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   2473篇
  免费   144篇
  国内免费   29篇
耳鼻咽喉   20篇
儿科学   84篇
妇产科学   50篇
基础医学   367篇
口腔科学   59篇
临床医学   176篇
内科学   731篇
皮肤病学   66篇
神经病学   158篇
特种医学   47篇
外科学   330篇
综合类   6篇
预防医学   60篇
眼科学   5篇
药学   175篇
中国医学   2篇
肿瘤学   310篇
  2023年   39篇
  2022年   65篇
  2021年   103篇
  2020年   46篇
  2019年   79篇
  2018年   79篇
  2017年   38篇
  2016年   63篇
  2015年   61篇
  2014年   66篇
  2013年   85篇
  2012年   125篇
  2011年   152篇
  2010年   71篇
  2009年   70篇
  2008年   129篇
  2007年   132篇
  2006年   115篇
  2005年   121篇
  2004年   88篇
  2003年   100篇
  2002年   93篇
  2001年   60篇
  2000年   68篇
  1999年   72篇
  1998年   28篇
  1997年   16篇
  1996年   19篇
  1995年   17篇
  1993年   11篇
  1992年   22篇
  1991年   29篇
  1990年   41篇
  1989年   28篇
  1988年   23篇
  1987年   25篇
  1986年   29篇
  1985年   29篇
  1984年   10篇
  1983年   15篇
  1981年   11篇
  1980年   13篇
  1979年   12篇
  1978年   20篇
  1977年   13篇
  1976年   9篇
  1974年   9篇
  1972年   13篇
  1971年   9篇
  1970年   9篇
排序方式: 共有2646条查询结果,搜索用时 15 毫秒
1.
This article describes the construction and use of a new end graft holder during coronary artery bypass grafting (CABG). The instrument consists of a pinching device attached to a flexible arm and a fixation clamp. This device provides secure stabilization and enables excellent positioning of the graft without producing graft injury.  相似文献   
2.
3.
4.
5.
Human beta-defensin(hBD)-2, an antimicrobial peptide, is produced by various epithelial cells. Because hBD-2 expression in the oral epithelium has not been assessed, we investigated its localization in normal oral epithelium and epithelial lesions. hBD-2 expression was studied using immunohistochemistry and in situ hybridization on formalin-fixed, paraffin-embedded tissue sections from 30 cases of squamous cell carcinoma and 6 cases of leukoplakia. Immunostaining for hBD-2 was more intense in hyperkeratinized than in ortho- or non-keratinized epithelium. In contrast, signals for hBD-2 mRNA were frequently stronger in non-keratinized epithelium than in hyper- or ortho-keratinized epithelium. The results suggest that keratinization in oral epithelium plays an important role in the biological function of hBD-2 both at the mRNA level and in the retention of the peptide in the epithelium.  相似文献   
6.
Anti-idiotypic (anti-ID) antibody in test serum was determined by the direct binding assay using 125I-anti-human thyroglobulin (hTg). Several positive cases were found in Graves' disease and thyroiditis chronica. Positive anti-ID antibodies could be classified into two types. Type 1 showed the positive anti-hTg antibody and high Tg levels by RIA using double antibody method. Type 2 showed the positive anti-hTg antibody but low Tg levels by RIA. The binding of 125I-hTg to anti-hTg antibody was displaced by anti-ID antibody in type 1, but was not anti-ID antibody in type 2. A case of coexistence of autoantibody to hTSH and auto-anti-ID antibody to anti-hTSH antibody was found. She showed normal thyroid function (T4, T3), but TSH level showed discrepancy by different assay methods. Both autoantibodies for hTSH and for anti-hTSH antibody were demonstrated by the reaction of patient's antibody with both 125I-hTSH and 125I-anti-hTSH (MoAb). These two autoantibodies belong to the polyclonal IgG. The autoantibody for hTSH recognized only the beta-subunit of hTSH. Neither stimulating type of TSH receptor antibody (TRAb) nor blocking type of TRAb interfered with the binding of patient's anti-ID to 125I-anti-hTSH. This binding reaction could be inhibited by the unlabeled hTSH. This anti-ID might represent the internal image of the non-biological active site of TSH molecule, because of absence of thyroid stimulating activity. These anti-ID antibodies may provide evidence supporting a network theory of the immune system.  相似文献   
7.
BACKGROUND: The loop-mediated isothermal amplification (LAMP) method is a novel technique for the amplification of specific DNA sequences. OBJECTIVES: To establish the LAMP method for amplifying Epstein-Barr virus (EBV) DNA and to examine its reliability for the detection of EBV DNA in clinical specimens. STUDY DESIGN: Sera from 108 patients, who were initially suspected of primary EBV infection, were tested by the EBV LAMP method, and the results were compared with those of the real-time PCR assay. Serological examination was regarded as the standard diagnostic method. RESULTS: To diagnose primary EBV infection, the sensitivity of LAMP was 86.4% and the specificity was 100%. The sensitivity of the real-time PCR assay was 84.1% and the specificity was 98.4%. Longitudinal analysis showed that the detection rate of EBV DNA in serum by the LAMP method decreased with time in accordance with the decrease of the EBV load. EBV DNA could not be detected in serum 40 days after onset of symptoms. CONCLUSIONS: These results indicate that the sensitivity and specificity of the LAMP method are comparable to those of real-time PCR and that detecting EBV DNA in serum by this method is potentially useful for diagnosing primary EBV infection.  相似文献   
8.
Sleep timing is influenced by the circadian system. Morningness-eveningness (ME) preference in humans is affected by the free-running period, which is determined by circadian clock-relevant genes. In this study, we investigated association between the 3111T/C polymorphism in the 3'-flanking region of hClock (Homo sapiens Clock homolog) and ME preference in 421 Japanese subjects. The Horne-Ostberg ME questionnaire (MEQ) scores showed normal distribution, with mean score of 51.2 +/- 1.4 (range, 25-73), and scores were positively correlated with sleep onset time (r = 0.541, P < 0.001) and wake time (r = 0.513, P < 0.001). MEQ scores were significantly lower in subjects with 3111C/C (n = 12) than in subjects with 3111T/C (n = 106, P < 0.001) or 3111T/T (n = 303, P < 0.001), suggesting a stronger eveningness preference in 3111C/C homozygotes. This group also showed significantly delayed sleep onset (P < 0.001), shorter sleep time (P < 0.001), and greater daytime sleepiness (P < 0.001) in comparison to parameters in the subjects with the 3111T allele. There was no significant difference in any of these parameters between the 3111C/T and 3111T/T genotypes. The influence of the 3111T/C polymorphism on ME preferences in Caucasian populations remains controversial. The present findings in a Japanese population sample, which should have a relatively low risk of population stratification effects, suggest the significance of the association of the 3111C/C allele of hClock with evening preference.  相似文献   
9.
Association of Epstein-Barr virus with oral cancers   总被引:2,自引:0,他引:2  
  相似文献   
10.
Integrins are not involved in the process of human sperm-oolemmal fusion   总被引:3,自引:0,他引:3  
BACKGROUND: We investigated whether integrins are required forthe human sperm–oocyte binding and fusion processes. METHODS:The expression of several integrin subunits at the human oocyteplasma membrane was investigated using immunofluorescence microscopy,and the functional role of integrins expressed at the humanoocyte surface in sperm–oocyte interaction was studiedusing a zona-free human oocyte binding and fusion assay. A totalof 144 unfertilized oocytes were stained with anti-integrinantibodies and 147 zona-free unfertilized oocytes were inseminatedin the presence of various anti-integrin antibodies that wereexpressed in oocyte plasma membrane. RESULTS: The antibodiesof six integrin subunits (2, 3, 5, 6, V, M) and six integrinsubunits (1, 2, 3, 4, 5, 6) were bound to the surface of fixedunfertilized oocytes. In contrast, the presence of 1 and 4 subunitscould not be verified. The human sperm–oocyte bindingwas only partially inhibited by blocking antibodies of 2, 3,5, 6, V, M, 1, 2 and 3 with a maximum of 55% inhibition, butantibodies of 4, 5 and 6 showed no effect on sperm–oolemmalbinding. A similar reduction of the number of fused sperm wasobserved. However, the ratio of fused sperm to total sperm (boundand fused) was not impaired by all integrin antibodies, suggestingthat integrins had no role in the sperm–oolemmal fusionprocess. CONCLUSIONS: These results suggest that one of thebinding mechanisms can be inhibited by integrin antibodies butthat this mechanism does not play an essential role in the humansperm–oolemmal binding and fusion processes. The othermechanisms, insensitive to integrins, may involve both bindingand fusion processes in human oocytes.  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