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   925篇
  免费   51篇
  国内免费   9篇
耳鼻咽喉   5篇
儿科学   40篇
妇产科学   5篇
基础医学   104篇
口腔科学   44篇
临床医学   93篇
内科学   208篇
皮肤病学   40篇
神经病学   32篇
特种医学   153篇
外国民族医学   1篇
外科学   68篇
综合类   45篇
预防医学   69篇
眼科学   5篇
药学   45篇
中国医学   1篇
肿瘤学   27篇
  2023年   3篇
  2021年   5篇
  2020年   5篇
  2019年   12篇
  2018年   13篇
  2017年   15篇
  2016年   16篇
  2015年   31篇
  2014年   17篇
  2013年   31篇
  2012年   29篇
  2011年   31篇
  2010年   38篇
  2009年   48篇
  2008年   33篇
  2007年   23篇
  2006年   23篇
  2005年   16篇
  2004年   34篇
  2003年   23篇
  2002年   13篇
  2001年   6篇
  2000年   7篇
  1999年   18篇
  1998年   54篇
  1997年   62篇
  1996年   56篇
  1995年   42篇
  1994年   40篇
  1993年   37篇
  1992年   7篇
  1991年   11篇
  1990年   16篇
  1989年   14篇
  1988年   22篇
  1987年   23篇
  1986年   21篇
  1985年   9篇
  1984年   4篇
  1983年   8篇
  1982年   18篇
  1981年   3篇
  1980年   9篇
  1979年   4篇
  1978年   4篇
  1977年   5篇
  1976年   6篇
  1975年   2篇
  1968年   3篇
  1959年   2篇
排序方式: 共有985条查询结果,搜索用时 0 毫秒
981.
BACKGROUND: At present, tens of thousands of United States blood donors who are at low risk for human immunodeficiency virus type 1 (HIV-1) infection are indefinitely deferred. These persons are repeatably reactive for HIV-1 antibody in enzyme immunoassay (EIA) and are indeterminate in Western blot. STUDY DESIGN AND METHODS: To determine the significance and persistence of anti-HIV-1 reactivity in plasma from volunteer blood donors with HIV-1-indeterminate Western blots, 66 donors were retested for HIV-1 antibody by the same manufacturers' EIA and Western blot 5 to 7 years after the initial Western blot. In addition, donors' peripheral blood mononuclear cells were tested by polymerase chain reaction (PCR) for HIV-1 DNA gag sequences. RESULTS: Thirty-five (53%) of 66 donors were still repeatedly reactive for HIV-1 on EIA and indeterminate on Western blot, 23 (35%) were negative on EIA and indeterminate on Western blot, 7 (11%) were negative in EIA and Western blot, and 1 (2%) was repeatedly reactive on EIA and negative on Western blot. Donors with persistently indeterminate Western blots had a band pattern nearly identical to that on the original Western blot. No donor was positive in Western blot, p24 antigen, or PCR testing. No donor had signs or symptoms of HIV-1 infection. CONCLUSION: Long-term follow-up of Western blot-indeterminate blood donors does not reveal evidence of HIV-infection. A mechanism to return these donors to the donor pool should be considered.  相似文献   
982.
The ease of tolerance induction in B lymphocytes from fetal, neonatal, and adult mice was studied in vivo, in a cell transfer system, and in vitro. Three different tolerogens were used: ultracentrifuged BGG, DNP(6)-D-GL, and ultracentrifuged DNP(22)-BGG. Irradiated thymectomized mice were reconstituted with B cells from fetal or neonatal liver or adult spleen or bone marrow. The mice were injected with tolerogen 1 day later. They were given normal thymus cells and challenged with either BGG or DNP(44)-BGG between 4 and 14 days after tolerance induction. With BGG no difference in ease of B-cell tolerance induction was observed in mice reconstituted with B cells from 17-day fetal liver, neonatal liver, 8- day-old spleen, adult spleen, or adult bone marrow. B cells from 14-day fetal donors are relatively resistant to tolerance induction. In contrast, with DNP(6)-D-GL and DNP(22)-BGG B cells from neonatal donors were clearly more susceptible to tolerance induction than were B cells from adult donors. Comparable results were obtained in studies on tolerance induction in vitro. Neonatal B cells were more susceptible than adult B cells to tolerance induction upon culture with DNP(6)-D-GL or DNP(22)-BGG. However, neonatal and adult B cells were identical with respect to ease of tolerance induction in vitro with deaggregated BGG. The results suggest that there are multiple mechanisms for B-cell tolerance induction. Immature B cells appear to be more susceptible to tolerance induction by some mechanisms but not by others. It is suggested that immature B cells are more susceptible to tolerance induction with moderately polyvalent antigens such as hapten-carrier conjugates. With antigens like BGG which do not haverepeated epitopes no difference between mature and fetal B cells in regard to ease of tolerance induction is observed. These observations raise questions about the importance of relative ease of tolerance induction in immature B cells as a mechanism controlling the normal induction of self tolerance.  相似文献   
983.
DNA methylation (DNAm)-based biological age (epigenetic age) has been suggested as a useful biomarker of age-related conditions including type 2 diabetes (T2D), and its newest iterations (GrimAge measurements) have shown early promise. In this study, we explored the association between epigenetic age and incident T2D in the context of their relationships with obesity. A total of 1,057 participants in the Coronary Artery Risk Development in Young Adults (CARDIA) study were included in the current analyses. We stratified the participants into three groups: normal weight, overweight, and obese. A 1-year increase of GrimAge was associated with higher 10-year (study years 15–25) incidence of T2D (odds ratio [OR] 1.06, 95% CI 1.01–1.11). GrimAge acceleration, which represents the deviation of GrimAge from chronological age, was derived from the residuals of a model of GrimAge and chronological age, and any GrimAge acceleration (positive GrimAA: having GrimAge older than chronological age) was associated with significantly higher odds of 10-year incidence of T2D in obese participants (OR 2.57, 95% CI 1.61–4.11). Cumulative obesity was estimated by years since obesity onset, and GrimAge partially mediated the statistical association between cumulative obesity and incident diabetes or prediabetes (proportion mediated = 8.0%). In conclusion, both older and accelerated GrimAge were associated with higher risk of T2D, particularly among obese participants. GrimAge also statistically mediated the associations between cumulative obesity and T2D. Our findings suggest that epigenetic age measurements with DNAm can potentially be used as a risk factor or biomarker associated with T2D development.  相似文献   
984.
本文介绍了一种适合治疗各种类型颈椎病的颈椎保健理疗仪。它是由颈椎按摩装置、热疗装置和颈椎牵引装置构成。治疗颈椎病时,先利用颈椎按摩、热疗装置对颈部进行揉捏推拿、振动按摩、热疗;然后利用牵引装置对椎间小关节紊乱、椎间隙狭窄(椎间盘病变)等疾病进行牵引治疗。  相似文献   
985.
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