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   42522篇
  免费   4703篇
  国内免费   3114篇
耳鼻咽喉   457篇
儿科学   488篇
妇产科学   595篇
基础医学   4289篇
口腔科学   729篇
临床医学   5451篇
内科学   5730篇
皮肤病学   461篇
神经病学   1775篇
特种医学   1584篇
外国民族医学   17篇
外科学   4235篇
综合类   8674篇
现状与发展   18篇
一般理论   5篇
预防医学   3795篇
眼科学   968篇
药学   4774篇
  50篇
中国医学   2777篇
肿瘤学   3467篇
  2024年   120篇
  2023年   531篇
  2022年   1367篇
  2021年   2017篇
  2020年   1552篇
  2019年   1372篇
  2018年   1417篇
  2017年   1480篇
  2016年   1290篇
  2015年   1946篇
  2014年   2419篇
  2013年   2480篇
  2012年   3305篇
  2011年   3453篇
  2010年   2565篇
  2009年   2192篇
  2008年   2431篇
  2007年   2458篇
  2006年   2266篇
  2005年   2085篇
  2004年   1835篇
  2003年   2070篇
  2002年   1773篇
  2001年   1398篇
  2000年   967篇
  1999年   777篇
  1998年   448篇
  1997年   442篇
  1996年   277篇
  1995年   276篇
  1994年   247篇
  1993年   161篇
  1992年   167篇
  1991年   155篇
  1990年   123篇
  1989年   98篇
  1988年   72篇
  1987年   57篇
  1986年   57篇
  1985年   49篇
  1984年   22篇
  1983年   25篇
  1982年   13篇
  1981年   13篇
  1979年   12篇
  1977年   10篇
  1976年   7篇
  1974年   7篇
  1973年   8篇
  1972年   6篇
排序方式: 共有10000条查询结果,搜索用时 718 毫秒
991.

Little research has considered all children while investigating adult children’s role in their older parents’ health and well-being. In this study, we examine the effect of filial piety across all children on parental depressive symptoms. A sample of 432 older parents with 1,223 adult children in a rural county in northern China rated the filial piety level for each child individually. Ratings were then combined across multiple children and organized into an ordinal variable of filial piety including three levels: all children being filial, some of the children being filial, and none of the children being filial. Ordinary least squares linear regression analyses were performed. The results reveal a significant and negative relationship between adult children’s filial piety levels and older parents’ depressive symptoms after controlling for age, gender, marital status, financial strain, chronic conditions, and social support from family and friends, respectively. That is, one level lower in the adult children’s filial piety corresponds to increase in level of older parents’ depressive symptoms. Filial piety seems to benefit older Chinese parents’ mental health net of social support from family and friends in this sample. Including information from all children in the analyses is informative for better understanding the psychological significance of filial piety for healthy aging in China.

  相似文献   
992.
Ding  Yufang  Zhao  Jiuliang  Qian  Junyan  Zhang  Li  Zhang  Shangzhu  Jiang  Nan  Li  Jing  Wu  Chanyuan  Wu  Qingjun  Xu  Dong  Leng  Xiaomei  Wang  Qian  Zhang  Wen  Tian  Xinping  Li  Mengtao  Zeng  Xiaofeng 《Clinical rheumatology》2022,41(5):1371-1379
Clinical Rheumatology - To identify the predictive value of anti-ribosomal P protein (anti-RibP) antibodies on the accrual of neuropsychiatric damage in systemic lupus erythematosus (SLE) patients...  相似文献   
993.
He  Xuxia  Wen  Yubing  Hu  Rongrong  Wu  Haiting  Ye  Wei  Yue  Cai  Qin  Yan  Xia  Peng  Chen  Limeng 《Clinical rheumatology》2022,41(11):3551-3563
Clinical Rheumatology - The typical nephrological presentation of antineutrophil cytoplasmic antibody (ANCA)–associated vasculitis (AAV) is rapidly progressive glomerulonephritis....  相似文献   
994.
Wen  Lihong  Chen  Xin  Cheng  Qi  Nie  Liuyan  Xu  Jieying  Yan  Tingting  Zhang  Xin  Yang  Huanhuan  Sun  Wenjia  Liu  Lei  Xue  Jing  Du  Yan 《Clinical rheumatology》2022,41(11):3419-3427
Clinical Rheumatology - The purpose of this study was to determine the incidence of myositis-specific autoantibodies (MSAs) in a cohort of Chinese patients with idiopathic inflammatory myopathies...  相似文献   
995.
Journal of Thrombosis and Thrombolysis - This study evaluated the risk of major bleeding associated with concomitant use of direct oral anticoagulant (DOAC) and anticancer drugs (ACDs), which share...  相似文献   
996.
Because the impact of periodic limb movements in sleep (PLMS) is controversial, no consensus has been reached on the therapeutic strategy for PLMS in obstructive sleep apnea (OSA). To verify the hypothesis that PLMS is related to a negative impact on the cardiovascular system in OSA patients, this study investigated the basal autonomic regulation by heart rate variability (HRV) analysis. Sixty patients with mild‐to‐moderate OSA who underwent polysomnography (PSG) and completed sleep questionnaires were analysed retrospectively and divided into the PLMS group (n = 30) and the non‐PLMS group (n = 30). Epochs without any sleep events or continuous effects were evaluated using HRV analysis. No significant difference was observed in the demographic data, PSG parameters or sleep questionnaires between the PLMS and non‐PLMS groups, except for age. Patients in the PLMS group had significantly lower normalized high frequency (n‐HF), high frequency (HF), square root of the mean of the sum of the squares of difference between adjacent NN intervals (RMSSD) and standard deviation of all normal to normal intervals index (SDNN‐I), but had a higher normalized low frequency (n‐LF) and LF/HF ratio. There was no significant difference in the Epworth Sleepiness Scale, the Pittsburgh Sleep Quality Index, the Short‐Form 36 and the Hospital Anxiety and Depression Scale between the two groups. After adjustment for confounding variables, PLMS remained an independent predictor of n‐LF (β = 0.0901, P = 0.0081), LF/HF ratio (β = 0.5351, P = 0.0361), RMSSD (β = ?20.1620, P = 0.0455) and n‐HF (β = ?0.0886, P = 0.0134). In conclusion, PLMS is related independently to basal sympathetic predominance and has a potentially negative impact on the cardiovascular system of OSA patients.  相似文献   
997.
目的:了解双相障碍青少年的健康相关危险行为特点。方法:纳入符合疾病和有关健康问题的国际统计分类第十次修订本(ICD-10)双相障碍标准的12~18岁青少年50例(抑郁状态29人,躁狂状态19人,混合状态2人)及性别、年龄相匹配的正常对照100例,完成青少年健康相关危险行为自评问卷(AHRBI),同时由双相障碍患者父母完成青少年健康相关危险行为问卷父母版(AHRBI-P),评估双相障碍青少年在不同疾病状态下的健康相关危险行为。结果:双相障碍组青少年AHRBI总分与攻击与暴力、健康妥协、破坏纪律、无保护性、自杀自伤及吸烟饮酒等6项因子评分均高于正常对照组[如总分,55.5(38,119)vs.46(38,65);P0.05]。其中,26项行为条目双相障碍组评分均高于正常对照组(均P0.05)。双相障碍组AHRBI和AHRBI-P总分及6项因子分之间的差异无统计学意义(均P0.05)。偏相关分析显示(变量赋值抑郁发作=0,躁狂发作=1),AHRBI和AHRBI-P自杀自伤因子得分与发作状态呈负相关(r=-0.32、-0.33;均P0.05),AHRBI攻击与暴力维度下的毁坏财物行为得分与发作状态呈正相关(r=0.32,P0.05)。结论:双相障碍青少年总体健康相关危险行为多于正常对照青少年,并且,患者在6个维度均存在明显增多的健康相关危险行为。评估期间抑郁发作患者自杀风险更高,而躁狂发作患者更易出现毁坏财物行为。  相似文献   
998.
目的 观察动态轴向压应变对三维丝素蛋白支架内成骨细胞成骨相关基因表达的影响。方法 应用动态力学加载仪对实验组小鼠胚胎成骨细胞MC3T3-E1加载动态轴向压应变(5%应变幅度,1 Hz,30 min/d,共21 d),对照组细胞常规静置培养,不施加力学刺激。应用定量PCR检测细胞成骨基因碱性磷酸酶(ALP)、I型胶原(COLⅠ)、骨特异性转录因子(Runx2)、成骨相关转录因子(Osx)、骨钙蛋白(OCN) mRNA表达量。结果 成骨细胞在周期性轴向压应力刺激下,Runx2、Osx及COLⅠ表达分别增加280%、68.9%和79.6%,ALP及OCN表达也分别增加10.7%和26.9%。实验组成骨相关基因mRNA表达与对照组比较,差异具有统计学意义(P<0.05)。结论 成骨细胞复合丝素蛋白生物支架材料在周期性轴向压应力刺激下,成骨基因COLⅠ、Runx2、Osx及OCN表达明显上调,可能是生理状态下压应力刺激促进骨折愈合的重要机制之一。研究结果对于以力学信号为基础的细胞疗法修复骨缺损等疾病具有重要临床价值。  相似文献   
999.
Sturge–Weber syndrome (SWS) is a rare syndrome characterized by capillary‐venous malformations involving skin and brain. Many patients with SWS also suffer from drug‐resistant epilepsy. We retrospectively studied a series of six SWS patients with epilepsy and extensive neurosurgical resections. At time of surgery, the patients' age ranged from 11 to 35 years (with a mean of 20.2 years). All surgical specimens were well preserved, which allowed a systematic microscopical inspection utilizing the 2011 ILAE classification for focal cortical dysplasia (FCD). Neuropathology revealed dysmorphic‐like neurons with hypertrophic cell bodies reminiscent to those described for FCD type IIa in all cases. However, gross architectural abnormalities of neocortical layering typical for FCD type IIa were missing, and we propose to classify this pattern as FCD ILAE type IIIc. In addition, our patients with earliest seizure onset also showed polymicrogyria (PMG; n = 4). The ictal onset zones were identified in all patients by subdural electrodes, and these areas always showed histopathological evidence for FCD type IIIc. Four out of five patients had favorable seizure control after surgery with a mean follow‐up period of 1.7 years. We concluded from our study that FCD type IIIc and PMG are frequently associated findings in SWS. FCD type IIIc may play a major epileptogenic role in SWS and complete resection of the associated FCD should be considered a prognostic key factor to achieve seizure control.  相似文献   
1000.
Probing a wide range of cellular phenotypes in neurodevelopmental disorders using patient-derived neural progenitor cells (NPCs) can be facilitated by 3D assays, as 2D systems cannot entirely recapitulate the arrangement of cells in the brain. Here, we developed a previously unidentified 3D migration and differentiation assay in layered hydrogels to examine how these processes are affected in neurodevelopmental disorders, such as Rett syndrome. Our soft 3D system mimics the brain environment and accelerates maturation of neurons from human induced pluripotent stem cell (iPSC)-derived NPCs, yielding electrophysiologically active neurons within just 3 wk. Using this platform, we revealed a genotype-specific effect of methyl-CpG-binding protein-2 (MeCP2) dysfunction on iPSC-derived neuronal migration and maturation (reduced neurite outgrowth and fewer synapses) in 3D layered hydrogels. Thus, this 3D system expands the range of neural phenotypes that can be studied in vitro to include those influenced by physical and mechanical stimuli or requiring specific arrangements of multiple cell types.Neuronal migration and maturation is a key step in brain development. Defects in this process have been implicated in many disorders, including autism (1) and schizophrenia (2). Thoroughly understanding how neural progenitor cell (NPC) migration is affected in neurodevelopmental disorders requires a means of dissecting the process using cells with genetic alterations matching those in patients. Existing in vitro assays of migration generally involve measurement of cell movement across a scratch or gap or through a membrane toward a chemoattractant in 2D culture systems. Although widely used, such assays may not accurately reveal in vivo differences, as neuronal migration is tightly regulated by physical and chemical cues in the extracellular matrix (ECM) that NPCs encounter as they migrate.In vitro 3D culture systems offer a solution to these limitations (37). Compared with 2D culture, a 3D arrangement allows neuronal cells to interact with many more cells (4); this similarity to the in vivo setting has been shown to lengthen viability, enhance survival, and allow formation of longer neurites and more dense networks in primary neurons in uniform matrices or aggregate culture (8, 9). Indeed, 3D culture systems have been used to study nerve regeneration, neuronal and glial development (1012), and amyloid-β and tau pathology (13). Thus, measuring neuronal migration through a soft 3D matrix would continue this trend toward using 3D systems to study neuronal development and pathology.We sought to develop a 3D assay to examine potential migration and neuronal maturation defects in Rett syndrome (RTT), a genetic neurodevelopmental disorder that affects 1 in 10,000 children in the United States and is caused by mutations in the X-linked methyl-CpG-binding protein-2 (MECP2) gene (14). Studies using induced pluripotent stem cells (iPSCs) from RTT patients in traditional 2D adherent culture have revealed reduced neurite outgrowth and synapse number, as well as altered calcium transients and spontaneous postsynaptic currents (1). However, 2D migration assays seemed unlikely to reveal inherent defects in this developmental process, which could be affected because MeCP2 regulates multiple developmental related genes (15). Migration of RTT iPSC-derived NPCs has not previously been studied.Using a previously unidentified 3D tissue culture system that allows creation of layered architectures, we studied differences in migration of MeCP2-mutant iPSC-derived versus control iPSC-derived NPCs. This approach revealed a defect in migration of MeCP2-mutant iPSC-derived NPCs induced by either astrocytes or neurons. Further, this 3D system accelerated maturation of neurons from human iPSC-derived NPCs, yielding electrophysiologically active neurons within just 3 wk. With mature neurons derived from RTT patients and controls, we further confirmed defective neurite outgrowth and synaptogenesis in MeCP2-mutant neurons. Thus, this 3D system enables study of morphological features accessible in 2D system as well as previously unexamined phenotypes.  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