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61.
The yeasts Candida utilis and Hansenula polymorpha were able to grow in media containing choline or ethanolamine as the sole nitrogen source. During growth in the presence of these substrates, large peroxisomes developed in the cells, and extracts of choline-grown C. utilis cells contained increased levels of amine oxidase and catalase. Incubation of whole cells with choline in the presence of the amine oxidase inhibitor aminoacetonitrile led to excretion of dimethylamine and methylamine. Cytochemical experiments in which spheroplasts prepared from choline-grown cells were incubated with CeCl3 and choline, trimethylamine, dimethylamine or methylamine revealed positively stained peroxisomes, whereas in the presence of 1 mM aminoacetonitrile staining was not observed. This indicated that choline was degraded via methylated amines and that peroxisomes played a role in its metabolism. A similar involvement of peroxisomes in choline degradation was observed in H. polymorpha. Cell-free extracts of ethanolamine-grown C. utilis and H. polymorpha also contained increased levels of amine oxidase and catalase. Ethanolamine was oxidized by cell-free extracts of both organisms after growth in the presence of ethanolamine or choline. Incubation of spheroplasts of ethanolamine-or choline-grown C. utilis with CeCl3 and ethanolamine resulted in positively stained peroxisomes. In this organism peroxisomes were therefore also involved in ethanolamine degradation.K. B. Zwart was supported by the Foundation for Fundamental Biological Research (BION) which is subsidized by the Netherlands Organization for the Advancement of Pure Research (ZWO). 相似文献
62.
Dick De Zwart 《Aquatic Ecology》1979,13(2-3):96-96
Summary Three-stage aquatic microcosms have been employed to investigate the long-term effects of subtle temperature rises. The type of microcosm used consists of three seperate aquaria, each representing one of the following trophic levels: autotrophs, herbivores and decomposers. The subsystems are interconnected by a pump-driven circulation flow. During a two-year experiment four of these systems have been subjected to a sequence of temperatures. Assuming the winter situation to be the most critical period regarding thermal pollution, the temperatures varied between 5°C and 17°C. Each temperature has been sustained for a period of at least 100 days, to ensure the development of ecological relevant steady-states. The parameters observed, such as oxygen, phosphate and nitrate concentration, particle volume and zooplankton biomass, show a totally reversible effect to temperature in those cases that any effect is detectable. The systems show little memory in reacting to temperature alterations.It can be concluded tentatively from part of all data that temperature rises of up to 8°C have no harmfull effects. Increasing the temperature to the absolute value of 17°C effected the phosphate metabolism of the micro-ecosystems.A more extensive report, containing the fully analysed data and some remarks on the utility of microcosms in ecological impact studies, will be available on request from November 1979. 相似文献
63.
Growth of Hansenula polymorpha in shake flasks and chemostat cultures in the presence of methanol as the sole source of carbon and methylamine as the sole
source of nitrogen was associated with the development of peroxisomes in the cells. The organelles were involved in the concurrent
oxidation of these two compounds, since they contained both alcohol oxidase and amine oxidase, which are key enzymes in methanol
and methylamine metabolism, respectively. In addition catalase was present. Peroxisomes with a completely crystalline substructure
were observed in methanol-limited chemostat-grown cells. Amine oxidase probably formed an integral part of these crystalloids,
whereas catalase was present in a freely diffusable form.
Transfer of cells, grown in a methanol-limited chemostat in the presence of methylamine into glucose/ammonium sulphate media
resulted in the loss of both alcohol oxidase and amine oxidase activity from the cells. This process was associated with degradation
of the crystalline peroxisomes. However, when cells were transferred into glucose/methylamine media, amine oxidase activity
only declined during 2 h after the transfer and thereafter increased again. This subsequent rise in amine oxidase activity
was associated with the development of new peroxisomes in the cells in which degradation of the crystalline peroxisomes, originally
present, continued. These newly formed organelles probably originated from peroxisomes which had not been affected by degradation.
When in the methanollimited chemostat methylamine was replaced by ammonium sulphate, repression of the synthesis of amine
oxidase was observed. However, inactivation of this enzyme or degradation of peroxisomes was not detected. The decrease of
amine oxidase activity in the culture was accounted for by dilution of enzyme as a result of growth and washout. 相似文献
64.
65.
Sai-Mei Hou Fred J. Van Dam Frans de Zwart Caroline Warnock Maddalena Mognato Joanne Turner Natalia Podlutskaja Andrej Podlutsky Roswitha Becker Yvonne Barnett Christopher R. Barnett Lucia Celotti Margaret Davies Edith Hüttner Bo Lambert A. D. Tates 《Mutation research》1999,431(2):21
The T-cell cloning assay, which enables the enumeration and molecular analysis of 6-thioguanine resistant (HPRT-negative) mutant T-cells, has been extensively used for studying human somatic gene mutation in vivo. However, large inter-laboratory variations in the HPRT mutant frequency (MF) call for further investigation of inter-laboratory differences in the experimental methodology, and development of an optimal but easy uniform cloning protocol. As part of the EU Concerted Action on HPRT Mutation (EUCAHM), we have carried out two Ring tests for the T-cell cloning assay. For each test, duplicate and coded samples from three buffy coats were distributed to five laboratories for determination of MF using six different protocols. The results indicated a good agreement between split samples within each laboratory. However, both the cloning efficiencies (CEs) and MFs measured for the same blood donors showed substantial inter-laboratory variations. Also, different medium compositions used in one and the same laboratory resulted in a remarkable difference in the level of MF. A uniform operating protocol (UOP) was proposed and compared with the traditional protocols in the second Ring test. The UOP (preincubation) increased the CE in laboratories traditionally using preincubation, but decreased the CE in laboratories traditionally using priming. Adjusted for donor, use of different protocols contributed significantly to the overall variation in lnCE (P=0.0004) and lnMF (P=0.03), but there was no significant laboratory effect on the lnCE (P=0.38) or lnMF (P=0.14) produced by the UOP alone. Finally, a simplified version of the UOP using the serum-free medium X-Vivo 10 and PMA was tested in one laboratory, and found to produce a considerable increase in CE. This modified UOP needs to be further evaluated in order to be used for future databases on HPRT MFs in various populations. 相似文献
66.
A simple remedy against artifactual double bands in denaturing gradient gel electrophoresis 总被引:8,自引:0,他引:8
Denaturant gradient gel electrophoresis (DGGE) is a widely used method for mutation analysis and for studies of microbial diversity. Particular combinations of target gene fragments and primers may give rise to erroneous DGGE profiles. We report on a very straightforward means to eliminate the artifactual 'double bands' that can be encountered in several applications. 相似文献
67.
68.
Zwart G Kamst-van Agterveld MP van der Werff-Staverman I Hagen F Hoogveld HL Gons HJ 《Environmental microbiology》2005,7(3):365-377
We have studied the diversity of pelagic cyanobacteria in Lake Loosdrecht, The Netherlands, through recovery and analysis of small subunit ribosomal RNA gene sequences from lake samples and cyanobacterial isolates. We used an adapted protocol for specific amplification of cyanobacterial rDNA for denaturing gradient gel electrophoresis (DGGE) analysis. This protocol enabled direct comparison of cyanobacterial community profiles with overall bacterial profiles. The theoretical amplification specificity of the primers was supported by sequence analysis of DNA from excised DGGE bands. Sequences recovered from these bands, in addition to sequences obtained by polymerase chain reaction (PCR) and cloning from lake DNA as well as from cyanobacterial isolates from the lake, revealed a diverse consortium of cyanobacteria, among which are representatives of the genera Aphanizomenon, Planktothrix, Microcystis and Synechococcus. One numerically important and persistent cyanobacterium in the lake, Prochlorothrix hollandica, appeared to co-occur with an unknown but related species. However, the lake is dominated by filamentous species that originally have been termed 'Oscillatoria limnetica-like'. We show that this is a group of several related cyanobacteria, co-occurring in the lake, which belong to the Limnothrix/Pseudanabaena group. The available variation among the coexisting strains of this group can explain the persistent dominance of the group under severe viral pressure. 相似文献
69.
E. A. Hart K. Zwart A. J. Teske M. Voskuil P. R. Stella S. A. J. Chamuleau A. O. Kraaijeveld 《Netherlands heart journal》2017,25(2):137-142
Percutaneous MitraClip placement for treatment of severe mitral regurgitation in high surgical risk patients is a commonly performed procedure and requires a transseptal puncture to reach the left atrium. The resulting iatrogenic atrial septal defect (iASD) is not routinely closed, yet the haemodynamic and functional consequences of a persisting defect are not fully understood. Despite positive effects such as acute left atrial pressure relief, persisting iASDs are associated with negative consequences, namely significant bidirectional shunting and subsequent worse clinical outcome. Percutaneous closure of the iASD may therefore be desirable in selected cases. In this review we discuss the available literature on this matter. 相似文献
70.
Adams PD Afonine PV Bunkóczi G Chen VB Echols N Headd JJ Hung LW Jain S Kapral GJ Grosse Kunstleve RW McCoy AJ Moriarty NW Oeffner RD Read RJ Richardson DC Richardson JS Terwilliger TC Zwart PH 《Methods (San Diego, Calif.)》2011,55(1):94-106
X-ray crystallography is a critical tool in the study of biological systems. It is able to provide information that has been a prerequisite to understanding the fundamentals of life. It is also a method that is central to the development of new therapeutics for human disease. Significant time and effort are required to determine and optimize many macromolecular structures because of the need for manual interpretation of complex numerical data, often using many different software packages, and the repeated use of interactive three-dimensional graphics. The Phenix software package has been developed to provide a comprehensive system for macromolecular crystallographic structure solution with an emphasis on automation. This has required the development of new algorithms that minimize or eliminate subjective input in favor of built-in expert-systems knowledge, the automation of procedures that are traditionally performed by hand, and the development of a computational framework that allows a tight integration between the algorithms. The application of automated methods is particularly appropriate in the field of structural proteomics, where high throughput is desired. Features in Phenix for the automation of experimental phasing with subsequent model building, molecular replacement, structure refinement and validation are described and examples given of running Phenix from both the command line and graphical user interface. 相似文献