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971.
972.
Total 427 yeast strains from seawater, sediments, mud of salterns, guts of the marine fish, and marine algae were obtained.
After inulinase activity of the yeast cultures was estimated, we found that four strains (OUC1, G7a, OUC2, and G7a1) of the
marine yeasts grown in the medium with inulin could secrete a large amount of inulinase into the medium. The results of routine
identification and molecular methods show that they belong to Pichia guilliermondii OUC1, Cryptococcus aureus G7a, Yarrowia lipolytica OUC2, and Debaryomyces hansenii G7a1, respectively. The optimal pHs of inulinase activity produced by them were 6.0, 5.0, 5.0, and 5.0, respectively, while
the optimal temperatures of inulinase activity produced by them were 60°, 50°, 60°, and 50°C, respectively. A large amount
of monosaccharides and a trace amount of oligosaccharides were detected after the hydrolysis by the crude inulinase produced
by P. guilliermondii OUC1, indicating that the crude inulinase had a high exoinulinase activity while a large amount of monosaccharides and oligosaccharides
were detected after inulin hydrolysis by the crude inulinase produced both by C. aureus G7a and D. hansenii G7a1. However, no monosaccharides and disaccharides were detected after inulin hydrolysis by the crude inulinase produced
by Y. lipolytica OUC2, suggesting that the crude inulinase had no exoinulinase activity. 相似文献
973.
Hamada H Abe Y Nagane R Fang YY Lewis MA Long EC Chikira M 《Journal of inorganic biochemistry》2007,101(10):1529-1536
DNA fiber EPR was used to investigate the DNA binding stabilities and orientations of Cu(II).Gly-Gly-His-derived metallopeptides containing D- vs. L-amino acid substitutions in the first peptide position. This examination included studies of Cu(II).D-Arg-Gly-His and Cu(II).D-Lys-Gly-His for comparison to metallopeptides containing L-Arg/Lys substitutions, and also the diastereoisomeric pairs Cu(II).D/L-Pro-Gly-His and Cu(II).D/L-Pro-Lys-His. Results indicated that L-Arg/Lys to D-Arg/Lys substitutions considerably randomized the orientation of the metallopeptides on DNA, whereas the replacement of L-Pro by D-Pro in Cu(II).L-Pro-Gly-His caused a decrease in randomness. The difference in the extent of randomness observed between the D- vs. L-Pro-Gly-His complexes was diminished through the substitution of Gly for Lys in the middle peptide position, supporting the notion that the epsilon-amino group of Lys triggered further randomization, likely through hydrogen bonding or electrostatic interactions that disrupt binding of the metallopeptide equatorial plane and the DNA. The relationship between the stereochemistry of amino acid residues and the binding and reaction of M(II).Xaa-Xaa'-His metallopeptides with DNA are also discussed. 相似文献
974.
Wang B Feng WY Wang M Shi JW Zhang F Ouyang H Zhao YL Chai ZF Huang YY Xie YN Wang HF Wang J 《Biological trace element research》2007,118(3):233-243
It has been demonstrated that inhaled fine (d < 2.5 μm) and ultrafine (d < 100 nm) particles produce more severe toxicity than coarse particles. Some recent data support the concept that the central
nervous system (CNS) may be a target for the inhaled fine particulates. This work describes initial observation of the transport
of intranasally instilled fine ferric oxide (Fe2O3) particles in animal brain. The iron micro-distribution and chemical state in the mice olfactory bulb and brain stem on day
14 after intranasal instillation of fine Fe2O3 particle (280 ± 80 nm) suspension at a single dose of 40 mg/kg body weight were analyzed by synchrotron radiation x-ray fluorescence
and x-ray absorption near-edge structure (XANES). The micro-distribution map of iron in the olfactory bulb and brain stem
shows an obvious increase of Fe contents in the olfactory nerve and the trigeminus of brain stem, suggesting that Fe2O3 particles were possibly transported via uptake by sensory nerve endings of the olfactory nerve and trigeminus. The XANES
results indicate that the ratios of Fe (III)/Fe (II) were increased in the olfactory bulb and brain stem. The further histopathological
observation showed that the neuron fatty degeneration occurred in the CA3 area of hippocampus. Such results imply an adverse
impact of inhalation of fine Fe2O3 particles on CNS. 相似文献
975.
976.
Cultivation-based and molecular approaches were used to characterize the phylogenetic composition and structure of the microbial community in an extremely acidic (pH 2.0) acid mine drainage (AMD) associated with Pb/Zn mine tailings that were undergoing vigorous acid generation. Acidophilic bacteria were isolated and enumerated on solid media, and were found to be restricted to isolates related to Acidithiobacillus ferrooxidans and Acidiphilium cryptum. By contrast, cloning and phylogenetic analysis of 16S rRNA genes revealed that, although low in total taxonomically distinct groups, the tailings AMD ecosystem harbored a wide range of phylogenetically diverse microbes. Of the 141 clones examined, 104 were phylogenetically affiliated with the recently discovered, iron-oxidizing Leptospirillum group III within the Nitrospira. It thus appears that iron serves as the major electron donor in this habitat. Thirty clones were affiliated with the Proteobacteria, half of which belonged to organisms related to Alphaproteobacteria species capable of ferric iron reduction. Other clones were grouped with Betaproteobacteria and Gammaproteobacteria (six clones each), and even with Deltaproteobacteria (three clones), a subdivision with anaerobic sulfate or metal (iron) reduction as the predominant physiological trait of its members. Finally, four clones were clustered within the Firmicutes and the Acidobacteria. Approximately half of the sequence types representing the majority of the total clones fell into lineages that are poorly represented by cultured organisms or have thus far been represented by only a few environmental sequences. Thus, the present study extends our knowledge of the biodiversity of microorganisms populating highly acidic AMD environments. 相似文献
977.
It is widely accepted that the APD (action potential duration) restitution plays a key role in the initializing and maintaining of the reentry arrhythmias. The Luo-Rudy II models paced with different protocols showed that the current APD had a complex relation with the previous APDs and diastole intervals (DIs). This relation could not be accurately described by a single exponential function. We used an artificial neural network to formularize this relation. The results suggested that back-propagation (BP) network could predict the current APD from the information of the first three previous beats. This would help provide a target for potential anti-arrhythmic therapies. 相似文献
978.
Four iridal-type triterpenoids, two of which were new compounds, have been isolated from rhizomes of Iris tectorum Maxim. Their structures were determined by 1D and 2D NMR spectroscopy and ESI-MS spectrometry. The compounds were identified as the iritectols A and B, and the known iridobelamal A and isoiridogermanal. The presence of epoxide and tetrahydrofuran functions are not common in previously isolated iridal-type triterpenoids. 相似文献
979.
Summary. Flow cytometric analysis of mitochondria isolated from maize leaves revealed two distinct rhodamine-123-stained fluorescence
populations distinguishable by their main fluorescence channel. Further microscopic observation of mitochondria stained with
Janus Green B and rhodamine-123 revealed the occurrence of differently sized mitochondrial particles. It was shown by pulsed-field
gel electrophoresis that the DNA from the isolated mitochondria ranged in size from 45 to 100 kb. These results suggest that
different types of mitochondria with different physiological status, mass, and genomic DNA size probably coexist and carry
out different physiological functions throughout the whole process of maize leaf growth and development.
Correspondence: Lijia Li, Key Laboratory for Plant Developmental Biology of the Ministry of Education, College of Life Sciences,
Wuhan University, Wuhan 430072, People’s Republic of China. 相似文献
980.
Directed evolution for increased chitinase activity 总被引:3,自引:0,他引:3
Fan Y Fang W Xiao Y Yang X Zhang Y Bidochka MJ Pei Y 《Applied microbiology and biotechnology》2007,76(1):135-139
Directed evolution through DNA shuffling and screening was used to enhance the catalytic ability of a fungal, Beauveria bassiana, chitinase, Bbchit1. The Bbchit gene was first linked to various prokaryotic signal sequences and expressed in Escherichia coli. The signal peptide, PelB, from Erwinia carotovora resulted in greatest chitinase secretion into broth. The nucleotide sequence expressing PelB signal peptide was then incorporated
into an E. coli vector to express Bbchit1 variants generated by three rounds of DNA shuffling. A Bbchit1 library with 150,000 variants was constructed with a nucleotide point mutation frequency of 0.6% and screened for chitinolytic
activity. Two Bbchit1 variants (SHU-1 and SHU-2) were selected that showed increased chitinolytic activity compared to the
wild type. Sequence analysis of these variants revealed mutations in amino acid residues that would not normally be considered
for rational design of improved chitinase activity. The amino acid substitutions occurred outside of the two putative substrate-binding
sites and the catalytic region. 相似文献