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   8843篇
  免费   765篇
  国内免费   309篇
耳鼻咽喉   39篇
儿科学   77篇
妇产科学   66篇
基础医学   839篇
口腔科学   175篇
临床医学   1187篇
内科学   1115篇
皮肤病学   97篇
神经病学   674篇
特种医学   256篇
外科学   593篇
综合类   936篇
一般理论   1篇
预防医学   1397篇
眼科学   91篇
药学   1300篇
  7篇
中国医学   692篇
肿瘤学   375篇
  2024年   20篇
  2023年   155篇
  2022年   275篇
  2021年   349篇
  2020年   321篇
  2019年   382篇
  2018年   325篇
  2017年   330篇
  2016年   315篇
  2015年   303篇
  2014年   598篇
  2013年   841篇
  2012年   524篇
  2011年   546篇
  2010年   394篇
  2009年   383篇
  2008年   422篇
  2007年   416篇
  2006年   381篇
  2005年   302篇
  2004年   255篇
  2003年   205篇
  2002年   179篇
  2001年   174篇
  2000年   149篇
  1999年   101篇
  1998年   125篇
  1997年   115篇
  1996年   90篇
  1995年   81篇
  1994年   78篇
  1993年   92篇
  1992年   68篇
  1991年   61篇
  1990年   51篇
  1989年   31篇
  1988年   40篇
  1987年   32篇
  1986年   30篇
  1985年   50篇
  1984年   43篇
  1983年   40篇
  1982年   38篇
  1981年   29篇
  1980年   27篇
  1979年   32篇
  1978年   21篇
  1977年   21篇
  1976年   27篇
  1975年   17篇
排序方式: 共有9917条查询结果,搜索用时 15 毫秒
1.
内生菌由细菌、真菌、古菌和原生生物组成,它们生活在植物的活体组织中,具有丰富的次级代谢产物多样性。人参内生菌在人参的生长发育、次级代谢产物的生成和环境适应等方面均有重要的促进作用,对人参的产量和品质有较大影响。随着人们在微生物领域研究的深入,高通量测序技术已经成为研究植物内生菌的重要方法。文章主要从人参内生菌分离与鉴定研究方法、人参内生菌的多样性、人参内生菌及其次级代谢产物的活性、人参内生菌对宿主的影响等4个方面对人参内生菌近年来的研究进展进行讨论,并对其发展方向提出展望,以期为药用植物内生菌研究和品质改良提供新思路、新方法。  相似文献   
2.
3.
4.
5.
The Poisson-Nernst-Planck (PNP) system is a widely accepted model for simulation of ionic channels. In this paper, we design, analyze, and numerically validate a second order unconditional positivity-preserving scheme for solving a reduced PNP system, which can well approximate the three dimensional ion channel problem. Positivity of numerical solutions is proven to hold true independent of the size of time steps and the choice of the Poisson solver. The scheme is easy to implement without resorting to any iteration method. Several numerical examples further confirm the positivity-preserving property, and demonstrate the accuracy, efficiency, and robustness of the proposed scheme, as well as the fast approach to steady states.  相似文献   
6.
Objective The present study aims to investigate the concentrations of Hg and its aspects methyl mercury(Me-Hg) and inorganic mercury(I-Hg) in the biological samples(BSs) of fluorescent lamp industries workers(FLIWs).Methodology Different BSs including red blood cells(RBCs),plasma,urine,hair and nails were collected from the workers exposed to Hg and unexposed persons were selected as control group to measure both the T-Hg concentration as well as its species in different biological samples through quantitative analysis.Health data was collected through questionnaire survey.Results The mean concentrations of T-Hg(31.9 μg/L),Me-Hg(27.7 μg/L),and I-Hg(5.36 μg/L) in RBCs were found significantly(P 0.001) higher among the workers(n = 40) as compared to the control group(n = 40).Similarly the mean Hg concentrations in plasma,urine,hair and nails were also significantly higher among the workers than the control group.The statistical relation between Hg concentration and demographic characteristics observed that workers experience and fish consumption has increased the Hg concentration while age,weight and smoking found no significant effect on Hg concentration in the BSs.Conclusion The study observed that the workers were highly exposed to high concentration of Hg and they are at a high health risk.  相似文献   
7.
The Local Lymph Node Assay (LLNA) is the most common in vivo regulatory toxicology test for skin sensitisation, quantifying potency as the EC3, the concentration of chemical giving a threefold increase in thymidine uptake in the local lymph node. Existing LLNA data can, along with clinical data, provide useful comparator information on the potency of sensitisers. Understanding of the biological variability of data from LLNA studies is important for those developing non-animal based risk assessment approaches for skin allergy. Here an existing set of 94 EC3 values for 12 chemicals, all tested at least three times in the same vehicle have been analysed by calculating standard deviations (SD) for logEC3 values. The SDs range from 0.08 to 0.22. The overall SD for the 94 logEC3 values is 0.147. Thus the 95% confidence limits (2xSD) for LLNA EC3 values are within a factor of 2, comparable to those for physico-chemical measurements such as partition coefficients and solubility. The residual SDs of Quantitative Mechanistic Models (QMMs) based on physical organic chemistry parameters are similar to the overall SD of the LLNA, indicating that QMMs of this type are unlikely to be bettered for predictive accuracy.  相似文献   
8.
目的:建立大黄特征化学成分和抗氧化活性相关联的二维指纹图谱,研究大黄抗氧化活性物质。方法:利用高效液相多检测器联用的抗氧化活性成分在线检测体系,对大黄中化学成分进行检测,共鉴定出大黄中化学成分15种;其中8种具有抗氧化活性;然后采用清除效率为指标对各活性成分的抗氧化活性进行评价。结果:结果发现化合物葡萄糖紫丁香酸、腺嘌呤、没食子酸、儿茶素或表儿茶素、双花母草素、2-O-桂皮酰-没食子酰葡萄糖等具有较强的清除ABTS·+的活性,而蒽醌类成分对ABTS·+的清除作用较弱。结论:采用HPLC-ABTS-DAD-Q-TOF/MS对大黄中的抗氧化活性成分进行快速分析鉴定,初步阐明大黄在抗氧化环节起作用的效应物质。  相似文献   
9.

Background

The ZOE-50 (NCT01165177) and ZOE-70 (NCT01165229) phase 3 clinical trials showed that the adjuvanted recombinant zoster vaccine (RZV) was ≥90% efficacious in preventing herpes zoster in adults. Here we present a comprehensive overview of the safety data from these studies.

Methods

Adults aged ≥50 (ZOE-50) and ≥70 (ZOE-70) years were randomly vaccinated with RZV or placebo. Safety analyses were performed on the pooled total vaccinated cohort, consisting of participants receiving at least one dose of RZV or placebo. Solicited and unsolicited adverse events (AEs) were collected for 7 and 30?days after each vaccination, respectively. Serious AEs (SAEs) were collected from the first vaccination until 12?months post-last dose. Fatal AEs, vaccination-related SAEs, and potential immune-mediated diseases (pIMDs) were collected during the entire study period.

Results

Safety was evaluated in 14,645 RZV and 14,660 placebo recipients. More RZV than placebo recipients reported unsolicited AEs (50.5% versus 32.0%); the difference was driven by transient injection site and solicited systemic reactions that were generally seen in the first week post-vaccination. The occurrence of overall SAEs (RZV: 10.1%; Placebo: 10.4%), fatal AEs (RZV: 4.3%; Placebo: 4.6%), and pIMDs (RZV: 1.2%; Placebo: 1.4%) was balanced between groups. The occurrence of possible exacerbations of pIMDs was rare and similar between groups. Overall, except for the expected local and systemic symptoms, the safety results were comparable between the RZV and Placebo groups irrespective of participant age, gender, or race.

Conclusions

No safety concerns arose, supporting the favorable benefit-risk profile of RZV.  相似文献   
10.
Klinefelter syndrome (KS) (47,XXY) is the most common aneuploidy (1/650) of sexual chromosome among male (0,1 à 0,2 % of male population) (Hong and Reiss, 2014). Because its large physical phenotypic variability (high tall, sparse hairiness, gynecomastia), this syndrome is largely underdiagnosed (less than 25 % of affected persons) (Samango-Sprouse et al., 2018). Nevertheless, cognitive variability is smaller. Normal to low average total IQ, low verbal IQ, social problems and high levels of psychiatric comorbidities including early aggressiveness are commonly described (Hong and Reiss, 2014). In Denmark, higher risks of committing sexual crime and arson (compared to criminal controls) was recently reported (Stochholm et al., 2012). Quite a few clinically relevant cases reports scattered in the literature, suggests the presence of a pattern of a specific subtype of KS inpatients among forensic population (Bénézech, 1975). However, very few studies provide quantitative or qualitative pertaining to robust results. KS well-documented neurobiological (van Rijn, 2018) (e.g. low levels of testosterone), neuropsychological (Bénézech, 1975; Hong and Reiss, 2014; Samango-Sprouse et al., 2018; Savic, 2012; Seara-Cardoso et al., 2016; Senon, 2005; Stochholm et al., 2012; van Rijn, 2018; van Rijn et al., 2008; van Rijn et al., 2018; van Rijn et al., 2014; van Rijn et al., 2012) [29] (e.g. alterations of both complex cerebral — attention, empathy — and behavioral regulation functions - inhibition, mental flexibility, emotional response modulation, control of own actions) and neuroanatomical (Hong and Reiss, 2014; Itti et al., 2003; Savic, 2012; van Rijn et al., 2008; van Rijn et al., 2012) [29] (e.g. limbic system and temporal lobe abnormal volume, hemispheric specialization shortcoming) features may be helpful to understand comorbid symptoms psychopathology. Numbers of recent studies conduct on KS pediatric or adult population provide interesting results on conduct, anxiety, psychotic and autism spectrum disorders. In addition, some authors use genetic and epigenetic specific features of sex chromosome aneuploidies (e.g. X genes neurodevelopmental role; imprinting) in order to clarify genotype-phenotype links of comorbid symptoms (Bruining et al., 2011; Zitzmann et al., 2004;). With Belgian colleagues from the Social Defense Research Center (CRDS, Tournai, Belgium), we are currently recruiting KS inpatients from security hospitals or psychiatric units in Belgium and France. We aim to assess psychopathic traits with the Psychopathy Checklist Revised (PCL-R, Hare) (Hare, 2003). Our first results concerning 3 KS males outline that PCL-R is useful for the characterization of clinical phenotype among KS forensic sample. While three of them present psychopathic traits, two of them present categorical double diagnose “psychopathy-KS” (total PCL-R score > = 30/40 (Delannoy et al., 2017)). Moreover, dimensional analysis support our hypothesis of a higher prevalence of “explosive profile” in comparison to other psychopathic profiles in our sample (Delannoy et al., 2017). The present article summarizes historic background (e.g. “psychopathy” disappearance of mental disorder reference classification schemes, “crime chromosome” (Bénézech, 1975)) and current context argues (e.g. French psychiatrists court experts widely refer to psychopathy concept despite a lack of consensual definition (Senon, 2005), weak knowledge and training of PCL-R and its related biopsychological recent findings (Blair, 2013; de Oliveira-Souza et al., 2008; Dotterer et al., 2017; Glenn and Raine, 2014; Hosking et al., 2017; Korponay et al., 2017; Pham, 1995; Pham, 2005; Raine, 2008; Raine et al., 2003); stigma and discrimination apprehensions of KS and psychopath) that motivate our research project. Finally, we discuss the advantages of our research protocol on KS participants assessed with PCL-R, such as tackling stigma and discrimination, better understanding psychopathology, and clarifying murky interactions of biological, psychological and social factors entangled in the development of these two fascinating troubles.  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