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991.
Involvement of protein sulfhydryls in the trigger reaction of rhodotorucine A, a farnesyl peptide mating pheromone of Rhodosporidium toruloides. 总被引:2,自引:2,他引:0 下载免费PDF全文
T Miyakawa M Kaji T Yasutake Y K Jeong E Tsuchiya S Fukui 《Journal of bacteriology》1985,162(1):294-299
The involvement of protein sulfhydryls for the signaling of rhodotorucine A, a mating pheromone produced by mating type A cells of Rhodosporidium toruloides, was investigated by the use of sulfhydryl compounds. The sulfhydryl-blocking reagent 5,5'-dithiobis(2-nitrobenzoic acid) (DTNB; Ellman's reagent) strongly inhibited both the biological effect of the pheromone on the recipient cell and the hydrolysis of the pheromone, which is catalyzed by the mating type-specific surface endopeptidase of the recipient cell. Conversely, the two reactions were markedly enhanced by the presence of the reducing reagent dithiothreitol. The inhibitory effect of DTNB on the pheromone response of the recipient cell was specific to an initial stage of the differentiation; once it had initiated, the reagent had no effect on its progression. The results suggested that dithiothreitol enhances and DTNB impairs the efficiency with which the pheromone triggers sexual d differentiation. The reaction of DTNB with cellular protein sulfhydryls was highly restricted to those at the exterior surface of the membrane due to the impermeability of the reagent through the membrane. Phosphorylation of endogenous proteins, which is modulated by the pheromone added to an in vitro phosphorylation system, was also blocked by DTNB. The results showed that sulfhydryl groups are involved in the pheromone hydrolysis by the surface endopeptidase of the recipient cell and that pheromone metabolism is indispensable for the signaling reaction. We suggest that the modulation of protein phosphorylation of membrane proteins by the pheromone is an initial transmembrane response coupled to pheromone metabolism. 相似文献
992.
The vertical distribution of a bloom-forming Microcystis population was studied based on the relevant limnological parameters obtained from the lower Nakdong River (Mulgum) during
the summer of 1994. Over three months (late June to late September), a high abundance of Microcystis population (mean ± SD, 2.9 ± 8.4 × 105 cells ml−1, n = 40) and algal biomass (mean ± SD, chlorophyll a, 131 ± 346 μg l−1, n = 31) was persistent throughout the entire water column (0–5 m, n = 11). The vertical distribution of carbon content was uneven, with a high concentration near the surface zone (mean ± SD,
total, 7.9 ± 7.8; Microcystis, 5.2 ± 8.3 μg C ml−1, n = 15). Incorporating limnological and meteorological factors, a diel study of the vertical distribution of Microcystis showed that the chlorophyll a concentration was highest near the surface zone on a calm night (wind velocity, <2 m s−1, 2300–700) but was evenly distributed on a windy day (>4 m s−1, 1100–1900). Among many possible factors, wind velocity may have played an important role in controlling the vertical distribution
of Microcystis in the lower Nakdong River.
Received: July 12, 1999 / Accepted: November 15, 1999 相似文献
993.
Kwak HJ Pyun DK Kim JH Kim EJ Jeong HJ Kim BJ Lee CH 《Bioorganic & medicinal chemistry letters》2000,10(4):333-336
The 2alpha-functionalized 1beta-methylcarbapenems 3 were synthesized from the 2-formyl 1beta-methylcarbapenem intermediate 5. The best compound in the series of 2alpha-(hydroxy)alkylcarbapenems, KR-21012, displayed well balanced in vitro and in vivo activity as a parent compound of oral carbapenem. 相似文献
994.
New partially N-hydroxyethylated 14-membered tetraaza macrocycles 1,8-bis(2-hydroxyethyl)-3,5,7,7,10,12,14,14-octamethyl-1,4,8,11-tetraazacyclotetradecane (L2) and 1-(2-hydroxyethyl))-3,5,7,7,10,12,14,14-octamethyl-1,4,8,11-tetraazacyclotetradecane (L3) have been synthesized selectively by the one-step reaction of 2,5,5,7,9,12,12,14-octamethyl-1,4,8,11-tetraazacyclotetradecane (L1) with 2-hydroxyethyl bromide. The complexes [NiL3]2+, [CuL2]2+, and [CuL3]2+ have been prepared and characterized. The complex [CuL2](ClO4)2 has a square-pyramidal coordination geometry with one apical oxygen atom; only one of the two hydroxyethyl groups is coordinated to the metal ion. Electronic absorption spectra of [CuL3](ClO4)2 containing one hydroxyethyl pendant arm indicate that the geometry is similar to that of [CuL2](ClO4)2. Unexpectedly, the nickel(II) complex [NiL3](ClO4)2 has a severely distorted trigonal bipyramidal coordination geometry with the oxygen atom of the pendant arm at the equatorial position. The Ni---O bond distance of the nickel(II) complex is shorter, or not longer, than the Ni---N bond distances. The ligand in [CuL2]2+ is in the RRSS (trans-III) configuration, as usual, whereas that in [NiL3]2+ has the RRRR (trans-V) conformation. The coordination geometry and properties of [NiL3]2+ are quite different from those reported for other related nickel(II) complexes containing one functional pendant arm. 相似文献
995.
Transformation of 2,4,6-Trinitrotoluene by Purified Xenobiotic Reductase B from Pseudomonas fluorescens I-C 总被引:2,自引:0,他引:2 下载免费PDF全文
Jeong W. Pak Kyle L. Knoke Daniel R. Noguera Brian G. Fox Glenn H. Chambliss 《Applied microbiology》2000,66(11):4742-4750
The enzymatic transformation of 2,4,6-trinitrotoluene (TNT) by purified XenB, an NADPH-dependent flavoprotein oxidoreductase from Pseudomonas fluorescens I-C, was evaluated by using natural abundance and [U-14C]TNT preparations. XenB catalyzed the reduction of TNT either by hydride addition to the aromatic ring or by nitro group reduction, with the accumulation of various tautomers of the protonated dihydride-Meisenheimer complex of TNT, 2-hydroxylamino-4,6-dinitrotoluene, and 4-hydroxylamino-2,6-dinitrotoluene. Subsequent reactions of these metabolites were nonenzymatic and resulted in predominant formation of at least three dimers with an anionic m/z of 376 as determined by negative-mode electrospray ionization mass spectrometry and the release of ~0.5 mol of nitrite per mol of TNT consumed. The extents of the initial enzymatic reactions were similar in the presence and in the absence of O2, but the dimerization reaction and the release of nitrite were favored under aerobic conditions or under anaerobic conditions in the presence of NADP+. Reactions of chemically and enzymatically synthesized and high-pressure liquid chromatography-purified TNT metabolites showed that both a hydroxylamino-dinitrotoluene isomer and a tautomer of the protonated dihydride-Meisenheimer complex of TNT were required precursors for the dimerization and nitrite release reactions. The m/z 376 dimers also reacted with either dansyl chloride or N-1-naphthylethylenediamine HCl, providing evidence for an aryl amine functional group. In combination, the experimental results are consistent with assigning the chemical structures of the m/z 376 species to various isomers of amino-dimethyl-tetranitrobiphenyl. A mechanism for the formation of these proposed TNT metabolites is presented, and the potential enzymatic and environmental significance of their formation is discussed. 相似文献
996.
997.
A Novel Technique for the Effective Production of Short Peptide Analogs from Concatameric Short Peptide Multimers 总被引:2,自引:0,他引:2
We designed a basic unit of the modified chicken gonadotropin releasing hormone II (cGnRH-II) peptide containing a trypsin cleavable linker peptide at both ends of the original peptide. We made a synthetic DNA coding for the modified cGnRH-II peptide with asymmetric and complementary cohesive ends of linker nucleotides. A tandemly repeated DNA cassette for the expression of concatameric short peptide multimers was constructed by ligating the basic units. The expressed peptide multimers were purified and subject to amino-terminal sequence analysis, which displayed the amino acid sequences expected from the designed nucleotides of the expression cassette. The monomeric cGnRH-II peptide analogs were generated after trypsin digestion. The present results showed that the technique developed for the production of the concatameric peptide multimers with cleavable linker peptides can be generally applicable to the production of short peptide analogs. 相似文献
998.
999.
Young Jun Kang Young Shin Kim Hyangsuk Hur Hee Sun Kim Hyo Jeong Hong 《Biotechnology letters》1999,21(5):375-380
The complete (encoding 55 amino acids, aa) or partial (encoding aa 1–26) preS2 region gene of hepatitis B virus (HBV) was fused to the 3-end of glutathion-S-transferase (GST) gene and expressed under the control of the inducible tac promoter in Escherichia coli at 37 °C. The fusion protein with the complete preS2 region was moderately expressed (8%) while the protein with the N-terminal 26 aa was expressed at a higher level, yielding about 20% of the total cellular proteins. The GST-preS2 (aa 1–26) protein, which contains the immunodominant epitope, was produced form the soluble protein fraction of the recombinant bacteria and purified by affinity chromatography using glutathione-agarose column. The purified preS2 fusion protein showed the antigenicity of preS2, as assessed by indirect and competitive ELISAs. 相似文献
1000.
Cheong Na Eun Choi Yeon Ok Lee Kyun Oh Kim Woe Yeon Jung Bae Gyo Chi Yong Hun Jeong Jin Sook Kim Kanghwa Cho Moo Je Lee Sang Yeol 《Plant molecular biology》1999,40(5):825-834
A cDNA (C2C-Prx) corresponding to a 2Cys-peroxiredoxin (2Cys-Prx) was isolated from a leaf cDNA library of Chinese cabbage. The predicted amino acid sequence of C2C-Prx has 2 conserved cysteines and several peptide domains present in most of the 2Cys-Prx subfamily members. It shows the highest sequence homology to the 2Cys-Prx enzymes of spinach (88%) and Arabidopsis (86%). Southern analysis using the cDNA insert of C2C-Prx revealed that it consists of a small multigene family in Chinese cabbage genome. RNA blot analysis showed that the gene was predominantly expressed in the leaf tissue of Chinese cabbage seedlings, but the mRNA was generally expressed in most tissues of mature plant, except roots. The expression of C2C-Prx was slightly induced by treatment with H2O2 (100M) or Fe3+/O2/DTT oxidation system, but not by ABA (50 M) or GA3 (10 M). The C2C-Prx is encoded as a preprotein of 273 amino acids containing a putative chloroplast-targeting signal of 65 amino acids at its N-terminus. The N-terminally truncated recombinant protein (C2C-Prx) migrates as a dimer in a non-reducing SDS-polyacrylamide gel and as a monomer in a reducing condition. The C2C-Prx shows no immuno cross-reactivity to antiserum of the yeast thiol-specific antioxidant protein, and vice versa. The C2C-Prx prevents the inactivation of glutamine synthetase and the DNA cleavage in the metal-catalyzed oxidation system. In the yeast thioredoxin system containing thioredoxin reductase, thioredoxin, and NADPH, the C2C-Prx exhibits peroxidase activity on H2O2. 相似文献