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101.
Cell-free mercury volatilization activity from three marine caulobacter strains. 总被引:2,自引:1,他引:1 下载免费PDF全文
Three mercury-resistant marine Caulobacter strains showed an inducible mercury volatilization activity. Cell-free mercury volatilization (mercuric reductase) from these three marine Caulobacter strains was characterized and compared with enzyme activities determined by plasmids of Escherichia coli and Staphylococcus aureus. The temperature sensitivity of the Caulobacter mercuric reductase was greater than that of mercuric reductase from other gram-negative sources. Cell-free enzyme activity required NADH or NADPH, with NADPH functioning much better at lower concentrations than NADH. The Km for the Caulobacter enzyme was 4 microM Hg2+. Ag+ was a competitive inhibitor of Caulobacter mercuric reductase (Ki = 0.2 microM Ag+), as with previously studied enzymes. Arsenite was a noncompetitive inhibitor of the Caulobacter enzyme with a Ki of 75 microM AsO2-. 相似文献
102.
Methanogenesis in the hypersaline Solar Lake (Sinai) 总被引:2,自引:0,他引:2
Dieter Giani Luise Giani Yehuda Cohen Wolfgang E. Krumbein 《FEMS microbiology letters》1984,25(2-3):219-224
Abstract Enrichment studies on microbial mat sediments (potential stromatolites) from the hypersaline Solar Lake (Sinai) indicated high numbers of methanogenic bacteria (up to 105 ml−1 sediment) in spite of the high sulfate reduction rate, sulfate concentration and salinity. Among H2 /CO2 , acetate and monomethylamine, the methylated amine was the preferred substrate. The predominant species enriched was a Methanosarcina sp. The findings indicate that methanogenic bacteria play an important role in hypersaline sulfate-enriched anoxic sediments and stromatolithic microbial mats. 相似文献
103.
The neuropharmacological basis for d-amphetamine induced paradoxical behavioral thermoregulation remains unclear. This study examined thermoregulatory behavior of rats in a runway device that housed a heat source at one end and in which locomotion along the length of the runway could be observed. Sprague Dawley rats were pretreated with IP injections of saline, beta-endorphin, MIF-1, or alpha-MSH, with a repeat injection after 30 min. In a second experiment, d-amphetamine was administered as the repeat drug for all Ss. The results showed clear differences for heat-source-on vs. heat-source off. All peptides induced hypermotility, although no differentiated effects for the peptides on d-amphetamine induced paradoxical behavioral thermoregulation were found. These findings are discussed in light of the theoretical possibilities that: (a) a ceiling effect exists; (b) there are separate control systems for maintaining body temperature and another for behavioral thermoregulatory responses, and (c) other neurotransmitters may be involved in such induced paradoxical behavioral thermoregulation. 相似文献
104.
We have developed a new method for protein secondary structure prediction that achieves accuracies as high as 71.0%, the highest value yet reported. The main component of our method is a nearest-neighbor algorithm that uses a more sophisticated treatment of the feature space than standard nearest-neighbor methods. It calculates distance tables that allow it to produce real-valued distances between amino acid residues, and attaches weights to the instances to further modify the the structure of feature space. The algorithm, which is closely related to the memory-based reasoning method of Zhang et al., is simple and easy to train, and has also been applied with excellent results to the problem of identifying DNA promoter sequences. 相似文献
105.
Scanning electron microscopy of surface morphology of embryonic neural retina cells in suspension revealed striking age-dependent differences between trypsin-dissociated and EGTA-separated cells (EGTA, ethylene bis[oxyethylene nitrolo]tetra-acetic acid). Trypsinized cells were characterized by numerous filopodial processes, ruffles and a relatively smooth-textured cell membrane. EGTA treatment resulted in only partial cell separation, paucity or absence of elongated filopodia, and a coarse-textured cell membrane. The findings are briefly considered in the context of age-dependent differences in retina cell interactions, cell surface properties, and the effects of the two methods of cell separation on the cell surface. 相似文献
106.
Yehuda Kott 《Hydrobiologia》1968,32(1-2):161-169
Summary Concentrations of 50 mg/l nitrate (as NO3
–) and 20 mg/l phosphate (as PO4---) were found to be optimal for algal growth in experimental citrus waste oxidation ponds.Reliable results were only obtained after three weeks of detention. Nitrogen or phosphorus alone did not suffice for stimulating algal growth but had to be used together. Dilution of the waste resulted in very poor growth.Several inexpensive fertilizers were compared with sodium nitrate and phosphate and were found to give an equivalent algal yield.
This study was sponsored by the Ministry of Agriculture — Water Commission. 相似文献
Résumé Pour le développement des algues dans des ponds d'oxidation expímentales du dechet de l'industrie des agrumes les concentrations ci dessous ont été trouvées optimales: 50 mg/1 de nitrate (NO3 –) et 20 mg/1 phosphate (PO4---). On n'a obtenu des réesultats satisfaisants qu'apres trois semaines de detention.Seulement l'azote or le phosphore ne stimule pas le développement des algues: il faut les utiliser en conjunction.La prolifération des algues dans des eaux résiduaires diluées est très faible.Plusieurs engrais moins chers ont été comparés au nitrate de soude et au phosphate et ont donné des résultats équivalents aux développement des algues.
This study was sponsored by the Ministry of Agriculture — Water Commission. 相似文献
107.
Genome re-annotation: a wiki solution? 总被引:1,自引:0,他引:1
Salzberg SL 《Genome biology》2007,8(1):102
The annotation of most genomes becomes outdated over time, owing in part to our ever-improving knowledge of genomes and in part to improvements in bioinformatics software. Unfortunately, annotation is rarely if ever updated and resources to support routine reannotation are scarce. Wiki software, which would allow many scientists to edit each genome's annotation, offers one possible solution. 相似文献
108.
Jinxue Luo Jinsong Zhang Robert J. Barnes Xiaohui Tan Diane McDougald Anthony G. Fane Guoqiang Zhuang Staffan Kjelleberg Yehuda Cohen Scott A. Rice 《Microbial biotechnology》2015,8(3):549-560
A novel strategy to control membrane bioreactor (MBR) biofouling using the nitric oxide (NO) donor compound PROLI NONOate was examined. When the biofilm was pre‐established on membranes at transmembrane pressure (TMP) of 88–90 kPa, backwashing of the membrane module with 80 μM PROLI NONOate for 45 min once daily for 37 days reduced the fouling resistance (Rf) by 56%. Similarly, a daily, 1 h exposure of the membrane to 80 μM PROLI NONOate from the commencement of MBR operation for 85 days resulted in reduction of the TMP and Rf by 32.3% and 28.2%. The microbial community in the control MBR was observed to change from days 71 to 85, which correlates with the rapid TMP increase. Interestingly, NO‐treated biofilms at 85 days had a higher similarity with the control biofilms at 71 days relative to the control biofilms at 85 days, indicating that the NO treatment delayed the development of biofilm bacterial community. Despite this difference, sequence analysis indicated that NO treatment did not result in a significant shift in the dominant fouling species. Confocal microscopy revealed that the biomass of biopolymers and microorganisms in biofilms were all reduced on the PROLI NONOate‐treated membranes, where there were reductions of 37.7% for proteins and 66.7% for microbial cells, which correlates with the reduction in TMP. These results suggest that NO treatment could be a promising strategy to control biofouling in MBRs. 相似文献
109.
110.
Ayelet Zauberman Avital Tidhar Yinon Levy Erez Bar-Haim Gideon Halperin Yehuda Flashner Sara Cohen Avigdor Shafferman Emanuelle Mamroud 《PloS one》2009,4(6)
An important virulence strategy evolved by bacterial pathogens to overcome host defenses is the modulation of host cell death. Previous observations have indicated that Yersinia pestis, the causative agent of plague disease, exhibits restricted capacity to induce cell death in macrophages due to ineffective translocation of the type III secretion effector YopJ, as opposed to the readily translocated YopP, the YopJ homologue of the enteropathogen Yersinia enterocolitica O∶8. This led us to suggest that reduced cytotoxic potency may allow pathogen propagation within a shielded niche, leading to increased virulence. To test the relationship between cytotoxic potential and virulence, we replaced Y. pestis YopJ with YopP. The YopP-expressing Y. pestis strain exhibited high cytotoxic activity against macrophages in vitro. Following subcutaneous infection, this strain had reduced ability to colonize internal organs, was unable to induce septicemia and exhibited at least a 107-fold reduction in virulence. Yet, upon intravenous or intranasal infection, it was still as virulent as the wild-type strain. The subcutaneous administration of the cytotoxic Y. pestis strain appears to activate a rapid and potent systemic, CTL-independent, immunoprotective response, allowing the organism to overcome simultaneous coinfection with 10,000 LD50 of virulent Y. pestis. Moreover, three days after subcutaneous administration of this strain, animals were also protected against septicemic or primary pneumonic plague. Our findings indicate that an inverse relationship exists between the cytotoxic potential of Y. pestis and its virulence following subcutaneous infection. This appears to be associated with the ability of the engineered cytotoxic Y. pestis strain to induce very rapid, effective and long-lasting protection against bubonic and pneumonic plague. These observations have novel implications for the development of vaccines/therapies against Y. pestis and shed new light on the virulence strategies of Y. pestis in nature. 相似文献