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41.
42.
Hugo P. Montiero Glenn F. Vile Christine C. Winterbourn 《Free radical biology & medicine》1989,6(6):587-591
The cytotoxicity of many xenobiotics is related to their ability to undergo redox reactions and iron dependent free radical reactions. We have measured the ability of a number of redox active compounds to release iron from the cellular iron storage protein, ferritin. Compounds were reduced to their corresponding radicals with xanthine oxidase/hypoxanthine under N2 and the release of Fe2+ was monitored by complexation with ferrozine. Ferritin iron was released by a number of bipyridyl radicals including those derived from diquat and paraquat, the anthracycline radicals of adriamycin, daunorubicin and epirubicin, the semiquinones of anthraquinone-2-sulphonate, 1,5 and 2,6-dihydroxyanthraquinone, 1-hydroxyanthraquinone, purpurin, and plumbagin, and the nitroaromatic radicals of nitrofurantoin and metronidazole. In each case, iron release was more efficient than with an equivalent flux of superoxide. Introduction of air decreased the rate of iron release, presumably because the organic radicals reacted with O2 to form superoxide. In air, iron release was inhibited by superoxide dismutase. Semiquinones of menadione, benzoquinone, duroquinone, anthraquinone 1,5 and 2,6-disulphonate, 1,4 naphthoquinone-2-sulphonate and naphthoquinone, when formed under N2, were unable to release ferrin iron. In air, these systems gave low rates of superoxide dismutase-inhibitible iron release. Of the compounds investigated, those with a single electron reduction potential less than that of ferritin were able to release ferritin iron. 相似文献
43.
Nalin Rastogi Dr.Sc. Marie-Christine Blom-Potar Hugo L. David 《Current microbiology》1989,19(2):83-89
The intracellular growth kinetics ofMycobacterium xenopi was studied in the murine J-774 macrophage cell line model. During the initial 4 days of infection, the bacilli divided about every 33 h. Electron microscopy of infected macrophages showed that bacteria inside phagosomes were surrounded by a protective electron-transparent zone (ETZ). This model was used for comparing the extracellular and intracellular activities of the following drugs: pristinamycin (PRISTINA), isoniazid (INH), clofazimine (CLOFA), rifabutin (=ansamycin; ANSA), rifampicine (RIFA), streptomycin (SM), ethambutol (EMB), and five fluoroquinolones, namely, ciprofloxacin (CIPRO), ofloxacin (OFLO), pefloxacin (PEFLO), enoxacin (ENOX) and norfloxacin (NORFLO). All the drugs were tested within their obtainable serum level concentrations in man. Under these conditions, CLOFA, SM, CIPRO, and OFLO were highly active against intracellularly growingM. xenopi, INH and RIFA were moderately active, whereas ANSA, PRISTINA, EMB, PEFLO, ENOX, and NORFLO were only growth inhibiting. The comparison of these data with extracellular activities of the same drugs underlined the discrepancies observed in test-tube drug activity evaluation and its correlation with results of chemotherapy in patients in whom the drug has essentially an intracellular bacterial killing role. 相似文献
44.
M protein (M1) of influenza virus: antigenic analysis and intracellular localization with monoclonal antibodies. 总被引:6,自引:5,他引:1 下载免费PDF全文
D Bucher S Popple M Baer A Mikhail Y F Gong C Whitaker E Paoletti A Judd 《Journal of virology》1989,63(9):3622-3633
A panel of 16 monoclonal antibodies recognizing M protein (M1) of influenza virus was generated. Competition analyses resulted in localization of 14 monoclonal antibodies to three antigenic sites. Three monoclonal antibodies localized to site 1B recognized a peptide synthesized to M1 (residues 220 to 236) with enzyme-linked immunosorbent assay titers equivalent to or greater than that seen with purified M1; therefore, site 1B is located near the C terminus of M1. Sites 2 and 3 localize to the N-terminal half of M1. Antigenic variation of M proteins was seen when the monoclonal antibodies were tested against 14 strains of type A influenza viruses. Several monoclonal antibodies showed specific recognition of A/PR/8/34 and A/USSR/90/77 M proteins and little or no reactivity for all other strains tested. Immunofluorescence analysis with the monoclonal antibodies showed migration of M protein to the nucleus during the replicative cycle and demonstrated association of M protein with actin filaments in the cytoplasm. Use of a vaccinia virus recombinant containing the M-protein gene demonstrated migration of M protein to the nucleus in the absence of synthesis of gene products from other influenza virus RNA segments. 相似文献
45.
In order to advance knowledge of the neural control of feeding,we investigated the cortical representation of the taste oftannic acid, which produces the taste of astringency. It isa dietary component of biological importance particularly toarboreal primates. Recordings were made from 74 taste responsiveneurons in the orbitofrontal cortex. Single neurons were foundthat were tuned to respond to 0.001 M tannic acid, and representeda subpopulation of neurons that was distinct from neurons responsiveto the tastes of glucose (sweet), NaCl (salty), HCI (sour),quinine (bitter) and monosodium glutamate (umami). In addition,across the population of 74 neurons, tannic acid was as wellrepresented as the tastes of NaCI, HCI quinine or monosodiumglutamate. Multidimensional scaling analysis of the neuronalresponses to the tastants indicates that tannic acid lies outsidethe boundaries of the four conventional taste qualities (sweet,sour, bitter and salty). Taken together these data indicatethat the astringent taste of tannic acid should be consideredas a distinct taste quality, which receives a separate representationfrom sweet, salt, bitter and sour in the primate cortical tasteareas. Chem. Senses 21: 135145, 1996. 相似文献
46.
47.
The PROSITE database consists of biologically significant patterns and profiles formulated in such a way that with appropriate computational tools it can help to determine to which known family of proteins (if any) a new sequence belongs or which known domain(s) it contains. 相似文献
48.
Neuronal communication involves the fusion of neurotransmitter filled synaptic vesicles with the presynaptic terminal. This
exocytotic event depends upon proteins present in three separate compartments: the synaptic vesicle, the synaptic cytosol,
and the presynaptic membrane. Recent data indicate that the basic components of exocytotic pathways, including those used
for neurotransmitter release, are conserved from yeast to human. Genetic dissection of the secretory pathway in yeast, identification
of the target proteins cleaved by the clostridial neurotoxins and biochemical characterization of the interactions of synaptic
proteins from vertebrates have converged to provide the SNARE (soluble NSF attachment protein receptor) hypothesis for vesicle
trafficking. This model proposes that proteins present in the vesicle (v-SNAREs) interact with membrane receptors (t-SNAREs)
to provide a molecular scaffold for cytosolic proteins involved in fusion. The hypothesis that these mechanisms function at
the synapse relies largely uponin vitro evidence. Recently, genetic approaches in mice, C.elegans and the fruitfly,Drosophila melanagaster, have been used to dissect thein vivo function of numerous proteins involved in synaptic transmission. This review covers recent progress and insights provided
by a genetic dissection of neurotransmitter release inDrosophila. In addition, we will provide evidence that the mechanisms for synaptic communication are highly conserved from invertebrates
to vertebrates, makingDrosophila an ideal model system to further unravel the intricacies of synaptic transmission. 相似文献
49.
Thomas Altmann Gisela Felix Alison Jessop Annette Kauschmann Ursula Uwer Hugo Peña-Cortés Lothar Willmitzer 《Molecular genetics and genomics : MGG》1995,247(5):646-652
Using a two-component Ac/Ds system consisting of a stabilized Ac element (Acc1) and a non-autonomous element (DsA), 650 families of plants carrying independent germinal DsA excisions/transpositions were isolated. Progenies of 559 of these Acc1/DsA families, together with 43 families of plants selected for excision/transposition of wild-type (wt)Ac, were subjected to a broad screening program for mutants exhibiting visible alterations. This resulted in the identification of 48 mutants showing a wide variety of mutant phenotypes, including embryo lethality (24 mutants), chlorophyll defects (5 mutants), defective seedlings (2 mutants), reduced fertility (5 mutants), reduced size (3 mutants), altered leaf morphology (2 mutants), dark green, unexpanded rosette leaves (3 mutants), and aberrant flower or shoot morphology (4 mutants). To test whether these mutants were due to transposon insertions, a series of Southern blot experiments was performed on 28 families, comparing in each case several mutant plants with others showing the wild-type phenotype. A preliminary analysis revealed in 4 of the 28 families analyzed a common, novel DsA fragment in all mutant plants, which was present only in heterozygous plants with wt phenotype, as expected for DsA insertion mutations. These four mutants included two showing embryo lethality, one with dark green, unexpanded rosette leaves and stunted inflorescences, and one with curly growth of stems, leaves and siliques. Further evidence for DsA insertion mutations was obtained for one embryo lethal mutant and for the stunted mutant, while in case of the second embryo lethal mutant, the DsA insertion could be separated from the mutant locus by genetic recombination. 相似文献