全文获取类型
收费全文 | 50篇 |
免费 | 7篇 |
国内免费 | 2篇 |
出版年
2023年 | 1篇 |
2022年 | 1篇 |
2020年 | 1篇 |
2019年 | 2篇 |
2018年 | 1篇 |
2017年 | 2篇 |
2016年 | 2篇 |
2015年 | 4篇 |
2014年 | 2篇 |
2013年 | 3篇 |
2012年 | 3篇 |
2011年 | 1篇 |
2010年 | 1篇 |
2009年 | 2篇 |
2008年 | 1篇 |
2007年 | 1篇 |
2006年 | 2篇 |
2005年 | 1篇 |
2004年 | 3篇 |
2003年 | 1篇 |
2002年 | 3篇 |
1998年 | 3篇 |
1997年 | 1篇 |
1996年 | 1篇 |
1995年 | 1篇 |
1993年 | 2篇 |
1992年 | 1篇 |
1987年 | 1篇 |
1984年 | 1篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1978年 | 1篇 |
1977年 | 2篇 |
1976年 | 1篇 |
1974年 | 1篇 |
1966年 | 1篇 |
1934年 | 1篇 |
1929年 | 1篇 |
排序方式: 共有59条查询结果,搜索用时 15 毫秒
1.
REINHARD B
SE KARL T. FRIEDHOFF SYLVIA OLBRICH 《The Journal of eukaryotic microbiology》1987,34(1):110-113
Four fallow deer, Cervus dama, became infected with Trypanosoma (Megatrypanum) sp. by oral application of triturated guts from tabanids collected in an area with deer but without any cattle; four control calves remained negative. Upon challenge with triturated guts from tabanids from an area with pastured cattle, the four calves became infected with Trypanosoma (M.) theileri. The prepatent period in deer was five days or less. Haematopota spp. and Tabanus spp. were identified as vectors of the deer trypanosomes. It is concluded that the trypanosomes of C. dama belong to a Megatrypanum species that is not identical with T. theileri. 相似文献
2.
The apple rootstock,A106(Malus sieboldii),had 17 bivalents in pollen mother cells at meiotic metaphase 1,and 17 chromosomes in a haploid pollen cell.Karyotypes were prepared from root-tip cells with 2n=34 chromosomes,Seven out of 82 karyotypes(8.5%) showed one pari of satellites at the end of the short arm of chromosome 3.C-bands were shown on 6 pairs of chromosomes 2,4,6,8,14,and 16 near the telomeric regions of short arms.Probes for three ripening-related genes from Malus x domestica:endopolygalacturonase(EPG,0.6kb),ACC oxidase(1.2kb),and ACC synthase(2kb)were hybridized in situ to metaphase chromosomes of A106.Hybridization sites for the EPG gene were observed on the long arm of chromosome 14 in 15 out of 16 replicate spreads and proximal to the centromere of chromosomes 6 and 11.For the ACC oxidase gene,hylridization sites were observed in the telomeric region of the short arm of chromosomes 5 and 11 in 87% and 81% of 16 spreads respectively,proxiaml to the centromere of chromosome 1 in 81% of the spreads,and on the long arm of chromosome 13 in 50% of the spreads. Physical mapping of three fruit ripening genes in an apple rootstock A106.Twenty five spreads were studied for the ACC synthase gene and hybridization sites were observed in the telomeric region of the short arm of chromosome 12 in 96% of the spreads.chromosomes 9 and 10 in 76% of the spreads,and chromosome 17 in 56% of the spreads. 相似文献
3.
The cytokineplast: purified, stable, and functional motile machinery from human blood polymorphonuclear leukocytes 总被引:11,自引:4,他引:7 下载免费PDF全文
We examined the formation of motile, chemotactically active, anucleate fragments from human blood polymorphonuclear leukocytes (PMN, granulocytes), induced by the brief application of heat. These granule-poor fragments are former protopods (leading fronts, lamellipodia) that become uncoupled from the main body of the cell and leave it, at first with a connecting filament that breaks and seals itself. The usual random orientation of such filaments can be controlled by preorientation of cells in a gradient of the chemotactic peptide, N-formylmethionylleucylphenylalanine (F-Met-Leu-Phe) (2x10(-9) M- 1x10(-8)). Cytochalsin B, 2.5-5 μg/ml, prevents fragment formation; colchicine, 10(-5) M, does not. In scanning electron micrographs, fragments are ruffled and the cell body rounded up and rather smooth. In transmission electron micrographs, fragments contain microfilaments but lack centrioles and microtubules. Like intact cells, both bound and free fragments can respond chemotactically to an erythrocyte destroyed by laser microirradiation (necrotaxis); the free, anucleate fragments may do so repeatedly, even after having been held overnight at ambient temperatures. We propse the name cytokineplast for the result of this self-purification of motile apparatus. The exodus of the motile machinery from the granulocyte requires anchoring of the bulk of the cell to glass and uncoupling, which may involve heat-induced dysfunction of the centrosome. In ultrastructural studies of the centrosomal region after heat, centriolar structure remains intact, but pericentriolar osmiophilic material appears condensed, and microtubules are sparse. These changes are found in all three blood cell types examined: PMN, eosinophil, and monocyte. Of these, the first two make fragments under our conditions; the more sluggish monocyte does not. Uncoupling is further linked to centrosomal dysfunction by the observation that colchicines-treated granulocytes (10(-5)M, to destroy the centrosome’s efferent arm) make fragments after less heat than controls. If motive force and orientation are specified mainly from the organelle-excluding leading front, then endoplasmic streaming in PMN is a catch-up phenomenon, and microtubules do not provide the vector of locomotion but rather stabilize and orient the “baggage” (nucleus, granuloplasm)—i.e., they prevent fishtailing. Moreover, constraints emanating from the centrosome may now be extended to include, maintenance of the motile machinery as an integral part of the cell. 相似文献
4.
Hernandez-Trejo A B Estrada-Drouaillet JA López-Santillán C Rios-Velasco SE Varela-Fuentes R Rodríguez-Herrera E Osorio-Hernández 《Phyton》2019,88(1):47-54
The control of Spodoptera frugiperda is based
on synthetic insecticides, so some alternatives are the use of
entomopathogenic fungi (EF) and neem extract. The objective of
the study was to evaluate in vitro effectiveness of native EF and
neem extracts on S. frugiperda larvae. Six EF were identified by
DNA sequencing of ITS regions from three EF (Fusarium solani,
Metarrhizium robertsii, Nigrospora spherica and Penicillium
citrinum). They were evaluated in concentrations of 1 × 10⁸ spores/
mL. In addition, a second bioassay was carried out evaluating
only F. solani, M. robertsii and N. sphaerica and the addition
of vegetable oil. On the other hand, extraction of secondary
metabolites from neem seed (Azadirachta indica) was carried
out by performing, mass (g) and solvent volume (mL ethanol
and water) combinations, which were subjected to microwaves
and ultrasound. Subsequently, these extracts were evaluated
in concentrations of 3%, 4% and 5%. A survival analysis was
performed for each of the bioassays. With respect to the results
of the first bioassay, F. solani obtained a probability of survival of
0.476 on the seventh day, while in the second bioassay, M. robertsii
obtained 0.488 survival probability. This suggests that the expected
percentage of larvae that stay alive on the sixth day is 48.8%.
However, in the evaluation of the neem extract the combination
1:12/70% to 4% caused 84% mortality of larvae. The use of native
HE and neem extracts has potential for the control of S. frugiperda. 相似文献
5.
Barcoding diatoms: exploring alternatives to COI-5P 总被引:2,自引:0,他引:2
Diatoms are a diverse lineage with species that can be difficult to identify or cryptic, but DNA barcoding, a molecular technique, can assist identification and facilitate studies of speciation and biogeography. The most common region used for DNA barcoding, COI-5P, can distinguish diatom species, but has not displayed universality (i.e., successful PCR amplification from diverse taxa). Therefore, we have assessed the following alternative markers: ~1400bp of rbcL; 748bp at the 3' end of rbcL (rbcL-3P); LSU D2/D3 and UPA. Sellaphora isolates were used to determine each marker's ability to discriminate among closely related species and culture collection material was utilized to explore further marker universality. All of the alternative markers investigated have greater universality than COI-5P. Both full and partial (3P) rbcL regions had the power to discriminate between all species, but rbcL-3P can be sequenced more easily. LSU D2/D3 could distinguish between all but the most closely related species (96%), whereas UPA only distinguished 20% of species. Our observations suggest that rbcL-3P should be used as the primary marker for diatom barcoding, while LSU D2/D3 should be sequenced as a secondary marker to facilitate environmental surveys. 相似文献
6.
DALDINIA CONCENTRICA ATTACKING THE WOOD OF FRAXINUS EXCELSIOR 总被引:1,自引:0,他引:1
7.
Limited molecular data for marine tube-forming diatoms are available currently and this study provides the first molecular survey of these taxa. To conduct this survey, we used a molecular-assisted alpha taxonomy (MAAT) approach that utilizes DNA barcode data. We used three DNA barcode markers: the 3´ end of the large subunit of RUBISCO (rbcL-3P); the variable D2/D3 region of the nuclear large subunit ribosomal DNA (LSU D2/D3); and the internal transcribed spacer 2 (ITS2) to assign marine tube-forming diatoms from Canada to genetic species groups. The rbcL-3P analysis uncovered 29 genetic groups including representatives of Haslea crucigera, Navicula bottnica, N. brunelii, N. ramosissima, Nitzschia fontifuga, N. tubicola, Parlibellus berkeleya and P. delognei f. elliptica, as well as a complex of 14 closely related groups morphologically consistent with Berkeleya rutilans. We sequenced ITS2 for representatives of the B. rutilans complex; these data were consistent with the rbcL-3P genetic clusters for 86% of the colonies tested. The remaining 14% were in conflict, possibly indicating that more than a single Berkeleya genetic species was present in each colony. To investigate this hypothesis further, we developed ‘species-specific’ ITS2 primers and confirmed heterogeneity of Berkeleya genetic species in 64% of the colonies tested (N = 91). Therefore, a taxonomic assessment of tube-forming species that were originally described on the basis of colony morphology (e.g. Berkeleya rutilans) can only proceed using clonal cultures or single-cell analysis. 相似文献
8.
Effects of Temperature and Photorepair Radiation on a Marine Ciliate Exposed to UVB Radiation 下载免费PDF全文
Sarah E. Hamsher Cheng Yun Tina Sung Robert W. Sanders 《The Journal of eukaryotic microbiology》2018,65(4):458-467
The influences of intensity and repeated exposure to ultraviolet‐B radiation (UVB), photoreactivating repair radiation (PRR), and temperature on the scuticociliate Parauronema acutum were explored under laboratory conditions. Population growth was negatively affected after exposure to the equivalent of one sunny summer day of ambient UVB, especially in the absence of PRR. Repeated daily exposure to UVB severely compromised ciliate survival. UVB‐exposed treatments without PRR recovered slower and reached lower final abundances than treatments receiving PRR. Reducing the daily UVB exposure approximately 25% improved ciliate recovery after exposure. In the single exposure treatments, temperature effects were not consistent, except that growth was slowest for control and treatments at the lowest temperature (15 °C). These data suggest that dark repair and/or photoprotection are present in P. acutum, but photoenzymatic repair was the more effective mechanism in reversing UVB damage. Repeated exposure treatments without PRR had zero or declining growth at all temperatures (15, 20 and 25 °C), as did those with PRR at 15 °C. Significant temperature/dose differences were identified in the repeated exposure treatments; ciliates subjected to the higher UVB intensity with PRR survived only at 25 °C, while ciliate populations under reduced UVB increased at 20 and 25 °C. 相似文献
9.
L. Vimercati S. Hamsher Z. Schubert S. K. Schmidt 《Extremophiles : life under extreme conditions》2016,20(5):579-588
Soils above 6000 m.a.s.l. are among the most extreme environments on Earth, especially on high, dry volcanoes where soil temperatures cycle between ?10 and 30 °C on a typical summer day. Previous studies have shown that such sites are dominated by yeast in the cryophilic Cryptococcus group, but it is unclear if they can actually grow (or are just surviving) under extreme freeze–thaw conditions. We carried out a series of experiments to determine if Cryptococcus could grow during freeze–thaw cycles similar to those measured under field conditions. We found that Cryptococcus phylotypes increased in relative abundance in soils subjected to 48 days of freeze–thaw cycles, becoming the dominant organisms in the soil. In addition, pure cultures of Cryptococcus isolated from these same soils were able to grow in liquid cultures subjected to daily freeze–thaw cycles, despite the fact that the culture medium froze solid every night. Furthermore, we showed that this organism is metabolically versatile and phylogenetically almost identical to strains from Antarctic Dry Valley soils. Taken together these results indicate that this organism has unique metabolic and temperature adaptations that make it able to thrive in one of the harshest and climatically volatile places on Earth. 相似文献
10.
Phenylalanine uptake in Chlorella fusca was measured, using the membrane filter technique. The cells were synchronized, and harvested at specific points of the life cycle. Experiments with autospores showed that the uptake followed saturation kinetics, with a Km= 5 μM. Vmax, was 0.1 nmol/min × 107 cells. The optimum temperature for the uptake was 40°C, and the activation energy was 1700 J/mol. The uptake showed a high specificity towards l -phenylalanine; presence of the unlabelled stereoisomer did not inhibit the uptake. Uptake of l -phenylalanine was inhibited in the presence of other analogues or other amino acids, but only if they were present in concentrations considerably higher than that of L-phenylalanine. Variations in the ratio of Na4+ to K+ in the external solution during uptake experiments did not have any influence upon the uptake rate of l -phenylalanine. The cells were able to take up the amino acid against a concentration gradient. At pool maximum the ratio between internal and external amino acid concentration was 1000/1. 2,4-Dinitro-phenol inhibited the uptake completely. Exchange between internal and external l -phenylalanine could not be demonstrated. The Km value did not change during the life cycle of the cells. The uptake rate reached a maximum at the end of the light period, and fell to a minimum just before sporulation started. It is concluded that Chlorella fusca cells have a highly specific, active uptake system for l -phenylalanine. The system is constitutive, independent on the K or Na concentration, and the mechanism of uptake does not change during the life cycle of the cells. 相似文献