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21.
Khalid M. Chraibi B. Alain Latche Jean-Paul Roustan Jean Fallot 《Plant cell reports》1991,10(4):204-207
The effects of CoCl2, AgNO3 and ethylene released by exogenous 2-chloroethylphosphonic acid (Ethephon), were studied on shoot regeneration from cotyledons of Helianthus annuus cv. E8206R, a poorly regenerative cultivar. Inhibition of ethylene biosynthesis by CoCl2, at concentrations of 20 K, provoked a substantial enhancement of shoot regeneration (30 %): the control was poorly regenerative. However, CoCl2 had no effect when Ethephon was supplied. Inhibition of ethylene action by AgNO3, at concentrations of 10–25 M, caused a significant increase in plant regeneration: 25 % instead of 1.2 % in the control. Furthermore, addition of Ethephon to AgNO3-treated tissues failed to reduce the stimulation of shoot regeneration caused by AgNO3. On the basis of these findings, it is suggested that ethylene inhibits the regeneration process from cotyledons of sunflower.Abbreviations NAA
1-naphthalene acetic acid
- BAP
6-benzylamino-purine
- GA3
gibberellic acid
- Ethephon
2-chloroethylphosphonic acid
- MS
Murashige and Skoog medium
- AVG
aminoethoxyvinylglycine 相似文献
22.
Following the “Index of new names” (Theurillat etMoravec 1991a), the present work collects the names of syntaxa (in the sense of the Code of Phytosociological Nomenclature,Barkman et al. 1986) above subassociation rank typified in 1989. The list comprises 110 names of syntaxa. 相似文献
23.
Julien Deschênes Jean-Paul Valet Normand Marceau 《In vitro cellular & developmental biology. Plant》1980,16(8):722-729
Summary The two-step collagenase perfusion method originally developed for the high yield isolation of parenchymal cells from adult
rat livers has been adapted to rats of 1 day, 1 week, and 3 weeks of age. The use of this method to isolate hepatocytes from
five or six rats of the respective ages demonstrated its reliability in terms of cell yield, percentage of single cells, and
cell viability. In all cases, hepatocytes attach with high efficiency to fibronectin precoated dishes using serum-free culture
medium. The dynamics of spreading is faster for newborn hepatocytes than adult ones. The functional integrity of these parenchymal
liver cells was assessed by their capacity to secrete albumin and α-fetoprotein in serum-free medium and to express lactate
dehydrogenase activity over a 24-hr period in primary culture.
Part of this work was presented at the 30th Annual Meeting of the Tissue Culture Association, Seattle, June, 1979. 相似文献
24.
The substitution pattern of the water-soluble l-arabino-(4-O-methyl-d-glucurono)-d-xylan from redwood (Sequoia sempervirens) has been studied by enzymic degradation. Exhaustive hydrolysis by an endo-xylanase (EC 3.2.1.8) from a Basidiomycete Sporotrichum dimorphosporum left a residue accounting for 20% of the original d-xylan. In the dialyzable material, oligosaccharides having arabinose or 4-O-methylglucuronic acid residues attached to the non-reducing d-xylosyl end-group of xylobiose or xylotriose, respectively, were the smallest branched oligomers released. Action of the xylanase appears to involve a region of the polysaccharide backbone having three xylosyl residues. A mode of action is proposed that requires unsubstituted hydroxyl groups at C-2, C-3, and C-2′ of a xylobiosyl residue. The binding site seems to correspond to a shallow cavity. The composition and structure of the final residue of attack shows that the enzyme has no action when the xylosyl residues branched through O-2 are separated by only one, unsubstituted xylose residue. This pattern of action, the nature of the dialyzable products, and the production of a final residue in which the substituents are accumulated, suggest that the arabinosyl and glucosyl-uronic groups are irregularly distributed on the main chain of the xylan from redwood and that in some regions they are in close vicinity when not actually on adjacent xylosyl residues. 相似文献
25.
Claude Auriault Joël Pestel Michel Joseph Jean-Paul Dessaint Andre Capron 《Cellular immunology》1981,62(1):15-27
Discharge of lysosomal enzymes, measured by release of β-glucuronidase and cytotoxicity against Schistosoma mansoni schistosomula, was studied when rat macrophages were incubated in the presence of either IgG peptides, resulting from the cleavage of nonimmune IgG by parasitic proteases, or nonimmune aggregated IgG. With peptides, the macrophage activity showed a dramatic decrease while they were stimulated by IgG aggregates. In contrast, the synthesis of lymphocyte activating factor by macrophages was unaffected. The hydrolysis of IgG is carried out by two distinct enzymatic molecules released into the medium by the larvae. The mechanism by which nonimmune IgG peptides or aggregates inhibit or stimulate macrophage activity, regulated by both parameters indicated above, is discussed and is suggested as a general regulation mechanism for the macrophage activity required for parasite survival in the host. 相似文献
26.
Mutations of Chinese Hamster Somatic Cells from 2-Deoxygalactose Sensitivity to Resistance 下载免费PDF全文
In Chinese hamster somatic cells, the spontaneous change of phenotype from 2-deoxygalactose sensitivity to resistance was studied using fluctuation test experiments à la Luria and Delbrück (1943) for four Chinese hamster cell strains derived from V79. The results are consistent with true mutational events. The mutation rates are in the range of 1 to 3.5 X 10(-5) per cell per generation. The relationship between the 2-deoxyglactose resistance and the galactokinase markers is discussed. 相似文献
27.
Dr. Jean-Paul Mourier 《Cell and tissue research》1979,201(2):249-262
Summary The rate of 3H-thymidine incorporation into different parts of the renal proximal tubule of female sticklebacks treated with methyltestosterone was investigated using high-speed scintillation autoradiography. The results are compared with those from normal males before or after mucous transformation of the kidney. Labelled cells are observed in all parts of the proximal tubule, with marked variations from one segment to another. They are numerous in part 2 of the proximal tubule, particularly in the distal region. Male sex hormones affect the labelling rate in all parts of the nephron, especially in the distal region of part 2 of the proximal tubule. In that particular area, new tubule formation by budding is observed in some individuals, but this process does not appear to be a general one. Correlation between the frequency of these figures and the time of treatment could not be established. Comparing the action of sex hormones in females with that in males reveals a difference in reactivity in the proximal zone of part 2 of the proximal tubule, where methyltestosterone has a strong action in females; in contrast, in mature and immature males, only a few labelled cells are present in this region.It is concluded that kidney enlargement during the breeding season does not result only from a swelling of cells belonging to part 2 of the proximal tubule, as was generally believed, but also from a lengthening or even a proliferation of the proximal tubules, induced by an increase in mitotic activity controlled by male sex hormones.
Résumé L'incorporation de thymidine tritiée dans les tubules proximaux du rein est étudiée par autoradiographie rapide chez des Epinoches femelles préalablement traitées par la méthyltestostérone. Les résultats sont comparés avec ceux obtenus chez des mâles normaux ayant ou non développé un rein muqueux. Des cellules marquées sont présentes à tous les niveaux des tubules proximaux, mais leur nombre varie considérablement d'un segment à l'autre. Elles sont les plus nombreuses dans la seconde partie du tubule proximal, particulièrement dans sa région distale. Le taux de marquage est modifié dans toutes les régions du néphron, mais les variations sont les plus intenses dans la région distale de la seconde partie du tubule proximal, où l'on observe parfois la formation de nouveaux tubules par bourgeonnement. La comparaison des résultats obtenus dans les deux sexes fait apparaître une différence de réactivité au niveau de la zone proximale de la seconde partie du tubule proximal, où la méthyltestostérone agit fortement chez les femelles, alors qu'elle n'exerce pas d'effet notable chez les mâles.L'augmentation de volume du rein chez le mâle lors de la période de reproduction ne résulte donc pas uniquement d'un gonflement des cellules de la seconde partie du tubule proximal, comme on le pensait généralement. Des phénomènes mitotiques interviennent également dans ce processus, sous l'influence des hormones sexuelles mâles, qui conduisent à un allongement, voire à une multiplication des tubules proximaux.相似文献
28.
Eva B. Griepp John H. Peacock Merton R. Bernfield Jean-Paul Revel 《Experimental cell research》1978,113(2):273-282
We have examined correlations between morphological and functional evidence of cell coupling between aggregates of beating embryonic heart cells and underlying layers. Synchronously beating aggregate-layer pairs were compared with asynchronous pairs. Intracellular microelectrode studies demonstrated that asynchronously beating aggregate-layers could not be induced to beat synchronously by electrical stimulation of the aggregate, whereas 86% of synchronous instances showed propagation of stimulating current pulses from aggregate to layer. By freeze fracture we have found significant differences both in the number and in the total area of gap junctions between the aggregate-layer interfaces of synchronous and asynchronous preparations. The data suggest that synchronous beating is a reliable functional indication of effective ionic coupling, and requires a certain area and number of gap junction/cell. 相似文献
29.
Francis M. Delmotte Jean-Paul D.J. Privat Michel L.P. Monsigny 《Carbohydrate research》1975,40(2):353-364
4-Methylumbelliferyl 2-acetamido-2-deoxy-β-D-glucopyranoside, 2-acetamido-4-O-(2-acetamido-2-deoxy-β-D-glucopyranosyl)-2-deoxy-β-D-glucopyranoside (di-N-acetyl-β-chitobioside), and O-(2-acetamido-2-deoxy-β-D-glucopyranosyl)-(1→4)-O-(2-acetamido-2-deoxy-β-D-glucopyranosyl)-(1→4)-2-acetamido-2-deoxy-β-D-glucopyranoside (tri-N-acetyl-β-chitotrioside) were obtained in good yield from the corresponding peracetylated glycosyl chlorides by condensation with the sodium salt of 4-methylumbelliferone in N,N-dimethylformamide. The trisaccharide glycoside is hydrolyzed by lysozyme and is, therefore, a convenient substrate for this enzyme; the 4-methylumbelliferone produced can be determined by the increase of the fluorescence intensity at 442 nm. The intensity of the fluorescence of 4-methylumbelliferyl tri-N-acetyl-β-chitotrioside is enhanced upon binding with lysozyme without modification of the position of the absorption maximum. The binding constant and the rate of hydrolysis of the trisaccharide glycoside by lysozyme are higher than those obtained with p-nitrophenyl tri-N-acetyl-β-chitotrioside. 相似文献
30.
Gene silencing with RNA interference in the human pathogenic fungus Aspergillus fumigatus 总被引:13,自引:0,他引:13
Aspergillus fumigatus is an opportunistic pathogenic fungus which causes fatal invasive aspergillosis among immunocompromised patients. To obtain a better understanding of the key elements involved in A. fumigatus virulence and to identify possible drug targets, it is necessary to be able to generate gene-deletion strains. Unfortunately, the molecular techniques available do not include a rapid method to disrupt and identify essential genes. RNA interference, a process in which the presence of double-stranded RNA homologous to a gene of interest results in specific degradation of the corresponding message, has been successfully tested on A. fumigatus. We have shown that expression of double stranded RNA corresponding to portions of the ALB1/PKSP and FKS1 genes results in reduced mRNA levels for those genes, with phenotypic consequences similar to that of gene disruption. The two genes could also be subjected to simultaneous interference through expression of chimeric double-stranded RNA. Use of RNA interference in Aspergillus will allow easier examination of the phenotypic consequences of reducing expression of a gene of interest, especially for essential genes. 相似文献