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81.
The somatic and oral cortical ultrastructure of the plagiopylid ciliates Lechriopyla mystax Lynch, 1930 and Plagiopyla minuta Powers, 1933 are described. The somatic kinetids are monokinetids with an anteriorly directed kinetodesmal fibril originating near triplets 5, 6, 7, a divergent postciliary ribbon originating at triplet 9, and an unusual transverse ribbon originating in dense material adjacent to triplets 1, 2, 3. The transverse ribbon extends beneath the right surface of the cortical ridge adjacent to the kinety from which it originated. The oral kinetids are also monokinetids from whose base rootlet fibrils extend inwards beneath the oral kineties and converge on the furcula. The striated band on these ciliates is composed of a series of short ridges orthogonal to the longitudinal axis of the band. The sides of the striated band groove are apparently supported by macrotubules. The cortical ultrastructure of the plagiopylids is discussed with reference both to the optical microscopy of the organisms and to the ultrastructure of other ciliate taxa. The plagiopylids are not clearly related to any other higher taxon and are placed incertae sedis in the Subphylum Cyrtophora Small, 1976. 相似文献
82.
MARIANNE J. VAN DIJKEN PETER NEUENSCHWANDER JACQUES J. M. VAN ALPHEN WINFRED N. O. HAMMOND 《Ecological Entomology》1991,16(2):233-240
Abstract.
- 1 In cassava fields in Africa, population sex ratios of Epidinocarsis fopezi vaned from 0.44 (males to total parasitoids) at low host densities to highly male-biased ratios of 0.70 at high host densities.
- 2 This variability is caused by the difference in allocation of sons and daughters to hosts of different sizes, through the following mechanisms: (a) small, i.e. second instar, hosts are mainly used for the production of male offspring, whereas in large, i.e. third instar, hosts a variable, female-biased sex ratio is produced; (b) E.fopezi does not selectively oviposit into large hosts but always accepts both small and large hosts for oviposition upon encountering; (c) in the field, this parasitoid is time-limited, and not egg-limited. On the basis of an optimal diet model, such general host acceptance is shown to be the best strategy.
- 3 Thus, sex ratio increases with host density for three reasons: the proportion of small hosts encountered in the field increases with increasing host density, small hosts are used for male production, and hosts are always accepted when encountered.
83.
THIERRY OBERDORFF BERNARD HUGUENY ARTHUR COMPIN & DJAMILA BELKESSAM 《The Journal of animal ecology》1998,67(3):472-484
1. Spatial patterns of freshwater fish species at regional and local scales were investigated to explore the possible role of interspecific interactions in influencing distribution and abundance within communities occupying coastal streams of North-Western France.
2. Nine sites from nine streams situated in the same biogeographical region were sampled annually over the 6-year period from 1990 to 1995.
3. Similar habitats (sites) with richer regional colonization pools exhibited proportionally richer local communities in terms of number of species, total density and total biomass of individuals. Furthermore, no negative relationships were found between density and biomass of each of the most common species and local species richness.
4. Results of dynamic regression models (applied to the above-mentioned species) suggest an absence of strong competition between all pairs of species.
5. The evidence on lack of density compensation for species-poor communities and absence of perceptible interspecific competition between species suggest that the communities studied are non-interactive.
6. Two main explanations can be advanced. First, the local abundance of species in the communities studied could be determined through differential responses to unpredictable environmental changes, rather than through biological interactions. Second, as a result of historical events, the communities studied are reduced in congeneric species which can limit, in turn, the influence of interspecific competition in structuring these communities.
7. These results underline the strong influence of regional processes in shaping local riverine fish communities and minimize the possible influence of species interactions in governing these communities. 相似文献
2. Nine sites from nine streams situated in the same biogeographical region were sampled annually over the 6-year period from 1990 to 1995.
3. Similar habitats (sites) with richer regional colonization pools exhibited proportionally richer local communities in terms of number of species, total density and total biomass of individuals. Furthermore, no negative relationships were found between density and biomass of each of the most common species and local species richness.
4. Results of dynamic regression models (applied to the above-mentioned species) suggest an absence of strong competition between all pairs of species.
5. The evidence on lack of density compensation for species-poor communities and absence of perceptible interspecific competition between species suggest that the communities studied are non-interactive.
6. Two main explanations can be advanced. First, the local abundance of species in the communities studied could be determined through differential responses to unpredictable environmental changes, rather than through biological interactions. Second, as a result of historical events, the communities studied are reduced in congeneric species which can limit, in turn, the influence of interspecific competition in structuring these communities.
7. These results underline the strong influence of regional processes in shaping local riverine fish communities and minimize the possible influence of species interactions in governing these communities. 相似文献
84.
85.
DAVID M. GOLDENBERG ROSE A. PAVIA HANS J. HANSEN JACQUES P. VANDEVOORDE 《Nature: New biology》1972,239(93):189-190
NORMAL and neoplastic mammalian cells cultivated in vitro retain a number of functions that characterize their cellular origin, even after extensive passage1. It therefore seems reasonable to expect that cell products such as tumour-associated antigens could, if present from the outset, be retained in a demonstrable state when the tumour cells are cultivated outside the original host organism. The discovery by Gold and Freedman2 of an antigenic substance specific for entodermally-derived cancers of the digestive system, carcinoembryonic antigen (CEA), provides a suitable candidate for studying one such property related to a particular type of human cancer. It has been proposed, however, that tumour-specific antigens such as CEA are not indigenous to the tumours, but are glycoproteins produced elsewhere in the body and coating the tumour cells secondarily3. If this were the case, then human colonic cancer cells in long-term propagation in vitro should not synthesize this material. We now present evidence to the contrary. 相似文献
86.
Observations on Idiotypy of Rabbit Antibodies against <Emphasis Type="Italic">Salmonella abortus-equi</Emphasis> 总被引:4,自引:0,他引:4
IDIOTYPIC specificities are antigenic specificities each of which seems to be peculiar to antibodies of one given individual (or perhaps of one group of individuals) against one given antigen1,2. They are detected by reactions—usually of specific precipitation-using anti-idiotypic sera3. We have used anti-Salmonella abortus-equi (SAE) sera of two rabbits to agglutinate bacteria which were injected into two series of six rabbits; three rabbits of each series gave precipitating anti-idiotypic sera. 相似文献
87.
JEAN-FRANÇOIS RIOU DE-LI SHI THIERRY DARRIBÈRE JEAN-CLAUDE BOUCAUT JACQUES CHARLEMAGNE 《Development, growth & differentiation》1987,29(5):443-454
We have previously reported the identification of cell surface glycoproteins in Pleurodeles waltlii gastrulae. In an attempt to study the expression of three of these cell surface glycoproteins (proteins referred to 1, 11 and 14), we have produced monoclonal and polyclonal antibodies by immunizing mice with the spots of the three selected glycoproteins excised from 2D-gels. Expression of the three glycoproteins was detected on the surfaces of all cells during embryonic development. Before hatching, proteins 1, 11 and 14 become expressed in a limited number of tissues. 相似文献
88.
Abstract. An acid phosphatase is isolated and purified to homogeneity from sycamore cell walls. The enzyme, which has a molecular weight close to 100,000, is a glycoprotein and is most probably made up of one polypeptide chain only. Its amino acid composition has been determined. Although homogeneous to polyacrylamide gel electrophoresis under non-denaturing conditions, the enzyme preparation still contains protease traces that tend to split polypeptide chain in two fragments. 相似文献
89.
JEAN GRUENBERG BERNARD SCHWENDIMANN PUKH RAJ SHARMA JACQUES DESHUSSES 《The Journal of eukaryotic microbiology》1980,27(4):484-491
SYNOPSIS. Under aerobic conditions, we have determined glycerol uptake in the long slender (LS) bloodstream form of Trypanosoma (Trypanozoon) brucei brucei by studying glycerophosphate accumulation in the parasites. The coupled enzyme theory applies to the permeation-phosphorylation sequence. Glycerol passage through the plasma membrane is asymmetric, the efflux process being favored over the influx process. No free diffusion of glycerol can be detected even under conditions under which free glycerol accumulates within the cells; most probably, glycerol permeation is mediated by a specific transport system. In the absence of respiratory activities, glycerol is known to be an end-product of T. brucei glycolysis; its production from glycerophosphate should allow ATP synthesis. The observed efflux of free glycerol following intracellular accumulation of glycerophosphate confirms the hypothesis that glycerol production occurs through reversal of glycerol kinase activity. We conclude that in vivo the role of the carrier-mediated asymmetric permeation process is to prevent inhibition of the reversal of the glycerol kinase-mediated reaction by removing free glycerol. 相似文献
90.
THIERRY BACKELJAU ANTON J. DE WINTER RAMON MARTIN TERESA RODRIGUEZ LUC DE BRUYN 《Zoological Journal of the Linnean Society》1994,110(1):1-18
A comparison of the genital features of Arion urbiae and A. anguloi suggests that the species are extremely similar, if not identical. This hypothesis is supported by an electrophoretic analysis of 13 putative enzynme loci, which shows that the two species are also genetically yery similar (I = 0.947), while the related A. subfuscus consists of two distinct genetic types (I = 0.421). These results are further confirmed by a study of esterase profiles obtained with isoelectric focusing. It is therefore concluded that A. urbiae and A. anguloi are most probably conspecifie, whereas the genetic types of A. subfuscus may represent two different species. 相似文献