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101.
C. de Julián Fernández C. Sangregorio C. Innocenti G. Mattei P. Mazzoldi 《Inorganica chimica acta》2008,361(14-15):4138-4142
The magnetic properties of Co–Ni alloys nanoparticles with composition Co80Ni20 and Co50Ni50 and dispersed in a silica matrix are investigated. The effective magnetic anisotropies are evaluated from the analysis of the temperature dependence of the zero-field-cooling magnetizations and from the hysteresis loops at 3 K considering the coherent rotation model. The results show that, on the contrary of what expected, Co80Ni20 nanoparticles have smaller anisotropy than the Co50Ni50 one showing that the magnetic properties of the system can be tuned from soft to hard by simply adjusting the alloy composition. This behaviour can be explained on the basis of the different size and composition of the two systems. Moreover we found that the evaluation of the anisotropy constant depends on the experimental method adopted due to the modifications by interparticle dipolar interactions of the reversal process. 相似文献
102.
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104.
Gonzalez MA Alvarez Mdel L Pisani GB Bernal CA Roma MG Carrillo MC 《Biological trace element research》2007,116(3):329-348
We have shown that aluminum (Al) induces cholestasis associated with multiple alterations in hepatocellular transporters involved
in bile secretory function, like Mrp2. This work aims to investigate whether these harmful effects are mediated by the oxidative
stress caused by the metal. For this purpose, the capability of the antioxidant agent, vitamin E, to counteract these alterations
was studied in male Wistar rats. Aluminum hydroxide (or saline in controls) was administered ip (27 mg/kg body weight, three
times a week, for 90 d). Vitamin E (600 mg/kg body weight) was coadministered, sc. Al increased lipid peroxidation (+50%)
and decreased hepatic glutation levels (-43%) and the activity of glutation peroxidase (-50%) and catalase (-88%). Vitamin
E counteracted these effects total or partially. Both plasma and hepatic Al levels reached at the end of the treatment were
significantly reduced by vitamin E (-40% and -44%, respectively;p< 0.05). Al increased 4 times the hepatic apoptotic index, and this effect was fully counteracted by vitamin E. Bile flow
was decreased in Al-treated rats (-37%) and restored to normality by vitamin E. The antioxidant normalized the hepatic handling
of the Mrp2 substrates, rose bengal, and dinitrophenyl-S-glutathione, which was causally associated with restoration of Mrp2
expression. Our data indicate that oxidative stress has a crucial role in cholestasis, apoptotic/necrotic hepatocellular damage,
and the impairment in liver transport function induced by Al and that vitamin E counteracts these harmful effects not only
by preventing free-radical formation but also by favoring Al disposal. 相似文献
105.
Acorn dispersal estimated by radio-tracking 总被引:2,自引:0,他引:2
Bird-dispersed seeds are difficult to track, especially in the case of long-distance dispersal events. To estimate the oak
dispersal distance and the seed shadow generated by the European jay (Garrulus glandarius), we inserted radio-transmitters in 239 acorns, placed them in bird-feeders and then located them by radio-tracking. Using
this methodology we located the exact caching site of 94 Quercus ilex and 54 Q. suber acorns and determined the caching habitat characteristics (vegetation type, distance, spatial distribution). The results
show that: (1) there is no differences in the dispersal distance distribution between the different acorn species or sizes,
(2) dispersal distances range from approximately 3 m up to approximately 550 m (mean = 68.6 m; median = 49.2 m), (3) recently
abandoned fields and forest tracks were the sites preferred by jays to cache acorns, whereas fields and shrublands were avoided
and (4) seed shadows showed acorn aggregation zones (i.e. clusters of caches) close to the feeder as well as isolated caches
at longer distances. The results also suggest that radio-transmitters are a cheap and reliable way to determine seed shadows
and quantify both seed dispersal and post-dispersal seed predation for medium to large seeds. 相似文献
106.
Marcelo R. de Carvalho Flávio A. Bockmann Dalton S. Amorim Carlos Roberto F. Brandão Mário de Vivo José L. de Figueiredo Heraldo A. Britski Mário C. C. de Pinna Naércio A. Menezes Fernando P. L. Marques Nelson Papavero Eliana M. Cancello Jorge V. Crisci John D. McEachran Robert C. Schelly John G. Lundberg Anthony C. Gill Ralf Britz Quentin D. Wheeler Melanie L. J. Stiassny Lynne R. Parenti Larry M. Page Ward C. Wheeler Julián Faivovich Richard P. Vari Lance Grande Chris J. Humphries Rob DeSalle Malte C. Ebach Gareth J. Nelson 《Evolutionary biology》2007,34(3-4):140-143
107.
N-linked glycosylation status of classical swine fever virus strain Brescia E2 glycoprotein influences virulence in swine 总被引:1,自引:0,他引:1
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Risatti GR Holinka LG Fernandez Sainz I Carrillo C Lu Z Borca MV 《Journal of virology》2007,81(2):924-933
E2 is one of the three envelope glycoproteins of classical swine fever virus (CSFV). Previous studies indicate that E2 is involved in several functions, including virus attachment and entry to target cells, production of antibodies, induction of protective immune response in swine, and virulence. Here, we have investigated the role of E2 glycosylation of the highly virulent CSFV strain Brescia in infection of the natural host. Seven putative glycosylation sites in E2 were modified by site-directed mutagenesis of a CSFV Brescia infectious clone (BICv). A panel of virus mutants was obtained and used to investigate whether the removal of putative glycosylation sites in the E2 glycoprotein would affect viral virulence/pathogenesis in swine. We observed that rescue of viable virus was completely impaired by removal of all putative glycosylation sites in E2 but restored when mutation N185A reverted to wild-type asparagine produced viable virus that was attenuated in swine. Single mutations of each of the E2 glycosylation sites showed that amino acid N116 (N1v virus) was responsible for BICv attenuation. N1v efficiently protected swine from challenge with virulent BICv at 3 and 28 days postinfection, suggesting that glycosylation of E2 could be modified for development of classical swine fever live attenuated vaccines. 相似文献
108.
Bacteriophage specific for Campylobacter were isolated from chicken excreta collected from established free-range layer breed stock. Bacteriophage were either propagated on a Campylobacter jejuni host with broad susceptibility to bacteriophage (NCTC 12662) or on Campylobacter isolates from the same samples. Campylobacters were confirmed as being C. jejuni and or C. coli, using a combination of standard biochemical tests and PCR analysis with genus and species specific primers. The bacteriophage displayed differential patterns of susceptibility against reference NCTC strains and contemporary C. jejuni /C. coli isolates from chicken excreta. Electron microscopy demonstrated that the phage possessed icosahedral heads and rigid contractile tails. Pulsed-field gel electrophoresis revealed the bacteriophage genomes to be double stranded DNA in the range of 140 kb in size and the restriction enzyme patterns of the DNAs indicate they are genetically related members of the Myoviridae family. This study showed that Campylobacter bacteriophage could easily be isolated from free-range chickens and form part of their normal microbiological biota of environmentally exposed birds. 相似文献
109.
Most neural communication and processing tasks are driven by spikes. This has enabled the application of the event-driven simulation schemes. However the simulation of spiking neural networks based on complex models that cannot be simplified to analytical expressions (requiring numerical calculation) is very time consuming. Here we describe briefly an event-driven simulation scheme that uses pre-calculated table-based neuron characterizations to avoid numerical calculations during a network simulation, allowing the simulation of large-scale neural systems. More concretely we explain how electrical coupling can be simulated efficiently within this computation scheme, reproducing synchronization processes observed in detailed simulations of neural populations. 相似文献
110.
Plant phenology is in great measure driven by air temperature. To forecast harvest time for ‘Algerie’ loquat accurately, the
growing degree days (GDD) needed from bloom to ripening were determined using data from nine seasons. The methods proposed
by Zalom et al. (Zalom FG, Goodell PB, Wilson LT, Barnett WW, Bentley W, Degree-days: the calculation and use of heat units
in pest management, leaflet no 21373, Division Agriculture and Natural Resources, University of California 10 pp, 1983) were compared as regards their ability to estimate heat summation based on hourly records. All the methods gave remarkably
similar results for our cultivation area, although the double-sine method showed higher performance when temperatures were
low. A base temperature of 3°C is proposed for ‘Algerie’ loquat because it provides a coefficient of variation in GDD among
seasons of below 5%, and because of its compatibility with loquat growth. Based on these determinations, ‘Algerie’ loquat
requires 1,715 GDD from bloom to harvest; under our conditions this heat is accumulated over an average of 159 days. Our procedure
permits the ‘Algerie’ harvest date to be estimated with a mean error of 4.4 days (<3% for the bloom-harvest period). GDD summation
did not prove superior to the use of the number of calendar days for predicting ‘Algerie’ harvest under non-limiting growing
conditions. However, GDD reflects the developmental rate in water-stressed trees better than calendar days. Trees under deficit
irrigation during flower development required more time and more heat to ripen their fruits. 相似文献