全文获取类型
收费全文 | 5216篇 |
免费 | 301篇 |
国内免费 | 19篇 |
专业分类
耳鼻咽喉 | 83篇 |
儿科学 | 427篇 |
妇产科学 | 117篇 |
基础医学 | 497篇 |
口腔科学 | 71篇 |
临床医学 | 349篇 |
内科学 | 1283篇 |
皮肤病学 | 175篇 |
神经病学 | 605篇 |
特种医学 | 229篇 |
外科学 | 501篇 |
综合类 | 141篇 |
一般理论 | 2篇 |
预防医学 | 208篇 |
眼科学 | 101篇 |
药学 | 224篇 |
中国医学 | 9篇 |
肿瘤学 | 514篇 |
出版年
2023年 | 49篇 |
2022年 | 56篇 |
2021年 | 123篇 |
2020年 | 83篇 |
2019年 | 118篇 |
2018年 | 148篇 |
2017年 | 101篇 |
2016年 | 125篇 |
2015年 | 97篇 |
2014年 | 189篇 |
2013年 | 220篇 |
2012年 | 332篇 |
2011年 | 313篇 |
2010年 | 188篇 |
2009年 | 173篇 |
2008年 | 284篇 |
2007年 | 260篇 |
2006年 | 242篇 |
2005年 | 256篇 |
2004年 | 226篇 |
2003年 | 200篇 |
2002年 | 188篇 |
2001年 | 86篇 |
2000年 | 132篇 |
1999年 | 100篇 |
1998年 | 53篇 |
1997年 | 46篇 |
1996年 | 40篇 |
1995年 | 34篇 |
1994年 | 36篇 |
1993年 | 28篇 |
1992年 | 76篇 |
1991年 | 52篇 |
1990年 | 55篇 |
1989年 | 94篇 |
1988年 | 63篇 |
1987年 | 71篇 |
1986年 | 62篇 |
1985年 | 62篇 |
1984年 | 65篇 |
1983年 | 49篇 |
1979年 | 28篇 |
1978年 | 20篇 |
1977年 | 22篇 |
1975年 | 21篇 |
1974年 | 23篇 |
1972年 | 25篇 |
1970年 | 22篇 |
1969年 | 26篇 |
1967年 | 17篇 |
排序方式: 共有5536条查询结果,搜索用时 281 毫秒
1.
2.
3.
K. Bhatia Group of Obstetric Anaesthetists of Lancashire Greater Manchester Mersey Study Collaborators 《Anaesthesia》2022,77(4):389-397
Since the start of the COVID-19 pandemic, few studies have reported anaesthetic outcomes in parturients with SARS-CoV-2 infection. We reviewed the labour analgesic and anaesthetic interventions utilised in symptomatic and asymptomatic parturients who had a confirmed positive test for SARS-CoV-2 across 10 hospitals in the north-west of England between 1 April 2020 and 31 May 2021. Primary outcomes analysed included the analgesic/anaesthetic technique utilised for labour and caesarean birth. Secondary outcomes included a comparison of maternal characteristics, caesarean birth rate, maternal critical care admission rate along with adverse composite neonatal outcomes. A positive SARS-CoV-2 test was recorded in 836 parturients with 263 (31.4%) reported to have symptoms of COVID-19. Neuraxial labour analgesia was utilised in 104 (20.4%) of the 509 parturients who went on to have a vaginal birth. No differences in epidural analgesia rates were observed between symptomatic and asymptomatic parturients (OR 1.03, 95%CI 0.64–1.67; p = 0.90). The neuraxial anaesthesia rate in 310 parturients who underwent caesarean delivery was 94.2% (95%CI 90.6–96.0%). The rates of general anaesthesia were similar in symptomatic and asymptomatic parturients (6% vs. 5.7%; p = 0.52). Symptomatic parturients were more likely to be multiparous (OR 1.64, 95%CI 1.19–2.22; p = 0.002); of Asian ethnicity (OR 1.54, 1.04–2.28; p = 0.03); to deliver prematurely (OR 2.16, 95%CI 1.47–3.19; p = 0.001); have a higher caesarean birth rate (44.5% vs. 33.7%; OR 1.57, 95%CI 1.16–2.12; p = 0.008); and a higher critical care utilisation rate both pre- (8% vs. 0%, p = 0.001) and post-delivery (11% vs. 3.5%; OR 3.43, 95%CI 1.83–6.52; p = 0.001). Eight neonates tested positive for SARS-CoV-2 while no differences in adverse composite neonatal outcomes were observed between those born to symptomatic and asymptomatic mothers (25.8% vs. 23.8%; OR 1.11, 95%CI 0.78–1.57; p = 0.55). In women with COVID-19, non-neuraxial analgesic regimens were commonly utilised for labour while neuraxial anaesthesia was employed for the majority of caesarean births. Symptomatic women with COVID-19 are at increased risk of significant maternal morbidity including preterm birth, caesarean birth and peripartum critical care admission. 相似文献
4.
5.
Nirmanmoh Bhatia Buddhadeb Dawn Tariq S. Siddiqui Marcus F. Stoddard 《Texas Heart Institute journal / from the Texas Heart Institute of St. Luke's Episcopal Hospital, Texas Children's Hospital》2015,42(1):16-24
Determining aortic stenosis (AS) severity is clinically important. Calculating aortic valve (AV) area by means of the continuity equation assumes a circular left ventricular outflow tract (LVOT). The full impact of this assumption in calculating AV area is unknown. Predictors of noncircular LVOT shape in patients with AS are undefined.In 109 adult patients with AS who underwent multiplanar transesophageal echocardiography, we calculated AV area by means of the standard continuity method and by a modified method involving planimetric LVOT area.We found 54 circular, 37 horizontal-oval, 8 vertical-oval, and 10 irregular LVOTs. Area derived by direct planimetry correlated better with the modified than the standard continuity method (r=0.89 vs r=0.85; both P=0.0001). Valve areas of patients with mild, moderate, or severe AS by planimetry were more often mischaracterized with use of the standard than modified method (29 vs 18; P <0.0001). Horizontal-oval AV area derived by planimetry (1.28 ± 0.55 cm2) was underestimated by the standard method (1.05 ± 0.47 cm2; P=0.001), but not by the modified method. Congenital AV morphology and low cardiac index were the only multivariate predictors of horizontal-oval shape. Low cardiac index was the only predictor of noncircular shape.More than half our patients with AS had noncircular LVOTs. Using the modified method reduces mischaracterizations of AS severity. Congenital AV morphology and low cardiac index predict horizontal-oval or noncircular shape. These data suggest the value of direct LVOT measurement to calculate AS severity in patients who have congenital AV or a low cardiac index. 相似文献
6.
Girish S. Mishra Arpan Bhatia 《Indian journal of otolaryngology and head and neck surgery》2007,59(3):296-297
Dermatofibrosarcoma protuberance of head and neck is a rare neoplasm and accounts for less than one percent of Head and Neck Neoplasm. The objective of this report is to understand etiology, presentation, histopathologic identification and treatment option for this tumour. The goal of current report is to acquaint the clinician with presentation and treatment option for this disease. 相似文献
7.
Gayatri Vasudevan R. Chandra B. Vishnu Bhat B. D. Bhatia 《Indian Journal of Thoracic and Cardiovascular Surgery》1993,9(1):42-44
We present two cases of neonatal pleural effusion, a relatively rare condition, most commonly due to chylothorax. One had
bilateral hypoplastic lungs and the other suffered birth asphyxia. Both died before any treatment could be initiated. 相似文献
8.
There are very few reported cases of milk of calcium in the ureter. Its presence in the ureter is quite unusual and is the
subject of the present report. 相似文献
9.
Leeta Alison Green Khoi Nguyen Bijan Berenji Meera Iyer Eileen Bauer Jorge R Barrio Mohammad Namavari Nagichettiar Satyamurthy Sanjiv S Gambhir 《Journal of nuclear medicine》2004,45(9):1560-1570
Reporter probe 9-(4-18F-fluoro-3-[hydroxymethyl]butyl)guanine (18F-FHBG) and reporter gene mutant herpes simplex virus type 1 thymidine kinase (HSV1-sr39tk) have been used for imaging reporter gene expression with PET. Current methods for quantitating the images using the percentage injected dose per gram of tissue do not distinguish between the effects of probe transport and subsequent phosphorylation. We therefore investigated tracer kinetic models for 18F-FHBG dynamic microPET data and noninvasive methods for determining blood time-activity curves in an adenoviral gene delivery model in mice. METHODS: 18F-FHBG (approximately 7.4 MBq [approximately 200 microCi]) was injected into 4 mice; 18F-FHBG concentrations in plasma and whole blood were measured from mouse heart left ventricle (LV) direct sampling. Replication-incompetent adenovirus (0-2 x 10(9) plaque-forming units) with the E1 region deleted (n = 8) or replaced by HSV1-sr39tk (n = 18) was tail-vein injected into mice. Mice were dynamically scanned using microPET (approximately 7.4 MBq [approximately 200 microCi] 18F-FHBG) over 1 h; regions of interest were drawn on images of the heart and liver. Serial whole blood 18F-FHBG concentrations were measured in 6 of the mice by LV sampling, and 1 least-squares ratio of the heart image to the LV time-activity curve was calculated for all 6 mice. For 2 control mice and 9 mice expressing HSV1-sr39tk, heart image (input function) and liver image time-activity curves (tissue curves) were fit to 2- and 3-compartment models using Levenberg-Marquardt nonlinear regression. The models were compared using an F statistic. HSV1-sr39TK enzyme activity was determined from liver samples and compared with model parameter estimates. For another 3 control mice and 6 HSV1-sr39TK-positive mice, the model-predicted relative percentage of metabolites was compared with high-performance liquid chromatography analysis. RESULTS: The ratio of 18F-FHBG in plasma to whole blood was 0.84 +/- 0.05 (mean +/- SE) by 30 s after injection. The least-squares ratio of the heart image time-activity curve to the LV time-activity curve was 0.83 +/- 0.02, consistent with the recovery coefficient for the partial-volume effect (0.81) based on independent measures of heart geometry. A 3-compartment model best described 18F-FHBG kinetics in mice expressing HSV1-sr39tk in the liver; a 2-compartment model best described the kinetics in control mice. The 3-compartment model parameter, k3, correlated well with the HSV1-sr39TK enzyme activity (r2 = 0.88). CONCLUSION: 18F-FHBG equilibrates rapidly between plasma and whole blood in mice. Heart image time-activity curves corrected for partial-volume effects well approximate LV time-activity curves and can be used as input functions for 2- and 3-compartment models. The model parameter k3 from the 3-compartment model can be used as a noninvasive estimate for HSV1-sr39TK reporter protein activity and can predict the relative percentage of metabolites. 相似文献
10.
D. Le Elizabeth Eric R. Powers Jian-Ping Bin Howard Leong-Poi N. Craig Goodman Sanjiv Kaul 《Journal of nuclear cardiology》2007,14(2):207-214
Background The mechanism by which transmyocardial revascularization (TMR) offers clinical benefit is controversial. We hypothesized that
TMR ameliorates ischemia by reversing paradoxical catecholamine-induced vasoconstriction.
Methods and Results Chronic ischemic cardiomyopathy was created in 11 dogs by placing ameroid constrictors on the proximal coronary arteries and
their major branches. Six weeks later, 35 channels were created percutaneously in the left circumflex artery region, with
the left anterior descending artery region serving as control. At rest, wall thickening and myocardial blood flow did not
change in the treated region, whereas they deteriorated in the control bed. Contractile and myocardial blood flow reserve
increased in the treated region but deteriorated in the control region. There was diminished iodine 123 metaiodobenzylguanidine
uptake and a significant reduction in noradrenergic nerves in the treated region compared with the control region, with a
corresponding reduction in tissue tyrosine hydroxylase activity.
Conclusions We conclude that the absence of a catecholamine-induced reduction in MBF reserve and contractile reserve in the TMR-treated
region with associated evidence of neuronal injury indicates that the relief of exercise-induced ischemia after TMR most likely
results from reversal of paradoxical catecholamine-induced vasoconstriction. These findings may have implications in selecting
patients who would benefit from TMR.
Supported in part by grants from the National Institutes of Health (R01-HL66034 and K-08-HL074290-01). Bethesda. Md. The radio-labeled
microspheres were provided by DuPont Pharmaceuticals, North Billerica. Mass, and the ultrasound equipment was supplied by
Philips. Andover, Mass. Dr Leong-Poi was the recipient of a Fellowship Training Grant from the Canadian Institute of Health
Research and the Heart and Stroke Foundation of Canada. 相似文献