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A continuous photometric assay of aminopeptidase P activity was developed which is based on a coupled enzymic assay with the substrate Gly-Pro-Pro-pNA and DPP IV as auxiliary enzyme. This assay was used to evaluate the kinetic parameters and inhibitory profile of intestinal brush border aminopeptidase P. 相似文献
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Gundula Thiel Tanka Lozanova Siegfried Vogel Dieter Kintzel Werner Jänisch Regine Witkowski 《Human genetics》1993,91(6):547-550
We report a cytogenetic investigation of 55 low-grade astrocytomas in 52 patients, 15 children and 37 adults. In addition to numerical aberrations such as trisomy 7 and gonosomal losses, we found structural and/or numerical aberrations of chromosome 1 in eight astrocytomas. There was a striking difference between the rearranged chromosomes in pediatric and adult patients. Whereas the pediatric tumors revealed monosomies 1p with accompanying trisomy 1q, the astrocytomas in adults showed partial or complete monosomies 1q. 相似文献
4.
Regine Hengge-Aronis 《Molecular microbiology》1996,21(5):887-893
It is now well established that the σS subunit of RNA polymerase is a master regulator in a complex regulatory network that governs the expression of many stationary-phase-inducible genes in Escherichiacoli. In this review, more recent findings will be summarized that demonstrate that σS also acts as a global regulator for the osmotic control of gene expression, and actually does so in exponentially growing cells. Thus, many σS-dependent genes are induced during entry into stationary phase as well as in response to osmotic upshift. K+ glutamate, which accumulates in hyperosmotically stressed cells, seems to specifically stimulate the activity of σS-containing RNA polymerase at σS-dependent promoters. Moreover, osmotic upshift results in an elevated cellular σS level similar to that observed in stationary-phase cells. This increase is the result of a stimulation of rpoS translation as well as an inhibition of the turnover of σS, which in exponentially growing non-stressed cells is a highly unstable protein. Whereas the RNA-binding protein HF-I, previously known as a host factor for the replication of phage Qβ RNA, is essential for rpoS translation, the recently discovered response regulator RssB, and ClpXP protease, have been shown to be required for σS degradation. The finding that the histone-like protein H-NS is also involved in the control of rpoS translation and σS turnover, sheds new light on the function of this protein in osmoregulation. Finally, preliminary evidence suggests that additional stresses, such as heat shock and acid shock, also result in increased cellular σS levels in exponentially growing cells. Taken together, σS function is clearly not confined to stationary phase. Rather, σS may be regarded as a sigma factor associated with general stress conditions. 相似文献
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Peter Miethe Ingeborg Jansen Uwe Niedermeyer Udo Kragl Regine Haftendorn Maria-Regina Kula Christian Wandrey Karl-Heinz Mohr Helmut-Walter Meyer 《Biocatalysis and Biotransformation》1992,7(1):61-73
The possibility of using the enzyme (R)-Oxynitrilase in a biphasic lyotropic liquid crystal/dibutylether system has been demonstrated. This reaction system is applicable for the continuous production of (R)-benzaldehydecyanohydrin in a fixed bed reactor. The optical purity was between 94 and 96% ee and independent of the flow rate. The space time yield was maximal (2650 g/(1*d)) at a flow rate of 1.6 ml/min. 相似文献
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Dietrich Werner Arno Krotzky Regine Berggold Heidemarie Thierfelder Marianne Preiß 《Archives of microbiology》1982,132(1):51-56
Specific nitrogenase activity inAzospirillum brasilense ATCC 29145 in surface cultures under air is enhanced from about 50 nmol C2H4·mg protein-1·h-1 to 400 nmol C2H4 by the addition of 1 mM phenol. 0.5 and 2 mM phenol added increase the rate 5-fold and 4-fold. This enhancement effect is observed only between 2 and 3 days after inoculation, with only a small reduction of the growth of the cells by the phenol added. In surface cultures under 1% O2, nitrogenase activity is slightly reduced by the addition of 1–0.01 mM phenol. Utilization of succinate is enhanced during the period of maximum enhancement of nitrogenase activity by 60% by addition of 1 mM phenol. The cells did not produce14CO2 from [U-14C] phenol, neither in surface cultures nor in liquid cultures and less than 0.1% of the phenol was incorporated into the cells. A smaller but significant enhancement of nitrogenase activity by about 100% in surface cultures under air was found withKlebsiella pneumoniae K 11 after addition of 1 mM phenol. However, inRhizobium japonicum 61-A-101 all phenol concentrations above 0.01 mM reduced nitrogenase activity. With 1 mM phenol added activity was reduced to less than 10% with no effect on the growth in the same cultivation system. With thisRhizobium japonicum strain significant quantities of phenol (25 mol in 24 h by 2·1012 cells) were metabolized to14CO2, with phenol as sole carbon source. WithAzospirillum brasilense in liquid culture under 1% and 2% O2 in the gas phase, no enhancement of nitrogenase activity by phenol was noticed. 相似文献
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The solvolytic detachment of leucine aminopeptidase from Sepharose-enzyme conjugates with multiple and single anchoring bonds has been studied under a variety of conditions by radiochemical and enzymological methods. The release of the single-point-fixed conjugate could be described by a leakage function, derived previously, yielding the first-order rate constant of the cleavage of the enzyme-matrix bond. The nucleophile hydroxylamine increased the detachment rate considerably. The release of the immobilized enzyme was incomplete in all experiments even after prolonged times. The enzyme leakage from multipoint-attached conjugates was still high enough to prohibit a long-term use of such preparations in routine work at room temperature. 相似文献
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