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1.
2.
Localization of the epidermal growth factor (EGF) receptor within the endosome of EGF-stimulated epidermoid carcinoma (A431) cells 总被引:13,自引:7,他引:6 下载免费PDF全文
K Miller J Beardmore H Kanety J Schlessinger C R Hopkins 《The Journal of cell biology》1986,102(2):500-509
We have followed the internalization pathway of both epidermal growth factor (EGF) and its receptor in human epidermoid carcinoma (A431) cells. Using EGF conjugated with horseradish peroxidase and anti-receptor monoclonal antibodies (TL5 and EGFR1) coupled either directly or indirectly to colloidal gold we have identified an extensive elaboration of endosomal compartments, consisting of a peripheral branching network of tubular cisternae connected to vacuolar elements that contain small vesicles and a pericentriolar compartment consisting of a tubular cisternal network connected to multivesicular bodies. Immunocytochemistry on frozen thin sections using receptor-specific antibody-gold revealed that at 4 degrees C in the presence of EGF, receptors were mainly on the plasma membrane and, to a lesser extent, within some elements of both the peripheral and pericentriolar endosomal compartments. Upon warming to 37 degrees C there was an EGF-dependent redistribution of most binding sites, first to the peripheral endosome compartment and then to the pericentriolar compartment and lysosomes. Upon warming only to 20 degrees C the ligand-receptor complex accumulated in the pericentriolar compartment. Acid phosphatase cytochemistry identifies hydrolytic activity only within secondary lysosomes and trans cisternae of the Golgi stacks. Together these observations suggest that the prelysosomal endosome compartment extends to the pericentriolar complex and that the transfer of EGF receptor complexes to the acid phosphatase-positive lysosome involves a discontinuous, temperature-dependent step. 相似文献
3.
MAJOR CLADES OF THE ANGIOSPERMS 总被引:2,自引:0,他引:2
ROLF DAHLGREN KÅRE BREMER 《Cladistics : the international journal of the Willi Hennig Society》1985,1(4):349-368
Abstract— Our knowledge of fundamental angiosperm interrelationships is still very incomplete. The absence of a narrowly circumscribed gymnosperm outgroup, ideally the sister group, makes character evaluation, necessary for a cladistic analysis, difficult. According to current views the superorder Magnoliiflorae with a number of other groups, for example the monocotyledons, may represent a complex of families near the base of the angiosperms. Interrelationships of groups within the monocotyledons are much better understood than those between groups within the dicotyledons. A cladogram of monocotyledon orders based on earlier work by R. Dahlgren, H. T. Clifford, and F. N. Rasmussen is presented. A data matrix for a sample of the angiosperms with 61 characters for 49 taxa, mostly magnoliifloran and related families, is presented. The characters are polarized mainly according to the current view that the primitive angiosperm morphotype is a woody dicotyledon with strobiloid flowers. As an alternative the matrix is adjusted following W. C. Burger's conjecture that the primitive angiosperm was a herbaceous monocotyledon with trimerous flowers. Both matrices were run in a computerized parsimony analysis, resulting in numerous equally parsimonious solutions. This result is illustrative of the great homoplasy in the available character information, and also of how little actually is known about fundamental angiosperm interrelationships or phylogeny. 相似文献
4.
An electrophoretic study of genetic variation at 31 loci was made in nine species of gobild fish. Rank order estimates of the degree of environmental heterogeneity experienced by each of the species examined were made and correlations between genetic variation (measured as \-He) and this rank order were calculated. The most conservative rank correlation coefficient is 0.88 (P<0.01). The large difference in values of He between estuarine/shore ( He=0.094) and neritic/offshore ( He=0.044) species seems unlikely to be accounted for by differences in parameters such as population size or mutation rate. We conclude that it is probable that more variable environments are conducive to the maintenance of higher levels of genetic variation at enzyme loci in these goby populations. These results parallel findings made in numerous comparisons of laboratory populations. 相似文献
5.
Assignment of orthologous relationships among mammalian alpha-globin genes by examining flanking regions reveals a rapid rate of evolution 总被引:1,自引:0,他引:1
In order to study the relationships among mammalian alpha-globin genes, we
have determined the sequence of the 3' flanking region of the human alpha 1
globin gene and have made pairwise comparisons between sequenced
alpha-globin genes. The flanking regions were examined in detail because
sequence matches in these regions could be interpreted with the least
complication from the gene duplications and conversions that have occurred
frequently in mammalian alpha-like globin gene clusters. We found good
matches between the flanking regions of human alpha 1 and rabbit alpha 1,
human psi alpha 1 and goat I alpha, human alpha 2 and goat II alpha, and
horse alpha 1 and goat II alpha. These matches were used to align the
alpha-globin genes in gene clusters from different mammals. This alignment
shows that genes at equivalent positions in the gene clusters of different
mammals can be functional or nonfunctional, depending on whether they
corrected against a functional alpha-globin gene in recent evolutionary
history. The number of alpha-globin genes (including pseudogenes) appears
to differ among species, although highly divergent pseudogenes may not have
been detected in all species examined. Although matching sequences could be
found in interspecies comparisons of the flanking regions of alpha- globin
genes, these matches are not as extensive as those found in the flanking
regions of mammalian beta-like globin genes. This observation suggests that
the noncoding sequences in the mammalian alpha-globin gene clusters are
evolving at a faster rate than those in the beta-like globin gene clusters.
The proposed faster rate of evolution fits with the poor conservation of
the genetic linkage map around alpha-globin gene clusters when compared to
that of the beta-like globin gene clusters. Analysis of the 3' flanking
regions of alpha-globin genes has revealed a conserved sequence
approximately 100-150 bp 3' to the polyadenylation site; this sequence may
be involved in the expression or regulation of alpha-globin genes.
相似文献
6.
INTRODUCTI0NThedifferentiati0nofcelIsalongthemonocyte-macr0phagepathwayandthesig-nalsinvo1vedinthesecel1sacquiringtheabilitytokilltum0rcellsarenotfllllyundersto0d.Wehavebeenstudingamoleculewhichappearst0beanimportantmemberofthecytokinenetworkinvo1vedintheregulati0nmonocyteactivation.ThiscytokinetermedP48wasisolatedfr0mthehllmannullcellleukemiacell1ineReh.IthasbeenpurifiedtohomogeneityandfOundtobedistinctfrominterferongamma,col0nystimulatingfactors(CSFs)andTNFalphaalldbeta[1,2].Func-ti… 相似文献
7.
Summary The susceptibility of cellulose to enzymatic hydrolysis can be significantly affected through pretreatment by means of gamma-ray radiation. Experiments were carried out to investigate the effects of this radiation on enzymatic hydrolysis and on the two major structural features of cellulose that most influence hydrolysis, namely, specific surface area and crystallinity.D. H. Beardmore is currently with Phillips Petroleum Company, Bartlesville, OK 74004, U.S.A. 相似文献
8.
Allozyme variation encoded for by 22 enzyme loci analyzed with starch-gel electrophoresis from samples of gonochoristic Artemia monica and A. urmiana collected from Lake Urmia, Iran and from Mono Lake, CA, USA, respectively, are compared and contrasted with data from representative gonochoristic populations of A. franciscana, A. persimilis and A. salina, as well as diploid, triploid, tetraploid, and pentaploid parthenogenetic forms. Values for parameters measuring degree of genetic variability (number of alleles per locus, proportion of polymorphic loci, and expected heterozygosity) in A. monica and A. urmiana were among the highest in the genus (1.76, 0.46, 0.19, and 2.19, 0.55, and 0.14, respectively). For A. monica, possible factors promoting its high genetic variability are discussed. Mean values for Nei's D between A. monica and A. franciscana were very low (0.09) and consistent with reported cytological and morphological similarities, thus the physiological differentiation which distinguishes the former must involve differences at very few loci. D values from A. urmiana to rest of the gonochoristic species (0.95) are consistent with its taxonomic status and distinctive morphology, while its low genetic distance to the monophyletic Artemia parthenogenetic lineage (mean D = 0.48) suggests a recent common ancestry. 相似文献
9.
Under natural conditions, plants are subjected to continuous changes of irradiance that drive variations of stomatal conductance to water vapour (gs). We propose a dynamic model to predict the temporal response of gs at the leaf level using an asymmetric sigmoid function with a unique parameter describing time constants for increasing and decreasing gs. The model parameters were adjusted to observed data using Approximate Bayesian Computation. We tested the model performance for (1) instant changes of irradiance; or (2) continuous and controlled variations of irradiance simulating diurnal time courses. Compared with the two mostly used steady‐state models, our dynamic model described daily time courses of gs with a higher accuracy. In particular, it was able to describe the hysteresis of gs responses to increasing/decreasing irradiance and the resulting rapid variations of intrinsic water‐use efficiency. Compared to the mechanistic model of temporal responses of gs by Kirschbaum, Gross & Pearcy, for which time constants were estimated with a large variance, our model estimated time constants with a higher precision. It is expected to improve predictions of water loss and water‐use efficiency in higher scale models by using a small number of parameters. 相似文献
10.
Many animal populations live in social groups which avoid contact with other conspecific groups for at least part of the year. This may give rise to competition between groups for items such as shelter, land and mates. We couple intra-specific group competition with disease dynamics to investigate how infectious diseases may spread through population subgroups, particularly with reference to the contact rates between groups. Our model uses a nonlinear systems of ODEs for which steady-state analysis is carried out in the simplest two-group system. This indicates that coexistence of social groups is possible with the disease or that competitive exclusion occurs with one group dying out whilst the other retains disease. Moreover, we show that in certain circumstances the model can exhibit multistability and we discuss the ecological implications of this result in relation to contact between social groups. 相似文献