全文获取类型
收费全文 | 633篇 |
免费 | 88篇 |
出版年
2021年 | 9篇 |
2019年 | 5篇 |
2018年 | 8篇 |
2017年 | 5篇 |
2016年 | 11篇 |
2015年 | 17篇 |
2014年 | 25篇 |
2013年 | 29篇 |
2012年 | 37篇 |
2011年 | 24篇 |
2010年 | 20篇 |
2009年 | 20篇 |
2008年 | 25篇 |
2007年 | 26篇 |
2006年 | 15篇 |
2005年 | 16篇 |
2004年 | 10篇 |
2003年 | 17篇 |
2002年 | 22篇 |
2001年 | 17篇 |
2000年 | 15篇 |
1999年 | 27篇 |
1998年 | 6篇 |
1997年 | 10篇 |
1996年 | 9篇 |
1995年 | 7篇 |
1994年 | 13篇 |
1993年 | 5篇 |
1992年 | 5篇 |
1991年 | 9篇 |
1990年 | 10篇 |
1989年 | 14篇 |
1988年 | 16篇 |
1987年 | 15篇 |
1986年 | 15篇 |
1985年 | 11篇 |
1984年 | 12篇 |
1982年 | 6篇 |
1981年 | 9篇 |
1980年 | 7篇 |
1979年 | 12篇 |
1978年 | 7篇 |
1976年 | 5篇 |
1975年 | 6篇 |
1974年 | 10篇 |
1973年 | 14篇 |
1971年 | 6篇 |
1970年 | 9篇 |
1969年 | 9篇 |
1968年 | 12篇 |
排序方式: 共有721条查询结果,搜索用时 31 毫秒
101.
Characterization of an endosymbiont infecting wood ticks, Dermacentor andersoni, as a member of the genus Francisella.
下载免费PDF全文
![点击此处可从《Applied microbiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
M L Niebylski M G Peacock E R Fischer S F Porcella T G Schwan 《Applied microbiology》1997,63(10):3933-3940
A microorganism (Dermacantor andersoni symbiont [DAS]) infecting Rocky Mountain wood ticks (D. andersoni) collected in the Bitterroot Mountains of western Montana was characterized as an endosymbiont belonging to the genus Francisella. Previously described as Wolbachia like, the organism's DNA was amplified from both naturally infected tick ovarial tissues and Vero cell cultures by PCR assay with primer sets derived from eubacterial 16S ribosomal DNA (rDNA) and Francisella membrane protein genes. The 16S rDNA gene sequence of the DAS was most similar (95.4%) to that of Francisella tularensis subsp. tularensis. Through a combination of Giménez staining, PCR assay, and restriction fragment length polymorphism analysis, 102 of 108 female ticks collected from 1992 to 1996 were infected. Transovarial transmission to female progeny was 95.6%, but we found no evidence of horizontal transmission. 相似文献
102.
Two Eucalyptus homologues of the Arabidopsis floral homeotic gene AP1 (EAP1 and EAP2/) show 60–65% homology to AP1. EAP1 and EAP2 are expressed predominantly in flower buds. EAP2 produces two different polypeptides arising from differential splicing at an intron, the shorter EAP2 protein diverging from the longer sequence after amino acid 197 and having a translation stop after residue 206. This truncated protein includes both MADS- and K-box amino acid sequences. Ectopic expression of the EAP1 or either of the two EAP2 polypeptides in Arabidopsis driven by the 35S promoter produces effects similar to the corresponding AP1 construct, causing plants to flower earlier, have shorter bolts and resemble the terminal flower mutant (tfl). 相似文献
103.
1 Phratora vulgatissima (Chrysomelidae) is the major pest of short-rotation coppice willows in the U.K., capable of causing severe defoliation in monoculture plantations. As this beetle shows feeding preferences between willow clones, knowledge of the spatio-temporal dynamics of P. vulgatissima is needed in order to assess the effects of mixed clonal plantings on the management of this pest. 2 Distribution patterns of adult P. vulgatissima were monitored over a season at a spatial scale of every tree or every other tree in single clone plantings (monocultures) of three willow clones and in a regular row mixture of these clones. 3 Distribution indices (deviation from Complete Spatial Randomness) demonstrated that P. vulgatissima adults were spatially aggregated on favourable clones in the monocultures and the mixture. The degree of aggregation (measured by the k-parameter of the negative binomial) differed between willow clones. Beetles were highly aggregated at the start of the season, but less so later. 4 Dispersal studies of P. vulgatissima adults over time showed a pattern of beetle infestation along rows of the preferred clones in a regularly structured mixture. In the monocultures, movement was less directional. 5 Plantation design offers some potential for more effective non-chemical pest management for P. vulgatissima. Monitoring of the pest must take account of our findings that adults occur in mobile aggregations. 相似文献
104.
The effect of simulated beetle damage (0%, 25%, 50% and 75% mechanical defoliation) on 12 willow genotypes, grown in short‐rotation coppice, was studied in a modified criss‐cross experimental design. The design enabled the above‐ground effects of monoculture and mixed planting to be assessed. Repeated measurements were modelled to produce derived variables in terms of time or, more appropriately, in terms of accumulated day length (i.e. ‘developmental time’) units. These derived variables were then analysed using the REsidual Maximum Likelihood (REML) method implemented in GenStat? (2001) . No significant competition effect between the genotypes due to planting regime was detected. Genotypes Salix viminalis × Salix schwerinii‘Beagle’ and S. viminalis × S. schwerinii‘Torhild’ were found to have the greatest rate of increase in leaves regardless of defoliation and also the greatest height prior to defoliation. Genotype Salix dasyclados‘Loden’ showed the highest rate of growth under the stress of defoliation. When assessing height at the end of the growing season, S. viminalis × S. schwerinii‘Olof’ was the highest genotype for 25% and 75% levels of defoliation, but genotypes Salix aurita × Salix cinerea‘Delamere’, Loden and S. viminalis × Salix burjatica‘Ashton Parfitt’ appeared to be most tolerant by having consecutively lower base day lengths (i.e. increasing the accumulation of developmental units and the length of the growing season) for increasing defoliation. Shorter genotypes tended to be more tolerant, but of the higher genotypes reaching a control height of greater than 3 m by the end of the growing season, S. viminalis × S. schwerinii‘Tora’ and Beagle performed best to 50% defoliation. 相似文献
105.
J. Cory C. E. Yunker R. A. Ormsbee M. Peacock H. Meibos G. Tallent 《Applied microbiology》1974,27(6):1157-1161
Clear-cut and repeatable plaque assays were obtained for three rickettsiae of the spotted fever group (Rickettsia rickettsi, R. conori, and R. montana) in Vero cells used in a manner similar to that for arboviruses. In addition, three typhus group agents (R. typhi, R. canada, R. prowazeki) induced plaques in these cells. In preliminary tests Coxiella burneti (Nine Mile strain) failed to produce plaques. Comparable results were obtained in plastic flasks and plastic culture trays incubated in ambient air with or without addition of N-2-hydroxyethyl-piperazine-N'-2-ethanesulfinic acid buffer. Larger and more well defined R. rickettsi plaques were produced when cultures were overlaid with Leibovitz (L15) medium than with either medium 199 or Eagle medium. Phosphate-buffered saline containing bovine plasma albumin (fraction V), in contrast to brain heart infusion broth, as a diluent for preparing inocula consistently permitted development of larger and more numerous plaques with three agents: R. rickettsi, R. conori, and R. montana. When R. rickettsi and R. typhi were assayed in parallel in primary chicken embryo cultures and Vero cells, comparable results were obtained, but with R. canada results in Vero cells were superior. In contrast, R. prowazeki produced inconsistent results in Vero cells. 相似文献
106.
An active electrical response in fibroblasts 总被引:9,自引:3,他引:6
L cells have a resting potential of about -16 mv (internal negative) at 37°C in Dulbecco''s modified Eagle''s medium containing 10% fetal calf serum and a potassium concentration of 5.4 mM. Membrane resistivity is about 20,000 Ωcm2 when the surface filopodia described by others are taken into account. Mechanical and electrical stimuli can evoke an active response from mouse L cells, cells of the 3T3 line, and normal fibroblasts which we have termed hyperpolarizing activation or the H.A. response. This consists of a prolonged (3–5 sec) increase in the membrane permeability by a factor of 2–10 with a parallel increase in membrane potential to about -50 mv. The reversal potential for the H.A. response is -80 mv. The resting cells are depolarized to about -12 mv when the external medium contains 27 mM potassium, and the potential reached at the peak of the H.A. response is about -30 mv. The reversal potential for the H.A. response is about -40 mv in 27 mM external potassium. This effect of potassium ions on the reversal potential of the H.A. response leads us to conclude that the response represents an increase in membrane permeability, predominantly to potassium, by at least a factor of five. This increase must be greater than 20-fold if previous measurements of the ratio of potassium permeability to chloride permeability in L cells are valid for the preparation used in the present study. 相似文献
107.
Mouse neuroblastoma cells have been tested for their responsiveness to iontophoretically applied acetylcholine, norepinephrine, dopamine, and serotonin using intracellularly recorded membrane potential and resis tance as indicators of response. Acetylcholine can elicit either a membrane depolarization (D-response) or hyperpolarization (H-response) or a compound D-H response from different neuroblastoma cells of a given culture. Some 60 to 70% of tested cells gave no measurable response. A change of culture medium (from DMEM to F-12) increased the incidence of H-responses 2-fold. Dopamine elicited H-responses in about one-quarter of cells tested, while no responses were elicited by norepinephrine or serotonin in a small sample of cells. 相似文献
108.
Haptoglobin--hemoglobin interaction. Stoichiometry 总被引:1,自引:0,他引:1
109.
110.
John A.M. Ramshaw Derek Peacock Barry T. Meatyard Donald Boulter 《Phytochemistry》1974,13(12):2783-2789
The amino acid sequence of Epiteromorpha cytochrome c has been added to an affinity tree relating the cytochrome c sequences of animals, plants, fungi, protozoans and one bacterium, cytochrome c2 from Rhodospirillum. The Enteromorpha sequence lies on the line of descent of the higher plant sequences; it is not closely related to the cytochrome c of the photosynthetic protozoan, Euglena. The distribution of ε-N-trimethyllysine in cytochrome c is discussed. 相似文献