全文获取类型
收费全文 | 114047篇 |
免费 | 10525篇 |
国内免费 | 275篇 |
学科分类
医药卫生 | 124847篇 |
出版年
2021年 | 1518篇 |
2020年 | 1005篇 |
2019年 | 1553篇 |
2018年 | 1929篇 |
2017年 | 1438篇 |
2016年 | 1577篇 |
2015年 | 1787篇 |
2014年 | 2388篇 |
2013年 | 3828篇 |
2012年 | 5407篇 |
2011年 | 5882篇 |
2010年 | 3140篇 |
2009年 | 3017篇 |
2008年 | 5240篇 |
2007年 | 5853篇 |
2006年 | 5620篇 |
2005年 | 5713篇 |
2004年 | 5379篇 |
2003年 | 5146篇 |
2002年 | 4957篇 |
2001年 | 2975篇 |
2000年 | 3047篇 |
1999年 | 2788篇 |
1998年 | 1530篇 |
1997年 | 1287篇 |
1996年 | 1181篇 |
1995年 | 1115篇 |
1994年 | 1127篇 |
1993年 | 1045篇 |
1992年 | 2316篇 |
1991年 | 2216篇 |
1990年 | 2077篇 |
1989年 | 2012篇 |
1988年 | 1930篇 |
1987年 | 1926篇 |
1986年 | 1869篇 |
1985年 | 1835篇 |
1984年 | 1687篇 |
1983年 | 1518篇 |
1982年 | 1172篇 |
1981年 | 1014篇 |
1980年 | 946篇 |
1979年 | 1368篇 |
1978年 | 1053篇 |
1977年 | 943篇 |
1976年 | 829篇 |
1975年 | 836篇 |
1974年 | 973篇 |
1973年 | 836篇 |
1972年 | 798篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
Gary E. Stapleton Benjamin W. Eidem Ricardo H. Pignatelli Karina M. Carlson Charles E. Mullins Ronald G. Grifka 《Congenital heart disease》2006,1(3):116-119
Background. A persistent patent ductus arteriosus (PDA) may delay closure of a coexisting atrial septal defect (ASD) due to volume loading and enlargement of the left atrium. The purpose of this study was to investigate the natural history of ASD size in patients with a PDA following transcatheter PDA occlusion. Methods. All patients with an ASD and a PDA who underwent transcatheter PDA occlusion at Texas Children’s Hospital were identified. Patients with ASD diameter <3 mm, or additional cardiac defects were excluded. Eight patients (7 females) with small‐ to moderate‐sized ASDs and a PDA were identified. Patient demographics, echocardiographic data, and cardiac catheterization data were recorded. Data were analyzed by 1‐tailed t‐test. Results. Following PDA occlusion, ASD diameter decreased in 6 of 8 patients by a mean of 3.8 mm (±2.3 mm), including 2 that closed. The median duration of follow‐up was 689 days. One ASD remained unchanged and 1 increased in size. The mean maximum ASD diameter decreased from 6.4 mm (±2.2 mm) to 3.9 mm (±3.4 mm) (P = .03). Two patients underwent subsequent transcatheter ASD occlusion. Conclusion. Following transcatheter PDA occlusion, small‐ to moderate‐sized ASDs have significant probability to decrease in size, and possibly close. In infants and children, we recommend transcatheter PDA occlusion, and serial follow‐up of the size of the ASD. This will allow many small‐ to moderate‐sized ASDs to either close, or become smaller, obviating the need for future intervention. 相似文献
32.
33.
34.
Petra Schwingenschuh Karoline Wenzel Petra Katschnig Ronald Saurugg Erwin Ott 《Movement disorders》2007,22(5):742-745
We describe a case of a palatal tic resembling palatal tremor (PT) in a young female patient with a previously unrecognized mild Tourette syndrome. At the time of her visit, the patient complained about ear clicks that were audible to others. We discuss the differential diagnoses of hyperkinetic palatal movements emphasizing the ongoing discussion about essential PT representing a more heterogeneous disorder than previously thought. 相似文献
35.
Pretibial lacerations and lower limb wounds are referred to plastic surgery teams for split skin graft surgery. Traditionally, these patients have been immobilised on bedrest following surgery. More recently, patients have commenced ambulation earlier to avoid medical complications and facilitate discharge. The objective of this literature review was to determine when such patients should begin walking. A literature search was undertaken using the electronic databases AMED, Cinahl, Embase, Medline (via Ovid), PEDro and Pubmed. Clinical trials using human subjects, written in English, were included. Seventeen (of 1137) papers met the inclusion criteria and were reviewed. The literature suggested that patients should begin walking immediately or at the earliest possible opportunity after lower limb skin graft surgery. Although the literature advocated early ambulation, the evidence base presented with a number of recurrent methodological limitations, including small sample sizes, lack of a control sample, and limited follow-up. Accordingly, further research employing large, well-designed, randomised controlled trials is recommended. It will then be possible to understand with greater certainty when patients should begin walking after lower extremity split skin graft surgery. 相似文献
36.
37.
Stacey A Thom Jeannette D Hoit Thomas J Hixon Alice E Smith 《The Cleft palate-craniofacial journal》2006,43(5):539-546
OBJECTIVE: To determine the age at which infants achieve velopharyngeal closure during vocalization. DESIGN: Longitudinal with repeated measures. SETTING: Laboratory. PARTICIPANTS: Six healthy infants were studied monthly from ages 2 to 6 months while they interacted with a parent and an investigator. MAIN OUTCOME MEASURES: The presence or absence of velopharyngeal closure, as determined by sensing ram pressure at the anterior nares. RESULTS: The velopharynx was open for windups, whimpers, and laughs, and it was closed for cries, screams, and raspberries, regardless of age. The frequency with which the velopharynx closed during syllable utterances increased significantly with age. CONCLUSIONS: Velopharyngeal closure for speech-like utterance increases with age, but is not complete and is still undergoing development at 6 months of age. Velopharyngeal closure during infancy may be influenced by pressure demands of the utterance; however, support for this speculation is stronger for other types of utterances than it is for speech-like utterances. The method used in this study holds promise for evaluating infants with suspected velopharyngeal impairment. 相似文献
38.
H. Newell J. D. Smith P. Rogers E. Birks A. J. Danskine R. E. Fawson M. L. Rose 《American journal of transplantation》2006,6(7):1712-1717
Implantation of left ventricular assist devices (LVAD) is associated with HLA antibody sensitization. The objective of this study was to determine the specificity of antibodies produced by LVAD recipients using a combination of ELISA, Luminex and microcytotoxicity assays. Fifty-one LVAD patients were studied, from 44 to 838 days post-implantation. No patient developed HLA antibodies, although 24 produced IgG antibodies detectable in both ELISA and Luminex assays. These antibodies manifest as positive reactions with class I and class II wells of the ELISA and also blank wells. In Luminex assays, they produce high MFI readings with the negative control beads. Antibodies were detected 18 to 228 days after implantation. This reactivity was found to be directed against bovine serum albumin (BSA), commonly used to block non-specific binding in ELISA and Luminex assays; absorption of sera with BSA-coated beads completely abrogated reactivity in all solid phase assays, but did not eliminate anti-HLA antibodies in control sera. Ten of the 24 patients have proceeded to transplantation, with a 1-year graft survival of 69%. In conclusion, it appears that implantation of LVADS disrupts immunoregulatory pathways leading to production of anti-albumin antibodies. These can be misinterpreted as anti-HLA antibodies in solid phase assays. 相似文献
39.
40.
Erika E Forbes Douglas E Williamson Neal D Ryan Boris Birmaher David A Axelson Ronald E Dahl 《Neuropsychopharmacology》2006,59(1):24-30
BACKGROUND: Changes in the hypothalamic-pituitary-adrenal (HPA) axis, as evidenced by patterns of cortisol secretion, have been of interest in understanding depression and anxiety disorders across the life span. Previous studies of pediatric depression have pointed to the period around sleep onset as a key time point for observing alterations in cortisol secretion associated with affective disorders. Evidence also indicates that pubertal development may influence the expression of HPA dysregulation. We hypothesized that adolescents with depression and youth with anxiety disorders exhibit elevated peri-sleep-onset cortisol. METHODS: Plasma cortisol was sampled every 20 min around sleep onset from children and adolescents with major depressive disorder (n = 116), anxiety disorders (n = 32), or no history of psychiatric disorder (control; n = 76). Sleep onset was determined by polysomnography. Classification of participants as children or adolescents was based on Tanner staging of pubertal maturation. RESULTS: Children with anxiety disorders had higher peri-sleep-onset cortisol than children with depression or control children. Adolescents with depression had marginally higher peri-sleep-onset cortisol than control adolescents and significantly higher peri-sleep-onset cortisol than children with depression. CONCLUSIONS: Depression and anxiety are associated with altered cortisol secretion around sleep onset, and these changes appear to be influenced by pubertal maturation. 相似文献