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   721篇
  免费   52篇
耳鼻咽喉   4篇
儿科学   60篇
妇产科学   17篇
基础医学   83篇
口腔科学   24篇
临床医学   104篇
内科学   139篇
皮肤病学   21篇
神经病学   35篇
特种医学   32篇
外科学   73篇
综合类   16篇
预防医学   56篇
眼科学   12篇
药学   55篇
中国医学   4篇
肿瘤学   38篇
  2023年   10篇
  2022年   27篇
  2021年   41篇
  2020年   25篇
  2019年   27篇
  2018年   40篇
  2017年   31篇
  2016年   25篇
  2015年   17篇
  2014年   39篇
  2013年   46篇
  2012年   53篇
  2011年   55篇
  2010年   40篇
  2009年   26篇
  2008年   47篇
  2007年   56篇
  2006年   35篇
  2005年   26篇
  2004年   24篇
  2003年   19篇
  2002年   24篇
  2001年   7篇
  2000年   1篇
  1999年   5篇
  1998年   1篇
  1997年   2篇
  1996年   3篇
  1994年   2篇
  1990年   1篇
  1989年   3篇
  1986年   1篇
  1984年   2篇
  1981年   1篇
  1979年   1篇
  1976年   1篇
  1975年   1篇
  1973年   1篇
  1971年   1篇
  1968年   1篇
  1967年   1篇
  1966年   3篇
  1965年   1篇
排序方式: 共有773条查询结果,搜索用时 0 毫秒
1.
2.
Primary ciliary dyskinesia (PCD) is a disorder of structure and function of motor ciliary and dyskinetic activity of ciliary in the fallopian tubes of affected women and could lead to infertility in some cases. In vitro fertilisation (IVF) is a choice of treatment in infertile women with PCD, which could conquer the tubal dysfunction. In this case study, we report a PCD affected woman with infertility who was treated by IVF and pregnancy was achieved but it failed due to the spontaneous abortion. We also performed whole-exome sequencing for this case and her PCD-affected sister, which did not reveal any genetic abnormality related to the PCD or infertility.  相似文献   
3.
As the most abundant natural biopolymer on earth, celluloses have long-term emerged as a capable platform for diverse purposes. In the context of metal nanoparticles applied to catalysis, the alternatives to traditional catalyst supports by using biomass-derived renewable materials, likely nanocelluloses, have been paid a great effort, in spite of being less exploited. In this study, cellulose nanocrystals were isolated from corn leaf via chemical treatment involving alkalizing, bleaching and acid hydrolysis. The crystallinity of obtained cellulose was evaluated in each step, focusing on the effects of reactant concentration and reaction time. Cellulose nanocrystals were characterized by powder X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), evidencing the presence of cellulose nanospheres (crystallinity index of 67.3% in comparison with 38.4% from untreated raw material) in the size range of 50 nm. Without using any additional surfactants or stabilizers, silver nanoparticles (AgNPs) well-dispersed on the surface of cellulose nanocrystals (silver content of 5.1 wt%) could be obtained by a simple chemical reduction using NaBH4 at room temperature. The catalytic activity was evaluated in the selective reductions of 4-nitrophenol towards 4-aminophenol and methyl orange towards aromatic amine derivatives in water at room temperature. The effects of catalyst amount and reaction time were also studied in both reduction processes, showing near-quantitative conversions within 5 minutes and obeying the pseudo-first-order kinetics, with the apparent kinetic rate constants of 8.9 × 10−3 s−1 (4-nitrophenol) and 13.6 × 10−3 s−1 (methyl orange). The chemical structure of the catalytic system was found to be highly stable during reaction and no metal leaching was detected in reaction medium, evidencing adaptability of cellulose nanocrystals in immobilizing noble metal nanoparticles.

As the most abundant natural biopolymer on earth, celluloses have long-term emerged as a capable platform for diverse purposes.  相似文献   
4.
Sarcoidosis is a multisystem disease of unknown origin. Diagnosis remains challenging, based on organ site involvement, histological confirmation of non-caseating granuloma and an appropriate clinical syndrome. Granulomatous bone involvement is rare and may be ignored because it is usually asymptomatic. Vertebrae, ribs and skull localizations are rarely reported. We described an interesting case of a woman with chronic and multiorgan sarcoidosis with unusual bone localizations.  相似文献   
5.
In neonates, bilirubin tends to be deposited in body tissues, especially the skin and mucous membranes. Jaundice is an early symptom of bilirubin excretion disorders. Therefore, the aim of this study was to investigate the effect of clofibrate on reducing neonatal jaundice. In this systematic review, international databases, including PubMed, Scopus, Web of Science, Embase, Cochrane, and Google Scholar, were searched without time and language restrictions. The reference lists of all studies ultimately included were manually searched. In the 17 articles reviewed, with a sample size of 665 people published between 2005 and 2019, the average weight of the neonates varied from 2,186 g to 4,000 g. Furthermore, the average age of neonates varied from 2 days to 9 days. Four doses of clofibrate (25, 30, 50, 100 mg/kg of neonatal body weight) were used. The bilirubin level of neonates significantly decreased in the intervention group 24, 36, 48, and 72 hours after the start of treatment. Clofibrate administration decreased total serum bilirubin, especially from the second day onwards, and also reduced hospitalization time, hospital costs, and side effects from hospitalization.  相似文献   
6.
7.
8.
ObjectiveBoth genetic and environmental factors play roles in Multiple Sclerosis (MS) etiopathogenesis. The relationship between prenatal/perinatal factors/exposures and future MS occurrence in the offspring remains controversial. Here, we aimed to review the available evidence on prenatal/perinatal factors associated with later MS occurrence.MethodWe performed systematic search of PubMed, Web of Science, and Scopus from inception to October 2020. We included original observational studies conducted on human participants addressing the association between prenatal/perinatal factors and MS occurrence. Data were extracted according to the PRISMA guideline. The adjusted odds ratio (OR) with 95% confidence interval (CI) was considered as the desired effect size. The heterogeneity was evaluated by Cochran's Q and I2 and the publication bias was assessed. We excluded gestational/neonatal vitamin D level, season of birth, and latitude because of recently published systematic reviews/meta-analyses on these subjects.ResultsOverall, 2306 records were identified in the primary search. After excluding irrelevant studies, we evaluated 34 studies with contributing data on 100 prenatal/perinatal factors associated with an increased or decreased risk of MS occurrence. In the meta-analyses, we found no statistically significant associations between later MS occurrence in offspring and prenatal smoking exposure (OR = 1.01, 95% CI = 0.77–1.34), mode of delivery (OR = 0.90, 95% CI = 0.52–1.56), birth order (OR = 0.85, 95% CI = 0.72–1.00), and maternal age (OR = 1.34, 95% CI = 0.88–2.04). Paternal age and parents' marital status at the time of childbirth, maternal preeclampsia/ toxemia, forceps use, birth weight, plurality, and preterm birth were the other most studied factors, and none reported to affect MS risk.ConclusionWe found that prenatal smoking exposure, mode of delivery, birth order, and maternal age do not affect risk of future MS development. Moreover, most of the other investigated factors were reported not to affect MS risk in the offspring.  相似文献   
9.
10.
CD36 plays a critical role in the inhibition of angiogenesis through binding to the type 1 repeats of thrombospondin-1 (TSP-1) and activating Fyn tyrosine kinase and MAPK pathways. Here, we reveal a novel association of CD36 with VEGFR-2 and spleen tyrosine kinase (Syk). We also address the correlation between the expression of CD36 and Syk by demonstrating that overexpression of CD36 in HUVECs up-regulates endogenous Syk expression. We also define a new role for TSP-1 and CD36 in the activation of the VEGFR-2 signaling pathway that requires Syk. Our findings also identify a role for Syk as a stimulator of VEGF-A-induced angiogenesis by increasing phosphorylation of Y1175 in VEGFR-2, which is a major tyrosine for promoting VEGF-A-induced endothelial cell migration. Together, these studies introduce a new signaling pathway for TSP-1, CD36, and Syk, and address the role of these proteins in regulating the angiogenic switch.  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