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排序方式: 共有1225条查询结果,搜索用时 24 毫秒
131.
Hauck M Stolte M Schönhaber J Kuball HG Müller TJ 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(36):9984-9998
Phenothiazinyl merocyanine dyes with variable substitution patterns on the peripheral benzene ring were synthesized in good yields by Knoevenagel condensation of the corresponding phenothiazinyl aldehydes and N-methylrhodanine or indan-1,3-dione. The electronic properties were investigated by cyclic voltammetry, absorption, electro-optical absorption, and emission spectroscopy. All these merocyanines reveal reversible redox behavior that stems from the phenothiazinyl-centered oxidation to give stable radical cations. The redox potentials strongly correlate with Hammett σ(p) parameters. All merocyanines reveal large Stokes shifts. They also display a pronounced emissive solvatochromism, which is caused by large dipole moment changes upon excitation from the ground to the excited state. These findings are supported by solvatochromism studies and time-dependent DFT computations. 相似文献
132.
Today, a life without poly(ethylene glycol) is hardly imaginable. One encounters PEG in nearly every aspect of our daily needs: from cosmetics to hairstyling products and from medicines to food. Even in maritime military technology and the preservation of recovered cultural possessions PEG can be found. This article deals with the synthesis, the surprising properties, and the application of this structurally simple yet fascinating and important polymer. 相似文献
133.
Tiziana Forleo Alessandro Zappi Dora Melucci Martina Ciriaci Francesco Griffoni Simone Bacchiocchi Melania Siracusa Tamara Tavoloni Arianna Piersanti 《Molecules (Basel, Switzerland)》2021,26(9)
The international seafood trade is based on food safety, quality, sustainability, and traceability. Mussels are bio-accumulative sessile organisms that need regular control to guarantee their safe consumption. However, no well-established and validated methods exist to trace mussel origin, even if several attempts have been made over the years. Recently, an inorganic multi-elemental fingerprint coupled to multivariate statistics has increasingly been applied in food quality control. The mussel shell can be an excellent reservoir of foreign inorganic chemical species, allowing recording long-term environmental changes. The present work investigates the multi-elemental composition of mussel shells, including Al, Cu, Cr, Zn, Mn, Cd, Co, U, Ba, Ni, Pb, Mg, Sr, and Ca, determined by inductively-coupled plasma mass-spectrometry in Mytilus galloprovincialis collected along the Central Adriatic Coast (Marche Region, Italy) at 25 different sampling sites (18 farms and 7 natural banks) located in seven areas. The experimental data, coupled with chemometric approaches (principal components analysis and linear discriminant analysis), were used to create a statistical model able to discriminate samples as a function of their production site. The LDA model is suitable for achieving a correct assignment of >90% of individuals sampled to their respective harvesting locations and for being applied to counteract fraud. 相似文献
134.
Martina Mazzoni Lorenzo Franco Alberta Ferrarini Carlo Corvaja Giovanni Zordan Gianfranco Scorrano 《Liquid crystals》2013,40(2):203-208
A nitroxide [60]fullerene adduct containing a pyrrolidine-1-oxyl group has been synthesized. Its orientational order in the nematic phase of the liquid crystal solvent 4,4′-azoxyanisole (PAA) has been measured from the variation of the EPR spectral parameters on passing from the isotropic to the nematic phase. Highly resolved EPR lines allow for precise evaluation of the shifts of the g, a N and a H values. Since the g and the hyperfine tensors are known, the order matrix could be obtained. This is compared with the one calculated with a theoretical model based on short range solute-solvent interactions, which predicts a considerable degree of orientation of the molecular axes, despite the almost spherical shape of the molecule. The agreement with experimental findings is quite good and it is further improved if a bent structure of the pyrrolidine ring is taken into account. 相似文献
135.
Firdaus Yhaya Sandra Binauld Yoseop Kim Martina H. Stenzel 《Macromolecular rapid communications》2012,33(21):1868-1874
A block copolymer based on poly(N‐isopropyl acrylamide) (PNIPAAm) and a block with a statistical distribution of poly(2‐hydroxyethyl acrylate) (PHEA) and repeating unit with carrying β‐cyclodextrin was prepared via reversible addition–fragmentation chain transfer (RAFT) polymerization and click reaction. Addition of poly(2‐hydroxyethyl acrylate‐s‐adamantylmethyl acrylate) P(HEA17‐s‐AdMA7) above the LCST of the block copolymer led to capture of the micelle structure of 36 nm against disassembly. The drug‐ (albendazole) loaded supramolecular assembly, which was fixed via host–guest complexation between β‐cyclodextrin and adamantane, was then tested as a drug carrier. Cell viability studies using human ovarian carcinoma cell line (OVCAR‐3) cell lines show a higher toxicity of the shell cross‐linked micelle compared with the free block copolymer. 相似文献
136.
Hubert Hřebabecký Milan Dejmek Martin Dračínský Michal Šála Pieter Leyssen Johan Neyts Martina Kaniaková Jan Krůšek Radim Nencka 《Tetrahedron》2012,68(4):1286-1298
Azanorbornylpurine derivatives were prepared by Mitsunobu reaction of appropriate hydroxyazanorbornane derivative with 6-chloropurine or construction of purine base at azanorbornylamines. The prepared target compounds were evaluated for antiviral activity and effect on neuronal and muscle nicotinic acetylcholine receptors. 相似文献
137.
Walter Bauer Jochen Ellermann Martina Dotzler Diana Pohl Frank W. Heinemann Matthias Moll 《无机化学与普通化学杂志》2000,626(2):574-587
Chemistry of Polyfunctional Molecules. 133. X‐Ray Crystal Structural, Solid‐state 31P CP/MAS NMR, TOSS, 31P COSY NMR, and Mechanistic Contributions to the Co‐ordination Chemistry of Octacarbonyldicobalt with the Ligands Bis(diphenylphosphanyl)amine, Bis(diphenylphosphanyl)methane, and 1,1,1‐Tris(diphenylphosphanyl)ethane Co2(CO)8 reacts with bis(diphenylphosphanyl)amine, HN(PPh2)2 (Hdppa, 1 ), in two steps to afford the known compound [Co(CO)(Hdppa‐κ2P)2][Co(CO)4] · 2 THF ( 6 a · 2 THF). The intermediate [Co(CO)2(Hdppa‐κ2P) · (Hdppa‐κP)][Co(CO)4] · dioxane · n‐pentane ( 5 · dioxane · n‐pentane) was isolated for the first time and was characterized by X‐ray analysis. The cation 5 + exhibits a slightly distorted trigonal‐bipyramidal geometry. Detailed 31P‐NMR investigations (solid‐state CP/MAS NMR, TOSS, 31P‐COSY, 31P‐EXSY) showed that the additional tautomer [Co(CO)2(Hdppa‐κ2P)(Ph2P–N=P(H)Ph2‐κP)]+ ( 5 ′+) is present in solution. The tautomer equilibrium is slow in the NMR time scale. In contrast to the solid state only tetragonal pyramidal species of 5 are found in solution. At –90 °C there is slow exchange between the three diastereomeric species 5 a +– 5 c +. Compound 5 forms [Co(CO) · (Hdppa‐κ2P)2]BPh4 · THF ( 6 b · THF) in THF with NaBPh4 under CO‐Elimination. A X‐ray diffraction investigation shows that the cation 6 + consists of a slightly distorted trigonal‐bipyramidal co‐ordination polyeder. However, a distorted tetragonal‐pyramidal structure has been found for the cation 7 + of the related compound [Co(CO)(dppm)2][Co(CO)4] · 2 THF ( 7 · 2 THF; dppm = bis(diphenylphosphanyl)methane, Ph2PCH2PPh2). A comparison with the known [8] trigonal‐bipyramidal stereoisomer, ascertained for 7 + of the solvent‐free 7 , is described. In solutions of 6 a · 2 THF and 7 · 2 THF 13C{1H}‐ and 31P{1H}‐NMR spectra indicate an exchange of all CO and organophosphane molecules between cobalt(I) cation and cobalt(–I) anion. A concerted mechanism for the exchange process is discussed. CO elimination leads to discontinuance of the cyclic mechanism by forming binuclear substitution products such as the isolated Co2(CO)2 · (μ‐CO)2(μ‐dppm)2 · 0.83 THF ( 8 · 0.83 THF), which was characterized by spectroscopy and X‐ray analysis. For the dissolved [Co(CO)2CH3C(CH2PPh2)3][Co(CO)4] · 0.83 n‐pentane ( 9 a · 0.83 n‐pentane) no CO and triphos exchange processes between the cation and the anion are observed. Metathesis of 9 a · 0.83 n‐pentane with NaBPh4 yields [Co(CO)2CH3C(CH2PPh2)3]BPh4 ( 9 b ) which has been characterized by single‐crystal X‐ray analysis. The cation shows a small distorted tetragonal‐pyramidal structure. 相似文献
138.
Sébastien L.X. Martina 《Tetrahedron letters》2004,45(16):3279-3282
Novel solid-supported phosphonate reagents have been prepared and evaluated for the synthesis of α,β-unsaturated esters with a preference for the Z-alkene. The optimal reagent was a hybrid of both Still-Gennari and Ando reagents, and showed good to high yields and fair to good Z-selectivity for the conversion of both aliphatic and aromatic aldehydes. 相似文献
139.
Wolpert M Hellwig P 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2006,64(4):987-1001
In this work, we present the absorption spectra and molar coefficients of all 20 amino acids in aqueous solutions down to 500 cm(-1). The spectral region between 1200 and 500 cm(-1) was yet disregarded for protein infrared spectroscopy, mainly due to the strong H(2)O absorption. Absorption spectra were obtained mainly for physiological relevant pH region. Intense bands for aromatic amino acids, histidine and such with OH group could clearly be identified throughout the given spectral region. For sulfur-containing amino acids cysteine and methionine some strong bands besides the weak carbon-sulfur stretching vibration was shown. Effects of aqueous solution environment, pH, protonation states were discussed, together with previously reported data from theoretical approaches. With this complete set of spectral information application to proteins in the whole mid infrared region could be described precise and the potential of the lower spectral region to study typical cofactor ligands like histidine, shown. 相似文献