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   36576篇
  免费   3414篇
  国内免费   975篇
耳鼻咽喉   117篇
儿科学   1847篇
妇产科学   1185篇
基础医学   4092篇
口腔科学   414篇
临床医学   3820篇
内科学   5579篇
皮肤病学   255篇
神经病学   1734篇
特种医学   998篇
外国民族医学   3篇
外科学   3253篇
综合类   4445篇
一般理论   1篇
预防医学   4162篇
眼科学   407篇
药学   4924篇
  19篇
中国医学   1621篇
肿瘤学   2089篇
  2024年   35篇
  2023年   746篇
  2022年   933篇
  2021年   1527篇
  2020年   1557篇
  2019年   1511篇
  2018年   1321篇
  2017年   1451篇
  2016年   1441篇
  2015年   1470篇
  2014年   2511篇
  2013年   3156篇
  2012年   2136篇
  2011年   2359篇
  2010年   1785篇
  2009年   1714篇
  2008年   1819篇
  2007年   1661篇
  2006年   1418篇
  2005年   1362篇
  2004年   1071篇
  2003年   1051篇
  2002年   848篇
  2001年   733篇
  2000年   579篇
  1999年   509篇
  1998年   415篇
  1997年   387篇
  1996年   321篇
  1995年   295篇
  1994年   316篇
  1993年   232篇
  1992年   209篇
  1991年   207篇
  1990年   171篇
  1989年   140篇
  1988年   126篇
  1987年   120篇
  1986年   125篇
  1985年   183篇
  1984年   188篇
  1983年   138篇
  1982年   140篇
  1981年   97篇
  1980年   95篇
  1979年   83篇
  1978年   60篇
  1977年   48篇
  1976年   53篇
  1975年   27篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
2.
目的基于UHPLC-Q-Exactive-Orbitrap-MS技术阐明树舌灵芝主要成分,结合网络药理学探讨其防治新型冠状病毒肺炎的作用机制。方法采用UHPLC-Q-Exactive-Orbitrap-MS技术鉴定树舌灵芝的主要成分;采用Swiss Target Prediction数据平台对鉴定成分进行靶点预测,对核心靶基因进行GO和KEGG富集分析,运用Cytoscape 3.8.0绘制关联网络图,同时通过分子对接评价树舌灵芝核心成分与血管紧张素转化酶Ⅱ(ACE2)及3种新型冠状病毒(SARS-CoV-2)蛋白的结合作用。结果该研究从树舌灵芝中鉴定化合物62个;30个活性化合物主要作用在IL-6、PTGS2和MAPK1等32个核心靶点,通过PI3K/Akt、TNF及肺结核等多条与肺损伤保护相关通路,发挥防治COVID-19的作用;分子对接显示小白菊内酯、1,4-二羟基-2-萘甲酸和瑞香素等核心成分与ACE2及3种SARS-CoV-2蛋白的亲和作用较好。结论该研究初步阐明树舌灵芝的化学成分及潜在作用机制,为筛选树舌灵芝防治COVID-19的药效成分及深入阐明作用机制提供了科学的理论依据。  相似文献   
3.
Metastatic brain disease frequently complicates extra central nervous system (CNS) neoplastic disease, with an increase in reported incidence over time. Brain parenchyma is the commonest anatomical site, with other lesions involving the spinal cord, dura and tissues surrounding the CNS. Metastases are usually characterised by a well-defined border with surrounding brain, although some can show an infiltrative edge. The use of appropriate immunohistochemical panels can help identify the origin of most tumours, and molecular testing should be performed according to the site of origin even if performed on a previous specimen due to potential changes in molecular characteristics. Reliable detection of leptomeningeal metastasis using CSF cytology relies on examination of an adequate volume of fluid; immunocytochemistry and flow cytometry can also be useful in the correct settings. Advances in the field include liquid biopsies, where circulating biomarkers are examined, and the use of methylation profiling to identify primary tumours.  相似文献   
4.
目的 基于网络药理学方法和分子对接技术探究冬虫夏草抗肿瘤的作用机制。方法 利用TCMSP、CNKI、PubMed、Drugbank、Stitch和Swiss target prediction等平台检索冬虫夏草的化学成分和作用靶点;通过GeneCards、OMIM等数据库筛选肿瘤相关基因,运用Cytoscape 3.7.2构建冬虫夏草活性成分-靶点网络,通过String数据库对关键靶点构建网络互作(PPI)网络,并进行基因本体(GO)基因和京都基因和基因组百科全书(KEGG)通路富集分析,最后利用AutoDock Vina软件和Pymol软件对药物有效活性成分和关键靶点进行分子对接验证。结果 共得到冬虫夏草22个化合物,86个抗肿瘤共同靶点,主要包括环加氧酶(PTGS)2、丝裂原活化蛋白激酶3(MAPK3)、过氧化物酶体增生激活受体γ(PPARG)、胱天蛋白酶3(CASP3)、JUN基因等关键靶点。GO分析与KEGG通路结果显示,冬虫夏草抗肿瘤涉及到多种生物学过程以及PPAR、花生四烯代谢、5-羟色胺信号通路等多种信号通路。将关键化合物和靶点进行分子对接,提示冬虫夏草抗肿瘤可能的前5个主要活性成分11,14-二十碳二烯酸、花生四烯酸、黄豆黄素、胆甾醇和豆甾醇与关键靶点PTGS2、PTGS1、PGR、HMGCR和CNR1均能自发结合。结论 初步探讨了冬虫夏草抗肿瘤的主要活性成分、相关靶点及相关通路,发现冬虫夏草可以通过多成分、多靶点、多通路抗肿瘤,为后期实验验证提供了参考依据。  相似文献   
5.
Objective: Breast cancer is the second most common cancer in the world. Many metastasis suppressor genes were identified, including the KISS1 gene which encodes for a 145 amino acid protein (kisspeptin-145), which undergoes proteolytic cleavage resulting in kisspeptin-14, -13 and -10. All of these proteins can activate KISS1 receptor (KISS1R). The role of KP/KISS1R signaling in breast cancer remains controversial. The present study aimed to measure mRNA gene expression of KISS1 receptor in healthy and cancerous breast tissue and to evaluate the association of its level with the available molecular subtypes and the traditional clinico-pathological variables. Methods: The study was done on 41 operable primary breast cancer patients. Biopsies from both tumor tissue and surrounding healthy mammary tissue were taken from all patients. KISS1R mRNA expression level was measured using a quantitative real time PCR.   Results: KISS1R mRNA expression was significantly higher in stage III patients compared to stage II patients. At a cut-off value for KISS1R mRNA expression of 1.75, stage II was discriminated from stage III. A significant positive correlation was found between KISS1R mRNA expression and tumor size as well as lymph nodes metastasis. KISS1R mRNA was highly expressed in ER negative cases compared to ER positive ones, and in PR negative cases compared to PR positive ones. There was a statistically significant difference in KISS1R mRNA expression levels and different molecular subtypes being over-expressed in HER2 and triple negative cancer cases. Conclusion: This study supports other studies suggesting that KISS1/KISS1R may not be acting as a metastasis suppressor in breast cancer. KISS1R mRNA is over expressed in advanced stages of breast cancer and hence it can be used as a prognostic marker for aggressiveness of breast cancer. Also being over expressed in triple negative patients, KISS1R could represent a promising therapeutic target in triple negative cases.  相似文献   
6.
目的:探讨不同起始时间使用咖啡因防治极低出生体质量早产儿呼吸暂停的疗效和安全性。方法:检索PubMed、Cochrane Library、Embase、中国期刊全文数据库(CNKI)、万方数据、生物医学文献(CBM)及维普等数据库,收集各数据库从建库至2020年6月有关极低出生体质量早产儿早期应用咖啡因防治呼吸暂停的病例对照研究,并采用Cochrane系统评价手册5.1.0和Newcastle-Ottawa量表(NOS)对不同类型研究进行质量评价,采用RevMan 5.3进行系统评价。结果:10项文献中,包括5项随机临床对照研究(RCT)和5项回顾性队列研究,文献质量评价结果显示,5项RCT质量等级为B级,5项回顾性队列研究NOS评分为7~9分。共2 665例患儿,其中早期用药组1 515例,晚期用药1 150例。Meta分析结果显示,早期用药组呼吸暂停(AOP)发生率(RR=0.48,95%CI 0.38~0.60,P<0.01)、吸氧时间(SMD=-0.97,95%CI -1.13~-0.80,P<0.01)、机械通气时间(SMD=-0.82,95%CI -1.06~-0.58,P<0.01)、咖啡因用药时间(SMD=-0.42,95%CI -0.56~-0.28,P<0.01)、支气管肺发育不良(BPD)发生率(RR=0.50,95%CI 0.41~0.60,P<0.01)、动脉导管未封闭(PDA)发生率(RR=0.56,95%CI 0.44~0.70,P<0.01)、早产儿视网膜病(ROP)发生率(RR=0.59,95%CI 0.47~0.74,P<0.01)、脑室内出血(IVH)发生率(RR=0.66,95%CI 0.54~0.81,P<0.01)和坏死性小肠结肠炎(NEC)发生率(RR=0.70,95%CI 0.55~0.91,P<0.01)显著低于晚期用药组,而病死率(RR=1.15,95%CI 0.73~1.81,P=0.55)与晚期用药组比较差异无统计学意义。结论:极低出生体质量早产儿早期使用咖啡因能显著降低呼吸暂停发生率、BPD、ROP、PDA、IVH和NEC发生率,减少机械通气、吸氧和咖啡因用药时间,但对病死率无影响。  相似文献   
7.
五味子乙素是五味子中主要活性成分之一,具有多种药理作用。长期研究表明五味子乙素具有保护肝脏、肾脏、肺和心脑血管等作用。五味子乙素的多器官保护作用通过不同的途径起效,作用机制包括抗氧化、抗炎、抗纤维化、促进热休克反应、调节脂质代谢、抑制细胞凋亡。就五味子乙素对各器官的保护作用的分子机制进行了总结,为推进其药理研究和分子机制的阐明以及临床应用提供参考。  相似文献   
8.
目的 观察内镜下低温等离子消融治疗不同炎症分期儿童先天性梨状窝瘘的疗效及并发症发生情况,探讨手术适应证的选择及术后治愈标准判断。 方法 将近3年来收治的45 例先天性梨状窝瘘临床资料进行回顾性分析,根据临床特点将其分为炎症早期、脓肿期和静止期,观察低温等离子内瘘口消融封闭术后的疗效。 结果 所有患儿术后随访6个月~3年,治愈33例(占比73.3%),其中17例患儿完成二次内镜下探查,内瘘口均一次性闭合且术后B超检查未见异常;16例患儿未接受二次手术探查,仅B超随访,未见异常;好转11例(占比24.4%),均未接受二次内镜手术探查,术后B超随访可见微管残留,但随访半年以上无临床症状发作;未愈1例(占比2.3%),该例完成内镜探查,内瘘口已封闭,B超复查示微管残留,术后7个月患侧颈部再次感染,抗感染治疗后痊愈,随访一年未见反复,仍在随访中。炎症早期患儿4例,术后短期内出现颈部脓肿2例,切开排脓后痊愈;脓肿期患儿15例,术后随访期间未再出现颈部感染;炎症静止期患儿26例,术后7个月患侧颈部再次肿胀1例,抗感染治疗后痊愈。术后声音嘶哑1例(静止期),随访1个月恢复,其余无并发症出现。 结论 内镜下低温等离子消融治疗炎症静止期和急性感染期的先天性梨状窝瘘,疗效确切,安全微创,推荐作为初治先天性梨状窝瘘方法首选。  相似文献   
9.
Backgroundand purpose: Although several studies have reported that thread embedding acupuncture (TEA) is effective for lumbar herniated intervertebral disc (LHIVD), the evidence remains limited because previous studies had a high risk of bias. This study aimed to investigate the efficacy and safety of TEA for LHIVD through a rigorously designed trial.Materials and methodsThis was a randomized, patient-assessor-blinded, sham-controlled trial. Participants were screened according to eligibility criteria, and 70 patients with LHIVD were randomly allocated to the TEA and sham TEA (STEA) groups in a 1:1 ratio. Both groups received TEA or STEA treatment at 23 acupoints once per week for eight weeks. Changes in low back pain, radiating pain, Oswestry disability index, Roland–Morris disability questionnaire, EuroQol 5–Dimensions 5–Levels, and global perceived effect were measured at baseline and at 4, 8, 12, and 16 weeks after screening and compared between the two groups.ResultsTEA showed no significant difference in all outcomes compared to STEA immediately after eight weeks of treatment. After an additional eight weeks of follow-up, TEA showed a more significant effect on the low back pain than STEA (p < 0.05) and showed a better tendency in maintaining or enhancing the improvement of radiating pain, function, and quality of life even after the end of treatment. No serious adverse events were observed.ConclusionTEA is effective in improving low back pain in patients with LHIVD and may help improve function and quality of life, especially in the long term.  相似文献   
10.
We discuss the second reported case of NUT carcinoma (NC) arising in the thyroid.1 NC is a rare and aggressive malignancy which usually arises in the midline head and neck structures. The tumour is defined cytogenetically by rearrangements of the NUTM1 gene, most commonly producing the BRD4-NUTM1 fusion oncogene. A 23-year-old-male had a neck mass excised by right hemithyroidectomy following two fine needle aspirates (Thy 3a and Thy 4). Following completion left thyroidectomy with bilateral central neck dissection, further surgery was required to excise recurrent disease from the thyroid bed and right lateral neck. This aggressive clinical course prompted molecular analysis which revealed a BRD4-NUTM1 fusion gene. The initial hemithyroidectomy diagnosis of solid variant papillary thyroid carcinoma with poorly differentiated areas was thus revised to NC. This is a rare site for NC to occur and illustrates the importance of considering this diagnosis in poorly differentiated neoplasms in the head and neck region.1  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