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   2403919篇
  免费   181828篇
  国内免费   4898篇
耳鼻咽喉   33513篇
儿科学   79813篇
妇产科学   69250篇
基础医学   346268篇
口腔科学   66877篇
临床医学   212915篇
内科学   471243篇
皮肤病学   53745篇
神经病学   192747篇
特种医学   92422篇
外国民族医学   794篇
外科学   364230篇
综合类   54267篇
现状与发展   4篇
一般理论   749篇
预防医学   185326篇
眼科学   55193篇
药学   176181篇
  2篇
中国医学   5210篇
肿瘤学   129896篇
  2018年   25369篇
  2017年   19267篇
  2016年   21807篇
  2015年   24713篇
  2014年   34601篇
  2013年   51998篇
  2012年   70765篇
  2011年   75423篇
  2010年   44545篇
  2009年   42250篇
  2008年   71083篇
  2007年   76016篇
  2006年   77006篇
  2005年   74920篇
  2004年   72016篇
  2003年   69069篇
  2002年   67523篇
  2001年   113437篇
  2000年   116177篇
  1999年   97541篇
  1998年   27906篇
  1997年   25124篇
  1996年   25254篇
  1995年   23978篇
  1994年   22069篇
  1993年   20727篇
  1992年   75950篇
  1991年   73633篇
  1990年   71774篇
  1989年   69187篇
  1988年   63899篇
  1987年   62630篇
  1986年   59114篇
  1985年   56436篇
  1984年   42606篇
  1983年   36566篇
  1982年   22008篇
  1981年   19586篇
  1979年   39023篇
  1978年   27633篇
  1977年   23339篇
  1976年   22166篇
  1975年   23647篇
  1974年   28131篇
  1973年   27126篇
  1972年   25635篇
  1971年   23583篇
  1970年   22214篇
  1969年   21028篇
  1968年   19779篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
21.
Objective: Polyunsaturated fatty acids n-3 (PUFA n-3) have shown effects in reducing tumor growth, in particular eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) abundantly present in fish oil (FO). When these fatty acids are provided in the diet, they alter the functions of the cells, particularly in tumor and immune cells. However, the effects of α-linolenic fatty acid (ALA), which is the precursor of EPA and DHA, are controversial. Thus, our objective was to test the effect of this parental fatty acid. Methods: Non-tumor-bearing and tumor-bearing Wistar rats (70 days) were supplemented with 1 g/kg body weight of FO or Oro Inca® (OI) oil (rich in ALA). Immune cells function, proliferation, cytokine production, and subpopulation profile were evaluated. Results: We have shown that innate immune cells enhanced phagocytosis capacity, and increased processing and elimination of antigens. Moreover, there was a decrease in production of pro-inflammatory cytokines (tumor necrosis factor-alpha (TNF-α) and interleukin 6 (IL-6)) by macrophages. Lymphocytes showed decreased proliferation capacity, increased cluster of differentiation 8 (CD8+) subpopulation, and increased TNF-α production. Conclusions: Oil rich in ALA caused similar immune modulation in cancer when compared with FO.  相似文献   
22.
23.
24.
DNA methylation at CpG dinucleotides is an important epigenetic regulator common to virtually all mammalian cell types, but recent evidence indicates that during early postnatal development neuronal genomes also accumulate uniquely high levels of two alternative forms of methylation, non-CpG methylation and hydroxymethylation. Here we discuss the distinct landscape of DNA methylation in neurons, how it is established, and how it might affect the binding and function of protein readers of DNA methylation. We review studies of one critical reader of DNA methylation in the brain, the Rett syndrome protein methyl CpG-binding protein 2 (MeCP2), and discuss how differential binding affinity of MeCP2 for non-CpG and hydroxymethylation may affect the function of this methyl-binding protein in the nervous system.  相似文献   
25.
26.
27.
Abstract

Objective: To understand the origin of extremely high gonadotropin levels in a perimenopausal woman.

Methods: A 52-year-old woman with a 2?months of amenorrhea followed spontaneous menstrual cycles recovery was referred to our outpatient clinic with elevated follicle-stimulating hormone (FSH, 483 mUI/ml), luteinizing hormone (LH, 475 mUI/ml) and prolactin (PRL, 173?ng/ml). She was known to take levosulpiride. The gonadotropin levels did not fit with the clinical features.

Results: A gonadotroph tumor was ruled out. Further analysis confirmed constantly high FSH, LH and PRL levels. The measurements were repeated using different analytical platforms with different results. After serial dilutions, nonlinearity was present suggesting an immunoassay interference. After post-polyethylene glycol recovery, hormone levels appeared in the normal range. Anti-goat antibodies were recognized in the serum of the patient.

Conclusions: This case report shows a case of falsely abnormal high gonadotropin and PRL levels in a woman during menopause transition. In the clinical practice the evaluation of gonadotropin profile is not recommended at this age, but the abnormal levels stimulated further evaluation. An interference in the assay due to anti-goat antibodies resulted in abnormally high level of FSH and LH. A strict collaboration between clinicians and the laboratory is needed, when laboratory findings do not correspond to clinical findings.  相似文献   
28.
29.
30.
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