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1.
Cathespin B has been purified 750-fold to apparent homogeneity from human and bovine brain cortex using ammonium sulfate fractionation
(30–70%), chromatography on Sephadex G-100, CM-Sephadex C-50, and concanavalin A-Sepharose. Enzyme was assayed fluorometrically
at pH 4.0 with pyridoxyl-hemoglobin in the presence of 1 mM DTT and 1 mM EDTA. Properties of the enzyme from the two sources
proved to be similar. On disc PAGE the purified preparation produced two bands associated with proteinase activity that are
due to existence of two multiple forms of brain cathepsin B with pI 6.1 and 6.8. The enzyme is completely inactivated by thiol-blocking
reagents, leupeptin, E-64, and demands thiol compounds for its ultimate activity. Z-Phe-Ala-CHN2 is a potent inhibitor of the enzyme (K
2nd=1280 M−1s−1) in contrast to Z-Phe-Phe-CHN2 (K
2nd=264 M−1s−1). pH optimum in the reaction of hydrolysis of Pxy-Hb is 4.0–6.0,K
M(app.) =10−5 M. Cathepsin B splits azocasein: pH optimum 5.0–6.0,K
M(app.)=2.2·10−5 M, but inclusion of urea in the incubation medium depresses the azocaseinolytic activity of the enzyme 1.5-fold. It does
not split Lys-NNap, Arg-NMec and is not inhibited by bestatin. The specific activity of brain cathepsin B with Z-Arg-Arg-NNapOMe
at pH 6.0 is 10-fold higher than with Bz-Arg-NNap, Z-Gly-Gly-Arg-NNap is a poor substrate. With Z-Arg-Arg-NMec and Bz-Phe-Val-Arg-NMec
the specific acitivity is 80 and 35%, respectively of that with Z-Phe-Arg-NMec.
Special Issue dedicated to Dr. Eugene Kreps. 相似文献
2.
Armen H. Tashjian Edward F. Voelkel Lawrence Levine 《Biochemical and biophysical research communications》1977,74(1):199-207
In mice bearing the prostaglandin-producing HSDM1 fibrosarcoma, the plasma concentration of 13,14-dihydro-15-keto-PGE2 was elevated before the development of hypercalcemia, and the magnitude of the rise was greater than that of PGE2. When hydrocortisone, which inhibits synthesis of PGE2 by HSDM1 cells in culture, was administered to tumor-bearing mice, the steroid hormone prevented the rises in plasma PGE2 metabolite and calcium concentrations. At the dose levels used, hydrocortisone did not inhibit the calcium-mobilizing action of parathyroid hormone or the bone resorption-stimulating activity of . These findings are consistent with our hypothesis that the hypercalcemic syndrome in HSDM1 tumor-bearing mice is due to the secretion of PGE2 by the tumor. 相似文献
3.
Priscilla S. Dannies Armen H. Tashijian 《Biochemical and biophysical research communications》1976,70(4):1180-1189
A wheat germ embryo extract was used to translate cytoplasmic RNA isolated from rat pituitary tumor cells (GH-cells). This RNA directed the synthesis of a radioactive product which was precipitated with antiserum specific for rat prolactin. The molecular weight of this immunoprecipitated product was 24,500 as determined by electrophoresis in denaturing gels. Prolactin secreted by intact GH-cells had a molecular weight identical to standard pituitary prolactin, reported to be about 22,500. Our finding that a larger form of prolactin is made by the wheat germ system is similar to results recently described by Maurer, Stone and Gorski (J. Biol. Chem., in press). Thyrotropin-releasing hormone (TRH) stimulates prolactin synthesis in GH-cells, and cytoplasmic RNA isolated from cells treated with TRH directed the synthesis in wheat germ extracts of larger amounts of prolactin than RNA isolated from control cells. The increase in translatable cytoplasmic mRNA for prolactin corresponded to the increase in prolactin synthesis which suggests that the increase in prolactin synthesis in TRH-treated cells is a result of the accumulation of cytoplasmic mRNA for prolactin. 相似文献
4.
Armen A. Ghazarian Megan A. Murphy Maria R. Khan Brit I. Saksvig Sean F. Altekruse 《PloS one》2013,8(11)
Purpose
To examine the associations between area-level socioeconomic attributes and stage of esophageal adenocarcinoma diagnoses in 16 SEER cancer registries during 2000-2007.Methods
Odds ratios (OR) and 95% confidence intervals (CI) were calculated using multivariable logistic regression models to assess the relationship between distant-stage esophageal adenocarcinoma and individual, census tract, and county-level attributes.Results
Among cases with data on birthplace, no significant association was seen between reported birth within versus outside the United States and distant-stage cancer (adjusted OR=1.02, 95% CI: 0.85-1.22). Living in an area with a higher percentage of residents born outside the United States than the national average was associated with distant-stage esophageal adenocarcinoma; census tract level: >11.8%, (OR=1.10, 95% CI:1.01–1.19), county level: >11.8%, (OR=1.14, 95% CI:1.05-1.24). No association was observed between median household income and distant-stage cancer at either census tract or county levels.Conclusion
The finding of greater odds of distant-stage esophageal adenocarcinoma among cases residing in SEER areas with higher proportion of non-U.S. Natives suggests local areas where esophageal cancer control efforts might be focused. Missing data at the individual level was a limitation of the present study. Furthermore, inconsistent associations with foreign birth at individual- versus area-levels cautions against using area-level attributes as proxies for case attributes. 相似文献5.
Glycerol and glucose fermentation redox routes by Escherichia coli and their regulation by oxidizing and reducing reagents were investigated at different pHs. Cell growth was followed by decrease of pH and redox potential (E h ). During glycerol utilization at pH 7.5 ?pH, the difference between initial and end pH, was lower compared with glucose fermentation. After 8 h growth, during glycerol utilization E h dropped down to negative values (?150 mV) but during glucose fermentation it was positive (+50 mV). In case of glycerol H2 was evolved at the middle log phase while during glucose fermentation H2 was produced during early log phase. Furthermore, upon glycerol utilization, oxidizer potassium ferricyanide (1 mM) inhibited both cell growth and H2 formation. Reducing reagents dl-dithiothreitol (3 mM) and dithionite (1 mM) inhibited growth but stimulated H2 production. The findings point out the importance of reductive conditions for glycerol fermentation and H2 production by E. coli. 相似文献
6.
Valeri B. Arakelyan Poghos O. Vardevanyan Zaven E. Navoyan Marine A. Parsadanyan Gohar G. Hovhannesyan Armen T. Karapetian 《Journal of biomolecular structure & dynamics》2013,31(2):330-335
In the present work, the adsorption kinetics of extended ligands on DNA duplexes at small fillings when molecules of DNA duplexes are on the underlayer within diffusion layer has been investigated. Both diffusion of ligands in solution (diffusion stage) and adsorption of ligands (kinetic stage) are taken into consideration at adsorption of ligands on DNA duplexes. Nonlinear system of differential equations describing adsorption of ligands where not only diffusion stage but also kinetic stage is taken into account, is obtained, moreover the equations allow localizing duplexes in arbitrary place within diffusion layer. Numeric solution of the equations makes possible to investigate the filling kinetics of DNA duplexes by ligands depending on parameters controlling adsorption process. It has been shown that depending on relation between adsorption parameters different kinetic regimes of adsorption – kinetic, complex, and diffusion regimes may be realized. 相似文献
7.
Poghos O. Vardevanyan Valeri B. Arakelyan Ara P. Antonyan Zhanna H. Mukhaelyan Lilit A. Hambardzumyan Armen T. Karapetian 《Journal of biomolecular structure & dynamics》2013,31(1)
The binding of ligands with DNA is a key moment in a whole range of cellular processes that provide not only the normal cell vital activity but also the development of some pathological processes. Depending on ligand type, structure of DNA adsorption centers, and physical–chemical conditions of the surrounding, the ligand may bind to DNA by several modes [1]. Particularly, adsorption isotherm of multimodal ligands binding to DNA in Scatchard’s coordinates has a concave shape with two brightly expressed linear areas in the region of small fillings. The analysis of such type of adsorption isotherm for determining of important binding parameters such as binding constant and number of adsorption centers (the part of DNA polymer with which one ligand molecule binds) presents difficulties. Practically in all cases, the analysis of such adsorption isotherm is carried out by linear parts of curves. Such analysis mode of experimental points is approximate method, since all registered of experimental points are roughly divided into two groups and they are treated by linear binding isotherm and therefore the binding parameters are determined. In the present work, the non-linear adsorption isotherm in Scatchard‘s coordinates is obtained which allowed, provided, the more precise treatment of all experimental points by unique curve which includes linear regions as well. Such mode of treatment of experimental points makes more precise the determination of not only binding constant and number of adsorption centers that correspond to the one ligand molecule binding, but also additional binding parameter – a proportion of adsorption centers of each binding to DNA type of multimodal ligand. 相似文献
8.
The rotary proton- and sodium-translocating ATPases are reversible molecular machines present in all cellular life forms that couple ion movement across membranes with ATP hydrolysis or synthesis. Sequence and structural comparisons of F- and V-type ATPases have revealed homology between their catalytic and membrane subunits, but not between the subunits of the central stalk that connects the catalytic and membrane components. Based on this pattern of homology, we propose that these ATPases originated from membrane protein translocases, which, themselves, evolved from RNA translocases. We suggest that in these ancestral translocases, the position of the central stalk was occupied by the translocated polymer. 相似文献
9.
World Journal of Microbiology and Biotechnology - Karst caves, considering to be the “arks” of biodiversity, often contain high levels of endemism. In the present study, the... 相似文献
10.
Libraries from natural product-like scaffolds 总被引:1,自引:0,他引:1
Boldi AM 《Current opinion in chemical biology》2004,8(3):281-286
Natural products are an attractive source of varied structures that exhibit potent biological activities, and desirable pharmacological profiles. Since the relatively recent advent of high-throughput organic synthesis in the drug discovery process, several design approaches have been applied to the construction of screening libraries. Libraries of natural-product derivatives, natural-product-like compounds prepared by total synthesis, and libraries derived from natural-products are several types that have been reported. 相似文献