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291.
Multiple mechanisms of immune evasion can coexist in melanoma tumor cell lines derived from the same patient 总被引:2,自引:0,他引:2
Real LM Jimenez P Kirkin A Serrano A García A Cantón J Zeuthen J Garrido F Ruiz-Cabello F 《Cancer immunology, immunotherapy : CII》2001,49(11):621-628
Progressive tumor growth may be associated with suppression of the immune response. Many different mechanisms may contribute
to immune evasion. We investigated some of these mechanisms in melanoma cells lines generated from two patients. These cell
lines show a complex pattern of altered HLA expression; however, the resulting phenotype did not satisfactorily explain the
simultaneous evasion of T and NK cell cytotoxicity. Two additional alterations have now been detected in these melanoma cell
lines: (1) resistance to FAS-induced apoptosis caused by defective FAS gene expression, and (2) constitutive expression of
immunosuppressive cytokines. Our results show that several of the major mechanisms for immune evasion may coexist in a single
tumor. This suggests that tumor progression may give rise to an extremely resistant phenotype, which may be an impediment
to some immunotherapeutic strategies. We hypothesize that the simultaneous presence of several mechanisms involved in tumor
immune evasion must be the result of progressive selection of characteristics that are advantageous for tumor survival in
a competent host. Our findings do not support the possibility that FASL expression is a common mechanism of evasion of immune
response in melanoma cells.
Received: 27 January 2000 / Accepted: 28 August 2000 相似文献
292.
293.
Wave-like spread of Ebola Zaire 总被引:1,自引:1,他引:0
In the past decade the Zaire strain of Ebola virus (ZEBOV) has emerged repeatedly into human populations in central Africa and caused massive die-offs of gorillas and chimpanzees. We tested the view that emergence events are independent and caused by ZEBOV variants that have been long resident at each locality. Phylogenetic analyses place the earliest known outbreak at Yambuku, Democratic Republic of Congo, very near to the root of the ZEBOV tree, suggesting that viruses causing all other known outbreaks evolved from a Yambuku-like virus after 1976. The tendency for earlier outbreaks to be directly ancestral to later outbreaks suggests that outbreaks are epidemiologically linked and may have occurred at the front of an advancing wave. While the ladder-like phylogenetic structure could also bear the signature of positive selection, our statistical power is too weak to reach a conclusion in this regard. Distances among outbreaks indicate a spread rate of about 50 km per year that remains consistent across spatial scales. Viral evolution is clocklike, and sequences show a high level of small-scale spatial structure. Genetic similarity decays with distance at roughly the same rate at all spatial scales. Our analyses suggest that ZEBOV has recently spread across the region rather than being long persistent at each outbreak locality. Controlling the impact of Ebola on wild apes and human populations may be more feasible than previously recognized. 相似文献
294.
Rausell C De Decker N García-Robles I Escriche B Van Kerkhove E Real MD Martínez-Ramírez AC 《Journal of invertebrate pathology》2000,75(4):288-291
Three steps of the proposed mode of action of Bacillus thuringiensis toxins have been studied in Lymantria monacha. We demonstrated that only the toxins that caused typical pathological changes in midgut epithelial cells and bound to the midgut brush border membrane were able to drastically reduce the midgut transepithelial voltage of the nun moth. 相似文献
295.
Improved genetic markers for monitoring recruitment dynamics in the endangered Mary River cod (Maccullochella mariensis)
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D. J. Schmidt T. Espinoza K. Real A. Dunlop M. Kennard J. M. Hughes 《Zeitschrift fur angewandte Ichthyologie》2018,34(3):633-637
The Mary River cod (Maccullochella mariensis) is a large predatory freshwater fish identified as a potential flagship for freshwater ecosystem conservation in Australia. The species is endemic to the Mary River catchment in eastern Australia, and is listed as Endangered. Previous conservation genetic assessment of Mary River cod was based on a small set of microsatellite loci developed for congeneric Maccullochella species. Here we develop a novel set of 15 microsatellite loci specific to M. mariensis, and demonstrate that these markers exhibit higher variability than those used previously. Mean number of alleles per locus was 4 and mean expected heterozygosity was 0.57. We genotyped 35 Mary River cod larvae belonging to a single cohort using the 15 novel loci and eight previously used loci, and found 10 full‐sib family groups along with clear genetic differentiation between individuals collected from the two sub‐catchments – Tinana Creek and Mary River. Microsatellites presented here will be useful for cost‐effective monitoring of genetic diversity and recruitment dynamics in this endangered fish species. 相似文献
296.
Francisco Javier Martínez Peromingo Carlos Oñoro Algar M. Elena Baeza Monedero Cristina González de Villaumbrosia Diego Real de Asua Cruzat Raquel Barba Martín 《Revista espa?ola de geriatría y gerontología》2018,53(3):149-154
Age is one of the main risk factors for the development of cancer. It is expected that the progressive aging of the population will have an unprecedented impact on the incidence of various tumours. In fact, the management of elderly cancer patients is already a major public health problem in developed countries. However, elderly patients have systematically been excluded from cancer drug studies or protocol development. This has left health professionals in uncharted territory, without proper tools to address the multiple difficulties that arise in the treatment of these patients. A comprehensive geriatric assessment may serve as an ideal tool for the correct detection of hidden problems, facilitating treatment decisions in these complex patients, and integrating the care of patients with comorbidities. 相似文献
297.
Cross-hybridizing snake satellite, Drosophila, and mouse DNA sequences may have arisen independently 总被引:2,自引:0,他引:2
Previous reports have interpreted hybridization between snake satellite DNA
and DNA clones from a variety of distant taxonomic groups as evidence for
evolutionary conservation, which implies common ancestry (homology) and/or
convergence (analogy) to produce the cross- hybridizing sequences. We have
isolated 11 clones from a genomic library of Drosophila melanogaster, using
a cloned 2.5-kb snake satellite probe of known nucleotide sequence. We have
also analysed published sequence data from snakes, mice, and Drosophila.
These data show that (1) all of the cross-hybridization between the snake,
fly, and mouse clones can be accounted for by the presence of either of two
tandem repeats, [GATA]n and [GACA]n and (2) these tandem repeats are
organized differently among the different species. We find no evidence that
these sequences are homologous apart from the existence of the simple
repeat itself, although their divergence from a common ancestral sequence
cannot be ruled out. The sequences contain a variety of homogeneous
clusters of tandem repeats of CATA, GA, TA, and CA, as well as GATA and
GACA. We suggest that these motifs may have arisen by a self-accelerating
process involving slipped-strand mispairing of DNA. Homogeneity of the
clusters might simply be the result of a rate of accumulation of tandem
repeats that exceeds that of other mutations.
相似文献
298.
Oligochaeta assemblages from Lake Banyoles were composed of one species of Naididae and eight species of Tubificidae, Potamothrix heuscheri (8–1350 ind. m–2) being the most abundant and widely distributed species, followed by Limnodrilus hoffmeisteri (25–858 ind. m–2) and Psammoryctides barbatus (12–792 ind. m–2). The remaining species were Potamothrix hammoniensis, Potamothrix bavaricus, Limnodrilus claparedeanus, Branchiura sowerbyi, Aulodrilus pigueti and Dero digitata, all of which occurred at lower densities and with restricted distributions.Regardless of sampling depth, maximum densities of oligochaetes were found in winter (up to 5,142 ind. m–2 in December) and secondarily in June. Immature Tubificidae with hair setae and mature P. heuscheri were present and dominant throughout the year. Cestode parasites were recorded infesting L. hoffmeisteri and P. heuscheri populations.Oligochaeta densities increased with depth, but low oxygen concentrations (less than 1 mg l–1) during a long period (4 months) in some basins of the lake acted as a key factor in reducing the density of worms and the species richness to one species, Potamothrix heuscheri. 相似文献
299.
Structural comparison of fibroblast growth factor-specific heparan sulfates derived from a growing or differentiating neuroepithelial cell line 总被引:3,自引:1,他引:2
Brickman YG; Nurcombe V; Ford MD; Gallagher JT; Bartlett PF; Turnbull JE 《Glycobiology》1998,8(5):463-471
Heparan sulfate (HS) glycosaminoglycans are essential modulators of
fibroblast growth factor (FGF) activity both in vivo and in vitro, and
appear to act by cross-linking particular forms of FGF to appropriate FGF
receptors. We have recently isolated and characterized two separate HS
pools derived from immortalized embryonic day 10 mouse neuroepithelial 2.3D
cells: one from cells in log growth phase, which greatly potentiates the
activity of FGF-2, and the other from cells undergoing contact-inhibition
and differentiation, which preferentially activates FGF-1. These two pools
of HS have very similar functional activities to those species isolated
from primary neuroepithelial cells at corresponding stages of active
proliferation or differentiation. We present here a structural comparison
between these cell line HS species to establish the nature of the changes
that occur in the biosynthesis of HS. A combination of chemical and
enzymatic cleavage, low pressure chromatography and strong anion-exchange
HPLC were used to generate full chain models of each species. Overall, the
HS pools synthesized in the dividing cell line pools possessed less complex
sulfation than those derived from more differentiated, growth arrested
cells.
相似文献
300.
Giovanni De Munno Miguel Julve Jos Antonio Real Francesc Lloret Rosario Scopelliti 《Inorganica chimica acta》1996,250(1-2):81-85
The iron(II) compound of formula [Fe(bpym)(NCS)2]n (bpym = 2,2′-bipyrimidine) has been synthesized and its crystal structure determined by X-ray diffraction methods. It crystallizes in the tetragonal P41 (No. 76) and P43 space groups, a = 8.849(2), C=16.486(3) Å, V=1290.9(5) Å3, Z=4, Dc=1.699 g cm−3, Mr=330.2, F(000)=664, λ(Mo K)=0.71073 Å, μ(Mo K)=14.8 cm−1 and T=295 K. A total of 2449 reflections was collected over the range 3≤2≤55°; of these, 1657 were unique and 1321 were considered as observed (13σ(I)) and used in the structural analysis. The final R and Rw residuals were 0.027 and 0.026, respectively. The structure is made up of chiral (Δ and Λ enantiomers crystallize in the same crop) chains of iron(II) atoms bridged by bis-chelating bpym, the electroneutrality being achieved by N-bonded thiocyanato groups in cis position. Each metal atom is in a distorted FeN6 octahedral environment, the Fe---N bonds ranging from 2.265(3) to 2.028(4)
. The intrachain metal-metal separation is 5.960(1) Å. Variable-temperature magnetic susceptibility data in the temperatyre range 290–4.2 K show that the iron(II) is high-spin and interacts in an antiferromagnetic fashion, the relevant parameters being . The magnitude of the exchange coupling compares well with that reported for other structurally characterized bpym-bridged iron(II) complexes. 相似文献