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951.
Frederico M. Batista Alexandra Leitão Vera G. Fonseca Radhouan Ben-Hamadou Maria A. Henriques Pierre Boudry 《Journal of experimental marine biology and ecology》2007,352(1):226-233
The Portuguese oyster, Crassostrea angulata, is taxonomically close to the Pacific oyster, C. gigas, but there are clear genetic and phenotypic differences between these taxa. Among those differences, the faster growth of C. gigas compared with C. angulata has often been observed in the field. Crosses between C. angulata and C. gigas were performed to investigate the relationship between growth variation and somatic aneuploidy at the individual level in the two taxa and their reciprocal hybrids. The different progenies were reared in Ria Formosa (Portugal) under standard farming conditions. Growth rate and survival were significantly higher in C. gigas than in C. angulata, and the hybrids showed intermediate performances. Significant differences were also observed in the proportion of aneuploid cells (PAC) and of missing chromosomes (PMC) between the two taxa, C. angulata showing the highest values. Intermediate values of PAC and PMC were observed in the hybrids, supporting additive genetic bases of these parameters. Our results also confirm the negative correlation between somatic aneuploidy and growth rate at the individual level, as previously reported in C. gigas. 相似文献
952.
Glomski IJ Corre JP Mock M Goossens PL 《Journal of immunology (Baltimore, Md. : 1950)》2007,178(5):2646-2650
Virulent strains of Bacillus anthracis produce immunomodulating toxins and an antiphagocytic capsule. The toxin component-protective Ag is a key target of the antianthrax immune response that induces production of toxin-neutralizing Abs. Coimmunization with spores enhances the antitoxin vaccine, and inactivated spores alone confer measurable protection. We aimed to identify the mechanisms of protection induced in inactivated-spore immunized mice that function independently of the toxin/antitoxin vaccine system. This goal was addressed with humoral and CD4 T lymphocyte transfer, in vivo depletion of CD4 T lymphocytes and IFN-gamma, and Ab-deficient (muMT(-/-)) or IFN-gamma-insensitive (IFN-gammaR(-/-)) mice. We found that humoral immunity did not protect from nontoxinogenic capsulated bacteria, whereas a cellular immune response by IFN-gamma-producing CD4 T lymphocytes protected mice. These results are the first evidence of protective cellular immunity against capsulated B. anthracis and suggest that future antianthrax vaccines should strive to augment cellular adaptive immunity. 相似文献
953.
Suppression of viral gene expression in bovine leukemia virus-associated B-cell malignancy: interplay of epigenetic modifications leading to chromatin with a repressive histone code 总被引:1,自引:0,他引:1
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Merimi M Klener P Szynal M Cleuter Y Kerkhofs P Burny A Martiat P Van den Broeke A 《Journal of virology》2007,81(11):5929-5939
954.
Binding-site identification and genotypic profiling of hepatitis C virus polymerase inhibitors 总被引:2,自引:0,他引:2
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Pauwels F Mostmans W Quirynen LM van der Helm L Boutton CW Rueff AS Cleiren E Raboisson P Surleraux D Nyanguile O Simmen KA 《Journal of virology》2007,81(13):6909-6919
The search for hepatitis C virus polymerase inhibitors has resulted in the identification of several nonnucleoside binding pockets. The shape and nature of these binding sites differ across and even within diverse hepatitis C virus genotypes. These differences confront antiviral drug discovery with the challenge of finding compounds that are capable of inhibition in variable binding pockets. To address this, we have established a hepatitis C virus mutant and genotypic recombinant polymerase panel as a means of guiding medicinal chemistry through the elucidation of the site of action of novel inhibitors and profiling against genotypes. Using a genotype 1b backbone, we demonstrate that the recombinant P495L, M423T, M414T, and S282T mutant enzymes can be used to identify the binding site of an acyl pyrrolidine analog. We assess the inhibitory activity of this analog and other nonnucleoside inhibitors with our panel of enzyme isolates generated from clinical sera representing genotypes 1a, 1b, 2a, 2b, 3a, 4a, 5a, and 6a. 相似文献
955.
Mittra ES Smith HF Lemelin P Jungers WL 《American journal of physical anthropology》2007,134(4):449-459
The relationship between the structure and function of the primate apical tuft is poorly understood. This study addresses several hypotheses about apical tuft morphology using a large modern primate comparative sample. Two indices of tuft size are employed: expansion and robusticity. First, comparisons of relative apical tuft size were drawn among extant nonhuman primate groups in terms of locomotion and phylogenetic category. Both of these factors appear to play a role in apical tuft size among nonhuman primates. Suspensory primates and all platyrrhines had the smallest apical tufts, while terrestrial quadrupeds and all strepsirrhines (regardless of locomotor category) had the largest tufts. Similarly, hypotheses regarding the apical tufts of hominins, especially the large tufts of Neandertals were addressed using a comparison of modern warm- and cold-adapted humans. The results showed that cold-adapted populations possessed smaller apical tufts than did warm-adapted groups. Therefore, the cold-adaptation hypothesis for Neandertal distal phalangeal morphology is not supported. Also, early modern and Early Upper Paleolithic humans had apical tufts that were significantly less expanded and less robust than those of Neandertals. The hypothesis that a large apical tuft serves as support for an expanded digital pulp is supported by radiographic analysis of modern humans in that a significant correlation was discovered between the width of the apical tuft and the width of the pulp. The implications of these findings for hypotheses about the association of apical tuft size and tool making in the hominin fossil record are discussed. 相似文献
956.
957.
Lee MK Pardoux C Hall MC Lee PS Warburton D Qing J Smith SM Derynck R 《The EMBO journal》2007,26(17):3957-3967
Erk1/Erk2 MAP kinases are key regulators of cell behaviour and their activation is generally associated with tyrosine kinase signalling. However, TGF-beta stimulation also activates Erk MAP kinases through an undefined mechanism, albeit to a much lower level than receptor tyrosine kinase stimulation. We report that upon TGF-beta stimulation, the activated TGF-beta type I receptor (TbetaRI) recruits and directly phosphorylates ShcA proteins on tyrosine and serine. This dual phosphorylation results from an intrinsic TbetaRI tyrosine kinase activity that complements its well-defined serine-threonine kinase function. TGF-beta-induced ShcA phosphorylation induces ShcA association with Grb2 and Sos, thereby initiating the well-characterised pathway linking receptor tyrosine kinases with Erk MAP kinases. We also found that TbetaRI is tyrosine phosphorylated in response to TGF-beta. Thus, TbetaRI, like the TGF-beta type II receptor, is a dual-specificity kinase. Recruitment of tyrosine kinase signalling pathways may account for aspects of TGF-beta biology that are independent of Smad signalling. 相似文献
958.
959.
Sexual selection theory has primarily focussed on the role of mating preferences for the best individuals in the evolution
of condition-dependent ornaments, traits that signal absolute quality. Because the most suitable mate for one individual is
not always the best for others, however, we argue that non-directional mate choice can promote the evolution of alternative
morphs that are not condition-dependent in their expression (i.e. genetic polymorphism). We list the different mate-choice
rules (i.e. all individuals have the same preference; preference depends on the chooser’s morph; individuals mate preferentially
with conspecifics displaying an uncommon or the most frequent morph) and review experimental studies that investigated mate
choice in natural populations of colour-polymorphic animals. Our review emphasises that although the experimental data support
the idea that sexual selection plays an important role in the evolution of genetic colour polymorphism in many different ways,
little is known about the adaptive value of each mate-choice strategy and about their implication in the evolutionary stability
of colour polymorphism. One way of solving this problem is to determine the adaptive function of colour morphs, a worthwhile
objective, because better understanding of mate-choice rules in polymorphic species should provide important insights into
sexual-selection processes and, in turn, into the maintenance of genetic variation. 相似文献
960.
Massip L Ectors F Deprez P Maleki M Behets C Lengelé B Delahaut P Picard J Rezsöhazy R 《Differentiation; research in biological diversity》2007,75(3):256-267
Vertebrate Hox genes act as developmental architects by patterning embryonic structures like axial skeletal elements, limbs, brainstem territories, or neural crest derivatives. While active during the patterning steps of development, these genes turn out to be down-regulated in specific differentiation programs like that leading to chondrogenesis. To investigate why chondrocyte differentiation is correlated to the silencing of a Hox gene, we generated transgenic mice allowing Cre-mediated conditional misexpression of Hoxa2 and induced this gene in Collagen 2 alpha 1-expressing cells committed to enter chondrogenesis. Persistent Hoxa2 expression in chondrogenic cells resulted in overall chondrodysplasia with delayed cartilage hypertrophy, mineralization, and ossification but without proliferation defects. The absence of skeletal patterning anomaly and the regular migration of precursor cells indicated that the condensation step of chondrogenesis was normal. In contrast, closer examination at the differentiation step showed severely impaired chondrocyte differentiation. In addition, this inhibition affected structures independently of their embryonic origin. In conclusion, for the first time here, by a cell-type specific misexpression, we precisely uncoupled the patterning function of Hoxa2 from its involvement in regulating differentiation programs per se and demonstrate that Hoxa2 displays an anti-chondrogenic activity that is distinct from its patterning function. 相似文献