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991.
Heteromorphisms between sex chromosomes are rarely found in anurans and sex chromosome differentiation is considered to be a set of recent recurrent events in the evolutionary history of this group. This paper describes for the first time heteromorphic sex chromosomes Z and W in the leiuperid genus Physalaemus. They were found in P. ephippifer, a species of the P. cuvieri group, and corresponded to the eighth pair of its karyotype. The W chromosome differed from the Z chromosome by the presence of an additional segment in the short arm, composed of a distal NOR and an adjacent terminal DAPI-positive C-band. The identification of this sex chromosome pair may help in future investigations into the sex determining genes in the genus Physalaemus. 相似文献
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993.
The objective of this work was to identify and further characterize potential changes in the functional profile of the cardiac
ryanodine receptor (RyR2) channel caused by the coupled gating phenomenon. By reconstituting an ion channel into a planar
lipid membrane, we showed that coupled RyR2 channels were activated by cytosolic Ca2+ with similar efficacy and potency as reported for the single RyR2 channel. In contrast, all examined parameters of gating
kinetics were affected by the functional interaction between channels. Ignoring brief closings during main open events, the
average open and closed times were considerably prolonged and the frequency of opening was reduced. Interestingly, when luminal
Ca2+ was used as a charge carrier, Ca2+-activated coupled RyR2 channels did not exhibit a sudden switch from slow to fast gating kinetics at an open probability
of 0.5 as reported for the single RyR2 channel. Regarding flicker gating, the average closed time was significantly shorter
and the frequency of closing was greatly enhanced. Furthermore, in contrast to the single RyR2 channel, both parameters for
coupled channels were independent of cytosolic Ca2+. Selected permeation properties of coupled RyR2 channels were comparable to those found for the single RyR2 channel. The
Ca2+ current amplitude-luminal Ca2+ relationship displayed a simple saturation and the channel selectivity for Ba2+ and Ca2+ ions was similar. Our results suggest that the major targets influenced by coupled gating are likely the gates of individual
RyR2 channels recruited into a functional complex, thus ensuring the correlation of Ca2+ fluxes. 相似文献
994.
Jana R. Herrmann Angelika Fuchs Thomas Eckert Stephanie Unterreitmeier Dmitrij Frishman 《Journal of molecular biology》2010,396(2):452-461
Folding and oligomerization of integral membrane proteins frequently depend on specific interactions of transmembrane helices. Interacting amino acids of helix-helix interfaces may form complex motifs and exert different types of molecular forces. Here, a set of strongly self-interacting transmembrane domains (TMDs), as isolated from a combinatorial library, was found to contain basic and acidic residues, in combination with polar nonionizable amino acids and C-terminal GxxxG motifs. Mutational analyses of selected sequences and reconstruction of high-affinity interfaces confirmed the cooperation of these residues in homotypic interactions. Probing heterotypic interaction indicated the presence of interhelical charge-charge interactions. Furthermore, simple motifs of an ionizable residue and GxxxG are significantly overrepresented in natural TMDs, and a specific combination of these motifs exhibits high-affinity heterotypic interaction. We conclude that intramembrane charge-charge interactions depend on sequence context. Moreover, they appear important for homotypic and heterotypic interactions of numerous natural TMDs. 相似文献
995.
Pomajbíková K Petrželková KJ Profousová I Petrášová J Modrý D 《The Journal of parasitology》2010,96(6):1139-1144
Balantidium coli is a ciliate reported in many mammalian species, including African great apes. In the former, asymptomatic infections as well as clinical balantidiasis have been reported in captivity. We carried out a cross-sectional study of B. coli in African great apes (chimpanzees, bonobos, and both species of gorillas) and examined 1,161 fecal samples from 28 captive facilities in Europe, plus 2 sanctuaries and 11 wild sites in Africa. Samples were analyzed with the use of Sheather's flotation and merthiolate-iodine-formaldehyde (MIFC) sedimentation. MIFC sedimentation was the more sensitive technique for diagnostics of B. coli in apes. Although not detected in any wild-ape populations, B. coli was diagnosed in 52.6% of captive individuals. Surprisingly, in the apes' feces, trophozoites of B. coli were commonly detected, in contrast with other animals, e.g., Old World monkeys, pigs, etc. Most likely reservoirs for B. coli in captive apes include synantropic rats. High starch diets in captive apes are likely to exacerbate the occurrence of balantidiasis in captive apes. 相似文献
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Dolezal T Kucerova K Neuhold J Bryant PJ 《The International journal of developmental biology》2010,54(10):1419-1424
We are using a candidate gene approach to identify genes contributing to cancer through somatic mutation. Somatic mutations were found in breast cancer samples in the human casein kinase I epsilon (CKIepsilon) gene, a homolog of the Drosophila gene dco in which certain point mutations lead to imaginal disc overgrowth. We therefore created fly genotypes in which the dco gene carried point mutations homologous to those discovered in CKIepsilon, and tested them in vivo. The results show that the most frequent mutation discovered in breast cancer, L39Q, causes a striking overgrowth phenotype in flies. Further experiments show that this mutation affects the newly recognized Fat/Warts signaling pathway, which controls organ size and shape in both flies and mammals. Another mutation, S101R, modifies the mutant phenotype so that the affected tissue disintegrates, mimicking more aggressive forms of breast cancer. Our results thus strongly support the conclusion that CKIepsilon mutations play important roles in breast carcinogenesis. 相似文献
1000.
Jana Jersáková Sílvia Castro Nicole Sonk Kathrin Milchreit Iva Schödelbauerová Till Tolasch Stefan Dötterl 《Evolutionary ecology》2010,24(5):1199-1218
Polyploidy has played a key role in plant evolution and diversification. Despite this, the processes governing reproductive
isolation among cytotypes growing in mixed-ploidy populations are still largely unknown. Theoretically, coexistence of diploid
and polyploid individuals in sympatric populations is unlikely unless cytotypes are prezygotically isolated through assortative
pollination. Here, we investigated the pre-mating barriers involved in the maintenance of three co-occurring cytotypes from
the genus Gymnadenia (Orchidaceae): tetraploid and octoploid G. conopsea and tetraploid G. densiflora. We assessed differences in flowering phenology, floral morphology, and visual and olfactory cues, which could lead to assortative
mating. Gas chromatography coupled with electroantennographic detection was used to identify scent compounds with physiological
activity in the two main pollinators, Deilephila porcellus and Autographa gamma. The importance of olfactory cues was also assessed in the field by analysing the moths’ responses to the olfactory display
of the plants, and by following the pollinator’s behaviour on artificial arrays. Our complex approach demonstrated that the
coexistence of Gymnadenia cytotypes in mixed-ploidy populations was only partly explained by differences in floral phenology, as cytotypes with overlapping
flowering (i.e., octoploid G. conopsea and tetraploid G. densiflora) might freely exchange pollen due to only 1 mm differences in spur lengths and the lack of assortative behaviour of pollinators.
While floral colour among the cytotypes was similar, floral scent differed significantly. Though both pollinator species seemed
to physiologically detect these differences, and the floral scent alone was sufficient to attract them, pollinators did not
use this cue to discriminate the cytotypes in the field. The absence of pre-mating barriers among cytotypes, except partial
temporal segregation, suggests the existence of other mechanisms involved in the cytotypes’ coexistence. The genetic differences
in ITS sequences among cytotypes were used to discuss the cytotype’s origin. 相似文献