全文获取类型
收费全文 | 411篇 |
免费 | 29篇 |
出版年
2021年 | 7篇 |
2020年 | 5篇 |
2019年 | 8篇 |
2018年 | 15篇 |
2017年 | 9篇 |
2016年 | 9篇 |
2015年 | 21篇 |
2014年 | 19篇 |
2013年 | 10篇 |
2012年 | 21篇 |
2011年 | 19篇 |
2010年 | 13篇 |
2009年 | 12篇 |
2008年 | 19篇 |
2007年 | 21篇 |
2006年 | 10篇 |
2005年 | 7篇 |
2004年 | 12篇 |
2003年 | 7篇 |
2002年 | 7篇 |
2001年 | 10篇 |
2000年 | 10篇 |
1999年 | 12篇 |
1998年 | 15篇 |
1997年 | 7篇 |
1996年 | 9篇 |
1995年 | 7篇 |
1994年 | 5篇 |
1993年 | 5篇 |
1992年 | 7篇 |
1991年 | 7篇 |
1990年 | 6篇 |
1989年 | 7篇 |
1988年 | 8篇 |
1987年 | 4篇 |
1985年 | 12篇 |
1984年 | 7篇 |
1983年 | 9篇 |
1982年 | 5篇 |
1980年 | 4篇 |
1979年 | 3篇 |
1978年 | 2篇 |
1977年 | 8篇 |
1976年 | 6篇 |
1975年 | 3篇 |
1974年 | 2篇 |
1973年 | 2篇 |
1972年 | 3篇 |
1971年 | 1篇 |
1961年 | 1篇 |
排序方式: 共有440条查询结果,搜索用时 156 毫秒
431.
Developing taste buds in the anterior mandibular floor of perihatching
chicks were studied by high voltage electron microscopic autoradiography in
order to identify proliferating gemmal cell types. Montaged profiles of 29
taste buds in five cases euthanized between embryonic day 21 and
posthatching day 2 were analyzed after a single [3H]thymidine injection
administered on embryonic day 16, 17 or 18. Results showed that dark cells
comprised 55% of identified (n = 900 cells) and 62% of labeled (n = 568
cells) gemmal cells as compared with light, intermediate, basal or
perigemmal bud cells. Dark cells had both a greater (P < 0.05) number of
labeled cells and a greater amount of label (grains/nucleus) than the other
four bud cell types, irrespective of injection day. The nuclear area
(micron 2) of dark cells was not significantly larger (P > 0.05) than
that of the other gemmal cell types and therefore cannot account for the
greater amount for label in the dark cells. Interestingly, only dark cells
showed a positive correlation (P < 0.003) between amount of label and
nuclear area. Results suggest that, during the perihatching period of
robust cell proliferation, dividing dark cells may give rise primarily, but
not exclusively, to dark cell progeny.
相似文献
432.
C.L. Brady S.N. Venter I. Cleenwerck K. Engelbeen P. de Vos M.J. Wingfield N. Telechea T.A. Coutinho 《Letters in applied microbiology》2009,49(4):461-465
Aims: This study was performed to identify bacterial strains isolated simultaneously with Pantoea species from Eucalyptus trees showing symptoms of bacterial blight and dieback in Uruguay.
Methods and Results: Several molecular techniques including 16S rRNA and rpoB gene sequencing and DNA–DNA hybridization were used to characterize the Gram-negative, facultatively anaerobic, slime-producing bacterial strains isolated along with Pantoea species from Eucalyptus . Hypersensitivity reactions (HR) and pathogenicity tests were performed on tobacco and Eucalyptus seedlings, respectively. The isolates clustered closely with the type strain of Enterobacter cowanii in both phylogenetic trees constructed. The DNA–DNA similarity between the isolates and the type strain of Ent. cowanii ranged from 88% to 92%. A positive HR was observed on the tobacco seedlings, but no disease symptoms were visible on the inoculated Eucalyptus seedlings.
Conclusions: Enterobacter cowanii was isolated from trees with symptoms of bacterial blight although strains of this bacterial species do not appear to be the causal agent of the disease.
Significance and Impact of the Study: This study provides the first report of Ent. cowanii isolated from Eucalyptus . Its presence in Eucalyptus tissue suggests that it is an endophyte in trees showing symptoms of blight. 相似文献
Methods and Results: Several molecular techniques including 16S rRNA and rpoB gene sequencing and DNA–DNA hybridization were used to characterize the Gram-negative, facultatively anaerobic, slime-producing bacterial strains isolated along with Pantoea species from Eucalyptus . Hypersensitivity reactions (HR) and pathogenicity tests were performed on tobacco and Eucalyptus seedlings, respectively. The isolates clustered closely with the type strain of Enterobacter cowanii in both phylogenetic trees constructed. The DNA–DNA similarity between the isolates and the type strain of Ent. cowanii ranged from 88% to 92%. A positive HR was observed on the tobacco seedlings, but no disease symptoms were visible on the inoculated Eucalyptus seedlings.
Conclusions: Enterobacter cowanii was isolated from trees with symptoms of bacterial blight although strains of this bacterial species do not appear to be the causal agent of the disease.
Significance and Impact of the Study: This study provides the first report of Ent. cowanii isolated from Eucalyptus . Its presence in Eucalyptus tissue suggests that it is an endophyte in trees showing symptoms of blight. 相似文献
433.
Hormonal vaginal cytology of vervet monkeys 总被引:2,自引:0,他引:2
The cellular proliferation and maturation of the vaginal epithelium of adult female Vervet monkeys was examined during their menstrual cycles. At the same time the serum contents of estrogen and progesterone were analysed. Gradual but distinct patterns demarcated the phases of the menstrual cycle cytologically. The karyopyknotic index paralleled the estrogen concentration. Mid-cycle peak maturation produced many anucleate squames, which exfoliated, forming a diagnostic vaginal discharge. 相似文献
434.
Greenhouse and microplot experiments were conducted to evaluate the damage potential of Ditylenchus destructor on four South African commercial peanut cultivars as influenced by harvest date. The cultivars Sellie and Harts should be harvested by 150 and 120 days after planting, respectively. Losses were 12-13% with early harvest, but a 15-day delay resulted in losses of 45-49%. Harvest of Natal Common and Norden at 125 and 145 days after planting, respectively, resulted in the highest seed grade. By normal harvest time (140 and 160 days, respectively) these two cultivars were downgraded to crushing seed quality. Even though seed weight increases with time, a net loss occurs if harvest is delayed. 相似文献
435.
436.
Commercial peanut cultivars were evaluated for host suitability and sensitivity to Ditylenchus destructor. All cultivars were susceptible. Approximately 94% of the final population were in the pods. Highest Pf occurred at harvest on early maturing cultivars. Damage occurred on four of six cuttivars at Pi = 100/3 liters of soil and all six cultivars at Pi = 1,000. Norden and Selmani were the most susceptible cultivars. Sellie was the most tolerant and highest yielding cultivar. This cultivar may be the most profitable one for growers. 相似文献
437.
438.
439.
440.