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11.
M. Pilar López M. Jose Gómez-Lechón Jose V. Castell 《In vitro cellular & developmental biology. Plant》1988,24(6):511-517
Summary This study examines the factors involved in the rapid glycolysis and glycogenolysis that occur during the first stages of
hepatocyte culture: a) Shortly after seeding glycolysis, estimated as lactate released to culture medium, increased 10 times
in comparison to that reported in vivo. By 8 to 9 h of culture, hepatocytes were nearly glycogen-depleted even in the presence
of insulin. b) 6-Phosphofructo-2-kinase remained 100% active during this period. The proportion of the initial active phosphorylase
(87%) decreased to 57% by 7 h of culture. c) Fructose 2,6-bisphosphate content was initially similar to that found in liver
of fed animals, decreased after seeding and increased thereafter up to four times the initial concentration. In spite of changes
in the concentration of this activator, the glycolytic rate remained high and constant. d) ADP and AMP increased sharply after
cell plating, reaching values 1.7 and 3.5 times higher. The rise in AMP levels may be involved in the activation of glycolysis
and glycogenolysis, because this metabolite is known to act as an allosteric activator of phosphofrucktokinase and glycogen
phosphorylase. This metabolic situation resembles that of cells under hypoxia.
Part of this work was presented at the 38th Annual Meeting of the Tissue Culture Association, Washington, DC, May 1987. 相似文献
12.
Stomatal response to air humidity and its relation to stomatal density in a wide range of warm climate species 总被引:1,自引:0,他引:1
Mabrouk A. El-Sharkawy James H. Cock Ana Del Pilar Hernandez 《Photosynthesis research》1985,7(2):137-149
The gas exchange of 19 widely different warm climate species was observed at different leaf to air vapour pressure deficits (VPD). In all species stomata tended to close as VPD increased resulting in a decrease in net photosynthesis. The absolute reduction in leaf conductance per unit increase in VPD was greatest in those species which had a large leaf conductance at low VPDs. This would be expected even if stomata of all species were equally sensitive. However the percentage reduction in net photosynthesis (used as a measure of the relative sensitivity of stomata of the different species) was also closely related to the maximal conductance at low VPD. Similarily the relative sensitivity of stomata to changes in VPD was closely related to the weighted stomatal density or crowding index.The hypothesis is presented that stomatal closure at different VPDs is related to peristomatal evaporation coupled with a high resistance between the epidermis and the mesophyll and low resistance between the stomatal apparatus and the epidermal cells. This hypothesis is consistent with the greater relative sensitivity of stomata on leaves with a high crowding index.The results and the hypothesis are discussed in the light of selection, for optimal productivity under differing conditions of relative humidity and soil water availablility, by observation of stomatal density and distribution on the two sides of the leaf.Visiting scientist, plant physiologist and research assitant of the Cassava Program 相似文献
13.
F Vyskocil J Pilar H Zemková P Svoboda V Vítek J Teisinger 《Biochemical and biophysical research communications》1983,116(2):783-790
Bleomycin 2 X 10(-6) and 6 X 10(-6) mol.1(-1) increased the activity of specific (Na+-K+) ATPase of the rat brain microsomes. It also stimulated the electrogenic (Na+-K+) pump in intact skeletal muscle cells. The blocking effect of vanadyl (+4V) on membrane (Na+-K+) ATPase was eliminated completely by the drug, but the action of vanadate (+5V) was counteracted only partially. Electron paramagnetic resonance spectra revealed the formation of a +4V - bleomycin complex which is still able to activate the (Na+-K+) ATPase. 相似文献
14.
The developmental influence of neuron-target interaction upon transmitter synthesis from labeled precursor and the capacity to release labeled transmitter were examined in dispersed cell cultures of embryonic ciliary ganglion neurons by comparing cultures of neurons plated alone and neurons plated upon pectoral myotubes. Of the total ACh synthesized from radiolabeled choline by neurons plated alone, more than half is via a Na+-dependent path, but a larger fraction of the synthesis is Na+ insensitive in culture than in mature neurons in vivo. In addition, at 1 week in culture the neurons lacking target failed to significantly increase ACh synthesis from the labeled choline in response to a previous high [K+]0 depolarization. Synthetic responsiveness to depolarization is a characteristic of mature nerve terminals in this preparation. One week after plating neurons onto myotube cultures, synthesis of ACh from the exogenous precursor is double that of sibling cultures lacking muscle, and prior depolarization with [K+]0 results in an increase in labeled product. Release from the labeled transmitter pool by the neurons with myotubes was also enhanced. [3H]ACh release elicited by depolarization via a Ca2+-dependent mechanism was more than fivefold higher in the cocultures. The influence of coculture with myotubes upon neuronal development is not duplicated by the neurons themselves despite formation of apparent interneuronal synapses (G. Crean, G. Pilar, J. Tuttle, and K. Vaca, 1982, J. Physiol. (London). 331, 87-104), by "fibroblasts" or medium conditioned over myotube cultures. Neurons under these conditions neither increase synthesis of [3H]ACh in response to a prior depolarization nor demonstrate enhanced basal [3H]ACh synthesis and release. Thus, coculture of embryonic ciliary ganglion neurons with a striated muscle target has a somewhat specific inductive effect, enhancing the capacity for neuronal [3H]ACh synthesis and release toward mature levels. This influence of a readily accessible target upon ciliary neuron cholinergic development in vitro may reflect a normal neuromuscular interaction occurring during embryogenesis. 相似文献
15.
The time of the last DNA replication of the Mauthner's neuron precursor cell has been investigated using radioautography. Embryos of Xenopus laevis were labeled at different stages of early development by single microinjections of tritiated thymidine. Labeling times were designed to cover the entire period of development between gastrula and hatching stages. The embryos were fixed at later stages (41 to 44, according to Nieuwkoop and Faber, 1967), when the Mauthner neuron can be readily distinguished by its characteristically large size and large nucleolus.Mauthner neurons of embryos which received tritiated thymidine from stage 10 (beginning of gastrulation) to stage 12 (advanced gastrula, medium yolk plug) were always labeled. Those embryos which received the isotope at or after stage (advanced gastrula, small yolk plug) were never found labeled. These results imply that the last DNA replication of the cell destined to give rise to the Mauthner neuron occurs during the last gastrula stages. This last DNA replication immediately proceeds the time of the so-called “histogenetic determination” of the Mauthner neuron proposed to correspond to stage 13 (slit blastopore) by Stefanelli (1951).Therefore it appears that the developmental program of the Mauthner neuron involves a remarkably early cessation of DNA replication closely followed by histogenetic determination. This is the earliest known event of this type for a specific, well characterized neuron in the amphibian embryo. 相似文献
16.
Joaquin Royo Isabel Diaz Pablo Rodriquez-Palenzuela Pilar Carbonero 《Plant molecular biology》1996,31(5):1051-1059
The geneItr1, encoding trypsin inhibitor BTI-CMe, has been obtained from a genomic library ofHordeum vulgare L. The gene has no introns and presents in its 5-upstream region 605 bp that are homologous to the long terminal repeats (LTR) of the copia-like retro-transposon Bare-1. Functional analysis of theItr1 promoter by transient expression in protoplasts derived from different barley tissues, has shown that in this system theItr1 promoter retains its endosperm specifity and thetrans-regulation mediated by theLys3a gene. The proximal promoter extending 343 bp upstream of the translation initiation ATG codon is sufficient to confer fullGUS expression and for endosperm specifity. In protoplasts derived from thelys3a mutant, Risø 1508,GUS activity was less than 5% of that obtained with the same constructs in the protoplasts of wild-type Bomi from which it derives. Gel retardation experiments, after incubation with proteins obtained from both types of endosperm nuclei, also show differential patterns. Possible reasons for these differences are discussed.Equal authours 相似文献
17.
18.
Gemma Fabris M. Pilar Marco Francisco Camps 《Archives of insect biochemistry and physiology》1994,27(2):77-87
The control of Spodoptera littoralis sex pheromone biosynthesis has been investigated with synthetic pheromone biosynthesis activating neuropeptide (PBAN) and different labeled tracers using an in vitro isolated gland system. Responsiveness of the glands to PBAN stimulation was impaired by careless tissue manipulation. The fact that PBAN is active in the isolated gland system suggests that this might be a target organ for this peptide in S. littoralis. As reported previously with Br-SOG extracts and intact females, label incorporation into the pheromone increased in glands treated with PBAN from all the precursors tested. However, the formation of labeled intermediates from d5E11–14:Acid also occurred in glands incubated in the absence of the peptide, but the amounts of d5Z9, E11–14:Acid were lower in PBAN treated glands than in controls. These results indicate that PBAN controls pheromone biosynthesis in S. littoralis by regulating the reduction of acyl moieties. © 1994 Wiley-Liss, Inc. 相似文献
19.
Pablo Morales Alfredo Corell Jorge Martínez-Laso J. Manuel Martín-Villa Pilar Varela Estela Paz-Artal Luis-M. Allende Antonio Arnaiz-Villena 《Immunogenetics》1993,38(5):323-331
Three new allelic forms of the HLA-G DNA sequence (HLA-G*II, HLA-G*III, and HLA-G*IV) have been identified. With the HLA-G*I sequence (previously designated HLA 6.0) as a reference, HLA-G*II shows a silent (G A) mutation at the third base of codon 57, HLA-G*III bears a non-synonymous (A T), but conservative, (Thr Ser) substitution at the first base of codon 31, and HLA-G*IV shows two silent substitutions: (A T) at the third base of codon 107 and (G A) at the third base of codon 57. A rapid method of singling out each allele on genomic DNA has been developed by using polymerase chain reaction amplification followed by restriction endonuclease treatment. Also, more or less strong linkage disequilibria has been found between most HLA-A alleles and either HLA-G*I or *II, both being the most prevalent alleles in the population, with a genotypic frequency of 0.55 and 0.38, respectively; HLA-G*III is very rare and HLA-G*IV has a genotypic frequency of 0.07. An evolutive classification of HLA-A alleles results according to their association with either HLA-G*I or HLA-G*II, which does not correlate with the classical serological cross-reacting groups classification. The finding of a strong and selective A/G linkage disequilibria with most HLA-A alleles, together with the existence of less frequent random A/G associations, may suggest that there exist in different haplotypes true and varied A/G genetic distances (and not a recombinational hotspot). It may be inferred from preliminary data that in primates HLA-A/G haplotypes bearing G*II may have appeared later than those bearing G*I.The nucleotide sequence data reported in this paper have been submitted to the GenBank and EMBL nucleotide sequence databases and have been assigned the following accession numbers: EMBL-X60983 (HLA-G*II), GenBank-M99048 (HLA-G*III), and GenBank-L07784 (HLA-G*IV).The contribution to this paper by P. Morales and A. Corell is equal, and the order of authorship is arbitrary.
Correspondence to: A. Arnaiz-Villena. 相似文献
20.
An understanding of plant responses to fluctuations in environment is critical to predictions of plant and ecosystem responses
to climate change. In the northern hemisphere, the northern limits of distribution of major biomes are probably determined
by the tolerance of their dominant physiognomic types (e.g., deciduous hardwood trees) to minimum winter temperatures and
can thus be predicted from long-term patterns of temperature fluctuations. At a more detailed level, the responses of functional
groups of plants to altered climate can be predicted from their known responses to fluctuations in soil resources (nutrients
and water) and the expected effect of climatic change on these soil resources. Laboratory and field experiments demonstrate
the feasibility of this approach. 相似文献