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排序方式: 共有1313条查询结果,搜索用时 15 毫秒
1.
Tanner Miest Dyana Saenz Anne Meehan Manuel Llano Eric M. Poeschla 《Methods (San Diego, Calif.)》2009,47(4):298-303
RNAi is a powerful technology for analyzing gene function in human cells. However, its utility can be compromised by inadequate knockdown of the target mRNA or by interpretation of effects without rigorous controls. We review lentiviral vector-based methods that enable transient or stable knockdowns to trace mRNA levels in human CD4+ T cell lines and other targets. Critical controls are reviewed, including rescue of the pre-knockdown phenotype by re-expression of the targeted gene. The time from thinking about a potential knockdown target to analysis of phenotypes can be as short as a few weeks. 相似文献
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W Tanner A Haselbeck H Schwaiger L Lehle 《Philosophical transactions of the Royal Society of London. Series B, Biological sciences》1982,300(1099):185-194
The pathways for protein N- and O-glycosylation in yeast cells are summarized. Evidence is presented that the terminal glucosyl residues of the dolichyl-PP-oligosaccharide intermediate are responsible for decreasing the Km for the peptide to be N-glycosylated. A liposomal model system is introduced that allows the study of a dolichyl phosphate (Dol-P) dependent transmembrane transport of mannosyl residues. The results obtained so far suggest that the mannosylation of Dol-P and the transmembrane translocation of Dol-P-Man are catalysed by the enzyme more or less simultaneously. However, only about 8-10% of the enzyme molecules incorporated into the liposomes seem to carry out the 'coupled' reaction. The glycosylation of carboxypeptidase Y is not required for this protein to reach the vacuole, its target organelle. In the presence of low concentrations of tunicamycin, however, yeast cells do stop growth. This does not seem to be due to the inhibition of secretion of glycoproteins like external invertase. It is postulated that protein glycosylation is crucial for a cell cycle event during the G1 phase. 相似文献
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Due to research on biochemistry and genetic engineering, mathematical models of microbial growth have become more complicated but Michaelis-Menten or Monod type expressions have still been used for conversion rates, uptake rates, etc. It is worth examining the error that can be caused by these quasi-steady-state-hypotheses. This paper presents a simple but very effective rationale function that describes the error of the quasi-steady-state hypothesis in enzyme kinetics. A simplified fermentation kinetic model was used for comparison of microbial growth but no analytical error function has been found for batch cultivation. In the case of continuous fermentation the error can be given in an analytical form. Many simulations, based on real SCP experiments, show a significant effect of the quasi-steady-state hypothesis. Since the rate constants of intracellular events are not really known, we have to be very careful when taking into account Michaelis-Menten type expressions in the building of complicated models.
Correspondence to: L. Szigeti 相似文献
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Young leaf and internodal stem segments of Gaillardia pulchella, collected from wild species re-established in the greenhouse, were used to initiate callus on Murashige & Skoog medium supplemented
with NAA (2.0 mgl−1) and BA (0.4 mgl−1). Callus formed after 10 to 14 days in the dark. Cultures were transferred to fresh medium and placed under lighted conditions
where shoot formation occurred approximately 14 to 30 days after initiation. Callus sub-cultured at 14 to 21-day intervals
continued to produce primordia for several weeks. Flowers were produced by regenerated shoots maintained on MS medium, but
roots did not develop until the plantlets were transferred to soil conditions. 相似文献
9.
K Kitagawa B S Rosen B M Spiegelman G E Lienhard L I Tanner 《Biochimica et biophysica acta》1989,1014(1):83-89
The release of adipsin, a serine proteinase with complement factor D activity, from 3T3-L1 adipocytes was measured by quantitative immunoblotting. This protein is secreted constitutively from 3T3-L1 adipocytes, and there is a 2-fold increase in the amount of adipsin released from cells treated with insulin for 1 to 10 min. Longer exposure to insulin had no further effect on the rate of adipsin release. Adipsin does not appear to be anchored by a glycosylphosphatidylinositol moiety, since adipsin which was been released with Triton X-114 from an intracellular membrane fraction partitions into the aqueous phase. Using a previously described procedure for the isolation of vesicles containing the insulin-responsive intracellular glucose transporters (GT vesicles), we show here that these GT vesicles contain an insulin-responsive pool of adipsin. Thus, insulin stimulates the secretion of a soluble protein, adipsin, as well as translocation to the plasma membrane of integral membrane proteins, including the glucose transporter, the transferrin receptors, and the insulin-like growth factor II receptor. 相似文献
10.
Purification and characterization of the inducible a agglutinin of Saccharomyces cerevisiae. 总被引:17,自引:2,他引:15 下载免费PDF全文
A cell surface glycoprotein induced by the mating pheromone alpha factor in Saccharomyces cerevisiae a cells has been purified to homogeneity. At 4 x 10(-9) M it strongly inhibits mating-type-specific agglutination between a and alpha cells. The protein is solely O-glycosylated. It consists of 29% carbohydrate and its apparent molecular mass is 22 kd on SDS gels. After HF treatment it behaves like a protein of 13 kd; therefore its true molecular mass probably is close to 18 kd. Mild periodate treatment destroys the biological activity of the purified protein. The protein contains one cysteine, no arginine, and 27% of the amino acids are serine and threonine residues, two thirds of which are glycosylated. With a polyclonal antibody the glycoprotein can already be detected at the cell surface 15 min after pheromone addition. The inducible antigen is not expressed in a specific phase of the cell cycle; it first appears exclusively on the growing bud. Mother cells express the antigen on their surface only after the daughter cells have separated; it is then localized at the tip of the pear-shaped 'shmoo'. Using the secretory ts-mutant sec 18 is shown that a mannosylated precursor of a agglutinin accumulates at the endoplasmic reticulum. 相似文献