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51.
A major substrate of maturation promoting factor identified as elongation factor 1 beta gamma delta in Xenopus laevis 总被引:9,自引:0,他引:9
G M Janssen J Morales A Schipper J C Labbé O Mulner-Lorillon R Bellé W M?ller 《The Journal of biological chemistry》1991,266(23):14885-14888
Protein synthesis is believed to be under control of the cell cycle during meiosis and mitosis. Any relationship between substrates for cdc2 kinase and components of the protein synthetic apparatus would therefore be of prime importance. During meiosis of Xenopus laevis oocytes one of the substrates for this kinase is a p47 protein, which is complexed to two other proteins, P36 and P30. Judged from partial amino acid sequence data on P47 and P30, the P30 and P47 proteins were reported to resemble the protein synthetic elongation factors (EF) 1 beta and 1 gamma from Artemia salina (Bellé, R., Derancourt, J., Poulhe, R., Capony, J.P., Ozon, R., and Mulner-Lorillon, O. (1989) FEBS Lett. 255, 101-104). This paper shows that the complex composed of P30, P47, and P36 from Xenopus is identical to the complex of EF-1 beta, EF-1 gamma, and EF-1 delta from Artemia according to two criteria. 1) Both stimulate elongation factor 1 alpha-mediated transfer RNA binding to ribosomes and exchange of guanine nucleotides on elongation factor 1 alpha to a comparable degree. 2) Each of the three subunits of the protein complex P30.P47.P36 from Xenopus shows a structural homology with one of the corresponding subunits of EF-1 beta gamma delta from Artemia. Presumably the phosphorylation of EF-1 gamma, which associates with tubulin at least in vitro, is important in processes following the onset of meiosis which is accompanied by a rise of protein synthesis. 相似文献
52.
T cell receptor/CD3-signaling induces death by apoptosis in human T cell receptor gamma delta + T cells. 总被引:14,自引:0,他引:14
O Janssen S Wesselborg B Heckl-Ostreicher K Pechhold A Bender S Schondelmaier G Moldenhauer D Kabelitz 《Journal of immunology (Baltimore, Md. : 1950)》1991,146(1):35-39
mAb directed against the TCR/CD3 complex activate resting T cells. However, TCR/CD3 signaling induces death by apoptosis in immature (CD4+CD8+) murine thymocytes and certain transformed leukemic T cell lines. Here we show that anti-TCR and anti-CD3 mAb induce growth arrest of cloned TCR-gamma delta + T cells in the presence of IL-2. In the absence of exogenous IL-2, however, the very same anti-TCR/CD3 mAb stimulated gamma delta (+)-clones to proliferation and IL-2 production. In the presence of exogenous IL-2, anti-TCR/CD3 mAb induced the degradation of DNA into oligosomal bands of approximately 200 bp length in cloned gamma delta + T cells. This pattern of DNA fragmentation is characteristic for the programmed cell death termed apoptosis. These results demonstrate that TCR/CD3 signaling can induce cell death in cloned gamma delta + T cells. In addition, this report is the first to show that apoptosis triggered by TCR/CD3 signaling is not restricted to CD4+CD8+ immature thymocytes and transformed leukemic T cell lines but can be also observed with IL-2-dependent normal (i.e., TCR-gamma delta +) T cells. 相似文献
53.
G Schieren O Janssen G M H?nsch 《Journal of immunology (Baltimore, Md. : 1950)》1992,148(10):3183-3188
C8 binding protein (C8bp) is a 65-kDa membrane glycoprotein that inhibits complement-mediated lysis by homologous C5b-9. C8bp was first identified on human erythrocytes, but could also be detected on peripheral blood cells, platelets, glomerular cells and synovial fibroblasts. Lack of C8bp as seen in patients with paroxysmal nocturnal hemoglobinuria type III results in enhanced susceptibility of the cells toward C5b-9. We studied C8bp expression on the promonocytic cell line U937. In addition to the membrane-bound C8bp, a cytoplasmic form of C8bp could also be identified by immunofluorescence, blotting, and precipitation. Stimulation of the cells with IL-1 beta, endotoxin, IFN-gamma, or phorbol ester increased C8bp surface expression. Because cycloheximide did not inhibit enhanced surface expression, it was most probably mobilized from cytoplasmic reservoirs. Thus, resistance of nuclear cells to complement attack seems to be based on two events: 1) the removal of the C5b-9 complex from the membrane; and 2) expression of regulatory surface proteins such as C8bp, which inhibit C5b-9-mediated lysis. We propose that the C8bp mobilization by cytokines might provide an additional protection against complement attack by its known interference with the C5b-9 assembly. 相似文献
54.
Peter H. Janssen 《Antonie van Leeuwenhoek》1991,59(3):191-198
Enrichments on L-tartrate from a freshwater lake sediment yielded a pure culture of anaerobic bacterium designated strain 16Lt1. The rod-shaped organism was motile, did not form spores, and had a gram-negative wall structure. No cytochromes were detected. The mol % G+C of the DNA was 58. The new strain was microaerotolerant, and grew optimally at 30°C and neutral pH in freshwater medium. A wide range of carbohydrates was fermented, with formate, acetate, ethanol, lactate and succinate being the end-products detected. L-tartrate and citrate were fermented to formate, acetate and CO2. L-tartrate was fermented by the dehydratase pathway, and glucose by the Embden-Meyerhof-Parnas pathway. Fumarate was reduced, but nitrate, sulfate, sulfur and thiosulfate were not used as terminal electron acceptors. Glucose metabolism was constitutive, whereas L-tartrate-degrading activity was inducible. When glucose and L-tartrate were both present as substrates, growth was diauxic with glucose being metabolized first. The growth rate and growth yield were higher on glucose than on L-tartrate. Strain 16Lt1 has been deposited with the Deutsche Sammlung von Mikroorganismen as Bacteroides sp. DSM6268. 相似文献
55.
W D Nes G G Janssen R A Norton M Kalinowska F G Crumley B Tal A Bergenstrahle L Jonsson 《Biochemical and biophysical research communications》1991,177(1):566-574
Whereas sitosterol and 24(28)-methylene cycloartanol were competitive inhibitors (with Ki = 26 microM and 14 microM, respectively), 24(R,S)-25-epiminolanosterol was found to be a potent non-competitive inhibitor (Ki = 3.0 nM) of the S-adenosyl-L-methionine-C-24 methyl transferase from sunflower embryos. Because the ground state analog, 24(R,S)-oxidolanosterol, failed to inhibit the catalysis and 25-azalanosterol inhibited the catalysis with a Ki of 30 nM we conclude that the aziridine functions in a manner similar to the azasteriod (Rahier, A., et al., J. Biol. Chem. (1984) 259, 15215) as a transition state analog mimicking the carbonium intermediate found in the normal transmethylation reaction. Additionally, we observed that the aziridine inhibited cycloartenol metabolism (the preferred substrate for transmethylation) in cultured sunflower cells and cell growth. 相似文献
56.
K J Lusthof W Richter N J de Mol L H Janssen W Verboom D N Reinhoudt 《Archives of biochemistry and biophysics》1990,277(1):137-142
The reduction of a series of 2,5-bis(1-aziridinyl)-1,4-benzoquinone (BABQ) derivatives with various 3,6 substituents by the enzyme xanthine oxidase has been studied. The reduction rate has been assayed by measuring the rate of reduction of cytochrome c, which is very efficiently reduced by reduced BABQ species. Under nitrogen, the reduction rate correlated with the quinone reduction potential and steric parameters. Comparing reduction rates under nitrogen and air demonstrates that at BABQ concentrations greater than 25 microM the competition for electrons from xanthine oxidase between oxygen and the BABQ derivative is dominated by the latter. This is also confirmed by the effect of superoxide dismutase (SOD): in the presence of a BABQ derivative, cytochrome c reduction can be totally inhibited by SOD, although the required amount of SOD depends on the redox potential of the quinones. This indicates that SOD causes the equilibrium between semiquinone and superoxide to shift, resulting in a decrease of the semiquinone concentration. It is concluded that reduction by xanthine oxidase is a simple and effective method for reducing aziridinylbenzoquinones. 相似文献
57.
In the present study a two-dimensional finite element model for incompressible Newtonian flow is applicated to the modelling of carotid artery flow. In earlier studies, the numerical model was validated experimentally for several flow configurations. In general the pulsatile flow is characterized by reversed flow regions at the non-divider side walls of both the internal and external carotid arteries. The unsteadiness of the flow is associated with rather complex spatial and temporal velocity distributions and leads to temporal variations of the location and length of the reversed flow regions. As a consequence, pronounced spatial and temporal variations in the wall shear stresses are found. At the non-divider side walls, wall shear stresses are relatively low and exhibits an oscillatory behaviour in space and time. At the divider side walls, wall shear stresses are relatively high and approximately follow the flow rate distribution in time. The aim of this study is not only to present two-dimensional calculations but also to compare the calculated two-dimensional velocity profiles with those from three-dimensional experiments. It is observed that in the common carotid artery and in the proximal parts of the internal and external carotid arteries, the two-dimensional numerical model provides valuable information with respect to the three-dimensional configuration. In the more distal parts of especially the internal carotid artery, deviations are found between the two-dimensional numerical and three-dimensional experimental model. These deviations can mainly be attributed to the neglect of the secondary velocity distribution in the two-dimensional model. In the two-dimensional numerical model the influence of a minor stenosis in the internal carotid artery is hardly distinguishable from a minor geometrical variation without stenosis. Full three-dimensional analyses of the influence of minor stenoses are needed to prove numerically whether in-vivo measurements of the axial velocity distribution are useful in the detection of minor stenoses. 相似文献
58.
Regulation of amidase formation in mutants from Pseudomonas aeruginosa PAO lacking glutamine synthetase activity 总被引:1,自引:0,他引:1
Dick B. Janssen Patricia M. Herst Han M. L. J. Joosten Chris van der Drift 《Archives of microbiology》1982,131(4):344-346
The formation of amidase was studied in mutants from Pseudomonas aeruginosa PAO lacking glutamine synthetase activity. It appeared that catabolite repression of amidase synthesis by succinate was partially relieved when cellular growth was limited by glutamine. Under these conditions, a correlation between amidase and urease formation was observed. The results suggest that amidase formation in strain PAO is subject to nitrogen control and that glutamine or some compound derived from it mediates the nitrogen repression of amidase. 相似文献
59.
Mobility of endogenous ecotropic murine leukemia viral genomes within mouse chromosomal DNA and integration of a mink cell focus-forming virus-type recombinant provirus in the germ line 总被引:6,自引:4,他引:2 下载免费PDF全文
Characterization of endogenous ecotropic Akv proviruses in DNA of low and high leukemic mouse strains revealed the presence of one to six copies of the Akv genome per haploid genome equivalent integrated in the germ line. Low leukemic strains analyzed so far contained only one complete copy of the Akv proviral DNA. The site of integration varied among strains, although genetically related strains often carried the Akv proviral gene in the same chromosomal site. The different substrains of the AKR mouse displayed the presence of variable numbers (two to six) of Akv genomes. In all substrains one Akv genome was present in an identical chromosomal site; this locus probably comprised the progenitor genome. Closely related substrains had several Akv proviral DNAs integrated in common sites. The accumulation of Akv genomes in the germ line of the AKR/FuRdA strain is likely the result of independent integration events, since backcross studies with the Akv-negative 129 strain showed random segregation of all six proviral loci. The AKR/Cnb strain carried a recombinant provirus in the germ line. This provirus resembled in structure the AKR mink cell focus-forming viruses, which are generated by somatic recombination during leukemogenesis. Therefore, the germ-line amplification of Akv proviral DNAs occurs most likely through infection of embryonic cells by circulating virus. 相似文献
60.
Janssen Dick B. op den Camp Huub J. M. Leenen Pieter J. M. van der Drift Chris 《Archives of microbiology》1980,124(2-3):197-203
Glutamine synthetase from Pseudomonas aeruginosa is regulated by repression/derepression of enzyme synthesis and by adenylylation/deadenylylation control. High levels of deadenylylated biosynthetically active glutamine synthetase were observed in cultures growing with limiting amounts of nitrogen while synthesis of the enzyme was repressed and that present was adenylylated in cultures with excess nitrogen.NADP-and NAD-dependent glutamate dehydrogenase could be separated by column chromatography and showed molecular weights of 110,000 and 220,000, respectively. Synthesis of the NADP-dependent glutamate dehydrogenase is repressed under nitrogen limitation and by growth on glutamate. In contrast, NAD-dependent glutamate dehydrogenase is derepressed by glutamate. Glutamate synthase is repressed by glutamate but not by excess nitrogen. 相似文献