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   46150篇
  免费   3618篇
  国内免费   1408篇
耳鼻咽喉   217篇
儿科学   1065篇
妇产科学   543篇
基础医学   7443篇
口腔科学   1102篇
临床医学   3269篇
内科学   7523篇
皮肤病学   940篇
神经病学   3711篇
特种医学   680篇
外国民族医学   5篇
外科学   3521篇
综合类   6260篇
现状与发展   4篇
预防医学   2103篇
眼科学   547篇
药学   6784篇
  4篇
中国医学   2162篇
肿瘤学   3293篇
  2024年   95篇
  2023年   843篇
  2022年   2012篇
  2021年   1965篇
  2020年   1514篇
  2019年   1746篇
  2018年   1721篇
  2017年   1612篇
  2016年   1442篇
  2015年   1521篇
  2014年   2536篇
  2013年   2733篇
  2012年   2304篇
  2011年   2767篇
  2010年   2192篇
  2009年   2185篇
  2008年   2206篇
  2007年   1971篇
  2006年   1817篇
  2005年   1722篇
  2004年   1622篇
  2003年   1496篇
  2002年   1315篇
  2001年   988篇
  2000年   940篇
  1999年   864篇
  1998年   702篇
  1997年   680篇
  1996年   573篇
  1995年   511篇
  1994年   449篇
  1993年   333篇
  1992年   269篇
  1991年   276篇
  1990年   210篇
  1989年   182篇
  1988年   185篇
  1987年   142篇
  1986年   154篇
  1985年   329篇
  1984年   312篇
  1983年   242篇
  1982年   273篇
  1981年   214篇
  1980年   199篇
  1979年   181篇
  1978年   135篇
  1977年   94篇
  1976年   103篇
  1975年   91篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
AimEssential hypertension (EH) is one of the most important public health problems worldwide. However, the pathogenesis of EH is unclear and early diagnostic methods are lacking. Metabolomics demonstrates great potential for biomarker discovery and the mechanistic exploration of metabolic diseases.Data synthesisThis review included human and animal metabolomics studies related to EH in the PubMed and Web of Science databases between February 1996 and May 2020. The study designs, EH standards, and reported metabolic biomarkers were systematically examined and compared. The pathway analysis was conducted through the online software MetaboAnalyst 4.0.Twenty-two human studies and fifteen animal studies were included in this systematic review. There were many frequently reported biomarkers with consistent trends (e.g., pyruvate, lactic acid, valine, and tryptophan) in human and animal studies, and thus had potential as biomarkers of EH. In addition, several shared metabolic pathways, including alanine, aspartate, and glutamate metabolism, aminoacyl-tRNA biosynthesis, and arginine biosynthesis, were identified in human and animal metabolomics studies. These biomarkers and pathways, closely related to insulin resistance, the inflammatory state, and impaired nitric oxide production, were demonstrated to contribute to EH development.ConclusionsThis study summarized valuable metabolic biomarkers and pathways that could offer opportunities for the early diagnosis or prediction of EH and the discovery of the metabolic mechanisms of EH.  相似文献   
992.
目的探讨老年慢性阻塞性肺疾病急性加重期(AECOPD)患者IL-8、IL-6、TNF-α水平变化和肺功能的相关性。方法选取我院收治的AECOPD患者78例。分别于患者急性加重期和稳定期检测其血清IL-8、IL-6、TNF-α水平以及肺功能。对比不同肺功能综合评估分级的患者IL-8、IL-6、TNF-α的水平,同时对比急性加重期和稳定期患者IL-8、IL-6、TNF-α和FEV1%预计值的检测结果,并分析IL-8、IL-6、TNF-α与FEV1%预计值的相关性。结果肺功能综合评估分级级别越高,其IL-8、IL-6和TNF-α的水平显著增高(p<0.05);COPD急性加重期及稳定期患者的IL-8、IL-6、TNF-α水平和FEV1%预计值水平均呈负相关(p<0.05)。结论老年AECOPD患者IL-8、IL-6和TNF-α水平和FEV1%预计值呈负相关,检测IL-8、IL-6和TNF-α的水平可反应出患者病情的严重程度,有助于临床评估患者的病情,指导临床治疗。  相似文献   
993.
Alzheimer’s disease (AD) and depression in late life are one of the most severe health problems in the world disorders. Serotonin 6 receptor (5-HT6R) has caused much interest for potential roles in AD and depression. However, a causative role of perturbed 5-HT6R function between two diseases was poorly defined. In the present study, we found that a 5-HT6R antagonist, SB271036 rescued memory impairment by attenuating the generation of Aβ via the inhibition of γ-secretase activity and the inactivation of astrocytes and microglia in the AD mouse model. It was found that the reduction of serotonin level was significantly recovered by SB271036, which was mediated by an indirect regulation of serotonergic neurons via GABA. Selective serotonin reuptake inhibitor (SSRI), fluoxetine significantly improved cognitive impairment and behavioral changes. In human brain of depression patients, we then identified the potential genes, amyloid beta (A4) precursor protein-binding, family A, member 2 (APBA2), well known AD modulators by integrating datasets from neuropathology, microarray, and RNA seq. studies with correlation analysis tools. And also, it was demonstrated in mouse models and patients of AD. These data indicate functional network of 5-HT6R between AD and depression.  相似文献   
994.
Oral squamous cell carcinoma (OSCC) is a lethal disease whose incidence is increasing. Epidemiologic studies demonstrate an association between periodontitis and oral cancer, and periodontal pathogens are implicated in the pathogenesis of numerous disorders, including rheumatoid arthritis, cardiovascular diseases, diabetes and gastrointestinal malignancies. Nevertheless, a causal role for periodontal pathogens in OSCC has not been shown, partly due to the lack of an appropriate animal model. Here, utilizing a newly-established murine model of periodontitis-associated oral tumorigenesis, we report that chronic bacterial infection promotes OSCC, and that augmented signaling along the IL-6-STAT3 axis underlies this effect. Our results indicate that periodontal pathogens P. gingivalis and F. nucleatum stimulate tumorigenesis via direct interaction with oral epithelial cells through Toll-like receptors. Furthermore, oral pathogens stimulate human OSCC proliferation and induce expression of key molecules implicated in tumorigenesis. To the best of our knowledge, these findings represent the first demonstration of a mechanistic role for oral bacteria in chemically induced OSCC tumorigenesis. These results are highly relevant for the design of effective prevention and treatment strategies for OSCC.  相似文献   
995.
996.
HDAC inhibitors have been reported to produce antidepressant and pro-cognitive effects in animal models, however, poor brain bioavailability or lack of isoform selectivity of current probes has limited our understanding of their mode of action. We report the characterization of novel pyrimidine hydroxyl amide small molecule inhibitors of HDAC6, brain bioavailable upon systemic administration. We show that two compounds in this family, ACY-738 and ACY-775, inhibit HDAC6 with low nanomolar potency and a selectivity of 60- to 1500-fold over class I HDACs. In contrast to tubastatin A, a reference HDAC6 inhibitor with similar potency and peripheral activity, but more limited brain bioavailability, ACY-738 and ACY-775 induce dramatic increases in α-tubulin acetylation in brain and stimulate mouse exploratory behaviors in novel, but not familiar environments. Interestingly, despite a lack of detectable effect on histone acetylation, we show that ACY-738 and ACY-775 share the antidepressant-like properties of other HDAC inhibitors, such as SAHA and MS-275, in the tail suspension test and social defeat paradigm. These effects of ACY-738 and ACY-775 are directly attributable to the inhibition of HDAC6 expressed centrally, as they are fully abrogated in mice with a neural-specific loss of function of HDAC6. Furthermore, administered in combination, a behaviorally inactive dose of ACY-738 markedly potentiates the anti-immobility activity of a subactive dose of the selective serotonin reuptake inhibitor citalopram. Our results validate new isoform-selective probes for in vivo pharmacological studies of HDAC6 in the CNS and reinforce the viability of this HDAC isoform as a potential target for antidepressant development.  相似文献   
997.
Purpose: We previously developed a novel cryo-thermal therapy to treat malignant mammary carcinoma and melanoma in a mouse model; long-term survival and CD4+ T cell orchestrating anti-tumor immune memory response were achieved. Moreover, cryo-thermal-induced CD4+ T cell differentiation into Th1 and CD4+CTL sub-lineages, in which M1 macrophage polarization played a direct, important role. In particular, cryo-thermal therapy triggered M1 macrophage polarization with up-regulated expression of C–X–C motif ligand 10 (CXCL10) and Interleukin 6 (IL-6). But whether CXCL10 and IL-6 contribute to CD4+ T cell-mediated anti-tumor immunity remains unclear. In this study, the role of cryo-thermal-induced CXCL10 and IL-6 in anti-tumor immunity was determined.

Methods: The level of CXCL10 and IL-6 in spleen and serum was determined by RT-PCR and ELISA on day 14 after cryo-thermal therapy. Splenic dendritic cells (DCs) and macrophages were isolated from cryo-thermal-treated mice on day 5 and 14, and the level of CXCL10 and IL-6 in macrophages and DCs was determined by ELISA. The transwell migration assay was performed to study immune cell migration. In vivo neutralization of CXCL10 or IL-6 was performed to investigate the phenotypic changes of immune cells.

Results: Cryo-thermal therapy induced M1 macrophage polarization with up-regulation of CXCL10 and IL-6 expression in spleen. CXCL10 and IL-6 promoted DCs migration and maturation, and subsequently promoted CD4+ T cell migration and differentiation into Th1 and CD4+ CTL, moreover, reduced myeloid-derived suppressor cells (MDSCs) accumulation.

Conclusions: Cryo-thermal-induced CXCL10 and IL-6 created acute inflammatory environment to initiate a systemically cascading innate and adaptive anti-tumor immunity, which was more permissive for tumor eradication.  相似文献   

998.
BackgroundOmentin is an adipokine expressed in visceral adipose tissue (VAT). In vitro studies demonstrated that omentin induces vasorelaxation in isolated rat mesenteric arteries, and in vivo studies showed inhibition of agonist-induced increases in blood pressure, possibly mediated by nitric oxide (NO)-dependent mechanisms.MethodsWe investigated, in normotensive rats, the effects of subacute omentin-1 administration [8 μg/kg, intraperitoneally (ip), once daily for 14 days] on cardiac activity, blood pressure, plasma concentration of l-citrulline (as a marker of NO production from l-arginine), and the gene expression of adiponectin, tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) in intra-thoracic pericardial adipose tissue (PAT). Electrocardiography (ECG), heart rate (HR), mean blood pressure (MBP), pulse pressure (PP) were monitored before and after treatment with omentin-1 or vehicle.ResultsWith respect to baseline and vehicle, we found a significant decrease of MBP (p < 0.005) and PP (p < 0.05) after treatment with omentin-1, while ECG and HR were not modified. Omentin-1 significantly increased l-citrulline levels in plasma (p < 0.05), and the gene expression of adiponectin in PAT (p < 0.05). On the other hand, we found decreased gene expression of IL-6 (p < 0.005), while TNF-α mRNA in PAT was not affected.ConclusionWe conclude that the hypotensive effects of omentin-1 could be driven by stimulated production of NO in the vascular system, possibly related to increased adiponectin and decreased IL-6 mRNA in PAT.  相似文献   
999.
目的观察银杏达莫注射液对急性脑梗死患者血清白细胞介素-1β(IL-1β)、白细胞介素-6(IL-6)水平的影响。方法 80例急性脑梗死患者随机分为两组,治疗组予以常规措施并加银杏达莫注射液治疗,对照组仅用常规治疗。观察治疗前后血清IL-1β、IL-6水平的变化。结果两组治疗后血清I L-1β、IL-6的浓度较治疗前有明显降低,但治疗组降低较对照组更显着(P<0.05)。结论银杏达莫注射液可显著降低急性脑梗死患者血清IL-1β、IL-6的水平而降低炎症反应,在治疗急性脑梗死中起重要作用。  相似文献   
1000.
Protocatechuic acid (PCA) at 0.5%, 1% or 2% was supplied to d-galactose (DG) treated mice for 8 week. PCA intake at 2% increased its deposit in brain. DG treatment increased brain level of reactive oxygen species, protein carbonyl, carboxymethyllysine, pentosidine, sorbitol, fructose and methylglyoxal (P < 0.05). PCA intake, at 1% and 2%, lowered brain level of these parameters (P < 0.05). DG treatments enhanced activity and protein expression of aldose reductase (AR) and sorbitol dehydrogenase, as well as declined glyoxalase I (GLI) activity and protein expression (P < 0.05). PCA intake at 1% and 2% reduced activity and protein expression of AR (P < 0.05), and at 2% restored GLI activity and expression (P < 0.05). DG injection also elevated cyclooxygenase (COX)-2 activity and expression, and increased the release of interleukin (IL)-1beta, IL-6, tumor necrosis factor-alpha and prostaglandin E2 in brain (P < 0.05). PCA intake decreased these cytokines (P < 0.05), and at 1% and 2% suppressed COX-2 activity and expression (P < 0.05). PCA intake at 1% and 2% also lowered DG-induced elevation in activity, mRNA expression and protein production of nuclear factor kappa B p65 (P < 0.05). These findings suggest that the supplement of protocatechuic acid might be helpful for the prevention or alleviation of aging.  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