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   5149篇
  免费   614篇
  国内免费   48篇
耳鼻咽喉   10篇
儿科学   209篇
妇产科学   241篇
基础医学   827篇
口腔科学   113篇
临床医学   496篇
内科学   920篇
皮肤病学   145篇
神经病学   487篇
特种医学   196篇
外科学   592篇
综合类   142篇
一般理论   5篇
预防医学   605篇
眼科学   141篇
药学   341篇
中国医学   24篇
肿瘤学   317篇
  2021年   63篇
  2019年   62篇
  2018年   78篇
  2017年   67篇
  2016年   73篇
  2015年   68篇
  2014年   98篇
  2013年   143篇
  2012年   199篇
  2011年   187篇
  2010年   143篇
  2009年   127篇
  2008年   191篇
  2007年   251篇
  2006年   237篇
  2005年   185篇
  2004年   187篇
  2003年   182篇
  2002年   203篇
  2001年   184篇
  2000年   185篇
  1999年   174篇
  1998年   90篇
  1997年   65篇
  1996年   70篇
  1995年   50篇
  1994年   60篇
  1993年   70篇
  1992年   131篇
  1991年   123篇
  1990年   125篇
  1989年   124篇
  1988年   108篇
  1987年   115篇
  1986年   113篇
  1985年   108篇
  1984年   94篇
  1983年   89篇
  1982年   59篇
  1981年   39篇
  1980年   59篇
  1979年   72篇
  1978年   56篇
  1977年   49篇
  1976年   52篇
  1975年   47篇
  1974年   53篇
  1973年   52篇
  1972年   47篇
  1967年   35篇
排序方式: 共有5811条查询结果,搜索用时 125 毫秒
81.
There is a deficit of literature regarding the association between nickel allergy–induced symptoms and implanted devices. This report describes a case of nickel allergy causing debilitating migraine-like symptoms, failing to resolve with medical therapy, requiring surgical removal of the device and repair of the defect.  相似文献   
82.
IntroductionFibroepithelial polyps (FEP) of the lower urinary tract are relatively common in adults but rare in children, with fewer than 250 cases reported in the literature to date.ObjectiveThe aim of this study was to address the experience of FEP management in children.Study designA retrospective multicenter review was undertaken in children with defined FEP of the lower urinary tract managed between 2008 and 2018. The data at 18 pediatric surgery centers were collected. Their demographic, radiological, surgical, and pathological information were reviewed.ResultsA total of 33 children (26 boys; 7 girls) were treated for FEP of the lower urinary tract at 13 centers. The most common presentation was urinary outflow as hematuria (41%), acute urinary retention (25%), dysuria (19%), or urinary infections (28%). A prenatal diagnosis was made for three patients with hydronephrosis. Almost all of the children (94%) underwent ultrasound imaging of the urinary tract as the first diagnostic examination, 23 (70%) of them also either had an MRI (15%), cystourethrography (25%), computerized tomography (6%), or cystoscopy (45%). Two of these children (6%) had a biopsy prior to the surgery. The median preoperative delay was 7.52 (range: 1–48) months. Most of the patients were treated endoscopically, although four (12.1%) had open surgery and two (6.1%) had an additional incision for specimen extraction. The median hospital stay was 1.5 (range: 1–10) days. There were no recurrences and no complications after a median follow-up of 13 (range: 1–34) months.DiscussionThe main limitation of our study is the retrospective design, although it is the largest one for this pathology.ConclusionThis series supports sonography as the most suitable diagnosis tool before endoscopy to confirm the diagnosis and to perform the resection for most FEP in children. This report confirms the recognized benign nature in the absence of recurrences.Level of EvidenceLevel V.  相似文献   
83.
A dynamic microbiological test has been used to assess the safety of sealed containers for use in laboratory centrifuges. When 26 models of containers (buckets or rotors) were examined 27% failed to contain aerosols. Some of the reasons for the failures are described.  相似文献   
84.
The effect of the infusion of different fat emulsions (Intralipid and MCT/LCT mixtures) on the reticuloendothelial function of the rabbit has been investigated. Emulsions containing 20% dispersed triglyceride were administered over 6 h to a total of 3 g/kg body weight. The extent of blockade of the reticuloendothelial system was measured using a labelled probe in the form of technetium-99m labelled albumin microspheres. Scintigraphic and blood and organ level determinations demonstrated that all emulsions caused an impairment of reticuloendoethlial function, but this was small.  相似文献   
85.
Although puréed diets are thought to be widely used for patients in long-term care facilities, there is little specific information concerning prevalence and reasons for the actual use of this diet texture. At Saint-Vincent Hospital, a 516 bed, long-term care and rehabilitation facility, 25.9% of the chronic-care population (n = 424) were on a puréed diet. Those who received puréed diets tended to be older (83.5 years versus 75.4 years, P < 0.001) and were more likely to be female (82.7% versus 70.8% P < 0.006), than the total population of long-term care patients. A greater percentage of patients receiving a puréed diet had dementia (43.0% versus 30.6%, P < 0.02), and fewer had cerebrovascular accident as a primary diagnosis (22.6% versus 33.9%, P < 0.05), than the total population of long-term care patients at this hospital. Following data collection, reasons for patients being on a puréed diet were grouped into five categories. The most popular categories were "Physiological/Mechanical" and "Cognitive" problems.  相似文献   
86.
Culprits in the degradation of cyclin E apprehended   总被引:4,自引:0,他引:4       下载免费PDF全文
  相似文献   
87.
Rapidly progressive dementia in an adult with findings of bilateral, symmetric high signal intensity on T2-weighted sequences and normal findings on T1-weighted sequences predominantly in the deep grey matter is suggestive of Creutzfeldt-Jakob disease (CJD). The peripheral cortex may be involved, as it was in the present case. The absence of subcortical periventricular white matter high signal intensity suggests that symmetric high signal intensities within the basal ganglia and cortical grey matter are more likely to be due to a degenerative process rather than due to ischaemia, infection or tumour.  相似文献   
88.
The acquired painful flatfoot in the adult is a syndrome that commonly is disabling and progressive. Patients should benefit from a surgical technique that can provide correction of the major deformities and lasting stability with limited surgical morbidity. Twenty-nine patients treated with a talonavicular arthrodesis for this disorder were followed up a minimum of 12 months and an average of 26 months. Twenty-five patients (86%) were satisfied with no or minor reservations and achieved good or excellent results. A talonavicular arthrodesis, by addressing the instability at its focal point, appears to achieve these goals with one surgical procedure.  相似文献   
89.
Sleep disruption and other circadian rhythm disturbances are frequently seen in dementia patients. In this study, we examined the suprachiasmatic nucleus (SCN), the putative site of the hypothalamic circadian pacemaker, to determine the nature and degree of pathologic changes caused by severe dementia. Neuropathologic examination indicated that among 30 patients with a clinical history of severe dementia, 22 had Braak and Braak stage V-VI Alzheimer disease, 3 had combined Alzheimer and Parkinson disease, 3 had Pick disease and 2 had severe hippocampal sclerosis. Comparisons were made with a control group composed of 13 age-matched patients with no clinical or pathological evidence of dementia or other CNS disorders. To determine the pathologic involvement within the SCN, human hypothalami were stained with: Nissl, Bielchowsky silver, thioflavin S and specific antibodies directed against vasopressin (VP), neurotensin (NT), neuropeptide Y (NPY), vasoactive intestinal peptide (VIP), beta-amyloid (B/A4) and glial fibrillary acidic protein (GFAP). Pathologic damage was primarily limited to neuronal loss and neurofibrillary tangle formation. Only rare diffuse plaques were noted. The pathologic changes within the SCN were less severe than in the other brain regions. Morphometric analysis was accomplished using a stereological approach to sample the average total number of positively stained neurons and astrocytes in 10 different 0.1mm2 microscopic fields in the dorsal subdivision of the SCN. Patients with Alzheimer disease exhibited a significant decrease in vasopressin (9.75 vs 16.7, p < 0.001) and neurotensin (6.82 vs 9.63, p < 0.002) neurons, as well as a corresponding increase in the GFAP-stained astrocyte/Nissl-stained neuron ratio (0.54 vs 0.10, p < 0.009). These studies provide evidence that both vasopressin and neurotensin neurons are lost in Alzheimer disease, and that the astrocyte/neuron ratio is a reliable indicator of disease-related pathology within the SCN. Taken collectively, our data support the hypothesis that damage to the SCN may be an underlying anatomical substrate for the clinically observed changes in circadian rhythmicity that have been observed in Alzheimer patients.  相似文献   
90.
BACKGROUND: Brain metabolite levels are measured by proton magnetic resonance spectroscopy (1H MRS) and include N-acetylaspartate (NAA), creatine (Cr), choline (Cho), and lactate and the ratios NAA to Cho and Cr (NAA-ChoCr), NAA-Cr, NAA-Cho, and Cho-Cr. Brain metabolite levels may correlate with the degree of neonatal asphyxia. OBJECTIVE: To determine which brain metabolite ratios have the strongest correlation with the Apgar scores in infants with possible asphyxia; whether the correlation is stronger with basal ganglia (BG) or anterior border-zone metabolites; and whether a combined approach using routine MR imaging (MRI), diffusion-weighted MRI, and MRS can be used to evaluate the severity of neonatal asphyxia. METHODS: Twenty infants with 1-minute Apgar scores of 6 or less were studied at 2 to 28 days of age. The MRS variables were compared with routine and diffusion-weighted brain MRI. Clinical variables and MRS findings were subjected to factor analysis and stepwise multiple regressions to determine interrelationships. RESULTS: The BG region NAA-Cho and NAA-ChoCr ratios correlated with the 1-minute (P<.001) and 5-minute (P = .01 for NAA-Cho; P = .006 for NAA-ChoCr). There was no correlation between metabolite levels and the 10-minute Apgar scores. The stongest predictions exist between the 1-minute Apgar scores and the NAA-Cho and NAA-ChoCr ratios. In the anterior border zone, the only correlation was between the 1-minute Apgar score and the NAA-Cho ratio, but there was a strong age effect in these data. Lactate was found in the BG of 3 infants, all of whom had 5-minute Apgar scores of 6 or less. Three patients had focal lesions on MRI; 2 of these had elevated lactate levels in the abnormal region; and the third, who had an intrauterine stroke, had no lactate in the region. CONCLUSIONS: Correlations between NAA-Cho and NAA-ChoCr ratios and the 1- and 5-minute Apgar scores are stronger in the BG region than in the frontal border zone. The presence or absence of lactate may indicate the severity of the brain insult, and the combination of MRS, MRI, and diffusion-weighted MRI may assist in localizing and predicting a long-term brain injury.  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