全文获取类型
收费全文 | 15568篇 |
免费 | 1088篇 |
国内免费 | 76篇 |
专业分类
耳鼻咽喉 | 121篇 |
儿科学 | 322篇 |
妇产科学 | 325篇 |
基础医学 | 1905篇 |
口腔科学 | 347篇 |
临床医学 | 1525篇 |
内科学 | 3077篇 |
皮肤病学 | 193篇 |
神经病学 | 1563篇 |
特种医学 | 627篇 |
外科学 | 2390篇 |
综合类 | 183篇 |
现状与发展 | 1篇 |
一般理论 | 28篇 |
预防医学 | 1339篇 |
眼科学 | 520篇 |
药学 | 1195篇 |
中国医学 | 25篇 |
肿瘤学 | 1046篇 |
出版年
2024年 | 17篇 |
2023年 | 144篇 |
2022年 | 289篇 |
2021年 | 624篇 |
2020年 | 305篇 |
2019年 | 459篇 |
2018年 | 538篇 |
2017年 | 396篇 |
2016年 | 406篇 |
2015年 | 501篇 |
2014年 | 674篇 |
2013年 | 800篇 |
2012年 | 1298篇 |
2011年 | 1266篇 |
2010年 | 689篇 |
2009年 | 643篇 |
2008年 | 1003篇 |
2007年 | 1011篇 |
2006年 | 955篇 |
2005年 | 961篇 |
2004年 | 820篇 |
2003年 | 741篇 |
2002年 | 673篇 |
2001年 | 123篇 |
2000年 | 75篇 |
1999年 | 103篇 |
1998年 | 129篇 |
1997年 | 100篇 |
1996年 | 87篇 |
1995年 | 75篇 |
1994年 | 59篇 |
1993年 | 52篇 |
1992年 | 57篇 |
1991年 | 44篇 |
1990年 | 45篇 |
1989年 | 44篇 |
1988年 | 35篇 |
1987年 | 34篇 |
1986年 | 25篇 |
1985年 | 21篇 |
1984年 | 34篇 |
1983年 | 29篇 |
1982年 | 26篇 |
1981年 | 35篇 |
1980年 | 32篇 |
1978年 | 17篇 |
1977年 | 14篇 |
1976年 | 16篇 |
1975年 | 12篇 |
1974年 | 12篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
Effect of inhaled corticosteroids on symptom severity and sputum mediator levels in chronic persistent cough 总被引:6,自引:0,他引:6
Chaudhuri R McMahon AD Thomson LJ MacLeod KJ McSharry CP Livingston E McKay A Thomson NC 《The Journal of allergy and clinical immunology》2004,113(6):1063-1070
BACKGROUND: Chronic cough often lasts for more than 1 year and is associated with airway inflammation. The effect of inhaled corticosteroids on symptom severity and inflammatory mediator levels in these patients is unknown. OBJECTIVE: We sought to determine whether inhaled corticosteroids reduce cough severity and sputum mediator concentrations in patients with chronic persistent cough. METHODS: We performed a double-blind, randomized, placebo-controlled crossover study with inhaled fluticasone, 500 microg twice daily, and placebo for 14 days in 88 patients with cough for more than 1 year, with normal chest radiography and spirometry results. Outcome measures were a daily cough visual analogue scale and induced sputum concentrations of eosinophilic cationic protein (ECP), myeloperoxidase, leukotriene B(4) (LTB(4)), leukotrienes C(4)/D(4)/E(4) (cysteinyl leukotrienes [Cys-LTs]), prostaglandin E(2) (PGE(2)), IL-8, and TNF-alpha. Sputum cell counts, exhaled nitric oxide levels, and carbon monoxide levels were also measured. RESULTS: There was a significant improvement in the cough visual analogue scale after inhaled fluticasone compared with placebo (mean difference, 1.0; 95% CI, 0.4-1.5; P <.001). LTB(4), Cys-LT, and PGE(2) levels were increased in all causes of cough. Sputum ECP counts, exhaled nitric oxide levels, and carbon monoxide levels decreased significantly after inhaled fluticasone. There was no change in sputum cell counts and other mediator concentrations. CONCLUSION: Cough severity and sputum ECP levels are modestly reduced by inhaled corticosteroids in patients with chronic cough persisting for more than 1 year. LTB(4), Cys-LT, PGE(2), IL-8, myeloperoxidase, and TNF-alpha levels are unaltered by this therapy. This raises the possibility that drugs targeted to reduce the effects of these mediators might be of benefit in chronic persistent cough. 相似文献
92.
The perforant-path projection to the hippocampus forms synapses in the apical tuft of CA1 pyramidal neurons. We used computer modeling to examine the function of these distal synaptic inputs, which led to three predictions that we confirmed in experiments using rat hippocampal slices. First, activation of CA1 neurons by the perforant path is limited, a result of the long distance between these inputs and the soma. Second, activation of CA1 neurons by the perforant path depends on the generation of dendritic spikes. Third, the forward propagation of these spikes is unreliable, but can be facilitated by modest activation of Schaffer-collateral synapses in the upper apical dendrites. This 'gating' of dendritic spike propagation may be an important activation mode of CA1 pyramidal neurons, and its modulation by neurotransmitters or long-term, activity-dependent plasticity may be an important feature of dendritic integration during mnemonic processing in the hippocampus. 相似文献
93.
Determinants of the effect of estrogen on the progression of subclinical atherosclerosis: Estrogen in the Prevention of Atherosclerosis Trial 总被引:1,自引:0,他引:1
Karim R Mack WJ Lobo RA Hwang J Liu CR Liu CH Sevanian A Hodis HN 《Menopause (New York, N.Y.)》2005,12(4):366-373
OBJECTIVE: To determine the extent to which the estrogen-induced changes in lipids and markers of carbohydrate metabolism explain the beneficial effect of estrogen therapy on the progression of carotid artery intima-media thickness (IMT) in postmenopausal women. DESIGN: A randomized, double-blind, placebo-controlled, single-center trial enrolling 222 postmenopausal women 45 years and older without cardiovascular disease and with low-density lipoprotein (LDL) cholesterol levels of 3.37 mmol/L or greater (> or = 130 mg/dL). Intervention was unopposed micronized 17beta-estradiol versus placebo. Measurements were made using high-resolution B-mode ultrasonography to measure carotid artery IMT at baseline and every 6 months on-trial. RESULTS: Progression of carotid IMT was inversely related to on-trial high-density lipoprotein (HDL) cholesterol (P = 0.04) and was directly related to on-trial LDL-cholesterol (P = 0.005). Compared with placebo, women randomized to estradiol showed a higher mean on-trial HDL-cholesterol level and a lower mean on-trial LDL-cholesterol level. In contrast, fasting glucose, insulin, and hemoglobin A1C were lowered and insulin sensitivity increased with estradiol therapy, but the changes were not related to carotid IMT progression. On-trial HDL-cholesterol and LDL-cholesterol were significant independent determinants of carotid IMT progression, jointly explaining 30% of the treatment effect of unopposed estrogen on the progression of carotid IMT. CONCLUSION: Unopposed 17beta-estradiol reduced carotid IMT progression in postmenopausal women in part by increasing HDL-cholesterol and decreasing LDL-cholesterol. Although women randomized to estradiol showed improvement in all the markers of carbohydrate metabolism, these factors did not play a significant role in carotid IMT progression. 相似文献
94.
95.
96.
de Jong BC Onipede A Pym AS Gagneux S Aga RS DeRiemer K Small PM 《Journal of clinical microbiology》2005,43(7):3530-3532
Mycobacterium bovis is best identified by screening those isolates of the Mycobacterium tuberculosis complex that have any pyrazinamide (PZA) resistance, using a confirmatory test such as spoligotyping, biochemical testing, or genomic deletion analysis. The sensitivity for detection of M. bovis is lowered to 82% when only PZA-monoresistant isolates are screened. 相似文献
97.
High rates of clustering of strains causing tuberculosis in Harare, Zimbabwe: a molecular epidemiological study
下载免费PDF全文
![点击此处可从《Journal of clinical microbiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Easterbrook PJ Gibson A Murad S Lamprecht D Ives N Ferguson A Lowe O Mason P Ndudzo A Taziwa A Makombe R Mbengeranwa L Sola C Rastogi N Rostogi N Drobniewski F 《Journal of clinical microbiology》2004,42(10):4536-4544
We examined the pattern of tuberculosis (TB) transmission (i.e., reactivation versus recent transmission) and the impact of human immunodeficiency virus (HIV) infection in Harare, Zimbabwe. Consecutive adult smear-positive pulmonary TB patients presenting to an urban hospital in Harare were enrolled. A detailed epidemiological questionnaire was completed, and tests for HIV type 1 and CD4 cell counts were performed for each patient. Molecular fingerprinting of the genomic DNA recovered from cultures of sputum was performed by two molecular typing methods: spacer oligonucleotide typing (spoligotyping) and analysis of variable number of tandem DNA repeats (VNTRs). A cluster was defined as isolates from two or more patients that shared the same spoligotype pattern or the same VNTR pattern, or both. DNA suitable for typing was recovered from 224 patients. The prevalence of HIV infection was 79%. Of 187 patient isolates (78.6%) typed by both spoligotyping and analysis of VNTRs, 147 were identified as part of a cluster by both methods. By spoligotyping alone, 84.1% of patient isolates were grouped into 20 clusters. The cluster size was generally <8 patient isolates, although three large clusters comprised 68, 25, and 23 patient isolates. A total of 89.4% of the patient isolates grouped into 12 clusters defined by analysis of VNTRs, with 2 large clusters consisting of 127 and 13 patient isolates, respectively. Thirty-six percent of patient isolates with a shared spoligotype and 17% with a shared VNTR pattern were geographically linked within Harare, but they were not linked on the basis of the patient's home district. In a multivariate analysis, there were no independent predictors of clustering, including HIV infection status. Comparison with the International Spoligotype database (Pasteur Institute, Pointe a Pitre, Guadeloupe) demonstrated that our three largest spoligotype clusters are well recognized and ubiquitous in Africa. In this epidemiologically well characterized urban population with a high prevalence of HIV infection, we identified a very high level of strain clustering, indicating substantial ongoing recent TB transmission. Geographic linkage could be detected in a proportion of these clusters. A small group of actively circulating strains accounted for most of the cases of TB transmission. 相似文献
98.
Doris Škorić‐Milosavljević Fleur V. Y. Tjong Julien Barc Ad P. C. M. Backx Sally‐Ann B. Clur Karin van Spaendonck‐Zwarts Roelof‐Jan Oostra Najim Lahrouchi Leander Beekman Regina Bökenkamp Daniela Q. C. M. Barge‐Schaapveld Barbara J. Mulder Elisabeth M. Lodder Connie R. Bezzina Alex V. Postma 《American journal of medical genetics. Part A》2019,179(9):1836-1845
The first human mutations in GATA6 were described in a cohort of patients with persistent truncus arteriosus, and the phenotypic spectrum has expanded since then. This study underscores the broad phenotypic spectrum by presenting two patients with de novo GATA6 mutations, both exhibiting complex cardiac defects, pancreatic, and other abnormalities. Furthermore, we provided a detailed overview of all published human genetic variation in/near GATA6 published to date and the associated phenotypes (n = 78). We conclude that the most common phenotypes associated with a mutation in GATA6 were structural cardiac and pancreatic abnormalities, with a penetrance of 87 and 60%, respectively. Other common malformations were gallbladder agenesis, congenital diaphragmatic hernia, and neurocognitive abnormalities, mostly developmental delay. Fifty‐eight percent of the mutations were de novo, and these patients more often had an anomaly of intracardiac connections, an anomaly of the great arteries, and hypothyroidism, compared with those with inherited mutations. Functional studies mostly support loss‐of‐function as the pathophysiological mechanism. In conclusion, GATA6 mutations give a wide range of phenotypic defects, most frequently malformations of the heart and pancreas. This highlights the importance of detailed clinical evaluation of identified carriers to evaluate their full phenotypic spectrum. 相似文献
99.
PCR-reverse line blot typing method underscores the genomic heterogeneity of Borrelia valaisiana species and suggests its potential involvement in Lyme disease
下载免费PDF全文
![点击此处可从《Journal of clinical microbiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Godfroid E Min Hu C Humair PF Bollen A Gern L 《Journal of clinical microbiology》2003,41(8):3690-3698
Detection of the Borrelia burgdorferi sensu lato complex in biological samples is currently done by conventional immunological and molecular biological methods. To improve on the accuracy of these methods and to simplify the procedure for testing large numbers of samples, a solid-phase sandwich hybridization system readily applicable to the detection of PCR products has been designed. This colorimetric detection system relies on the use of polybiotinylated detection probes and of specific capture oligonucleotides covalently linked at allocated positions on nylon membrane strips. From a phylogenetic analysis on a great number of ospA gene sequences, we have designed and synthesized a set of PCR primers specific to the five Borrelia burgdorferi sensu lato genospecies present in Europe and a subset of probes (capture and detection probes) specific to these five genospecies (B. burgdorferi sensu stricto, B. garinii, B. afzelii, B. valaisiana, and B. lusitaniae). This combined PCR hybridization system was evaluated with a large number of various B. burgdorferi isolates and clinical specimens. These analyses clearly showed that the system could be used as a typing method to distinguish five genospecies belonging to the B. burgdorferi sensu lato complex. In addition, the study showed that B. valaisiana strains might be more heterologous than suspected up to now and clustered into three genomic groups. 相似文献
100.
Ko AC Choo-Smith LP Hewko M Leonardi L Sowa MG Dong CC Williams P Cleghorn B 《Journal of biomedical optics》2005,10(3):031118
Early dental caries detection will facilitate implementation of nonsurgical methods for arresting caries progression and promoting tooth remineralization. We present a method that combines optical coherence tomography (OCT) and Raman spectroscopy to provide morphological information and biochemical specificity for detecting and characterizing incipient carious lesions found in extracted human teeth. OCT imaging of tooth samples demonstrated increased light backscattering intensity at sites of carious lesions as compared to the sound enamel. The observed lesion depth on an OCT image was approximately 290 microm matching those previously documented for incipient caries. Using Raman microspectroscopy and fiber-optic-based Raman spectroscopy to characterize the caries further, spectral changes were observed in PO4 (3-) vibrations arising from hydroxyapatite of mineralized tooth tissue. Examination of various ratios of PO4 (3-) nu2, nu3, nu4 vibrations against the nu1 vibration showed consistent increases in carious lesions compared to sound enamel. The changes were attributed to demineralization-induced alterations of enamel crystallite morphology and/or orientation. OCT imaging is useful for screening carious sites and determining lesion depth, with Raman spectroscopy providing biochemical confirmation of caries. The combination has potential for development into a new fiber-optic diagnostic tool enabling dentists to identify early caries lesions with greater sensitivity and specificity. 相似文献