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   4885篇
  免费   334篇
  国内免费   31篇
耳鼻咽喉   24篇
儿科学   131篇
妇产科学   90篇
基础医学   765篇
口腔科学   137篇
临床医学   462篇
内科学   1046篇
皮肤病学   107篇
神经病学   606篇
特种医学   139篇
外科学   444篇
综合类   21篇
预防医学   454篇
眼科学   67篇
药学   371篇
中国医学   6篇
肿瘤学   380篇
  2024年   16篇
  2023年   78篇
  2022年   132篇
  2021年   247篇
  2020年   167篇
  2019年   181篇
  2018年   226篇
  2017年   143篇
  2016年   171篇
  2015年   210篇
  2014年   260篇
  2013年   320篇
  2012年   466篇
  2011年   439篇
  2010年   241篇
  2009年   184篇
  2008年   293篇
  2007年   325篇
  2006年   252篇
  2005年   247篇
  2004年   221篇
  2003年   154篇
  2002年   136篇
  2001年   18篇
  2000年   7篇
  1999年   23篇
  1998年   18篇
  1997年   21篇
  1996年   12篇
  1995年   7篇
  1994年   15篇
  1993年   6篇
  1992年   3篇
  1991年   2篇
  1990年   2篇
  1989年   3篇
  1986年   1篇
  1983年   1篇
  1972年   1篇
  1971年   1篇
排序方式: 共有5250条查询结果,搜索用时 15 毫秒
91.
92.
Objective A recent study evidenced by metyrapone test a central adrenal insufficiency (CAI) in 60% of Prader–Willi syndrome (PWS) children. These results were not confirmed in investigations with low [Low‐Dose Tetracosactrin Stimulation Test (LDTST), 1 μg] or standard‐dose tetracosactrin stimulation tests. We extended the research by LDTST in paediatric patients with PWS. Design Cross‐sectional evaluation of adrenal stress response to LDTST in a PWS cohort of a tertiary care referral centre. Patients Eighty‐four children with PWS. Measurements Assessment of adrenal response by morning cortisol and ACTH dosage, and 1‐μg tetracosactrin test. Response was considered appropriate when cortisol reached 500 nm ; below this threshold, patients were submitted to a second test. Responses were correlated with the patients’ clinical and molecular characteristics to assess genotype–phenotype correlation. Results Pathological cortisol peak responses to the LDTST were registered in 12 patients (14·3%) who had reduced basal (169·4 ± 83·3 nm ) and stimulated (428·1 ± 69·6 nm ) cortisol levels compared to patients with normal responses (367·1 ± 170·6 and 775·9 ± 191·3 nm , P < 0·001). Body mass index standard deviation score was negatively correlated with basal and peak cortisol levels (both P < 0·001), and the patients’ ages (P < 0·001). In patients with deletion on chromosome 15, the cortisol peak was significantly lower than that in uniparental disomy (UPD) cases (P = 0·030). At multiple regression analysis, the predictors of peak response were basal cortisol, age, and UPD subclass (r2 = 0·353, P < 0·001). Standard‐dose (250 μg) tetracosactrin test confirmed CAI in 4/12 patients (4·8% of the cohort). Conclusions Our results support the hypothesis that, albeit rare, CAI may be part of the PWS in childhood.  相似文献   
93.
Bajwah S  Higginson IJ  Ross JR  Wells AU  Birring SS  Patel A  Riley J 《Lung》2012,190(2):215-220

Background  

This study aimed to assess the palliative care needs of progressive idiopathic fibrotic interstitial lung disease (PIF-ILD) populations in two London ILD centres.  相似文献   
94.
95.
96.

Objective

The aim of this study is to assess whether C1772T and G1790A hypoxia-inducible factor-1 (HIF-1)α polymorphisms are associated with risk of oral lichen planus (OLP).

Material and methods

Restriction fragment length polymorphism analysis was used to investigate HIF-1α C1779T and G1790A polymorphisms in 32 OLP and 88 individuals without OLP.

Results

The frequency of the CC, TT, GA, and AA genotypes was higher in patients with OLP. Notably, individuals carrying the C and A, and T and A haplotypes showed a significant association OLP risk.

Conclusions

Our study demonstrated that the C1772T and G1790A polymorphisms of HIF-1α gene increased the risk of OLP. C1772T and G1790A polymorphisms of HIF-1α gene had differing patterns of allelic imbalance in the normal samples and subsequent chronic lesions. Further studies are necessary to elucidate the HIF-1α pathway in OLP, which would facilitate the development of novel therapeutic strategies for the prevention and treatment of OLP.

Clinical relevance

These results, in conjunction with previous studies, suggest that HIF-1α may play important roles in the chronicity of oral mucosa lesions of OLP patients. Taken together, we suggest that HIF-1α polymorphisms enhance its target genes, thereby altering the microenvironment and supporting sequential release of inflammatory mediators or cellular events in OLP. It appears unlikely that inhibition of a single proinflammatory mediator will prove useful in clinical practice, but several ways to reprogram mediators engaged in a wide array of roles simultaneously are encouraging.  相似文献   
97.

Background

Meningiomas are mostly benign, but they may have a notorious tendency to recur when total resection is not possible. Systemic chemotherapeutical treatment has been largely disappointing. The treatment of meningiomas with the cyclooxygenase-2 (COX-2) inhibitor celecoxib showed inhibitory-growth effects in vitro and in vivo after subcutaneous transplantation into mouse. So far, celecoxib has never been tested in an orthotopic model of meningioma. In this work, we tested the effects of celecoxib on the growth of human benign meningiomas after transplantation into the prefrontal cortex of nude mice after confirming the inhibitory in vitro effect on these cells.

Methods

Primary cell cultures were stereotactically implanted into mice and were treated with 0, 750, or 1,500 ppm celecoxib for 3 months. The mice were then killed and blood was analyzed for celecoxib concentration. The mice brains were histologically processed for measurement of tumor volume, COX-2 expression, proliferation index (PI), intratumoral microvessel density (iMVD), and vascular endothelial growth factor (VEGF) expression.

Results

Treatment with celecoxib had no effect on tumor volume, despite the fact that we found a dose-dependent inhibitory effect on cell cultures and there was a sufficiently high celecoxib concentration in blood plasma and brain tissue. Additionally, celecoxib had neither an effect on COX-2 and VEGF expression nor on the PI and iMVD.

Conclusions

Our findings suggest that celecoxib may not be effective on meningioma growth in clinical settings. In general, these results may indicate that the effect of treatment on brain tumors should not only be tested in a heterotopic environment but also in the orthotopic location of these tumors.  相似文献   
98.
A subset of over-expressed microRNAs (miRNAs) identified in parathyroid carcinomas (Ca) compared to normal glands belongs to C19MC, a cluster on chromosome 19q13.4 involved in stem cell biology and tumourigenesis. In this study, the expression of C19MC-MIR371-3 clusters and the molecular mechanisms presiding their modulation were investigated in a series of six normal parathyroids, 24 adenomas (Ad), 15 Ca and five matched metastases. The general expression levels of C19MC or MIR371-3 clusters in Ad lesions did not differ from normal glands, while they distinguished Ad from Ca at unsupervised hierarchical cluster analysis (P=0.0008). MIR517C showed the most significant difference in expression between Ca and Ad (P=0.0003) and it positively correlated with serum calcium, parathormone and tumour weight. In regard to the molecular mechanism determining C19MC cluster activation, we could detect C19MC copy number (CN) gain in ten Ca (67%) extending distal to the MIR371-3 cluster in almost all samples. Conversely, only four Ad (16%) showed C19MC amplification, with one case presenting distal genomic aberration to MIR371-3. Globally, CN variations of 19q13.4 loci were significantly associated with MIR517C up-regulation (P=0.006). Opposite to normal glands where C19MC promoter was methylated, hypomethylation occurred in 15 out of 30 analysed tumours. Though the epigenetic status did not correlate with C19MC miRNA expression levels, loss of C19MC promoter methylation was significantly associated with Ca and metastatic disease (P=0.01). In conclusion, C19MC cluster aberrations are a characteristic of Ca with respect to Ad. Altogether, these evidences point towards a role for 19q13.4 miRNA clusters as oncogenes in parathyroid tumourigenesis.  相似文献   
99.
100.
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