases, such as multiple sclerosis, lesion counts obtained from magnetic resonance imaging (MRI) are used as markers of disease progression. This leads to longitudinal, and typically overdispersed, count data outcomes in clinical trials. Models for such data invariably include a number of nuisance parameters, which can be difficult to specify at the planning stage, leading to considerable uncertainty in sample size specification. Consequently, blinded sample size re-estimation procedures are used, allowing for an adjustment of the sample size within an ongoing trial by estimating relevant nuisance parameters at an interim point, without compromising trial integrity. To date, the methods available for re-estimation have required an assumption that the mean count is time-constant within patients. We propose a new modeling approach that maintains the advantages of established procedures but allows for general underlying and treatment-specific time trends in the mean response. A simulation study is conducted to assess the effectiveness of blinded sample size re-estimation methods over fixed designs. Sample sizes attained through blinded sample size re-estimation procedures are shown to maintain the desired study power without inflating the Type I error rate and the procedure is demonstrated on MRI data from a recent study in multiple sclerosis. 相似文献
6.
7.
8.
Kate Ridley Tim S Olds Alison Hill 《The international journal of behavioral nutrition and physical activity》2006,3(1):10-11
Background
Self-report recall questionnaires are commonly used to measure physical activity, energy expenditure and time use in children and adolescents. However, self-report questionnaires show low to moderate validity, mainly due to inaccuracies in recalling activity in terms of duration and intensity. Aside from recall errors, inaccuracies in estimating energy expenditure from self-report questionnaires are compounded by a lack of data on the energy cost of everyday activities in children and adolescents. This article describes the development of the Multimedia Activity Recall for Children and Adolescents (MARCA), a computer-delivered use-of-time instrument designed to address both the limitations of self-report recall questionnaires in children, and the lack of energy cost data in children. 相似文献9.
John R. Jarrett M.D. 《Aesthetic plastic surgery》1990,14(1):87-92
Immediate reconstruction of more than 1000 breasts was performed on high-risk patients on whom a prophylactic mastectomy was done. The mastectomy removes as much breast tissue as possible while leaving sufficient skin, and possibly the nipple-areola complex, to enable immediate reconstruction. The creation of symmetrical, well-balanced muscle pockets for the implant is the most important factor in producing satisfactory results in these cases. 相似文献
10.
D J Kupfer B G Pollock J M Perel D B Jarrett A B McEachran J M Miewald 《Psychiatry research》1991,36(3):279-289
An i.v. challenge dose of clomipramine (12.5 mg) was given to eight outpatients with major depression. The procedure facilitated the examination of all-night sleep and sleep-related neuroendocrine changes (cortisol, growth hormone, and prolactin). In comparison to baseline saline nights, the patients experienced a profound suppression of rapid eye movement (REM) sleep throughout the night with no rebound recovery in the second half of the night. Furthermore, REM-suppressing effects were noted on the following no-drug night. In contrast, little effect on delta wave sleep was found, except for increased consolidation of delta waves within stage 3 and 4 sleep. Delta sleep measures were significantly correlated with levels of cortisol and growth hormone. 相似文献