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   34920篇
  免费   2853篇
  国内免费   1652篇
耳鼻咽喉   200篇
儿科学   618篇
妇产科学   720篇
基础医学   6982篇
口腔科学   818篇
临床医学   2605篇
内科学   5647篇
皮肤病学   386篇
神经病学   2449篇
特种医学   900篇
外国民族医学   12篇
外科学   2276篇
综合类   5472篇
现状与发展   9篇
预防医学   2022篇
眼科学   579篇
药学   4025篇
  8篇
中国医学   761篇
肿瘤学   2936篇
  2024年   48篇
  2023年   308篇
  2022年   653篇
  2021年   977篇
  2020年   943篇
  2019年   920篇
  2018年   1017篇
  2017年   1047篇
  2016年   1202篇
  2015年   1429篇
  2014年   2209篇
  2013年   2498篇
  2012年   2331篇
  2011年   2558篇
  2010年   2093篇
  2009年   2024篇
  2008年   2160篇
  2007年   2109篇
  2006年   1962篇
  2005年   1625篇
  2004年   1454篇
  2003年   1200篇
  2002年   1020篇
  2001年   855篇
  2000年   669篇
  1999年   605篇
  1998年   492篇
  1997年   433篇
  1996年   335篇
  1995年   289篇
  1994年   255篇
  1993年   221篇
  1992年   182篇
  1991年   173篇
  1990年   137篇
  1989年   138篇
  1988年   106篇
  1987年   107篇
  1986年   90篇
  1985年   87篇
  1984年   79篇
  1983年   46篇
  1982年   61篇
  1981年   48篇
  1980年   42篇
  1979年   55篇
  1978年   20篇
  1977年   25篇
  1976年   34篇
  1974年   11篇
排序方式: 共有10000条查询结果,搜索用时 171 毫秒
1.

Background

Resistin is an immunometabolic mediator that is elevated in several inflammatory disorders. A ligand for Toll-like receptor 4, resistin modulates the recruitment and activation of myeloid cells, notably neutrophils. Neutrophils are major drivers of cystic fibrosis (CF) lung disease, in part due to the release of human neutrophil elastase- and myeloperoxidase-rich primary granules, leading to tissue damage. Here we assessed the relationship of resistin to CF lung disease.

Methods

Resistin levels were measured in plasma and sputum from three retrospective CF cohorts spanning a wide range of disease. We also assessed the ability of neutrophils to secrete resistin upon activation in vitro. Finally, we constructed a multivariate model assessing the relationship between resistin levels and lung function.

Results

Plasma resistin levels were only marginally higher in CF than in healthy control subjects. By contrast, sputum resistin levels were very high in CF, reaching 50–100 fold higher levels than in plasma. Among CF patients, higher plasma resistin levels were associated with allergic bronchopulmonary aspergillosis, and higher sputum resistin levels were associated with CF-related diabetes. Mechanistically, in vitro release of neutrophil primary granules was concomitant with resistin secretion. Overall, sputum resistin levels were negatively correlated with CF lung function, independently of other variables (age, sex, and genotype).

Conclusions

Our data establish relationships between resistin levels in the plasma and sputum of CF patients that correlate with disease status, and identify resistin as a novel mechanistic link between neutrophilic inflammation and lung disease in CF.  相似文献   
2.
Objective: Association of matrix metalloproteinases (MMPs) gene polymorphisms with rheumatoid arthritis is controversial. We conduct a meta-analysis to clarify this dispute.

Methods: We systematically searched the electronic PUBMED, EMBASE and CNKI databases for research articles about MMPs (MMP-1, MMP-2, MMP-3, MMP-9) gene polymorphisms and rheumatoid arthritis (RA) up to January 2015. According to the heterogeneity, fixed-effects or random-effects models were used to calculate crude odds ratios (ORs) and 95% confidence intervals (95% CIs).

Results: A total of 11 articles involving 2143 cases and 2049 controls were included in this meta-analysis. Overall, no significant associations were observed between MMP-1-1607 1G/2G polymorphism and RA. Stratification by ethnicity, no significant associations were observed in Caucasian populations. Similarly, no significant associations were observed between MMP-3-1171 5A/6A, MMP-9-1562 C/T polymorphisms and RA in overall and Caucasian populations, respectively. However, a weak association was found between MMP-2-1306 C/T polymorphism and RA (C vs. T, OR?=?0.813, 95%CI?=?0.694–0.953, p?=?0.010) in overall populations.

Conclusions: The present meta-analysis suggests that MMP-1-1607 1G/2G, MMP-3-1171 5A/6A, MMP-9-1562 C/T polymorphisms are not associated with the susceptibility of RA, but MMP-2 -1306 C/T is weakly associated with susceptibility to RA. Further studies with more sample size are needed for definitive conclusions.  相似文献   
3.
背景与目的:CD44分子是众多肿瘤细胞的标志分子,其表达水平与肿瘤细胞的恶性程度有关。该研究探讨CD44基因中的单核苷酸多态性(single nucleotide polymorphism,SNP)位点与云南汉族人群宫颈癌和非小细胞肺癌(nonsmall cell lung cancer,NSCLC)易感性的相关性。方法:选取了CD44基因中的两个SNP位点rs13347和rs8193,采用TagMan基因分型的方法,分析这两个多态性位点在497例宫颈癌患者和500例健康对照个体以及483例NSCLC患者和471例健康对照个体中的分布特征,并分析CD44基因中的多态性位点与云南汉族人群宫颈癌和NSCLC的相关性。结果:rs13347和rs8193位点等位基因和基因型在宫颈癌组和对照组中的分布频率的差异无统计学意义(P>0.05)。而在NSCLC组和对照组的比较中:rs13347和rs8193位点等位基因在NSCLC组和对照组中的分布频率的差异有统计学意义(P=0.020和P=0.004);这两个位点基因型在NSCLC组和对照组中分布频率的差异有统计学意义(P=0.027和P=0.020);其中rs13347位点等位基因C在NSCLC组中的分布频率显著高于对照组,可能是NSCLC发生的风险因素(OR=1.250,95% CI:1.035~1.509),rs8193位点等位基因C在对照组中的分布频率显著高于NSCLC组,可能是NSCLC发生的保护性因素(OR=0.768,95%CI:0.641~0.921)。单倍型分析结果显示,rs13347C-rs8193T和rs13347T-rs8193C在NSCLC组和对照组中的分布频率差异有统计学意义(P=0.003和0.022);该结果说明单倍型rs13347C-rs8193T可能是云南汉族人群NSCLC发生的风险性因素(OR=1.316,95%CI:1.096~1.579)。结论:CD44基因中的两个SNP位点rs13347和rs8193可能与云南汉族人群宫颈癌发病风险无关,而可能与云南汉族人群NSCLC具有相关性。  相似文献   
4.
《Vaccine》2020,38(50):7916-7927
Respiratory syncytial virus (RSV) is the major cause of acute lower respiratory illness in children of less than 5 years of age which usually results in hospitalization or even in death. Vaccine development is hampered in consequence of a failed vaccine trial with fatalities in the 1960s. Even though research has been more focused on the RSV fusion protein in its pre-fusion conformation, maternal vaccination with post-fusion protein (post F) was considered as a promising vaccine strategy for passive immunization of babies, because post F preserves very potent neutralizing epitopes. We extensively analyzed post F-binding B cell receptor (BCR) repertoires of three vaccinees who received a post F-subunit vaccine in the context of a first-in-human, Phase 1, randomized, observer-blind, placebo-controlled clinical trial (ClinicalTrials.gov Identifier: NCT02298179). In order to compare the vaccine-induced BCR repertoires with BCR repertoires induced by natural infection, we also analyzed pre F- and post F-binding BCRs isolated from a healthy blood donor with relatively high F-binding memory B cell (MBC) frequencies. Analysis of the vaccine-induced repertoires revealed that preferentially VH4-encoded BCRs were expanded in response to vaccination. Estimation of antigen-driven selection further demonstrated that expanded BCRs accumulated positively selected replacement mutations which substantiated the hypothesis that post F-vaccination induces diversification of VH4-encoded BCRs in germinal centers. Comparison of the vaccine-induced BCR repertoires with clonally related pre and post F-binding BCRs of the healthy blood donor suggested that the vaccine expanded pre/post F cross-reactive MBCs. Interestingly, several vaccine-induced BCRs shared stereotypic VDJ gene junctions with known neutralizing Abs. Once expressed for functional characterization, the selected monoclonal Abs demonstrated the predicted neutralization activities in plaque reduction neutralization assays indicating that the post F-vaccine induced expansion of neutralizing BCRs.  相似文献   
5.

Objective

Arch obstruction after the Norwood procedure is common and contributes to mortality. We determined the prevalence, associated factors, and practice variability of arch reintervention and assessed whether arch reintervention is associated with mortality.

Methods

From 2005 to 2017, 593 neonates in the Congenital Heart Surgeons' Society Critical Left Heart Obstruction cohort underwent a Norwood procedure. Median follow-up was 3.7 years. Multivariable parametric models, including a modulated renewal analysis, were performed.

Results

Of the 593 neonates, 146 (25%) underwent 218 reinterventions for arch obstruction after the Norwood procedure: catheter-based (n = 168) or surgical (n = 50) at a median age of 4.3 months (quartile 1-quartile 3, 2.6-5.7). Interdigitation of the distal aortic anastomosis was protective against arch reintervention. Development of ≥ moderate tricuspid valve regurgitation and right ventricular dysfunction at any point was associated with arch reintervention. Nonsignificant variables for arch reintervention included shunt type and preoperative aortic measurements. Surgical arch reintervention was protective against arch reintervention, but transcatheter reintervention was associated with increased reintervention. Arch reintervention was not associated with increased mortality. There was wide institutional variation in incidence of arch reintervention (range, 0-40 reinterventions per 100 years patient follow-up) and in preintervention gradient (range, 0-64 mm Hg).

Conclusions

Interdigitation of the distal aortic anastomosis during the Norwood procedure decreased the risk of arch reintervention. Surgical arch reintervention is more definitive than transcatheter. Arch reintervention after the Norwood procedure is not associated with increased mortality. Serial surveillance for arch obstruction, integrated with changes in right ventricular function and tricuspid valve regurgitation, is recommended after the Norwood procedure to improve outcomes.  相似文献   
6.
《Drug discovery today》2022,27(6):1733-1742
Compounds that exhibit assay interference or undesirable mechanisms of bioactivity are routinely encountered in assays at various stages of drug discovery. We observed that assays for the investigation of thiol-reactive and redox-active compounds have not been collected in a comprehensive review. Here, we review these assays and subject them to experimental optimization to improve their reliability. We demonstrate the usefulness of our assay cascade by assaying a library of bioactive compounds, chemical probes, and a set of approved drugs. These high-throughput assays should complement the array of wet-lab and in silico assays during the initial stages of hit discovery campaigns to pursue only hit compounds with tractable mechanisms of action.  相似文献   
7.
BackgroundThe growing enthusiasm for the use of reverse shoulder arthroplasty (RSA) in the treatment of primary glenohumeral osteoarthritis (GHOA) with an intact rotator cuff is based on data derived from single-center studies with limited generalizability and follow-up. This study compared patient-reported outcomes (PROs) between RSA and total shoulder arthroplasty (TSA) for the treatment of primary GHOA with up to 5-year follow-up and examined temporal trends in the treatment of GHOA between 2012 and 2021.MethodsA retrospective review was performed on patients with primary GHOA undergoing primary arthroplasty surgery from the Surgical Outcomes System global registry between 2012 and 2021. PROs including the American Shoulder and Elbow Surgeons (ASES) score, Single Assessment Numeric Evaluation (SANE) score, and visual analog scale (VAS) for pain were compared between RSA and TSA at 1, 2, and 5 years postoperatively.ResultsA total of 4451 patients were included, with 2693 (60.5%) undergoing TSA and 1758 (39.5%) undergoing RSA. Both RSA and TSA provided clinically excellent outcomes at 1 year postoperatively (ASES: 80.8 ± 17.9 vs. 85.9 ± 15.2, respectively; SANE: 74.8 ± 24.7 vs. 79.5 ± 22.9; VAS pain: 1.3 ± 2.0 vs. 1.1 ± 1.7; all P < .05) that were maintained at 2 years (ASES: 81.3 ± 19.3 vs. 87.3 ± 14.9; SANE: 74.8 ± 26.2 vs. 79.7 ± 24.7; VAS pain: 1.3 ± 2.1 vs. 1.0 ± 1.6; all P < .05) and 5 years (ASES: 81.7 ± 16.5 vs. 86.9 ± 15.3; SANE: 71.6 ± 28.5 vs. 78.2 ± 25.9; VAS pain: 1.0 ± 1.7 vs. 1.0 ± 1.7; all P < .05), with statistical significance favoring TSA. After controlling for age and sex, there was an adjusted difference of 4.5 units in the ASES score favoring TSA (P = .005) at 5 years postoperatively but no differences in adjusted SANE (P = .745) and VAS pain (P = .332) scores. The use of RSA for GHOA grew considerably over time, from representing only 17% of all replacements performed for GHOA in 2012 to nearly half (47%) in 2021 (P < .001).ConclusionRSA as a treatment for GHOA with an intact rotator cuff seems to yield PROs that are largely clinically equivalent to TSA extending to 5 years postoperatively. The observed statistical significance favoring TSA appears to be of marginal clinical benefit based on established minimal clinically important differences and may be a result of the large sample size. Further research using more granular clinical data and examining differences in range of motion and complications is warranted as it may change the value analysis.  相似文献   
8.
9.
目的:通过检测人绒癌细胞株Be Wo合体化过程中增殖细胞核抗原(proliferating cell nuclear antigen,PCNA)、生存素(Survivin)蛋白表达的变化,探讨滋养细胞合体化后增殖性的变化,为恶性滋养细胞肿瘤,尤其是耐药恶性滋养细胞肿瘤的临床治疗提供新的思路和方法。方法:利用毛喉素(forskolin)诱导Be Wo细胞株融合;应用逆转录聚合酶链反应(RT-PCR)检测促融素(Syncytin)在forskolin作用不同时间的Be Wo细胞株中的表达;应用蛋白质印迹(Western blotting)检测PCNA、Survivin蛋白在forskolin作用不同时间的Be Wo细胞株中的表达;应用噻唑蓝比色分析实验(MTT)法检测forskolin作用不同时间的绒癌细胞株Be Wo的增殖能力。结果:1forskolin作用后的Be Wo细胞株Syncytin基因的表达增强,且随着forskolin作用时间的延长,Syncytin的表达更强,于48 h达到高峰。2forskolin作用后的Be Wo细胞株PCNA、Survivin蛋白的表达降低。3forskolin作用后的Be Wo细胞株的增殖能力下降,且不同作用时间的差异有统计学意义;forskolin作用的时间越长,Be Wo细胞株增殖能力下降越明显。结论:人绒癌细胞株Be Wo合体化后PCNA、Survivin蛋白的表达降低,说明人绒癌细胞株Be Wo合体化后增殖性降低,推测诱导滋养细胞合体化可能对临床治疗恶性滋养细胞肿瘤具有一定作用。  相似文献   
10.
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