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   15056篇
  免费   757篇
  国内免费   73篇
耳鼻咽喉   269篇
儿科学   298篇
妇产科学   316篇
基础医学   2063篇
口腔科学   1617篇
临床医学   871篇
内科学   3391篇
皮肤病学   253篇
神经病学   1238篇
特种医学   280篇
外科学   2221篇
综合类   65篇
一般理论   4篇
预防医学   1181篇
眼科学   347篇
药学   704篇
中国医学   109篇
肿瘤学   659篇
  2024年   6篇
  2023年   106篇
  2022年   250篇
  2021年   583篇
  2020年   330篇
  2019年   426篇
  2018年   536篇
  2017年   285篇
  2016年   365篇
  2015年   540篇
  2014年   743篇
  2013年   830篇
  2012年   1244篇
  2011年   1485篇
  2010年   758篇
  2009年   635篇
  2008年   1107篇
  2007年   1096篇
  2006年   1044篇
  2005年   880篇
  2004年   776篇
  2003年   643篇
  2002年   566篇
  2001年   60篇
  2000年   52篇
  1999年   45篇
  1998年   64篇
  1997年   46篇
  1996年   41篇
  1995年   36篇
  1994年   32篇
  1993年   31篇
  1992年   24篇
  1991年   18篇
  1990年   11篇
  1989年   15篇
  1988年   9篇
  1987年   12篇
  1986年   10篇
  1985年   14篇
  1984年   14篇
  1983年   16篇
  1982年   8篇
  1981年   7篇
  1980年   12篇
  1979年   7篇
  1978年   7篇
  1977年   9篇
  1975年   4篇
  1971年   5篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
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   
3.
4.
Die Anaesthesiologie - Simulationstraining ist für die Notfallmedizin unverzichtbar, insbesondere in Hinsicht auf eine verbesserte Patientensicherheit. Methoden und Technologien umfassen ein...  相似文献   
5.
6.
7.
8.
Age-related bone loss has been associated with high levels of marrow adipogenesis. Estrogens (E2) are known to regulate the differentiation of marrow precursors into osteoblasts, however, their role in bone marrow adipogenesis remain unknown. E2 regulate adipocyte differentiation in subcutaneous and visceral fat through interaction with other nuclear receptors. This interaction has not been assessed in bone marrow adipocytes in vivo. In this study, we compared two groups of animals, young and old, after either oophorectomy (OVX) or oophorectomy plus E2 (OVX + E2) replacement. We found that absence of E2 was associated with higher levels of PPARγ and lower levels of Sirt1 most significantly in the old group. In addition, old mice responded better to E2 replacement in terms of reducing adipogenesis and PPARγ expression as well as increasing levels of Sirt1 expression. Our findings represent a new understanding of the role of E2 in age-related bone loss, which could be mediated through the regulation of Sirt1 expression within the bone marrow. In addition, this evidence suggests that old individuals may show a better response to E2 administration in terms of reverting the high levels of marrow fat seen in age-related bone loss.  相似文献   
9.
10.
Black-pigmented anaerobic rods such as Prevotella spp. and Porphyromonas spp. are involved in the etiology and perpetuation of endodontic infections. The aim of this study was to evaluate the prevalence of these species in chronic endodontic infections by using culture and polymerase chain reaction (PCR) techniques. Samples of 100 patients with root canals displaying chronic endodontic infections were obtained by sterilized paper points. Bacterial identification was performed by using culture and PCR techniques. By culture, in 33% of the samples, P. intermedia-P. nigrescens (75.8%), P. gingivalis (27.3%), and P. endodontalis (9.1%) were identified, and by PCR 60% of the samples harbored P. nigrescens (43.3%), P. gingivalis (43.3%), P. intermedia (31.7%), and P. endodontalis (23.3%). The presence of these black-pigmented anaerobic rods alone or in association in chronic endodontic infections seems to be frequent. PCR is a very sensitive technique for detecting DNA from bacterial cells. Culturing is only able to reveal living bacteria and is less sensitive for the identification of low numbers of bacterial cells.  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