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101.
The Arabidopsis AtEPR1 extensin-like gene is specifically expressed in endosperm during seed germination 总被引:5,自引:0,他引:5
Dubreucq B Berger N Vincent E Boisson M Pelletier G Caboche M Lepiniec L 《The Plant journal : for cell and molecular biology》2000,23(5):643-652
Screening of 10 000 Arabidopsis transgenic lines carrying a gene-trap (GUS) construct has been undertaken to identify markers of seed germination. One of these lines showed GUS activity restricted to the endosperm, at the micropylar end of the germinating seed. The genomic DNA flanking the T-DNA insert was cloned by walking PCR and the insertion was shown to be located 70 bp upstream of a 2285 bp open reading frame (AtEPR1) sharing strong similarities with extensins. The AtEPR1 open reading frame consists of 40 proline-rich repeats and is expressed in both wild-type and mutant lines. The expression of the AtEPR1 gene appears to be under positive control of gibberellic acid, but is not downregulated by abscisic acid during seed germination. No expression was detected in organs other than endosperm during seed germination. The putative role of AtEPR1 is discussed in the light of its specific expression in relation to seed germination. 相似文献
102.
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104.
The maternal chromosome set is the target of the T-DNA in the in planta transformation of Arabidopsis thaliana 总被引:8,自引:0,他引:8
In planta transformation methods are now commonly used to transform Arabidopsis thaliana by Agrobacterium tumefaciens. The origin of transformants obtained by these methods has been studied by inoculating different floral stages and examining gametophytic expression of an introduced beta-glucuronidase marker gene encoding GUS. We observed that transformation can still occur after treating flowers where embryo sacs have reached the stage of the third division. No GUS expression was observed in embryo sacs or pollen of plants infiltrated with an Agrobacterium strain bearing a GUS gene under the control of a gametophyte-specific promoter. To identify the genetic target we used an insertion mutant in which a gene essential for male gametophytic development has been disrupted by a T-DNA bearing a Basta resistance gene (B(R)). In this mutant the B(R) marker is transferred to the progeny only by the female gametes. This mutant was retransformed with a hygromycin resistance marker and doubly resistant plants were selected. The study of 193 progeny of these transformants revealed 25 plants in which the two resistance markers were linked in coupling and only one plant where they were linked in repulsion. These results point to the chromosome set of the female gametophyte as the main target for the T-DNA. 相似文献
105.
Specific Single or Double Proline Substitutions in the “Spring-loaded” Coiled-Coil Region of the Influenza Hemagglutinin Impair or Abolish Membrane Fusion Activity 下载免费PDF全文
Hui Qiao Sandra L. Pelletier Lucas Hoffman Jill Hacker R. Todd Armstrong Judith M. White 《The Journal of cell biology》1998,141(6):1335-1347
We tested the role of the “spring-loaded” conformational change in the fusion mechanism of the influenza hemagglutinin (HA) by assessing the effects of 10 point mutants in the region of high coiled-coil propensity, HA2 54–81. The mutants included proline substitutions at HA2 55, 71, and 80, as well as a double proline substitution at residues 55 and 71. Mutants were expressed in COS or 293T cells and assayed for cell surface expression and structural features as well as for their ability to change conformation and induce fusion at low pH. We found the following: Specific mutations affected the precise carbohydrate structure and folding of the HA trimer. All of the mutants, however, formed trimers that could be expressed at the cell surface in a form that could be proteolytically cleaved from the precursor, HA0, to the fusion-permissive form, HA1-S-S-HA2. All mutants reacted with an antibody against the major antigenic site and bound red blood cells. Seven out of ten mutants displayed a wild-type (wt) or moderately elevated pH dependence for the conformational change. V55P displayed a substantial reduction (~60– 80%) in the initial rate of lipid mixing. The other single mutants displayed efficient fusion with the same pH dependence as wt-HA. The double proline mutant V55P/ S71P displayed no fusion activity despite being well expressed at the cell surface as a proteolytically cleaved trimer that could bind red blood cells and change conformation at low pH. The impairment in fusion for both V55P and V55P/S71P was at the level of outer leaflet lipid mixing. We interpret our results in support of the hypothesis that the spring-loaded conformational change is required for fusion. An alternate model is discussed. 相似文献
106.
S. Bonhomme C. Horlow D. Vezon S. de Laissardière A. Guyon M. Férault M. Marchand N. Bechtold G. Pelletier 《Molecular genetics and genomics : MGG》1998,260(5):444-452
Many genes are thought to be expressed during the haploid phase in plants, however, very few haploid-specific genes have been isolated so far. T-DNA insertion mutagenesis is a powerful tool for generating mutations that affect gametophyte viability and function, as disruption of a gene essential for these processes should lead to a defect in the transmission of the gametes. Mutants can therefore be screened on the basis of segregation distortion for a reporter resistance gene contained in the T-DNA. We have screened the Versailles collection of Arabidopsis transformants for 1:1 KanR:KanS segregation after selfing, focussing on gametophyte mutations which show normal transmission through one gametophyte and cause lethality or dysfunction of the other. Only 1.3% (207) of the 16,000 lines screened were scored as good candidates. Thorough genetic analysis of 38 putative T-DNA transmission defect lines (Ttd) identified 8 defective gametophyte mutants, which all showed 0 to 1% T-DNA transmission through the pollen. During the screen, we observed a high background of low-penetrance mutations, often affecting the function of both gametophytes, and many lines which were likely to carry chromosomal rearrangements. The reasons for the small number of retained lines (all male gametophytic) are discussed, as well as the finding that, for most of them, residual T-DNA transmission is obtained through the affected gametophyte. 相似文献
107.
A parametric study of the destruction efficiency of Bacillus spores in low pressure oxygen-based plasmas 总被引:2,自引:2,他引:0
The destruction of Bacillus spores in oxygen-based plasmas sustained in the millitorr pressure range has been studied as functions of various biological and plasma parameters, namely Bacillus species, surface concentration of spores, treatment temperature, and gas composition. In an oxygen plasma, Bacillus stearothermophilus appears less plasma-resistant than the other spores tested. Oxygen, H2 O2 and chiefly CO2 plasmas are clearly shown to be much more efficient in destroying Bacillus subtilis spores than pure argon plasma. The bacterial surface concentration on the spore carriers and the treatment temperature also lead to significant variations in the destruction efficiency of spores when using CO2 plasma. 相似文献
108.
Hans M.H. van Eijk Johanne G. Bloemen Cornelis H.C. Dejong 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》2009,877(8-9):719-724
A new liquid chromatography–mass spectrometry method is described to determine concentrations of the short chain fatty acids acetic acid, propionic acid and butyric acid (SCFAs) in human blood plasma. The method is based on reversed phase chromatography followed by post-column neutralization of the mobile phase with ammonia and a consecutive measurement of the SCFAs ammonia adducts using negative electro spray ionization. Sample preparation involved simple organic acid deproteinization, resulting in 100% recovery. SCFAs eluted baseline separated within a 25 min run cycle. A linear response was obtained in the range between 0 and 250 μmol/l (R2 ranged from 0.997 to 0.9999). The limit of detection ranged from 0.05 μmol/l for propionic and butyric acid and 0.1 μmol/l for acetic acid. The method was tested by analyzing plasma of arterial blood, from portal vein and hepatic vein blood from patients undergoing a pylorus-preserving pancreaticoduodenectomy. As expected, the highest SCFA concentrations were found in portal plasma, hepatic vein levels were in between, while arterial concentrations were lowest. This newly developed method is suitable to determine SCFA concentrations in human plasma samples. 相似文献
109.
Anja Irmisch Eleni Ampatzidou Ken'ichi Mizuno Matthew J O'Connell Johanne M Murray 《The EMBO journal》2009,28(2):144-155
The Smc5/6 structural maintenance of chromosomes complex is required for efficient homologous recombination (HR). Defects in Smc5/6 result in chromosome mis‐segregation and fragmentation. By characterising two Schizosaccharomyces pombe smc6 mutants, we define two separate functions for Smc5/6 in HR. The first represents the previously described defect in processing recombination‐dependent DNA intermediates when replication forks collapse, which leads to increased rDNA recombination. The second novel function defines Smc5/6 as a positive regulator of recombination in the rDNA and correlates mechanistically with a requirement to load RPA and Rad52 onto chromatin genome‐wide when replication forks are stably stalled by nucleotide depletion. Rad52 is required for all HR repair, but Rad52 loading in response to replication fork stalling is unexpected and does not correlate with damage‐induced foci. We propose that Smc5/6 is required to maintain stalled forks in a stable recombination‐competent conformation primed for replication restart. 相似文献
110.
Brigitte Michelsen Ragnhild Fiane Andreas P. Diamantopoulos Dag Magnar Soldal Inger Johanne W. Hansen Tuulikki Sokka Arthur Kavanaugh Glenn Haugeberg 《PloS one》2015,10(4)