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   19421篇
  免费   1705篇
  国内免费   682篇
耳鼻咽喉   53篇
儿科学   588篇
妇产科学   109篇
基础医学   1835篇
口腔科学   832篇
临床医学   1875篇
内科学   2999篇
皮肤病学   96篇
神经病学   642篇
特种医学   371篇
外国民族医学   3篇
外科学   1574篇
综合类   3082篇
现状与发展   4篇
预防医学   3260篇
眼科学   101篇
药学   2641篇
  7篇
中国医学   1266篇
肿瘤学   470篇
  2024年   51篇
  2023年   340篇
  2022年   526篇
  2021年   994篇
  2020年   689篇
  2019年   674篇
  2018年   562篇
  2017年   608篇
  2016年   825篇
  2015年   880篇
  2014年   1211篇
  2013年   1509篇
  2012年   1189篇
  2011年   1341篇
  2010年   993篇
  2009年   829篇
  2008年   741篇
  2007年   850篇
  2006年   779篇
  2005年   663篇
  2004年   618篇
  2003年   562篇
  2002年   421篇
  2001年   402篇
  2000年   372篇
  1999年   287篇
  1998年   256篇
  1997年   251篇
  1996年   240篇
  1995年   221篇
  1994年   236篇
  1993年   215篇
  1992年   170篇
  1991年   127篇
  1990年   150篇
  1989年   128篇
  1988年   103篇
  1987年   91篇
  1986年   64篇
  1985年   90篇
  1984年   84篇
  1983年   71篇
  1982年   71篇
  1981年   64篇
  1980年   60篇
  1979年   49篇
  1978年   34篇
  1977年   29篇
  1976年   25篇
  1974年   15篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
22.
23.
工作相关肌肉骨骼疾患(WMSDs)是常见的慢性非传染性疾病。WMSDs已成为影响工人健康、降低工人生命质量和造成经济损失的重要因素,可见于多个行业、工种。本文对WMSDs流行现状及人体工效学负荷相关研究进行综述,以期找到职业人群保护的可行方法。  相似文献   
24.
抗生素的定义,首先来自于20世纪40年代链霉素的发现。在随后的几十年中,其他氨基糖苷类抗生素家族被大量发现并广泛应用,一度成为抗革兰阴性菌感染的首选抗生素。但由于其毒副作用较大,并且细菌对其不断产生耐药性,加上其他结构类别的新型抗生素的不断发现,使其一度几乎退出历史舞台。然而随着多重耐药细菌引起的感染率急剧上升,人们开始关注氨基糖苷类抗生素作为几种重要的治疗革兰阴性病原体的方案之一,并且发掘了其在治疗感染性疾病、艾滋病和遗传性疾病的潜力,使这个“老牌”抗生素重焕生机。  相似文献   
25.

Objective

A rapid and worrying emergence of vancomycin-resistant enterococci (VRE) gut colonization is occurring worldwide and may be responsible for outbreaks, especially in healthcare facilities. While no efficient decolonization strategies are recommended, we assessed fecal microbiota transplantation (FMT) to eradicate VRE colonization.

Patients and method

Our main objective was to measure the impact of FMT on decolonization of VRE carriers, confirmed by at least two consecutive negative rectal swabs at one-week interval during a 3-month follow-up period. Patients received no antibiotic prior to the FMT.

Results

After a month only three patients remained colonized with VRE. Decolonization was associated with 87.5% (n = 7) of success after three months as only one patient remained colonized.

Conclusion

Our first results confirm that the FMT seems to be safe, with an impact on VRE colonization over time that may help control outbreaks.  相似文献   
26.
The objective of this study was to investigate the absorption behavior of chikusetsusaponin IVa (CHS‐IVa) in the rat intestine using single‐pass intestinal perfusion (SPIP) and to classify CHS‐IVa into the biopharmaceutics classification system (BCS). The equilibrium solubility of CHS‐IVa was determined by the shaker method. The absorption mechanism of CHS‐IVa in the intestine was studied by comparing the Peff of different concentrations of CHS‐IVa. The intestinal site dependence of CHS‐IVa absorption was studied by comparing the Peff of the same concentration of CHS‐IVa in different intestinal segments. The relationship between CHS‐IVa and intestinal efflux protein was studied by perfusion with an efflux protein inhibitor. The permeability of CHS‐IVa was investigated by comparing the Peff of CHS‐IVa and the reported value. The solubility of CHS‐IVa over the pH range 1.0–7.5 was 14.4 ± 0.29 to 16.9 ± 0.34 mg/ml. The Peff of CHS‐IVa in the duodenum was 1.76 × 10?3 to 2.00 × 10?3 cm/min. The Peff of CHS‐IVa in the jejunum was 1.26 × 10?3 to 1.39 × 10?3 cm/min. The Peff of CHS‐IVa in the ileum was 1.25 × 10?3 to 1.31 × 10?3 cm/min. The Peff of CHS‐IVa in the colon was 1.02 × 10?3 to 1.08 × 10?3 cm/min. There was no statistical difference of the Peff in the four segments at different CHS‐IVa concentrations. The Peff of CHS‐IVa (0.07, 0.7 and 7.0 mg/ml) were all notably smaller than the reported Peff (3.00 × 10?3 cm/min) in the jejunum. The Peff of CHS‐IVa was not influenced by verapamil (P‐gp inhibitor), indomethacin (MRP inhibitor) and pantoprazole (BCRP inhibitor). CHS‐IVa was classified as high solubility, low permeability and BCS III. The main absorptive tracts were the upper intestinal tracts and the rank order of intestinal permeability was duodenum > jejunum ≈ ileum > colon. The transport mechanism of CHS‐IVa in all intestinal segments might be primarily passive transport. CHS‐IVa was not a substrate of P‐gp, MRP and BCRP.  相似文献   
27.
目的:研究碘乙酸钠诱导的大鼠膝骨关节炎(KOA)模型肠道菌群变化情况,探究肠道菌群与KOA的潜在联系。方法:将SPF级大鼠分为空白对照组和KOA组,通过膝关节局部注射碘乙酸钠制造大鼠KOA模型。通过16SrDNA检测大鼠粪便中的肠道菌群变化情况,蛋白印记法检测结肠组织中NF-κB和TNF-α蛋白表达,RT-qPCR检测结肠组织中Caspase-1和IL-1β基因表达情况,苏木精-伊红染色观察结肠黏膜通透性变化,苏木精-伊红染色观察关节滑膜和软骨组织的病理变化情况。ELISA检测血液上清中LBP,IL-1β,TNF-α及IL-10炎症因子水平。结果:与空白对照组相比,从KOA组中筛选出明显变化的肠道菌群,以Akkermansia和疣微菌门变化最为显著,结肠黏膜通透性增加,结肠组织中NF-κB p65及TNF-α蛋白表达升高,结肠组织中Caspase-1和IL-1β基因表达升高,血液中促炎因子LBP,IL-1β及TNF-α蛋白含量升高,抗炎因子IL-10蛋白含量降低。结论:KOA病理状态下肠道菌群发生变化,结肠炎症反应增强,结肠炎症反应或许在提高全身炎症反应水平、促进与肠道菌群相关的KOA的病理进程中起到重要的桥梁作用。  相似文献   
28.
《Journal of endodontics》2019,45(10):1228-1236
IntroductionThe balance between the host proinflammatory immune response and the counteracting anti-inflammatory and reparative responses supposedly determine the outcome of periapical lesions. In this scenario, the vasoactive intestinal peptide (VIP) may exert a protective role because of its prominent immunoregulatory capacity. In this study, we investigated (in a cause-and-effect manner) the potential involvement of VIP in the development of human and experimental periapical lesions.MethodsPeriapical granulomas (n = 124) and control samples (n = 48) were comparatively assessed for VIP and multiple immunologic/activity marker expression through real-time polymerase chain reaction. Experimental periapical lesions (C57Bl/6 wild-type mice) were evaluated regarding endogenous VIP expression correlation with lesion development and the effect of recombinant VIP therapy in lesion outcome. CCR4KO and IL4KO strains and anti-glucocorticoid-induced TNFR-related protein inhibition were used to test the involvement of Treg and Th2 cells in VIP-mediated effects.ResultsVIP expression was more prevalent in periapical granulomas than in controls, presenting a positive association with immunoregulatory factors and an inverse association/correlation with proinflammatory mediators and the receptor activator of nuclear factor kappa B ligand/osteoprotegerin ratio. Endogenous VIP expression up-regulation was temporally associated with lesion immunoregulation and a decline of bone loss. VIP therapy in mice prompted the arrest of lesion development, being associated with an anti-inflammatory and proreparative response that limits the proinflammatory, Th1, Th17, and osteoclastogenic response in the periapex. The VIP protective effect was dependent of Treg migration and activity and independent of interleukin 4.ConclusionsOur results show that VIP overexpression in human and experimental periapical lesions is associated with lesion inactivity and that VIP therapy results in the attenuation of experimental lesion progression associated with the immunosuppressive response involving Treg cells.  相似文献   
29.
The present study included three periods: (1) a 12-month prerestriction and control period in 2001; (2) a 12-month restriction period with reduced ceftazidime prescribing in favor of piperacillin-tazobactam (2002); (3) and a 24 month postrestriction period (2003–2004). Note that, for results, P represents the difference between 2002 and 2001; P′, the difference between 2003 and 2001; and P″, the difference between 2004 and 2001. No changes in hygiene practices were observed during these three periods. The purpose of this study was to assess the effect of reducing ceftazidime use in an intensive care unit (ICU) upon Gram-negative bacterial resistance, particularly as regards Pseudomonas aeruginosa. During the three periods of the study, patients were similar concerning age, Simplified Acute Physiology Score (SAPSII), the site of nosocomial infection, and the requirements for mechanical ventilation (75% in 2001, 76% in 2002, 74% in 2003, and 85% in 2004). The most commonly isolated pathogens were P. aeruginosa, Acinetobacter baumannii, and Enterobacteriaceae. The use of ceftazidime decreased significantly from 12.6% in 2001 to 9% in 2002, to 3% in 2003 (P′ = 0.0009), and 2.6% in 2004 (P″ = 0.0001) in favor of piperacillin-tazobactam (0% 2001 to 3.7% in 2003; P′ = 0.002; and 5% in 2004; P″ = 0.0001). Simultaneously, we observed a significant decrease in isolates of P. aeruginosa resistant to piperacillin-tazobactam (P = 0.03; P′ = 0.004; P″ = 0.009), and those resistant to imipenem in 2003 (P′ = 0.008). We also noted a significant decrease in A. baumannii isolates resistant to ceftazidime (P′ = 0.01; P″ = 0.0004) and those resistant to imipenem in both 2002 and 2004 (P = 0.03; P″ = 0.04), and a considerable decrease in isolates of Klebsiella pneumoniae producing expanded spectrum betalactamase (ESBL) in 2003 and 2004 (P′ = 0.04; P″ = 6.10−5). In contrast, we noted an increase in penicillinase-producing isolates of K. pneumoniae, from 6% in 2001 to 16% in 2002 (p = 0.01), 20% in 2003 (P′ = 0.001), and 32% in 2004 (P″ = 10−6). We concluded that restriction of ceftazidime use was demonstrated to be efficient in reducing antimicrobial resistance, especially to K. pneumoniae ESBL.  相似文献   
30.
Opportunistic infections in the oral cavity of the elderly may increase the incidence of systemic disease. The objective of this study was to investigate the differences in the oral bacterial flora between dependent elderly (inpatients) and independent elderly (community-dwelling residents). After multiple variables were taken into account, inpatients had significantly lower detection rates than community-dwelling residents for alpha-streptococci (p < 0.001) and Neisseria (p 0.004), and higher detection rates for Pseudomonas aeruginosa (p 0.024), methicillin-resistant Staphylococcus aureus (MRSA) (p 0.011) and Actinomyces spp. (p 0.005). Among inpatients, the requirement for a high degree of care was related negatively to detection of alpha-streptococci, but was related significantly to detection of P. aeruginosa (p 0.018) or MRSA (p 0.004). Tube-fed inpatients had a significantly lower detection rate for alpha-streptococci (p 0.041) and a higher detection rate for P. aeruginosa (p 0.004) than those who did not require tube feeding. Inpatients with a history of antibiotic use had a significantly lower detection rate for alpha-streptococci (p 0.049) and a higher detection rate for MRSA (p 0.007) than those without a history of antibiotic use. The detection rates for P. aeruginosa or MRSA in inpatients without alpha-streptococci were higher than in inpatients with alpha-streptococci after controlling for age and gender (P. aeruginosa, p 0.006; MRSA, p 0.001). Overall, detection of alpha-streptococci had an inverse correlation with the detection of P. aeruginosa and MRSA in the oral cavity and is likely to be an indicator of pathogenic bacterial infection.  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