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81.
Depaquit J Ferté H Léger N Lefranc F Alves-Pires C Hanafi H Maroli M Morillas-Marquez F Rioux JA Svobodova M Volf P 《International journal for parasitology》2002,32(9):1123-1131
An intraspecific study on Phlebotomus sergenti, the main and only proven vector of Leishmania tropica among the members of the subgenus Paraphlebotomus was performed. The internal transcribed spacer 2 (ITS2) sequences of 12 populations from 10 countries (Cyprus, Egypt, Italy, Lebanon, Morocco, Pakistan, Portugal, Spain, Syria, and Turkey) were compared. Samples also included three species closely related to P. sergenti: Phlebotomus similis (three populations from Greece and Malta), Phlebotomus jacusieli and Phlebotomus kazeruni. Our results confirm the validity of the taxa morphologically characterised, and imply the revision of their distribution areas, which are explained through biogeographical events. At the Miocene time, a migration route, north of the Paratethys sea would have been followed by P. similis to colonise the north of the Caucasus, Crimea, Balkans including Greece and its islands, and western Turkey. Phlebotomus sergenti would have followed an Asiatic dispersion as well as a western migration route south of the Tethys sea to colonise North Africa and western Europe. This hypothesis seems to be well supported by high degree of variation observed in the present study, which is not related to colonisation or to intra-populational variation. Two groups can be individualised, one oriental and one western in connection with ecology, host preferences and distribution of L. tropica. We hypothesise that they could be correlated with differences in vectorial capacities. 相似文献
82.
Whole-Cell versus Total RNA Extraction for Analysis of Microbial Community Structure with 16S rRNA-Targeted Oligonucleotide Probes in Salt Marsh Sediments 总被引:2,自引:1,他引:2 下载免费PDF全文
Marc E. Frischer Jean M. Danforth Michele A. Newton Healy F. Michael Saunders 《Applied microbiology》2000,66(7):3037-3043
rRNA-targeted oligonucleotide probes have become powerful tools for describing microbial communities, but their use in sediments remains difficult. Here we describe a simple technique involving homogenization, detergents, and dispersants that allows the quantitative extraction of cells from formalin-preserved salt marsh sediments. Resulting cell extracts are amenable to membrane blotting and hybridization protocols. Using this procedure, the efficiency of cell extraction was high (95.7% ± 3.7% [mean ± standard deviation]) relative to direct DAPI (4′,6′-diamidino-2-phenylindole) epifluorescence cell counts for a variety of salt marsh sediments. To test the hypothesis that cells were extracted without phylogenetic bias, the relative abundance (depth distribution) of five major divisions of the gram-negative mesophilic sulfate-reducing delta proteobacteria were determined in sediments maintained in a tidal mesocosm system. A suite of six 16S rRNA-targeted oligonucleotide probes were utilized. The apparent structure of sulfate-reducing bacteria communities determined from whole-cell and RNA extracts were consistent with each other (r2 = 0.60), indicating that the whole-cell extraction and RNA extraction hybridization approaches for describing sediment microbial communities are equally robust. However, the variability associated with both methods was high and appeared to be a result of the natural heterogeneity of sediment microbial communities and methodological artifacts. The relative distribution of sulfate-reducing bacteria was similar to that observed in natural marsh systems, providing preliminary evidence that the mesocosm systems accurately simulate native marsh systems. 相似文献
83.
Angela Lombardi Michele Saviano Flavia Nastri Ornella Maglio Marco Mazzeo Carla Isernia Livio Paolillo Vincenzo Pavone 《Biopolymers》1996,38(6):693-703
In the present paper we describe the solution nmr structural analysis and restrained molecular dynamic simulation of the cyclic pentapeptide cyclo-(Pro-Phe-Phe-β-Ala-β-Ala). The conformational analysis carried out in CD3CN and dimethylsulfoxide (DMSO) solutions by nmr spectroscopy was based on interproton distances derived from rotating frame nuclear Overhauser effect spectroscopy spectra and homonuclear coupling constants. A restrained molecular dynamic simulation in vacuo was also performed to build refined molecular models. The molecule is present in both solvent systems as two slowly interconverting conformers, characterized by a cis-trans isomerism around the β-Ala5-Pro1 peptide bond. In CD3CN solution, the conformer with a cis peptide bond is quite similar to that observed in the solid state, while the conformer containing all trans peptide bonds is characterized by an intramolecular hydrogen bond stabilizing a C10- and a C13-ring structure. In DMSO solution, the trans isomer is partly similar to that observed in CD3CN solution while the cis isomer is different from that observed in the solid state. The effect of the solvent in stabilizing different conformations was also investigated in DMSO-CD3CN solvent mixtures. © 1996 John Wiley & Sons, Inc. 相似文献
84.
85.
Proper expression of the replication licensing factor Cdt1 is primarily
regulated post-translationally by ubiquitylation and proteasome degradation.
In a screen to identify novel non-histone targets of histone deacetylases
(HDACs), we found Cdt1 as a binding partner for HDAC11. Cdt1 associates
specifically and directly with HDAC11. We show that Cdt1 undergoes acetylation
and is reversibly deacetylated by HDAC11. In vitro, Cdt1 can be
acetylated at its N terminus by the lysine acetyltransferases KAT2B and KAT3B.
Acetylation protects Cdt1 from ubiquitylation and subsequent proteasomal
degradation. These results extend the list of non-histone acetylated proteins
to include a critical DNA replication factor and provide an additional level
of complexity to the regulation of Cdt1.To maintain genomic integrity, DNA replication must be tightly controlled
to ensure that each portion of the genome replicates once and only once per
cell cycle (reviewed in Ref.
1). Replication licensing
begins by the formation of the prereplication complex at multiple potential
origins of replication. This is established sequentially, with the origin
recognition complex
(ORC)2 proteins
binding first, followed by the recruitment of Cdc6 and Cdt1, which in turn
recruit the MCM2–7 proteins. MCM proteins act as the replicative
helicase. The licensed replication origins are activated by cyclin-dependent
kinases at the start of S phase. Licensing occurs throughout the cell cycle
once S phase is complete.Cdt1 levels fluctuate throughout the cell cycle. It is destabilized at
G1/S transition, and then levels begin to climb again upon S phase
completion. To prevent licensing at inappropriate times, two separate
processes regulate the inactivation or destruction of Cdt1. First, geminin
negatively regulates Cdt1 function by prevention of the association of Cdt1
with MCM2–7 via steric hindrance
(2). Interestingly, geminin
also positively regulates Cdt1 by preventing its ubiquitylation, perhaps by
prevention of its interaction with an E3 ligase. This allows Cdt1 to
accumulate in G2 and M phases, to ensure adequate pools of Cdt1 to
license the next cycle of replication
(3). The ratio of geminin to
Cdt1 likely determines whether geminin positively or negatively regulates Cdt1
(4). Second, Cdt1 is targeted
for proteolysis by two distinct ubiquitin E3 ligases: the SCF-Skp2 complex and
the DDB1-Cul4 complex (5).
Phosphorylation by cyclin A/Cdk2 promotes interaction of Cdt1 with Skp2,
leading to Cdt1 degradation during S phase
(6–8).
In addition, DDB1-Cul4 utilizes proliferating cell nuclear antigen as a
binding platform to contact Cdt1, targeting the destruction of Cdt1 in S phase
or following DNA damage (9,
10). Ubiquitylation by either
of these E3 ligases promotes degradation of Cdt1 by the proteasome.Ubiquitylation occurs primarily (but not exclusively) on the ε-amino
group of lysine residues. Another prominent post-translational modification
that occurs on that residue is acetylation. Acetylation and, correspondingly,
deacetylation can modulate the function and activity of a variety of proteins
(see Ref. 11 for review).
Here, we report that Cdt1 physically interacts with HDAC11, a class IV histone
deacetylase (12,
13), as well as with several
lysine acetyltransferases (KATs). We show that Cdt1 is an acetylated protein
and further show that acetylation protects Cdt1 from ubiquitylation and
subsequent proteasomal degradation. This study uncovers yet another layer of
complexity to the regulation of the critical licensing factor Cdt1. 相似文献
86.
Michele Michelin Vivian M. Benassi Luiz Alberto B. Moraes João A. Jorge Maria de Lourdes T.M. Polizeli 《Carbohydrate research》2010,345(16):2348-2353
An α-amylase produced by Paecilomyces variotii was purified by DEAE-cellulose ion exchange chromatography, followed by Sephadex G-100 gel filtration and electroelution. The α-amylase showed a molecular mass of 75 kDa (SDS-PAGE) and pI value of 4.5. Temperature and pH optima were 60 °C and 4.0, respectively. The enzyme was stable for 1 h at 55 °C, showing a t50 of 53 min at 60 °C. Starch protected the enzyme against thermal inactivation. The α-amylase was more stable in alkaline pH. It was activated mainly by calcium and cobalt, and it presented as a glycoprotein with 23% carbohydrate content. The enzyme preferentially hydrolyzed starch and, to a lower extent, amylose and amylopectin. The Km of α-amylase on Reagen® and Sigma® starches were 4.3 and 6.2 mg/mL, respectively. The products of starch hydrolysis analyzed by TLC were oligosaccharides such as maltose and maltotriose. The partial amino acid sequence of the enzyme presented similarity to α-amylases from Bacillus sp. These results confirmed that the studied enzyme was an α-amylase ((1→4)-α-glucan glucanohydrolase). 相似文献
87.
FOXM1 Transcription Factor: A New Component of Chronic Myeloid Leukemia Stem Cell Proliferation Advantage 下载免费PDF全文
Manuela Mancini Fausto Castagnetti Simona Soverini Elisa Leo Caterina De Benedittis Gabriele Gugliotta Gianantonio Rosti Luana Bavaro Sara De Santis Cecilia Monaldi Margherita Martelli Maria Alessandra Santucci Michele Cavo Giovanni Martinelli 《Journal of cellular biochemistry》2017,118(11):3968-3975
88.
The self‐sufficient P450 RhF expressed in a whole cell system selectively catalyses the 5‐hydroxylation of diclofenac 下载免费PDF全文
Jan M. Klenk Bernd A. Nebel Joanne L. Porter Justyna K. Kulig Shaneela A. Hussain Sven M. Richter Michele Tavanti Nicholas J. Turner Martin A. Hayes Bernhard Hauer Sabine L. Flitsch 《Biotechnology journal》2017,12(3)
P450 monooxygenases are able to catalyze the highly regio‐ and stereoselective oxidations of many organic molecules. However, the scale‐up of such bio‐oxidations remains challenging due to the often‐low activity, level of expression and stability of P450 biocatalysts. Despite these challenges they are increasingly desirable as recombinant biocatalysts, particularly for the production of drug metabolites. Diclofenac is a widely used anti‐inflammatory drug that is persistent in the environment along with the 4'‐ and 5‐hydroxy metabolites. Here we have used the self‐sufficient P450 RhF (CYP116B2) from Rhodococcus sp. in a whole cell system to reproducibly catalyze the highly regioselective oxidation of diclofenac to 5‐hydroxydiclofenac. The product is a human metabolite and as such is an important standard for environmental and toxicological analysis. Furthermore, access to significant quantities of 5‐hydroxydiclofenac has allowed us to demonstrate further oxidative degradation to the toxic quinoneimine product. Our studies demonstrate the potential for gram‐scale production of human drug metabolites through recombinant whole cell biocatalysis. 相似文献
89.
Functional and structural data are reviewed which provide evidence that proton pumping in cytochrome c oxidase is associated with extended allosteric cooperativity involving the four redox centers in the enzyme . Data are also summarized showing that the H+/e- stoichiometry for proton pumping in the cytochrome span of the mitochondrial respiratory chain is flexible. The DeltapH component of the bulk-phase membrane electrochemical proton gradient exerts a decoupling effect on the proton pump of both the bc1 complex and cytochrome c oxidase. A slip in the pumping efficiency of the latter is also caused by high electron pressure. The mechanistic and physiological implications of proton-pump slips are examined. The easiness with which bulk phase DeltapH causes, at least above a threshold level, decoupling of proton pumping indicates that for active oxidative phosphorylation efficient protonic coupling between redox complexes and ATP synthase takes place at the membrane surface, likely in cristae, without significant formation of delocalized DeltamuH+. A role of slips in modulating oxygen free radical production by the respiratory chain and the mitochondrial pathway of apoptosis is discussed. 相似文献
90.
Why do curly tail lizards (genus Leiocephalus) curl their tails? An assessment of displays toward conspecifics and predators 下载免费PDF全文
Bonnie K. Kircher Michele A. Johnson 《Ethology : formerly Zeitschrift fur Tierpsychologie》2017,123(5):342-347
Animal display behaviors are used to convey specific messages to other animals, including potential mates, rivals, and predators. However, because these different types of interactions can be mediated by a single behavioral display, or conversely, multiple signals can be used to convey one specific message, interpretation of any particular behavioral display can be difficult. Leiocephalus lizards (i.e., curly tails) provide an excellent opportunity to study the use of display behaviors across multiple contexts. Previous research has demonstrated that the use of tail curling in these lizards is associated with predation risk, but less is known regarding the use of this behavior in social interactions with conspecifics. The goal of this study was to determine the extent to which tail curling display behavior is used to mediate both social and predatory interactions in two species, Leiocephalus barahonensis and L. carinatus. We found that in lizards of both species, tail curling was used in interactions with both conspecifics and potential (human) predators. However, tail curl intensity did not differ between lizards involved in social encounters and solitary lizards, although L. barahonensis lizards performed more headbobs during social than non‐social observations. Further, L. carinatus lizards exhibited greater intensity of tail curling upon fleeing from a human predator than during observations in which individuals interacted with conspecifics, and lizards that exhibited tighter tail curls fled from predators for a longer distance. Finally, tail curl intensity was not correlated with headbob displays in either species, suggesting that these two components of display communicate different information. Our results suggest that tail curling displays, while consistently a component of interactions with potential predators, are not a necessary component of social interactions. These data contribute to a more complete understanding of how and why visual signals evolve for use in communication across multiple contexts. 相似文献