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91.
Jacob St-Gelais Émilie Côté Danny Lainé Prof. Paul A. Johnson Prof. Denis Giguère 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(59):13499-13506
In this work, we synthesized all mono-, di-, and trifluorinated glucopyranose analogues at positions C-2, C-3, C-4, and C-6. This systematic investigation allowed us to perform direct comparison of 19F resonances of fluorinated glucose analogues and also to determine their lipophilicities. Compounds with a fluorine atom at C-6 are usually the most hydrophilic, whereas those with vicinal polyfluorinated motifs are the most lipophilic. Finally, the solvation energies of fluorinated glucose analogues were assessed for the first time by using density functional theory. This method allowed the log P prediction of fluoroglucose analogues, which was comparable to the C log P values obtained from various web-based programs. 相似文献
92.
Danny Schuhknecht Thomas P. Spaniol Laurent Maron Jun Okuda 《Angewandte Chemie (International ed. in English)》2020,59(1):310-314
Chemo‐ and regioselectivity are often difficult to control during olefin hydrosilylation catalyzed by d‐ and f‐block metal complexes. The cationic hydride of calcium [CaH]+ stabilized by an NNNN macrocycle was found to catalyze the regioselective hydrosilylation of aliphatic olefins to give anti‐Markovnikov products, while aryl‐substituted olefins were hydrosilyated with Markovnikov regioselectivity. Ethylene was efficiently hydrosilylated by primary and secondary hydrosilanes to give di‐ and monoethylated silanes. Aliphatic hydrosilanes were preferred over other commonly employed hydrosilanes: Arylsilanes such as PhSiH3 underwent scrambling reactions promoted by the nucleophilic hydride, while alkoxy‐ and siloxy‐substituted hydrosilanes gave isolable alkoxy and siloxy calcium derivatives. 相似文献
93.
A sandwich technique based on the very affinity between avidin and biotin is used. Antibodies are covalently bound to glass-fibre on which the antigen is captured. The discs are then treated in sequence with monoclonal antibodies of high selectivity, species-specific anti-IgG (biotin-linked), streptavidin and β-galactosidase, (biotin-linked). The discs are then incubated with the substrate, 4-methylumbelliferyl-β-d-galactopyranoside and the fluorescence is measured in an automatic immunoassay system. 相似文献
94.
Decision analysis models are developed and illustrated for the reinsurance (risk transfer) decisions made by insurance companies. Decision analytic models were found to be useful tools both for structuring multistage reinsurance decisions and for comparing alternative options. The insurer is faced with many possible choices involving reinsurance type and extent, and an expected utility model provided insight both as a screening device and as an evaluation criterion. Decision analytic models appeared to be superior to other approaches such as mean/variance and risk of ruin models both because of their flexibility and their more comprehensive treatment the important elements of the decision, namely the complete claims distribution, the cost of reinsurance and the insurer's risk attitude. 相似文献
95.
Surfactants can be introduced into the environment through wastewater or by direct contamination. Understanding the fate and transport of surfactants in the environment is important in assessing their role as pollutants. Humic substances are complex heterogeneous mixtures of decomposition products of natural organic materials. They are environmentally important because they are known to solubilize and transport organic pollutants. Therefore humic substances are likely to affect the environmental fate of surfactants. Diffusion coefficients measured with pulsed-field gradient nuclear magnetic resonance spectroscopy are used in this study to examine the intermolecular interactions of the surfactants sodium dodecyl sulfate (SDS) and cetyltrimethylammonium bromide (CTAB) in the presence of various humic substances. These results indicate that humic substances enhance the aggregation of SDS prior to micellization with a more pronounced effect observed for the more hydrophobic humic materials. The positively charged surfactant CTAB forms stable ion pairs with the humic substances. 相似文献
96.
Danny Brouard Jean-Franois Y. Gravel Mathieu Lessard Viger Denis Boudreau 《Spectrochimica Acta Part B: Atomic Spectroscopy》2007,62(12):1361-1369
Silicon, zirconium and aluminum sol–gels were investigated as suitable starting materials for tunable matrix calibration standards for laser-induced breakdown spectroscopy. A fast and simple preparation method was developed, using aluminum i-propoxide as the precursor in the sol–gel synthesis, which allows one to quickly prepare solid calibration standards offering very homogenous analyte distribution in the matrix, low optical spectral background, as well as reproducible behavior towards laser ablation and vaporization. The surface of the calibration targets and the morphology of the ablation craters were examined by optical and scanning electron microscopy, and the material ejection process was observed by shadowgraph imaging. Low μg/g detection limits and 4–15% relative standard deviation were measured by laser induced breakdown spectroscopy for Pb, Cr and Be used as internal standards. 相似文献
97.
Danny M. Gelman Penelope A. Mayes Roger Mulder Patrick Perlmutter 《Tetrahedron: Asymmetry》2006,17(24):3341-3350
Reversing the polarity of the cycloaddition partners in Dane’s steroid synthesis provides ready access to enantiomerically pure, functionally-rich steroidal structures. 相似文献
98.
Jinghui Wang Danny X. Liu Marcello Canova R. Gregory Downing Lei R. Cao Anne C. Co 《Journal of Radioanalytical and Nuclear Chemistry》2014,301(1):277-284
Measuring the distribution of lithium in high capacity lithium-ion battery (LIB) electrodes is essential to understanding the coulombic losses during the lithiation/delithiation processes that occur while charging and discharging the cell. In this research, two half-cell prototypes were fabricated by electrochemically lithiating Sn foil anodes in 1M LiBF4 in a 1:1 (wt:wt) ethylene carbonate and dimethyl carbonate solutions at a constant potential of 0.50 and 0.67 V (vs. Li/Li+). The neutron depth profiling (NDP) technique was employed to study the Li distributions in the anodes. Li concentration profiles were resolved for the samples lithiated under different conditions for LIB studies. In addition, this paper demonstrated an in situ NDP measurement of an electrochemical cell with a thin window design, which reveals the dynamics of lithium distribution within the Sn anode. 相似文献
99.
Jeannette Janssen Danny Krizanc Lata Narayanan Sunil Shende 《Journal of Algorithms in Cognition, Informatics and Logic》2000,36(2):119
A cellular network is generally modeled as a subgraph of the triangular lattice. The distributed online frequency assignment problem can be abstracted as a multicoloring problem on a weighted graph, where the weight vector associated with the vertices models the number of calls to be served at the vertices and is assumed to change over time. In this paper, we develop a framework for studying distributed online frequency assignment in cellular networks. We present the first distributed online algorithms for this problem with proven bounds on their competitive ratios. We show a series of algorithms that use at each vertex information about increasingly larger neighborhoods of the vertex, and that achieve better competitive ratios. In contrast, we show lower bounds on the competitive ratios of some natural classes of online algorithms. 相似文献
100.
Adenosine diphosphate-ribosyl cyclase (ADP-ribosyl cyclase) is a ubiquitous enzyme in eukaryotes that converts NAD+ to cyclic-ADP-ribose (cADPR) and nicotinamide. A quantitative assay for cADPR was developed using capillary electrophoresis to separate NAD+, cADPR, ADP-ribose, and ADP with UV detection (254 nm). Using this assay, the apparent Km and Vmax for Aplysia ADP-ribosyl cyclase were determined to be 1.24+/-0.05 mM and 131.8+/-2.0 microM/min, respectively. Boric acid inhibited ADP-ribosyl cyclase non-competitively with a Ki of 40.5+/-0.5 mM. Boric acid binding to cADPR, determined by electrospray ionization mass spectrometry, was characterized by an apparent binding constant, KA, of 655+/-99 L/mol at pH 10.3. 相似文献