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   24780篇
  免费   2198篇
  国内免费   609篇
耳鼻咽喉   64篇
儿科学   342篇
妇产科学   550篇
基础医学   3877篇
口腔科学   447篇
临床医学   2327篇
内科学   2557篇
皮肤病学   292篇
神经病学   1919篇
特种医学   420篇
外国民族医学   1篇
外科学   1448篇
综合类   3491篇
一般理论   7篇
预防医学   4344篇
眼科学   432篇
药学   2447篇
  40篇
中国医学   1629篇
肿瘤学   953篇
  2023年   371篇
  2022年   386篇
  2021年   738篇
  2020年   884篇
  2019年   809篇
  2018年   730篇
  2017年   903篇
  2016年   960篇
  2015年   951篇
  2014年   1408篇
  2013年   1877篇
  2012年   1427篇
  2011年   1501篇
  2010年   1226篇
  2009年   1197篇
  2008年   1256篇
  2007年   1259篇
  2006年   1109篇
  2005年   927篇
  2004年   854篇
  2003年   696篇
  2002年   616篇
  2001年   543篇
  2000年   466篇
  1999年   401篇
  1998年   338篇
  1997年   269篇
  1996年   270篇
  1995年   290篇
  1994年   247篇
  1993年   221篇
  1992年   219篇
  1991年   213篇
  1990年   176篇
  1989年   195篇
  1988年   179篇
  1987年   127篇
  1986年   169篇
  1985年   144篇
  1984年   168篇
  1983年   117篇
  1982年   151篇
  1981年   119篇
  1980年   109篇
  1979年   105篇
  1978年   63篇
  1977年   48篇
  1976年   65篇
  1975年   32篇
  1973年   16篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
We propose a computational model to study the growth and spread of bacterial biofilms on interfaces, as well as the action of antibiotics on them. Bacterial membranes are represented by boundaries immersed in a fluid matrix and subject to interaction forces. Growth, division and death of bacterial cells follow dynamic energy budget rules, in response to variations in environmental concentrations of nutrients, toxicants and substances released by the cells. In this way, we create, destroy and enlarge boundaries, either spherical or rod-like. Appropriate forces represent details of the interaction between cells, and the interaction with the environment. We can investigate geometrical arrangements and the formation of porous structures. Numerical simulations illustrate the evolution of top views and diametral slices of small biofilm seeds, as well as the action of antibiotics. We show that cocktails of antibiotics targeting active and dormant cells can entirely eradicate a biofilm.  相似文献   
2.
IntroductionWe extend previous research to illustrate how individual, interpersonal and neighbourhood factors in a high-density urban setting in Vancouver, Canada, shape social connectedness experiences of community-dwelling older adults during the first wave of the COVID-19 pandemic.MethodsWe conducted 31 semi-structured interviews and collected objective measures of loneliness and social connectedness (surveys).ResultsThree dimensions of the neighbourhood environment influenced social connectedness: (i) interactions with neighbours, (ii) involvement with neighbourhood-based organizations, and (ii) outdoor pedestrian spaces. Seventy-one percent of participants felt a strong sense of belonging to their local community, while 39% were classified as high or extremely lonely.SummaryMany participants leveraged pre-existing social ties to maintain connections during the pandemic. However, volunteer outreach was vital for more isolated older adults. Although many participants felt lonely and isolated at times, the relative ease and accessibility with which they could connect with others in their neighbourhood environment, may have helped mitigate persistent loneliness.ConclusionStrategies that foster social connectedness over the longer term, need to prioritize the needs of older adults who face multiple barriers to equitable social participation.  相似文献   
3.
《Molecular therapy》2022,30(8):2856-2867
  1. Download : Download high-res image (173KB)
  2. Download : Download full-size image
  相似文献   
4.
《Journal of endodontics》2022,48(5):572-596
IntroductionCulture-independent molecular studies have shown a broad spectrum of bacterial taxa that persist after chemomechanical procedures (CMP). Therefore, this study systematically reviewed these reports to explore the prevalence of bacteria in post-instrumentation samples of root canals from permanent teeth, especially of as-yet-uncultivated/difficult-to-culture bacteria.MethodsElectronic databases were searched from 2007 to January 2021. Clinical studies using culture-independent molecular methods to identify species-level taxa before and after CMP were included. Studies were critically appraised using the Joanna Briggs Institute Prevalence Critical Appraisal Checklist and the funnel plot analysis. The meta-analysis was performed on the prevalence of as-yet-uncultivated/difficult-to-culture bacterial taxa using RStudio.ResultsA total of 3781 titles were screened, but only 20 studies were included. The most frequent species in post-instrumentation samples were Streptococcus spp., Leptotrichia buccalis, Fusobacterium nucleatum, and Capnocytophaga ochracea. The detection frequency of some species increased after CMP, including mainly Firmicutes members such as streptococci, Enterococcus faecium, Selenomonas noxia, and Solobacterium moorei. The prevalence (confidence interval) of difficult-to-culture species was as follows: Dialister invisus, 17% (7%–29%); Solobacterium moorei, 14% (8%–23%); Bacteroidaceae [G-1] bacterium HMT 272, 13% (5%–23%); and Filifactor alocis, 11% (3%–23%).ConclusionsThe prevalence of as-yet-uncultivated/difficult-to-culture bacterial taxa in post-instrumentation samples was low. The persistent species belonged mainly to the phylum Firmicutes, and streptococci were the major members. Future larger clinical studies on the composition of the whole bacterial community that persist after CMP are still necessary for a better understanding of bacterial interactions and their clinical significance in the treatment outcome.  相似文献   
5.
急性髓系白血病(acute myeloid leukemia,AML)是常见的髓系原始细胞单克隆性恶性增殖的造血系统疾病,但是其免疫学机制目前尚不清楚。一般认为参与恶性肿瘤免疫反应的细胞包括调节性T细胞(regulatory T cells,Treg)、效应性T细胞(effective T cells,Teff)和B细胞等。B细胞具有活化T细胞、产生抗体等功能,近年发现一群具有免疫调节功能的B细胞(调节性B细胞,regulatory B cells,Breg),能够对Treg、Teff等细胞起调节作用。深入研究Breg细胞在AML的免疫学发病机制有重要意义。因此,本文就Breg细胞在AML中的研究进展进行综述。  相似文献   
6.
In this paper, we propose a high-order accurate discontinuous Galerkin (DG) method for the compressible Euler equations under gravitational fields on unstructured meshes. The scheme preserves a general hydrostatic equilibrium state and provably guarantees the positivity of density and pressure at the same time. Comparing with the work on the well-balanced scheme for Euler equations with gravitation on rectangular meshes, the extension to triangular meshes is conceptually plausible but highly nontrivial. We first introduce a special way to recover the equilibrium state and then design a group of novel variables at the interface of two adjacent cells, which plays an important role in the well-balanced and positivity-preserving properties. One main challenge is that the well-balanced schemes may not have the weak positivity property. In order to achieve the well-balanced and positivity-preserving properties simultaneously while maintaining high-order accuracy, we carefully design DG spatial discretization with well-balanced numerical fluxes and suitable source term approximation. For the ideal gas, we prove that the resulting well-balanced scheme, coupled with strong stability preserving time discretizations, satisfies a weak positivity property. A simple existing limiter can be applied to enforce the positivity-preserving property, without losing high-order accuracy and conservation. Extensive one- and two-dimensional numerical examples demonstrate the desired properties of the proposed scheme, as well as its high resolution and robustness.  相似文献   
7.
《Vaccine》2022,40(6):904-911
BackgroundGSK initiated a Pregnancy Registry in the United States (US) for the reduced-antigen-content tetanus-diphtheria-acellular pertussis (Tdap; Boostrix, GSK) vaccine with the aim to detect and describe pregnancy outcomes in women vaccinated with Boostrix 28 days before estimated conception or during pregnancy.MethodsVoluntary reports of pregnancy exposure to Boostrix received from spontaneous and post-marketing surveillance sources in the US were assessed. Reports were classified as prospective or retrospective based on the knowledge of pregnancy outcomes at the time of reporting. For completeness, reports of exposure to Boostrix or to the Tdap-inactivated poliovirus vaccine (Boostrix-IPV, GSK) reported to the global safety database from countries outside the US were also evaluated.ResultsFrom May 2005 to August 2019, 1517 (1455 prospective and 62 retrospective) pregnancy reports were received in the Boostrix US Pregnancy Registry. Of the prospective reports, 250 had known outcomes: 244 live infants with no apparent birth defects (BDs), three live infants with BDs, and three spontaneous abortions with no apparent BDs. Of the retrospective reports, 55 had known outcomes: 33 live infants with no apparent BDs, 16 live infants with BDs, one spontaneous abortion with no apparent BDs, four stillbirths with no apparent BDs, and one stillbirth with BDs. Cumulatively, 1321 pregnancy reports (1006 for Boostrix; 315 for Boostrix-IPV) were received from countries outside the US. Of these, 163 prospective reports and 551 retrospective reports had known outcomes. Results were in line with those from the Boostrix US Pregnancy Registry.ConclusionsData currently available from the Boostrix US Pregnancy Registry and from countries outside the US suggested that exposure to Boostrix or Boostrix-IPV during pregnancy does not raise safety concerns related to adverse pregnancy outcomes or BDs.  相似文献   
8.
 目的 探讨冲刺间歇训练时两种恢复方式(积极性恢复 vs. 消极性恢复)对士兵运动能力和训练效果的影响。方法 选取18名男性武警士兵完成6组冲刺间歇训练(30 s Wingate全力蹬车试验),间歇期(4 min)分别进行消极性恢复(即在功率自行车上休息)和积极性恢复(以1.1 W/kg负荷继续蹬车),每次Wingate试验时(不包括间歇期)记录峰值功率(PP)、平均功率(MP)、疲劳指数(FI)、总做功(TW)和心率(HR)等参数。结果 与消极性恢复比较,积极性恢复PP在第2次Wingate试验时降低(P<0.05),MP和HR在第4~6次Wingate试验时升高,差异均有统计学意义(P<0.05),FI和TW差异无统计学意义(P>0.05)。结论 积极性恢复可提高冲刺间歇训练后期的训练效果, 士兵应根据训练方案选择合理的恢复方式。  相似文献   
9.
2021年,免疫学在基础理论研究和转化应用方面取得诸多突破性进展,深化了对免疫应答及其调控基本原理的认识,并为揭示免疫相关疾病发病机制和疾病防治提供了科学依据及方法策略。基础理论方面,天然免疫识别与炎症应答、细胞死亡的分子调控机制和免疫学效应以及神经系统与免疫系统的交叉调控等领域取得诸多创新性成果;临床转化应用方面,新冠肺炎和肿瘤等重大疾病发生发展的免疫学原理和防治手段方面取得多项进展。本文将回顾总结2021年国内外免疫学研究代表性重要进展,共同展望某些前沿方向和未来挑战。  相似文献   
10.
This commentary looks at the process of conducting a systematic review of surveys and validated questionnaires. Surveys and other questionnaire style tools are often used in the field of social and administrative pharmacy, to capture beliefs, attitudes and experiences of patients and healthcare professionals (including pharmacists). Currently, there is little guidance available on how to conduct a systematic review of these types of studies. Considerations related to the process of a systematic review are highlighted, including identification of articles, data extraction, assessing quality of articles and synthesis and analysis of data.  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