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61.
62.
Steen A Buist G Horsburgh GJ Venema G Kuipers OP Foster SJ Kok J 《The FEBS journal》2005,272(11):2854-2868
AcmA, the major autolysin of Lactococcus lactis MG1363 is a modular protein consisting of an N-terminal active site domain and a C-terminal peptidoglycan-binding domain. The active site domain is homologous to that of muramidase-2 of Enterococcus hirae, however, RP-HPLC analysis of muropeptides released from Bacillus subtilis peptidoglycan, after digestion with AcmA, shows that AcmA is an N-acetylglucosaminidase. In the C-terminus of AcmA three highly similar repeated regions of 45 amino acid residues are present, which are separated by short nonhomologous sequences. The repeats of AcmA, which belong to the lysine motif (LysM) domain family, were consecutively deleted, removed, or, alternatively, one additional repeat was added, without destroying the cell wall-hydrolyzing activity of the enzyme in vitro, although AcmA activity was reduced in all cases. In vivo, proteins containing no or only one repeat did not give rise to autolysis of lactococcal cells, whereas separation of the producer cells from the chains was incomplete. Exogenously added AcmA deletion derivatives carrying two repeats or four repeats bound to lactococcal cells, whereas the derivative with no or one repeat did not. In conclusion, these results show that AcmA needs three LysM domains for optimal peptidoglycan binding and biological functioning. 相似文献
63.
Single-stranded circular DNA generated from broad host range plasmid R1162 and its derivatives 总被引:1,自引:0,他引:1
Extraction of R1162 plasmid DNA with the alkaline lysis method yields considerable amounts of single-stranded circular plasmid DNA. Destabilization of plasmid DNA is stimulated by the R1162 mob region in cis. The formation of single-stranded circular DNA is initiated at a specific site on the plasmid, presumably the origin of transfer (oriT). 相似文献
64.
Prat C Bestebroer J de Haas CJ van Strijp JA van Kessel KP 《Journal of immunology (Baltimore, Md. : 1950)》2006,177(11):8017-8026
Bacteria have developed mechanisms to escape the first line of host defense, which is constituted by the recruitment of phagocytes to the sites of bacterial invasion. We previously described the chemotaxis inhibitory protein of Staphylococcus aureus, a protein that blocks the activation of neutrophils via the formyl peptide receptor (FPR) and C5aR. We now describe a new protein from S. aureus that impaired the neutrophil responses to FPR-like1 (FPRL1) agonists. FPRL1 inhibitory protein (FLIPr) inhibited the calcium mobilization in neutrophils stimulated with MMK-1, WKYMVM, prion-protein fragment PrP(106-126), and amyloid beta(1-42). Stimulation with low concentrations of fMLP was partly inhibited. Directed migration was also completely prevented toward MMK-1 and partly toward fMLP. Fluorescence-labeled FLIPr efficiently bound to neutrophils, monocytes, B cells, and NK cells. HEK293 cells transfected with human C5aR, FPR, FPRL1, and FPRL2 clearly showed that FLIPr directly bound to FPRL1 and, at higher concentrations, also to FPR but not to C5aR and FPRL2. FLIPr can reveal unknown inflammatory ligands crucial during S. aureus infections. As a novel described FPRL1 antagonist, it might lead to the development of therapeutic agents in FPRL1-mediated inflammatory components of diseases such as systemic amyloidosis, Alzheimer's, and prion disease. 相似文献
65.
Yan Yan Chen Jin Ping Wang Ya Yun Jiang Hui Li Ying Hua Hu Kok Onn Lee Guang Wei Li 《PloS one》2015,10(6)
Background
The association between hyperinsulinemia and obesity is well known. However, it is uncertain especially in childhood obesity, if initial fasting hyperinsulinemia predicts obesity, or obesity leads to hyperinsulinemia through insulin resistance.Objective
To investigate the predictive effect of fasting plasma insulin on subsequent weight change after a 5-year interval in childhood.Methods
424 Children from Da Qing city, China, were recruited at 5 years of age and followed up for 5 years. Blood pressure, anthropometric measurements, fasting plasma insulin, glucose and triglycerides were measured at baseline and 5 years later.Results
Fasting plasma insulin at 5 years of age was significantly correlated with change of weight from 5 to 10 years (ΔWeight). Children in the lowest insulin quartile had ΔWeight of 13.08±0.73 kg compare to 18.39±0.86 in the highest insulin quartile (P<0.0001) in boys, and similarly 12.03±0.71 vs 15.80±0.60 kg (P<0.0001) in girls. Multivariate analysis showed that the predictive effect of insulin at 5 years of age on subsequent weight gain over 5 years remained statistically significant even after the adjustment for age, sex, birth weight, TV-viewing time and weight (or body mass index) at baseline. By contrast, the initial weight at 5 years of age did not predict subsequent changes in insulin level 5 years later. Children who had both higher fasting insulin and weight at 5 years of age showed much higher levels of systolic blood pressures, fasting plasma glucose, the homeostasis model assessment for insulin resistance (HOMA-IR) and triglycerides at 10 years of age.Conclusions
Fasting plasma insulin at 5 years of age predicts weight gain and cardiovascular risk factors 5 year later in Chinese children of early childhood, but the absolute weight at 5 years of age did not predict subsequent change in fasting insulin. 相似文献66.
Identification of a gene required for maturation of an extracellular lactococcal serine proteinase. 总被引:18,自引:4,他引:18 下载免费PDF全文
A J Haandrikman J Kok H Laan S Soemitro A M Ledeboer W N Konings G Venema 《Journal of bacteriology》1989,171(5):2789-2794
Directly upstream of the Lactococcus lactis subsp. cremoris Wg2 proteinase gene is an oppositely directed open reading frame (ORF1). The complete nucleotide sequence of ORF1, encoding a 33-kilodalton protein, was determined. A protein of approximately 32 kilodaltons was synthesized when ORF1 was expressed in Escherichia coli by using a T7 RNA polymerase-specific promoter. L. lactis subsp. lactis MG1363 transformants carrying the proteinase gene but lacking ORF1 were phenotypically proteinase deficient, unlike transformants carrying both the proteinase gene and ORF1. Synthesis and secretion of proteinase antigen by L. lactis could be detected with proteinase-directed monoclonal antibodies regardless of whether ORF1 was present. The requirement of ORF1 for proteinase activation was reflected in a reduction in the molecular weight of the secreted proteinase. Furthermore, deletion of the 130 C-terminal amino acids of the Wg2 proteinase prevented attachment of the enzyme to lactococcal cells. 相似文献
67.
Mode of action of LciA, the lactococcin A immunity protein 总被引:6,自引:1,他引:6
K. Venema R. E. Haverkort T. Abee A. J. Haandrikman K. J. Leenhouts L. de Leij G. Venema J. Kok 《Molecular microbiology》1994,14(3):521-532
Monoclonal antibodies were raised against a fusion between the Escherichia coli maltose-binding protein and LciA, the immunity protein that protects Lactococcus lactis against the effects of the bacteriocin lactococcin A. One of the antibodies directed against the LciA moiety of the fusion protein was used to locate the immunity protein in the L. lactis producer cell. LciA was present in the cytosolic. the membrane-associated, and the membrane fractions in roughly equal amounts, irrespective of the production by the cells of lactococcin A. The monoclonal antibody specifically reacted with right-side-out vesicles obtained from a strain producing the immunity protein. It did not react with inside-out vesicles of the same strain, or with right-side-out vesicles obtained from a strain producing both LciA and lactococcin A. Also, externally added lactococcin A blocked the interaction between the antibody and right-side-out vesicles obtained from a strain producing only LciA. The epitope in LciA was localized between amino acid residues 60 and 80. As the epitope could be removed from right-side-out vesicles by proteinase K, it is located at the outside of the cell. The immunity protein contains a putative a-amphiphilic helix from residue 29 to 47. A model is proposed in which this helix is thought to traverse the membrane in such a way that the C-terminal part of the protein, containing the epitope, is on the outside of the cell. Vesicle-fusion studies together with leucine-uptake experiments suggest that the immunity protein interacts with the putative receptor for lactococcin A, thus preventing pore formation by the bacteriocin. 相似文献
68.
Fui Chin Chong Beng Ti Tey Zanariah Mohd Dom Kok Hing Cheong Budiatman Satiawihardja Mohd Nordin Ibrahim Russly Abdul Rahman Dayang Radiah Awang Biak Tau Chuan Ling 《Biotechnology and Bioprocess Engineering》2007,12(3):250-256
Rice bran lipase (RBL) was delipidated to enhance its stability in organic solvent and its esterification activity at elevated
temperature. The esterification activity of delipidated RBL increased as temperature was increased from 45 to 65°C. The esterification
activity of delipidated RBL at 65°C was about 14 times greater than that of the non-delipidated RBL. As temperature was further
increased to 75°C, the non-delipidated RBL lost all esterification activity, whereas the delipidated RBL retained approximately
48% of its esterilication activity. The delipidated RBL maintained a relative esterification activity greater than 80% after
16 h of incubation in hexane, whereas the non-delipidated RBL maintained a relative esterification activity of only 50%. A
method for production of acylglycerol using delipidated RBL to esterify palm oil fatty acid distillate (PFAD) with glycerol
in hexane was successfully developed. The effects of reaction temperatures and type of water removal agents (silica gel and
molecular sieve) on the degree of esterification were also examined. A 4 h reaction at 65°C, catalyzed by delipidated RBL
and using silica gel as the water removal agent resulted in 53.8% esterification. Thin layer chromatography analysis suggested
that the esterified product was primarily comprised of mono-and di-acylglycerols. 相似文献
69.
Lipoamide dehydrogenase from Azotobacter vinelandii. Molecular cloning, organization and sequence analysis of the gene 总被引:11,自引:0,他引:11
The gene encoding lipoamide dehydrogenase from Azotobacter vinelandii has been cloned in Escherichia coli. Fragments of 9-23 kb from Azotobacter vinelandii chromosomal DNA obtained by partial digestion with Sau3A were ligated into the BamHI site of plasmid pUC9. E. coli TG2 cells were transformed with the resulting recombinant plasmids. Screening for clones which produced A. vinelandii lipoamide dehydrogenase was performed with antibodies raised against the purified enzyme. A positive colony was found which produced complete chains of lipoamide dehydrogenase as concluded form SDS gel electrophoresis of the cell-free extract, stained for protein or used for Western blotting. After subcloning of the 14.7-kb insert of this plasmid the structural gene could be located on a 3.2-kb DNA fragment. The nucleotide sequence of this subcloned fragment (3134 bp) has been determined. The protein-coding sequence of the gene consists of 1434 bp (478 codons, including the AUG start codon and the UAA stop codon). It is preceded by an intracistronic region of 85 bp and the structural gene for succinyltransferase. A putative ribosome-binding site and promoter sequence are given. The derived amino acid composition is in excellent agreement with that previously published for the isolated enzyme. The predicted relative molecular mass is 50223, including the FAD. The overall homology with the E. coli enzyme is high with 40% conserved amino acid residues. From a comparison with the three-dimensional structure of the related enzyme glutathione reductase [Rice, D. W., Schultz, G. E. & Guest, J. R. (1984) J. Mol. Biol. 174, 483-496], it appears that essential residues in all four domains have been conserved. The enzyme is strongly expressed, although expression does not depend on the vector-encoded lacZ promoter. The cloned enzyme is, in all the respects tested, identical with the native enzyme. 相似文献
70.
P M de Kok N A Beijer H M Buck L A Sluyterman E M Meijer 《European journal of biochemistry》1988,175(3):581-585
The geometry of seven NAD+ analogues bound to horse liver alcohol dehydrogenase (LADH) modified only in their nicotinamide group, have been studied using AMBER molecular mechanics energy-minimization procedures. Starting geometries were taken from X-ray crystallographic data for NAD+/Me2SO/LADH reported by Eklund and co-workers. In this study the NAD+ analogues were encaged by the constituent amino acids of the enzyme within a range of 0.6 nm from the initial NAD+/Me2SO/Zn2+ complex. The calculational method used is able to rationalize individual substituent effects and to evaluate the essential interactions between NAD+ analogue, enzyme, Me2SO and Zn2+ without the necessity of additional X-ray data. The results presented here demonstrate that the reactivity of NAD+ derivatives as reported in literature can be qualitatively related to the position of the pyridine moiety in the active site. 相似文献