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41.
The absorption spectra of polyadenylic acid (polyA) radicals in N20 saturated aqueous solution have been measured as a function of time (up to 15 s) following an 0.4μS electron pulse. The spectra and their changes were analysed by comparison with those from monomeric adenine derivatives (nucleosides and nucleotides) which had been studied by Steenken.1
The reaction of OH· radicals with the adenine moiety in poly A results in the formation of two hvdroxvl adducts at the positions C-4 [polyA40H·] and C-8 [polyA80H·]. Each OH-adduct undergoes a unimol-ecular transformation reaction before any bimolecular or other unimolecular decay occurs. These reactions are characterized by different rate constants and pH dependencies. The polyA40H· adduct undergoes a dehydration reaction to yield a neutral N6 centered radical (rate constant Kdeh= 1.4 × 104s-1 at pH7.3). This reaction is strongly inhibited by H+. In comparison with the analogous reactions in adenosine phosphates, the kinetic pK value for its inhibition is two pH units higher. This shift is the result of the counter ion condensation or double-strand formation. The polyA80H· adduct undergoes an imidazole ring opening reaction to yield an enol type of formamidopyrimidine radical with the resulting base damage (kr.o. = 3.5 × 104 s -1 at pH7.3). This reaction in contrast is strongly catalysed by H+and OH-, similar as for adenosine but different compared to the nucleotides. 相似文献
The reaction of OH· radicals with the adenine moiety in poly A results in the formation of two hvdroxvl adducts at the positions C-4 [polyA40H·] and C-8 [polyA80H·]. Each OH-adduct undergoes a unimol-ecular transformation reaction before any bimolecular or other unimolecular decay occurs. These reactions are characterized by different rate constants and pH dependencies. The polyA40H· adduct undergoes a dehydration reaction to yield a neutral N6 centered radical (rate constant Kdeh= 1.4 × 104s-1 at pH7.3). This reaction is strongly inhibited by H+. In comparison with the analogous reactions in adenosine phosphates, the kinetic pK value for its inhibition is two pH units higher. This shift is the result of the counter ion condensation or double-strand formation. The polyA80H· adduct undergoes an imidazole ring opening reaction to yield an enol type of formamidopyrimidine radical with the resulting base damage (kr.o. = 3.5 × 104 s -1 at pH7.3). This reaction in contrast is strongly catalysed by H+and OH-, similar as for adenosine but different compared to the nucleotides. 相似文献
42.
A conventional Clark-type O2 probe was used to determine N2O concentrations in suspensions. At a polarizing voltage of–0.95 V versus the reference Ag/AgCl electrode, the probe is almost half as sensitive for N2O as for O2, and the detection limit is less than 1 M N2O. The probe can also be used to determine NO for which the suitable polarizing voltage is–0.7 V. The method was successfully applied for continuously recording dissimilatory formation or utilization of N2O by intactAzospirillum brasilense Sp 7, NO production by extracts from this bacterium, and N2O reduction catalyzed by nitrogenase in intactKlebsiella pneumoniae. It is concluded that the probe is useful for measuring N2O or NO contents in bacterial suspensions when the O2 level is zero or kept constant during the assays. 相似文献
43.
Imadul Islam Shendong Yuan Christopher W. West Marc Adler Ulrich Bothe Judi Bryant Zheng Chang Kieu Chu Kumar Emayan Giovanna Gualtieri Elena Ho David Light Cornell Mallari John Morser Gary Phillips Caralee Schaefer Drew Sukovich Marc Whitlow Brad O. Buckman 《Bioorganic & medicinal chemistry letters》2018,28(20):3372-3375
We report here the design and synthesis of a novel series of benzylamines that are potent and selective inhibitors of uPA with promising oral availability in rat. Further evaluation of one representative (ZK824859) of the new structural class showed that this compound lowered clinical scores when dosed in either acute or chronic mouse EAE models, suggesting that uPA inhibitors of this type could be useful for the treatment of multiple sclerosis. 相似文献
44.
Achim Sokolowski Heiko Leutbecher Thomas Weyhermüller Robert Schnepf Eberhard Bothe Eckhard Bill Peter Hildebrandt K. Wieghardt 《Journal of biological inorganic chemistry》1997,2(4):444-453
The reaction of the macrocycles 1,4,7-tris (3,5-di-tert-butyl-2-hydroxy-benzyl)-1,4,7-triazacyclononane, L1H3, or 1,4,7-tris(3-tert-butyl-5-methoxy-2-hydroxy-benzyl)-1,4,7-triazacyclononane, L2H3, with Cu(ClO4)2·6H2O in methanol (in the presence of Et3N) affords the green complexes [CuII(L1H)] (1), [CuII(L2H)]·CH3OH (2) and (in the presence of HClO4) [CuII(L1H2)](ClO4) (3) and [CuII(L2H2)] (ClO4) (4). The CuII ions in these complexes are five-coordinate (square-base pyramidal), and each contains a dangling, uncoordinated pendent
arm (phenol). Complexes 1 and 2 contain two equatorially coordinated phenolato ligands, whereas in 3 and 4 one of these is protonated, affording a coordinated phenol. Electrochemically, these complexes can be oxidized by one electron,
generating the phenoxyl-copper(II) species [CuII(L1H)]+ ·, [Cu(L2H)]+ ·, [CuII(L1H2)]2+ ·, and [CuII(L2H2)]2+ ·, all of which are EPR-silent. These species are excellent models for the active form of the enzyme galactose oxidase (GO).
Their spectroscopic features (UV-VIS, resonance Raman) are very similar to those reported for GO and unambiguously show that
the complexes are phenoxyl-copper(II) rather than phenolato-copper(III) species.
Received: 10 February 1997 / Accepted: 7 April 1997 相似文献
45.
Extracts from the nitrogen fixing blue-green algaAnabaena cylindrica catalyse a pyruvate decarboxylation, which is dependent on ferredoxin and stimulated by coenzyme A, ATP and a SH-protecting compound. This pyruvate clastic reaction is completely reversible: The net synthesis of pyruvate requires CO2, acetyl-coenzyme A and reduced ferredoxin. Preparations fromAnabaena cylindrica also catalyse the exchange reaction between CO2 and the carboxyl group of pyruvate. Thus the enzyme fromAnabaena cylindrica has essentially all the characteristics known for the pyruvate: ferredoxin oxidoreductase from anaerobic bacteria.The activity of the pyruvate: ferredoxin oxidoreductase inAnabaena grown with ammonia is lower than one-fifth of that in cells grown with molecular nitrogen or nitrate as the nitrogen source. From this, it will be concluded that a physiological role of the reaction is to generate reduced ferredoxin for the assimilation of nitrogen to ammonia. The pyruvate synthesis is probably not physiological inA. cylindrica.In addition, extracts fromA. cylindrica also catalyse a ferredoxin dependent decarboxylation of -ketoglutarate. It is not yet clear, whether this ketoglutarate cleavage has a function inA. cylindrica. 相似文献
46.
A Sghaier-Ayadi M Feki I Bezrati-Ben Ayed O Abene MK Ben Fredj K Kaabachi A Chaouachi 《Biology of sport / Institute of Sport》2015,32(4):281-287
Recent reports suggest that hypovitaminosis D in athletes is as common as in the general population. This study was devised to examine vitamin D status and determinants of deficiency in athletes living in a sunny country (Tunisia). One hundred and fifty national elite athletes, training outdoors (n = 83) or indoors (n = 67), were enrolled from January to February 2012. Plasma 25-hydroxyvitamin D was measured by radioimmunoassay. Concentrations were between 50 and 75 nmol · l-1 in 21.3% of participants, between 25 and 50 nmol · l-1 in 55.3% of participants and <25 nmol · l-1 in 14.7% of participants. The concentrations were significantly lower in indoor athletes than outdoor athletes (36.2±19.0 nmol · l-1 vs. 49.1±19.2 nmol · l-1; p < 0.001). In multivariate analysis, vitamin D deficiency (25-hydroxyvitamin D <50 nmol · l-1) was associated with indoor sports [multi-adjusted odds ratio (95% confidence interval), 5.03 (1.64-15.4); p = 0.005], female gender [3.72 (1.44-9.65); p = 0.007] and age < 18 years [2.40 (1.01-5.85); p = 0.05]. Athletes living in sun-rich environments are exposed to a high risk of vitamin D inadequacy. Given the importance of vitamin D in health and athletic ability, targeting sufficient levels of plasma 25-hydroxyvitamin D in athletes is well justified. 相似文献
47.
The formation of multinucleated muscle cells through cell-cell fusion is a conserved process from fruit flies to humans. Numerous studies have shown the importance of Arp2/3, its regulators, and branched actin for the formation of an actin structure, the F-actin focus, at the fusion site. This F-actin focus forms the core of an invasive podosome-like structure that is required for myoblast fusion. In this study, we find that the formin Diaphanous (Dia), which nucleates and facilitates the elongation of actin filaments, is essential for Drosophila myoblast fusion. Following cell recognition and adhesion, Dia is enriched at the myoblast fusion site, concomitant with, and having the same dynamics as, the F-actin focus. Through analysis of Dia loss-of-function conditions using mutant alleles but particularly a dominant negative Dia transgene, we demonstrate that reduction in Dia activity in myoblasts leads to a fusion block. Significantly, no actin focus is detected, and neither branched actin regulators, SCAR or WASp, accumulate at the fusion site when Dia levels are reduced. Expression of constitutively active Dia also causes a fusion block that is associated with an increase in highly dynamic filopodia, altered actin turnover rates and F-actin distribution, and mislocalization of SCAR and WASp at the fusion site. Together our data indicate that Dia plays two roles during invasive podosome formation at the fusion site: it dictates the level of linear F-actin polymerization, and it is required for appropriate branched actin polymerization via localization of SCAR and WASp. These studies provide new insight to the mechanisms of cell-cell fusion, the relationship between different regulators of actin polymerization, and invasive podosome formation that occurs in normal development and in disease. 相似文献
48.
Denecke M Eilmus S Röder N Roesch C Bothe H 《Applied microbiology and biotechnology》2012,93(4):1725-1734
The diversity of the microbial community was identified in two lab-scale, ideally mixed sequencing batch reactors which were
run for 115 days. One of the reactors was intermittently aerated (2 h aerobically/2 h anaerobically) whereas the other was
consistently aerated. The amount of biomass as dry matter, the degradation of organic carbon determined by chemical oxygen
demand and nitrogen-degradation activity were followed over the operation of the two reactors and did not show significant
differences between the two approaches at the end of the experiment. At this point, the composition of the microbial community
was determined by a terminal restriction fragment length polymorphism approach using multiple restriction enzymes by which
organisms were retrieved to the lowest taxonomic level. The microbial composition was then significantly different. The species
richness was at least five-fold higher in the intermittently aerated reactor than in the permanently kept aerobic approach
which is in line with the observation that ecosystem disturbances result in higher diversity. 相似文献
49.
Guma MK Abdeldaim Kristoffer Strålin Jens Korsgaard Jonas Blomberg Christina Welinder-Olsson Björn Herrmann 《BMC microbiology》2010,10(1):310
Background
Streptococcus pneumoniae and Haemophilus influenzae cause pneumonia and as Neisseria meningitidis they are important agents of meningitis. Although several PCR methods have been described for these bacteria the specificity is an underestimated problem. Here we present a quantitative multiplex real-time PCR (qmPCR) for detection of S. pneumoniae (9802 gene fragment), H. influenzae (omp P6 gene) and N. meningitidis (ctrA gene). The method was evaluated on bronchoalveolar lavage (BAL) samples from 156 adults with lower respiratory tract infection (LRTI) and 31 controls, and on 87 cerebrospinal fluid (CSF) samples from meningitis patients. 相似文献50.