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961.
962.
Barbara Conti Francesco Berti David Mercati Fabiola Giusti Romano Dallai 《Journal of morphology》2010,271(2):244-254
The secretory activity of the two branched malpighian tubules (MTs) of the second‐instar larva in Aeolothrips intermedius is described. MTs of adult thrips have the typical ultrastructure of excretory epithelium with apical microvilli containing long mitochondria and a rich system of basal membrane infoldings. In the second‐instar larva just before pupation, the ultrastructure of MT epithelial cells is dramatically different, and there are numerous huge Golgi systems in the cytoplasm. These cells are involved in an intense secretory activity to produce an electron‐dense product which is released into the MTs lumen. This secretion is extruded from the hindgut and used by the second‐instar larva to build an elaborate protective cocoon for pupation. Electron‐spray‐ionization mass spectrometry analysis of the cocoon revealed the presence of a β‐N‐acetyl‐glucosamine, the main component of chitin, which is also present in the cocoons of Neuroptera and some Coleoptera. J. Morphol., 2010. © 2009 Wiley‐Liss, Inc. 相似文献
963.
Storz JF Bhat HR Kunz TH 《Evolution; international journal of organic evolution》2001,55(6):1215-1223
Population subdivision into behaviorally cohesive kin groups influences rates of inbreeding and genetic drift and has important implications for the evolution of social behavior. Here we report the results of a study designed to test the hypothesis that harem social structure promotes inbreeding and genetic subdivision in a population with overlapping generations. Genetic consequences of harem social structure were investigated in a natural population of a highly polygynous fruit bat, Cynopterus sphinx (Chiroptera: Pteropodidae), in western India. The partitioning of genetic variance within and among breeding groups was assessed using 10-locus microsatellite genotypes for 431 individually marked bats. Genetic analysis of the C. sphinx study population was integrated with field data on demography and social structure to determine the specific ways in which mating, dispersal, and new social group formation influenced population genetic structure. Microsatellite data revealed striking contrasts in genetic structure between consecutive offspring cohorts and between generations. Relative to the 1998 (dry-season) offspring cohort, the 1997 (wet-season) cohort was characterized by a more extensive degree of within-group heterozygote excess (F(IS) = -0.164 vs. -0.050), a greater degree of among-group subdivision (F(ST) = 0.123 vs. 0.008), and higher average within-group relatedness (r = 0.251 vs. 0.017). Differences in genetic structure between the two offspring cohorts were attributable to seasonal differences in the number and proportional representation of male parents. Relative to adult age-classes, offspring cohorts were characterized by more extensive departures from allelic and genotypic equilibria and a greater degree of genetic subdivision. Generational differences in F-statistics indicated that genetic structuring of offspring cohorts was randomized by natal dispersal prior to recruitment into the breeding population. Low relatedness among harem females (r = 0.002-0.005) was primarily attributable to high rates of natal dispersal and low rates of juvenile survivorship. Kin selection is therefore an unlikely explanation for the formation and maintenance of behaviorally cohesive breeding groups in this highly social mammal. 相似文献
964.
In the gustatory system, the recognition of sugars, amino acids and bitter-tasting compounds is the function of specialized G protein-coupled receptors. Recently, two members of novel subfamily of G protein-coupled receptors were proposed to function as taste receptors based on their specific expression in taste receptor cells. Here, we report the identification of a third member, T1R3, of this family of receptors. T1R3 maps near the telomere of mouse chromosome 4 rendering it a candidate for the Sac locus, a primary determinant of sweet preference in mice. Consistent with its candidacy for the Sac locus, T1R3 displays taste receptor cell-specific expression. In addition, taster and non-taster strains of mouse harbor different alleles of T1R3. 相似文献
965.
beta-Amyloid peptides (Abetas) share with lipopolysaccharide, a potent pro-inflammatory agent, the property of stimulating glial cells or macrophages to induce various inflammatory mediators. We recently reported that central administration of lipopolysaccharide induces peripheral interleukin-6 responses via both the central and peripheral norepinephrine system. In this study, the effect of intracerebroventricular injection of various synthetic Abetas on plasma interleukin-6 levels was examined in mice. Abeta(1-42) dose-dependently increased plasma interleukin-6 levels: 'aged' Abeta(1-42) was more effective than fresh, whereas Abeta(42-1) had no effect. 'Aged' Abeta(1-42) (205 pmol/mouse i.c.v.)-induced plasma interleukin-6 peaked at 2 h post injection, which is earlier than the peak time of the Abeta(1-42)-induced brain interleukin-6, tumor necrosis factor-alpha and interleukin-1beta levels, which was 4, 4 and 24 h, respectively. Among various peripheral organs, Abeta(1-42) (205 pmol/mouse i.c.v.) significantly increased interleukin-6 mRNA expression in lymph nodes and liver. Abeta(1-42) (205 pmol/mouse i.c.v.) significantly increased norepinephrine turnover in both hypothalamus and spleen. Either central or peripheral norepinephrine depletion effectively inhibited the Abeta(1-42)-induced peripheral interleukin-6 response. Pretreatment with prazosin (alpha(1)-adrenergic antagonist), yohimbine (alpha(2)-adrenergic antagonist), and ICI-118,551 (beta(2)-adrenergic antagonist), but not with betaxolol (beta(1)-adrenergic antagonist), inhibited Abeta(1-42)-induced plasma interleukin-6 levels. These results demonstrate that centrally administered Abeta(1-42) effectively induces the systemic interleukin-6 response which is mediated, in part, by central Abeta(1-42)-induced activation of the central and the peripheral norepinephrine systems. 相似文献
966.
The isolation of a new type of thrombin inhibitor, called triabin, from the saliva of the hematophagous bug Triatoma pallidipennis,
has recently been described. In the in vitro platelet aggregation inhibition assay triabin has a similar potency as the thrombin
inhibitor hirudin now in phase III clinical trials. However, in another in vitro assay using a low molecular weight substrate
for thrombin, triabin does not inhibit thrombin completely even at 6 fold higher molar doses in comparison with hirudin. This
means that triabin has a novel mode of action towards thrombin making triabin into an interesting candidate as a therapeutic
agent. Recently it has been shown that a recombinant baculovirus can be efficiently used for the triabin production in insect
cells and that the yields in adherent cultures of High Five™ cells (approx. 20 mg l-1) were about 7 fold higher than in adherent
cultures of Sf9 cells (approx. 3 mg l- 1). To optimize the triabin yield from the baculovirus/insect cell expression system,
experiments were performed with suspension adapted cultures of High Five™ cells to investigate the effects of the state of
the host cell, of the multiplicity of infection, of the cell density at the time of infection and of supplementation of the
medium with nutrients and oxygen. Triabin yields of up to 200 mg l-1, as determined by an activity assay, could finally be
obtained here.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
967.
968.
Shinya M Furutani-Seiki M Kuroiwa A Takeda H 《Development, growth & differentiation》1999,41(2):135-142
The floor plate is located at the ventral midline of the neural tube in vertebrates. Floor-plate development is severely impaired in zebrafish one-eyed pinhead (oep) mutants. oep encodes a membrane-bound protein with an epiblast growth factor (EGF) motif and functions autonomously in floor-plate precursors. To understand the cell behavior and cell-cell interaction during floor-plate development, the distribution and gene expression of wild-type and oep mutant cells in genetic mosaics were examined. When mutant shield cells were transplanted into a wild-type host, an ectopic neural tube with a floor plate was induced. However, the floor plate of the secondary axis was consistently devoid of mutant cells while its notochord was composed entirely of mutant cells. This indicates that oep shield cells adopt only a notochord fate in a wild-type environment. In reciprocal transplants (wild to oep), however, grafted shield cells frequently contributed to part of the floor-plate region of the secondary neural tube and expressed floor-plate markers. Careful examination of serial sections revealed that a mutant neural cell, when located next to the wild-type cells at the ventral midline, inhibited floor-plate differentiation of the adjacent wild-type cells. This inhibition was effective over an area only one- or two-cells wide along the anteroposterior axis. As the cells located at the ventral midline of the oep neural tube are thought to possess a neural character, similar to those located on either side of the floor plate in a wild-type embryo, this inhibition may play an important role during normal development in restricting the floor-plate region into the ventral-most midline by antagonizing homeogenetic signals from the floor-plate cells. 相似文献
969.
The selfish DNA hypothesis predicts that natural selection is responsible for preventing the unregulated build up of transposable
elements in organismal genomes. Accordingly, between-species differences in the strength and effectiveness of selection against
transposons should be important in driving the evolution of transposon activity and abundance. We used a modeling approach
to investigate how the rate of self-fertilization influences the population dynamics of transposable elements. Contrasting
effects of the breeding system were observed under selection based on transposon disruption of gene function versus selection
based on element-mediated ectopic exchange. This suggests that the comparison of TE copy number in organisms with different
breeding systems may provide a test of the relative importance of these forces in regulating transposon multiplication. The
effects of breeding system also interacted with population size, particularly when there was no element excision. The strength
and effectiveness of selection against transposons was reflected not only in their equilibrium abundance, but also in the
per-site element frequency of individual insertions and the coefficient of variation in copy number. These results are discussed
in relation to evidence on transposon abundance available from the literature, and suggestions for future data collection.
With their immense variety of breeding systems,plants will be extremely important for comparative studies and for sorting
out the forces influencing...variation.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
970.
The Na,K-ATPase is a major ion transport protein found in higher eukaryotic cells. The enzyme is composed of two subunits,
α and β, and tissue-specific isoforms exist for each of these, α1, α2 and α3 and β1, β2 and β3. We have proposed that an additional
α isoform, α4, exists based on genomic and cDNA cloning. The mRNA for this gene is expressed in rats and humans, exclusively
in the testis, however the expression of a corresponding protein has not been demonstrated. In the current study, the putative
α4 isoform has been functionally characterized as a novel isoform of the Na,K-ATPase in both rat testis and in α4 isoform
cDNA transfected 3T3 cells. Using an α4 isoform-specific polyclonal antibody, the protein for this novel isoform is detected
for the first time in both rat testis and in transfected cell lines. Ouabain binding competition assays reveal the presence
of high affinity ouabain receptors in both rat testis and in transfected cell lines that have identical K
D
values. Further studies of this high affinity ouabain receptor show that it also has high affinities for both Na+ and K+. The results from these experiments definitively demonstrate the presence of a novel isoform of the Na,K-ATPase in testis.
Received: 4 December 1998/Revised: 1 February 1999 相似文献