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141.
Anish Khan Aftab Aslam Parwaz Khan Abdullah M. Asiri Malik Abdul Rub Mohammed M. Rahman Sulaiman Ab. Ghani 《Mikrochimica acta》2014,181(9-10):1049-1057
A composite was prepared from copper and graphene oxide (Cu-GO) by in-situ chemical reduction of a mixture containing GO and Cu(II) ions with potassium borohydride. The morphology and structure of the composite were confirmed by various physicochemical techniques. The materials were used in a tyrosinase-based microbiosensor where the enzyme is immobilized in a biocompatible matrix consisting of poly(ortho-phenylene diamine) and Cu-GO. The composite was deposited on the surface of an 8-μm thick carbon fiber microelectrode. The role of each component in the sensing layer was systematically investigated with respect to the analytical performance of the system. In its optimal configuration, the biosensor demonstrated (a) a sensitivity of 6.1?±?3 nA mM-1 dopamine (DA), (b) a linear response to DA (with a Michaelis-Menten constant of 0.29?±?0.03 mM), (c) good selectivity over ascorbic acid and uric acid, and (d) a high blocking capacity (112.2?±?2 mM) for ascorbic acid. Figure
Poly(o-phenylenediamine) electropolymerized carbon fiber electrode with sensitivity towards dopamine (DA) is 6.1?±?3 nA mM?1 supported by Cu-GO. The linear range for DA is 0.29?±?0.03 mM with 0.033 μM LOD and fast response time of <8 s with ascorbic acid blocking capacity of 112.2?±?2 mM AA. Studies on different ratio of Glu/Tyr revealed that 10:3 gave best overall response. 相似文献
142.
Flavones were prepared using a one-pot procedure starting from the corresponding 2′-hydroxyacetophenones. The latter were treated with 3 equiv of aroyl chloride in wet K2CO3/acetone (1% w/w water) to afford a good yield of flavone and a smaller amount of 3-aroylflavone. Evidence was obtained that the reaction proceeds via a triketone intermediate. When the reactants were heated in 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) and pyridine, the 3-aroylflavone was obtained exclusively. Use of a stoichiometric amount of aroyl chloride afforded only the corresponding flavone. 相似文献
143.
Pathways for degradation of lignin in bacteria and fungi 总被引:5,自引:0,他引:5
Lignin is a heterogeneous aromatic polymer found as 10-35% of lignocellulose, found in plant cell walls. The bio-conversion of plant lignocellulose to glucose is an important part of second generation biofuel production, but the resistance of lignin to breakdown is a major obstacle in this process, hence there is considerable interest in the microbial breakdown of lignin. White-rot fungi are known to break down lignin with the aid of extracellular peroxidase and laccase enzymes. There are also reports of bacteria that can degrade lignin, and recent work indicates that bacterial lignin breakdown may be more significant than previously thought. The review will discuss the enzymes for lignin breakdown in fungi and bacteria, and the catabolic pathways for breakdown of the β-aryl ether, biphenyl and other components of lignin in bacteria and fungi. The review will also discuss small molecule phenolic breakdown products from lignin that have been identified from lignin-degrading microbes, and includes a bioinformatic analysis of the occurrence of known lignin-degradation pathways in Gram-positive and Gram-negative bacteria. 相似文献
144.
Tae Kyu Kim Euh Duck Jeong Chae Young Oh Min Seob Shin Jong-Pil Kim Ok-Sang Jung Hongsuk Suh Fazlur Rahman Nawaz Khan Myung Ho Hyun Jong Sung Jin 《Chemical Papers》2011,65(6):863-872
A series of neutral gelators and cationic amphiphiles derived from 1,2 diphenylethylenediamine (I) and 1,2-cyclohexanediamine (II) was synthesised. Helical silica nanotubes were prepared utilising these organic gelators through sol-gel polycondensation
of tetraethoxy silane, (TEOS-silica source). Right- and left-handed helical nanotubes respectively were obtained from a 1:
1 mass mixture of optically active, (1S,2S)-III-(1S,2S)-V neutral gelator and (1S,2S)-IV-(1S,2S)-VI cationic amphiphile and a 1: 1 mass mixture of optically active, (1R,2R)-III-(1R,2R)-V neutral gelator and (1R,2R)-IV-(1R,2R)-VI cationic amphiphile, indicating that the handedness of the helical nanotubes varied with the change in the neutral gelator
precursors used. The nanotubes were characterised by SEM images. 相似文献
145.
Salwa Meredith Hashim Abdul Rahman Mohamed Subhash Bhatia 《Journal of Sol-Gel Science and Technology》2011,59(3):505-512
Perovskite-type La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF6428) thin-film membrane prepared by modified Pechini sol–gel process, was successfully deposited on porous support
of similar composition using dip-coating method. Fine grain and crack-free film with perovskite structure was obtained at
sintering temperature of 800 °C and dwelling time of 60 min. The cross-sectional image indicated that LSCF6428 thin-film membrane
coated on the porous support showed excellent adhesion to the support with uniform thickness. The minimum dense layer thickness
obtained by dip-coating method was around 0.5 μm. It was found that the oxygen permeability of the supported thin film was
lower than that of the perovskite support, which indicated that the pores of the support were reduced by thin-film deposition
on the support surface. The reduction in the pore size led to the more selective permeation mechanism contributes to the overall
permeation. Successful deposition of LSCF6428 thin-film membrane on porous support can be considered as a promising technique
for the preparation of oxygen separation membrane. 相似文献
146.
A carbon-paste electrode modified with 2,7-bis(ferrocenyl ethyl)fluoren-9-one (2,7-BF) and carbon nanotubes (CNTs) was used for the sensitive and selective voltammetric determination of N-acetylcysteine (NAC). The mediated oxidation of NAC at the modified electrode was investigated by cyclic voltammetry (CV). Also, the values of catalytic rate constant (k), and diffusion coefficient (D) for NAC were calculated. Differential pulse voltammetry (DPV) of NAC at the modified electrode exhibited two linear dynamic ranges with a detection limit (3σ) of 52.0 nmol L−1. DPV was used for simultaneous determination of NAC and acetaminophen (AC) at the modified electrode, and quantitation of NAC and AC in some real samples by the standard addition method. 相似文献
147.
Ramin Ghorbani-Vaghei Rahman Karimi-NamiZahra Toghraei-Semiromi Mostafa AmiriMehdi Ghavidel 《Tetrahedron》2011,67(10):1930-1937
N, N, N′, N′-Tetrabromobenzene-1,3-disulfonamide and poly(N-bromo-N-ethylbenzene-1,3-disulfonamide) were used as efficient catalysts for the one-pot synthesis of aliphatic and aromatic 2H-indazolo[2,1-b]phthalazine-triones in excellent yields from aldehydes, phthalhydrazide, and dimedone at 80-100 °C under solvent-free conditions. 相似文献
148.
Flavonoids are secondary metabolites synthesized by plants shown to exhibit health benefits such as anti-inflammatory, antioxidant,
and anti-tumor effects. Thus, due to the importance of this compound, several enzymes involved in the flavonoid pathway have
been cloned and characterized in Escherichia coli. However, the formation of inclusion bodies has become a major disadvantage of this approach. As an alternative, chalcone
synthase from Physcomitrella patens was secreted into the medium using a bacteriocin release protein expression vector. Secretion of P. patens chalcone synthase into the culture media was achieved by co-expression with a psW1 plasmid encoding bacteriocin release protein
in E. coli Tuner (DE3) plysS. The optimized conditions, which include the incubation of cells for 20 h with 40 ng/ml mitomycin C at
OD600 induction time of 0.5 was found to be the best condition for chalcone synthase secretion. 相似文献
149.
Cheong KW Leow TC Rahman RN Basri M Rahman MB Salleh AB;Enzyme Microbial Technology Research Group 《Applied biochemistry and biotechnology》2011,164(3):362-375
A thermostable lipase from Geobacillus zalihae strain T1 was chemically modified using propionaldehyde via reductive alkylation. The targeted alkylation sites were lysines,
in which T1 lipase possessed 11 residues. Far-UV circular dichroism (CD) spectra of both native and alkylated enzyme showed
a similar broad minimum between 208 and 222 nm, thus suggesting a substantial amount of secondary structures in modified enzyme,
as compared with the corresponding native enzyme. The hydrolytic activity of the modified enzymes dropped drastically by nearly
15-fold upon chemical modification, despite both the native and modified form showed distinctive α-helical bands at 208 and
222 nm in CD spectra, leading us to the hypothesis of formation of a molten globule (MG)-like structure. As cooperative unfolding
transitions were observed, the modified lipase was distinguished from the native state, in which the former possessed a denaturation
temperature (T
m) in lower temperature range at 61 °C while the latter at 68 °C. This was further supported by 8-anilino-1-naphthalenesulfonic
acid (ANS) probed fluorescence which indicated higher exposure of hydrophobic residues, consequential of chemical modification.
Based on matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) analysis, a small number
of lysine residues were confirmed to be alkylated. 相似文献
150.
Erfan Mafakheri Abdollah Salimi Rahman Hallaj Abdolali Ramazani Mohamad Almasi Kashi 《Electroanalysis》2011,23(10):2429-2437
For the first time iridium oxide (IrO2) nanotubes are synthesized by electrodeposition in a polycarbonate (PC) template. Potential cycling (90 cycles) between 0.0 and 0.9 V is used for the preparation of IrOx nanotubes onto the PC template with a pore diameter of 100 nm. Field‐emission scanning electron microscopy (FESEM) images show, that IrO2 nanotubes with uniform diameters of 110±10 nm and an estimated length of 1–3 µm are formed. The electrochemical properties and the electrocatalytic activity of a glassy carbon‐IrOx nanotube modified electrode toward Cr3+ and As3+ oxidation are investigated. Finally, the modified electrode is used for micromolar detection of the proposed analytes using differential pulse voltammetry. 相似文献