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Walter Malorni Pietro L. Indovina Giuseppe Arancia Stefania Meschini Maria T. Santini 《In vitro cellular & developmental biology. Plant》1990,26(4):399-410
Summary This paper describes the microscopic evidence supporting a cesium-induced delay in the fusion of chick embryo myoblast membranes
during in vitro myogenic differentiation. We have recently demonstrated that the sharp decrease in the conductivity and permittivity
of the membranes of these myogenic cells at the time of fusion is delayed 30 h by the addition of cesium to the culture medium
(Santini et al., Biochim. Biophys. Acta 945:56–64; 1988). We report here that this delay in fusion is substantiated by direct
microscopic observation and that cesium also induces ultrastructural changes in the myoblast cells themselves. Possible mechanisms
by which cesium may cause both the delay in fusion as well as the ultrastructural changes observed are discussed.
This investigation was partially supported by an Italian Consiglio Nazionale delle Ricerche grant 85.00.304.02 (to P. L. I.). 相似文献
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Pietro Paolo Fanciullt Miguel Gaju Carmen Bach Francesco Frati 《Biological journal of the Linnean Society. Linnean Society of London》1997,62(4):533-551
Different species of the bristletail genus Lepismachilis were collected in 14 localities in Italy and Spain and an allozyme electrophoretic survey was carried out to estimate the degree of genetic variability and differentiation at intra- and interspecific levels. Four morphological species were initially identified (L osellai, L. y-signata, L. affinis, L. targionii), but the electrophoretic analysis demonstrated the presence of two additional species among the individuals of L. targionii (Lepismachilis spl and sp2). The validity of these species and their differentiation from L targionii were demonstrated by the fixation of alternative allelic patterns at several loci (7 in Lepismachilis spl and 8 in Lepismachilis sp2), coupled with fixed, previously undetected, morphological differences. In addition, Lepismachilis sp2 was sympatric with L. targionii in three collecting sites, where the fixation of alternative allelic patterns unequivocally demonstrated reproductive isolation. Genetic variability did not seem to be correlated with local ecological factors, and differences between species should rather be explained by different historical factors. Low levels of gene flow, estimated with two different indirect methods, were observed in L. targionii and L. y-signata, and were due to high levels of structuring among populations. Genetic differentiation among conspecific populations was not correlated to their geographical arrangement and the presence of loci fixed for different alleles among them suggested that stochastic factors (such as genetic drift) may have played a role in determining genetic differentiation of geographically isolated populations. Genetic divergence values indicated that the six species are well differentiated and allozyme profiles were diagnostic for all of them. On the other hand, allozyme data did not provide adequate information to resolve evolutionary relationships among the species, nor did they confirm the validity of the two subgenera (Lepismachilis and Berlesilis) in which the genus Lepismachilis is traditionally divided. 相似文献
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Summary The adrenal cortex of different mammals was studied by SEM in order to demonstrate its actual three-dimensional organization. In the rat, as well as in the cat and pig, the adrenal cortex appeared as a tunnelled continuum of polyhedral cells arranged in plate-like structures (laminae). This laminar arrangement was more evident in the inner fasciculate and reticular zones where the cortex revealed a striking similarity to liver tissue. The polyhedral cells of all cortical zones possessed regular facets populated by small pits, larger invaginations and numerous microvilli with the exception of very short and smooth areas probably corresponding to attachment zones and/or gap junctions. This cellular architecture produced a labyrinthic system of intercellular channels or lacunae in which the capillaries were suspended.The pericapillary areas of this labyrinth contained microvilli, amorphous material, a delicate net of fibrils and occasional cells. The intercellular compartment of this lacunar system was mainly bordered by numerous microvilli arising from endocrine cells.The luminal surface of the capillary wall showed not only irregularly protruding margins (interpretable as endothelial junctions) but also clearly overlapping and flattened endothelial extensions.In all the animals and areas of the adrenal cortex examined, the endothelial wall was provided with abundant clusters of small fenestrations (about 50 nm in diameter) generally arranged in sieve plates.
Larger fenestrations were noted mainly in the fasciculate and reticular zones of the cat and pig and occasionally in the rat.A final point related to the nature and significance of sinusoidal fenestrations was the occurrence of irregularly shaped and intracapillary located cells mainly noted in the deeper zones of the fasciculate and reticular zones of the gland. These elements — possessing the surface characteristics of macrophages — were observed, with their irregular and slender evaginations, in close proximity to the large fenestrations in a manner reminiscent of Kupffer cells within the lumen of liver sinusoids. 相似文献
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Leonardo Dapporto Thomas Schmitt Roger Vila Stefano Scalercio Heinrich Biermann Vlad Dincă Severiano F. Gayubo José A. González Pietro Lo Cascio Roger L. H. Dennis 《Journal of Biogeography》2011,38(5):854-867
Aim Our aims were to verify the existence of phylogenetic disequilibrium between butterfly lineages at the subcontinental scale for islands and the nearest mainland and to test the capacity of islands for hosting ancestral populations of butterflies and the significance of such relict populations. Location The western Mediterranean continental area of Europe and North Africa together with several large and small islands (Balearics, Tuscan Archipelago, Aeolian Archipelago, Capri, Sardinia, Sicily, Corsica). Methods Using geometric morphometrics, the shape of male genitalia was analysed in two common butterflies (Pyronia cecilia and Pyronia tithonus), whose spatial heterogeneity in the Mediterranean region has recently been described. Observed patterns in genital shapes were compared with shapes predicted for islands and fossil islands to assess the contribution of historical and current events in accounting for the transition from a refugial model to an equilibrium model. Measurements were taken for 473 specimens in 90 insular and mainland sites. Results The shape of the genitalia of populations of most islands differed substantially from that predicted by the equilibrium hypothesis while closely fitting the refugial hypothesis. The comparison between different models strongly suggests that islands maintain ancestral lineages similar to those living in Spain (P. cecilia) and France (P. tithonus). A high correlation between observed and predicted patterns on islands and fossil islands occurs during the first steps of modelled introgressive hybridization while the following steps exposed a successively lower fit, suggesting that the process from a refugial to an equilibrium situation is highly skewed towards an earlier non‐equilibrium. Main conclusions The observed non‐equilibrium pattern supports the refugial hypothesis, suggesting that an ancestral lineage was originally distributed from Spain to Italy, and also occupied offshore islands. This lineage, replaced in Italy, has persisted on the islands owing to their isolation. A comparison of the distribution patterns for genetic and morphometric markers in several species indicates that the situation highlighted for Pyronia may represent a common biogeographic feature for many Mediterranean butterflies. 相似文献
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Barbara?Biondi Elisa?Giannini Lucia?Negri Pietro?Melchiorri Roberta?Lattanzi Federica?Rosso Luigi?Ciocca Raniero?RocchiEmail author 《International journal of peptide research and therapeutics》2006,12(2):145-151
Summary Syntheses are described of new endomorphin 1 and 2 peptoid–peptide hybrids in which Tyr1 and either one or both Phe3 and Phe4 have been replaced by N-substituted-glycine. The preparation is also described of two glycosylated Hyp2-endomorphin 2 analogues in which either 2,3,4,6-tetra-O-acetyl glucose or glucose are β-O-glycosidically linked to the hydroxyproline residue. The Hyp2-endomorphin sequences have also been elongate by adding a C-terminal β-alanine residue and several linear dimers have been prepared by coupling either the native peptides or the modified analogues. The cyclo endomorphin 2 has also been synthesized. Preliminary pharmacological experiments on isolated organ preparations showed that the agonist activities of both endomorphin 1 and 2 are not significantly affected by the Pro/Hyp substitution. Phe4/Nphe substitution in the endomorphin 1 reduced the potency on guinea pig ileum (GPI) by about 100 times and abolished the agonist activity on mouse vas deferens (MVD) preparation. The decrease of the agonist activity induced by modification of one phenylalanine residue only, either Phe3 or Phe4, is lower on endomorphin 2. Either modification of both Phe3 and Phe4 or glycosylation of the Hyp2-endomorphin 2 cancelled any agonist activity on both preparations. The linear peptide dimers [endomorphin 1]2, [endomorphin 2]2, [Hyp2-endomorphin 1]2, [Hyp2-endomorphin 2]2, [Hyp2-endomorphin 1-Hyp2-endomorphin 2]2 or [Hyp2-endomorphin 2-Hyp2-endomorphin 1]2, are 7–19 times less potent than endomorphin 1 on GPI and significantly less active than endomorphins 1 and 2 on MVD. The other afforded modifications significantly affected or abolished the agonist activity of the resulting endomorphin analogues on both GPI and MVD preparations.The α-amino acid residues are of the L-configuration. Standard abbreviations for amino acid derivatives and peptides are according to the suggestions of the IUPAC-IUB Commission on Biochemical Nomenclature (1984) Eur. J. Biochem., 138, 9–37. Abbreviations listed in the guide published in (2003) J. Peptide Sci., 9, 1–8 are used without explanation. 相似文献
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Pietro D’Addabbo Moira Scascitelli Vincenzo Giambra Mariano Rocchi Domenico Frezza 《BMC evolutionary biology》2011,11(1):71
Background
The Immunoglobulin heavy chain (IgH) 3' Regulatory Region (3'RR), located at the 3' of the constant alpha gene, plays a crucial role in immunoglobulin production. In humans, there are 2 copies of the 3'RR, each composed of 4 main elements: 3 enhancers and a 20 bp tandem repeat. The single mouse 3'RR differs from the two human ones for the presence of 4 more regulative elements with the double copy of one enhancer at the border of a palindromic region. 相似文献10.