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   176篇
  免费   14篇
  190篇
  2021年   3篇
  2018年   2篇
  2016年   2篇
  2015年   4篇
  2014年   3篇
  2013年   11篇
  2012年   2篇
  2011年   15篇
  2010年   5篇
  2009年   4篇
  2008年   10篇
  2007年   8篇
  2006年   10篇
  2005年   2篇
  2004年   14篇
  2003年   3篇
  2002年   10篇
  2001年   4篇
  2000年   2篇
  1999年   3篇
  1998年   2篇
  1996年   2篇
  1994年   2篇
  1993年   2篇
  1991年   2篇
  1990年   1篇
  1989年   3篇
  1988年   4篇
  1987年   1篇
  1986年   3篇
  1985年   1篇
  1984年   6篇
  1983年   2篇
  1982年   2篇
  1980年   3篇
  1979年   3篇
  1978年   3篇
  1977年   2篇
  1976年   5篇
  1975年   1篇
  1974年   5篇
  1972年   2篇
  1971年   3篇
  1969年   2篇
  1968年   1篇
  1966年   1篇
  1965年   1篇
  1964年   2篇
  1961年   1篇
  1957年   1篇
排序方式: 共有190条查询结果,搜索用时 15 毫秒
91.
ABSTRACT: BACKGROUND: Glioblastoma Multiforme (GBM) is one of the most aggressive primary brain tumors and is associated with a dismal prognosis. The median survival after the primary diagnosis remains poor, even after multimodal treatment approaches. However, a few patients have been reported to have long term survival greater than three years. A number of studies have attempted to define factors capable of predicting long term outcomes in specific patient groups. This article reports the outcomes of a very large group of patients diagnosed with GBM, and analyzes specific prognostic factors known to influence survival in these patients. METHODS: We used the Surveillance, Epidemiology, and End Results (SEER) database of the US National Cancer Institute (NCI) to investigate various patient-related and treatment- related factors that could influence the long term survival in patients diagnosed with glioblastoma. A total of 34,664 patients aged 20 years or older with a diagnosis of GBM during the years 1973 to 2008 were studied. Overall survival outcomes were examined with Kaplan-Meier survival analysis and Cox hazard models. RESULTS: Asian/Pacific Islanders had a better survival compared to the white population (P = <0.001). Patients diagnosed with GBM during the years 2000 to 2008 had a superior survival rate when compared with earlier decades (P = <0 .001). Statistically significant improvements in overall survival were also found for patients who received surgical resections, and adjuvant radiation treatment versus no radiation (P-values <0.001). Young age was also found to be highly predictive of improved overall survival rates when separated into age groups as well as when studied as a continuous variable. CONCLUSIONS: Clinical pretreatment and treatment factors, including young age at diagnosis, Asian/Pacific Islander ethnicity, recent year of diagnosis, surgical resection and the use of adjuvant radiation therapy favorably influence survival in patients diagnosed with glioblastoma. Trial Registration All data were obtained from the United States Surveillance Epidemiology and End Results (SEER) database.  相似文献   
92.

Background  

The NANOG gene is expressed in mammalian embryonic stem cells where it maintains cellular pluripotency. An unusually large family of pseudogenes arose from it with one unprocessed and ten processed pseudogenes in the human genome. This article compares the NANOG gene and its pseudogenes in the human and chimpanzee genomes and derives an evolutionary history of this pseudogene family.  相似文献   
93.
Ascites cells of the 13762 rat mammary adenocarcinoma bind poly(U) in a reaction that is complete within 5 min at 0°C. Poly(U) binding is saturable; the capacity of these cells is 5×107 UMP residues/cell (approx. 2×105 chains/cell). Most [3H]poly(U) bound in the rapid reaction can be recovered in an undergraded state. However, it is rapidly degraded by low concentrations of exogenous pancreatic ribonuclease. The magnitude of binding is independent of temperature and ionic conditions, and is unaffected by metabolic inhibitors or concanavalin A (ConA). Radioactivity presented as [3H]poly(U) tends to co-fractionate with 5′-nucleotidase after homogenization of cells in the media of low ionic strength, but is efficiently released from cells exposed to protein denaturants that effectively fix cellular RNA in situ. Cells pretreated with proteolytic enzymes have sharply reduced capacities to bind poly(U). Autoradiography of cells bearing [3H]poly(U) demonstrates a uniform distribution of radioactivity through the cell population and is consistent with binding to the plasma membrane. These and other results imply that binding of poly(U) to 13762 ascites cells is mediated by protein receptors on the cell surface.  相似文献   
94.
Isolated human erythrocyte membranes crenate when suspended in isotonic medium, but can use MgATP to reduce their net positive curvature, yielding smooth discs and cup forms that eventually undergo endocytosis. An earlier report from this laboratory (Patel, V.P. and Fairbanks, G. (1981) J. Cell Biol. 88, 430-440), has described a phenomenon of ATP-independent shape change in which ghosts prepared by hemolysis and washing in synthetic zwitterionic buffers crenated at 0 degree C, but underwent conversion to smooth discs and cups when warmed in the absence of MgATP. We have further explored the effect of the hemolysis condition on the requirement for ATP in ghost shape change. 25 hemolysis buffers were applied at 10 mM (pH 7.4, 0 degree C). Eight anionic buffers with relatively high ionic strength (e.g., phosphate and diethylmalonic acid (DMA] yielded ghosts requiring ATP for shape change, while two cationic buffers (Bistris and imidazole) and ten synthetic zwitterionic buffers (e.g., Tricine and Hepes) with lower ionic strength produced ghosts that smoothed spontaneously at 30 degrees C. Hemolysis at intermediate ionic strength yielded mixed populations in which spontaneous smoothing was expressed in all-or-none fashion. Maximal ATP-independent shape change was induced by hemolysis at pH 7.3-7.7, while ATP was required after hemolysis at pH less than or equal to 7.1 even when the ionic strength at hemolysis was low. Ghosts requiring ATP could be converted to ATP independence by washing at low ionic strength, but ATP independence could not be reversed readily by washing at high ionic strength. Exposure to low ionic strength at pH greater than 7.1 presumably changes membrane organization in a way that alters the temperature dependence of tensions within the bilayer or skeleton of the composite membrane.  相似文献   
95.
Restoration of the oral commissure   总被引:1,自引:0,他引:1  
  相似文献   
96.
Significant alterations in the spectrin: band 3 and band 4.1a: band 4.1b ratios and an occasional decrease in the peak height of band 4.2 with respect to band 4.1 were found in electrophoretic patterns of red cell membranes from patients with hereditary xerocytosis. Electrophoretic comparison of whole cell, cytoplasm and membrane polypeptides implied that atypical partitioning at hemolysis could account for some, but not all, of the alterations seen in membrane patterns of xerocytes. A decrease in band 4.2 peak height as well as a variation in the profile of band 3 were produced in controls by specific manipulations of the electrophoresis protocol. Metabolic depletion of normal cells produced the type of alterations in bands 3 and 4.1 found in xerocyte membranes, whereas Heinz body production, addition of calcium to the hemolysis buffer and incubation of membranes in detergent under conditions designed to promote proteolysis did not. The presence of a higher peak height of band 4.1b with respect to that of band 4.1a in membranes of patients with various other red cell disorders correlated with an increase in the percentage of reticulocytes in peripheral circulation. The appearance of both band 3 and 4.1 abnormalities in the patterns of control cells which had been enriched in young cells by density gradient centrifugation suggested that these alterations in hemolytic disease are related to the predominance of young cells in the population.  相似文献   
97.

Background  

Chimpanzee dental pulp stem/stromal cells (ChDPSCs) are very similar to human bone marrow derived mesenchymal stem/stromal cells (hBMSCs) as demonstrated by the expression pattern of cell surface markers and their multipotent differentiation capability.  相似文献   
98.
The enzyme inosine triphosphate pyrophosphatase (ITPase) catalyses the pyrophosphohydrolysis of ITP to IMP. ITPase deficiency is a clinically benign autosomal recessive condition characterised by the abnormal accumulation of ITP in erythrocytes. A deficiency of ITPase may predict adverse reactions to therapy with the thiopurine drug 6-mercaptopurine and its prodrug azathioprine. In this study, we examine the frequencies of ITPA polymorphisms in 100 healthy Japanese individuals. The allele frequency of the 94C > A variant in the Japanese sample was 0.135 (Caucasian allele frequency 0.06). The IV2 + 21A > C polymorphism was not found in Japanese (Caucasian allele frequency 0.130). Allele frequencies of the 138G > A, 561G > A and 708G > A polymorphisms were 0.57, 0.18 and 0.06 respectively in the Japanese population, and with the exception of the 138G > A polymorphism, similar to allele frequencies in Caucasians.  相似文献   
99.
Spinal acute opioid tolerance remains mechanistically undercharacterized. Expanded clinical use of direct spinal administration of opioids and other analgesics indicates that studies to further understand spinal mechanisms of analgesic tolerance are warranted. Rodent models of spinal administration facilitate this objective. Specifically, acute spinal opioid tolerance in mice presents a plasticity-dependent, rapid, and efficient opportunity for evaluation of novel clinical agents. Similarities between the pharmacology of acute and chronic spinal opioid tolerance, neuropathic pain, and learning and memory suggest that this model may serve as a high through-put predictor of bioactivity of novel plasticity-modifying compounds.  相似文献   
100.
A genetic linkage map of the vervet monkey (Chlorocebus aethiops sabaeus)   总被引:1,自引:0,他引:1  
The spectacular progress in genomics increasingly highlights the importance of comparative biology in biomedical research. In particular, nonhuman primates, as model systems, provide a crucial intermediate between humans and mice. The close similarities between humans and other primates are stimulating primate studies in virtually every area of biomedical research, including development, anatomy, physiology, immunology, and behavior. The vervet monkey (Chlorocebus aethiops sabaeus) is an important model for studying human diseases and complex traits, especially behavior. We have developed a vervet genetic linkage map to enable mapping complex traits in this model organism and facilitate comparative genomic analysis between vervet and other primates. Here we report construction of an initial genetic map built with about 360 human orthologous short tandem repeats (STRs) that were genotyped in 434 members of an extended vervet pedigree. The map includes 226 markers mapped in a unique order with a resolution of 9.8 Kosambi centimorgans (cM) in the vervet monkey genome, and with a total length (including all 360 markers) of 2726 cM. At least one complex and 11 simple rearrangements in marker order distinguish vervet chromosomes from human homologs. While inversions and insertions can explain a similar number of changes in marker order between vervet and rhesus homologs, mostly inversions are observed when vervet chromosome organization is compared to that in human and chimpanzee. Our results support the notion that large inversions played a less prominent role in the evolution within the group of the Old World monkeys compared to the human and chimpanzee lineages. Electronic supplementary material The online version of this article (doi: ) contains supplementary material, which is available to authorized users.  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