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   5645篇
  免费   437篇
  国内免费   187篇
耳鼻咽喉   35篇
儿科学   160篇
妇产科学   58篇
基础医学   1170篇
口腔科学   36篇
临床医学   510篇
内科学   771篇
皮肤病学   128篇
神经病学   217篇
特种医学   109篇
外国民族医学   1篇
外科学   285篇
综合类   1238篇
预防医学   358篇
眼科学   14篇
药学   513篇
  3篇
中国医学   300篇
肿瘤学   363篇
  2023年   36篇
  2022年   83篇
  2021年   160篇
  2020年   184篇
  2019年   111篇
  2018年   93篇
  2017年   155篇
  2016年   158篇
  2015年   160篇
  2014年   241篇
  2013年   274篇
  2012年   268篇
  2011年   310篇
  2010年   242篇
  2009年   223篇
  2008年   215篇
  2007年   244篇
  2006年   273篇
  2005年   239篇
  2004年   225篇
  2003年   252篇
  2002年   168篇
  2001年   175篇
  2000年   180篇
  1999年   139篇
  1998年   144篇
  1997年   143篇
  1996年   106篇
  1995年   137篇
  1994年   149篇
  1993年   101篇
  1992年   98篇
  1991年   97篇
  1990年   81篇
  1989年   63篇
  1988年   43篇
  1987年   46篇
  1986年   32篇
  1985年   54篇
  1984年   52篇
  1983年   26篇
  1982年   30篇
  1981年   13篇
  1980年   11篇
  1979年   11篇
  1978年   3篇
  1977年   11篇
  1975年   3篇
  1971年   2篇
  1906年   1篇
排序方式: 共有6269条查询结果,搜索用时 39 毫秒
71.
李峰生  杨曌  江其生 《免疫学杂志》2005,21(Z1):103-105
机体受到一定剂量核辐射后会出现多个器官结构和功能的改变.本文综述了机体受到低剂量核辐射后出现的免疫细胞数量和功能变化,包括淋巴细胞总数和部分亚群数量、淋巴细胞转化率、血清免疫球蛋白含量以及单核细胞功能等变化.同时还综述了核辐射对内分泌及遗传的影响.  相似文献   
72.
乙型肝炎表面抗原对BALB/c小鼠细胞免疫应答的影响   总被引:6,自引:3,他引:6  
目的研究不同来源乙肝表面抗原(HBsAg)对BALB/c小鼠的某些细胞免疫应答的影响.方法采用血源、CHO和酵母HBsAg分别免疫BALB/c小鼠,于免疫后不同时间制备脾脏单个核细胞(MNC),测定MNC对刀豆蛋白(ConA)和细菌脂多糖(LPS)的增殖反应性;采用绵羊红细胞(SRBC)作为致敏原,测定不同HBsAg免疫小鼠后迟发性超敏反应(DTH)的发生程度.结果不同来源HBsAg对ConA或LPS刺激的反应指数(SI)表现出不同的时间曲线,一般于免疫20?d和25?d时显著升高,其中血源HBsAg较高,酵母较低.H.M.-HBsAg在免疫5?d时即显出较高的SI值.CHO-HBsAg对SRBC诱导的DTH反应具有显著的抑制作用(P<0.05).结论不同来源HBsAg诱导细胞免疫反应的类型和程度存在差异,CHO细胞来源的HBsAg对TH1细胞介导的DTH反应有抑制作用.  相似文献   
73.
白术多糖对小鼠淋巴细胞功能的调节   总被引:54,自引:1,他引:54  
研究了白术多糖PAM体内及体外对小鼠脾淋巴细胞的调节作用。结果表明:白术多糖PAM在一定的浓度范围内能单独激活或协同ConA/PHA促进正常小鼠淋巴细胞转化并能明显提高IL-2分泌的水平。PAM对氢化可的松造成的免疫抑制小鼠淋巴细胞的增殖功能有恢复作用。同时还发现白术多糖PAM对淋巴细胞的调节与β-肾上腺素受体激动剂异丙肾上腺素相关。  相似文献   
74.
75.
以CD3McAb为激动剂,以淋巴细胞体外DNA合成为研究手段,探讨了AC-cAMP-PKA信号途径在CD3McAb诱导的淋巴细胞活化中的意义。研究结果表明AC、cAMP和PKA在决定细胞对外界刺激的反应中起着重要作用。在淋巴细胞活化早期细胞内cAMP出现一过性升高,随着细胞活化增殖,cAMP降至正常水平以下。活化AC、升高细胞内cAMP水平可显著降低CD3McAb诱导的淋巴细胞DNA合成,而PKI却能在一定程度上促进淋巴细胞活化增殖。  相似文献   
76.
Summary Although the psychological disturbances accompanying Graves' disease are well known, the time required for normalisation of these disturbances during antithyroid drug treatment is not known. Therefore sequential psychological testing during the course of Graves' disease was done. There are also contradictory results concerning the possible correlation of neurophysiological and psychological test results during the course of Graves' disease with thyroid hormone values. Finally, psychological disturbances have been proposed as possible etiologic factors in Graves' disease.In our study, a significant decrease in anxiety and irritability could be observed at the time euthyroidism was achieved. Self-evaluations of depressivity, activity, exhaustion, well-being, extraversion, introversion, and the ability to concentrate changed 1 or 2 months after euthyroidism was induced. Similar test results could be observed after induction of euthyroidism by antithyroid drugs and subtotal thyroid resection. Therefore the mode of therapy does not seem to influence the course of normalisation of psychological parameters.In contrast to other investigations there was hardly any correlation between thyroid hormone values and psychological test results or the ability to concentrate. Nontheless, patients with Graves' disease showing high scores for depression and anxiety exhibit abnormal peripheral helper/suppressor T-lymphocyte relations. Furthermore, patients suffering from Graves' disease tend to be more anxious than controls. It remains to be determined whether an increased susceptibility to psychological disturbances has led to these alterations of lymphocyte subsets in Graves' disease patients with severe depression and anxiety.Supported by SFB 258  相似文献   
77.
目的 研究大鼠肠系膜淋巴结内高内皮微静脉与淋巴迷路之间淋巴细胞归巢的通路.方法 用镀银染色光镜观察法和冻裂割断扫描电镜观察法观察健康、成熟Wistar大鼠肠系膜淋巴结的基质网状结构.结果 位于高内皮微静脉和淋巴迷路周围有网状纤维支架,在二者相临近部位有密集交织的网状纤维网.结论 淋巴结内高内皮微静脉和淋巴迷路之间密集交织的网状纤维网,为细胞的居留和迁移提供结构支持和适宜的微环境,可能是淋巴细胞归巢的重要通路.  相似文献   
78.
目的:研究严重急性呼吸综合症(SAPS)患者T细胞亚群变化。方法:检索2003年2月-2004年1月有关SAPS患者T细胞亚群计数研究的论文,汇合成大样本资料,借助先进的RevMan4.2分析软件对这些资料进行二次分析以探讨该病患者T细胞亚群变化。结果:SAPS病程〈14天期间,患者与正常对照比较,CD3^+细胞、CD4^+细胞、CD8^+细胞均显著降低(均P〈0.01)。其中,重症病人(包括重型和极重型)比非重症病人(包括轻型和普通型)降低更显著(均P〈0.01)。病程〉14天恢复期病人与病程〈14天病人比较,CD3^+细胞虽然有了上升,但无显著差异(Z=1.56,P=0.12)。CD4^+细胞、CD8^+细胞均恢复性上升,差异显著(均P〈0.01)。病程〉14天恢复期病人与正常对照比较,CD3^+细胞、CD4^+细胞仍然显著降低(均P〈0.01)。两者的CD8^+细胞有差异(Z=2.28,P=0.02)。结论:①SAPS患者整个病程中都存在CD3^+细胞、CD4^+细胞、CD8^+细胞数量暂时性、严重性、可逆性降低;②患者T细胞亚群数量的下降以重症病人为甚;③这种降低是可逆性的,随着病程进入恢复期,患者T细胞亚群开始恢复性上升。  相似文献   
79.
The pathogenic mechanisms that lead to chronic hepatitis C are unknown. As hepatitis C virus (HCV) has been shown to induce T cell response, we assessed whether a particular T lymphocyte subset could be preferentially detected in the liver of patients with chronic hepatitis C in relation to viraemia or HCV genotypes. The immunophenotypes of liver-derived lymphocytes were analysed in 26 patients by flow cytometry and immunohistochemistry. Viraemia was quantified by branched DNA assay. Using this assay, HCV RNA was not detectable in six patients. HCV RNA was detected in 20 patients, and titres ranged from 8 to 137 x 10(6) Eq/ml. Genotyping was performed using a line probe assay. Type 1a, 1b, 2a, 3a and 4a were found to infect 2, 10, 2, 7 and 3 patients, respectively. The CD4+/CD8+ ratio of liver-derived lymphocytes was significantly higher (P < 0.01) in patients with detectable viraemia than in patients without detectable viraemia. In contrast, neither the percentage of gamma/delta T lymphocytes nor that of CD2+CD57+ cells was different in the groups. When comparing the CD4+/CD8+ ratio, the percentage of gamma/delta T lymphocytes or CD2+CD57+ cells according to genotype, the differences were not significant. These results suggest that the CD4+/CD8+ ratio of liver-derived lymphocytes is related to viraemia but not to HCV genotypes in patients with chronic hepatitis C, and that T lymphocytes may be involved in the pathogenesis of liver lesions in chronic hepatitis C.  相似文献   
80.
PROBLEM: Pregnancy affects the maternal immune system and the clinical course of maternal diseases. Here we report the changes in the detailed lymphocyte subsets of helper T cells, suppressor T cells, CD5+ B cells, T cell receptor (TCR) αβ-positive T cells (Tαβ cells), TCRαβ-negative T cell (Tγδ cells), and others during and after pregnancy through to one year postpartum, and discuss the significance of the changes. METHOD: The absolute numbers of helper T cells, suppressor T cells, cytotoxic T cells, TCRαβ-negative T cells (Tγδ cells), CD5 B cells, CD5+ B cells, and NK cell subsets were examined by two-color flow cytometry in peripheral blood from 51 healthy non-pregnant women, 106 healthy pregnant women, and 148 healthy postpartum women. RESULTS: In early pregnancy, the numbers of suppressor T cells and NK cells with strong cytotoxicity (NK+++ cells) increased, and the number of cytotoxic T cells decreased. In late pregnancy, the helper T cell and NK+++ cell numbers decreased. Tαβ, CD5 B and CD5+ B cells decreased during pregnancy. After delivery, helper T cells and cytotoxic T cells increased from 1 to 4 months postpartum, and suppressor T cells increased at 7 months postpartum. TCRαβ-negative T cells increased at 4 to 10 months postpartum. Both CD5 and CD5+ B cells decreased further at 1 month postpartum, but CD5+ B cells increased markedly at 7 to 10 months postpartum. CONCLUSIONS: These data indicate that 1) early increases of suppressor T cells and NK+++ cells during pregnancy may be related to the mechanism to accept or reject the fetus in early pregnancy, respectively; 2) late decreases of helper T cells and NK+++ cells may be related to the maintenance of pregnancy: 3) postpartum increases of helper T cells, cytotoxic T cells, TCRαβ-negative T cells (Tγδ cells), and CD5+ B cells may be related to the postpartum aggravation of autoimmune diseases; and 4) the immunological effects of pregnancy remains until about 1 year after delivery.  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