全文获取类型
收费全文 | 107篇 |
免费 | 10篇 |
出版年
2021年 | 1篇 |
2020年 | 2篇 |
2019年 | 4篇 |
2017年 | 5篇 |
2016年 | 2篇 |
2015年 | 1篇 |
2014年 | 5篇 |
2013年 | 5篇 |
2012年 | 3篇 |
2011年 | 10篇 |
2010年 | 6篇 |
2009年 | 3篇 |
2008年 | 5篇 |
2007年 | 4篇 |
2006年 | 2篇 |
2005年 | 3篇 |
2004年 | 5篇 |
2003年 | 3篇 |
2002年 | 4篇 |
2001年 | 1篇 |
2000年 | 6篇 |
1999年 | 2篇 |
1998年 | 2篇 |
1997年 | 2篇 |
1996年 | 2篇 |
1995年 | 3篇 |
1993年 | 1篇 |
1991年 | 2篇 |
1989年 | 2篇 |
1987年 | 1篇 |
1985年 | 1篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1978年 | 2篇 |
1977年 | 3篇 |
1976年 | 1篇 |
1975年 | 2篇 |
1973年 | 2篇 |
1972年 | 2篇 |
1971年 | 1篇 |
1969年 | 1篇 |
排序方式: 共有117条查询结果,搜索用时 14 毫秒
81.
Flounders offer unique opportunities to study the cytological basis of vertebrate pigmentation. Individual skin pigment cells are clearly visible at hatching, and flounder ontogeny includes a dramatic shift in overall pigmentation (from symmetrical to asymmetrical) during metamorphosis. Moreover, several types of malpigmentation occur in hatchery populations; although much effort has gone into reducing the frequency of such defects, their etiology remains poorly understood, and they have rarely been described at the cellular level. In this paper, we use light and fluorescence microscopy to describe the cytological basis of normal developmental changes and of common types of malpigmentation. We then discuss the implications of these observations for underlying patterning mechanisms. 相似文献
82.
E Quist 《Archives of biochemistry and biophysics》1985,236(1):140-149
The properties of the enzymes involved in Ca2+-stimulated breakdown of phosphatidylinositol 4'-phosphate (PIP), phosphatidylinositol 4',5'-bisphosphate (PIP2), and phosphatidic acid (PA) in rabbit erythrocyte ghosts were studied. At 25 degrees C, 1 to 180 microM Ca2+ rapidly stimulated the breakdown of PIP and PIP2, and maximal breakdown occurred within 10 minutes at all Ca2+ concentrations. The rate and the total amount of breakdown of PA, PIP, and PIP2 increased with Ca2+ concentration. MgCl2 inhibited the rate of Ca2+-stimulated breakdown of PIP and PIP2 at Ca2+ concentrations less than 10 microM, but did not have any appreciable effects at higher Ca2+ concentrations. MgCl2 also protected against Ca2+-stimulated breakdown of PA. In the presence and absence of 5 mM MgCl2, Ca2+ stimulated half-maximal breakdown of PIP and PIP2 at 2-3 microM under hypotonic and isotonic conditions. In the presence of 5 mM MgCl2, Ca2+-stimulated breakdown of PIP and PIP2 was associated with the release of Pi and inositol bisphosphate. In the absence of MgCl2, Ca2+ stimulated the release of 32P-labeled Pi, inositol bisphosphate, and inositol trisphosphate from labeled PIP, PIP2, and PA. Ca2+ increased phosphatidylinositol content and decreased PIP and PIP2 content in these membranes. The results of this investigation suggest that Ca2+ stimulates the breakdown of polyphosphoinositides by stimulating polyphosphoinositide phosphomonoesterase and phosphodiesterase activities in rabbit erythrocyte ghosts. These activities were activated by less than 3 microM Ca2+ in the presence of MgCl2 under hypotonic or isotonic conditions. These Ca2+-stimulated polyphosphoinositide phosphoesterase activities could therefore be active under physiological conditions in normal rabbit erythrocytes. 相似文献
83.
Complete nucleotide sequences of bovine alpha S2- and beta-casein cDNAs: comparisons with related sequences in other species 总被引:2,自引:0,他引:2
Stewart AF; Bonsing J; Beattie CW; Shah F; Willis IM; Mackinlay AG 《Molecular biology and evolution》1987,4(3):231-241
The nucleotide sequences corresponding to bovine alpha S2- and beta- casein
mRNAs have been determined by cDNA analysis. Both sequences appear to be
complete at their 5' ends. The nucleotide sequence of alpha S2-casein, when
compared with the corresponding cavine A sequence, helps to define the
boundaries of a large amino acid repeat (approximately 80 residues) whereas
comparisons with the nucleotide sequences of rat gamma- and mouse
epsilon-casein mRNAs also reveal extensive sequence similarities. An
alignment of these four sequences shows that the divergence of their
translated regions has been characterized by the duplication and deletion
of discrete segments of sequence that probably correspond to exons. A high
degree of nucleotide substitution is also found when the four sequences are
compared, except for well-conserved leader-peptide and phosphorylation-site
sequences and, to a lesser extent, the 5'-untranslated regions. Similar
comparison of the bovine and rat beta-caseins shows that their divergence
has involved a high rate of nucleotide substitution but that no major
insertions or deletions of sequence have occurred. The several splice sites
that have veen defined in the rat beta-casein gene are likely to have been
conserved in the bovine. The contrasting evolutionary histories of the
alpha- and beta-casein coding sequences correlate with the distinctive
functions of these proteins in the casein micelle system in milk.
相似文献
84.
P O Quist 《Biophysical journal》1998,75(5):2478-2488
The natural-abundance 13C NMR spectrum of gramicidin A in a lipid membrane was acquired under magic-angle spinning conditions. With fast sample spinning (15 kHz) at approximately 65 degrees C the peaks from several of the aliphatic, beta-, alpha-, aromatic, and carbonyl carbons in the peptide could be resolved. The resolution in the 13C spectrum was superior that observed with 1H NMR under similar conditions. The 13C linewidths were in the range 30-100 Hz, except for the alpha- and beta-carbons, the widths of which were approximately 350 Hz. The beta-sheet-like local structure of gramicidin A was observed as an upfield shift of the gramicidin alpha and carbonyl resonances. Under slow sample spinning (500 Hz), the intensity of the spinning sidebands from 13C in the backbone carbonyls was used to determine the residual chemical shift tensor. As expected, the elements of the residual chemical shift tensor were consistent with the single-stranded, right-handed beta6.3 helix structure proposed for gramicidin A in lipid membranes. 相似文献
85.
Methylated sulfur compounds in microbial mats: in situ concentrations and metabolism by a colorless sulfur bacterium. 总被引:9,自引:8,他引:1
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)
The concentrations of the volatile organic sulfur compounds methanethiol, dimethyl disulfide, and dimethyl sulfide (DMS) and the viable population capable of DMS utilization in laminated microbial ecosystems were evaluated. Significant levels of DMS and dimethyl disulfide (maximum concentrations of 220 and 24 nmol cm3 of sediment-1, respectively) could be detected only at the top 20 mm of the microbial mat, whereas methanethiol was found only at depth horizons from 20 to 50 mm (maximum concentration of 42 nmol cm3 of sediment-1). DMS concentrations in the surface layer doubled after cold hydrolysis of its precursor, dimethylsulfoniopropionate. Most-probable-number counts revealed 2.2 x 10(5) cells cm3 of sediment-1, in the 0- to 5-mm depth horizon, capable of growth on DMS as the sole source of energy. An obligately chemolithoautotrophic bacillus designated strain T5 was isolated from the top layer of the marine sediment. Continuous culture studies in which DMS was the growth-limiting substrate revealed a maximum specific growth rate of 0.10 h-1 and a saturation constant of 90 mumol liter-1 for aerobic growth on this substrate. 相似文献
86.
Can three incongruence tests predict when data should be combined? 总被引:31,自引:14,他引:17
Advocates of conditional combination have argued that testing for
incongruence between data partitions is an important step in data
exploration. Unless the partitions have had distinct histories, as in
horizontal gene transfer, incongruence means that one or more data support
the wrong phylogeny. This study examines the relationship between
incongruence and phylogenetic accuracy using three tests of incongruence.
These tests were applied to pairs of mitochondrial DNA data partitions from
two well-corroborated vertebrate phylogenies. Of the three tests, the most
useful was the incongruence length difference test (ILD, also called the
partition homogeneity test). This test distinguished between cases in which
combining the data generally improved phylogenetic accuracy (P > 0.01)
and cases in which accuracy of the combined data suffered relative to the
individual partitions (P < 0.001). In contrast, in several cases, the
Templeton and Rodrigo tests detected highly significant incongruence (P
< 0.001) even though combining the incongruent partitions actually
increased phylogenetic accuracy. All three tests identified cases in which
improving the reconstruction model would improve the phylogenetic accuracy
of the individual partitions.
相似文献
87.
Comparison of Immunization Methods for Producing Reference Adenovirus Antisera in Horses 总被引:5,自引:0,他引:5
John C. Hierholzer William C. Gamble Kenneth D. Quist W. Adrian Chappell 《Applied microbiology》1972,24(3):398-404
Horses were immunized by a variety of inoculation procedures designed to determine the most efficient method of producing antisera to adenovirus types 25 to 31. The procedures evaluated included immunization by (i) direct intravenous (iv) injection, (ii) iv infusion, (iii) intramuscular (im) injection of virus with and without Freund's incomplete adjuvant, (iv) combined iv and im injections, and (v) combined iv infusion and im injection. The im schedule (no. 3) was superior to the others in terms of immunizing antigen and time required, and hemagglutination-inhibition (HI) and serum-neutralizing (SN) antibody levels produced. HI and SN tests performed with sera before and after heating at 56 C for 30 min showed that heat-inactivation was not necessary for tests with equine antisera. 相似文献
88.
Organisms use circadian clocks to generate 24‐h rhythms in gene expression. However, the clock can interact with other pathways to generate shorter period oscillations. It remains unclear how these different frequencies are generated. Here, we examine this problem by studying the coupling of the clock to the alternative sigma factor sigC in the cyanobacterium Synechococcus elongatus. Using single‐cell microscopy, we find that psbAI, a key photosynthesis gene regulated by both sigC and the clock, is activated with two peaks of gene expression every circadian cycle under constant low light. This two‐peak oscillation is dependent on sigC, without which psbAI rhythms revert to one oscillatory peak per day. We also observe two circadian peaks of elongation rate, which are dependent on sigC, suggesting a role for the frequency doubling in modulating growth. We propose that the two‐peak rhythm in psbAI expression is generated by an incoherent feedforward loop between the clock, sigC and psbAI. Modelling and experiments suggest that this could be a general network motif to allow frequency doubling of outputs. 相似文献
89.
Acute sarcocystosis was diagnosed in an adult female wild turkey (Meleagris gallopavo) that was collected from Early County (Georgia, USA) in February of 1998. Marked inflammatory lesions were seen in the heart, lung, and liver and were associated with protozoal schizonts and merozoites. The organisms were identified as Sarcocystis sp. (Acomplexa: Sarcocystidae) based on structure and antigenicity. Protozoa divided by endopolygeny, merozoites lacked rhoptries, and the organisms did not react to anti-S. falcatula antibodies but reacted to anti-S. cruzi antibodies. 相似文献
90.
Nanotoxicity: the growing need for in vivo study 总被引:1,自引:0,他引:1