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201.
Ryan Knihtila Genevieve Holzapfel Kevin Weiss Flora Meilleur Carla Mattos 《The Journal of biological chemistry》2015,290(52):31025-31036
RAS GTPase is a prototype for nucleotide-binding proteins that function by cycling between GTP and GDP, with hydrogen atoms playing an important role in the GTP hydrolysis mechanism. It is one of the most well studied proteins in the superfamily of small GTPases, which has representatives in a wide range of cellular functions. These proteins share a GTP-binding pocket with highly conserved motifs that promote hydrolysis to GDP. The neutron crystal structure of RAS presented here strongly supports a protonated γ-phosphate at physiological pH. This counters the notion that the phosphate groups of GTP are fully deprotonated at the start of the hydrolysis reaction, which has colored the interpretation of experimental and computational data in studies of the hydrolysis mechanism. The neutron crystal structure presented here puts in question our understanding of the pre-catalytic state associated with the hydrolysis reaction central to the function of RAS and other GTPases. 相似文献
202.
Regulation of energy source metabolism in streptococci 总被引:1,自引:0,他引:1
O.M. Neijssel J.L. Snoep & M.J. Teixeira de Mattos 《Journal of applied microbiology》1997,83(S1):12S-19S
203.
M M Mulder M J Teixeira de Mattos P W Postma K van Dam 《Biochimica et biophysica acta》1986,851(2):223-228
204.
205.
Picon A de Mattos MJ Postma PW 《Journal of industrial microbiology & biotechnology》2008,35(4):213-218
During Escherichia coli growth on glucose, uptake exceeds the requirement of flux to precursors and the surplus is excreted as acetate. Beside the loss of carbon source, the excretion of a weak acid may result in increased energetic demands and hence a decreased yield. The deletion of ptsG, the gene coding for one of the components (IICB(Glc)) of the glucose-phosphoenolpyruvate phosphotransferase system (Glc-PTS) reduced glucose consumption and acetate excretion. Induction of protein production at the onset of cultivation decreased growth rate and glucose consumption rate for both the WT and the mutant strains. The mutant strain produced beta-galactosidase at higher rates than the wild-type strain while directing more carbon into biomass and CO(2) and less into acetate. 相似文献
206.
207.
Thatcher WW Moreira F Santos JE Mattos RC Lopes FL Pancarci SM Risco CA 《Theriogenology》2001,55(1):75-89
Developments in the use of drugs to improve reproduction and embryo production have focused on estrus and ovulation synchronization protocols and embryonic survival. Protocols for synchronization of ovulation eliminate the need for detection of estrus and allow timed insemination of all cows enrolled. Various estrogenic, progestational, GnRH and PGF2 alpha-like drugs are used to synchronize follicle development, CL regression and induction of ovulation. Strategies are discussed to optimize such programs to maximize herd pregnancy rates. Use of bovine Somatotrophin (bST) in combination with the Ovsynch protocol resulted in increased pregnancy rates, indicating possible effects on oocyte and embryonic development. Treatment of embryo donor cows with bST reduced the proportion of unfertilized oocytes and increased the number of transferable embryos. Furthermore, bST increased pregnancy rate when given to the recipient. Sub-luteal plasma progesterone concentrations after insemination have been associated with lower pregnancy rates. Injection of hCG on day 5 post-insemination resulted in induction of an accessory CL, increased plasma progesterone concentrations and increased conception rates. Strategies involving the use of sustained GnRH agonists to enhance CL development and alter follicular development are considered for future programs to enhance pregnancy rates. 相似文献
208.
Three cases of Cryptococcus neoformans var. gattii infection in AIDS patients observed in Rio Grande do Sul (Brazil) are related. A brief comment on the epidemiology of cryptococcosis in Brazil is also made. 相似文献
209.
Arêas AP Oliveira ML Ramos CR Sbrogio-Almeida ME Raw I Ho PL 《Protein expression and purification》2002,25(3):481-487
Cholera toxin B subunit (CTB) has been extensively studied as immunogen, adjuvant, and oral tolerance inductor depending on the antigen conjugated or coadministered. It has been already expressed in several bacterial and yeast systems. In this study, we synthesized a versatile gene coding a 6XHis-tagged CTB (359bp). The sequence was designed according to codon usage of Escherichia coli, Lactobacillus casei, and Salmonella typhimurium. The gene assembly was based on a polymerase chain reaction, in which the polymerase extends DNA fragments from a pool of overlapping oligonucleotides. The synthetic gene was amplified, cloned, and expressed in E. coli in an insoluble form, reaching levels about 13 mg of purified active pentameric rCTB per liter of induced culture. Western blot and ELISA analyses showed that recombinant CTB is strongly and specifically recognized by polyclonal antibodies against the cholera toxin. The ability to form the functional pentamers was observed in cell culture by the inhibition of cholera toxin activity on Y1 adrenal cells in the presence of recombinant CTB. The 6XHis-tagged CTB provides a simple way to obtain functional CTB through Ni(2+)-charged resin after refolding and also free of possible CTA contaminants as in the case of CTB obtained from Vibrio cholerae cultures. 相似文献
210.