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981.
Makoto Murakami 《Journal of Protein Chemistry》1993,12(6):783-789
Various reports have described that amino acid substitutions can alter substrate, positional, inhibitory, and target gene specificities of proteins. By using the method of Chou and Fasman, the present work predicts that critical amino acids for converting these specificities are located around -turns. Residues responsible for the alterations of substrate specificities of trypsin,l-lactate dehydrogenase, aspartate aminotransferase, -lactamase, and cytochrome P-450 are found to exist within regions predicted as -turns. The ratios of hydroxylation and oxygenation positions of substrates by cytochrome P-450 and lipoxygenase, respectively, are varied by changes of the protein structures, probably around turn conformations. Inhibitory specificities of bovine pancreatic trypsin inhibitor and 1-antitrypsin and target gene specificity of glucocorticoid receptor are converted by changing turn structures. Occurrence of -turn probabilities can be predicted around the amino acid alteration positions of an evolutionally antecedent protein of a nylon degradation enzyme. These findings will have relevance to work on protein engineering and enzyme evolution. 相似文献
982.
983.
Actinote anteas from Costa Rica was screened as a biological control candidate forChromolaena odorata in South Africa. Preliminary starvation trials suggest thatA. anteas is species specific. There are seven larval instars and the life cycle is completed in 101–169 days. The culture died out
after three generations possibly because of incompatibility with the form of the local species ofC. odorata or disease. 相似文献
984.
Substitution of the amino acid at position 102 with polar and aromatic residues influences substrate specificity of lactate dehydrogenase 总被引:1,自引:0,他引:1
David J. Nicholls Margaret Davey Susan E. Jones Julie Miller J. John Holbrook Anthony R. Clarke Michael D. Scawen Tony Atkinson Christopher R. Goward 《Journal of Protein Chemistry》1994,13(1):129-133
The Gin residue at amino acid position 102 ofBacillus stearothermophilus lactate dehydrogenase was replaced with Ser, Thr, Tyr, or Phe to investigate the effect on substrate recognition. The Q102S and Q102T mutant enzymes were found to have a broader range of substrate specificity (measured byk
cat/K
m) than the wild-type enzyme. However, it is evident that either Ser or Thr at position 102 are of a size able to accommodate a wide variety of substrates in the active site and substrate specificity appears to rely largely on size discrimination in these mutants. The Q102F and Q102Y mutant enzymes have low catalytic efficiency and do not show this relaxed substrate specificity. However, their activities are restored by the presence of an aromatic substrate. All of the enzymes have a very low catalytic efficiency with branched chain aliphatic substrates.Abbreviations used BSLDH
Bacillus stearothermophilus lactate dehydrogenase
- FBP
fructose-1,6-bisphosphate
- HP
hydroxypyruvate
- KB
ketobutyrate
- KC
ketocaproate
- KV
ketovalerate
- MDH
malate dehydrogenase
- PP
phenylpyruvate
- PYR
pyruvate
- RBE
relative binding energy 相似文献
985.
Remy Loris Florence Casset Julie Bouckaert Jurgen Pletinckx Minh-Hoa Dao-Thi Freddy Poortmans Anne Imberty Serge Perez Lode Wyns 《Glycoconjugate journal》1994,11(6):507-517
The X-ray crystal structure of lentil lectin in complex with -d-glucopyranose has been determined by molecular replacement and refined to anR-value of 0.20 at 3.0 Å resolution. The glucose interacts with the protein in a manner similar to that found in the mannose complexes of concanavalin A, pea lectin and isolectin I fromLathyrus ochrus. The complex is stabilized by a network of hydrogen bonds involving the carbohydrate oxygens O6, O4, O3 and O5. In addition, the -d-glucopyranose residue makes van der Waals contacts with the protein, involving the phenyl ring of Phe123. The overall structure of lentil lectin, at this resolution, does not differ significantly from the highly refined structures of the uncomplexed lectin.Molecular docking studies were performed with mannose and its 2-O and 3-O-m-nitro-benzyl derivatives to explain their high affinity binding. The interactions of the modelled mannose with lentil lectin agree well with those observed experimentally for the protein-carbohydrate complex. The highly flexible Me-2-O-(m-nitro-benzyl)--d-mannopyranoside and Me-3-O-(m-nitro-benzyl)--d-mannopyranoside become conformationally restricted upon binding to lentil lectin. For best orientations of the two substrates in the combining site, the loss of entropy is accompanied by the formation of a strong hydrogen bond between the nitro group and one amino acid, Gly97 and Asn125, respectively, along with the establishment of van der Waals interactions between the benzyl group and the aromatic amino acids Tyr100 and Trp128.RL and FC are joint first authors. 相似文献
986.
BRIGITTE BANNERT 《The Journal of eukaryotic microbiology》1994,41(3):183-188
ABSTRACT. Cross-transmission experiments were performed in order to determine the host specificity in the intermediate and definitive hosts of the four described dihomoxenous Sarcocystis species, S. gallotiae, S. stehlinii, S. simonyi , and S. dugesii from lacertid lizards of the genera Gallotia and Podarcis from the Macaronesian Islands. Sarcocysts of either species from experimentally infected lizards were fed to a variety of laboratory-bred lizard species of the genera Gallotia, Lacerta , and Podarcis . These sarcocysts proved to be infectious to all examined animals, showing no definitive host specificity in the tested genera. Lizards of the genera Chalcides and Tarentola , however, were not susceptible definitive hosts for S. gallotiae . The inoculation of experimentally obtained sporocysts of each of the four Sarcocystis species to various lacertid lizard species revealed varying degrees of intermediate host specificity, generally demonstrating each native host to be the most susceptible. 相似文献
987.
An Expression Profile of Active Genes in Human Lung 总被引:1,自引:0,他引:1
Itoh Kohichi; Okubo Kousaku; Yosii Junji; Yokouchi Hideoki; Matsubara Kenichi 《DNA research》1994,1(6):279-287
An expression profile ofgenes active in the human lung was obtainedby collecting 797 partial sequences from a 3'-directed cDNAlibrary. Three genes were found to produce mRNA each of whichcomprised more than 1% of total mRNA. These three have beenidentified as genes for pulmonary surfactant apoprotein (PSP-A),Clara cells 10-kDa secretory protein, and HLA-E heavy chain.In the remaining 745 clones, 221 were composed of89 speciesthat occurred recurrently, and 524 clones appeared only once.Because the 3'-directed cDNA library faithfully represents themRNA population in the source tissue, these numbers representthe relative activities ofthe gene expression. Altogether 437gene species were novel, and 179 gene species were identifiedin GenBank. A significant portion ofthese genes encode proteinsfound in secretory proteins, cell surface proteins, and componentsin the protein synthesis machinery, representing the functionof the lung. 相似文献
988.
989.
990.
Summary Nuclear poly(A)+ RNA was isolated from gastrula and early tadpole stages ofXenopus laevis, transcribed into cDNA and integrated as double stranded cDNA by the G-C joining method into the Pst cleavage site of plasmid pBR 322. After cloning inE. coli strain HB 101 the clone libraries were hybridized to32P labelled cDNA derived from nuclear poly(A)+ RNA of the two different developmental stages. About 20% of the clones gave a positive hybridization signal thus representing RNA molecules of high and medium abundance. From these clones, some individual clones were identified containing sequences which are not present at the oocyte and gastrula stages but which are transcribed at the early tadpole stage of embryonic development. 相似文献