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1.
Summary
Bacillus thuringiensis var.kurstaki (HD-1)_was grown as a continuous phased culture in a cyclone fermentor. During the time course of the continuous phased cultivation (CPC), the culture was sampled to determine the efficiency of sporulation and parasporal crystal formation. Concurrently, plasmid DNA was extracted and resolved on agarose gels. The plasmid profile remained constant throughout 328 h of cultivation. However, during the same time period, asporogenous, acrystalliferous variants increased from<1% to>90% of the cells harvested. Our data suggests that the disappearance of parasporal crystals inB. thuringiensis var.kurstaki (HD-1) during CPC occurs independent of plasmid copy but may be due to defective sporulation. 相似文献
2.
The pericentriolar material in Chinese hamster ovary cells nucleates microtubule formation 总被引:48,自引:38,他引:10
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The structure and function of the centrosomes from Chinese hamster ovary (CHO) cells were investigated by electron microscopy of negatively stained wholemount preparations of cell lysates. Cells were trypsinized from culture dishes, lysed with Triton X-100, sedimented onto ionized, carbon-coated grids, and negatively stained with phosphotungstate. The centrosomes from both interphase and dividing cells consisted of pairs of centrioles, a fibrous pericentriolar material, and a group of virus-like particles which were characteristic of the CHO cells and which served as markers for the pericentriolar material. Interphase centrosomes anchored up to two dozen microtubules when cells were lysed under conditions which preserved native microtubules. When Colcemid-blocked mitotic cells, initially devoid of microtubules, were allowed to recover for 10 min, microtubules formed at the pericentriolar material, but not at the centrioles. When lysates of Colcemid-blocked cells were incubated in vitro with micotubule protein purified from porcine brain tissue, up to 250 microtubules assembled at the centrosomes, similar to the number of microtubules that would normally form at the centrosome during cell division. A few microtubules could also be assembled in vitro onto the ends of isolated centrioles from which the pericentriolar material had been removed, forming characteristic axoneme- like bundles. In addition, microtubules; were assembled onto fragments of densely staining, fibrous material which was tentatively identified as periocentriolar material by its association of CHO can initiate and anchor microtubules both in vivo and in vitro. 相似文献
3.
G. G. Khachatourians 《Molecular & general genetics : MGG》1981,181(3):411-413
Summary Chromosome replication cycle in a DNA initiation mutant of Escherichia coli (CRT-83, dnaAts) was blocked by nalidixic acid, an inhibitor of the A subunit of DNA gyrase. Following a period of inhibition of DNA synthesis, the drug was removed and run-out DNA synthesis was examined. It was found that the capacity for DNA synthesis was not affected by such a treatment. 相似文献
4.
5.
George G. Khachatourians Court A. Saunders 《Preparative biochemistry & biotechnology》2013,43(3):291-298
A procedure has been developed for preparing minicells that does not rely on sucrose gradients in a rate-zone centrifuge. In the presence of low levels (10 units/ml) of penicillin, the contaminating bacteria present in minicell cultures after low-speed differential centrifugation are turned into long filamentous cells and can be killed by sonic treatment. An additional low-speed centrifugation (2, 000 g for 5 min) yields purified minicells with less than one contaminating cell per 10 minicells. 相似文献
6.
啤酒多倍体酵母菌原生质体已成功地与单倍体原生质体进行融合。经细胞壁再生后,稳定的融合重组体被分离出来。这些融合体的基因分析表明,融合体中含有双亲的基因型。孢子形成良好,且每个子囊中含有四个孢子,每个孢子确实是二倍体。这样原生质体融合就提供了一个对啤酒酿造酵母进行遗传分析的方法。但是如果没有一个方便的杂交技术,这个方法将是很困难的。 相似文献
7.
A disk diffusion type bioassay was developed for T-2 toxin using the yeast Kluyveromyces fragilis. The lower limit of detection for this in 0.2 μg of T-2 toxin. The growth of this yeast was sensitive to other trichothecenes such as verrucarin A (0.01 μg). Aflatoxin B1 (50 μg) and zearalanone (20 μg) did not inhibit the growth of this yeast. 相似文献
8.
Metarhizium anisopliae spores release isoforms of metalloprotease during hydration over a 4-day incubation period. The isoforms were identified and characterized by using one-dimensional native PAGE (1-DE nPAGE) and one-dimensional SDS non-dissociating (1-DE nSDS-PAGE) zymography. The ability of these isozymes to degrade gelatin varied as revealed by 2-D spot densitometry. 1-DE nPAGE zymography revealed five isoforms of gelatinase from Tween wash of conidia. Where as, one to three activities with different intensities appeared on gel from washing of conidia to incubation in water till day 4. The relative migrations of these activities on 1-DE nPAGE zymograms appeared as fast, medium and slow on gel. The 2-D spot densitometry of zymograms indicated isoforms have different proteolytic activity as quantified by pixel intensities. SDS-PAGE zymography indicated the release of two isozymes of Mr 103 and 12 kDa during Tween treatment of conidia. However, during the first washing step with water and incubation of spores at day 2 and 3, respectively, only 12 kDa protein was evident. Majority of these proteases were inhibited by EDTA, but stimulated by CaCl(2), and MgCl(2). The presence of isozymes in conidia and their release during hydration must have functional significance for fungi and in this case it should provide advantages to M. anisopliae in its saprobic or pathogenic modalities. To our knowledge this is the first report describing release of metalloprotease isozymes from conidia. 相似文献
9.
Decreased gene expression from T7 promoters may be due to impaired production of active T7 RNA polymerase 总被引:1,自引:0,他引:1
Background
Protein expression vectors that utilize the bacteriophage T7 polymerase/promoter system are capable of very high levels of protein production. Frequently, however, expression from these vectors does not reliably achieve optimal levels of protein production. Strategies have been proposed previously that successfully maintain high expression levels, however we sought to determine the cause of induction failure. 相似文献10.