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121.
Structure of the cell wall of lactobacilli. Role of muramic acid phosphate in Lactobacillus fermenti 总被引:9,自引:2,他引:7
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1. The polysaccharide and mucopeptide components of the cell wall of Lactobacillus fermenti, serological group F, were separated by mild conditions of acid hydrolysis; the polysaccharide was composed of glucose and galactose. 2. Soluble cell-wall products were isolated from cell wall lysed by lysozyme and a Streptomyces enzyme preparation. The lysozyme-dissolved fraction contained a greater proportion of mucopeptide. 3. The soluble preparations were heated in dilute acid to hydrolyse the linkage between the polysaccharide and mucopeptide components and then incubated with acid phosphatase. 4. Inorganic phosphate was released from products of Streptomyces enzyme action but not from products of lysozyme action. 5. The phosphate was shown to be present in the mucopeptide as muramic acid phosphate. It is concluded that in the intact wall polysaccharide is joined to muramic acid by a phosphodiester linkage. 相似文献
122.
Zoltán Nemes Krisztina Takács-Novák Gergely Völgyi Klara Valko Szabolcs Béni Zoltán Horváth Bálint Szokol Nóra Breza Judit Dobos Csaba Szántai-Kis Eszter Illyés Sándor Boros Robbert Jan Kok László Őrfi 《Bioorganic & medicinal chemistry letters》2018,28(14):2391-2398
Acute myeloid leukemia (AML) is the most common type of leukemia in adults. Sunitinib, a multikinase inhibitor, was the first Fms-like tyrosine kinase 3 (FLT3) inhibitor clinically used against AML. Off-target effects are a major concern for multikinase inhibitors. As targeted delivery may reduce such undesired side effects, our goal was to develop novel amino acid substituted derivatives of sunitinib which are potent candidates to be used conjugated with antibodies and peptides. In the current paper we present the synthesis, physicochemical and in vitro characterization of sixty two Fms-like tyrosine kinase 3-internal tandem duplication (FLT3-ITD) mutant kinase inhibitors, bearing amino acid moieties, fit to be conjugated with peptide-based delivery systems via their carboxyl group. We determined the solubility, pKa, CHI and LogP values of the compounds along with their inhibition potential against FLT3-ITD mutant kinase and on MV4-11 cell line. The ester derivatives of the compounds inhibit the growth of the MV4-11 leukemia cell line at submicromolar concentration. 相似文献
123.
C. Schöfer Klara Weipoltshammer Marlene Almeder Franz Wachtler 《Histochemistry and cell biology》1997,108(4-5):313-319
The tyramide amplification technique has recently been developed for signal enhancement in enzyme-linked immunosorbent assays
and western blots. This method relies on using labelled tyramides as substrates for peroxidase, resulting in an immobilization
of the labelled tyramide residues (tyramide reaction). We succeeded in establishing reliable protocols for the use of the
tyramide reaction at the electron microscopic (EM) level. As model systems we chose the visualization of DNA in late spermatocytes,
of actin in skeletal muscle, and the visualization of an rDNA probe after DNA-DNA in situ hybridization. We observed a significant
increase in signal density after performing the tyramide reaction at the EM level. The tyramide amplification technique at
the ultrastructural level therefore appears to be a useful tool to detect even a few epitopes present at the surface of a
section as shown after in situ hybridization. It offers advantages over other amplification systems, such as the peroxidase-mediated
deposition of diaminobenzidine, because of an increased spatial resolution, whereas specificity and sensitivity are comparable
to the conventional immunogold detection method.
Accepted: 10 June 1997 相似文献
124.
Summary The contribution of peptide groups to H and H proton chemical shifts can be modeled with empirical equations that represent magnetic anisotropy and electrostatic interactions [Ösapay, K. and Case, D.A. (1991) J. Am. Chem. Soc., 113, 9436–9444]. Using these, a model for the random coil reference state can be generated by averaging a dipeptide over energetically allowed regions of torsion-angle space. Such calculations support the notion that the empirical constant used in earlier studies arises from neighboring peptide contributions in the reference state, and suggest that special values be used for glycine and proline residues, which differ significantly from other residues in their allowed ,-ranges. New constants for these residues are reported that provide significant improvements in predicted backbone shifts. To illustrate how secondary structure affects backbone chemical shifts we report calculations on oligopeptide models for helices, sheets and turns. In addition to suggesting a physical mechanism for the widely recognized average difference between and secondary structures, these models suggest several additional regularities that should be expected: (a) H protons at the edges of -sheets will have a two-residue periodicity; (b) the H2 and H3 protons of glycine residues will exhibit different shifts, particularly in sheets; (c) H protons will also be sensitive to local secondary structure, but in different directions and to a smaller extent than H protons; (d) H protons in turns will generally be shifted upfield, except those in position 3 of type I turns. Examples of observed shift patterns in several proteins illustrate the application of these ideas. 相似文献
125.
Little is known about the cellular physiology of Escherichia coli at high cell densities (e.g., greater than 50 g [dry cell weight] per liter), particularly in relation to the cellular response to different growth conditions. E. coli W3100 cultures were grown under identical physical and nutritional conditions, by using a computer-controlled fermentation system which maintains the glucose concentration at 0.5 g/liter, to high cell densities at pH values of 6.0, 6.5, 7.0, and 7.5. The data suggest a relationship between the pH of the environment and the amount of acetate excreted by the organism during growth. At pH values of 6.0 and 6.5, the acetate reached a concentration of 6 g/liter, whereas at pH 7.5, the acetate reached a concentration of 12 g/liter. Furthermore, at pH values of 6.0 to 7.0, the E. coli culture undergoes a dramatic metabolic switch in which oxygen and glucose consumption and CO2 evolution all temporarily decreased by 50 to 80%, with a concomitant initiation of acetate utilization. After a 30-min pause in which approximately 50% of the available acetate is consumed, the culture recovers and resumes consuming glucose and oxygen and producing acetate and CO2 at preswitch levels. During the switch period, the specific activity of isocitrate lyase typically increases approximately fourfold. 相似文献
126.
Elizaveta M. Igumnova Ekaterina Mishchenko Tor Haug Hans-Matti Blencke Johanna U. Ericson Sollid Elizabeth G. Aarag Fredheim Silje Lauksund Klara Stensvåg Morten B. Strøm 《Bioorganic & medicinal chemistry》2018,26(17):4930-4941
There is an urgent need for novel antimicrobial agents to address the threat of bacterial resistance to modern society. We have used a structural motif found in antimicrobial marine hit compounds as a basis for synthesizing a library of antimicrobial sulfonamidobenzamide lead compounds. Potent in vitro antimicrobial activity against clinically relevant bacterial strains was demonstrated for two compounds, G6 and J18, with minimal inhibitory concentrations (MIC) of 4–16?μg/ml against clinical methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Enterococcus faecium (VRE). The two compounds G6 and J18, together with several other compounds of this library, also caused ≥90% eradication of pre-established biofilm of methicillin-resistant S. epidermidis (MRSE) at 40?μg/ml. Using a luciferase assay, the mechanism of action of G6 was shown to resemble the biocide chlorhexidine by targeting the bacterial cell membrane. 相似文献
127.
Christopher H. Taylor Klara M. Wanelik Ida M. Friberg Ann Lowe Amy J. Hall Catriona Ralli Richard J. Birtles Mike Begon Steve Paterson Joseph A. Jackson Janette E. Bradley 《International journal for parasitology》2018,48(6):463-471
In contrast to the conditions in most laboratory studies, wild animals are routinely challenged by multiple infections simultaneously, and these infections can interact in complex ways. This means that the impact of a parasite on its host’s physiology and fitness cannot be fully assessed in isolation, and requires consideration of the interactions with other co-infections. Here we examine the impact of two common blood parasites in the field vole (Microtus agrestis): Babesia microti and Bartonella spp., both of which have zoonotic potential. We collected longitudinal and cross-sectional data from four populations of individually tagged wild field voles. This included data on biometrics, life history, ectoparasite counts, presence/absence of microparasites, immune markers and, for a subset of voles, more detailed physiological and immunological measurements. This allowed us to monitor infections over time and to estimate components of survival and fecundity. We confirm, as reported previously, that B. microti has a preventative effect on infection with Bartonella spp., but that the reverse is not true. We observed gross splenomegaly following B. microti infection, and an increase in IL-10 production together with some weight loss following Bartonella spp. infection. However, these animals appeared otherwise healthy and we detected no impact of infection on survival or fecundity due to the two haemoparasite taxa. This is particularly remarkable in the case of B. microti which induces apparently drastic long-term changes to spleen sizes, but without major adverse effects. Our work sheds light on the ecologies of these important zoonotic agents, and more generally on the influence that interactions among multiple parasites have on their hosts in the wild. 相似文献
128.
129.
130.
Silke Hafner Guido L. B. Wiesenberg Ekaterina Stolnikova Klara Merz Yakov Kuzyakov 《Plant and Soil》2014,380(1-2):101-115