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41.
For many years data of cancer research indicated that viruses can cause cancer. Virus infections induce cancer by different mechanisms. To predict the significance of a viral DNA fragment in human cells we have to be aware of the changes the particular virus is able to induce there.However, no matter which mechanisms of viral carcinogenesis are utilized, generally other factors (environmental, chemical, immunodeficiency, etc.) are also needed to induce invasive cancer in human. Before the introduction of nucleic acid based detection technique virus identification was a long and cumbersome process. This has been eliminated by the invention of recombinant gene technology and polymerase chain reaction. Virus nucleic acid can be detected without amplification using Southern, Northern and in situ hybridization. Techniques for target (polymerase chain reaction)or signal (hybrid capture, tyramine) amplification improved the sensitivity of detection. In the meantime, for the successful use of the arsenal of new methods we have to consider the characteristic feature of molecular virus research. A major achievement of molecular virus detection is that it proved the pathological significance of viruses in human cancers even in those where this was not expected. Hopefully these informations will increase the effort for elimination of oncogene virus infections. 相似文献
42.
Dusha I 《Indian journal of experimental biology》2002,40(9):981-988
Under nitrogen-depleted conditions nitrogen-fixing soil bacteria of the family Rhizobiaceae are able to induce symbiotic nodules on the roots of leguminous plants where bacteroids convert atmospheric nitrogen to ammonia. The presence of exogenous nitrogen source inhibits the development and the functioning of bacterium-plant symbiosis. Earlier experiments demonstrated that nitrate inhibited all stages of symbiotic interaction, affecting primarily the host functions. The investigation of the possible involvement of the microsymbiont in nitrogen regulation showed that two signalling steps were controlled by ammonium. The synthesis of the first bacterial signal, the Nod factor was repressed by ammonium. The nitrogen signal is conveyed to nodulation (nod) genes by the general nitrogen regulatory (ntr) system and by the nodD3-syrM self-amplifying system. The fine control also involves a negative regulatory factor, ntrR. When ntrR is mutated, more efficient nodule formation and nitrogen fixation is observed in symbiosis with alfalfa even in the presence of ammonium. The biosynthesis of the second bacterial signal succinoglycan is also controlled by ammonium. SyrM, a common regulatory factor for nod and exo gene expression, may contribute to the adjustment of the amount of succinoglycan and the ratio of its biologically active form. 相似文献
43.
Dósa E Dóczi I Mojzes L Molnár EG Varga J Nagy E 《Acta microbiologica et immunologica Hungarica》2002,49(2-3):337-346
The fungal revolution taking place in otorhinology inspired us to study the frequency of occurrence of fungi in the nasal mucus of chronic rhinosinusitis (CRS) patients (with or without polyposis) in order to evaluate the incidence of eosinophilic fungal sinusitis in CRS patients. Ninety-six samples were examined from patients with CRS. In 74 cases mucus was collected non-invasively, and in 22 cases during operation. The Gram-stained direct smears of all samples were also evaluated. Bacteria and fungi colonizing in the mucus were detected by culturing method. The control group consisted of 50 healthy volunteers. Typical aerobic pathogenic bacteria could be isolated from 34 patients. Fifty-seven aerobic bacteria were isolated, i.e. 1.6 bacteria/positive patient with a maximum of 3 different bacteria/sample. The most frequently isolated bacteria were Staphylococcus aureus, Escherichia coli, Klebsiella pneumoniae, Streptococcus pneumoniae, and Haemophilus influenzae. Yeasts and moulds could be detected from 79 patients (83%): Candida albicans, Candida spp., Aspergillus spp., Cladosporium spp, and Penicillium spp. were isolated most frequently. Altogether 237 yeasts and moulds were isolated, i.e. 3.0 different fungi/positive patient, with a maximum of 5 different fungi/sample. In the control group aerobic pathogens were not isolated, only apathogenic species. Fungi were isolated from 22 healthy patients (44%). These data indicate that fungi are frequently involved in the aetiology of CRS. IgE-medicated hypersensitivity to fungal allergens could not be proven in our patients. 相似文献
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47.
Frieden IJ 《Lymphatic research and biology》2003,1(4):313-316
Hemangiomas of infancy are very common tumors, but they are heterogeneous in their behavior. A small, but significant, subset causes medical complications or permanent disfigurement, but due to their heterogeneity, there is no appropriate "one size fits all" approach to management. In addition, the rapid evolution of this tumor over the first weeks-to-months of infancy renders even more difficult the task of predicting which infants will have medical complications or permanent disfigurement. This article outlines the clinical characteristics that help to stratify hemangiomas into those which are high risk, and likely to require either active treatment or closer scrutiny, and those which are low risk, and likely to behave in an innocuous manner. Five major factors are emphasized: the age of the child, the location of the hemangioma(s), the total number of hemangiomas present, the hemangioma subtype, and the presence and nature of dermal involvement. 相似文献
48.
Three phosphatidylinositol 4-kinase isoforms, PI4K 230, 92 and 55 have been cloned and sequenced allowing a much wider characterization than the previously employed enzymological typing into type II and III enzymes. PI4K 230 and 92 contain a highly conserved catalytic core, PI4K55 one with a much lower degree of similarity. Candidate kinase motifs, deduced from the protein kinase super family, are absolutely conserved in all isoforms. Kinase activities are described based on their sensitivity and reactivity towards wortmannin, phenylarsine oxide (PAO) and 5'-p-fluorosulfonylbenzoyladenosine (FSBA). Localization of all isoforms in the cell is reported. All enzymes contain nuclear localization and export sequence motifs (NLS and NES) leading to the expectation that they can be transferred to the nucleus. PI4K230 has been found in the nucleolus, PI4K92 in the nucleus, additionally further broadening the function of these enzymes. In the cytoplasm of neuronal cells, PI4K230 is distributed evenly on membranes that are ultra structurally cisterns of the rough endoplasmatic reticulum, outer membranes of mitochondria, multivesicular bodies, and are in close vicinity of synaptic contacts. PI4K92 is functionally characterized as a key enzyme regulating Golgi disintegration/reorganization during mitosis probably via phosphorylation by cyclin-dependent kinases on well-defined sites. PI4K55 is involved in the production of second messengers, diacylglycerol (DAG) and inositol 1,4,5-trisphosphate (InsP3) at the plasma membrane, moreover, in the endocytotic pathway in the cytoplasm. 相似文献
49.
Kovács I Lasztóczi B Szárics E Héja L Sági G Kardos J 《Neurochemistry international》2003,43(2):101-112
Parameters of [3H]uridine binding to synaptic membranes isolated from rat brain cortex (K(D)=71+/-4 nM, B(max)=1.37+/-0.13 pmol/mg protein) were obtained. Pyrimidine and purine analogues displayed different rank order of potency in displacement of specifically bound [3H]uridine (uridine>5-F-uridine>5-Br-uridine approximately adenosine>5-ethyl-uridine approximately suramin>theophylline) and in the inhibition of [14C]uridine uptake (adenosine>uridine>5-Br-uridine approximately 5-F-uridine approximately 5-ethyl-uridine) into purified cerebrocortical synaptosomes. Furthermore, the effective ligand concentration for the inhibition of [14C]uridine uptake was about two order of magnitude higher than that for the displacement of specifically bound [3H]uridine. Adenosine evoked the transmembrane Na(+) ion influx, whereas uridine the transmembrane Ca(2+) ion influx much more effectively. Also, uridine was shown to increase free intracellular Ca(2+) ion levels in hippocampal slices by measuring Calcium-Green fluorescence. Uridine analogues were found to be ineffective in displacing radioligands that were bound to various glutamate and adenosine-recognition and modulatory-binding sites, however, increased [35S]GTPgammaS binding to membranes isolated from the rat cerebral cortex. These findings provide evidence for a rather specific, G-protein-coupled site of excitatory action for uridine in the brain. 相似文献
50.
Carugo O Cemazar M Zahariev S Hudáky I Gáspári Z Perczel A Pongor S 《Protein engineering》2003,16(9):637-639
The formation of a disulfide bond between adjacent cysteine residues is accompanied by the formation of a tight turn of the protein backbone. In nearly 90% of the structures analyzed a type VIII turn was found. The peptide bond between the two cysteines is in a distorted trans conformation, the omega torsion angle ranges from 159 to -133 degrees, with an average value of 171 degrees. The constrained nature of the vicinal disulfide turn and the pronounced difference observed between the oxidized and reduced states, suggests that vicinal disulfides may be employed as a 'redox-activated' conformational switch. 相似文献