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991.
Expression of the human proenkephalin gene in mouse pituitary cells: accurate and efficient mRNA production and proteolytic processing 总被引:8,自引:0,他引:8 下载免费PDF全文
A recombinant plasmid containing the human proenkephalin gene ligated to pBR322 was introduced into a mouse pituitary cell line (AtT-20D16v) that normally expresses pro-opiomelanocortin but not proenkephalin. The plasmid was introduced by co-transformation with the G418-selectable plasmid, pRSVneo. Stable transformants were isolated and analyzed for the presence of the human proenkephalin gene. AtT-20 transformants which had one or more copies of the human proenkephalin gene integrated stably into the mouse chromosomal DNA expressed a 1.45 kb mRNA identical in size to human proenkephalin mRNA. Primer extension analysis indicated that the human proenkephalin gene was accurately and efficiently transcribed from its own promoter. AtT-20 transformants that expressed the 1.45 kb human proenkephalin mRNA also expressed proenkephalin protein and cleaved the protein to form free Met-enkephalin. This is of particular interest because these cells do not cleave all of the available pairs of basic amino acids in the endogenous protein, pro-opiomelanocortin, the precursor to ACTH, beta-endorphin and melanocyte stimulating hormones. The release of both ACTH and Met-enkephalin from these cells is stimulated by corticotropin releasing factor, a natural secretagogue for ACTH, indicating that the two classes of peptide share a related secretory pathway. 相似文献
992.
Luminol-dependent luminescence (LDL) and luminol-independent, native luminescence (NL) of polymorphonuclear leukocytes were investigated with respect to the effects generated by the addition of albumin to the reaction medium. The cells were activated: (1) by simple surface attachment to a hydrophilic plastic, (2) by opsonized zymosan, (3) by phorbol myristate acetate, (4) by formylmethionyl-leucyl-phenylalaline. Both kinds of emissions were recorded simultaneously using a method of spectral discrimination. The addition of albumin resulted in an inhibition of LDL, which coincided with a generation of NL. The extent of the inhibition of LDL depended on the type of stimulus used. Maximum inhibition occurred with cells activated by attachment to plastic surfaces and minimum inhibition was observed with cells stimulated by opsonized zymosan. Different contributions of extracellularly released reactive oxygen-species may be responsible for this. It appears possible to discriminate between intra- and extracellular sites of oxygen-metabolites production using albumin simultaneously as extracellular quencher of LDL and as luminescent probe for NL. 相似文献
993.
Jürgen Siekmann Herbert R. Wenzel Eduard Matuszak Eberhard von Goldammer Harald Tschesche 《The protein journal》1988,7(5):633-640
ThepH dependence of the equilibrium constant KHyd for the hydrolysis of the Lys15-Ala16 reactive-site peptide bond of the bovine pancreatic trypsin inhibitor (aprotinin) was investigated over thepH range 2.3–6.5. Solutions of aprotinin, modified aprotinin with the Lys15-Ala16 peptide bond cleaved and mixtures of both species were incubated with 10 mol% porcine β-trypsin. The state of equilibrium was determined by analytical cation-exchange HPLC. The KHyd values obtained did not exactly obey the simple equation of Dobry et al. (1952), which had to be used in an extended form with two additional parameters for a satisfactory fit. ThepH-independent equilibrium constant is 0.90 and thepK values of the Lys15 carboxyl group and of the Ala16 amino group are 3.10 and 8.22, respectively. ThepK of an additional group is apparently perturbed by the peptide-bond hydrolysis. It is 4.60 in the native and 4.40 in the modified aprotinin. 相似文献
994.
Patricia M. Shaffer Herbert N. Arst Jr. Leah Estberg Leon Fernando Tran Ly Mark Sitter 《Molecular & general genetics : MGG》1988,212(2):337-341
Summary Of five amidohydrolase activities subject to nitrogen metabolite repression in Aspergillus nidulans, l-asparaginase shows clearest evidence of also being subject to repression by atmospheric oxygen. Such oxygen repressibility is only evident under nitrogen metabolite derepressed conditions. Asparaginase levels are also considerably elevated by areA300, an altered function allele of the positive acting wide domain regulatory gene areA mediating nitrogen metabolite repression and are drastically reduced by loss of function mutations in areA. A. nidulans has two l-asparaginase enzymes and it has been shown by the use of appropriate mutants that these regulatory effects are exerted on the expression of that specified by the ahrA gene but probably not that specified by the apnA gene.
Present address: (until 25 August, 1988) Department of Genetics, University of Georgia, Athens, GA 30602, USA 相似文献
995.
Christopher J. Herbert Geneviève Dujardin Michel Labouesse Piotr P. Slonimski 《Molecular & general genetics : MGG》1988,213(2-3):297-309
Summary We studied the NAM2 genes of Saccharomyces douglasii and Saccharomyces cerevisiae, and showed that they are interchangeable for all the known functions of these genes, both mitochondrial protein synthesis and mitochondrial mRNA splicing. This confirms the prediction that the S. douglasii NAM2D gene encodes the mitochondrial leucyl tRNA synthetase (EC 6.1.1.4). The observation that these enzymes are interchangeable for their mRNA splicing functions, even though there are significant differences in the intron/exon structure of their mitochondrial genome, suggests that they may have a general role in yeast mitochondrial RNA splicing. A short open reading frame (ORF) precedes the synthetase-encoding ORF, and we showed that at least in S. cerevisiae this is not essential for the expression of the gene; however, it may be involved in a more subtle type of regulation. Sequence comparisons of S. douglasii and S. cerevisiae revealed a particularly interesting situation from the evolutionary point of view. It appears that the two yeasts have diverged relatively recently: there is remarkable nucleotide sequence conservation, with no deletions or insertions, but numerous (albeit non-saturating) silent substitutions resulting from transitions. This applies not only to the NAM2 coding regions, but also to two other ORFs flanking the NAM2 ORF. The regions between the ORFs (believed to be intergenic regions) are much less conserved, with several deletions and insertions. Thus S. douglasii and S. cerevisiae provide an ideal system for the study of molecular evolution, being two yeasts caught in the act of speciation. 相似文献
996.
A linkage map of mouse Chromosome 1 using an interspecific cross segregating for the gld autoimmunity mutation 总被引:6,自引:0,他引:6
Mark L. Watson Peter D'Eustachio Beverly A. Mock Alfred D. Steinberg Herbert C. Morse III Rebecca J. Oakey Thad A. Howard Julie M. Rochelle Michael F. Seldin 《Mammalian genome》1992,2(3):158-171
An interspecific backross was used to define a high resolution linkage map of mouse Chromosome (Chr) 1 and to analyze the segregation of the generalized lymphoproliferative disease (gld) mutation. Mice homozygous for gld have multiple features of autoimmune disease. Analysis of up to 428 progeny from the backcross [(C3H/HeJ-gld x Mus spretus)F1 x C3H/HeJ-gld] established a map that spans 77.6 cM and includes 56 markers distributed over 34 ordered genetic loci. The gld mutation was mapped to a less than 1 cM segment on distal mouse Chr 1 using 357 gld phenotype-positive backcross mice. A second backcross, between the laboratory strains C57BL/6J and SWR/J, was examined to compare recombination frequency between selected markers on mouse Chr 1. Significant differences in crossover frequency were demonstrated between the interspecific backcross and the inbred laboratory cross for the entire interval studied. Sex difference in meiotic crossover frequency was also significant in the laboratory mouse cross. Two linkage groups known to be conserved between segments of mouse Chr 1 and the long arm of human Chrs 1 and 2 where further defined and a new conserved linkage group was identified that includes markers of distal mouse Chr 1 and human Chr 1, bands q32 to q42. 相似文献
997.
998.
Herbert L. Holland Sankarlal Poddar Brian Tripet 《Journal of industrial microbiology & biotechnology》1992,10(3-4):195-197
Summary The effects of calcium alginate bead immobilization and the presence of organic solvents on two bioconversion reactions carried out byMortierella isabellina ATCC 42613 have been investigated. These reactions, the 14-hydroxylation of progesterone and the sulfoxidation of thioanisole, both proceed in high yield using resting-cell bioconversions, but are not carried out by alginate bead preparations in the absence of an organic co-solvent, the best results being obtained with 5 or 10% aqueous methanol. The stereoselectivity of sulfoxidation, of thioanisole was found to be dependent upon the nature and concentration of organic co-solvent. 相似文献
999.
The use of compound continuous flow diffusion chemostats to study the interaction between nitrifying and nitrate-reducing bacteria 总被引:1,自引:0,他引:1
Abstract The interactions occuring between populations of a nitrate-respiring Vibrio sp. and autotrophic nitrifying bacteria belonging to the genera Nitrosomonas and Nitrobacter have been investigated in a compound bi-directional flow diffusion chemostat at a dilution rate of 0.025 h−1 and a temperature of 25°C. When grown under NO− 3 limitation, the Vibrio sp. produced NH+ 4 as the principal end-product of nitrate respiration, and there was a corresponding significant increase in cell numbers of the Nitrosomonas sp. population, which derived energy by the oxidation of NH+ 4 to NO− 2 . Nitrite in turn was used by the Nitrobacter sp. population as an energy source with the concomitant regeneration of NO− 3 . Under NO− 3 excess growth conditions the Vibrio sp. produced NO− 2 rather than NH+ 4 as the major product of NO− 3 dissimilation, and growth of the Nitrobacter population was stimulated as increased quantities of NO− 2 became available. In contrast, the Nitrosomonas sp. population declined sharply as the energy source NH+ 4 became limiting. These data demonstrate that defined mixed populations of obligately aerobic nitrifying bacteria and facultatively anaerobic nitrate respiring bacteria can co-exist for extended time periods and operate an internal nitrogen cycle which is energetically beneficial to both populations. 相似文献
1000.
Summary Phenotyping for Gc variants by conventional electrophoresis in 835 Papio hamadryas baboons demonstrated a monomorphic population. Gc subtyping by polyacrylamide IEF gels, pH 4–6, on 394 of these baboons revealed the existence of two common alleles which we named Gc
Papio
1
and Gc
Papio
2
. Pedigree data confirmed the inheritance of a single locus, two allele system and the observed gene frequencies were 0.593 for Gc
Papio
1
and 0.407 for Gc
Papio
2
. 相似文献