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排序方式: 共有262条查询结果,搜索用时 15 毫秒
1.
T Fukamizo T Ohkawa K Sonoda H Toyoda T Nishiguchi S Ouchi S Goto 《Bioscience, biotechnology, and biochemistry》1992,56(10):1632-1636
The cell wall of Fusarium oxysporum f. sp. lycopersici was digested with chitinase to analyze the structure of its chitinous components. In spite of a similar acetylation degree of the cell wall components to that of 25-35% acetylated chitosan, only N-acetylglucosamine disaccharide [(GlcNAc)2] was obtained from chitinase hydrolyzate of the fungal cell wall by CM-Sephadex C-25 column chromatography, while (GlcNAc)2 and several types of deacetylated chitooligosaccharides were separated from that of 25-35% acetylated chitosan. The results indicate that N-acetylglucosamine residues in the polysaccharide chains of the fungal cell wall are most likely condensed into some region, while acetylated residues are more scattered in 25-35% acetylated chitosan. 相似文献
2.
Cross-linked poly(N-benzyl-4-vinylpyridinium halide) (designated insoluble BVP) was previously reported to capture bacterial cells alive by contact with them. The corresponding linear polymer poly(N-benzyl-4-vinylpyridinium salt) (designated soluble BVP) was found to exhibit antibacterial activity. This soluble pyridinium-type polymer showed strong antibacterial activity against gram-positive bacteria, whereas it was less active against gram-negative bacteria. The antibacterial activity of this cationic, polymeric disinfectant was considerably greater than that of the corresponding monomeric compound and was approximately equal to that of conventional disinfectants such as benzalkonium chloride and chlorohexidine. 相似文献
3.
Circadian variations in the activities of aldehyde dehydrogenase (ALDH) isozymes in the subcellular fractions of the brain and liver were investigated in male and female mice of C57BL/6J strain. The rhythms in high Km-ALDH activities of brain and liver mitochondrial fractions which existed in ordinary light-dark cycle were not observed in animals maintained in the continuous darkness for two weeks. The rhythms in high Km-ALDH activities of hepatic soluble and microsomal fractions existed in both ordinary cycle and total darkness but the rhythmic phases were different. In the low Km-ALDH activity of hepatic mitochondrial fraction, the circadian rhythm was similar in two lighting conditions. There was sex difference in the existence of the circadian rhythm. It seems that the ALDH activity of mice is influenced by light-dark cycle and sex hormones. 相似文献
4.
Isolation and characterization of a large,neurite-associated glycoconjugate from neuroblastoma cells
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A high molecular weight glycoconjugate has been isolated from neurite-producing neuronal tumor cells in culture and has been designated as I(0) based on its elution characteristics in gel filtration chromatography. This molecule cannot be found in a variety of nonneuronal cells. I(0) is found in the substratum-attached material or cell fraction of neurite-producing neuroblastoma cells, depending upon culture conditions. It is found in the substratum-bound fraction of B104 rat neuroblastoma cells during serum starvation and in the EGTA-detached cell fraction of B104 cells grown in chemically defined N2 medium. It occurs only in the cell fraction of the human neuroblastoma line Platt. Examination of behavioral variants of the B104 rat line further strengthens the association of I(0) with neurite production; the constitutive neurite-producing E(R)B9 variant contains I(0) while the non-neurite-producing E(R)A11 variant does not. I(0) is large, eluting in the void volume of sepharose-CL2B columns. Radioiodination of intact cells with lactoperoxidase shows I(0) to be a cell surface component. Metabolic radiolabeling studies show that it contains a high proportion of polysaccharide to protein, does not contain mannose, and is unsulfated. Alkaline borohydride reduction release two size classes of large polysaccharide chain. The alkaline reduction results, along with the mannose incorporation studies, show the presence of O-glycosidic linkages and few, if any, N-linkages. Resistance to nitrous acid deamination, insensitivity to glycosaminoglycan lyases, and the absence of sulfation, indicate that I(0) does not contain the glycosaminoglycans hyaluronic acid, chondroitin-, dermatan-, or heparin- sulfates. Affinity column chromatography reveals high binding affinity of I(0) to polyornithine and no binding to gelatin (collagen) or the glycosaminoglycans hyaluronate and heparin. These studies describe a unique high molecular weight glycoconjugate on the surface of neurite-producing neuroblastoma cell lines from two species. 相似文献
5.
Relative apparent synapomorphy analysis (RASA). I: The statistical measurement of phylogenetic signal 总被引:10,自引:9,他引:1
We have developed a new approach to the measurement of phylogenetic signal
in character state matrices called relative apparent synapomorphy analysis
(RASA). RASA provides a deterministic, statistical measure of natural
cladistic hierarchy (phylogenetic signal) in character state matrices. The
method works by determining whether a measure of the rate of increase of
cladistic similarity among pairs of taxa as a function of phenetic
similarity is greater than a null equiprobable rate of increase. Our
investigation of the utility and limitations of RASA using simulated and
bacteriophage T7 data sets indicates that the method has numerous
advantages over existing measures of signal. A first advantage is
computational efficiency. A second advantage is that RASA employs known
methods of statistical inference, providing measurable sensitivity and
power. The performance of RASA is examined under various conditions of
branching evolution as the number of characters, character states per
character, and mutations per branch length are varied. RASA appears to
provide an unbiased and reliable measure of phylogenetic signal, and the
general approach promises to be useful in the development of new techniques
that should increase the rigor and reliability of phylogenetic estimates.
相似文献
6.
Cloning and characterization of a Bacillus subtilis gene encoding a homolog of the 54-kilodalton subunit of mammalian signal recognition particle and Escherichia coli Ffh. 总被引:8,自引:2,他引:6
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By using a DNA fragment of Escherichia coli ffh as a probe, the Bacillus subtilis ffh gene was cloned. The complete nucleotide sequence of the cloned DNA revealed that it contained three open reading frames (ORFs). Their order in the region, given by the gene product, was suggested to be ORF1-Ffh-S16, according to their similarity to the gene products of E. coli, although ORF1 exhibited no significant identity with any other known proteins. The orf1 and ffh genes are organized into an operon. Genetic mapping of the ffh locus showed that the B. subtilis ffh gene is located near the pyr locus on the chromosome. The gene product of B. subtilis ffh shared 53.9 and 32.6% amino acid identity with E. coli Ffh and the canine 54-kDa subunit of signal recognition particle, respectively. Although there was low amino acid identity with the 54-kDa subunit of mammalian signal recognition particle, three GTP-binding motifs in the NH2-terminal half and amphipathic helical cores in the COOH-terminus were conserved. The depletion of ffh in B. subtilis led to growth arrest and drastic morphological changes. Furthermore, the translocation of beta-lactamase and alpha-amylase under the depleted condition was also defective. 相似文献
7.
Molecular evolution of voltage-sensitive ion channel genes: on the origins of electrical excitability 总被引:14,自引:0,他引:14
We have analyzed nucleic acid and amino acid sequence alignments of a
variety of voltage-sensitive ion channels, using several methods for
phylogenetic tree reconstruction. Ancient duplications within this family
gave rise to three distantly related groups, one consisting of the Na+ and
Ca++ channels, another the K+ channels, and a third including the cyclic
nucleotide-binding channels. A series of gene duplications produced at
least seven mammalian homologues of the Drosophila Shaker K+ channel;
clones of only three of these genes are available from all three mammalian
species examined (mouse, rat, and human), pointing to specific genes that
have yet to be recovered in one or another of these species. The
Shaw-related K+ channels and the Na+ channel family have also undergone
considerable expansion in mammals, relative to flies. These expansions
presumably reflect the needs of the high degree of physiological and
neuronal complexity of mammals. Analysis of the separate domains of the
four-domain channels (Ca++ and Na+) supports their having evolved by two
sequential gene duplications and implies the historical existence of a
functional two-domain channel.
相似文献
8.
mtDNA diversity in rhesus monkeys reveals overestimates of divergence time and paraphyly with neighboring species 总被引:4,自引:0,他引:4
Reconstructions of the human-African great ape phylogeny by using
mitochondrial DNA (mtDNA) have been subject to considerable debate. One
confounding factor may be the lack of data on intraspecific variation. To
test this hypothesis, we examined the effect of intraspecific mtDNA
diversity on the phylogenetic reconstruction of another Plio- Pleistocene
radiation of higher primates, the fascicularis group of macaque (Macaca)
monkey species. Fifteen endonucleases were used to identify 10 haplotypes
of 40-47 restriction sites in M. mulatta, which were compared with similar
data for the other members of this species group. Interpopulational,
intraspecific mtDNA diversity was large (0.5%- 4.5%), and estimates of
divergence time and branching order incorporating this variation were
substantially different from those based on single representatives of each
species. We conclude that intraspecific mtDNA diversity is substantial in
at least some primate species. Consequently, without prior information on
the extent of genetic diversity within a particular species, intraspecific
variation must be assessed and accounted for when reconstructing primate
phylogenies. Further, we question the reliability of hominoid mtDNA
phylogenies, based as they are on one or a few representatives of each
species, in an already depauperate superfamily of primates.
相似文献
9.
An attenuated strain L11A of tobacco mosaic virus (TMV) multiplied like wild type strain L at an early stage of infection in tomato leaves. Four days after inoculation, however, multiplication of L11A was drastically reduced (autoregulation) compared with the constant multiplication of L. In mixed infections, L11A strongly inhibited the multiplication of homologous strain L. Experiments with cucumber mosaic virus (CMV) or tobacco plants revealed that the inhibitory mechanism of L11A is not host-specific but virus-specific, and the autoregulatory mechanism is effective only for TMV. RNA synthesis in L11A infected leaves 4 days after inoculation was studied by polyacrylamide gel electrophoresis. Synthesis of TMV-RNA and its replicative intermediate were strongly inhibited, whereas the replicative form of TMV-RNA and ribosomal RNA were synthesized as in the case of L infection. Synthesis of non-coat-protein was studied by the incorporation of radioactive histidine into subcellular fractions derived from leaves infected with L or L11A for 4 days. Different patterns of the two strains in protein synthesis were noted. At least three proteins were predominantly synthesized in L11A infection. One of them was observed in the mitochondria fraction. From its position in polyacrylamide gel, it could be viral coded 165K protein which is considered to be involved in viral RNA replication. These results suggest that the unique nature of attenuated virus L11A, i.e. autoregulation, resulted from the inhibitory mechanism of viral RNA synthesis due to overproduction of 165K protein and is quite distinct from interferon, intrinsic interference or interference by defective virus. 相似文献
10.
Enzyme immunoassay for serum dexamethasone using 4-(carboxymethylthio)dexamethasone as a new hapten.
A sensitive and simple enzyme immunoassay for direct quantitation of serum dexamethasone was established. An antiserum with high specificity was produced by the immunization of rabbits with a newly synthesized 4-(carboxymethylthio)dexamethasone-bovine serum albumin conjugate. Alkaline phosphatase was used as a labeling enzyme. The minimum amount of dexamethasone detected was 2 pg per tube on the basis of B/Bo 100 - 2 SD (%) of standard curve. However, taking into account the cross-reaction with steroids such as cortisol in dexamethasone-free serum, the measurable range was from approximately 0.13 to 10 micrograms/dl. Intra- and interassay coefficients of variation were 1.5 - 5.4% and 0.6 - 6.5%, respectively. Serum levels of dexamethasone and cortisol in four normal subjects after an oral administration of 1 mg of dexamethasone are also reported. 相似文献