首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   2360篇
  免费   130篇
  国内免费   5篇
耳鼻咽喉   15篇
儿科学   108篇
妇产科学   292篇
基础医学   256篇
口腔科学   217篇
临床医学   161篇
内科学   324篇
皮肤病学   46篇
神经病学   113篇
特种医学   158篇
外科学   390篇
综合类   54篇
一般理论   2篇
预防医学   135篇
眼科学   19篇
药学   120篇
中国医学   1篇
肿瘤学   84篇
  2023年   20篇
  2021年   48篇
  2020年   21篇
  2019年   46篇
  2018年   49篇
  2017年   32篇
  2016年   29篇
  2015年   44篇
  2014年   63篇
  2013年   89篇
  2012年   114篇
  2011年   116篇
  2010年   93篇
  2009年   61篇
  2008年   102篇
  2007年   120篇
  2006年   109篇
  2005年   83篇
  2004年   92篇
  2003年   76篇
  2002年   80篇
  2001年   58篇
  2000年   54篇
  1999年   59篇
  1998年   30篇
  1997年   35篇
  1996年   31篇
  1995年   31篇
  1994年   25篇
  1993年   27篇
  1992年   40篇
  1991年   43篇
  1990年   39篇
  1989年   45篇
  1988年   42篇
  1987年   40篇
  1986年   33篇
  1985年   36篇
  1984年   26篇
  1983年   27篇
  1982年   21篇
  1981年   24篇
  1980年   21篇
  1979年   30篇
  1977年   16篇
  1976年   13篇
  1973年   17篇
  1972年   13篇
  1970年   12篇
  1969年   13篇
排序方式: 共有2495条查询结果,搜索用时 15 毫秒
41.
Objective To evaluate gestation-specific risks of stillbirth, neonatal and post-neonatal mortality.
Design Retrospective analysis of 171,527 notified births (1989–1991) and subsequent infant survival at one year, from community child health records.
Setting Notifications from maternity units in the North East Thames Region, London.
Main outcome measures The incidence of births, stillbirths, neonatal and post-neonatal deaths at each gestation after 28 completed weeks. Mortality rates per 1000 total or live births and per 1000 ongoing pregnancies at each gestation were calculated.
Results The rates of stillbirth at term (2.3 per 1000 total births) and post-term (1.9 per 1000 total births) were similar. When calculated per 1000 ongoing pregnancies, the rate of stillbirth increased six-fold from 0.35 per 1000 ongoing pregnancies at 37 weeks to 2.12 per 1000 ongoing pregnancies at 43 weeks of gestation. Neonatal and post-neonatal mortality rates fell significantly with advancing gestation, from 15 1.4 and 31.7 per 1000 live births at 28 weeks, to reach a nadir at 41 weeks of gestation (0.7 and 1.3 per 1000 live births, respectively), increasing thereafter in prolonged gestation to 1.6 and 2.1 per 1000 live births at 43 weeks of gestation. When calculated per 1000 ongoing pregnancies, the overall risk of pregnancy loss (stillbirth + infant mortality) increased eight-fold from 0.7 per 1000 ongoing pregnancies at 37 weeks to 5.8 per 1000 ongoing pregnancies at 43 weeks of gestation.
Conclusion The risks of prolonged gestation on pregnancy are better reflected by calculating fetal and infant losses per 1000 ongoing pregnancies. There is a significant increase in the risk of stillbirth, neonatal and post-neonatal mortality in prolonged pregnancy. This study provides accurate data on gestation-specific risks of pregnancy loss, enabling pregnant women and their carers to judge the appropriateness of obstetric intervention.  相似文献   
42.
Objective To assess the risk of maternal osteoporosis associated with antenatal corticosterioid administration for neonatal respiratory distress syndrome prophylaxis.
Design Prospective longitudinal study.
Setting Maternity unit of Chelsea and Westminster Hospital, London.
Population Fourteen pregnant women who received dexamethasone therapy for fetal lung maturation in anticipation of delivery before 34 completed weeks of gestation.
Methods Blood samples were collected before dexamethasone administration, 24 hours and 48 hours after the course of dexamethasone, and within 24 hours of delivery. Serum levels of carboxy terminal pro-peptide of type I pro-collagen (PICP) were measured to monitor the rate of bone formation, and serum levels of cross-linked carboxy terminal telopeptide (ICTP) were measured as a marker of bone resorption.
Main outcome measures Changes in the markers of bone turnover following dexamethasone administration.
Results Serum PICP levels dropped 24 hours after dexamethasone therapy (   P = 0.001  ), but partially recovered by 48 hours (   P = 0.014  ) to reach higher than pre-therapy levels at delivery (   P = 0.044  ). Although there were no corresponding changes in the serum levels of ICTP after 24 and 48 hours of therapy, levels increased from pretherapy to delivery (   P = 0.006  ).
Conclusion Antenatal corticosteroid therapy leads to a transient suppression of, followed by an increase in, bone formation without any significant alteration in the pattern of bone resorption expected during pregnancy.  相似文献   
43.
Moyamoya disease and spontaneous internal carotid artery dissections are rare conditions, but both tend to affect young adults with potentially devastating consequences. A 43-year-old non-Japanese patient presented with neurological symptoms, which, following carotid Doppler ultrasound and angiography, was labelled as being due to a spontaneous internal carotid artery dissection. Repeat imaging at 3 months showed normalisation of the carotid Doppler findings which coincided with the formation of „moyamoya” vessels on the angiogram. This case report illustrates the changes on carotid ultrasound in early moyamoya disease which may mimic the appearances of an internal carotid artery dissection and demonstrates the change of the spectral Doppler waveform that occurs with the formation of new vessels at the base of the brain. Received: 20 August 1998; Revision received: 23 November 1998; Accepted: 23 December 1998  相似文献   
44.
Reflex sympathetic dystrophy, also known as complex regional pain syndrome (CRPS), has recently been shown to be associated with autoantibodies against β2‐adrenergic and muscarinic M2 receptors. In addition to pain and sudomotor/vasomotor symptoms, dysautonomia is also observed in a subset of CRPS patients. Despite its severity, there are few effective therapies for CRPS described to date. We report a case of a 14‐year‐old girl with CRPS of her right leg and dysautonomia (gastroparesis, postural tachycardia) refractory to multiple therapies, successfully treated with therapeutic plasma exchange (TPE) with albumin replacement. The patient, who has serum anti β2‐adrenergic and muscarinic M2 receptor autoantibodies in addition to nicotinic acetylcholine receptor ganglionic autoantibodies, underwent an initial course of five TPEs over a 2‐week period. She demonstrated a clinical response to TPE as manifested by a rapid improvement in her fatigue and gastroparesis, with a gradual yet significant improvement in her leg pain and sudomotor/vasomotor flares. Following the loading procedures, the patient was treated with rituximab. She continues to require periodic TPE to maintain a remission, with additional immunosuppression being considered long term. Although further studies are needed, TPE (in combination with immunosuppression) may be an appropriate therapy for CRPS patients with detectable autoantibodies, as it is for better characterized diseases with autoantibodies against neuronal surface receptors such as myasthenia gravis or Lambert Eaton myasthenic syndrome. J. Clin. Apheresis 31:368–374, 2016. © 2015 Wiley Periodicals, Inc.  相似文献   
45.
46.
47.
Clinical Oral Investigations - This study compared the effects of oral hygiene with a toothpaste formulated with zinc (test) to a fluoride dentifrice (control) for effects on oral polymorphonuclear...  相似文献   
48.
49.
Human α-synuclein (α-Syn) is instrumental in maintaining homeostasis of monoamine neurotransmitters in brain, through its trafficking, and regulation of the cell surface expression and, thereby, activity of dopamine, serotonin and norepinephrine transporters. Here we have investigated whether other members of the synuclein family of proteins, γ-synuclein (γ-Syn) and β-synuclein (β-Syn) can similarly modulate the serotonin transporter (SERT). In Ltk cells co-transfected with SERT and γ-Syn, γ-Syn reduced [3H]5-HT uptake, in a manner dependent on its expression levels. The decrease in SERT activity was via decreased Vmax of the transporter, without change in Km, compared to cells expressing only SERT. By contrast, β-Syn co-expression failed to alter SERT uptake activity, and neither the Vmax nor the Km was changed in the presence of β-Syn. γ-Syn modulation of SERT was only partial, with a maximal ∼27% decrease in SERT activity seen even at high expression levels of γ-Syn. By contrast, α-Syn attenuated SERT activity by ∼65% at identical expression levels as γ-Syn. Co-immunoprecipitation studies showed the presence of heteromeric protein:protein complexes between γ-Syn or α-Syn and SERT, while β-Syn failed to physically interact with SERT. Both α-Syn and γ-Syn colocalized with SERT in rat primary raphae nuclei neurons. These studies document a novel physiological role for γ-Syn in regulating 5-HT synaptic availability and homeostasis, and may be of relevance in depression and mood disorders, where SERT function is dysregulated.  相似文献   
50.
Background: The purpose of the present study was to compare iissue harmonic imaging (THI) and conventional sonography in focal hepatic lesions. Methods: Fifty patients with focal hepatic lesions were enrolled for study. Conventional grayscale and THI was performed in all the patients and two sets of images of the lesions were recorded (one each for THI and conventional) and assessed for fluid–solid differentiation, detail and overall image quality. These images were compared with conventional sonographic images and graded better, same or worse as per the case. Lesions were confirmed by fine‐needle aspiration cytology (FNAC)/surgery/other modalities such as computed tomography (CT) or magnetic resonance imaging (MRI). Results: Out of 50 patients with focal hepatic lesions, 21 patients had metastatic lesions (two single; 19 multiple) five patients had hepatocellular carcinoma (HCC), five patients had hydatid cysts, nine had simple hepatic cyst whereas five patients had liver abscess, three had focal fatty infiltration; and lymphoma and hemangioma were seen in one patient each. The first observer ranked THI better than standard sonography in 40 patients (80%) for fluid–solid differentiation, in 38 (76%) for detail and in 39 (78%) for overall image quality. The second observer ranked THI better than standard sonography in 39 patients (78%) for fluid–solid differentiation, in 40 (80%) for detail and in 42 (84%) for overall image quality. Tissue harmonic imaging provided additional information in eight patients (16%) and resulted in treatment alteration in three patients (6%). Conclusion: Tissue harmonic imaging was significantly better than conventional sonography for fluid–solid differentiation, detail and total image quality in focal hepatic lesions, especially in obese patients and patients with poor acoustic window.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号