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   117063篇
  免费   9859篇
  国内免费   4594篇
耳鼻咽喉   392篇
儿科学   2656篇
妇产科学   1473篇
基础医学   19095篇
口腔科学   1695篇
临床医学   8795篇
内科学   23980篇
皮肤病学   2058篇
神经病学   6254篇
特种医学   1936篇
外国民族医学   14篇
外科学   7650篇
综合类   16534篇
现状与发展   22篇
预防医学   9838篇
眼科学   1081篇
药学   15345篇
  24篇
中国医学   5469篇
肿瘤学   7205篇
  2024年   221篇
  2023年   1632篇
  2022年   4080篇
  2021年   4519篇
  2020年   3772篇
  2019年   4138篇
  2018年   3936篇
  2017年   3889篇
  2016年   4174篇
  2015年   4469篇
  2014年   7124篇
  2013年   7801篇
  2012年   6966篇
  2011年   7716篇
  2010年   6218篇
  2009年   6024篇
  2008年   5987篇
  2007年   5691篇
  2006年   5230篇
  2005年   4613篇
  2004年   4012篇
  2003年   3510篇
  2002年   2886篇
  2001年   2447篇
  2000年   2029篇
  1999年   1748篇
  1998年   1539篇
  1997年   1409篇
  1996年   1225篇
  1995年   1191篇
  1994年   1039篇
  1993年   800篇
  1992年   728篇
  1991年   636篇
  1990年   557篇
  1989年   483篇
  1988年   457篇
  1987年   383篇
  1986年   345篇
  1985年   744篇
  1984年   762篇
  1983年   616篇
  1982年   674篇
  1981年   533篇
  1980年   498篇
  1979年   451篇
  1978年   346篇
  1977年   263篇
  1976年   283篇
  1975年   249篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
目的探究老年胃癌患者术前血清白细胞介素6 (IL-6)、胃蛋白酶原(PG)Ⅰ、Ⅱ及PG-Ⅰ/Ⅱ比值在患者预后评估中的意义。方法选择2016年1月—2017年1月南通大学附属海安医院收治的101例外科手术治疗的老年胃癌患者为研究对象。收集患者的临床病理资料,检测血清IL-6和PG-Ⅰ/Ⅱ水平。以全因死亡为随访终点,使用Kaplan-Meier曲线明确患者预后与各指标间的关系。结果受试者工作特征曲线提示,IL-6、PG-Ⅰ和PG-Ⅰ/Ⅱ比值在最佳切割值为10.23pg/mL、30.65μg/L和2.44时,可评估患者的预后,而PG-Ⅱ则无法评估患者的预后。与IL-6≤10.23pg/mL组相比,IL-6> 10.23pg/mL组的肿瘤细胞分化更差、TNM分期Ⅲ期比例明显升高。Kaplan-Meier曲线结果表明,IL-6> 10.23pg/mL组的中位生存期显著短于IL-6≤10.23pg/mL组(28个月vs47个月,P<0.001);PG-Ⅰ≤30.65μg/L组的中位生存期显著短于PG-Ⅰ>30.65μg/L组(34个月vs49个月,P=0.008);PG-Ⅰ/Ⅱ≤2.44组的中位生存期显著短于PG-Ⅰ/Ⅱ> 2.44组(29个月vs56个月,P=0.02)。多因素Cox回归分析表明,肿瘤分化程度、TNM分期、IL-6及PG-Ⅰ/Ⅱ比值是影响患者生存率的独立危险因素。结论术前检测IL-6及PG-Ⅰ/Ⅱ比值有助于评估老年胃癌患者的预后。  相似文献   
2.
背景 致密性骨炎(OCI)和其他疾病有时难以鉴别,探讨血清骨转换生化标志物可为OCI的鉴别诊断提供依据。 目的 探索女性OCI患者的血清骨转换生化标志物的水平变化及临床意义。 方法 回顾性选取2013年6月至2022年2月在北京积水潭医院门诊及住院诊断为OCI的61例女性患者作为观察组,年龄15~50岁,平均(33.8±6.6)岁,病程2周~15年。选择同期61例女性体检健康者作为对照组,年龄15~48岁,平均(35.6±7.6)岁。比较两组一般临床资料和血清骨转换生化标志物水平,并对血清骨转换生化标志物与病情相关指标进行相关性分析。 结果 观察组血清白蛋白(45.4±2.9)g/L低于对照组(46.5±2.8)g/L(t=2.190,P<0.05)。血清骨转换生化标志物比较结果显示,观察组血清1型胶原羧基末端肽β特殊序列(β-CTX)〔0.28(0.23,0.37)μg/L〕、N-端骨钙素(OC)〔13.1(11.2,16.2)μg/L〕、25-羟维生素D3〔25-(OH)VD3〕〔(14.1±5.1)μg/L〕低于对照组〔0.36(0.29,0.48)μg/L,15.6(13.7,17.3)μg/L,(17.5±6.6)μg/L〕(Z=-2.983、-3.255,t=3.081,P<0.05)。长病程亚组OC水平〔14.6(12.4,18.5)μg/L〕高于短病程亚组〔11.7(10.2,14.0)μg/L〕(Z=-2.407,P<0.05)。多孕亚组β-CTX〔0.25(0.22,0.32)μg/L〕、OC水平〔12.2(10.3,15.0)μg/L〕低于非多孕亚组〔0.33(0.26,0.44)μg/L、13.4(12.0,18.8)μg/L〕(Z=-2.486、-1.897,P<0.05)。相关性分析显示,观察组血清1型前胶原氨基端延长肽(tP1NP)与妊娠次数、生产次数均呈负相关(rs=-0.276、-0.298,P<0.05),OC与体质指数(BMI)、视觉模拟评分法(VAS)评分、妊娠次数均呈负相关(rs=-0.284、-0.374、-0.360,P<0.05),25-(OH)VD3水平与BMI呈正相关(rs=0.275,P<0.05)。 结论 女性OCI患者血清OC、β-CTX水平明显降低,可为鉴别其他疾病提供依据;血清OC水平可以反映OCI患者的严重程度,同时OC水平与患者妊娠次数相关;tP1NP与妊娠次数、生产次数相关。  相似文献   
3.
The circadian rhythm in humans is determined by the central clock located in the hypothalamus’s suprachiasmatic nucleus, and it synchronizes the peripheral clocks in other tissues. Circadian clock genes and clock-controlled genes exist in almost all cell types. They have an essential role in many physiological processes, including lipid metabolism in the liver, regulation of the immune system, and the severity of infections. In addition, circadian rhythm genes can stimulate the immune response of host cells to virus infection. Hepatitis B virus (HBV) infection is the leading cause of liver disease and liver cancer globally. HBV infection depends on the host cell, and hepatocyte circadian rhythm genes are associated with HBV replication, survival, and spread. The core circadian rhythm proteins, REV-ERB and brain and muscle ARNTL-like protein 1, have a crucial role in HBV replication in hepatocytes. In addition to influencing the virus’s life cycle, the circadian rhythm also affects the pharmacokinetics and efficacy of antiviral vaccines. Therefore, it is vital to apply antiviral therapy at the appropriate time of day to reduce toxicity and improve the effectiveness of antiviral treatment. For these reasons, understanding the role of the circadian rhythm in the regulation of HBV infection and host responses to the virus provides us with a new perspective of the interplay of the circadian rhythm and anti-HBV therapy. Therefore, this review emphasizes the importance of the circadian rhythm in HBV infection and the optimization of antiviral treatment based on the circadian rhythm-dependent immune response.  相似文献   
4.
Breast core biopsies are a standard component of the triple approach that includes clinical examination, imaging and tissue sampling. Conventional cores, diagnostic vacuum assisted biopsy and vacuum assisted excisions are established methods for sampling and managing breast lesions. It is important to be aware of the potential pitfalls in the technical handling and interpretation of the limited core biopsy samples. Here, we present a clinically oriented, well illustrated overview of the common diagnostic pitfalls based on the author's diagnostic and second opinion practice, emphasize the value of clinicopathological correlation and provide histological tips and clues with useful immunohistochemistry to aid the reporting pathologists in their daily interpretation of breast core biopsies.  相似文献   
5.
《Survey of ophthalmology》2023,68(5):940-956
Congenital aniridia is a panocular disorder that is typically characterized by iris hypoplasia and aniridia-associated keratopathy (AAK). AAK results in the progressive loss of corneal transparency and thereby loss of vision. Currently, there is no approved therapy to delay or prevent its progression, and clinical management is challenging because of phenotypic variability and high risk of complications after interventions; however, new insights into the molecular pathogenesis of AAK may help improve its management. Here, we review the current understanding about the pathogenesis and management of AAK. We highlight the biological mechanisms involved in AAK development with the aim to develop future treatment options, including surgical, pharmacological, cell therapies, and gene therapies.  相似文献   
6.
7.
陈红亮 《中医学报》2016,(6):910-912
目的:观察理筋通督手法治疗颈性眩晕的临床疗效。方法:将120例颈性眩晕患者随机分成3组,理筋通督组、传统手法组及安慰剂组。理筋通督组采用理筋通督手法;传统手法组采用传统手法;安慰剂组口服维生素C。结果:理筋通督手法可显著减缓患者基底动脉舒张期最低血流速度(P0.05)。理筋通督组有效率为93.67%,传统手法组有效率为67.5%,安慰剂组有效率为17.5%,3组比较差异有统计学意义(P0.05),理筋通督组明显优于其他两组。结论:理筋通督手法治疗颈性眩晕临床疗效显著。  相似文献   
8.
Background: Aniridia is a rare developmental eye disorder characterized by complete or partial iris hypoplasia often accompanied with other ocular changes that affect the cornea, anterior chamber, lens, retina, and optic nerve. Most cases of aniridia are inherited with an autosomal dominant mode of inheritance caused by PAX6 mutations or deletions. To reveal the underlying genetic defect in a four-generation Iranian family with aniridia, we carried out a genetic screening of PAX6.

Methods: Complete ophthalmic examinations were performed for available affected family members. All PAX6 exons and their flanking regions were sequenced for affected individuals. Candidate variation was screened for segregation in the pedigree by Sanger sequencing. Bioinformatics prediction was done to evaluate the deleterious effects of the mutation on protein product. Real-time PCR was used to investigate the impact of the variant on PAX6 mRNA expression.

Results: All patients were diagnosed with isolated aniridia associated with variable phenotypic features including retinal detachment. A novel heterozygous deletion c.320_348delTGTCCGAGGGGGTCTGTACCAACGATAAC (p.Leu107HisfsX16) on PAX6 gene was detected. Decreased mRNA level of PAX6 in the affected individuals indicated that the mutation caused nonsense-mediated mRNA decay (NMD).

Conclusions: To the best of our knowledge, it is the first report on the genetics of aniridia in Iran. Segregation analysis, bioinformatics prediction and confirmation of NMD, all support the proposition that the novel observed PAX6 mutation is the cause of aniridia in the pedigree. Retinal detachment in some of the affected members, which is a rare reported phenotypic feature of aniridia patients, may be associated with this mutation.  相似文献   

9.
  1. The common marmoset (Callithrix jacchus) is a useful experimental animal to evaluate the pharmacokinetics of drug candidates. Cytochrome P450 (P450) 2B enzyme in marmoset livers has been identified; however, only limited information on the enzymatic properties and distribution has been available.

  2. Marmoset P450 2B6 amino acids showed high sequence identities (>86%) with those of primates including humans and cynomolgus monkeys. Phylogenetic analysis using amino acid sequences indicated that marmoset P450 2B6 was closer to human and cynomolgus monkey P450 2B6 than to P450 2B orthologs of other species, including pigs, dogs, rabbits and rodents.

  3. Quantitative polymerase chain reaction analysis using specific primers showed P450 2B6 mRNA predominantly expressed in livers among the five marmoset tissues, similar to those of humans and cynomolgus monkeys.

  4. Marmoset P450 2B6 heterologously expressed in Escherichia coli membranes oxidized 7-ethoxycoumarin, pentoxyresorufin, propofol and testosterone, at roughly similar rates to those of humans and/or cynomolgus monkeys. A high capacity of marmoset P450 2B6 with propofol 4-hydroxylation (at low ionic strength conditions) with a low Km value was relatively comparable to that for marmoset livers.

  5. These results collectively indicated a high propofol 4-hydroxylation activity of P450 2B6 expressed in marmoset livers.

  相似文献   
10.
目的总结近年来股骨转子间骨折在稳定性重建方面的概念演化与研究进展。方法查阅国内外相关文献并结合自身经验,从股骨转子间骨折的解剖特点、稳定型骨折与不稳定型骨折分类、稳定性复位与不稳定性复位、术中加压初始稳定与术后滑动二次稳定、内固定术后稳定性评估、早期下地站立负重等方面进行总结分析。结果股骨转子间骨折发生于股骨颈干骺端转换区,具有天然的内翻不稳定倾向。骨折复位质量是影响后续内固定物安放的最重要前提因素。判断骨折复位质量有对线和对位两方面,对线采用 Garden 指数;在对位方面,随着皮质对位理念(正性、中性、负性)的提出,特别强调前内侧皮质的相互砥住支撑(解剖、正性),是获得骨折稳定性复位的关键,而不再强调后内侧小转子骨块的作用。术后影像学的稳定性评分为早期下地站立负重提供了量化指标。但术中的前内侧皮质支撑复位,在术后头颈骨块滑动获得二次稳定的过程中,仍有皮质对位丢失现象,需研究其危险因素和防范措施。结论股骨转子间骨折在取得良好对线的基础上,只要获得了前内侧皮质的相互砥住和支撑,并用内固定器械维持住,就获得了术后稳定性。术后稳定性评分优良者,可以安全地早期下地负重、站立行走活动。  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