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   36725篇
  免费   3732篇
  国内免费   49篇
耳鼻咽喉   477篇
儿科学   1003篇
妇产科学   743篇
基础医学   5249篇
口腔科学   1370篇
临床医学   4152篇
内科学   7328篇
皮肤病学   409篇
神经病学   2931篇
特种医学   1321篇
外国民族医学   2篇
外科学   4834篇
综合类   1040篇
一般理论   30篇
预防医学   3848篇
眼科学   1006篇
药学   2800篇
  1篇
中国医学   27篇
肿瘤学   1935篇
  2021年   547篇
  2020年   329篇
  2019年   557篇
  2018年   603篇
  2017年   444篇
  2016年   471篇
  2015年   580篇
  2014年   808篇
  2013年   1205篇
  2012年   1669篇
  2011年   1760篇
  2010年   955篇
  2009年   932篇
  2008年   1559篇
  2007年   1652篇
  2006年   1527篇
  2005年   1588篇
  2004年   1448篇
  2003年   1387篇
  2002年   1360篇
  2001年   1098篇
  2000年   1155篇
  1999年   1077篇
  1998年   407篇
  1997年   331篇
  1996年   381篇
  1995年   344篇
  1994年   357篇
  1993年   335篇
  1992年   858篇
  1991年   836篇
  1990年   867篇
  1989年   781篇
  1988年   741篇
  1987年   745篇
  1986年   701篇
  1985年   714篇
  1984年   533篇
  1983年   490篇
  1982年   306篇
  1981年   321篇
  1980年   292篇
  1979年   472篇
  1978年   379篇
  1977年   305篇
  1976年   285篇
  1974年   374篇
  1973年   361篇
  1972年   298篇
  1971年   311篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
During pregnancy the mother must tolerate intra-uterine allogenic fetal tissue. Failure of this tolerance may cause spontaneous abortion. The immunological changes occurring in normal pregnancy are poorly understood. The aim of this study was to investigate the immunological changes occurring in pregnancy. Thirty women in the first trimester; 10 in the second and 10 in the third trimester of pregnancy were studied and compared to age matched non-pregnant controls. In normal pregnancy there was an increase in the total white cell count with no change in the lymphocyte count. There was a fall in total T cell numbers and activated T cell numbers, with no change in helper/inducer or suppressor/cytotoxic T cell numbers. [3H]Thymidine uptake in response to three different mitogens was increased. This implies an increase in potential for the cells to respond to mitogens. There was no change in interleukin-2 receptor levels, suggesting that despite this increased potential there was no general activation of the immune system. A rise in IgM and IgG was found after mitogen stimulation of peripheral blood lymphocytes, suggesting an increase in potential antibody production. These results demonstrate that lymphocytes from pregnant women have an increased potential rather than an increased activity.  相似文献   
102.
Three single-scan (SS) methods are currently available for estimating the local cerebral metabolic rate of glucose (LCMRG) from F-18 deoxyglucose (FDG) positron emission tomography (PET) scan data: SS(SPH), named for Sokoloff, Phelps, and Huang; SS(B), named for Brooks; and SS(H), named for Hutchins and Holden et al. All three of these SS methods make use of prior information in the form of mean values of rate constants from the normal population. We have developed a Bayes estimation (BE) method that uses prior information in the form of rate constant means, variances, and correlations in both the normal and ischemic tissue populations. The BE method selects, based only on the data, whether the LCMRG estimate should be computed using prior information from normal or ischemic tissue. The ability of BE to make this selection gives it an advantage over the other methods. The BE method can be used as a SS method or can use any number of PET scans. We conducted Monte Carlo studies comparing BE as a SS method with the other SS methods, all using a single scan at 60 min. We found SS(H) to be strongly superior to SS(SPH) and SS(B), and we found BE to be definitely superior to SS(H).  相似文献   
103.
Gamma scintigraphy was used in twelve healthy volunteers to establish whether the time of dosing of Liquid Gaviscon relative to a meal influenced its therapeutic action. Indium-113m labelled Liquid Gaviscon was administered to fasted subjects, 30 min after a technetium-99m labelled meal or immediately before ingestion of the meal. The time for 50% of the Gaviscon to empty from the stomach was 0.36 +/- 0.13 h, 3.10 +/- 0.31 h and 0.68 +/- 0.04 h (s.e.m.), respectively. The preparation was found to empty rapidly from the fasted stomach and could not be floated on a meal consumed subsequently. For raft formation to occur, Liquid Gaviscon should be taken 30 min after a meal.  相似文献   
104.
BACKGROUND: Allergic inflammation is characterized by the influx and activation of eosinophils. Cytokines generated by both resident and infiltrating cells are responsible for the initiation and maintenance of this pathogenesis. This study focuses on allergen-induced activation of eosinophil NF-kappaB and generation of granulocyte macrophage-colony stimulating factor (GM-CSF), TNF-alpha, and IL-8. METHODS: Peripheral blood eosinophils were enriched to >99.9% by Percoll gradient sedimentation and negative magnetic affinity chromatography. NF-kappaB activation by 10 microg/mL house dust mite (HDM) extract was demonstrated immunocytochemically using a monoclonal antibody against the active form of NF-kappaB (NF-kappaBa). The authenticity of NF-kappaB was confirmed by Western blot. Cytokine production was assessed both by immuno-staining of eosinophils and by assay of cytokines in the cell supernatant. RESULTS: Activation of peripheral blood eosinophils from atopic, but not non-atopic, donors induced activation of NF-kappaB, which peaked at 4 h and was accompanied by a decline in IkappaB-alpha. The activation of authentic NF-kappaB was confirmed in gel shift assays. Supershift assays showed p65 to be the major subunit of eosinophil NF-kappaB. Immunofluorescent confocal microscopy demonstrated localization of NF-kappaBa to the nucleus. Following activation, cytokine immunoreactivity was seen in a fraction of the eosinophils and cytokines were released into the supernatant. The NF-kappaB inhibitors, calpain inhibitor 1 (10 microm), pentoxifylline (0.5 mm), pyrrolidine dithiocarbamate (PDTC, 10 microm) or gliotoxin (1 pg/mL) reduced the generation of GM-CSF, TNF-alpha and IL-8 in parallel with their inhibition of NF-kappaB. CONCLUSIONS: HDM allergen activates human eosinophil NF-kappaB leading to the production of the cytokines GM-CSF, TNF-alpha and IL-8. We speculate that a role for eosinophil NF-kappaB-dependent cytokines is to act as an autocrine loop augmenting the survival of eosinophils in vivo.  相似文献   
105.
106.
107.
Comfort management is a priority for patients in all settings. Comfort theory provides a foundational and holistic approach to comfort management. This article reviews comfort theory and presents the application of comfort theory in the perianesthesia setting. OBJECTIVES: -Based on the content of the following article, the reader will be able to (1) define comfort; (2) identify comfort interventions; and (3) discuss the importance of a goal for enhanced comfort in patients.  相似文献   
108.
109.
110.
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