全文获取类型
收费全文 | 2846篇 |
免费 | 179篇 |
国内免费 | 14篇 |
专业分类
耳鼻咽喉 | 22篇 |
儿科学 | 76篇 |
妇产科学 | 30篇 |
基础医学 | 371篇 |
口腔科学 | 82篇 |
临床医学 | 413篇 |
内科学 | 574篇 |
皮肤病学 | 23篇 |
神经病学 | 152篇 |
特种医学 | 98篇 |
外科学 | 584篇 |
综合类 | 17篇 |
一般理论 | 2篇 |
预防医学 | 228篇 |
眼科学 | 23篇 |
药学 | 148篇 |
中国医学 | 8篇 |
肿瘤学 | 188篇 |
出版年
2023年 | 17篇 |
2022年 | 37篇 |
2021年 | 71篇 |
2020年 | 39篇 |
2019年 | 73篇 |
2018年 | 77篇 |
2017年 | 50篇 |
2016年 | 52篇 |
2015年 | 62篇 |
2014年 | 67篇 |
2013年 | 99篇 |
2012年 | 194篇 |
2011年 | 172篇 |
2010年 | 106篇 |
2009年 | 102篇 |
2008年 | 186篇 |
2007年 | 209篇 |
2006年 | 201篇 |
2005年 | 172篇 |
2004年 | 181篇 |
2003年 | 153篇 |
2002年 | 110篇 |
2001年 | 44篇 |
2000年 | 33篇 |
1999年 | 36篇 |
1998年 | 32篇 |
1997年 | 26篇 |
1996年 | 15篇 |
1995年 | 18篇 |
1994年 | 13篇 |
1992年 | 30篇 |
1991年 | 31篇 |
1990年 | 33篇 |
1989年 | 17篇 |
1988年 | 20篇 |
1987年 | 23篇 |
1986年 | 20篇 |
1985年 | 25篇 |
1984年 | 15篇 |
1983年 | 12篇 |
1982年 | 12篇 |
1981年 | 9篇 |
1980年 | 13篇 |
1979年 | 10篇 |
1976年 | 14篇 |
1974年 | 8篇 |
1973年 | 10篇 |
1972年 | 13篇 |
1971年 | 13篇 |
1969年 | 10篇 |
排序方式: 共有3039条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
5.
6.
7.
Bing Feng P. Hendrik Pretorius Troy H. Farncombe Seth T. Dahlberg Manoj V. Narayanan Miles N. Wernick Anna M. Celler Jeffrey A. Leppo Michael A. King 《Journal of nuclear cardiology》2006,13(3):354-361
BACKGROUND: Dynamic single photon emission computed tomography (SPECT) acquisition and reconstruction of early poststress technetium 99m teboroxime washout images has been shown to be useful in the detection of coronary disease. Assessment of poststress regional wall motion may offer additional use in assessing coronary disease. Our goal was to investigate the feasibility of simultaneously imaging myocardial ischemia and transient poststress akinesis using gated-dynamic SPECT. METHODS AND RESULTS: A gated-dynamic mathematical cardiac torso (MCAT) phantom was developed to model both teboroxime kinetics and cardiac regional wall motion. A lesion was simulated as having delayed poststress teboroxime washout together with a transient poststress wall motion abnormality. Gated projection data were created to represent a 3-headed SPECT system undergoing a total rotation of 480 degrees . The dynamic expectation-maximization reconstruction algorithm with postsmoothing across gating intervals by Wiener filtering, and the ordered-subset expectation maximization reconstruction algorithm with 3-point smoothing across gating intervals were compared. Compared with the ordered-subset expectation maximization with 3-point smoothing, the dynamic expectation-maximization algorithm with Wiener filtering was able to produce visually higher-quality images and more accurate left ventricular ejection fraction estimates. CONCLUSION: From simulations, we conclude that changing cardiac function and tracer localization possibly can be assessed by using a gated-dynamic acquisition protocol combined with a 5-dimensional reconstruction strategy. 相似文献
8.
Gregory C Gray Troy McCarthy Mark G Lebeck David P Schnurr Kevin L Russell Adriana E Kajon Marie L Landry Diane S Leland Gregory A Storch Christine C Ginocchio Christine C Robinson Gail J Demmler Michael A Saubolle Sue C Kehl Rangaraj Selvarangan Melissa B Miller James D Chappell Danielle M Zerr Deanna L Kiska Diane C Halstead Ana W Capuano Sharon F Setterquist Margaret L Chorazy Jeffrey D Dawson Dean D Erdman 《Clinical infectious diseases》2007,45(9):1120-1131
BACKGROUND: Recently, epidemiological and clinical data have revealed important changes with regard to clinical adenovirus infection, including alterations in antigenic presentation, geographical distribution, and virulence of the virus. METHODS: In an effort to better understand the epidemiology of clinical adenovirus infection in the United States, we adopted a new molecular adenovirus typing technique to study clinical adenovirus isolates collected from 22 medical facilities over a 25-month period during 2004-2006. A hexon gene sequence typing method was used to characterize 2237 clinical adenovirus-positive specimens, comparing their sequences with those of the 51 currently recognized prototype human adenovirus strains. In a blinded comparison, this method performed well and was much faster than the classic serologic typing method. RESULTS: Among civilians, the most prevalent adenovirus types were types 3 (prevalence, 34.6%), 2 (24.3%), 1 (17.7%), and 5 (5.3%). Among military trainees, the most prevalent types were types 4 (prevalence, 92.8%), 3 (2.6%), and 21 (2.4%). CONCLUSIONS: For both populations, we observed a statistically significant increasing trend of adenovirus type 21 detection over time. Among adenovirus isolates recovered from specimens from civilians, 50% were associated with hospitalization, 19.6% with a chronic disease condition, 11% with a bone marrow or solid organ transplantation, 7.4% with intensive care unit stay, and 4.2% with a cancer diagnosis. Multivariable risk factor modeling for adenovirus disease severity found that age <7 years (odds ratio [OR], 3.2; 95% confidence interval [CI], 1.4-7.4), chronic disease (OR, 3.6; 95% CI, 2.6-5.1), recent transplantation (OR, 2.7; 95% CI, 1.3-5.2), and adenovirus type 5 (OR, 2.7; 95% CI, 1.5-4.7) or type 21 infection (OR, 7.6; 95% CI, 2.6-22.3) increased the risk of severe disease. 相似文献
9.
10.