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   478篇
  免费   11篇
耳鼻咽喉   2篇
儿科学   48篇
妇产科学   6篇
基础医学   41篇
口腔科学   10篇
临床医学   25篇
内科学   127篇
皮肤病学   23篇
神经病学   36篇
特种医学   2篇
外科学   66篇
综合类   2篇
预防医学   10篇
眼科学   1篇
药学   52篇
肿瘤学   38篇
  2022年   5篇
  2021年   7篇
  2016年   3篇
  2015年   9篇
  2014年   9篇
  2013年   8篇
  2012年   6篇
  2011年   6篇
  2010年   8篇
  2009年   7篇
  2007年   9篇
  2006年   26篇
  2005年   7篇
  2004年   14篇
  2003年   8篇
  2002年   7篇
  2001年   3篇
  1999年   4篇
  1998年   21篇
  1997年   24篇
  1996年   32篇
  1995年   24篇
  1994年   21篇
  1993年   21篇
  1992年   16篇
  1991年   9篇
  1990年   10篇
  1989年   2篇
  1988年   7篇
  1987年   9篇
  1986年   9篇
  1985年   17篇
  1984年   4篇
  1983年   4篇
  1981年   7篇
  1980年   8篇
  1979年   7篇
  1978年   6篇
  1977年   2篇
  1970年   2篇
  1969年   3篇
  1967年   2篇
  1960年   2篇
  1959年   2篇
  1958年   15篇
  1957年   15篇
  1956年   13篇
  1955年   10篇
  1954年   9篇
  1948年   2篇
排序方式: 共有489条查询结果,搜索用时 15 毫秒
481.
Tetrahydro-ß-carbohnes. formed from aldehydes andtryptaminc. have been suggested as potential biochemical markersfor alcoholism. The excretion of 1-methyl-1.2.3.4-tctrahydro-ß-carbolinc(MTBC) and 1.2.3.4 [EC] -tetrahydro-ß-carbohne (TBC) inhuman urine was studied to assess their possible origin. Inurine collected after a drinking party. MTBC and TBC were excretedin significantly higher concentrations compared with sobriety.MTBC and TBC were contained in beer and wine at ng/ml levels,but not in distillate alcoholic beverages such as whisky, brandy,gin. etc The urinary excretion of MTBC and TBC was elevatedafter drinking beer, whereas no change was observed after drinkingwhisky. When a human subject was orally administered with dcuteratedL-tryptophan together with drinking whisky, deuterated tryptaminewas increasingly excreted in urine. However, no increase wasfound in urinary deuterated MTBC. These results indicate thatthe urinary excretion of MTBC and TBC associated with alcoholingestion does not imply promotion of their in vivo formation,but the exogenous supply of MTBC and TBC by drinking alcoholicbeverages containing them.  相似文献   
482.
A 5 year old boy had a spiky fever accompanied by a mild pharyngitis, cervical lymphadenopathy and hepatosplenomegaly. Laboratory findings revealed leukocytosis with 26% atypical lymphocytes, and liver dysfunction. A chest X-ray showed pneumonia and a considerable amount of pleural effusion. Serum antibody titers for cytomegalovirus (CMV) were elevated significantly and CMV-DNA (polymerase chain reaction) was detected in the pleural effusion. Only 13 cases of pleural effusion associated with infectious mononucleosis have been reported previously in the literature, but there was no documentation that proved CMV infection. The case reported here suggests that the pleural effusion was caused by the infiltration of mononuclear cells to the pleura as a result of systemic inflammation, and the possible alternative of host immune response against CMV was related to recent Varicella zoster virus infection.  相似文献   
483.
A 9 year old boy, born to a phenotypically normal, non-consanguineous couple was referred for clinical examination due to radio-ulnar synostosis. We made cytogenetic analyses to investigate the genotype-phenotype correlation. Chromosomal studies on the boy and his father revealed a very small Y chromosome in both cases, probably due to loss of the heterochromatic long arm segment. Repeated cytogenetic analysis of the boy was made, using QFQ, CBG, DA/DAPI and fluorescence in situ hybridization (FISH) methods with DYZ1 and DYZ3 probes. The results showed a likely mosaicism of cell lines with either a small Y or a normal Y found in the boy. The small Y appeared to be composed of double centromeric regions, without the heterochromatic segment of the long arm of the Y chromosome. The father refused re-analysis. These findings indicate an inherent instability of the Y chromosome resulting in a familial small Y. The radio-ulnar synostosis may be associated with excessive Y short arms.  相似文献   
484.
CYLIC PEPTIDES     
Two diastereomeric cyclic tetrapeptides with a sequence of cyclo (-D (and L)-Tyr (Me)-L-Ile-L-Pro-L-Leu-) (ID and IL) have been synthesized, which are simplified analogs of a phytotoxic peptide Cyl-2, and contain an L-proline and an L-leucine residue in place of an L-pipecolic acid and a 2-amino-8-oxo-9,10-epoxydecanoic acid residue, respectively, in Cyl-2. The cyclization of the H-D-Tyr(Me)-L-Ile-L-Pro-L-Leu-ONSu proceeded smoothly to give ID in excellent yield (50%), but the cyclization of H-L-Tyr(Me)-L-Ile-L-Pro-L-Leu-ONSu gave IL in much lower yield (10%). Based on the results of 1H- and 13C-n.m.r. studies, differential N-methylation and model buildings of ID, the backbone structure of ID has been proposed to be a unique trans-trans-cis-trans conformation, the L-Ile-L-Pro bond being cis.  相似文献   
485.
ABSTRACT Azosemide produced bent long bones such as wavy ribs in rat fetuses, but these abnormalities could not be found in the adult offspring. In the present study, the morphological sequence from appearance to disappearance of wavy ribs was examined in cartilage-bone double stained specimens of fetuses and pups from mothers treated with azosemide on day 16 of gestation. The first detected change of the skeletal abnormalities was inhibition of bone deposition in the ossification centers of fetuses on day 17 of gestation. A bend first appeared on day 18 of gestation, and consisted of cartilage and portion stained neither alcian blue nor alizarin red S. Ossification began at this stage. From day 19 of gestation onward, ossification progressed toward the ends of the cartilage model including the bent region. The bend disappeared in most pups as bone in the bent region grew on days 10–14 postpartum. The present findings imply that the bend may be caused by difference in growth between cartilaginous and unstained portions, and a surface remodeling of bones may straighten the bend in the subsequent bone growth.  相似文献   
486.
487.
488.
The autologous mixed lymphocyte reaction (auto-MLR) was studied to test the interactions between immunocompetent cells in patients with psoriasis. The auto-MLR in 20 patients with psoriasis was significantly lower than in 16 normal controls. Lower values were found in untreated psoriatic patients than in those in remission following treatment. The values in the latter group were significantly lower than in controls and in six patients with atopic dermatitis in remission. The tendency for an increase in the auto-MLR with a decrease in disease activity was further confirmed in five patients studied before and after treatment. In contrast, the allogeneic lymphocyte reaction (allo-MLR) in psoriatics was similar to that in normal controls.  相似文献   
489.
Tetra-spans transmembrane family (TSTF) members (CD9, CD37, CD53, CD63, CD81 and CD82) have potent effects on cell growth, motility and adhesion in various cells. However, little is known about their expression in human skin. Using immunohistological techniques, we have studied the localization of all six members of TSTF in normal and carcinomatous human keratinocytes. CD9, CD81 and CD82 were expressed in the entire living layers of the epidermis. Their staining pattern was quite similar, and was mainly intercellular with occasional intracellular immunoreactivity. CD53 expression was confined to the intercellular spaces of the upper spinous or granular layer in the normal epidermis. No clear-cut expression of CD63 could be detected in the epidermis. CD37 was not detected at all. Cultured human keratinocytes also expressed CD9, CD81 and CD82 at the surface membrane of cell-cell boundaries. Expression of CD37 and CD53 was negative in cultured keratinocyte, while CD63 was clearly localized in the cytoplasmic lysosomes. An immunoprecipitation assay revealed that α3β1 integrin is molecularly associated with CD9. The expression of CD9, CD81 and CD82 was markedly down-regulated in basal cell carcinoma but not in Bowen's disease. The abundant and differential expression of TSTF molecules and the selective association of CD9 with α3β1 integrin suggest that the TSTF molecules may be involved in the regulation of epidermal differentiation and integrity in vivo.  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