全文获取类型
收费全文 | 156篇 |
免费 | 6篇 |
出版年
2021年 | 1篇 |
2020年 | 2篇 |
2019年 | 3篇 |
2018年 | 1篇 |
2017年 | 5篇 |
2016年 | 4篇 |
2015年 | 4篇 |
2014年 | 5篇 |
2013年 | 11篇 |
2012年 | 4篇 |
2011年 | 5篇 |
2010年 | 8篇 |
2009年 | 6篇 |
2008年 | 5篇 |
2007年 | 5篇 |
2006年 | 8篇 |
2005年 | 4篇 |
2004年 | 4篇 |
2003年 | 6篇 |
2002年 | 4篇 |
2001年 | 5篇 |
2000年 | 7篇 |
1999年 | 2篇 |
1998年 | 9篇 |
1997年 | 1篇 |
1996年 | 2篇 |
1994年 | 1篇 |
1992年 | 3篇 |
1991年 | 3篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 3篇 |
1983年 | 2篇 |
1982年 | 2篇 |
1981年 | 6篇 |
1980年 | 3篇 |
1979年 | 3篇 |
1977年 | 2篇 |
1975年 | 2篇 |
1973年 | 2篇 |
1972年 | 1篇 |
排序方式: 共有162条查询结果,搜索用时 15 毫秒
51.
FMRFamide immunoreactivity is generally occurring in the nervous systems of coelenterates 总被引:4,自引:0,他引:4
C J Grimmelikhuijzen 《Histochemistry》1983,78(3):361-381
Abundant FMRFamide immunoreactivity has been found in the nervous systems of all hydrozoan, anthozoan, scyphozoan and ctenophoran species that were looked upon. This general and abundant occurrence shows that FMRFamide-like material must play a crucial role in the functioning of primitive nervous systems. 相似文献
52.
A covariotide model explains apparent phylogenetic structure of oxygenic photosynthetic lineages 总被引:17,自引:13,他引:4
Lockhart PJ; Steel MA; Barbrook AC; Huson DH; Charleston MA; Howe CJ 《Molecular biology and evolution》1998,15(9):1183-1188
The aims of the work were (1) to develop statistical tests to identify
whether substitution takes place under a covariotide model in sequences
used for phylogenetic inference and (2) to determine the influence of
covariotide substitution on phylogenetic trees inferred for photosynthetic
and other organisms. (Covariotide and covarion models are ones in which
sites that are variable in some parts of the underlying tree are invariable
in others and vice versa.) Two tests were developed. The first was a
contingency test, and the second was an inequality test comparing the
expected number of variable sites in two groups with the observed number.
Application of these tests to 16S rDNA and tufA sequences from a range of
nonphotosynthetic prokaryotes and oxygenic photosynthetic prokaryotes and
eukaryotes suggests the occurrence of a covariotide mechanism. The degree
of support for partitioning of taxa in reconstructed trees involving these
organisms was determined in the presence or absence of sites showing
particular substitution patterns. This analysis showed that the support for
splits between (1) photosynthetic eukaryotes and prokaryotes and (2)
photosynthetic and nonphotosynthetic organisms could be accounted for by
patterns arising from covariotide substitution. We show that the additional
problem of compositional bias in sequence data needs to be considered in
the context of patterns of covariotide/covarion substitution. We argue that
while covariotide or covarion substitution may give rise to
phylogenetically informative patterns in sequence data, this may not always
be so.
相似文献
53.
Grimmelikhuijzen C. J. P. Graff D. Koizumi O. Westfall J. A. McFarlane I. D. 《Hydrobiologia》1991,(1):555-563
Coelenterate neurones produce peptides containing an Arg-Phe-NH2(RF-amide)-like carboxyterminus. RF-amide-like peptides are located in neuronal dense-cored vesicles, indicating that they are released by exocytosis and that they might function as neurotransmitters or neurohormones. Using a radioimmunoassay for the sequence RF-amide, 3 peptides were isolated from the sea anemone Anthopleura elegantissima: < Glu-Gly-Arg-Phe-NH2(Antho-RF-amide), 2(Antho-RWamide I) and 2(Antho-RW-amide II). The general structure of these peptides can be described as 2, where X is an aromatic amino acid. From the hydromedusa Polyorchis penicillatus, the peptide 2(Pol-RF-amide I) was isolated, which also belongs to the 2 family. Using specific antisera, it was shown that all 4 peptides were located in neurones, many of which were associated with smooth muscle fibres. Application of low doses of Antho-RF-amide or of Antho-RW-amide I and II induced contractions of endodermal muscles of sea anemones. This suggests that these peptides are transmitters or modulators at neuromuscular junctions. 相似文献
54.
Ultrastructural localization of RFamide-like peptides in neuronal dense-cored vesicles in the peduncle of Hydra 总被引:2,自引:0,他引:2
O Koizumi J D Wilson C J Grimmelikhuijzen J A Westfall 《The Journal of experimental zoology》1989,249(1):17-22
The presence of Arg-Phe-amide (RFamide)-like peptides in dense-cored vesicles in neurons of the peduncle of Hydra was demonstrated by immunogold electron microscopy. Thin sections of Lowicryl-embedded tissue labeled with antisera to RFamide and 5-nm gold-conjugated, secondary antibody and of Epon-Araldite-embedded tissue labeled with 15-nm gold particles revealed a concentration of RFamide-like immunoreactivity over the granular cores of vesicles in epidermal ganglion cells. Gold-labeled, dense-cored vesicles were present in the perikaryon, long thin neurites, and axon terminals of these neurons. The aggregation of labeled dense-cored vesicles in an axon terminal on the myoneme of an epitheliomuscular cell suggests a possible function of RFamide-like peptides in neuromuscular transmission. Gold staining of dense-cored vesicles completely disappeared when the RFamide antiserum was preabsorbed with 10 micrograms/ml RFamide. These results are the first demonstration that the dense-cored vesicles of Hydra neurons contain a neuropeptide. 相似文献
55.
We have developed an assay for a substance from hydra that accelerates foot regeneration in the animal. This substance is specific for the foot as evidenced by the following findings: (1) It is present in the animal as a steep gradient descending from foot to head, paralleling the foot-forming potential of the tissue (2) It does not accelerate head regeneration, nor do the head factors of hydra discovered by Schaller (1973) and Berking (1977) accelerate foot regeneration. We propose that the foot-activating substance is a morphogen responsible for foot formation in hydra. The foot activator can be extracted from hydra tissue with methanol and separated from other known morphogens of hydra by gel filtration and ion-exchange chromatography. A substance with similar biological and physicochemical properties can be isolated from sea anemones. 相似文献
56.
J. Lepault A. W. McDowall Dr. C. J. P. Grimmelikhuijzen 《Cell and tissue research》1980,209(2):217-224
Summary Epithelial cells of nerve-free hydra contain septate and gap junctions. In thin sections the gap junctions are characterized by a gap of 3–4 nm. Freeze-fracture demonstrates the presence of septate junctions and two further types of structures: (i) the E-type or inverted gap junctions with particles in an en plaque conformation appearing as a raised plateau on the E-face or as a depression on the P-face; (ii) structures morphologically similar to gap junctions in rat liver, containing particles on the P-face and corresponding pits on the E-face, both having hexagonal packing with a lattice constant of 8 nm. We propose that these structures are also gap junctions. 相似文献
57.
H. Chica Schaller Tobias Schmidt Cok J. P. Grimmelikhuijzen 《Development genes and evolution》1979,186(2):139-149
Summary A procedure is presented by which four previously described morphogenetic substances can be purified from hydra: an activator and an inhibitor of head formation and an activator and an inhibitor of foot formation. We show that all four substances act specifically. At low concentrations, the head factors only influence head and not foot formation, and the foot factors only influence foot and not head formation. 相似文献
58.
C J Grimmelikhuijzen K L Rinehart A N Spencer 《Biochemical and biophysical research communications》1992,183(2):375-382
Using a radioimmunoassay for the sequence Arg-Phe-NH2 (RFamide), we have isolated the peptide less than Glu-Trp-Leu-Lys-Gly-Arg-Phe-NH2 (Pol-RFamide II) from acetic acid extracts of the hydromedusa Polyorchis penicillatus. This peptide is a neuropeptide and constitutes a peptide family together with less than Glu-Leu-Leu-Gly-Gly-Arg-Phe-NH2 (Pol-RFamide I), the first neuropeptide isolated from Polyorchis, and less than Glu-Gly-Arg-Phe-NH2 (Antho-RFamide), a neuropeptide isolated from sea anemones and sea pansies. 相似文献
59.
Using immunocytochemistry, gastrin/CCK-like immunoreactivity is found in sensory nerve cells in the ectoderm of the mouth region of hydra and in nerve cells in the endoderm of all body regions of the sea anemone tealia. These results are corroborated by radioimmunoassay: One hydra contains at least 5 fmole and one tealia at least 2 nmole gastrin/CCK-like immunoreactivity. Reactivities towards gastrin and CCK antisera with different specificities suggest that the coelenterate gastrin/CCK-like peptide contains the C-terminal amino-acid sequence common to mammalian gastrin and CCK. In addition the radioimmunochemical data indicate that the coelenterate peptide also contains an amino-acid sequence that resembles the sequence 20-30 of porcine CCK-33, but that no other sequences of gastrin are present. Thus, it is probably more CCK-like than gastrin-like. 相似文献
60.
Bombesin-like immunoreactivity in the nervous system of hydra 总被引:2,自引:0,他引:2
C. J. P. Grimmelikhuijzen G. J. Dockray N. Yanaihara 《Histochemistry and cell biology》1981,73(2):171-180
Summary With immunocytochemical methods, nerve cells have been detected in Hydra attenuata containing bombesin-like immunoreactivity. These nerve cells are located in the ectoderm of all body regions of the animal and are especially abundant in basal disk and tentacles. Radioimmunoassay of extracts of hydra demonstrated at least 0.2 pmol/g wet weight of bombesinlike immunoreactivity. The immunoreactive material elutes from Sephadex G-50 in a similar position to synthetic bombesin. The data show that bombesin-like peptides are among the phylogenetically oldest neuropeptides found so far. 相似文献