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191.
Pessione E Giuffrida MG Prunotto L Barello C Mazzoli R Fortunato D Conti A Giunta C 《Proteomics》2003,3(6):1070-1076
Study of the bacterial membrane proteome, though in its early stages, is a field of growing interest in the search for information about nutrient transport and processing. We tested different strategies and chemical compounds to extract proteins from the membranes (inner and outer) of Acinetobacter radioresistens S13, a Gram-negative bacterium selected for its ability to degrade aromatics. A. radioresistens S13 was monitored under different growth substrate conditions, using acetate, benzoate or phenol as sole carbon source. Two-dimensional gel electrophoresis map analysis of membrane extracts from benzoate- and phenol-grown cells reveals differences versus controls (acetate-grown cultures). Primarily, a different pattern of spots was observed and, in particular, some proteins were only expressed in the presence of aromatic substrate. Among these, we detected a Na(+)/H(+) antiporter, whose function is likely to be regulation of intracellular pH, and an ABC type sugar transport system, probably involved in capsular polysaccharide translocation. We also identified other proteins, detectable in acetate-grown but over-expressed in aromatic-grown cells. These include: (1) an outer membrane protein ascribable to an OmpA-like protein, recently described in the literature as "alasan", a bioemulsifying agent involved in solubilizing and enhancing bioavailability of hydrocarbons; (2) a trimeric porin of the PhoE family also belonging to the outer membrane and involved in facilitating the transport of anions (especially phosphate); and (3) two glycosyl transferases probably involved in capsules and/or lipopolysaccharide biosynthesis. Study of the bacterial membrane proteome helps to elucidate the role of the membrane as modulable site enabling communication between internal and external environments. 相似文献
192.
Cavalli A Haberthür U Paci E Caflisch A 《Protein science : a publication of the Protein Society》2003,12(8):1801-1803
Proteins fold in a time range of microseconds to minutes despite the large amount of possible conformers. Molecular dynamics simulations of a three-stranded antiparallel beta-sheet peptide (for a total of 12.6 microsec and 72 folding events) show that at the melting temperature the unfolded state ensemble contains many more conformers than those sampled during a folding event. 相似文献
193.
D'Elios MM Appelmelk BJ Amedei A Bergman MP Del Prete G 《Trends in molecular medicine》2004,10(7):316-323
Pathogens can induce autoreactive T cells to initiate autoimmune disease by several mechanisms. Pathogen-induced inflammation results in the enhanced presentation of self antigens, which causes the expansion of the activated autoreactive T cells that are required for disease onset. Alternatively, a pathogen might express antigens with epitopes that are structurally similar to epitopes of autoantigens, resulting in a mechanism of molecular mimicry. This is the case for Helicobacter pylori-associated human autoimmune gastritis, in which the activated CD4+ Th1 cells that infiltrate the gastric mucosa cross-recognize the epitopes of self gastric parietal cell H(+)K(+)-ATPase and of various H. pylori proteins. Therefore, in genetically susceptible individuals, H. pylori infection can start or worsen gastric autoimmunity, leading to atrophic gastritis. 相似文献
194.
Donati I Coslovi A Gamini A Skjåk-Braek G Vetere A Campa C Paoletti S 《Biomacromolecules》2004,5(1):186-196
Galactose moieties have been introduced on the uronic groups of alginates from different sources via an N-glycosidic bond, thus affecting the net charge on the polymer chain. The modified polymers have been analyzed by means of viscosity and of high-performance size-exclusion chromatography combined with refractive index multiple angle laser light scattering (HPSEC-RI-MALLS) measurements. The latter technique enabled us to determine the molecular weight of the modified polymers, proving that the synthetic procedure did not affect the chemical integrity of the chain. The intrinsic viscosity and the radius of gyration data showed that the hydrodynamic properties of the polymer chain varied with the degree and the pattern of substitution. In the presence of a relatively low galactose content (up to 19%), a decrease of the hydrodynamic dimensions of the coil was experienced, while on increasing the degree of substitution (especially on GG diads) a re-extension of the chain was discovered. Measurements of intrinsic viscosity at different values of the degree of dissociation have demonstrated that this effect cannot be solely explained by the reduction of the charge density of the polymer. Rather, it implies the occurrence of conformational changes of the chain that are specific to the chemical nature of the site of substitution. These data have been supported by the values of the persistence length of the natural and modified polymers obtained with the Doty-Benoit equation. The chiro-optical properties of the modified polymers studied by means of circular dichroism (CD) spectroscopy confirmed that conformational variations occurred to the polymeric chain upon introduction of galactose residues. 相似文献
195.
The role of aromaticity, exposed surface, and dipole moment in determining protein aggregation rates
Tartaglia GG Cavalli A Pellarin R Caflisch A 《Protein science : a publication of the Protein Society》2004,13(7):1939-1941
The mechanisms by which peptides and proteins form ordered aggregates are not well understood. Here we focus on the physicochemical properties of amino acids that favor ordered aggregation and suggest a parameter-free model that is able to predict the change of aggregation rates over a large set of natural sequences. Furthermore, the results of the parameter-free model correlate well with the aggregation propensities of a set of peptides designed by computer simulations. 相似文献
196.
Tait A Luppi A Franchini S Preziosi E Parenti C Buccioni M Marucci G Leonardi A Poggesi E Brasili L 《Bioorganic & medicinal chemistry letters》2005,15(4):1185-1188
A series of new 1,2,4-benzothiadiazine derivatives with an arylpiperazine mojety linked at position 3 of the heterocyclic ring were synthesized and assessed for their pharmacological profiles at alpha(1)-adrenoceptor subtypes (alpha(1A), alpha(1B) and alpha(1D)) by functional experiments and by in vitro binding studies at human cloned 5-HT(1A) receptor. Compound 1 was identified as a novel alpha(1D) antagonist (pK(b)alpha(1D)=7.59; alpha(1D)/alpha(1A)>389; alpha(1D)/alpha(1B)=135) with high selectivity over 5-HT(1A) receptor (5-HT(1A)/alpha(1D)<0.01), while compound 6, a 3,4-dihydro-derivative, was characterized as a novel 5-HT(1A) receptor ligand, highly selective over alpha(1D)-adrenoceptor subtype (pK(i)5-HT(1A)=8.04; 5-HT(1A)/alpha(1D)=1096). Further pharmacological studies demonstrated that 6 is a partial agonist at 5-HT(1A) receptor (E(max)=23, pD(2)=6.92). 相似文献
197.
Venkatesan AM Grosu GT Failli AA Chan PS Coupet J Saunders T Mazandarani H Ru X 《Bioorganic & medicinal chemistry letters》2005,15(22):5003-5006
Synthesis and structure-activity relationships (SAR) of arginine vasopressin (AVP) receptor modulators are described. Potent and selective compounds are prepared when the amide linkage connecting rings A and B of VPA-985 is replaced with a bond, CO, -O-, -S-, or -SO2- bond. 相似文献
198.
Fanelli D Henshaw M Cervo R Turillazzi S Queller DC Strassmann JE 《Journal of evolutionary biology》2005,18(5):1362-1367
Parasites that exploit the parental behaviour of several host species may be selected to form distinct host-specific genetic lineages. This process is well documented in bird brood parasites, but not in insect social parasites. Polistes atrimandibularis is the only paper-wasp social parasite known to exploit four host species. It does not form genetically distinct host races according to analyses based on microsatellite loci. Also, there were no size-matching between parasites and host species. Instead, P. atrimandibularis queens seemed to be successful as parasites in this population only when they originated from nests of P. dominulus, the largest species. The other host species are a sink for P. atrimandibularis since adult females emerging from those nests appear too small to usurp colonies themselves. Traits that may help P. atrimandibularis infiltrate multiple species may include its nonaggressive usurpation tactics and its ability to acquire host cuticular hydrocarbon recognition labels. 相似文献
199.
In multiple-foundress nests of the wasp Polistes dominulus, dominance hierarchies are established among foundresses, and only the dominant (=alpha) individual lays eggs. The alpha female can be distinguished from subordinate females and workers on the basis of the proportions of some hydrocarbons present on the cuticle, suggesting that chemical signaling of her reproductive status could occur. P. dominulus is also the host species of the obligate social parasite Polistes sulcifer. After aggressively usurping host colonies and behaviorally replacing the host alpha female, parasites are characterized by a change in the proportions of their cuticular hydrocarbons to match that of the host cuticular profile at both species and colony levels. In the current study, we demonstrate that P. sulcifer queens also modify their cuticular hydrocarbon proportions after usurpation to match that of the host alpha female. Parasite females, therefore, acquire the dominant rank in host colonies both reproductively and chemically by mimicking the typical alpha profile of the host. Parasite females were not able to fully inhibit ovary development in host foundresses, and 10 days after usurpation, parasites, alpha and beta foundresses show similar chemical profiles and ovarian development. 相似文献
200.
Lorenzo Guglielminetti Héctor Abel Busilacchi Amedeo Alpi 《Journal of plant research》2000,113(2):185-192
α -amylase as well as other enzymes involved in starch degradation under anoxia. Carbohydrates resulting from starch breakdown
allow maize caryopses to avoid sugar starvation. Most interestingly, this correlates well with the ability of maize caryopses
to sustain relatively prolonged anaerobiosis, in agreement with the hypothesis linking carbohydrate availability to anoxia
tolerance.
Received 25 September 1999/ Accepted in revised form 24 February 2000 相似文献