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971.
Pangallo D Drahovska H Harichova J Karelova E Chovanova K Aradska J Ferianc P Turna J Timko J 《Antonie van Leeuwenhoek》2008,93(1-2):193-203
The aim of the work was the evaluation of different PCR-based methods to found an appropriate identification and typing strategy
for environmental enterococci. Environmental enterococci were isolated mainly from surface- and waste-waters. Species identification
was provided by combination of phenotypic (Micronaut System, Merlin) and molecular detection methods (fluorescent ITS-PCR,
ddl-PCR, REP-PCR, AFLP). Very similar results were observed among molecular methods, however several discrepancies were recognized
during comparison of molecular and biochemical identification. Seven enterococcal species (E. faecium, E. hirae, E. casseliflavus, E. mundtii, E. faecalis, E. durans and E. gallinarum) were identified within 166 environmental isolates. The results obtained in this work attest the importance of PCR-based
methods for identification and typing of environmental enterococci. The fluorescent ITS-PCR (fITS-PCR) showed the best results
in order to identify the enterococci strains, the method used the automated capillary electrophoresis to separate the PCR
products in a very rapid and precise way. The AFLP method was suitable to identify and characterize the isolates, while the
REP-PCR can be used for species identification. 相似文献
972.
Cytochemical evidence for the leakage of acid phosphatase through ultrastructurally intact lysosomal membranes 总被引:9,自引:0,他引:9
Synopsis Fixation under improper conditions ofin vitro cultivated cells results in an extensive diffusion of the lysosomal enzyme acid phosphatase because of the influence of a low effective osmotic pressure. In the present investigation, advantage was taken of this predictable diffusion in order to establish whether or not leakage of acid phosphatase could take place through ultrastructurally intact lysosomal membranes.In order to reveal small holes in the lysosomal membranes, secondary lysosomes were labelled with thorium dioxide particles, which were presumed to appear free in the cell sap if ruptures in the membranes larger than about Ioo Å were created.The experiments revealed that following the fixation ofin vitro cultivated human glia cells under improper conditions, mitochondria and ground cytoplasm show considerable swelling artifacts, while secondary lysosomes appear to be essentially unaffected. The lysosomes, nevertheless, apparently lost most of their content of acid phosphatase, as judged from enzyme cytochemical studies. These findings indicate that leakage of acid phosphatase from ultrastructurally intact lysosomes is possible. 相似文献
973.
Natural fluctuations in soil microbial communities are poorly documented because of the inherent difficulty to perform a simultaneous analysis of the relative abundances of multiple populations over a long time period. Yet, it is important to understand the magnitudes of community composition variability as a function of natural influences (e.g., temperature, plant growth, or rainfall) because this forms the reference or baseline against which external disturbances (e.g., anthropogenic emissions) can be judged. Second, definition of baseline fluctuations in complex microbial communities may help to understand at which point the systems become unbalanced and cannot return to their original composition. In this paper, we examined the seasonal fluctuations in the bacterial community of an agricultural soil used for regular plant crop production by using terminal restriction fragment length polymorphism profiling (T-RFLP) of the amplified 16S ribosomal ribonucleic acid (rRNA) gene diversity. Cluster and statistical analysis of T-RFLP data showed that soil bacterial communities fluctuated very little during the seasons (similarity indices between 0.835 and 0.997) with insignificant variations in 16S rRNA gene richness and diversity indices. Despite overall insignificant fluctuations, between 8 and 30% of all terminal restriction fragments changed their relative intensity in a significant manner among consecutive time samples. To determine the magnitude of community variations induced by external factors, soil samples were subjected to either inoculation with a pure bacterial culture, addition of the herbicide mecoprop, or addition of nutrients. All treatments resulted in statistically measurable changes of T-RFLP profiles of the communities. Addition of nutrients or bacteria plus mecoprop resulted in bacteria composition, which did not return to the original profile within 14 days. We propose that at less than 70% similarity in T-RFLP, the bacterial communities risk to drift apart to inherently different states. 相似文献
974.
We tested the effects of various types of fatty acids, differing in the degree of saturation and in the cis/trans configuration of the double bond, on the growth and viability of NES2Y cells (a human pancreatic beta-cell line). We found that during a 48-hour incubation period, saturated fatty acids, i.e. palmitic and stearic acids, at a physiologically relevant concentration of 1 mM and higher concentrations induced death of the beta-cells while their counterpart unsaturated fatty acids, i.e. palmitoleic and oleic acids, did not induce cell death at concentrations up to 3 mM. We also found that unsaturated elaidic acid with a trans double bond exerted significant inhibition of growth of the beta-cells at a concentration approximately ten times lower, i.e. 0.1 mM vs. 1 mM, than counterpart oleic acid with a cis double bond. This is the first direct evidence that a trans unsaturated fatty acid is significantly more effective in inhibiting beta-cell growth than a counterpart cis unsaturated fatty acid. Furthermore, we newly demonstrated that beta-cell death induced by saturated fatty acids is related to significant increase of caspase-2 activity (2 to 5-fold increase) but not to caspase-3 activation. The growth-inhibiting effect of saturated fatty acids at concentrations lower than death-inducing concentrations correlates with certain increase of caspase-2 activity. 相似文献
975.
Factors controlling the distribution of vascular and non-vascular epiphytes in the northern Andes 总被引:4,自引:0,他引:4
Jan H. D. Wolf 《Plant Ecology》1994,112(1):15-28
The epiphytic vegetation on host trees along an altitudinal transect on the west slope of the Central Cordillera in Colombia was sampled. Bark-type restricted sampling comprised four full-grown forest trees, not necessarily four species, at altitudinal intervals of c. 200 meters from 1000 to 4130 m a.s.l. and included the canopy. Both vascular and non-vascular epiphytes, the latter often more abundant in the montane rain forest, were included in the analyses. Using a method of direct gradient analysis, canonical correspondence analysis, the variation explained by various environmental variables could be discriminated from a great amount of variation that seemed not related to any ecological factor. To a large extent, the randomness in propagule supply appears to determine the floristic composition on branch/trunk segments. The grouping of relevés in a phytosociological analysis concurred with a clustering of samples in an ordination diagram of the first two extracted constrained axes. The sample scores on these two axes were strongly correlated with the complex variables altitude and height within the host tree. Specialists and generalists with respect to the two variables were defined based on tolerances provided by the canonical correspondence analysis as was the position of species on the gradients involved. Independently from any of the other variables entered, a relation between the epiphytic vegetation and host species was detected, particularly in the case of Brunellia occidentalis, a fast growing tree species of higher altitude. No relation between chemical characteristics of suspended soil in the Upper Montane Rain forest and its supporting species could be demonstrated. 相似文献
976.
Notari S Strammiello R Capellari S Giese A Cescatti M Grassi J Ghetti B Langeveld JP Zou WQ Gambetti P Kretzschmar HA Parchi P 《The Journal of biological chemistry》2008,283(45):30557-30565
In prion disease, the abnormal conformer of the cellular prion protein, PrP(Sc), deposits in fibrillar protein aggregates in brain and other organs. Limited exposure of PrP(Sc) to proteolytic digestion in vitro generates a core fragment of 19-21 kDa, named PrP27-30, which is also found in vivo. Recent evidence indicates that abnormal truncated fragments other than PrP27-30 may form in prion disease either in vivo or in vitro. We characterized a novel protease-resistant PrP fragment migrating 2-3 kDa faster than PrP27-30 in Creutzfeldt-Jakob disease (CJD) brains. The fragment has a size of about 18.5 kDa when associated with PrP27-30 type 1 (21 kDa) and of 17 kDa when associated with type 2 (19 kDa). Molecular mass and epitope mapping showed that the two fragments share the primary N-terminal sequence with PrP27-30 types 1 and 2, respectively, but lack a few amino acids at the very end of C terminus together with the glycosylphosphatidylinositol anchor. The amounts of the 18.5- or 17-kDa fragments and the previously described 13-kDa PrP(Sc) C-terminal fragment relatively to the PrP27-30 signal significantly differed among CJD subtypes. Furthermore, protease digestion of PrP(Sc) or PrP27-30 in partially denaturing conditions generated an additional truncated fragment of about 16 kDa only in typical sporadic CJD (i.e. MM1). These results show that the physicochemical heterogeneity of PrP(Sc) in CJD extends to abnormal truncated forms of the protein. The findings support the notion of distinct structural "conformers" of PrP(Sc) and indicate that the characterization of truncated PrP(Sc) forms may further improve molecular typing in CJD. 相似文献
977.
978.
Forty-six volatile compounds were identified in the secretions from Dufour's gland of worker ants of the species Formica nigricans, F. rufa, and F. polyctena using combined gas chromatography-mass spectrometry and capillary gas chromatography. In both methods the natural volatile material has been driven off excised glands using a precolumn technique.The composition of the secretions from the three species are very similar but there are also some distinct differences, especially between F. nigricans on the one hand and F. rufa and F. polyctena on the other. Straight-chain, saturated hydrocarbons are the quantitatively dominating compounds, with undecane as the largest individual component, followed by tridecane, pentadecane, and heptadecane. Straight-chain, monounsaturated hydrocarbons and methyl-branched, saturated hydrocarbons are also present and a few straight-chain, doubly unsaturated hydrocarbons are present in trace amounts.In the region of lower volatility two isoprenoids identified as all-trans-geranylgeraniol and the corresponding acetate all-trans-geranylgeranyl acetate, have been found together with octadecyl acetate. The relative amounts between these compounds are the main difference between the secretions from the three species. Octadecyl acetate is thus present only in trace amounts in the secretion of F. nigricans.In addition to the compounds mentioned a few aliphatic acetates and alcohols present in small amounts have been identified.The secretions are thought to have many functions which are reflected in their complex composition. This is discussed in comparison with results from other formicine ants. The species specificity in the composition of the secretion from Dufour's gland and the taxonomic value of this specificity are also discussed. 相似文献
979.
980.
Frequent Occurrence of Human-Associated Microsporidia in Fecal Droppings of Urban Pigeons in Amsterdam, The Netherlands 下载免费PDF全文
Aldert Bart Ellen M. Wentink-Bonnema Edou R. Heddema Jan Buijs Tom van Gool 《Applied microbiology》2008,74(22):7056-7058
Human-associated microsporidia were frequently observed in fecal samples of 331 feral pigeons in Amsterdam, The Netherlands, obtained during high- and low-breeding periods. Thirty-six of 331 samples (11%) contained the human pathogens Enterocytozoon bieneusi (n = 18), Encephalitozoon hellem (n = 11), Encephalitozoon cuniculi (n = 6), and Encephalitozoon intestinalis (n = 1); 5 samples contained other microsporidia. Pigeon feces can be an important source of human microsporidian infection. 相似文献