全文获取类型
收费全文 | 2424篇 |
免费 | 191篇 |
国内免费 | 8篇 |
专业分类
耳鼻咽喉 | 20篇 |
儿科学 | 70篇 |
妇产科学 | 41篇 |
基础医学 | 331篇 |
口腔科学 | 22篇 |
临床医学 | 210篇 |
内科学 | 486篇 |
皮肤病学 | 48篇 |
神经病学 | 116篇 |
特种医学 | 168篇 |
外科学 | 364篇 |
综合类 | 100篇 |
一般理论 | 2篇 |
预防医学 | 116篇 |
眼科学 | 55篇 |
药学 | 290篇 |
中国医学 | 11篇 |
肿瘤学 | 173篇 |
出版年
2023年 | 13篇 |
2022年 | 38篇 |
2021年 | 71篇 |
2020年 | 43篇 |
2019年 | 54篇 |
2018年 | 57篇 |
2017年 | 49篇 |
2016年 | 80篇 |
2015年 | 66篇 |
2014年 | 89篇 |
2013年 | 135篇 |
2012年 | 184篇 |
2011年 | 192篇 |
2010年 | 123篇 |
2009年 | 73篇 |
2008年 | 158篇 |
2007年 | 139篇 |
2006年 | 136篇 |
2005年 | 129篇 |
2004年 | 130篇 |
2003年 | 104篇 |
2002年 | 76篇 |
2001年 | 35篇 |
2000年 | 34篇 |
1999年 | 40篇 |
1998年 | 20篇 |
1997年 | 15篇 |
1996年 | 13篇 |
1995年 | 10篇 |
1994年 | 10篇 |
1993年 | 14篇 |
1992年 | 24篇 |
1991年 | 32篇 |
1990年 | 22篇 |
1989年 | 17篇 |
1988年 | 10篇 |
1987年 | 10篇 |
1986年 | 11篇 |
1985年 | 12篇 |
1983年 | 11篇 |
1982年 | 13篇 |
1981年 | 12篇 |
1980年 | 7篇 |
1979年 | 8篇 |
1978年 | 8篇 |
1976年 | 8篇 |
1974年 | 10篇 |
1972年 | 10篇 |
1970年 | 7篇 |
1969年 | 9篇 |
排序方式: 共有2623条查询结果,搜索用时 0 毫秒
1.
S Majumdar S C Orphanoudakis A Gmitro M O'Donnell J C Gore 《Magnetic resonance in medicine》1986,3(4):562-574
The accurate estimation of the spin-spin relaxation time T2 is an important goal in magnetic resonance imaging particularly because it can be used for quantitative tissue characterization. The spin-spin relaxation time T2 may be estimated using multiecho pulse sequences, but the accuracy of the estimate is dependent on the fidelity of the spin-echo amplitudes, which may be severely compromised by rf pulse and static field imperfections. In this paper, the effects of static field inhomogeneities are investigated. The propagation of the errors introduced by off-resonance effects are analyzed through computer simulations and analytical solutions of the Bloch equations. A series of experiments performed on a simple tissue phantom using a whole-body imaging system operating at 6.35 MHz corroborates the simulation and analytical results. For accurate measurements of T2 using a whole-body imaging system it is necessary to correct for these inhomogeneities. A correction scheme which would enable a more accurate estimate of T2 is currently under investigation. 相似文献
2.
M. Barua R. Sinha A. Majumdar 《Indian journal of otolaryngology and head and neck surgery》1993,45(2):87-90
Between 1986–1990, 290 patients with squamouscell carcinoma of the hypopharynx were assessed at the S. S. K. M. Hospital Calcutta,
out of the total of 1460 number of Head Neck cancer, (19.8%). The most frequent initial symptom was a foreign body sensation
in the throat (70%), and males were affected more than females (9.8 : 1.2). The peak age incidence was found between 40 and
50 years (24%). Most of the patients came in advanced stages with cervical lymph node metastases (60%).
One interesting fact that came out from the present study is the Right pyriform fassa was more commonly affected than the
left in righthanded persons (56.9%). Though the reason is not clear it could be due to right — sided swallow, as one side
may be predominant in funtion. 相似文献
3.
Stimulation of enzyme secretion from isolated pancreatic acini by Clostridium difficile toxin B 总被引:1,自引:0,他引:1
G D Vesenka A P Majumdar M A Dubick D M Lyerly T D Wilkins J Silva M C Geokas 《Toxicology letters》1986,34(2-3):261-269
Exposure of isolated rat pancreatic acini to increasing concentrations (10 ng - 800 ng/ml) of toxin B from Clostridium difficile produced a biphasic effect on the rate of secretion of amylase, trypsinogen, and chymotrypsinogen. Whereas doses of toxin B from 10-30 ng/ml increased enzyme secretion by 15-20%, doses between 30 ng and 60 ng/ml showed a regression of this effect, whereafter the rate of secretion of amylase, trypsinogen, and chymotrypsinogen increased with increasing concentrations of the toxin. Toxin B concentration of 800 ng/ml enhanced amylase, trypsinogen and chymotrypsinogen secretion by 119%, 185% and 195%, respectively, when compared with the basal level. Stimulation of enzyme secretion by toxin B was not affected by the presence of either actinomycin-D or cycloheximide, at a concentration which inhibited acinar RNA or protein synthesis by 80-90%. Although toxin B as well as CCK8, carbachol and secretin by themselves caused significant stimulation in amylase, trypsinogen and chymotrypsinogen secretion from isolated pancreatic acini, toxin B together with either CCK8, carbachol or secretin produced no further augmentation in enzyme secretion than what was observed with the secretagogues alone. It is concluded that toxin B of Cl. difficile exerts a direct effect on pancreatic acinar cells as evidenced by stimulation of enzyme secretion. 相似文献
4.
A clinical and genetic study of 56 Saudi Wilson disease patients: identification of Saudi-specific mutations 总被引:3,自引:0,他引:3
M. Al Jumah R. Majumdar S. Al Rajeh A. Awada A. Al Zaben I. Al Traif A. R. Al Jumah Z. Rehana 《European journal of neurology》2004,11(2):121-124
Wilson disease (WD) is a hereditary disorder, with recessive transmission and genetic heterogeneity. Several mutations of ATP7B, the gene underlying WD, were reported in many ethnic groups. In this study, mutation screening in ATP7B of 56 Saudi Arabian WD patients was undertaken. The clinical data of all patients were recorded. The entire ATP7B coding sequence, including intron-exon boundaries were screened for mutation by the polymerase chain reaction (PCR)-based mutation detection technique and DNA sequencing. Thirty-nine patients were symptomatic at presentation and 17 subjects were pre-symptomatic siblings of affected patients. Fourteen patients had neurological, 11 patients had mixed (hepatic and neurological), and 14 patients had hepatic presentations. Family history suggestive of WD was present in 72% of cases and 68% had consanguineous parents. Genetic analysis showed disease-causing mutations in three exons (exons 8, 19 and 21) of the ATP7B gene in 28 patients (50%). Mutations in exons 21 (18 cases) and 19 (one case) were unique for Saudis. This large series of Saudi patients with WD has shown wide variability in the genomic substrate of WD. There is no correlation between genotype and clinical presentation. 相似文献
5.
Shyamal K Das Tapas K Banerjee Atanu Biswas Trishit Roy Deepak K Raut Arijit Chaudhuri Abhijit Hazra 《Movement disorders》2007,22(14):2031-2036
An epidemiological study on dystonia has not been reported from India. As part of a major study to find out the prevalence of major neurological disorders in the large urban city of Kolkata, Eastern India, we planned to determine the prevalence of primary dystonia. The study design was a cross-sectional study of a sample population obtained through stratified random selection and conducted in a two-stage procedure of screening by a nonprofessional team followed by confirmation of screened positive cases by the study neurologist. A total population of 52,377 was screened, and 29 subjects with dystonia were diagnosed. Out of them 23 subjects had primary dystonias [crude prevalence rate (CPR), 43.91/100,000; 95% confidence interval (CI), 28.41-64.81; age-standardized rates to world standard population, 49.06 (95% CI,31.74-72.41)] and all cases were focal type and predominantly of limb dystonia variety. Mean onset of dystonias were earlier in women (43.5 years) as compared to men (46.6 years). Thus our study on primary dystonia shows higher prevalence when compared with that of many studies globally, predominantly of focal type, earlier onset among women, and more cases of limb dystonias when compared with more prominent blepharospasm and cervical dystonias in western reports. 相似文献
6.
T lymphocytes and activated eosinophils in airway mucosa in fatal asthma and cystic fibrosis. 总被引:14,自引:0,他引:14
M Azzawi P W Johnston S Majumdar A B Kay P K Jeffery 《The American review of respiratory disease》1992,145(6):1477-1482
With the use of monoclonal antibodies (mAb) and immunohistology, the numbers of phenotypically distinct cells infiltrating lung tissue from 15 postmortem (PM) cases of fatal asthma were quantified and compared with 6 cases of cystic fibrosis (CF) (three postmortem, three transplant) and 10 nonasthmatic cases of sudden death matched for age and sex. Tissue eosinophilia was significantly greater (p less than 0.001) in the fatal asthma group than in the CF or sudden death controls. In asthma, approximately 40% of the eosinophilic infiltrate was EG2 positive (an indication of eosinophil activation and secretion of eosinophil cationic protein). The numbers of eosinophils and EG2 positive cells were significantly elevated in the subjects with acute severe asthma who had had a duration of terminal illness exceeding, as compared with less than, 24 h (p less than 0.05). When compared with the sudden death controls, there were increases in the numbers of Dako L C positive cells (i.e., CD45 positive "total leukocytes") in both fatal asthma and CF (p less than 0.01 and 0.05, respectively). The mean number of MT-1 positive (T) cells in the asthma and CF groups was approximately twice that of the control (p less than 0.05 and 0.01, respectively). The mean number of MB2 positive (B) cells was similar for both the asthma and sudden death control groups but was significantly increased in CF (p less than 0.05). The average T:B cell ratios were 6:1, 1:1, and 2:1 in the fatal asthma, CF, and control groups, respectively. The results support a role for the T lymphocyte in the pathogenesis of fatal asthma and CF.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
7.
Mysorekar VV Dandekar CP Satyaprakash BS Sarkar A 《Indian journal of pathology & microbiology》2003,46(1):37-43
Endoscopic biopsies obtained from 275 patients (180 from the upper gastrointestinal tract and 95 from the lower gastrointestinal tract) were studied to compare the accuracy of biopsy imprint cytology and histology in the diagnosis of gastrointestinal lesions, and also to establish the degree of reliability of imprint cytology alone for an early diagnosis of malignancy. Biopsy histology results were found to be correct in 100% cases. Imprint cytology had an overall accuracy of 100%, 96.7%, 95.8% and 95.8% for the diagnosis of malignancies of the oesophagus, stomach, duodenum and colorectum respectively. False negative results were obtained with lymphomas. Regenerative cellular atypia was an important cause for false positive results. It was concluded that imprint cytology can serve as a useful and simple tool for an immediate diagnosis of malignancy. This should be subsequently correlated with histopathology which facilitates exact tumour typing and assessment of tumour invasion. 相似文献
8.
9.
There are two sets of peripheral arterial chemoreceptors in the cat, the carotid bodies innervated by the carotid sinus nerve and the aortic bodies with afferents in the aortic depressor nerves. Reflex stimulation of ventilation in response to hypoxia is abolished acutely after interrupting the sensory pathway from the carotid body chemoreceptors in the cat even though the reflex pathway from the aortic body chemoreceptors is intact. However, in chronically maintained preparations, there is a restoration of the hypoxic response which is mediated by the aortic chemoreflex pathway. It was proposed that restoration was due to a ‘central reorganization’ of chemoreflex pathways which followed interruption of the sensory pathway from the carotid bodies and that the reorganization enhanced the efficacy of the aortic ventilation chemoreflex. This proposal was tested in the present experiments by measuring reflex ventilatory and cardiovascular responses to electrical stimulation of the sensory nerves containing aortic and carotid chemoreceptor afferents following bilateral interruption of carotid sinus nerves and carotid body resection. Responses measured acutely (1–6 h) after interruption were compared with those measured 60–80 and 110–140 days later. At 60–80 days, a chemoreflex response (increase in tidal volume of ventilation) to stimulation of the interrupted carotid sinus sensory pathway was markedly attenuated while the response to stimulation of the uninterrupted pathway in aortic depressor nerves was enhanced. At 110–140 days, the tidal volume response to carotid sinus nerve stimulation was greatly enhanced while the aortic depressor nerve response declined from the elevated level. There were significant but less pronounced changes in the response of other ventilatory and cardiovascular variables to aortic depressor nerve and carotid sinus nerve stimulation.The results support the idea that there is a ‘central reorganization’ of chemoreflex pathways which is reflected functionally by changes in the efficacy of reflexes evoked from aortic depressor nerve and carotid sinus nerve. The changes are analagous to those occurring in somatic reflexes during regeneration of sensory nerves. It is suggested that the changes in efficacy of carotid sinus nerve reflexes are due to a degenerative loss of synapses of the central projections of interrupted carotid sinus nerve sensory axons (degenerative atrophy) and subsequent regenerative like changes (regenerative proliferation) in the central projections. The changes in the efficacy of aortic depressor nerve reflexes may be attributed to formation of new synapses by converging central projections of this uninterrupted pathway (reactive synaptogenesis) and subsequent regression of the newly formed synapses. 相似文献
10.