全文获取类型
收费全文 | 299篇 |
免费 | 13篇 |
出版年
2021年 | 3篇 |
2017年 | 2篇 |
2016年 | 2篇 |
2015年 | 7篇 |
2014年 | 7篇 |
2013年 | 2篇 |
2012年 | 12篇 |
2011年 | 9篇 |
2010年 | 8篇 |
2009年 | 12篇 |
2008年 | 19篇 |
2007年 | 16篇 |
2006年 | 13篇 |
2005年 | 19篇 |
2004年 | 18篇 |
2003年 | 12篇 |
2002年 | 9篇 |
2001年 | 9篇 |
2000年 | 9篇 |
1999年 | 18篇 |
1996年 | 1篇 |
1995年 | 2篇 |
1994年 | 6篇 |
1993年 | 4篇 |
1992年 | 10篇 |
1991年 | 5篇 |
1990年 | 8篇 |
1989年 | 6篇 |
1988年 | 3篇 |
1987年 | 4篇 |
1986年 | 7篇 |
1985年 | 2篇 |
1984年 | 5篇 |
1983年 | 2篇 |
1982年 | 3篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1978年 | 3篇 |
1976年 | 3篇 |
1975年 | 3篇 |
1974年 | 1篇 |
1972年 | 2篇 |
1971年 | 4篇 |
1970年 | 2篇 |
1969年 | 2篇 |
1968年 | 3篇 |
1967年 | 1篇 |
1966年 | 1篇 |
1964年 | 2篇 |
排序方式: 共有312条查询结果,搜索用时 390 毫秒
11.
We measured a tubular brush-border enzyme (alanine aminopeptidase, AAP) and a lysosomal hydrolase (N-acetyl-beta-D-glucosaminidase, NAG) in morning urines from 15 healthy normal subjects to check if different storage times and temperatures could modify enzyme concentrations. Short-term (24 h) storage time at room temperature or 4 degrees C does not affect AAP and NAG activities. Both enzymes are well preserved at -70 degrees C. AAP dramatically falls after 1 month at -20 degrees C, lowering to about 8% of the initial value after only 4 days of storage. On the contrary, NAG is well preserved at these storage conditions. Centrifugation has revealed not critical for measurement of these two enzymes. 相似文献
12.
A sensitive and precise automated assay of urinary lactate dehydrogenase (EC 1.1.1.27), alkaline phosphatase (EC 3.1.3.1) and gamma-glutamyltransferase (EC 2.3.2.2) is described. For this purpose, we used a BM/Hitachi System 704 model and reagents for automated analysis of serum enzymes from Boehringer Mannheim. However, the schedules of enzyme chemistry parameters recorded by the autoanalyzer and the spectrophotometric calibration are reprogrammed to meet requirements deriving from urine adoption and to optimize the enzyme assay in this unusual medium. 相似文献
13.
Hydrolysis by horse muscle acylphosphatase of (Ca2+ + Mg2+)-ATPase phosphorylated intermediate 总被引:1,自引:0,他引:1
M Stefani G Liguri A Berti P Nassi G Ramponi 《Archives of biochemistry and biophysics》1981,208(1):37-41
Horse muscle acylphosphatase (EC 3.6.1.7) was found to hydrolyze the labeled phosphorylated intermediate of (Ca2+ + Mg2+)-ATPase from rabbit muscle. In addition, the phosphorylated peptides obtained by pepsin digestion of the labeled phosphorylated microsomes were completely hydrolyzed by acylphosphatase. These findings suggest a possible regulatory role of this enzyme in vivo on the calcium transport process by sarcoplasmic reticulum. 相似文献
14.
15.
Nonenzymatic acetylation of calf-thymus lysine- and arginine-rich histones was demonstrated to occur when these proteins were incubated with [14C]acetyl phosphate and [14C]acetyl adenylate. The levels of acetylation depend on both pH and on reagent concentration. When acetyl [33P]phosphate and acetyl [3H]adenylate were used as reagents, we found neither histone phosphorylation nor adenylylation. Most of the radioactivity of 14C-labeled acetylated histones was recovered as Ne-acetyllysine. Furthermore, only a small amount of O-bound radioactivity was released by the 14C-labeled acetylated arginine-rich histone during treatment with hydroxylamine. Experiments on the acetylation of histones, in the presence of increasing salt concentration, gave different results for the two acetylating agents. 相似文献
16.
We have predicted the secondary structure of horse muscle acylphosphatase by the statistical method of Chou and Fasman. In addition, we have studied the circular dichroism spectra of the enzyme, obtaining values for comparison to the predicted results. Discrepancies were found for the alpha-helix content estimated by the two methods. 相似文献
17.
Zaida Araujo Francesca Giampietro María de los Angeles Bochichio Andrea Palacios Jenifer Dinis Jaime Isern Jacobus Henry de Waard Elsa Rada Rafael Borges Carlos Fernández de Larrea Angel Villasmil Magnolia Vanegas Jose Antonio Enciso-Moreno Manuel Alfonso Patarroyo 《Memórias do Instituto Oswaldo Cruz》2013,108(2):131-139
The goal of this study was to demonstrate the usefulness of an enzyme-linked immunosorbent assay (ELISA) for the serodiagnosis of pulmonary tuberculosis (PTB) and extrapulmonary TB (EPTB). This assay used 20 amino acid-long, non-overlapped synthetic peptides that spanned the complete Mycobacterium tuberculosis ESAT-6 and Ag85A sequences. The validation cohort consisted of 1,102 individuals who were grouped into the following five diagnostic groups: 455 patients with PTB, 60 patients with EPTB, 40 individuals with non-EPTB, 33 individuals with leprosy and 514 healthy controls. For the PTB group, two ESAT-6 peptides (12033 and 12034) had the highest sensitivity levels of 96.9% and 96.2%, respectively, and an Ag85A-peptide (29878) was the most specific (97.4%) in the PTB groups. For the EPTB group, two Ag85A peptides (11005 and 11006) were observed to have a sensitivity of 98.3% and an Ag85A-peptide (29878) was also the most specific (96.4%). When combinations of peptides were used, such as 12033 and 12034 or 11005 and 11006, 99.5% and 100% sensitivities in the PTB and EPTB groups were observed, respectively. In conclusion, for a cohort that consists entirely of individuals from Venezuela, a multi-antigen immunoassay using highly sensitive ESAT-6 and Ag85A peptides alone and in combination could be used to more rapidly diagnose PTB and EPTB infection. 相似文献
18.
Villard V Agak GW Frank G Jafarshad A Servis C Nébié I Sirima SB Felger I Arevalo-Herrera M Herrera S Heitz F Bäcker V Druilhe P Kajava AV Corradin G 《PloS one》2007,2(7):e645
To identify malaria antigens for vaccine development, we selected alpha-helical coiled coil domains of proteins predicted to be present in the parasite erythrocytic stage. The corresponding synthetic peptides are expected to mimic structurally "native" epitopes. Indeed the 95 chemically synthesized peptides were all specifically recognized by human immune sera, though at various prevalence. Peptide specific antibodies were obtained both by affinity-purification from malaria immune sera and by immunization of mice. These antibodies did not show significant cross reactions, i.e., they were specific for the original peptide, reacted with native parasite proteins in infected erythrocytes and several were active in inhibiting in vitro parasite growth. Circular dichroism studies indicated that the selected peptides assumed partial or high alpha-helical content. Thus, we demonstrate that the bioinformatics/chemical synthesis approach described here can lead to the rapid identification of molecules which target biologically active antibodies, thus identifying suitable vaccine candidates. This strategy can be, in principle, extended to vaccine discovery in a wide range of other pathogens. 相似文献
19.
Fiaschi T Chiarugi P Buricchi F Giannoni E Taddei ML Talini D Cozzi G Zecchi-Orlandini S Raugei G Ramponi G 《The Journal of biological chemistry》2001,276(52):49156-49163
Low molecular weight protein-tyrosine phosphatase (LMW-PTP) is an enzyme involved in mitogenic signaling and cytoskeletal rearrangement after platelet-derived growth factor (PDGF) stimulation. Recently, we demonstrated that LMW-PTP is regulated by a redox mechanism involving the two cysteine residues of the catalytic site, which turn reversibly from reduced to oxidized state after PDGF stimulation. Since recent findings showed a decrease of intracellular reactive oxygen species in contact inhibited cells and a lower tyrosine phosphorylation level in dense cultures in comparison to sparse ones, we studied if the level of endogenous LMW-PTP is regulated by growth inhibition conditions, such as cell confluence and differentiation. Results show that both cell confluence and cell differentiation up-regulate LMW-PTP expression in C2C12 and PC12 cells. We demonstrate that during myogenesis LMW-PTP is regulated at translational level and that the protein accumulates at the plasma membrane. Furthermore, we showed that both myogenesis and cell-cell contact lead to a dramatic decrease of tyrosine phosphorylation level of PDGF receptor. In addition, we observed an increased association of the receptor with LMW-PTP during myogenesis. Herein, we demonstrate that myogenesis decreases the intracellular level of reactive oxygen species, as observed in dense cultures. As a consequence, LMW-PTP turns from oxidized to reduced form during muscle differentiation, increasing its activity in growth inhibition conditions such as differentiation. These data suggest that LMW-PTP plays a crucial role in physiological processes, which require cell growth arrest such as confluence and differentiation. 相似文献
20.
Paoli P Giannoni E Pescitelli R Camici G Manao G Ramponi G 《The Journal of biological chemistry》2001,276(45):41862-41869
Acylphosphatase is expressed in vertebrates as two molecular forms, the organ common and the muscle types. The former does not contain cysteine residues, whereas the latter contains a single conserved cysteine (Cys-21). We demonstrated that H(2)O(2) at micromolar levels induces, in vitro, the formation of a disulfide dimer of muscle acylphosphatase, which displays properties differing from those of the reduced enzyme. In particular, we observed changes in the kinetic behavior of its intrinsic ATPase activity, whereas the kinetic behavior of its benzoyl phosphatase activity does not change. Moreover, the disulfide dimer is capable of interacting with some polynucleotides such as poly(G), poly(C), and poly(T) but not with poly(A), whereas the reduced enzyme does not bind polynucleotides. Experiments performed with H(2)O(2) in the presence of increasing SDS concentrations demonstrated that disulfide dimer formation is prevented by SDS concentrations higher than 300 microm, suggesting that a non-covalently-linked dimer is present in non-denaturing solvents. Light-induced cross-linking experiments performed on the Cys-21 --> Ser mutant in the pH range 3.8-9.0 have demonstrated that a non-covalently-linked dimer is in fact present in non-denaturing solutions and that an enzyme group with a pK(a) of 6.4 influences the monomer-dimer equilibrium. 相似文献