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   49859篇
  免费   3987篇
  国内免费   124篇
耳鼻咽喉   399篇
儿科学   2000篇
妇产科学   1345篇
基础医学   7262篇
口腔科学   1009篇
临床医学   6857篇
内科学   9708篇
皮肤病学   935篇
神经病学   5097篇
特种医学   1134篇
外科学   4430篇
综合类   417篇
一般理论   62篇
预防医学   5992篇
眼科学   722篇
药学   2807篇
  2篇
中国医学   56篇
肿瘤学   3736篇
  2024年   66篇
  2023年   445篇
  2022年   612篇
  2021年   1338篇
  2020年   993篇
  2019年   1475篇
  2018年   1608篇
  2017年   1257篇
  2016年   1406篇
  2015年   1470篇
  2014年   1868篇
  2013年   2776篇
  2012年   3867篇
  2011年   4007篇
  2010年   2170篇
  2009年   1949篇
  2008年   3210篇
  2007年   3323篇
  2006年   3248篇
  2005年   3054篇
  2004年   2957篇
  2003年   2733篇
  2002年   2466篇
  2001年   379篇
  2000年   285篇
  1999年   336篇
  1998年   553篇
  1997年   415篇
  1996年   362篇
  1995年   364篇
  1994年   280篇
  1993年   275篇
  1992年   198篇
  1991年   170篇
  1990年   148篇
  1989年   120篇
  1988年   134篇
  1987年   98篇
  1986年   98篇
  1985年   104篇
  1984年   105篇
  1983年   106篇
  1982年   138篇
  1981年   130篇
  1980年   112篇
  1979年   64篇
  1978年   76篇
  1977年   52篇
  1976年   46篇
  1974年   45篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
The tumor microenvironment consists of tumor, immune, stromal, and inflammatory cells which produce cytokines, growth factors, and adhesion molecules that promote tumor progression and metastasis. Of particular interest in this setting is interleukin-1 (IL-1), a pleiotropic cytokine with numerous roles in both physiological and pathological states. It is known to be up regulated in many tumor types and has been implicated as a factor in tumor progression via the expression of metastatic and angiogenic genes and growth factors. A number of studies have reported that high IL-1 concentrations within the tumor microenvironment are associated with a more virulent tumor phenotype. Solid tumors in which IL-1 has been shown to be up regulated include breast, colon, lung, head and neck cancers, and melanomas, and patients with IL-1 producing tumors have generally bad prognoses. The exact mechanisms by which IL-1 promotes tumor growth remain unclear, though the protein is believed to act via induction of pro-metastatic genes such as matrix metalloproteinases and through the stimulation of adjacent cells to produce angiogenic proteins and growth factors such as VEGF, IL-8, IL-6, TNFα, and TGFβ. The IL-1 receptor antagonist (IL-1ra) is a naturally occurring inhibitor to IL-1 and acts by binding to the IL-1 receptor without activating it. The protein has been shown to decrease tumor growth, angiogenesis, and metastases in murine xenograft models. Our focus in this review is to summarize the known data on the role of IL-1 in tumor progression and metastasis and the use of IL-1 inhibition as a novel therapeutic approach in the treatment of solid organ malignancies.  相似文献   
62.
63.
64.
65.
The choroid plexuses (CPs) form a protective interface between the blood and the ventricular cerebrospinal fluid (CSF). To probe into the pathways by which CPs provide brain protection, we sought to evaluate the efficiency of glutathione conjugation in this barrier as a mechanism to prevent the entry of blood-borne electrophilic, potentially toxic compounds into the CSF, and we investigated the fate of the resulting metabolites. Rat CPs, as well as human CPs from both fetal and adult brains, displayed high glutathione-S-transferase activities. Using an in vitro model of the blood-CSF barrier consisting of choroidal epithelial cells cultured in a two-chambered device, we showed that glutathione conjugation can efficiently prevent the entry of 1-chloro-2,4-dinitrobenzene (CDNB) into the CSF, a model for electrophilic compounds. The duration of this enzymatic protection was set by the concentration of CDNB to which the epithelium was exposed, and this barrier effect was impaired only on severe epithelial intracellular glutathione and cysteine depletion. The conjugate was excreted from the choroidal cells in a polarized manner, mostly at the blood-facing membrane, via a high-capacity transport process, which is not a rate-limiting step in this detoxification pathway, and which may involve transporters of the ATP-binding cassette c(Abcc) and/or solute carrier 21 (Slc21) families. Supplying the choroidal epithelium at the blood-facing membrane with a therapeutically relevant concentration of N-acetylcysteine sustained this neuroprotective effect. Thus, glutathione conjugation at the CP epithelium coupled with the basolateral efflux of the resulting metabolites form an efficient blood-CSF enzymatic barrier, which can be enhanced by pharmacologically increasing glutathione synthesis within the epithelial cells.  相似文献   
66.
Recent years have witnessed increased antipsychotic treatment of children despite limited long‐term safety data in children. In this study, motor side effects associated with the use of antipsychotic drugs in children were examined in a sample of pediatric psychiatric patients. Child and adolescent psychiatric patients receiving antipsychotics (most were on atypicals) for 6 months or longer (n = 118) were compared with antipsychotic‐naïve patients (n = 80) with similar age, sex ratio, and diagnoses. Only 19% of patients on antipsychotics had ever experienced psychotic symptoms. Eleven children (9%) on antipsychotics exhibited dyskinesia, when compared with 0 in the naïve group (P = 0.003, Fisher's exact test). Nine of 62 African–American children (15%) on antipsychotics exhibited dyskinesia, when compared with only 4% (2 of 52) of European–American children (P = 0.003, Fisher's exact test). Children treated with antipsychotic drugs might experience a significant risk of dyskinesia even when treated only with atypical antipsychotics. Ethnicity might also be a risk factor for dyskinesia in children. Side‐effect profile of the atypical antipsychotic drugs in children may be much different than that in adults. © 2007 Movement Disorder Society  相似文献   
67.
Chordoma is a rare tumor, arising from notochord remnants, which usually occurs in the axial skeleton and rarely metastasizes. Although there have been 3 previous reports of metastatic disease to the facial bones from sacrococcygeal chordoma, this is the first to describe spread to the mandible from a vertebral primary chordoma.  相似文献   
68.
69.
BACKGROUND: While Tacrolimus (Tac) and Cyclosporine (Cya) immunosuppression are used after cardiac transplantation (tx), few studies have evaluated their use in pediatric patients. METHODS: We randomized 26 heart transplant recipients (pts) in a prospective, open-label trial to Tac (n = 14) or Cya (n = 12) to compare their efficacy and side-effects. Mean age at tx was 4.2 years for Tac and 5.8 years for Cya. Mean follow-up was 26 months (range: 11-39 months) for Tac and 24 months for Cya (range: 33-13 months). RESULTS: Our data suggest that both regimens are efficacious in the pediatric population. Conversion from Cya to Tac was useful for dealing with persistent rejection, although this sample did not suggest lower incidence of acute cellular rejection in the Tac group. CONCLUSIONS: Further studies are required to establish pharmacokinetic parameters to enhance therapeutic monitoring of these patients to minimize side effects and enhance outcomes.  相似文献   
70.
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