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Sturgeon BE Glover RE Chen YR Burka LT Mason RP 《The Journal of biological chemistry》2001,276(49):45516-45521
The quenching of the Y(D)(.) tyrosyl radical in photosystem II by nitric oxide was reported to result from the formation of a weak tyrosyl radical-nitric oxide complex (Petrouleas, V., and Diner, B. A. (1990) Biochim. Biophys. Acta 1015, 131-140). This radical/radical reaction is expected to generate an electron spin resonance (ESR)-silent 3-nitrosocyclohexadienone species that can reversibly regenerate the tyrosyl radical and nitric oxide or undergo rearrangement to form 3-nitrosotyrosine. It has been proposed that 3-nitrosotyrosine can be oxidized by one electron to form the tyrosine iminoxyl radical (>C=N-O*). This proposal was put forth as a result of ESR detection of the iminoxyl radical intermediate when photosystem II was exposed to nitric oxide (Sanakis, Y., Goussias, C., Mason, R. P., and Petrouleas, V. (1997) Biochemistry 36, 1411-1417). A similar iminoxyl radical was detected in prostaglandin H synthase-2 (Gunther, M. R., Hsi, L. C., Curtis, J. F., Gierse, J. K., Marnett, L. J., Eling, T. E., and Mason, R. P. (1997) J. Biol. Chem., 272, 17086-17090). Although the iminoxyl radicals detected in the photosystem II and prostaglandin H synthase-2 systems strongly suggest a mechanism involving 3-nitrosotyrosine, the iminoxyl radical ESR spectrum was not unequivocally identified as originating from tyrosine. We report here the detection of the non-protein L-tyrosine iminoxyl radical generated by two methods: 1) peroxidase oxidation of synthetic 3-nitroso-N-acetyl-L-tyrosine and 2) peroxidase oxidation of free L-tyrosine in the presence of nitric oxide. A newly developed ESR technique that uses immobilized enzyme was used to perform the ESR experiments. Analysis of the high resolution ESR spectrum of the tyrosine iminoxyl radical generated from free tyrosine and nitric oxide reveals a 28.4-G isotropic nitrogen hyperfine coupling and a 2.2-G proton hyperfine coupling assigned to the proton originally ortho to the phenoxyl oxygen. 相似文献
77.
Medvede AE Abakumova OYu Podobed OV Tsvetkova TA Sandler M Glover V 《Life sciences》2001,69(15):1783-1790
We have previously demonstrated that isatin (indole-2,3 dione), an endogenous compound widely distributed in mammalian tissues and body fluids, effectively inhibits atrial natriuretic peptide (ANP) receptor binding and ANP-stimulated guanylyl cyclase activity of rat membrane preparations. In the present study the effects of isatin on ANP-mediated accumulation of cGMP and guanylyl cyclase (GC) activity of PC12 cells were studied. Isatin (0.1 mM) effectively inhibited ANP-stimulated GC-activity of broken cells but was nearly inactive in attenuating ANP-dependent accumulation of cGMP in intact PC12 cells. The ATP-analogue adenylylimidodiphosphate (AMP-PNP) slightly potentiated the ANP effect on GC activity in broken cell preparations and significantly reduced GC sensitivity to isatin. Isatin caused a more pronounced reduction of ANP-dependent cGMP accumulation in cells grown in the presence of 10% embryonal calf serum (ECS) than in 0.5% ECS. The data obtained suggest that, in intact cells, the manifestation of the isatin effect on ANP-mediated signal transduction may depend on intracellular factor(s), possibly interacting at the kinase domain. 相似文献
78.
lux -marked biosensors for assessing the toxicity and bioremediation potential of polluted environments may complement traditional chemical techniques. lux CDABE genes were introduced into the chromosome of the 2,4-dichlorophenol (2,4-DCP)-mineralizing bacterium, Burkholderia sp. RASC c2, by biparental mating using the Tn 4431 system. Experiments revealed that light output was constitutive and related to cell biomass concentration during exponential growth. The transposon insertion was stable and did not interrupt 2,4-DCP-degradative genes, and expression of lux CDABE did not constitute a metabolic burden to the cell. A bioluminescence response was detectable at sublethal 2,4-DCP concentrations: at < 10.26 μg ml−1 , bioluminescence was stimulated (e.g. 218% of control), but at concentrations > 60 μg ml−1 it declined to < 1%. Investigating the effect of [14 C]-2,4-DCP concentration on the evolution of 14 CO2 revealed that, for initial concentrations of 2.5–25 μg ml−1 , ≈55% of the added 14 C was mineralized after 24 h compared with < 1% at 50 and 100 μg ml−1 . Inhibition of 2,4-DCP mineralization between 25 and 50 μg ml−1 corresponded well to the EC50 value (33.83 μg ml−1 ) obtained from bioluminescence inhibition studies. lux -marked RASC c2 may therefore be used as a functionally (i.e. 2,4-DCP degrader) and environmentally relevant biosensor of toxicity and biodegradation inhibition. 相似文献
79.
BRCA1 is required for common-fragile-site stability via its G2/M checkpoint function 总被引:1,自引:0,他引:1
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Arlt MF Xu B Durkin SG Casper AM Kastan MB Glover TW 《Molecular and cellular biology》2004,24(15):6701-6709
Common fragile sites are loci that form chromosome gaps or breaks when DNA synthesis is partially inhibited. Fragile sites are prone to deletions, translocations, and other rearrangements that can cause the inactivation of associated tumor suppressor genes in cancer cells. It was previously shown that ATR is critical to fragile-site stability and that ATR-deficient cells have greatly elevated fragile-site expression (A. M. Casper, P. Nghiem, M. F. Arlt, and T. W. Glover, Cell 111:779-789, 2002). Here we demonstrate that mouse and human cells deficient for BRCA1, due to mutation or knockdown by RNA interference, also have elevated fragile-site expression. We further show that BRCA1 functions in the induction of the G(2)/M checkpoint after aphidicolin-induced replication stalling and that this checkpoint function is involved in fragile-site stability. These data indicate that BRCA1 is important in fragile-site stability and that fragile sites are recognized by the G(2)/M checkpoint pathway, in which BRCA1 plays a key role. Furthermore, they suggest that mutations in BRCA1 or interacting proteins could lead to rearrangements at fragile sites in cancer cells. 相似文献
80.
Podgornik A Jancar J Merhar M Kozamernik S Glover D Cucek K Barut M Strancar A 《Journal of biochemical and biophysical methods》2004,60(3):179-189
Monoliths represent a special class of chromatographic supports. In contrast to other stationary phases, they consist of a single piece of highly porous material through which a sample is mainly transported by convection. As a consequence, monoliths enable fast separations and exhibit flow-unaffected properties, which make them attractive for purification of macromolecules like proteins or DNA. In this work, methacrylate-based monolithic columns with the bed volume up to 8000 ml are characterized. They perform high-resolution separations of several hundreds of grams of proteins per hour by utilizing liter per minute flow rates. They are incompressible under these operating conditions and resistant to strong alkaline conditions. 相似文献