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   8961篇
  免费   559篇
  国内免费   185篇
耳鼻咽喉   120篇
儿科学   152篇
妇产科学   104篇
基础医学   1319篇
口腔科学   182篇
临床医学   776篇
内科学   1891篇
皮肤病学   196篇
神经病学   583篇
特种医学   603篇
外国民族医学   2篇
外科学   1288篇
综合类   161篇
预防医学   579篇
眼科学   218篇
药学   781篇
  1篇
中国医学   143篇
肿瘤学   606篇
  2023年   79篇
  2022年   277篇
  2021年   376篇
  2020年   182篇
  2019年   255篇
  2018年   272篇
  2017年   199篇
  2016年   318篇
  2015年   402篇
  2014年   483篇
  2013年   542篇
  2012年   862篇
  2011年   756篇
  2010年   378篇
  2009年   358篇
  2008年   532篇
  2007年   443篇
  2006年   430篇
  2005年   358篇
  2004年   336篇
  2003年   334篇
  2002年   262篇
  2001年   179篇
  2000年   166篇
  1999年   155篇
  1998年   79篇
  1997年   54篇
  1996年   48篇
  1995年   41篇
  1994年   27篇
  1993年   38篇
  1992年   38篇
  1991年   47篇
  1990年   27篇
  1989年   36篇
  1988年   36篇
  1987年   27篇
  1986年   26篇
  1985年   26篇
  1984年   17篇
  1983年   21篇
  1982年   17篇
  1981年   12篇
  1980年   14篇
  1979年   19篇
  1978年   12篇
  1976年   10篇
  1974年   9篇
  1970年   12篇
  1968年   9篇
排序方式: 共有9705条查询结果,搜索用时 0 毫秒
71.
三康胶囊对高原移居青年体力作业效率的影响   总被引:1,自引:0,他引:1  
目的探讨在高原服用三康胶囊对移居青年体力作业效率的影响。方法对进驻海拔3 700 m 1年的10名青年在服药前和服药15d后分别用EGM-Ⅱ型踏车功量计做坐位踏车运动,初始负荷功率为50 W,每3 m in递增50 W,以60 r/m in连续踏车至200 W 3 m in后终止。用直线回归法计算每位受试者的PMC170,HR90w、功率200 W时的HR及SaO2,运动终止5 m in后恢复HR,按公式计算心功能指数。结果服药后各项检测指标较服药前均有非常显著性差异(P<0.01)。结论服用三康胶囊能明显提高高原移居青年的体力作业效率。  相似文献   
72.
海拔1400m某部官兵睡眠呼吸暂停低通气综合征患病率调查   总被引:4,自引:2,他引:2  
目的调查某部官兵睡眠呼吸暂停低通气综合征(SAHS)的患病率,为进一步了解移居不同海拔高度不同时间人群的患病情况提供参照,并为制定该病的防治策略提供依据。方法采用整群抽样的方法对驻守海拔1 400 m的某部官兵进行睡眠问卷调查,根据打鼾程度及日间嗜睡评分保守估计人群SAHS患病率。结果在调查的348人中打鼾的发生率为39.08%,中度打鼾者占5.17%,无重度鼾症患者。吸烟和饮酒与打鼾程度相关。有高原接触史的被调查者打鼾发生率高于未曾上过高原者(χ2=7.122,P=0.028)。不同程度的打鼾患者,日间的嗜睡评分有显著性差异(F=3.689,P=0.013)。结论如果仅依据日间Epworth嗜睡量表(ESS)评分≥9分为标准,保守估计驻守海拔1 400 m某部官兵的SAHS患病率为4.02%,打鼾及SAHS是严重危害健康的疾病之一,但未引起人们的重视,需要搞好宣传教育工作。  相似文献   
73.
The mechanical behaviors of two multi-materials, DP590 (steel sheet)–A356 (cast aluminum alloy) and SS330 (steel sheet)–A5052 (aluminum sheet), were studied. A structural adhesive was used for the joining of steel and aluminum at adhesion strengths of 10, 22, and 30 MPa. To demonstrate that the three-point bending properties depend on the difference in strength between steel and aluminum and adhesion strength, optical microscopy (OM), scanning electron microscopy (SEM), and finite-element analysis (FEA) were performed. According to the results of the bending tests on both multi-materials under the same stacking conditions, the flexural stress increased with the improvement in the adhesion strength until interface separation or aluminum fracture. At the same adhesion strength, the DP590 (lower)–A356 (upper) and SS330 (upper)–A5052 (lower) configurations exhibited a tendency to decrease in the sudden stress drop due to aluminum fracture and interface separation. The bending results were analyzed through the FEA and the stress distribution as a function of the stacking and adhesion strength was confirmed.  相似文献   
74.
目的探讨在海拔3 700 m和5 200 m高原口服富氧水对肺功能的影响。方法(1)在海拔3 700 m将20名已习服半年的男性志愿者分为实验组和对照组,实验组口服5%葡萄糖注射液制成的富氧水,对照组口服5%葡萄糖注射液,均每次500 m l,2次/d。饮用3 d后检测其肺功能,检测指标包括FVC、FEV1、FEV1%、MMEF、PEF和MVV。(2)对首次进驻海拔5 200 m的36名男性志愿者,自海拔1 400 m驻地乘汽车2 d到达海拔3 700 m当日随机分实验组和对照组,同前服用富氧水或生理盐水,直至进入海拔5 200 m某哨卡第6天,共服9d后检测肺功能。结果习服志愿者口服富氧水3 d和初进高原志愿者口服富氧水9 d,肺功能指标中FVC、FEV、MMEF、PEF、MVV均显著增高(P〈0.01,或P〈0.05),FEV1%无显著性变化(P〉0.05)。结论在高原口服富氧水能提高移居者的肺通气功能。  相似文献   
75.

Background

Atrophy of the pancreatic parenchyma, which occurs frequently after pylorus-preserving pancreaticoduodenectomy (PPPD), is often associated with pancreatic exocrine insufficiency. Many surgeons prefer to insert a drainage tube into the remnant pancreatic duct primarily to prevent pancreatic leakage at the pancreaticojejunostomy (PJ) after PPPD. Drainage methods vary widely but can be roughly classified as internal or external drainage. This study intended to evaluate their effects on pancreatic parenchymal atrophy following PPPD.

Methods

Fifty-seven patients who underwent PPPD were retrospectively divided into two groups, 28 who underwent external and 29 who underwent internal pancreatic drainage. External drainage tubes were removed 4 weeks after PPPD. The volume of the pancreatic parenchyma was serially measured on abdominal computed tomography (CT) scans before PPPD, as well as 7 days and 3, 6, and 12 months after surgery. Degree of pancreatic parenchymal atrophy was determined by calculating pancreatic volume relative to that on day 7.

Results

Univariate analysis showed that patient sex, age, body mass index, concurrent pancreatitis, pathology, and types of PJ did not significantly affect changes in pancreatic volume following PPPD. The degree of pancreatic volume atrophy did not differ significantly in the external and internal drainage groups. No patient in the external drainage group experienced drainage-related surgical complications. The incidence of PJ leak was comparable in the two groups. Postoperative pancreatic atrophy did not induce new-onset diabetes mellitus at 1 year.

Conclusions

Both external and internal pancreatic drainage methods showed similar atrophy rate of the pancreatic parenchyma following PPPD.  相似文献   
76.
Background/AimsThe worldwide coronavirus disease 2019 pandemic has led endoscopists to use personal protective equipment (PPE) for infection prevention. This study aimed to investigate whether wearing a face shield as PPE affects the quality of colonoscopy.MethodsWe reviewed the medical records and colonoscopy findings of patients who underwent colonoscopies at Asan Medical Center, Korea from March 10 to May 31, 2020. The colonoscopies in this study were performed by five gastroenterology fellows and four expert endoscopists. We compared colonoscopy quality indicators, such as withdrawal time, adenoma detection rate (ADR), mean number of adenomas per colonoscopy (APC), polypectomy time, and polypectomy adverse events, both before and after face shields were added as PPE on April 13, 2020.ResultsOf the 1,344 colonoscopies analyzed, 715 and 629 were performed before and after the introduction of face shields, respectively. The median withdrawal time was similar between the face shield and no-face shield groups (8.72 minutes vs 8.68 minutes, p=0.816), as was the ADR (41.5% vs 39.8%, p=0.605) and APC (0.72 vs 0.77, p=0.510). Polypectomy-associated quality indicators, such as polypectomy time and polypectomy adverse events were also not different between the groups. Quality indicators were not different between the face shield and no-face shield groups of gastroenterology fellows, or of expert endoscopists.ConclusionsColonoscopy performance was not unfavorably affected by the use of a face shield. PPE, including face shields, can be recommended without a concern about colonoscopy quality deterioration.  相似文献   
77.
Histone deacetylase (HDAC) inhibitors are currently being tested as anticancer agents in clinical trials. Chromatin remodeling, such as through histone acetylation, is a fundamental phenomenon in eukaryotic cell biology, bearing implications to numerous physiological and pathological phenomena. Here, we discuss recent data from our own laboratory and those of others demonstrating antifibrotic and renoprotective effect of HDAC inhibitors in diabetic kidneys, and the possible mechanisms including the role of reactive oxygen species. HDAC inhibitors may prove to be a novel class of multitarget agents in the treatment of diabetic nephropathy.  相似文献   
78.
During the course of evolution, animals encountered the harmful effects of fungi, which are strong pathogens. Therefore, they have developed powerful mechanisms to protect themselves against these fungal invaders. β-Glucans are glucose polymers of a linear β(1,3)-glucan backbone with β(1,6)-linked side chains. The immunostimulatory and antitumor activities of β-glucans have been reported; however, their mechanisms have only begun to be elucidated. Fungal and particulate β-glucans, despite their large size, can be taken up by the M cells of Peyer''s patches, and interact with macrophages or dendritic cells (DCs) and activate systemic immune responses to overcome the fungal infection. The sampled β-glucans function as pathogen-associated molecular patterns (PAMPs) and are recognized by pattern recognition receptors (PRRs) on innate immune cells. Dectin-1 receptor systems have been incorporated as the PRRs of β-glucans in the innate immune cells of higher animal systems, which function on the front line against fungal infection, and have been exploited in cancer treatments to enhance systemic immune function. Dectin-1 on macrophages and DCs performs dual functions: internalization of β-glucan-containing particles and transmittance of its signals into the nucleus. This review will depict in detail how the physicochemical nature of β-glucan contributes to its immunostimulating effect in hosts and the potential uses of β-glucan by elucidating the dectin-1 signal transduction pathway. The elucidation of β-glucan and its signaling pathway will undoubtedly open a new research area on its potential therapeutic applications, including as immunostimulants for antifungal and anti-cancer regimens.  相似文献   
79.
目的:观察艾灸对Apo E~(-/-)小鼠主动脉内肿瘤坏死因子(TNF-α)、白细胞介素-10(IL-10)及基质金属蛋白酶9(MMP-9)的影响,并从抑制炎性反应,稳定动脉粥样硬化斑块等角度探讨艾灸在防治动脉粥样硬化中的机制。方法:将48只采用高脂饮食喂养的载脂蛋白E基因敲除小鼠(Apo E~(-/-)小鼠)作为动脉粥样硬化模型,并随机分为3组:艾灸组,模型组,药物对照组。并将16只同龄相同遗传背景的C57BL/6小鼠作为空白对照组。空白组、模型组小鼠每天常规抓取、固定,并放置假艾灸装置。艾灸组小鼠每天抓取固定,并艾灸膻中穴。药物组小鼠每天采用辛伐他汀0.28 mg/100 g灌胃,所有干预20 min/d,6 d/周,干预14周后牺牲,取材检测。Elisa法测定主动脉内TNF-α、IL-10、MMP-9的含量。油红O染色观察胸主动脉病理改变。结果:1)与模型组相比,艾灸组,药物组小鼠主动脉内TNF-α、MMP-9含量明显降低(P0.05),艾灸组,药物组之间无明显差异;与模型组相比,药物组IL-10水平明显升高有统计学意义(P0.05),艾灸组小鼠主动脉内IL-10呈升高趋势,但无统计学意义。2)胸主动脉病理改变:与空白组相比,模型组胸主动脉可见明显的AS斑块,内膜破坏,中膜增厚,平滑肌细胞破坏变性,管腔变狭窄。相比于模型组,艾灸组及药物组主动脉病变明显减轻。结论:1)艾灸可以有效缓解动脉粥样硬化病变,抑制动脉粥样硬化斑块生长;2)艾灸可以抑制体内炎性反应,并具有稳定斑块的作用  相似文献   
80.
We investigated the effects of resveratrol on metastasis in in vitro and in vivo systems. 4T1 cells were cultured in the presence of various concentrations (0-30 µmol/L) of resveratrol. For experimental metastasis, BALB/c mice were injected intravenously with 4T1 cells in the tail vein, and were orally administered various concentrations (0, 100, or 200 mg/kg Body weight) of resveratrol for 21 days. After resveratrol treatment, cell adhesion, wound migration, invasion, and MMP-9 activity were significantly decreased in a dose-dependent manner in 4T1 cells (P < 0.05). The numbers of pulmonary nodules were significantly decreased in mice fed the resveratrol (P < 0.05). The plasma MMP-9 activity was decreased in response to treatment with resveratrol in mice (P < 0.05). We conclude that resveratrol inhibits cancer metastasis both in vitro and in vivo, and this inhibition is likely due to the decrease in MMP-9 activity caused by resveratrol.  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