全文获取类型
收费全文 | 83089篇 |
免费 | 1925篇 |
国内免费 | 48篇 |
出版年
2018年 | 920篇 |
2017年 | 1078篇 |
2016年 | 2810篇 |
2015年 | 6155篇 |
2014年 | 5741篇 |
2013年 | 5480篇 |
2012年 | 4636篇 |
2011年 | 1927篇 |
2010年 | 2048篇 |
2009年 | 2002篇 |
2008年 | 523篇 |
2007年 | 448篇 |
2006年 | 478篇 |
2005年 | 6594篇 |
2004年 | 5290篇 |
2003年 | 3489篇 |
2002年 | 1058篇 |
2001年 | 1073篇 |
2000年 | 306篇 |
1999年 | 1459篇 |
1998年 | 319篇 |
1997年 | 161篇 |
1992年 | 1917篇 |
1991年 | 2009篇 |
1990年 | 2071篇 |
1989年 | 1996篇 |
1988年 | 1953篇 |
1987年 | 1811篇 |
1986年 | 1625篇 |
1985年 | 1652篇 |
1984年 | 1090篇 |
1983年 | 833篇 |
1982年 | 458篇 |
1981年 | 423篇 |
1980年 | 368篇 |
1979年 | 1075篇 |
1978年 | 760篇 |
1977年 | 608篇 |
1976年 | 631篇 |
1975年 | 874篇 |
1974年 | 994篇 |
1973年 | 1005篇 |
1972年 | 953篇 |
1971年 | 928篇 |
1970年 | 820篇 |
1969年 | 830篇 |
1968年 | 734篇 |
1967年 | 751篇 |
1966年 | 584篇 |
1965年 | 431篇 |
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
51.
Endom Ismail Omimah Khaled Jaber Nofal Rajalingham Sakthiswary Syahrul Sazliyana Shaharir Radhika Sridharan 《PloS one》2016,11(4)
ObjectiveInterleukin-1 receptor antagonist (IL-1Ra) acts as an inhibitor of IL-1; which is one of the culprit cytokines in rheumatoid arthritis (RA). Although +2018 polymorphism of IL-1Ra has been implicated in the pathogenesis of RA, its importance remains poorly understood. Hence, the purpose of this study was to determine the clinical significance of interleukin-1 receptor antagonist (IL-1Ra) +2018 polymorphism in RA.MethodsPolymerase chain reaction (PCR) and sequencing were used to determine the genotypes of the IL-1Ra +2018 for 77 RA patients and 18 healthy controls. All RA patients were assessed for the disease activity score that includes 28 joints (DAS28) and radiographic disease damage based on Modified Sharp Score (MSS).ResultsThe frequency of the T/T and C/T genotypes did not differ significantly (p = 0.893) between the RA patients and the controls. The C/T genotype had significantly higher mean disease activity (DAS 28) and disease damage (MSS) scores with p values of 0.017 and 0.004, respectively. Additionally, the ESR (erythrocyte sedimentation rate), CRP (C-reactive protein), the number of swollen and tender joints were higher for the C/T individuals. On multivariate analysis the CRP, swollen joint count and MSS remained significant with the following p values i.e. 0.045, 0.046 and less than 0.05.ConclusionsC/T genotype of IL-1Ra +2018 prognosticates more aggressive disease in RA. 相似文献
52.
E Ortega Rincón J M Marchena J J García A Schmidt T Schulz I Malpica A B Rodríguez C Barriga H Michna H L?tzerich 《Journal of applied physiology》2001,91(3):1067-1072
Flow cytometer measurements were made of the basal variations in peripheral blood functional monocytes and granulocytes over the course of a training season (January to November) of a cycling team. Parallel determinations were made of plasma concentration of catecholamines (chromatography) and cortisol (RIA) in a search for neuroendocrine markers. The results showed the greatest phagocytic capacity to occur in the central months (March, May, and July), coinciding with the greatest number and highest level of competitive events with good correlation with a peak in epinephrine during these months (r(2) = 0.998 for monocytes and r(2) = 0.674 for granulocytes). No good correlations were found between phagocytosis and norepinephrine or cortisol. The highest values for phagocytosis and epinephrine concentration were found in May. These results suggest that blood epinephrine concentration could be a good neuroendocrine marker of sportspeople's phagocytic response. 相似文献
53.
54.
Following treatment of hen erythrocyte nuclei with dimethyl 3,3'-dithiobispropionimidate, dimers between histones H1a, H1b, and H5 were extracted with 5% perchloric acid. They resolved electrophoretically into four sub-bands and these were identified by non-reducing/reducing gel electrophoresis. The H5-H5 homodimer species was purified by gel electrophoresis and was treated sequentially with BrCN and dithiothreitol. The pattern of resulting fragments indicates that cross-links were mainly formed between the COOH-terminal portions and at a significantly lower frequency between the COOH-terminal and the NH2-terminal portions. 相似文献
55.
H Vaer?y F Nyberg H Franzén L Terenius 《Biochemical and biophysical research communications》1987,148(1):24-30
Enzyme activity capable of converting the glycine-extended substance P precursor, substance P-Gly12, into substance P was purified from human cerebrospinal fluid. The conversion reaction was monitored by radioimmunoassay measurement of substance P formation. The chemical identity of the product was verified by reversed-phase HPLC. The enzyme reaction was stimulated by Cu(II) ion and ascorbic acid and inhibited by the presence of diethyldithiocarbamate. By HPLC molecular sieving, the major enzyme activity appeared as a protein of 26,000 molecular weight. 相似文献
56.
57.
P V Sergeev A S Dukhanin A V Seme?kin 《Biulleten' eksperimental'no? biologii i meditsiny》1987,104(12):678-681
In has been shown that cortisol immobilized on polyvinylpyrrolidone (PVP-GC) affects cyclic AMP production stimulated by adenosine and isoproterenol in rat thymocytes. This effect of PVP-GC is specific for cortisol: antiglucocorticoid progesterone (at a concentration of 10(-5) M) inhibited completely the action of PVP-GC on the intracellular cAMP level. It is suggested that cortisol effect on cAMP production is one of the mechanisms of glucocorticoid hormone action in target cells. 相似文献
58.
59.
60.
Natural killer T (NKT) cells are a component of innate and adaptive immune systems implicated in immune, autoimmune responses and in the control of obesity and cancer. NKT cells develop from common CD4+ CD8+ double positive (DP) thymocyte precursors after the rearrangement and expression of T cell receptor (TCR) Vα14-Jα18 gene. Temporal regulation and late appearance of Vα14-Jα18 rearrangement in immature DP thymocytes has been demonstrated. However, the precise control of lifetime of DP thymocytes in vivo that enables distal rearrangements remains incompletely defined. Here we demonstrate that T cell factor (TCF)-1, encoded by the Tcf7 gene, is critical for the extended lifetime of DP thymocytes. TCF-1-deficient DP thymocytes fail to undergo TCR Vα14-Jα18 rearrangement and produce significantly fewer NKT cells. Ectopic expression of Bcl-xL permits Vα14-Jα18 rearrangement and rescues NKT cell development. We report that TCF-1 regulates expression of RORγt, which regulates DP thymocyte survival by controlling expression of Bcl-xL. We posit that TCF-1 along with its cofactors controls the lifetime of DP thymocytes in vivo. 相似文献