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排序方式: 共有253条查询结果,搜索用时 484 毫秒
91.
Prokofieva A Prikhod'ko AI Enyedy EA Farkas E Maringgele W Demeshko S Dechert S Meyer F 《Inorganic chemistry》2007,46(10):4298-4307
The synthesis of a new bioinspired dinucleating ligand scaffold based on a bridging pyrazolate with appended bis[2-(1-methylimidazolyl)methyl]aminomethyl chelate arms is reported. This ligand forms very stable copper complexes, and a series of different species is present in solution depending on the pH. Interconversions between these solution species are tracked and characterized spectroscopically, and X-ray crystallographic structures of three distinct complexes that correspond to the species present in solution from acidic to basic pH have been determined. Overall, this provides a comprehensive picture of the copper coordination chemistry of the new ligand system. Alterations in the protonation state are accompanied by changes in nuclearity and pyrazolate binding, which cause pronounced changes in color and magnetic properties. Antiferromagnetic coupling between the copper(II) ions is switched on or off depending on the pyrazole binding mode. 相似文献
92.
Vladimir V. Baranov Maria M. Antonova Valentina A. Karnoukhova Angelina N. Kravchenko 《Tetrahedron letters》2017,58(23):2203-2205
An unexpected reductive transformation of 1-substituted 5-hydroxy-4,5-diphenyl-1H-imidazol-2(5H)-ones (imidazolones) and their cyclic analogs to give 1-substituted 4,5-diphenyl-1H-imidazol-2(5H)-ones (imidazolinones) upon reaction with thiourea and hydrochloric acid was discovered. 相似文献
93.
Olga V. Hordiyenko Angelina V. Biitseva Yuliya Yu. Kostina Roman I. Zubatyuk Oleg V. Shishkin Ulrich M. Groth Mikhail Yu. Kornilov 《Structural chemistry》2017,28(3):607-616
The simplest o-amidino benzoic acid—2-(amino(imino)methyl)benzoic acid—has been isolated in 23 % yield as a side product of the reaction of phthalonitrile and ammonia along with desired 1-imino-1H-isoindol-3-amine. This amidino acid was fully characterized by nuclear magnetic resonance, IR spectroscopy, mass spectrometry; pKa values were also determined. X-ray diffraction study and quantum chemical calculations revealed that in the solid state it exists as a zwitterion that is stabilized by intermolecular hydrogen bonds. 相似文献
94.
A novel LC-fluorescence detection method based on the use of a monolithic column for the determination of norfloxacin, ciprofloxacin, and enrofloxacin antibiotic residues in environmental waters was developed. Fluoroquinolones (FQs) were isocratically eluted using a mobile phase consisting of 0.025 M phosphoric acid solution at pH 3.0 with tetrabutylammonium and methanol (960:40, v/v) through a Chromolith Performance RP-18e column (100x4.6 mm) at a flow rate of 2.5 mL/min and detected at excitation and emission wavelengths of 278 and 450 nm, respectively. After acidification and addition of EDTA, water samples were extracted using an Oasis HLB cartridge. Linearity was evaluated in the range of 0.05 to 1 microg/mL and correlation coefficients of 0.9945 for norfloxacin, 0.9974 for ciprofloxacin, and 0.9982 for enrofloxacin were found. The limit of quantification was 25 ng/L for the three FQs. The recovery of FQs spiked into river water samples at 25, 50, and 100 ng/L fortification levels ranged from 76.5 to 91.0% for norfloxacin, 78.5 to 97.2% for ciprofloxacin, and 79.4 to 93.6% for enrofloxacin. This method was successfully applied to the analysis of water samples from the Mondego River, and ciprofloxacin and enrofloxacin residues were detected in eight water samples. 相似文献
95.
We report a low cost selective analytical method based on inner filter effect (IFE) for citrate-silver nanoparticle (cit-AgNP) detection, in which fluorescent amine-derivatized carbon dots (a-CDs) act as the donor and aggregated cit-AgNPs as the energy receptor. Carbon dots (CDs) were chemically modified with ethylenediamine (EDA) moieties via amidic linkage displaying an emission band at 440 nm. The presence of cit-AgNPs produces a remarkably quenching of a-CD fluorescence via IFE, since the free amine groups at CD surface induce the aggregation of cit-AgNPs accompany by a red-shifting of their characteristic plasmon absorption wavelength, which resulted in “turn-on” of the IFE-decreased in CD fluorescence. The proposed method, which involves the use of chelating agents for removal of metal ions interferences, exhibits a good linear correlation for detection of cit-AgNPs from 1.23 × 10−5 to 6.19 × 10−5 mol L−1, with limits of detection (LOD) and quantification (LOQ) of 5.17 × 10−6 and 1.72 × 10−5 mol L−1, respectively. This method demonstrates to be efficient and selective for the determination of cit-AgNPs in complex matrices such as cosmetic creams and reveals many advantages such as low cost, reusability, high sensitivity and non time-consuming compared with other traditional methods. 相似文献
96.
Unexpectedly, nitrosation of 5,7‐dialkyl‐3‐thioxoperhydroimidazo[4,5‐e]‐1,2,4‐triazine‐6‐ones(thiones) with sodium nitrite in glacial AcOH led to 3,3′‐bis(5,7‐dialkyl‐1‐nitroso‐6‐oxo(thioxo)‐1,4,4a,5,7,7a‐hexahydroimidazo[4,5‐e]‐1,2,4‐triazinyl)disulfides that decomposed spontaneously into 1,3‐dialkyl‐5‐thioxohexahydroimidazo[4,5‐d]imidazol‐2(1H)‐ones(thiones) in DMSO‐d6 in the presence of water. 相似文献
97.
Synthesis of New Substituted Thioglycolurils via a Tandem Hydrazone Formation‐ Ring Contraction Reaction
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Galina A. Gazieva Tatyana B. Karpova Leonid D. Popov Yulia V. Nelyubina Angelina N. Kravchenko 《Journal of heterocyclic chemistry》2015,52(5):1390-1394
A series of new (E)‐1,3‐dialkyl‐4‐((hetarylmethylidene)amino)‐5‐thioxohexahydroimidazo[4,5‐d]imidazole‐2(1H)‐ones (thioglycolurils) was synthesized via tandem hydrazone formation—ring contraction reaction of 5,7‐dialkyl‐3‐thioxoperhydroimidazo[4,5‐e]‐1,2,4‐triazin‐6‐ones with heteroaromatic aldehydes. 相似文献
98.
Morales-Ríos MS Rivera-Becerril E González-Juárez DE García-Vázquez JB Trujillo-Serrato JJ Hernández-Barragán A Joseph-Nathan P 《Natural product communications》2011,6(4):457-464
A series of 1,3a,8-alkylpyrrolidinoindolines have been synthesized. The scope and limitations of the alkylation of starting methyl oxindol-3-acetates are explored employing electron-rich and electron-poor alkylating agents. Hydrolysis and reductive lactonization of the resulting carboxylic gamma-oxindolic acid derivatives proceeds with good yields to afford 2-oxofuroindolines providing ready access to the pyrrolidinoindoline derivatives. 相似文献
99.
SAXS investigation of a cubic to a sponge (L3) phase transition in self-assembled lipid nanocarriers
Angelov B Angelova A Mutafchieva R Lesieur S Vainio U Garamus VM Jensen GV Pedersen JS 《Physical chemistry chemical physics : PCCP》2011,13(8):3073-3081
The encapsulation and release of peptides, proteins, nucleic acids, and drugs in nanostructured lipid carriers depend on the type of the self-assembled liquid-crystalline organization and the structural dimensions of the aqueous and membraneous compartments, which can be tuned by the multicomponent composition of the systems. In this work, small-angle X-ray scattering (SAXS) investigation is performed on the 'melting' transition of the bicontinuous double diamond cubic phase, formed by pure glycerol monooleate (MO), upon progressive inclusion of varying fractions of pharmaceutical-grade glycerol monooleate (GO) in the hydrated system. The self-assembled MO/GO mixtures are found to form diamond (Pn3m) inverted cubic, inverted hexagonal (H(II)), and sponge (L(3)) phases at ambient temperature in excess of aqueous medium without heat treatment. Mixing of the inverted-cubic-phase-forming MO and the sponge-phase-forming GO components, in equivalent proportions (50/50 w/w), yields an inverted hexagonal (H(II)) phase nanostructured carrier. Scattering models are applied for fitting of the experimental SAXS patterns and identification of the structural changes in the aqueous and lipid bilayer subcompartments. The possibility of transforming, at ambient temperature (20 °C), the bicontinuous cubic nanostructures into inverted hexagonal (H(II)) or sponge (L(3)) mesophases may facilitate novel biomedical applications of the investigated liquid crystalline self-assemblies. 相似文献
100.
Romoli R Papaleo MC de Pascale D Tutino ML Michaud L LoGiudice A Fani R Bartolucci G 《Journal of mass spectrometry : JMS》2011,46(10):1051-1059
Bacteria belonging to the Burkholderia cepacia complex (Bcc) are significant pathogens in Cystic Fibrosis (CF) patients and are resistant to a plethora of antibiotics. In this context, microorganisms from Antarctica are interesting because they produce antimicrobial compounds inhibiting the growth of other bacteria. This is particularly true for bacteria isolated from Antarctic sponges. The aim of this work was to characterize a set of Antarctic bacteria for their ability to produce new natural drugs that could be exploited in the control of infections in CF patients by Bcc bacteria. Hence, 11 bacterial strains allocated to different genera (e.g., Pseudoalteromonas, Arthrobacter and Psychrobacter) were tested for their ability to inhibit the growth of 21 Bcc strains and some other human pathogens. All these bacteria completely inhibited the growth of most, if not all, Bcc strains, suggesting a highly specific activity toward Bcc strains. Experimental evidences showed that the antimicrobial compounds are small volatile organic compounds, and are constitutively produced via an unknown pathway. The microbial volatile profile was obtained by SPME-GC-MS within the m/z interval of 40-450. Solid phase micro extraction technique affords the possibility to extract the volatile compounds in head space with a minimal sample perturbation. Principal component analysis and successive cluster discriminant analysis was applied to evaluate the relationships among the volatile organic compounds with the aim of classifying the microorganisms by their volatile profile. These data highlight the potentiality of Antarctic bacteria as novel sources of antibacterial substances to face Bcc infections in CF patients. 相似文献