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101.
Olivier Galy Patricia Latour-Lambert Kais Zrelli Jean-Marc Ghigo Christophe Beloin Nelly Henry 《Biophysical journal》2012,103(6):1400-1408
Most bacteria live in the form of adherent communities forming three-dimensional material anchored to artificial or biological surfaces, with profound impact on many human activities. Biofilms are recognized as complex systems but their physical properties have been mainly studied from a macroscopic perspective. To determine biofilm local mechanical properties, reveal their potential heterogeneity, and investigate their relation to molecular traits, we have developed a seemingly new microrheology approach based on magnetic particle infiltration in growing biofilms. Using magnetic tweezers, we achieved what was, to our knowledge, the first three-dimensional mapping of the viscoelastic parameters on biofilms formed by the bacterium Escherichia coli. We demonstrate that its mechanical profile may exhibit elastic compliance values spread over three orders of magnitude in a given biofilm. We also prove that heterogeneity strongly depends on external conditions such as growth shear stress. Using strains genetically engineered to produce well-characterized cell surface adhesins, we show that the mechanical profile of biofilm is exquisitely sensitive to the expression of different surface appendages such as F pilus or curli. These results provide a quantitative view of local mechanical properties within intact biofilms and open up an additional avenue for elucidating the emergence and fate of the different microenvironments within these living materials. 相似文献
102.
Sergey N. Mikhailov Andrei A. Rodionov Ekaterina V. Efimtseva Boris S. Ermolinsky Marina V. Fomitcheva Nelly Sh. Padyukova 《Nucleosides, nucleotides & nucleic acids》2013,32(4-5):691-692
Abstract The unexpected formation of trisaccharide nucleosides during synthesis of purine 5′-O-β-D-ribofuranosylnucleosides in the presence of Lewis acids was observed. 相似文献
103.
Anita Mac Nelly Marco Kai Ale? Svato? Gabriele Diekert Torsten Schubert 《Applied and environmental microbiology》2014,80(14):4313-4322
The anaerobic dehalogenation of organohalides is catalyzed by the reductive dehalogenase (RdhA) enzymes produced in phylogenetically diverse bacteria. These enzymes contain a cobamide cofactor at the active site and two iron-sulfur clusters. In this study, the tetrachloroethene (PCE) reductive dehalogenase (PceA) of the Gram-positive Desulfitobacterium hafniense strain Y51 was produced in a catalytically active form in the nondechlorinating, cobamide-producing bacterium Shimwellia blattae (ATCC 33430), a Gram-negative gammaproteobacterium. The formation of recombinant catalytically active PceA enzyme was significantly enhanced when its dedicated PceT chaperone was coproduced and when 5,6-dimethylbenzimidazole and hydroxocobalamin were added to the S. blattae cultures. The experiments were extended to D. hafniense DCB-2, a reductively dehalogenating bacterium harboring multiple rdhA genes. To elucidate the substrate spectrum of the rdhA3 gene product of this organism, the recombinant enzyme was tested for the conversion of different dichlorophenols (DCP) in crude extracts of an RdhA3-producing S. blattae strain. 3,5-DCP, 2,3-DCP, and 2,4-DCP, but not 2,6-DCP and 3,4-DCP, were reductively dechlorinated by the recombinant RdhA3. In addition, this enzyme dechlorinated PCE to trichloroethene at low rates. 相似文献
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107.
Plant and Soil - Legumes integrated in crop rotations are intended to improve crop nitrogen (N) supply and yield. In conservation agriculture (CA) systems under low input conditions on highly... 相似文献
108.
Vitaly N. Nikandrov Oleg N. Murashko Galina V. Vorobyova Nelly S. Pyzhova Natalie V. Kvyatkovskaya Oksana A. Bartalevich 《International journal of peptide research and therapeutics》1997,4(4-6):497-502
Summary The formation of stable equimolar complexes of streptokinase or plasminogen with muscle lactate dehydrogenase or pyruvate
kinase, heart mitochondrial malate dehydrogenase and hepatic catalase at pH 7.4, 3.0 and 10.0 was first detected by differential
spectroscopy methods. All complexes, except those of plasminogen with dehydrogenases, were resistant to 6 M urea. Judging
from circular dichroism spectra, tertiary and secondary structures were considerably changed in the complexes. These changes
were significantly dependent upon the nature of interacting proteins; in some cases their structures were more ordered. NAD
(but not NADH) hampered the formation of streptokinase complexes with dehydrogenases. The plasminogen-activating function
of streptokinase and the ability of plasminogen to be activated by streptokinase in the complexes with oxidoreductases were
essentially unchanged. Pyruvate kinase induced a moderate (by 35%) increase in the streptokinase activating function. It is
assumed that the formation of complexes of streptokinase or plasminogen with enzymes may serve as a link in metabolic regulation
and/or intercellular interactions. 相似文献
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110.
Effects of aluminium treatment on Norway spruce roots: Aluminium binding forms,element distribution,and release of organic substances 总被引:1,自引:1,他引:0
Heim Alexander Luster Jörg Brunner Ivano Frey Beat Frossard Emmanuel 《Plant and Soil》1999,216(1-2):103-116
In order to investigate if Al resistance in Norway spruce (Picea abies[L.] Karst.) can be attributed to similar exclusion mechanisms as they occur in several crop plants, three-year-old Norway
spruce plants were treated for one week in hydroculture with either 500 μM AlCl3 or CaCl2 solutions at pH 4. Sequential root extraction with 1 M NH4Cl and 0.01 M HCl and EDX microanalysis revealed that Al and Ca in cell walls and on the surface participated in exchange processes. About
half of the Al extracted by the sequential extraction was not exchangeable by 1 M NH4Cl. Phenolics and phosphate present in the root extracts are possible ligands for Al adsorbed to or precipitated at the root
in a non-exchangeable form. In both treatments, C release during the first period of 2 d was much higher than during the remaining
time of the experiment. Al treated plants released less total C, carbohydrates and phenolics than did Ca treated plants. Acetate
was the only organic acid anion that could be detected in some samples of both treatments. Free amino acids were present at
micromolar concentrations but as hydrolysis did not increase their yield, there was no evidence of peptide release. One to
two thirds of the released C were large enough not to pass a 1 kDa ultrafilter. The results suggest that exudation of soluble
organic complexors is not a major Al tolerance mechanism in Norway spruce, although complexation of Al by phenolic substances
released by the root could be detected by fluorescence spectroscopy. Aluminium tolerance could rather be attributed to immobilization
in the root apoplast, where strong binding sites are available or precipitation may occur.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献