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61.
Maria G. da Fonseca Cassio M. Cardoso Luiza N.H. Arakaki 《Journal of Physics and Chemistry of Solids》2006,67(8):1835-1840
Vermiculite of general formula [Si6.85Al1.15][Mg4.68Al0.51Fe0.63]O20(OH)4Ca0.128Na0.032K0.094 reacted with heteroaromatic amines α-, β-, and γ-picolines from aqueous solution. The products were characterized by elemental analysis, infrared spectroscopy, and X-ray diffraction. The intercalated nanocompounds maintained the crystallinity and changed the original interlayer distance of 1422 pm to 1474, 1456, and 1474 pm, for the sequence of the guest picoline molecules. Natural and intercalated vermiculite can remove copper at the solid/liquid interface; removal 0.40 mmol g−1 was obtained for the original matrix, and 1.10, 0.92, and 1.33 mmol g−1 for the intercalated forms. These values are near the capacity of cation exchange (CEC) of this clay mineral, which can be possibly used as source of copper removal from aqueous solution. 相似文献
62.
63.
Covalent Attachment of Cyclic TAT Peptides to GFP Results in Protein Delivery into Live Cells with Immediate Bioavailability
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Dr. Francesco Natale Nina Bohlke Prof. Nediljko Budisa Prof. M. Cristina Cardoso Prof. Christian P. R. Hackenberger 《Angewandte Chemie (International ed. in English)》2015,54(6):1950-1953
The delivery of free molecules into the cytoplasm and nucleus by using arginine‐rich cell‐penetrating peptides (CPPs) has been limited to small cargoes, while large cargoes such as proteins are taken up and trapped in endocytic vesicles. Based on recent work, in which we showed that the transduction efficiency of arginine‐rich CPPs can be greatly enhanced by cyclization, the aim was to use cyclic CPPs to transport full‐length proteins, in this study green fluorescent protein (GFP), into the cytosol of living cells. Cyclic and linear CPP–GFP conjugates were obtained by using azido‐functionalized CPPs and an alkyne‐functionalized GFP. Our findings reveal that the cyclic‐CPP–GFP conjugates are internalized into live cells with immediate bioavailability in the cytosol and the nucleus, whereas linear CPP analogues do not confer GFP transduction. This technology expands the application of cyclic CPPs to the efficient transport of functional full‐length proteins into live cells. 相似文献
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66.
Dr. Shrinivas Dumbre Dr. Valérie Pezo Guy Schepers Prof. Vitor B. Pinheiro Prof. Eveline Lescrinier Prof. Philipp Holliger Dr. Philippe Marlière Prof. Piet Herdewijn 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(13):5009-5022
The synthesis, base‐pairing properties and in vitro and in vivo characteristics of 5‐methyl‐isocytosine (isoCMe) and isoguanine (isoG) nucleosides, incorporated in an HNA(h) (hexitol nucleic acid)–DNA(d) mosaic backbone, are described. The required h‐isoG phosphoramidite was prepared by a selective deamination as a key step. As demonstrated by Tm measurements the hexitol sugar showed slightly better mismatch discrimination against dT. The d‐isoG base mispairing follows the order T>G>C while the h‐isoG base mispairing follows the order G>C>T. The h‐ and d‐isoCMe bases mainly mispair with G. Enzymatic incorporation experiments show that the hexitol backbone has a variable effect on selectivity. In the enzymatic assays, isoG misincorporates mainly with T, and isoCMe misincorporates mainly with A. Further analysis in vivo confirmed the patterns of base‐pair interpretation for the deoxyribose and hexitol isoCMe/isoG bases in a cellular context, through incorporation of the bases into plasmidic DNA. Results in vivo demonstrated that mispairing and misincorporation was dependent on the backbone scaffold of the base, which indicates rational advances towards orthogonality. 相似文献
67.
Maximum likelihood estimation for stochastic volatility in mean models with heavy‐tailed distributions
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Carlos A. Abanto‐Valle Roland Langrock Ming‐Hui Chen Michel V. Cardoso 《商业与工业应用随机模型》2017,33(4):394-408
In this article, we introduce a likelihood‐based estimation method for the stochastic volatility in mean (SVM) model with scale mixtures of normal (SMN) distributions. Our estimation method is based on the fact that the powerful hidden Markov model (HMM) machinery can be applied in order to evaluate an arbitrarily accurate approximation of the likelihood of an SVM model with SMN distributions. Likelihood‐based estimation of the parameters of stochastic volatility models, in general, and SVM models with SMN distributions, in particular, is usually regarded as challenging as the likelihood is a high‐dimensional multiple integral. However, the HMM approximation, which is very easy to implement, makes numerical maximum of the likelihood feasible and leads to simple formulae for forecast distributions, for computing appropriately defined residuals, and for decoding, that is, estimating the volatility of the process. Copyright © 2017 John Wiley & Sons, Ltd. 相似文献
68.
Ana T.P.C. GomesAnna C. Cunha Maria do Rosário M. DominguesMaria G.P.M.S. Neves Augusto C. ToméArtur M.S. Silva Fernanda da C. SantosMaria C.B.V. Souza Vitor F. FerreiraJosé A.S. Cavaleiro 《Tetrahedron》2011,67(38):7336-7342
New porphyrin/4-quinolone conjugates were synthesized from the Suzuki-Miyaura coupling reaction of a β-borylated porphyrin with bromo-4-quinolones containing N-ethyl and N-d-ribofuranosyl substituents. The use of electrospray ionization tandem mass spectrometry showed important information about the fragmentation pathways of the new compounds. It was possible to distinguish between those compounds with the porphyrin moiety linked at the 6-position of the quinolone unit from their 7-substituted isomers. The new compounds showed to be good singlet oxygen generators. 相似文献
69.
Huang R Pomin VH Sharp JS 《Journal of the American Society for Mass Spectrometry》2011,22(9):1577-1587
Improved methods for structural analyses of glycosaminoglycans (GAGs) are required to understand their functional roles in
various biological processes. Major challenges in structural characterization of complex GAG oligosaccharides using liquid
chromatography-mass spectrometry (LC-MS) include the accurate determination of the patterns of sulfation due to gas-phase
losses of the sulfate groups upon collisional activation and inefficient on-line separation of positional sulfation isomers
prior to MS/MS analyses. Here, a sequential chemical derivatization procedure including permethylation, desulfation, and acetylation
was demonstrated to enable both on-line LC separation of isomeric mixtures of chondroitin sulfate (CS) oligosaccharides and
accurate determination of sites of sulfation by MS
n
. The derivatized oligosaccharides have sulfate groups replaced with acetyl groups, which are sufficiently stable to survive
MS
n
fragmentation and reflect the original sulfation patterns. A standard reversed-phase LC-MS system with a capillary C18 column
was used for separation, and MS
n
experiments using collision-induced dissociation (CID) were performed. Our results indicate that the combination of this
derivatization strategy and MS
n
methodology enables accurate identification of the sulfation isomers of CS hexasaccharides with either saturated or unsaturated
nonreducing ends. Moreover, derivatized CS hexasaccharide isomer mixtures become separable by LC-MS method due to different
positions of acetyl modifications. 相似文献
70.
Vitor RV Martins MC Figueiredo EC Martins I 《Analytical and bioanalytical chemistry》2011,400(7):2109-2117
A method constituted by molecularly imprinted solid-phase extraction (MISPE) with high-performance liquid chromatography coupled
to diode array detector (HPLC-DAD) was developed for cotinine analysis in saliva samples. For this purpose, the separation
was carried out with a C18 reversed-phase column at 20 °C. The mobile phase which was composed of a mixture of 09:91 (v/v) acetonitrile/phosphate buffer, pH 6.3, was delivered with isocratic flow rate at 1.4 mL min−1. Employing MISPE, the best conditions were achieved with 1.5 mL of saliva plus 1.5 mL of 0.1 mol L−1 of acetate buffer, pH 5.5, which were then passed through a cartridge previously conditioned with 2 mL acetonitrile, 2 mL
methanol, and 2 mL of 0.1 mol L−1 sodium acetate buffer, pH 5.5. The washing was carried out with 1 mL deionized water, 1 mL of 0.1 mol L−1 sodium hydroxide, and 1 mL hexane; finally; the cotinine elution was carried out with 3 mL methanol/water (97.5: 2.5, v/v). Linearity ranged from 30 to 500 ng mL−1 with r > 0.99. Intra-assay, interassay precision, and accuracy ranged from 3.1% to 10.1%, 5.2% to 15.9%, and 99.22% to 111.17%,
respectively. The detection and quantification limits were 10 and 30 ng mL−1, respectively. This investigation has provided a reliable method for routine cotinine determination in saliva, and it is
an important tool for monitoring cigarette smoke exposure in smokers. The method was applied in five smokers’ samples who
consumed around five to 20 cigarettes per day and the values of cotinine in saliva were from 66.7 to 316.16 ng mL−1. 相似文献