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21.
Differential scanning calorimetry (DSC) and film balance measurements were performed to study the interactions of the GalNAcbeta1-->4(NeuAcalpha2-->3)Galbeta1-->4Glc1 -->1'Cer (GM2)-activator protein with phospholipid/ganglioside vesicles and monolayers. The nonglycosylated form of the GM2-activator protein, added to unilamellar lipid vesicles of different composition, causes differential effects on the gel to liquid-crystalline phase transition peaks. The phase transition temperature (Tm) of pure dimyristoylglycerophosphocholine (DMPC) bilayer is slightly decreased. When lipids which specifically bind the GM2-activator protein are incorporated into the vesicles (e.g. a sulfatide or gangliosides) a shoulder in the thermograms at higher temperatures is observed, indicating an increase of the stability of the gel phase in relation to the liquid-crystalline phase. We also studied the surface activity of a glycosylated and a nonglycosylated GM2-activator protein at the air-water interface. The glycosylated form showed a slightly lower surface activity than the GM2-activator protein without oligosaccharide moiety. When the GM2-activator protein is added to the sub-phase of a surface covered with a lipid monolayer, it can only insert into the monolayer and reach the air-water interface below a monolayer pressure of 25 mN.m-1, depending on the lipid composition, and not when the monolayers are at the bilayer equivalence pressure of 30-35 mN.m-1. Particularly for Galbeta1-->3GalNAcbeta1-->4(NeuAcalpha2-->3)Galbeta 1-->4Glc1-->1'Cer (GM1) and GM2 containing films, the critical pressures (picrit) when no additional increase in surface pressure is observed after addition of the protein into the subphase, are much lower. This leads to the conclusion that binding of the GM2 activator protein to the ganglioside headgroups prevents the protein from reaching the air-water interface. The protein is then located preferentially at the lipid-water interface and cannot penetrate into the chain region. 相似文献
22.
Janis E. Lochner Geoffrey V. F. Seaman Philip Blume Arthur Malley 《Cell biochemistry and biophysics》1982,4(1):15-24
Concanavalin A, at extremely low concentrations, will produce significant increases in the electrophoretic mobility of murine
splenic T lymphocytes. It has been established that the alteration in cellular surface charge is mediated by a factor produced
by those lymphocytes that have reacted directly with con A. We originally conjectured that the mobility change might be the
consequence of an alteration in the distribution of the charged moieties of membrane glycoproteins. The results of experiments
conducted at low temperature raise some questions about this mechanism. Further experiments have been performed to establish
the nature of the physicochemical alterations in the peripheral zone of the factor-stimulated lymphocytes that are manifest
as changes in cellular surface charge. The results of these studies indicate that, subsequent to the interaction of T lymphocytes
with con A, there is a reduction in the number of positively charged amino groups effective at the electrophoretic surface
of the cells. 相似文献
23.
Ya. B. Blume 《Cytology and Genetics》2017,51(2):83-86
This survey paper contains a brief analysis of publications included in the current issue of the scientific journal Cytology and Genetics dedicated to its 50th anniversary. These papers reflect scientific achievements of their authors in the field of genetics and cell biology and underline the potential of these two biological disciplines, forming the double helix of the journal. 相似文献
24.
三氧化二砷对食管癌细胞增殖和热休克蛋白70表达的影响 总被引:2,自引:0,他引:2
目的:研究三氧化二砷(As2O3)对食管癌细胞增殖和热休克蛋白70(HSP70)表达的影响。方法:通过相差显微镜、流式细胞术、免疫细胞化学染色和免疫印迹分析等方法观察As2O3对人食管癌细胞株EC1的作用效果和作用机制。结果:与对照组相比,经2μmol/L和5μmol/Las2O3作用的细胞出现明显的生长抑制,G2/M期细胞比例增加;2μmol/Las2O3作用48h后经Ecl细胞HSP70(heat shock protein70)及HSC70(heat shock cognate protein70)表达均增加。结论:As2O3诱导食管癌细胞G2/M期阻滞抑制细胞增殖和生长;HSP70的升高是细胞对As2O3作用后出现的应激反应,并与细胞周期阻滞相关。 相似文献
25.
Blume A Ghaderi D Liebich V Hinderlich S Donner P Reutter W Lucka L 《Protein expression and purification》2004,35(2):387-396
UDP-GlcNAc 2-epimerase/ManNAc kinase is the key enzyme of sialic acid biosynthesis in mammals. Its functional expression is a prerequisite for early embryogenesis and for the synthesis of several cell recognition motifs in adult organism. This bifunctional enzyme is involved in the development of different diseases like sialuria or hereditary inclusion body myopathy. For a detailed understanding of the enzyme, large amounts of the pure active protein are needed. Different heterologous cell systems were therefore analyzed for the enzyme, which was found to be functionally expressed in Escherichia coli, the yeast strains Saccharomyces cerevisiae and Pichia pastoris, and insect cells. In all these cell types, the expressed enzyme displayed both epimerase and kinase activities. In E. coli, up to 2mg protein/l cell culture was expressed, in yeast cells only 0.4mg/L, while up to 100mg/L, were detected in insect cells. In all three cell systems, insoluble protein aggregates were also observed. Purification from E. coli resulted in 100microg/L pure and structurally intact protein. For insect cells, purification methods were established which resulted in up to 50mg/L pure, soluble, and active protein. In summary, expression and purification of the UDP-GlcNAc 2-epimerase/ManNAc kinase in Sf-900 cells can yield the milligram amounts of protein required for structural characterization of the enzyme. However, the easier expression in E. coli and yeast provides sufficient quantities for enzymatic and kinetic characterization. 相似文献
26.
Zhou YP Marlen K Palma JF Schweitzer A Reilly L Gregoire FM Xu GG Blume JE Johnson JD 《The Journal of biological chemistry》2003,278(51):51316-51323
27.
28.
To many, the foundations of statistical inference are cryptic and irrelevant to routine statistical practice. The analysis of 2 x 2 contingency tables, omnipresent in the scientific literature, is a case in point. Fisher''s exact test is routinely used even though it has been fraught with controversy for over 70 years. The problem, not widely acknowledged, is that several different p-values can be associated with a single table, making scientific inference inconsistent. The root cause of this controversy lies in the table''s origins and the manner in which nuisance parameters are eliminated. However, fundamental statistical principles (e.g., sufficiency, ancillarity, conditionality, and likelihood) can shed light on the controversy and guide our approach in using this test. In this paper, we use these fundamental principles to show how much information is lost when the tables origins are ignored and when various approaches are used to eliminate unknown nuisance parameters. We present novel likelihood contours to aid in the visualization of information loss and show that the information loss is often virtually non-existent. We find that problems arising from the discreteness of the sample space are exacerbated by p-value-based inference. Accordingly, methods that are less sensitive to this discreteness - likelihood ratios, posterior probabilities and mid-p-values - lead to more consistent inferences. 相似文献
29.
Janaína A Couto Karina LA Saraiva Cleiton D Barros Daniel P Udrisar Christina A Peixoto Juliany SB César Vieira Maria C Lima Suely L Galdino Ivan R Pitta Maria I Wanderley 《Reproductive biology and endocrinology : RB&E》2010,8(1):13
Background
The present study was designed to examine the effect of chronic treatment with rosiglitazone - thiazolidinedione used in the treatment of type 2 diabetes mellitus for its insulin sensitizing effects - on the Leydig cell steroidogenic capacity and expression of the steroidogenic acute regulatory protein (StAR) and cholesterol side-chain cleavage enzyme (P450scc) in normal adult rats. 相似文献30.
H C Wang B Beer D Sassano A J Blume M R Ziai 《The International journal of biochemistry》1991,23(3):271-276
1. Gene expression in Xenopus oocytes is now an integral part of many molecular cloning strategies. 2. For some genes, such as those encoding the ion channels, this system has emerged as the only available means to authenticate and examine the biological activities of the cloned DNA. 3. This review discusses some of the current applications of Xenopus oocytes in modern molecular biology. 相似文献