全文获取类型
收费全文 | 25693篇 |
免费 | 1541篇 |
国内免费 | 421篇 |
专业分类
耳鼻咽喉 | 254篇 |
儿科学 | 599篇 |
妇产科学 | 406篇 |
基础医学 | 3412篇 |
口腔科学 | 933篇 |
临床医学 | 2212篇 |
内科学 | 5896篇 |
皮肤病学 | 437篇 |
神经病学 | 2005篇 |
特种医学 | 759篇 |
外国民族医学 | 1篇 |
外科学 | 3515篇 |
综合类 | 1093篇 |
一般理论 | 5篇 |
预防医学 | 1634篇 |
眼科学 | 440篇 |
药学 | 1936篇 |
6篇 | |
中国医学 | 353篇 |
肿瘤学 | 1759篇 |
出版年
2023年 | 183篇 |
2022年 | 464篇 |
2021年 | 812篇 |
2020年 | 550篇 |
2019年 | 638篇 |
2018年 | 731篇 |
2017年 | 589篇 |
2016年 | 658篇 |
2015年 | 837篇 |
2014年 | 1004篇 |
2013年 | 1270篇 |
2012年 | 1908篇 |
2011年 | 1940篇 |
2010年 | 1196篇 |
2009年 | 1009篇 |
2008年 | 1550篇 |
2007年 | 1574篇 |
2006年 | 1495篇 |
2005年 | 1388篇 |
2004年 | 1376篇 |
2003年 | 1285篇 |
2002年 | 1214篇 |
2001年 | 603篇 |
2000年 | 459篇 |
1999年 | 347篇 |
1998年 | 207篇 |
1997年 | 193篇 |
1996年 | 165篇 |
1995年 | 132篇 |
1994年 | 125篇 |
1993年 | 104篇 |
1992年 | 155篇 |
1991年 | 148篇 |
1990年 | 134篇 |
1989年 | 107篇 |
1988年 | 107篇 |
1987年 | 87篇 |
1986年 | 75篇 |
1985年 | 86篇 |
1984年 | 72篇 |
1983年 | 61篇 |
1982年 | 46篇 |
1981年 | 34篇 |
1979年 | 42篇 |
1978年 | 33篇 |
1975年 | 41篇 |
1974年 | 47篇 |
1973年 | 33篇 |
1971年 | 31篇 |
1969年 | 34篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
2.
Adilson Cunha Ferreira Edward Araujo Júnior Wellington P. Martins João Francisco Jordão Antônio Hélio Oliani Simon E. Meagher 《The journal of maternal-fetal & neonatal medicine》2015,28(14):1706-1710
Objective: To assess the quality of images and video clips of fetal central nervous (CNS) structures obtained by ultrasound and transmitted via tele-ultrasound from Brazil to Australia.Methods: In this cross-sectional study, 15 normal singleton pregnant women between 20 and 26 weeks were selected. Fetal CNS structures were obtained by images and video clips. The exams were transmitted in real-time using a broadband internet and an inexpensive video streaming device. Four blinded examiners evaluated the quality of the exams using the Likert scale. We calculated the mean, standard deviation, mean difference, and p values were obtained from paired t tests.Results: The quality of the original video clips was slightly better than that observed by the transmitted video clips; mean difference considering all observers = 0.23 points. In 47/60 comparisons (78.3%; 95% CI?=?66.4–86.9%) the quality of the video clips were judged to be the same. In 182/240 still images (75.8%; 95% CI?=?70.0–80.8%) the scores of transmitted image were considered the same as the original.Conclusion: We demonstrated that long distance tele-ultrasound transmission of fetal CNS structures using an inexpensive video streaming device provided images of subjective good quality. 相似文献
3.
Gabi Mueller Claudio Perret Christina M Spengler 《Journal of rehabilitation medicine》2006,38(6):381-386
OBJECTIVE: Respiratory muscle endurance of able-bodied persons, assessed by normocapnic hyperpnoea at 70% of their maximal voluntary ventilation, usually ranges from 10 to 20 minutes. The aim of this study was to determine the level of ventilation that patients with paraplegia and tetraplegia can sustain for 10-20 minutes to later be used as the guideline for respiratory muscle endurance training. DESIGN: Pilot study; cross-over setting. SUBJECTS: Two groups, 8 patients with paraplegia and 6 with tetraplegia. METHODS: Respiratory muscle endurance tests were performed at 3 different intensities of normocapnic hyperpnoea, i.e. 20%, 40% and 60% maximal voluntary ventilation. Subjects performed partial re-breathing from a bag to assure normocapnia. Respiratory endurance was separately analysed for patients with paraplegia and tetraplegia. RESULTS: Mean respiratory endurance times were 46.0, 18.9 and 4.2 minutes at 20%, 40% and 60% maximal voluntary ventilation in patients with tetraplegia and 51.8, 38.8 and 12.2 minutes in patients with paraplegia. The duration differed significantly at 60% maximal voluntary ventilation between the groups. CONCLUSION: Minute ventilation to perform respiratory muscle endurance training can be set at around 40% of maximal voluntary ventilation for patients with tetraplegia and around 60% of maximal voluntary ventilation for patients with paraplegia, as these levels can be sustained for 10-20 minutes. 相似文献
4.
5.
6.
A M Cesura M D Galva R Imhof E Kyburz G B Picotti M Da Prada 《European journal of pharmacology》1989,162(3):457-465
This study demonstrated the existence of specific binding sites for [3H]Ro 19-6327 in human platelet membranes. This compound is a novel, time-dependent inhibitor of monoamine oxidase type B (MAO-B) and is structurally closely related to [3H]Ro 16-6491. The density of the sites labelled with high affinity by [3H]Ro 19-6327 was similar to that observed in previous studies with [3H]Ro 16-6491 as ligand. Binding was reversible at 20 degrees C and showed a relatively slow dissociation (t1/2 = 220 min). The dissociation rate was markedly decreased (t1/2 = greater than 24h) at 0 degrees C. MAO-B, but not MAO-A inhibitors, effectively prevented the binding of [3H]Ro 19-6327. Like [3H]Ro 16-6491, [3H]Ro 19-6327 is recognized as a substrate by MAO-B, being eventually deaminated by the enzyme. Since the deaminated aldehyde derivative of Ro 19-6327 did not inhibit MAO-B, a still unidentified reversible adduct, formed at the MAO-B active site, might explain the high potency and selectivity of [3H]Ro 19-6327. Incubation of the radioligand-enzyme complex from platelet and brain membranes with NaBH3CN and acetic acid (to pH 4.5) caused the irreversible incorporation of the radioactivity into a single polypeptide as shown by SDS-PAGE analysis. This polypeptide had a molecular weight identical to that of the MAO-B subunit, i.e. 58,000. The presence of unlabelled MAO-B inhibitors in the incubation mixture prevented the covalent incorporation of [3H]Ro 19-6327. The irreversible MAO-B inhibitor, [3H] pargyline, labelled a protein with a molecular weight identical to the protein labelled by [3H]Ro 19-6327.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
7.
A C Da Rosa B Kemp T Paiva F H Lopes da Silva H A Kamphuisen 《Electroencephalography and clinical neurophysiology》1991,78(1):71-79
A model of sleep phasic events such as vertex waves, K complexes, delta waves and sleep spindles is proposed. It consists of feedback loops that are driven by white noise (simulating tonic delta and sigma activity) and by isolated random impulses, simulating vertex waves or K complexes, depending on the background tonic activity. A model-based method for the detection of sleep phasic events was implemented in a personal computer. Its performance was investigated using simulated and real whole-night EEG signals. The method was able to detect K complexes and vertex waves in a reliable way in spite of their variable shapes and in the presence of a variety of background activities. The detector appears to have superior performance to those so far reported in the literature. The performance of the detector was also compared to that of an electroencephalographer using normal sleep EEG records of 8 h duration from 6 subjects. The performance was satisfactory both in terms of accuracy and reliability. The problem of detecting K complexes in stages 3 and 4 of sleep is discussed. 相似文献
8.
9.
10.
Unusual central chorioretinitis as the first manifestation of early secondary syphilis 总被引:1,自引:0,他引:1
E C de Souza A E Jalkh C L Trempe S Cunha C L Schepens 《American journal of ophthalmology》1988,105(3):271-276
Three young, otherwise healthy patients had a similar picture of unilateral central chorioretinitis associated with severe visual loss. Fluorescein angiography disclosed diffuse leakage under the neurosensory retina in the posterior pole, associated with multifocal areas of staining along the retinal vessels. Systemic examination showed a positive fluorescent treponemal antibody absorption test and a sharp increase in VDRL titers, indicative of active secondary syphilis. The patients responded dramatically to penicillin treatment, with visual recovery and resolution of the fundus lesions. 相似文献