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   71401篇
  免费   5811篇
  国内免费   3281篇
耳鼻咽喉   196篇
儿科学   1336篇
妇产科学   829篇
基础医学   12731篇
口腔科学   739篇
临床医学   5546篇
内科学   16765篇
皮肤病学   1075篇
神经病学   2649篇
特种医学   1293篇
外国民族医学   9篇
外科学   3877篇
综合类   10557篇
现状与发展   19篇
预防医学   6030篇
眼科学   486篇
药学   8831篇
  18篇
中国医学   3541篇
肿瘤学   3966篇
  2023年   798篇
  2022年   1861篇
  2021年   2297篇
  2020年   2156篇
  2019年   2387篇
  2018年   2279篇
  2017年   2244篇
  2016年   2604篇
  2015年   2869篇
  2014年   4664篇
  2013年   4854篇
  2012年   4780篇
  2011年   5097篇
  2010年   4124篇
  2009年   3928篇
  2008年   3874篇
  2007年   3762篇
  2006年   3431篇
  2005年   2933篇
  2004年   2431篇
  2003年   2107篇
  2002年   1712篇
  2001年   1499篇
  2000年   1157篇
  1999年   1009篇
  1998年   926篇
  1997年   769篇
  1996年   650篇
  1995年   662篇
  1994年   566篇
  1993年   463篇
  1992年   440篇
  1991年   349篇
  1990年   318篇
  1989年   286篇
  1988年   239篇
  1987年   205篇
  1986年   171篇
  1985年   443篇
  1984年   462篇
  1983年   373篇
  1982年   379篇
  1981年   316篇
  1980年   292篇
  1979年   261篇
  1978年   205篇
  1977年   160篇
  1976年   176篇
  1975年   153篇
  1974年   126篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
采用ELISA法检测104例各类型乙型肝炎(乙肝)患者的血清前-S2抗原(Pre-S2Ag)及其抗体(Pre-S2Ab),结果表明,Pre-S2Ag的出现与HBsAg、HBeAg、HBcAb呈显著相关性(P值均<0.005),主要见于乙肝急性期及慢性乙肝患者,说明病毒复制活跃、传染性强。而Pre-S2Ab阳性仅见于急性乙肝恢复期。  相似文献   
62.
Cytochemical analysis of leukemic blasts from 46 patients with acute myeloblastic M2 leukemia (according to the FAB classification) was performed before and after cytostatic therapy, and compared with findings obtained in 20 age- and sex-matched control subjects. Cytochemical findings for myeloperoxidase (MPO), Sudan black B, acid phosphatase and alpha-naphthyl-acetate esterase (ANAE) were related to the achievement of the first complete remission (CR),i.e. data were compared after the patients had been divided into CR and non-CR groups. The analysis clearly showed that a high proportion of myeloperoxidase- and, to a lesser extent, Sudan black B-positive blasts before treatment may have constituted a significantly unfavourable prognostic factor.  相似文献   
63.
In two independent trials 10 and 12 healthy volunteers received the novel intravenous immunoglobulin (IVIG) preparations BT 511 and BT 507, respectively. BT 511 contains 5 g human plasma proteins per 100 ml, more than 95% of which are immunoglobulins of the G class (IgG). BT 507 contains in addition 61 IU antibody against hepatitis B surface antigen (anti-HBs)·ml–1. In trial I volunteers received 4.0 ml/kg (n+4) and 8.0 ml·kg–1 (n+6) BT 511 to study the tolerability and the magnitude of the increase in immunoglobulins in plasma as well as their decline over 1 month. After administration of the lower dose, plasma IgG increased from 10.7 to 14.7 g·l–1 directly after the infusion. Following the 8.0 ml·kg–1 dose a more pronounced increase from 12.4 to 21.2 g·l–1 was observed. No adverse events occurred. After 1 month IgG concentrations had almost reached baseline values at 12.2 g·l–1 in the 4.0 ml·kg–1 group, but were still significantly increased at 15.2 g·l–1 after the high dose. There was a linear correlation between the maximal IgG plasma concentration and the subsequent decline of IgG during the 29-day observation period. After administration of BT 507 maximal anti-HBs concentrations of 1778 mU·ml–1 occurred 1.4 h after termination of the infusion. The terminal elimination half-life was 22.4 days, and total clearance and volume of distribution were determined to be 0.122 ml·min–1 and 5.41, respectively. The pharmacokinetic parameters calculated for anti-HBs as an indicator of IgG were in accordance with the pharmacokinetic behaviour of native IgG.  相似文献   
64.
65.
A panel of synthetic peptides representing human lymphocyte antigen (HLA) B8, other class I and class II restricted T cell epitopes and two B cell epitopes, were all able to compete with recognition of a HLA B8 restricted epitope by a cytotoxic T cell clone. Competition was obtained when the competitor peptides were added either before or after the target epitope. The target epitope also had a slow off rate, implicating allosteric inhibition. The presence of non-specific, allosteric binding sites may interfere with experiments attempting to define immunologically relevant MHC binding specificities.  相似文献   
66.
In a preceding study, we reported that the numbers of macrophages and polymorphonuclear leukocytes (PMN) were increased in bronchoalveolar lavage fluid (BALF) following the intratracheal instillation of nickel sulfate (NiSO4) in rats. In the present study, BALF chemotactic activities for both macrophages and PMN were measured to investigate if the increases of these inflammatory cells in BALF depend on increases in chemotactic activities in epithelial lining fluid (ELF) of the lung. Both the number of PMN and the PMN chemotactic activity peaked at 2 days post-instillation and they were significantly correlated. However, the PMN chemotactic activity was inversely correlated with concentration of leukotriene B4 (LTB4), a well-known chemotaxin. Although PMN were not observed in control BALF, LTB4 concentration in the control ELF (ca. 5×10–7 M) was estimated to have a potential to attract PMN chemotactically through a membrane in in vitro migration assay. These results suggest that the presence of LTB4 in ELF itself does not trigger transpulmonary PMN infiltration. The rat BALF were fractionated by high performance liquid chromatography (HPLC), and PMN chemotactic activity of each fraction was measured. The elution profiles of PMN chemotactic activity showed that there were at least two different chemotaxins in BALF obtained from the NiSO4-exposed rats. Macrophage chemotactic activity in BALF also peaked at 2 days post-instillation. However, the number of macrophages was not significantly correlated with the chemotactic activity for macrophage in BALF. The HPLC study showed that the macrophage chemotactic substance in the BALF obtained from NiSO4-exposed rats was different from complement fragment (C5a) and its MW was estimated to be 10 – 12 kD. Received: 1 December 1993/Accepted: 16 March 1994  相似文献   
67.
多重PCR归化法平行检测HBV和HCV的研究   总被引:3,自引:0,他引:3  
目的:建立一种多重PCR归化法并应用于对HBV、HCV平行检测。方法:利用PCR反应5′端允许添加非互补序列的原理,运用内外两对引物,经过2轮扩增,使目的产物均带上共有序列,再以共有序列为引物进行扩增,实现多重扩增。比较和筛选四种核酸提取方法。运用正交优化法,优化并确定最佳扩增条件。对28份血标本进行对比试验,并进行质量评价。结果:归化多重PCR方法对于HBV、HCV病毒合并感染患者的诊断敏感性为83.5%,诊断特异性为70.0%,诊断指数为153.3%,诊断效率为72.2%;对HBsAg阳性患者的HBV DNA的诊断敏感性为78.6%,诊断特异性为80.0%,诊断指数为158.6%,诊断效率为79.2%。对抗-HCV阳性患者的HCV RNA的诊断敏感性为75.0%,诊断特异性为90.0%,诊断指数为165.0%,诊断效率为83.3%。结论:多重PCR归化法在多基因扩增或多种病原体的同时平行检测领域具有较大应用潜力。该方法实用、准确、可靠,对HBV HCV的防治具有实际意义。  相似文献   
68.
目的 探讨冠心病患者血清同型半胱氨酸(HCY)与叶酸、维生素B12浓度的变化及其相关性。方法 选择84例经冠状动脉造影术证实为冠心病的患者,应用荧光偏振免疫分析法(FPIA)测定血清HCY浓度,离子捕获免疫分析法(ICIA)测定血清叶酸浓度,非均相微粒子酶免疫分析法(MEIA)测定血清维生素B12浓度。结果 冠心病患者血清HCY浓度增高,与正常对照组比较有显著性意义(P<0.001),而叶酸、维生素B12浓度则降低,与正常对照组比较有显著性意义(P<0.001),以上两种变化呈负相关(P<0.001)。结论 同型半胱氨酸血症是冠心病的新的独立危险因素,叶酸、维生素B12缺乏可能是诱发高HCY的重要因素。  相似文献   
69.
熊艳 《现代护理》2007,13(2):357-358
目的 观察行为干预对慢性乙型肝炎患者健康行为的影响。方法 将300例慢性乙型肝炎患者作为目标人群进行健康教育,建立目标人群管理档案,进行目标人群健康行为干预,比较教育前后相关行为的改变。结果 慢性乙型肝炎患者8项健康行为和8项危险健康行为有明显改观,差异具有统计学意义(P〈0.01)。结论 通过行为干预,有效地使慢性乙型肝炎患者完全遵从医嘱合理用药,完全依从健康行为,从而减少危险行为的发生。  相似文献   
70.
To clarify the prevalence of concurrent infection with hepatitis C virus (HCV), hepatitis B virus (HBV) and human T cell leukaemia virus (HTLV), we measured HCV antibody in the population of a district endemic for HBV and HTLV infection. Blood samples were collected in June 1990 from 579 inhabitants of four islands of Uwa Bay in the southwest of Ehime Prefecture in Japan. Anti-HCV antibody against C100-3 protein was detected using an enzyme-linked immunosorbent assay kit (Ortho Diagnostics). Thirteen of the 579 inhabitants (2.2%) were positive for anti-HCV, and this prevalence rate was not significantly different from the frequency of anti-HCV in Tokyo blood donors. A total of 11% (64 of 579) of the subjects were positive for HBsAg and 3.3% (19 of 579) were positive for anti-HTLV. These frequencies of HBsAg and anti-HTLV positivity were distinctly higher than the respective means of Japanese. All anti-HCV positive individuals were negative for HBsAg and anti-HTLV, while 54% (7 of 13) had increased alanine aminotransferase levels. These data suggest that the prevalence of HCV infection is not high even in an area endemic for HBV and HTLV infection.  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