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   21550篇
  免费   1915篇
  国内免费   1478篇
耳鼻咽喉   127篇
儿科学   218篇
妇产科学   196篇
基础医学   2659篇
口腔科学   404篇
临床医学   3041篇
内科学   3122篇
皮肤病学   222篇
神经病学   1129篇
特种医学   731篇
外国民族医学   13篇
外科学   2116篇
综合类   3970篇
现状与发展   5篇
预防医学   1099篇
眼科学   563篇
药学   2307篇
  21篇
中国医学   1192篇
肿瘤学   1808篇
  2024年   79篇
  2023年   410篇
  2022年   965篇
  2021年   1170篇
  2020年   898篇
  2019年   716篇
  2018年   809篇
  2017年   692篇
  2016年   698篇
  2015年   1058篇
  2014年   1278篇
  2013年   1077篇
  2012年   1609篇
  2011年   1769篇
  2010年   1031篇
  2009年   804篇
  2008年   1075篇
  2007年   1038篇
  2006年   1086篇
  2005年   1054篇
  2004年   698篇
  2003年   631篇
  2002年   545篇
  2001年   484篇
  2000年   508篇
  1999年   517篇
  1998年   308篇
  1997年   302篇
  1996年   209篇
  1995年   206篇
  1994年   219篇
  1993年   116篇
  1992年   131篇
  1991年   127篇
  1990年   126篇
  1989年   93篇
  1988年   90篇
  1987年   80篇
  1986年   67篇
  1985年   59篇
  1984年   27篇
  1983年   15篇
  1982年   16篇
  1981年   16篇
  1980年   3篇
  1979年   18篇
  1978年   3篇
  1977年   2篇
  1976年   4篇
  1974年   3篇
排序方式: 共有10000条查询结果,搜索用时 585 毫秒
91.
PURPOSEA large number of studies have suggested the practicability and predictability of immediate implant function, but few studies have reported marginal bone level changes during sequential loading periods. The purpose of this study was to evaluate the marginal bone remodeling of immediately loaded self-tapping implants both at each time point and during each loading period between two time points.MATERIALS AND METHODSThe patients included in this retrospective study were treated with immediately loaded NobelSpeedy Replace implants between August 2008 and July 2009. Differences in the marginal bone level (MBL) at each time point and the marginal bone level change (ΔMBL) between two time points were analyzed with Bonferroni correction (P < .05).RESULTSOverall, 24 patients (mean age, 47.3 ± 12.8 years) with 42 immediately loaded implants and a median follow-up of 6.5 years (IQR, 67.8 months) were included. The cumulative survival rate after 10 - 12 years was 95.2%. Continuous but slow marginal bone loss was observed during long-term follow-up. MBL at both 7.5 years and 11 years was significantly lower than that at loading, 6 months, 2 years and 4 years (P < .05). No bone loss difference was found in any period before 4 years of follow up (P > .05). The loading period of 4 years to 7.5 years showed the largest ΔMBL compared to those of other time periods (P < .05).CONCLUSIONSlight bone loss occurred continuously, and more radical changes of marginal bone can be observed during the period of 4-7.5 years. Thus, long-term effective follow-up of immediately loaded implants is needed.  相似文献   
92.
Background:In-stent restenosis (ISR) caused by vascular remodeling after percutaneous coronary intervention limits the long-term efficacy of this method. Salvianolate injection is now widely used in the clinical treatment of ISR. However, there is no systematic review or meta-analysis to evaluate the effects of Salvianolate injection on ISR.Methods:We will search articles in 8 electronic databases, including the Cochrane Central Register of Controlled Trials, PubMed, Embase, the Web of Science, China National Knowledge Infrastructure, the Chinese Biomedical Literature Database, Wanfang Database, and the Chinese Scientific Journal Database for randomized controlled trials of ISR treated by Salvianolate injection from their inception to February 27, 2022. The primary outcome measure will be the restenosis rate. The data meeting the inclusion criteria were analyzed by RevMan V.5.4 software. Two authors evaluated the study using the Cochrane collaborative risk bias tool. We will use a scoring method to assess the overall evidence supporting the main results.Results:This study will analyze the clinical effectiveness of Salvianolate injection in the treatment of ISR.Conclusion:The findings of this systematic review will provide evidence to evaluate the effectiveness of Salvianolate injection for the treatment of ISR.INPLASY registration number:INPLASY202220117.  相似文献   
93.
IntroductionRapid and accurate pathogen identification is essential for the treatment of pneumonia. Metagenomic next‐generation sequencing (mNGS) is a newly developed technology to obtain microbial nucleic acid sequence information quickly, efficiently, and without bias.MethodsWe performed shotgun metagenomic next‐generation sequencing (mNGS) of bronchoalveolar lavage fluid (BALF) for pathogen identification in pneumonia in a prospective study with 138 patients from a single center. We compared the results of mNGS with standard methods including culture, staining, and targeted PCR and evaluated the clinical applicability of mNGS.ResultsMost of the patients (128/138, 92.75%) were cured or improved. One patient (1/138, 0.72%) died because of acute gastrointestinal bleeding, and 9 patients (9/138, 6.52%) showed no improvement. mNGS identified more bacteria (53 versus 27), fewer fungi (8 versus 31), and more viruses (16 versus 1) than standard methods. In total, treatment in 34 out of 138 cases (24.64%) was adjusted and optimized because of mNGS results. Positive mNGS results contributed to a definitive diagnosis in 23 cases (16.67%), which helped guide treatment decision by either adjusting the antibiotics without de‐escalation or continuing the empirical treatment. mNGS also confirmed no active infection in 11 cases (7.97%) allowed for antibiotic de‐escalation.ConclusionThis prospective clinical study evaluated the clinical utility of mNGS for the diagnosis of pneumonia and showed that mNGS of BALF provides valuable information for effective treatment.  相似文献   
94.
目的测定正常中国人群红细胞儿茶酚氧位甲基转移酶(COMT)活性浓度值,为研究COMT活性变化在疾病诊断中的应用提供依据。方法采用高效液相色谱法测定279名正常健康人(其中男性134例,女性145例)红细胞中COMT的活性浓度,用SPSS统计软件对性别间测定结果进行检验比较。结果男性和女性红细胞中COMT活性浓度分别为:(16.5±7.4)、(15.5±5.3)nmol.mL RBC-1.h-1。活性频率分布男性在6.0~37.4nmol.mL RBC-1.h-1,女性为5.4~37.2 nmol.mL RBC-1.h-1,男女之间COMT活性浓度的差异无统计学意义(P>0.05)。结论本法灵敏,简便,准确,重复性好,且测定结果与国外一些报道一致,适用于临床应用测定研究。本结果可作为中国健康人红细胞COMT活性正常值及今后研究的重要参考数据。  相似文献   
95.
A new drug-targeting system for CD13+ tumors has been developed, based on ultrasound-sensitive nanobubbles (NBs) and cell-permeable peptides (CPPs). Here, the CPP-doxorubicin conjugate (CPP-DOX) was entrapped in the asparagine–glycine–arginine (NGR) peptide modified NB (CPP-DOX/NGR-NB) and the penetration of CPP-DOX was temporally masked; local ultrasound stimulation could trigger the CPP-DOX release from NB and activate its penetration. The CPP-DOX/NGR-NBs had particle sizes of about 200?nm and drug entrapment efficiency larger than 90%. In vitro release results showed that over 85% of the encapsulated DOX or CPP-DOX would release from NBs in the presence of ultrasound, while less than 1.5% of that (30?min) without ultrasound. Cell experiments showed the higher cellular CPP-DOX uptake of CPP-DOX/NGR-NB among the various NB formulations in Human fibrosarcoma cells (HT-1080, CD13+). The CPP-DOX/NGR-NB with ultrasound treatment exhibited an increased cytotoxic activity than the one without ultrasound. In nude mice xenograft of HT-1080 cells, CPP-DOX/NGR-NB with ultrasound showed a higher tumor inhibition effect (3.1% of T/C%, day 24), longer median survival time (50 days) and excellent body safety compared with the normal DOX injection group. These results indicate that the constructed vesicle would be a promising drug delivery system for specific cancer treatment.  相似文献   
96.
The possibility of using commercial bayberry tannin (BT) from a Chinese source as a cross-linker and functional additive to develop soybean protein isolate (SPI)-based films was explored in this study by using the solvent casting method. In particular, the impacts of BT loading on the tensile strength, microstructure, thermal stability, water resistance and antioxidant capacity were fully investigated. The results reveal that SPI incorporated with BT yielded a phenolic–protein hybrid whose relevant films exhibited an improvement in tensile strength of around two times greater compared with native SPI as a result of the formed interactions and covalent cross-links, which could be proven using FTIR spectroscopy. The introduction of BT also led to the compact microstructure of SPI–BT films and enhanced the thermal stability, while the water vapor permeability was reduced compared with the control SPI film, especially at high loading content of tannin. Additionally, the use of BT significantly promoted the antioxidant capacity of the SPI-based films according to DPPH radical scavenging assay results. On this basis, Chinese bayberry tannin is considered a promising natural cross-linker and multifunctional additive that can be dedicated to developing protein-derived films with antioxidant activity for food packaging applications.  相似文献   
97.
目的 了解鼓室硬化和非鼓室硬化中耳炎患者在抗氧化物质超氧化物歧化酶(superoxide dismutase,SOD)、过氧化氢酶(catalnse,CAT)活性及过氧化反应产物丙二醛(malondialdehyde,MDA)浓度方面的差异,以进一步探讨鼓室硬化形成的机制.方法 回顾分析56例(56耳)中耳炎、中耳炎后遗症手术患者资料,分成两组:鼓室硬化组26耳,非鼓室硬化组30耳.测定所有患者血浆、红细胞中SOD、CAT活力及血浆、中耳组织中MDA浓度.结果 分析用秩和检验及相关分析.结果 两组血浆中MDA含量差异无统计学意义.鼓室硬化组中耳组织中MDA含量较高,差异有统计学意义(P<0.05).两组红细胞中SOD和CAT活力差异无统计学意义.鼓室硬化组血浆中的SOD和CAT活力较非鼓室硬化组低.差异有统计学意义.鼓室硬化组术前的听力平均值与其各检测项目所测得的MDA、SOD、CAT值均不存在相关(P>0.05).结论 鼓室硬化患者可能存在局部氧自由基浓度增高和抗氧化物质活性降低的情况.局部氧自由基浓度增高,血液抗氧化物质无法进入中耳组织,可能是形成鼓室硬化的病理基础.  相似文献   
98.
Objective: The mainstay treatment of esophageal squamous cell carcinoma(ESCC) involves chemotherapy and immunotherapy. However, alternative therapies are required for patients who are refractory or intolerant to existing therapies.Methods: In this single-arm, multicenter, open-label phase Ib study, 30 patients received an intravenous infusion of SCT200, an antiepidermal growth factor receptor(EGFR) monoclonal antibody, 6.0 mg/kg once a week for 6 weeks, followed by 8.0 mg/kg once every 2 weeks u...  相似文献   
99.
The periosteum, a highly vascularized thin tissue, has excellent osteogenic and bone regenerative abilities. The generation of periosteum-mimicking tissue has become a novel strategy for bone defect repair and regeneration, especially in critical-sized bone defects caused by trauma and bone tumor resection. Here, we utilized a bone morphogenetic protein-2(BMP-2)-loaded scaffold to create periosteum-like tissue(PT) in vivo, mimicking the mesenchymal condensation during native long bone developmen...  相似文献   
100.
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