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   1648篇
  免费   149篇
  国内免费   23篇
耳鼻咽喉   38篇
儿科学   75篇
妇产科学   31篇
基础医学   180篇
口腔科学   71篇
临床医学   225篇
内科学   298篇
皮肤病学   16篇
神经病学   85篇
特种医学   149篇
外科学   183篇
综合类   46篇
一般理论   3篇
预防医学   184篇
眼科学   30篇
药学   104篇
中国医学   1篇
肿瘤学   101篇
  2023年   14篇
  2021年   37篇
  2020年   30篇
  2019年   28篇
  2018年   25篇
  2017年   29篇
  2016年   33篇
  2015年   34篇
  2014年   44篇
  2013年   51篇
  2012年   64篇
  2011年   69篇
  2010年   59篇
  2009年   43篇
  2008年   66篇
  2007年   89篇
  2006年   68篇
  2005年   47篇
  2004年   44篇
  2003年   57篇
  2002年   42篇
  2001年   69篇
  2000年   49篇
  1999年   39篇
  1998年   47篇
  1997年   30篇
  1996年   42篇
  1995年   33篇
  1994年   34篇
  1993年   34篇
  1992年   42篇
  1991年   22篇
  1990年   39篇
  1989年   26篇
  1988年   37篇
  1987年   34篇
  1986年   29篇
  1985年   19篇
  1984年   18篇
  1983年   11篇
  1982年   16篇
  1981年   11篇
  1980年   17篇
  1978年   13篇
  1977年   13篇
  1976年   10篇
  1974年   10篇
  1973年   14篇
  1972年   9篇
  1970年   9篇
排序方式: 共有1820条查询结果,搜索用时 15 毫秒
51.
Age-related senescence of T-cell mediated responses is well recognized. This study was designed to determine how aging affects the T-cell mediated Interleukin 2 (IL2) response to influenza vaccination. A group of healthy elderly individuals were compared to a control group of healthy young adults for their response to the 1990 influenza vaccine. Cultures of peripheral blood mononuclear cells (PBMC) were prepared from venous blood samples taken prevaccination (pre) and 8 and 12 weeks post-vaccination (post). PBMC cultures stimulated with inactivated A/Shanghai/16/89 (contained in the 1990 vaccine) and A/Philippine/2/82 (not contained in the vaccine) were assayed for peak IL2 activity. We find that after influenza vaccination, there was an insignificant increase in IL2 activity when PBMC from the young control group were stimulated with A/Shanghai/16/89 (pre, 5.14 U/mL/10(6) PBMC; post, 6.64 U/mL/10(6) PBMC) but there was a significant increase in IL2 activity when stimulated with A/Phillippine/2/82 (pre, 1.5 U/mL/10(6) PBMC; post, 8.3 U/mL/10(6) PBMC). In similar cultures of PBMC from the elderly group, there was a significant increase in IL2 response to both A/Shanghai/16/89 (pre, 1.6 U/mL/10(6) PBMC; post, 3.5 U/mL/10(6) PBMC) and A/Philippine/2/82 (pre, 0.86 U/mL/10(6) PBMC; post, 8.3 U/mL/10(6) PBMC). Measurements of CD4+/CD8+ populations were not affected by vaccination and were not significantly different in the two groups. Subgroup analysis of the elderly group revealed that previous influenza vaccination in 1989 did not significantly affect IL2 levels measured in the present study. This study shows that in healthy elderly, influenza vaccination effectively restores IL2 activity to normal. There appears to be an age-related decrease in the duration of T-cell memory.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
52.
Although allogeneic transplantation can be curative for patients with sickle cell disease, the toxicity of conditioning regimens has precluded its use in adults with significant end-organ damage. Newer conditioning regimens have been developed that are less toxic and that may broaden the applicability of allogeneic transplantation in this disorder. We report two adults with end-stage sickle cell disease, who underwent allogeneic transplantation from an HLA-identical sibling donor after conditioning with fludarabine/melphalan and ATG. Both patients had been extensively transfused and one had multiple RBC antibodies. One of the patients also had end-stage renal disease, and was dialysis dependent. Engraftment occurred promptly in both patients. Both achieved 100% donor chimerism and both were free of pain crises after transplant. The first patient died of a respiratory failure related to chronic graft-versus-host disease (GVHD) on day 335 after transplantation. The second patient developed severe gastro-intestinal GVHD and TTP and died on day 147 after transplantation. Conditioning with fludarabine/melphalan and ATG followed by allogeneic stem cell transplantation resulted in prompt and reliable engraftment in adults with end-stage sickle cell disease. The incidence of severe GVHD was unacceptably high and may be related to the ethnicity of the patients or to the inflammatory state associated with pre-existing sickle cell disease.  相似文献   
53.
54.
A previous audit conducted in the West of Scotland (WoS) suggested that anatomical factors accounted for a substantial proportion of invaded surgical margins after resection of an oral or oropharyngeal squamous cell carcinoma (SCC). Since then a number of technical improvements have taken place, the most important of which has been advanced digital imaging that has enabled better surgical planning. In this study we compare the incidence of involved surgical margins in a recent group with those found in the earlier audit. The earlier (WoS) group comprised a consecutive series of patient operated on for a primary SCC of the oral cavity or oropharynx between November 1999 and November 2001 (n = 296). The later series comprised 178 patients operated on for oral or oropharyngeal SCC at the Southern General Hospital (SGH), Glasgow, between 2006 and 2009. A total of 245 patients in the WoS cohort had information available on the invasion of the margins of whom 68 (28%) had an invaded margin. Of 177 patients in the SGH group, 9 (5%) had an invaded margin (p = 0.001). An anatomical approach to the resection of oral and oropharyngeal SCC is appropriate, as it results in a rate of invaded margins of less than 10% irrespective of size and site of the primary lesion.  相似文献   
55.
BACKGROUND: Canada converted from the platelet‐rich plasma (PRP) method to the buffy coat (BC) method of processing whole blood donations between 2006 and 2008. We measured coagulation variables in plasma units during this transition, in 2006 (PRP only), 2007 (BC and PRP), and 2008 (BC only) to test the hypothesis that this conversion would not affect frozen plasma (FP) quality. STUDY DESIGN AND METHODS: Fresh‐frozen plasma (FFP; frozen within 8 hr of collection) or FP (frozen within 24 hr of collection) units were shipped on dry ice from 12 plasma manufacturing sites, thawed, and characterized using an automated coagulation analyzer, at a single testing site. RESULTS: FP made by the BC method (FP‐BC) exhibited fibrinogen, Factor (F)V, ABO‐matched FVIII, and antithrombin levels at least as high as FP made by the PRP method (FP‐PRP) and supported global clotting, as measured by prothrombin time or activated partial thromboplastin time, to an indistinguishable extent as FP‐PRP. FP‐BC and FP‐PRP did not differ in ABO‐matched FVIII levels, but both contained 30% to 35% less FVIII than FFP. There was no discernible effect of the site of manufacturing on plasma quality. FP‐BC units leukoreduced by centrifugation contained more FV activity than those leukoreduced by filtration, but the difference was unlikely to be of clinical significance. CONCLUSION: Our data suggest that no reduction in FP quality, at least in the characteristics we tested, accompanied the switch from the PRP to the BC method processing of whole blood donations in Canada.  相似文献   
56.
BACKGROUND: The survival of patients with human immunodeficiency virus (HIV) has improved considerably with modern medical management. However, there remains surprisingly little information on treating head and neck neoplasms in HIV-positive patients. OBJECTIVE: To report our recent experience treating oral cavity and oropharyngeal tumors in HIV-positive patients. DESIGN AND PATIENTS: Retrospective analysis of a cohort of 8 HIV-positive patients with Kaposi sarcoma (KS), lymphoma, or squamous carcinoma of the oral cavity or oropharynx who were consecutively treated during a single year with radiation therapy at a tertiary care referral center. Length of follow-up was at least 2 years (mean, 2.5 years). RESULTS: All patients had partial and complete responses to treatment lasting until the last follow-up. However, we found that treatment was considerably better tolerated by patients with non-KS tumors, with fewer acute reactions and significantly less weight loss, despite larger treatment volumes and higher radiation doses, compared with patients with KS. Patients with non-KS tumors received a mean radiation dose of 62.6 Gy to 2636 cm3, yet lost only a mean of 0.1 kg in weight, whereas patients with KS were treated with a mean radiation dose of 19 Gy to a mean volume of 568 cm3, but lost a mean of 5.8 kg during treatment (P = .005) and on average sustained an additional grade of severity on a standard scale of mucosal reaction (P = .01). CONCLUSIONS: Oral cavity and oropharyngeal tumors in HIV-positive patients respond to radiation therapy, but there is a marked difference in the degree of acute reactions to treatment between patients with and without KS. Infection with HIV is not a contraindication when aggressive radiation therapy is needed in select patients.  相似文献   
57.
58.
We conducted the first study that estimates the sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of a population-based autism spectrum disorders (ASD) surveillance system developed at the Centers for Disease Control and Prevention. The system employs a records-review methodology that yields ASD classification (case versus non-ASD case) and was compared with classification based on clinical examination. The study enrolled 177 children. Estimated specificity (0.96, [CI.95 = 0.94, 0.99]), PPV (0.79 [CI.95 = 0.66, 0.93]), and NPV (0.91 [CI.95 = 0.87, 0.96]) were high. Sensitivity was lower (0.60 [CI.95 = 0.45, 0.75]). Given diagnostic heterogeneity, and the broad array of ASD in the population, identifying children with ASD is challenging. Records-based surveillance yields a population-based estimate of ASD that is likely conservative.  相似文献   
59.
60.
This paper uses data from the 2009 Kids’ Life and Times Survey, involving 3657 children aged 10 or 11 years old in Northern Ireland. The survey indicated high levels of use of Internet applications, including social-networking sites and online games. Using the KIDSCREEN-27 instrument, the data indicate that the use of social-networking sites and online games is related to poorer psychological well-being among girls, but not boys. Boys and girls who experience “cyberbullying” have poorer psychological well-being. This association between psychological well-being and some Internet applications merits more attention in future research and policy development.  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