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101.
Hu X Fukutani A Liu X Kimbara K Kawai F 《Applied microbiology and biotechnology》2007,73(6):1407-1413
Two bacterial consortia growing on a random copolymer of ethylene glycol and propylene glycol units were obtained by enrichment
cultures from various microbial samples. Six major strains included in both consortia were purified and identified as Sphingomonads,
Pseudomonas sp. and Stenotrophomonas maltophilia. Three of them (Sphingobium sp. strain EK-1, Sphingopyxis macrogoltabida strain EY-1, and Pseudomonas sp. strain PE-2) utilized both PEG and polypropylene glycol (PPG) as a sole carbon source. Four PEG-utilizing bacteria had
PEG dehydrogenase (PEG-DH) activity, which was induced by PEG. PCR products from DNA of these bacteria generated with primers
designed from a PEG-DH gene (AB196775 for S. macrogoltabida strain 103) indicated the presence of a sequence that is the homologous to the PEG-DH gene (99% identity). On the other hand,
five PPG-utilizing bacteria had PPG dehydrogenase (PPG-DH) activity, but the activity was constitutive. PCR of a PPG-DH gene
was performed using primers designed from a polyvinyl alcohol dehydrogenase (PVA-DH) gene (AB190288 for Sphingomonas sp. strain 113P3) because a PPG-DH gene has not been cloned yet, but both PPG-DH and PVA-DH were active toward PPG and PVA
(Mamoto et al. 2006). PCR products of the five strains did not have similarity to each other or to oxidoreductases including PVA-DH.
The paper was edited by a native speaker through American Journal Experts (http://www.journalexperts.com). 相似文献
102.
Escherichia coli dihydrofolate reductase (DHFR) catalyzes the reduction of dihydrofolate to tetrahydrofolate. During the catalytic cycle, DHFR undergoes conformational transitions between the closed (CS) and occluded (OS) states that, respectively, describe whether the active site is closed or occluded by the Met20 loop. The CS→OS and the reverse transition may be viewed as allosteric transitions. Using a sequence-based approach, we identify a network of residues that represents the allostery wiring diagram. Many of the residues in the allostery wiring diagram, which are dispersed throughout the adenosine-binding domain as well as the loop domain, are not conserved. Several of the residues in the network have been previously shown by NMR experiments, mutational studies, and molecular dynamics simulations to be linked to equilibration conformational fluctuations of DHFR. To further probe the nature of events that occur during conformational fluctuations, we use a self-organized polymer model to monitor the kinetics of the CS→OS and the reverse transitions. During the CS→OS transition, coordinated changes in a number of residues in the loop domain enable the Met20 loop to slide along the α-helix in the adenosine-binding domain. Sliding is triggered by pulling of the Met20 loop by the βG-βH loop and the pushing action of the βG-βH loop. The residues that facilitate the Met20 loop motion are part of the network of residues that transmit allosteric signals during the CS→OS transition. Replacement of M16 and G121, whose Cα atoms are about 4.3 Å in the CS, by a disulfide cross-link impedes that CS→OS transition. The order of events in the OS→CS transition is not the reverse of the forward transition. The contact Glu18-Ser49 in the OS persists until the sliding of the Met20 loop is nearly complete. The ensemble of structures in the transition state in both the allosteric transitions is heterogeneous. The most probable transition-state structure resembles the OS (CS) in the CS→OS (OS→CS) transition, which is in accord with the Hammond postulate. Structures resembling the OS (CS) are present as minor (∼ 1-3%) components in equilibrated CS (OS) structures. 相似文献
103.
A new coordination polymer, [Zn2(mal)(1,10-phen)Cl]n (1), (mal = malate, 1,10-phenanthroline), has been synthesized with malic acid and fumaric acid which are generated from maleic acid under hydrothermal reactions. At about the same condition, we get [Cd(fma)(2,2′-bpy)(H2O)]n (2) (fma = fumarate, 2,2′-bpy=2, 2′-bipyridine). The diverse products illustrate that the carbon-carbon doublebond of the maleic acid has two kinds of reaction trends under different conditions. Complex 1, which displays a two-dimensional (4, 8) lattice-type network, is formed from Zn and maleic through the addition reaction with water molecule. If the Zn is changed by Cd, at the same reaction condition with 1, a two-dimensional supramolecular network complex 2 is formed through the conformation transform reaction. To our knowledge, a lot of coordination polymers have been constructed from malic acid and fumaric acid directly; however, these kinds of complexes have seldom been synthesized from maleic acid under hydrothermal reaction. As is known, the rigid carbon-carbon double bond makes maleic acid lead to some unique structural features which the saturated aliphatic acid does not possess. To illustrate this clearly, a simple one dimensional complex 3, [Cd(glut)(1,10-phen)(H2O)]n (glut = glutarate), is synthesized. Furthermore, complex 1 and complex 3 exhibit intense photoluminescent property at room temperature. 相似文献
104.
Two isothiocyanate coordination polymers constructed from the conformationally flexible tethering ligand 3,3′-bipyridine (3,3′-bpy) and divalent metal cations have been prepared and characterized via single crystal X-ray diffraction, infrared spectroscopy and elemental analysis. [Co(NCS)2(3,3′-bpy)2] (1), wherein the isothiocyanate ligands are coordinated in a trans fashion, manifests stacked two-dimensional (2-D) rhomboid grid layered motifs. In contrast, [Ni(NCS)2(3,3′-bpy)2] (2) possesses a doubly interpenetrated adamantoid three-dimensional (3-D) network despite the presence of trans isothiocyanate ligands. Thus, a metal cation-based control of coordination polymer dimensionality has been revealed in this system, reflective of different donor dispositions allowed by the conformational flexibility of the exobidentate 3,3′-bpy ligand. The 3-D framework of 2 decomposes at a temperature ∼40 °C higher than the 2-D network of 1. 相似文献
105.
Ya-Qiong Gong Jiu-Tong Chen Ming-Yan Wu You-Gui Huang Fei-Long Jiang 《Inorganica chimica acta》2007,360(7):2207-2214
Two new 2D coordination polymers, [Ag4(μ-4,4′-bpp)3(1,3-bdc)2]n · 2nH2O (1) and [Ag(μ-4,4′-bpp)2ClO4]n(2) (4,4′-bpp = 2,2′-bis(4-pyridylmethyleneoxy)-1,1′-biphenylene; 1,3-bdc = 1,3-benzenedicarboxylate) have been synthesized using three-layer diffusion methods. Single-crystal X-ray analyses reveal that they are both extended grid networks of the (4,4) topology. In complex 1, a chain built by Ag(I) centers with T-shaped and linear geometries is further connected by the interesting ligand-unsupported Ag?Ag interactions as well as the conjugated π systems to form an interdigitated 2-D coordination network. The corrugated (4,4) sheets of 2 are packed in the ab planes and stacked along the c direction with the anions occupying the gaps in the squares. 相似文献
106.
A new lanthanum ethylenediaminetetraacetate (EDTA) coordination polymer, {[La(EDTA)(H2O)]2}n (EDTA3− = [(CH2N)2(CH2COOH)(CH2COO−)3]), was hydrothermally prepared from LaCl3 solution and ethylenediaminetetracetic acid at 448 K. The compound was characterized by elemental analysis, FTIR, TG-DTA, and X-ray crystallography. The structure consists of ladder-like chains of [La(EDTA)(H2O)]2 dimers bridged by O-C-O groups. Hydrothermal method successfully reduced the high number of La-aqua coordinations in known lanthanum EDTA to one giving rise to relatively compact structure. It has high thermal stability up to 550 K. Every EDTA ligand with COOH group is involved in eight La-O(N) bonds to three nine-coordinated La centers. 相似文献
107.
Tianle Zhang Changpeng Ji Dongshuang Hu Chunguang Chen 《Inorganica chimica acta》2007,360(5):1609-1615
A new dimeric silver(I) complex [Ag(PhPPy2)(CH3CN)]2(ClO4)2 (1) (PhPPy2 = bis(2-pyridyl)phenylphosphine) was synthesized by a direct reaction of [Ag(CH3CN)4]ClO4 with ligand PhPPy2. X-ray crystallographical studies revealed that in 1, two silver atoms are bridged by two PhPPy2 ligands and bonded to each other. Each Ag(I) adopts a distorted trigonally bi-pyramidal geometry, and axially coordinated acetonitrile molecules are collinear with two silver atoms. By using 1 as a building block precursor, a 1D coordination polymer, [Ag2(PhPPy2)2(1,3,5-C6H3(CO2)2(CO2H))]∞ (2) was prepared by replacing axially coordinated acetonitrile molecules in 1 with two carboxylate groups of a bridging ligand, 1,3,5-benzenetricarboxylate. In solid state, linear polymeric chains are oriented parallel to each other and interestingly interact by hydrogen bonding through their carboxylic/carboxylate groups to construct a novel wave-shaped 2D network. Both 1 and 2 exhibit similar photoluminescent properties in solid state at room temperature. 相似文献
108.
Synthesis and characterization of metal ion imprinted nano-porous polymer for the selective recognition of copper 总被引:1,自引:0,他引:1
Baghel A Boopathi M Singh B Pandey P Mahato TH Gutch PK Sekhar K 《Biosensors & bioelectronics》2007,22(12):3326-3334
Selective recognition of metal ions utilizing metal ion-imprinted polymers (MIIPs) received much importance in diverse fields owing to their high selectivity for the target metal ions. In the present study, a copper ion imprinted polymer was synthesized without an additional complexing ligand or complex with a broad aim to avoid the conventional extra metal ion complexing ligand during the synthesis of MIIP. The complete removal of the copper metal ion from the MIIP was confirmed by AAS and SEM–EDX. SEM image of the MIIP exhibited nano-patterns and it was also found to be entirely different from that of non-imprinted polymer and polymer with copper metal ions. BET surface area analysis revealed more surface area (47.96 m2/g) for the Cu(II)-MIIP than non-imprinted control polymer (41.43 m2/g). TGA result of polymer with copper metal ion indicated more char yield (18.41%) when compared to non-imprinted control polymer (8.3%) and Cu(II)-MIIP (less than 1%). FTIR study confirmed the complexation between Cu(II)-MIIP and Cu(II) metal ion through carbonyl oxygen of acryl amide. The Cu(II)-MIIP exhibited an imprinting efficiency of 2.0 and it was showing 8% interference from a mixture of Zn, Ni and Co ions. A potentiometric ion selective electrode devised with Cu(II)-MIIP showed more potential response for Cu(II) ion than that was fabricated from non-imprinted polymer. 相似文献
109.
Molecularly imprinted polymer films for reflectometric interference spectroscopic sensors 总被引:2,自引:0,他引:2
Belmont AS Jaeger S Knopp D Niessner R Gauglitz G Haupt K 《Biosensors & bioelectronics》2007,22(12):3267-3272
Reflectometric interference spectroscopic measurements were performed on molecularly imprinted polymer (MIP) films with the herbicide atrazine as the template molecule. A conventional imprinting protocol was used relying on non-covalent interactions between the functional monomers and the template. The MIPs were deposited on glass transducers by two different methods: spin-coating followed by in situ polymerization of thin films of monomers containing a sacrificial polymeric porogen, and autoassembly of MIP nanoparticles with the aid of an associative linear polymer. Reproducible results were obtained upon measurements of atrazine solutions in toluene with both films. Atrazine concentrations as low as 1.7 ppm could be detected with the autoassembled particle film. No or very little analyte adsorption was observed onto non-imprinted control films made by spin-coating and by particle assembly, respectively. We believe that these MIP layers in combination with the general reflectrometric transduction scheme could be a versatile sensing tool for the detection of environmentally important and other analytes. 相似文献
110.
A heparin/polypyrrole (PPy) composite, an electrical conducting polymer, was designed to enhance the interactions between
a gold-coated matrix and nerve cells, with the cell (PC12 cells) interactions investigated under different conditions, both
with and without electrical stimulation. The heparin concentration in the composites increased with increasing current density
under the preparation condition, indicating that the heparin concentration in the composite could be controlled by managing
the current density. Optical imaging showed that PC12 cells well attached to the PPy surfaces covered with heparin, but were
poorly interacted to PPy surfaces without the heparin and gold coated matrix. The neurite length of the PC12 cells on the
surfaces with an electrical stimulation (100 mV for 1h) significantly increased, with a median length of 77.5 μm; whereas,
that without electrical stimulation was 10∼20 μm. Therefore, the heparin/polypyrrole (PPy) composite may provide insight for
the development of an ideal nerve guidance channel. 相似文献