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941.
942.
Rossato G Ernst B Vedani A Smiesko M 《Journal of chemical information and modeling》2011,51(8):1867-1881
Water molecules mediating polar interactions in ligand-protein complexes can substantially contribute to binding affinity and specificity. To account for such water molecules in computer-aided drug design, we performed an extensive search in the Cambridge Structural Database (CSD) to identify the geometrical criteria defining interactions of water molecules with ligand and protein. In addition, with ab initio calculations the propensity of ligand hydration was evaluated. Based on this information, we developed an algorithm (AcquaAlta) to reproduce water molecules bridging polar interactions between ligand and protein moieties. This approach was validated with 20 crystal structures and yielded a match of 76% between experimental and calculated water positions. When water molecules establishing only weak interactions with the protein were neglected, the match could be improved to 88%. Supported by a pharmacophore-based alignment tool, the solvation algorithm was then applied to the docking of oligopeptides to the periplasmic oligopeptide binding protein A (OppA). Calculated waters based on the crystal poses matched an average of 66% of the experimental waters. With water molecules calculated based on the docked ligands, the average match with the experimental waters dropped to 53%. 相似文献
943.
Lippolis V Pascale M Valenzano S Pluchinotta V Baumgartner S Krska R Visconti A 《Analytical and bioanalytical chemistry》2011,401(8):2561-2571
A rapid fluorescence polarization (FP) immunoassay has been developed for the simultaneous determination of T-2 and HT-2 toxins
in naturally contaminated wheat samples. Syntheses of four fluorescein-labelled T-2 or HT-2 toxin tracers were carried out
and their binding response with seven monoclonal antibodies was evaluated. The most sensitive antibody-tracer combination
was obtained by using an HT-2-specific antibody and a fluorescein-HT-2 tracer. The developed competitive FP immunoassay in
solution showed high cross-reactivity for T-2 toxin (CR% = 100%) while a very low CR% for neosolaniol (0.12%) and no cross-reactivity
with other mycotoxins frequently occurring in wheat. A rapid extraction procedure using 90% methanol was applied to wheat
samples prior to FP immunoassay. The average recovery from spiked wheat samples (50 to 200 μg kg−1) was 96% with relative standard deviation generally lower than 8%. A limit of detection of 8 μg kg−1 for the combined toxins was determined. Comparative analyses of 45 naturally contaminated and spiked wheat samples by both
the FP immunoassay and high-performance liquid chromatography/immunoaffinity clean-up showed a good correlation (r = 0.964). These results, combined with the rapidity (10 min) and simplicity of the assay, show that this method is suitable
for high throughput screening as well as for quantitative determination of T-2 and HT-2 toxins in wheat. 相似文献
944.
The allantoin/uric acid (All/UA) ratio and malondialdehyde (MDA) plasma levels have been proposed as important markers for
monitoring oxidation triggered by the action of free radicals (FR). Here, we describe an easy field amplified sample injection
capillary electrophoresis method with UV detection for the separation and quantification of All, UA, and free MDA in human
plasma. The plasma samples were simply filtered through centrifugation membrane tubes for protein elimination and directly
injected on a capillary without complex cleanup and/or sample derivatization procedures. The use of a run buffer composed
of 300 mmol/L sodium borate at pH 10 with 50 mmol/L of N-methyl-d-glucamine and an overimposed pressure/voltage of 0.1 psi during the electrophoretic run allows basline resolution of the
analytes within 17 min. The electrokinetic injection allows a detection limit of 15 nmol/L for All, 20 nmol/L for UA and 10 nmol/L
for MDA in a plasma sample, thus significantly improving the LOD of previous described methods based on capillary electrophoresis.
Precision tests indicate a good repeatability of our method both for migration times (CV = 1.85%) and areas (CV = 2.87%).
Moreover, a good reproducibility of intra- and inter-assay tests was obtained (CV = 4.63% and CV = 6.59% respectively). The
suitability of the method was tested by measuring analyte levels in 40 healthy volunteers. 相似文献
945.
946.
A field amplified sample injection (FASI) capillary electrophoresis method with UV detection was developed for the separation and detection of carnosine-related peptides carnosine (Car), anserine (Ans) and homocarnosine (Hcar). The imidazole dipeptides were baseline-separated within 10 min by using 50 mmol/L Tris phosphate pH 2.2 as running buffer. The samples were diluted in water and directly injected on the capillary without complex cleanup and/or sample derivatization procedures. Using the electrokinetic injection, a sensitivity improvement of about 500-fold was achieved without any loss of separation efficiency if compared to the conventional sample injection. The detection limits for carnosine, anserine, and homocarnosine were between 0.4 and 0.5 nmol/L, thus improving of 10-100-fold the LOD of previous described methods based on laser induced fluorescence or chemiluminescence detection. This method has been applied to the analysis of homogenized rat tissue (heart, muscle and brain) and human cerebrospinal fluid (CSF). 相似文献
947.
Solfrizzo M De Girolamo A Gambacorta L Visconti A Stroka J Van Egmond HP 《Journal of AOAC International》2011,94(3):900-908
A liquid chromatographic method for the determination of fumonisins B1 (FB1) and B2 (FB2) in corn-based foods for infants and young children was subjected to an interlaboratory validation study involving 11 laboratories. Five blind duplicate sample pairs of each matrix were analyzed to establish the accuracy, repeatability, and reproducibility of the method. Mass fractions in the baby food samples ranged from 89.1 to 384.4 microg/kg FB1 and from 22.5 to 73.6 microg/kg FB2. The method involved a warm extraction with citrate phosphate buffer-methanol-acetonitrile (50 + 25 + 25, v/v/v), a cleanup through an immunoaffinity column, and an end-determination of fumonisins by LC after automated precolumn derivatization with o-phthaldialdehyde reagent. RSDs for within-laboratory repeatability (RSDr) ranged from 6.8 to 23.5% for FB1 and 7.6 to 22.9% for FB2. RSDs for between-laboratory reproducibility (RSDR) ranged from 15.4 to 26.2% for FB1 and 21.6 to 36.3% for FB2. Mean FB1 recoveries from baby foods spiked at 100.0 and 250.0 microg/kg were 89 and 96%, respectively; for FB2 spiked foods at 25.0 and 62.5 microg/kg recoveries were 90 and 85%, respectively. HorRat values ranged from 0.8 to 1.2 for FB1, whereas for FB2 they ranged from 0.9 to 1.4 when calculated according to Horwitz, and from 1.0 to 1.7 when calculated according to Thompson, indicating an acceptable among-laboratory precision for all matrixes (HorRat values <2). 相似文献
948.
Alkaloids from Hippeastrum papilio 总被引:1,自引:0,他引:1
de Andrade JP Berkov S Viladomat F Codina C Zuanazzi JA Bastida J 《Molecules (Basel, Switzerland)》2011,16(8):7097-7104
Galanthamine, an acetylcholinesterase inhibitor marketed as a hydrobromide salt (Razadyne?, Reminyl?) for the treatment of Alzheimer's disease (AD), is obtained from Amaryllidaceae plants, especially those belonging to the genera Leucojum, Narcissus, Lycoris and Ungernia. The growing demand for galanthamine has prompted searches for new sources of this compound, as well as other bioactive alkaloids for the treatment of AD. In this paper we report the isolation of the new alkaloid 11β-hydroxygalanthamine, an epimer of the previously isolated alkaloid habranthine, which was identified using NMR techniques. It has been shown that 11β-hydroxygalanthamine has an important in vitro acetylcholinesterase inhibitory activity. Additionally, Hippeastrum papilio yielded substantial quantities of galanthamine. 相似文献
949.
Natalia M. Padial Dr. Elsa Quartapelle Procopio Carmen Montoro Elena López Prof. J. Enrique Oltra Dr. Valentina Colombo Dr. Angelo Maspero Prof. Norberto Masciocchi Dr. Simona Galli Dr. Irena Senkovska Prof. Stefan Kaskel Dr. Elisa Barea Prof. Jorge A. R. Navarro 《Angewandte Chemie (International ed. in English)》2013,52(32):8290-8294
950.
We present first ab initio no-core shell model (NCSM) calculations using similarity renormalization group (SRG) transformed chiral two-nucleon (NN) plus three-nucleon (3N) interactions for nuclei throughout the p-shell, particularly (12)C and (16)O. By introducing an adaptive importance truncation for the NCSM model space and an efficient JT-coupling scheme for the 3N matrix elements, we are able to surpass previous NCSM studies including 3N interactions. We present ground and excited states in (12)C and (16)O for model spaces up to N(max) = 12 including full 3N interactions. We analyze the contributions of induced and initial 3N interactions and probe induced 4N terms through the sensitivity of the energies on the SRG flow parameter. Unlike for light p-shell nuclei, SRG-induced 4N contributions originating from the long-range two-pion terms of the chiral 3N interaction are sizable in (12)C and (16)O. 相似文献