收费全文 | 1313篇 |
免费 | 101篇 |
国内免费 | 6篇 |
耳鼻咽喉 | 13篇 |
儿科学 | 58篇 |
妇产科学 | 43篇 |
基础医学 | 196篇 |
口腔科学 | 73篇 |
临床医学 | 109篇 |
内科学 | 230篇 |
皮肤病学 | 31篇 |
神经病学 | 59篇 |
特种医学 | 162篇 |
外国民族医学 | 1篇 |
外科学 | 82篇 |
综合类 | 53篇 |
预防医学 | 114篇 |
眼科学 | 42篇 |
药学 | 85篇 |
中国医学 | 15篇 |
肿瘤学 | 54篇 |
2023年 | 3篇 |
2022年 | 13篇 |
2021年 | 38篇 |
2020年 | 27篇 |
2019年 | 32篇 |
2018年 | 37篇 |
2017年 | 34篇 |
2016年 | 39篇 |
2015年 | 45篇 |
2014年 | 48篇 |
2013年 | 75篇 |
2012年 | 82篇 |
2011年 | 74篇 |
2010年 | 77篇 |
2009年 | 67篇 |
2008年 | 61篇 |
2007年 | 70篇 |
2006年 | 46篇 |
2005年 | 38篇 |
2004年 | 23篇 |
2003年 | 21篇 |
2002年 | 18篇 |
2001年 | 25篇 |
2000年 | 18篇 |
1999年 | 18篇 |
1998年 | 36篇 |
1997年 | 34篇 |
1996年 | 35篇 |
1995年 | 35篇 |
1994年 | 23篇 |
1993年 | 21篇 |
1992年 | 7篇 |
1991年 | 5篇 |
1990年 | 9篇 |
1989年 | 16篇 |
1988年 | 16篇 |
1987年 | 11篇 |
1986年 | 15篇 |
1985年 | 9篇 |
1984年 | 17篇 |
1983年 | 14篇 |
1982年 | 12篇 |
1981年 | 13篇 |
1980年 | 16篇 |
1979年 | 4篇 |
1978年 | 10篇 |
1977年 | 4篇 |
1976年 | 10篇 |
1975年 | 7篇 |
1970年 | 2篇 |
Background and purpose:
5-aminosalicylate (5-ASA) raises levels of 6-thioguanine nucleotides (6-TGN), the active metabolites of thiopurines such as azathioprine (AZA). Changes in levels of each individual TGN – 6-thioguanosine mono-, di- and triphosphate (6-TGMP, 6-TGDP, 6-TGTP) – and of 6-methylmercaptopurine ribonucleotides (6-MMPR) after 5-ASA are not known.Experimental approach:
Effects of increasing 5-ASA doses on AZA metabolites were investigated prospectively in 22 patients with inflammatory bowel disease in 4-week study periods. Patients started with 2 g 5-ASA daily, and then were increased to 4 g daily and followed by a washout period. Thiopurine doses remained unchanged throughout the entire study. Levels of 6-TGMP, 6-TGDP, 6-TGTP and 6-MMPR as well as of 5-ASA and N-acetyl-5-aminosalicylic acid (N-Ac-5-ASA) were determined each study period.Key results:
Median baseline levels in 17 patients of 6-TGDP, 6-TGTP and 6-MMPR were 52, 319 and 1676 pmol per 8 × 108 red blood cells respectively. After co-administration of 2 g 5-ASA daily, median 6-TGDP and 6-TGTP levels increased but median 6-MMPR levels were unchanged. Increasing 5-ASA to 4 g daily did not affect median 6-TGDP and 6-TGTP levels, but median 6-MMPR levels decreased. After discontinuation of 5-ASA, both 6-TGDP and 6-TGTP levels decreased and median 6-MMPR levels increased. The 6-TGTP/(6-TGDP+6-TGTP)-ratio did not change during the study, but 6-MMPR/6-TGN ratios decreased.Conclusions and implications:
Individual 6-TGN metabolites increased after addition of 5-ASA, but 6-MMPR-levels and the 6-MMPR/6-TGN ratios decreased. Further studies are needed to decide whether this pharmacokinetic interaction would result in improvement of efficacy and/or increased risk of toxicity of AZA. 相似文献Pilocytic astrocytoma (PA) is a low-grade neoplasm frequently found in childhood. PA is characterized by slow growth and a relatively good prognosis. Genetic mechanisms such as activation of MAPK, BRAF gene deregulation and neurofibromatosis type 1 (NF1) syndrome have been associated with PA development. Epigenetic signature and miRNA expression profile are providing new insights about different types of tumor, including PAs.
MethodsIn the present study we evaluated global miRNA expression in 16 microdissected pediatric PA specimens, three NF1-associated PAs and 11 cerebral white matter (WM) samples by the microarray method. An additional cohort of 20 PAs was used to validate by qRT-PCR the expression of six miRNAs differentially expressed in the microarray data.
ResultsUnsupervised hierarchical clustering analysis distinguished one cluster with nine PAs, including all NF1 cases and a second group consisting of the WM samples and seven PAs. Among 88 differentially expressed miRNAs between PAs and WM samples, the most underexpressed ones regulate classical pathways of tumorigenesis, while the most overexpressed miRNAs are related to pathways such as focal adhesion, P53 signaling pathway and gliomagenesis. The PAs/NF1 presented a subset of underexpressed miRNAs, which was also associated with known deregulated pathways in cancer such as cell cycle and hippo pathway.
ConclusionsIn summary, our data demonstrate that PA harbors at least two distinct miRNA signatures, including a subgroup of patients with NF1/PA lesions.
相似文献Objective
To evaluate the vitamin A status in serum and colostrum of postpartum women with different socioeconomic status, comparing the colostrum retinol supply with the vitamin A requirement of the newborn.Methods
Cross-sectional study conducted with 424 postpartum women. Vitamin A maternal dietary intake was estimated using a food frequency questionnaire. Colostrum and serum retinol levels were measured by high performance liquid chromatography (HPLC). Serum retinol concentrations <20 μg/dL were indicative of vitamin A deficiency (VAD). Vitamin A levels provided by colostrum <400 μgRAE/day were considered as insufficient for term newborns.Results
The mean maternal vitamin A intake during pregnancy was 872.2 ± 639.2 μgRAE/day in low-income women and 1169.2 ± 695.2 μgRAE/day for high-income women (p < 0.005). The prevalence of vitamin A deficiency was 6.9% (n = 18) in the low-income group and 3.7% (n = 6) in the high-income group. The estimated mean retinol intake by infants of the high- and low-income mothers were 343.3 μgRAE/day (85.8% AI) and 427.2 μgRAE/day (106.8% AI), respectively.Conclusions
Serum vitamin A deficiency was considered a mild public health problem in both populations; however, newborns of low-income women were more likely to receive lower retinol levels through colostrum when compared with newborns of high-income mothers. 相似文献![点击此处可从《The American journal of pathology》网站下载免费的PDF全文](/ch/ext_images/free.gif)