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   745696篇
  免费   49012篇
  国内免费   1411篇
耳鼻咽喉   9879篇
儿科学   24302篇
妇产科学   18552篇
基础医学   112598篇
口腔科学   22668篇
临床医学   69616篇
内科学   141746篇
皮肤病学   16789篇
神经病学   52745篇
特种医学   26960篇
外国民族医学   76篇
外科学   109274篇
综合类   15039篇
现状与发展   14篇
一般理论   180篇
预防医学   55472篇
眼科学   16890篇
药学   55009篇
  13篇
中国医学   2402篇
肿瘤学   45895篇
  2021年   6508篇
  2019年   6404篇
  2018年   9471篇
  2017年   7592篇
  2016年   8497篇
  2015年   9342篇
  2014年   12546篇
  2013年   18270篇
  2012年   22194篇
  2011年   23131篇
  2010年   14510篇
  2009年   14221篇
  2008年   21468篇
  2007年   22793篇
  2006年   23241篇
  2005年   21580篇
  2004年   20987篇
  2003年   19863篇
  2002年   19324篇
  2001年   36810篇
  2000年   37240篇
  1999年   30852篇
  1998年   8502篇
  1997年   7237篇
  1996年   7568篇
  1995年   7081篇
  1994年   6453篇
  1993年   5913篇
  1992年   23200篇
  1991年   23144篇
  1990年   22495篇
  1989年   22264篇
  1988年   20203篇
  1987年   19571篇
  1986年   18621篇
  1985年   17434篇
  1984年   12821篇
  1983年   10875篇
  1982年   6053篇
  1979年   11577篇
  1978年   8176篇
  1977年   6894篇
  1976年   6651篇
  1975年   7320篇
  1974年   8544篇
  1973年   8176篇
  1972年   7687篇
  1971年   7145篇
  1970年   6897篇
  1969年   6323篇
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
991.
992.
This study determined inter- and intra-observer reliability for measurement of the angles of Böhler and Gissane, for the decision between surgical or conservative management and for the three mostly used classification systems for calcaneal fractures with the use of 2D-CT imaging versus 2D- and 3D-CT imaging.  相似文献   
993.
The Modified Checklist for Autism in Toddlers (M-CHAT) and the Early Screening of Autistic Traits (ESAT) were designed to screen for autism spectrum disorders in very young children. The aim of this study was to explore proportions of children that screened positive on the ESAT or the M-CHAT and to investigate if screening positive on the ESAT and M-CHAT is associated with clinical referral by 18 months and other aspects of children’s development, health, and behavior. In this study, the mothers of 12,948 18-month-old children returned a questionnaire consisting of items from the ESAT and M-CHAT, plus questions about clinical and developmental characteristics. The M-CHAT identified more screen-positive children than the ESAT, but the ESAT was associated with more clinical referrals and tended to identify more children with medical, language, and behavioral problems. A post hoc analysis of combining the two instruments found this to be more effective than the individual instruments alone in identifying children referred to clinical services at 18 months. Further analysis at the level of single items is warranted to improve these screening instruments.  相似文献   
994.
995.
996.
997.
The cellular prion protein, encoded by Prnp gene, is involved in neuroprotection, neuroplasticity and neurodevelopment. The variant allele Valine at codon 129 of the Prnp was associated with decreased brain volume in healthy volunteers and schizophrenic patients. We investigate the association between the cerebellum volume and the presence of variant allele Valine at codon 129 of the Prnp gene in patients with mesial temporal lobe epilepsy related to hippocampal sclerosis (MTLE-HS). The Prnp coding sequence was determined in 41 refractory MTLE-HS patients. The cerebellum volume corrected by the intracranial volume of patients with the normal Prnp genotypes was compared with that of patients presenting the variant alleles at codon 129. Twenty patients showed the Met129Met genotype, 16 showed Met129Val, and 5 had Val129Val. There were no association among clinical, demographic, electrophysiological, antiepileptic drugs used, and the presence of the Prnp variant alleles. The presence of Prnp variant allele at codon 129 was not associated with the analyzed cerebellum volume. Prnp variant alleles at codon 129 are not associated with cerebellum volume in patients with refractory MTLE-HS.  相似文献   
998.
Epileptic encephalopathies (EE) belong to the group of epilepsies which are associated with expressed cognitive and behavioral disturbances subsequent to epileptic activity. Despite the great importance of EE in the development and psychosocial adaptation of affected children, the mechanisms of cognitive deficits in EE have so far been insufficiently investigated. This review article summarizes the various neuroimaging studies which have tried to describe specific neuronal networks in EE. The results show that although epileptic activity in EE can be generated in different brain regions, specific propagation pathways and networks exist which are very characteristic for each different form of encephalopathy. In some forms of EE the epileptic activity seems to impair the integrity of the default mode network and possibly to interfere with cognitive function through this mechanism. Furthermore, there are further mechanisms underlying EE, e.g. abnormal connectivity patterns between brain regions which participate in the control of cognitive functions and impairment of the connections and activities in the thalamocortical network.  相似文献   
999.

Background

Sporadic influenza A virus (IAV) outbreaks in humans and swine have resulted from commingling of large numbers of people and pigs at agricultural fairs in the United States. Current antemortem IAV surveillance strategies in swine require collecting nasal swabs, which entails restraining pigs with snares. Restraint is labor-intensive for samplers, stressful for pigs, and displeasing to onlookers because pigs often resist and vocalize.

Objective

To evaluate the utility of snout wipes in exhibition swine as a method to make IAV surveillance efforts less intrusive, less labor-intensive, and more widely accepted among pig owners and exhibition officials.

Methods

Three materials (rayon/polyester gauze, cotton gauze, and Swiffer® Sweeper dry cloths) were inoculated with IAV, and viral recoveries from these materials were quantified using qRT-PCR and TCID50 assays. In a field trial, paired cotton gauze snout wipes and gold standard polyester-tipped nasal swabs were collected from 553 pigs representing 29 agricultural fairs and the qualitative results of rRT-PCR and viral isolation were compared.

Results and Conclusions

Viral recoveries from potential snout wipe materials ranged from 0·26 to 1·59 log10 TCID50/ml less than that of the positive control in which no substrate was included; rayon/polyester gauze performed significantly worse than the other materials. In the field, snout wipes and nasal swabs had high levels of agreement for both rRT-PCR detection and virus isolation. Although further investigation and refinement of the sampling method is needed, results indicate that snout wipes will facilitate convenient and undisruptive IAV surveillance in pigs at agricultural fairs.  相似文献   
1000.
Coronary spasm during coronary angiography for vasculopathy in children can be prevented by the intracoronary administration of nitroglycerin. We reviewed the anesthesia and catheterization reports and charts for pediatric transplant recipients who underwent angiography from 2005 through 2010. Correlation analysis was used to study the relation of post-injection systolic blood pressure (SBP) to nitroglycerin dose. Forty-one angiographic evaluations were performed on 25 patients (13 male and 12 female). Mean age was 9.9 ± 3.2 years (range, 3.3–16.1 yr). The mean total dose of nitroglycerin was 2.93 ± 1.60 µg/kg (range, 1–8 µg/kg).There was a significant drop between the baseline SBP (mean, 106 ± 21.6 mmHg) and the lowest mean SBP before nitroglycerin administration (78 ± 13.2, P <0.0001, paired t test). There was no significant additional change in SBP (mean after nitroglycerin administration, 80.7 ± 13.1 mmHg; P = 0.2). There was a significant drop in lowest heart rate between baseline (109 ± 16.5 beats/min) and before nitroglycerin administration (89 ± 14.3 beats/min; P <0.0001, paired t test). There was no significant additional change in heart rate (mean heart rate after nitroglycerin, 84 ± 17.7 beats/min; P = 0.09). There were 2 interventions for SBP before nitroglycerin and 2 after nitroglycerin. One child experienced a transient ST-T–segment change during angiography after nitroglycerin. In the highest dose range, the additional decrease in SBP was 7.2 mmHg (P=0.03). Routine intracoronary nitroglycerin administration in this dose range produced no significant changes in SBP or heart rate in children.Key words: Child, coronary angiography, coronary vasospasm/etiology, dose-response relationship, drug, heart transplantation/adverse effects, hemodynamics/drug effects, nitroglycerin/administration & dosage/therapeutic use, postoperative complications/therapy, retrospective studies, vasodilation/drug effectsAllograft coronary disease in children occurs with increasing frequency after transplantation, as a function of time. In a multicenter study,1 the incidence of coronary artery disease in children 5 years post-transplant was 17% of all recipients. Coronary angiography remains the gold standard in the detection of vasculopathy in heart-transplant recipients.2 Coronary artery spasm can complicate selective coronary angiography and result in myocardial ischemia. Coronary spasm can simulate the angiographic appearance of graft vasculopathy and cause diagnostic confusion.3 The spasm can arise from manipulation of the arterial wall by the catheter or from intraluminal injection of contrast material. In cardiac transplant recipients, coronary artery spasm has been reported in as many as 4.9% of coronary angiograms.3In adults, intracoronary nitroglycerin is routinely administered during coronary angiography to prevent coronary artery spasm.4 In children, however, safety and dosage guidelines for intracoronary nitroglycerin have not yet been firmly established. A dose of 3 µg/kg can be extrapolated by weight from the established adult dose of 200 µg; this dose was used in a study of children after the arterial switch operation and was shown to produce coronary vasodilation—with a small reduction in systolic blood pressure (SBP) and no noteworthy change in heart rate—in a control group of patients.5,6We previously reported a case of coronary artery spasm during routine coronary angiographic monitoring in a 9-year-old boy who had undergone heart transplantation as an infant.7 After left main coronary artery injection of contrast material, the patient''s left anterior descending and left circumflex coronary arteries appeared to be diffusely narrow, and he developed marked ST-segment elevation, hypotension, and ventricular tachycardia. After cardiopulmonary resuscitation, he recovered uneventfully and displayed normal systolic function. Coronary angiography one month later, with the administration of intracoronary nitroglycerin before the injection of contrast material, revealed normal coronary artery diameter and was accomplished without complication.Since 2005, intracoronary nitroglycerin has routinely been used in pediatric transplant patients during biennial selective coronary angiographic monitoring at our institution. The purpose of the study is to report our experience with the routine use of intracoronary nitroglycerin for coronary angiography in children: its effects on blood pressure, on heart rate, and on the occurrence of arrhythmia and ST-segment elevation.  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