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141.
142.
Carlo Scapolla Giuliana Cangemi Sebastiano Barco Laura Barbagallo Daniela Bugnone Angelo Maffia Giovanni Melioli Aldo Profumo Umberto Benatti Gianluca Damonte 《Journal of mass spectrometry : JMS》2012,47(7):816-824
The levels of urinary catecholamine metabolites, such as homovanillic acid (HVA) and vanillylmandelic acid, are routinely used as a clinical tool in the diagnosis and follow‐up of neuroblastoma (NB) patients. Recently, in the Clinical Pathology Laboratory Unit of G. Gaslini Children Hospital, a commercial method that employs liquid chromatography coupled to electrochemical detection (LC‐EC) has been introduced for the measurement of these metabolites in the routine laboratory practice. Using this LC‐EC method, an unknown peak could be observed only in samples derived from NB patients. To investigate the nature of this peak, we used a combination of liquid chromatography‐time‐of‐flight mass spectrometry (LC‐TOF‐MS) and liquid chromatography‐ion trap tandem mass spectrometry (LC‐IT‐MS). The first approach was used to obtain the elemental composition of the ions present in this new signal. To get additional structural information useful for the elucidation of unknown compounds, the ion trap analyzer was exploited. We were able to identify not just one, but three unknown signals in urine samples from NB patients which corresponded to three conjugated products of HVA: HVA sulfate and two glucuronoconjugate isomers. The enzymatic hydrolysis with β‐glucuronidase confirmed the proposed structures, while the selective alkaline hydrolysis allowed us to distinguish the difference between phenol‐ and acyl‐glucuronide of HVA. The latter was the unknown peak observed in LC‐EC separations of urine samples from NB patients. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
143.
Giorgio Colombo Gianluca Ottolina Giacomo Carrea 《Monatshefte für Chemie / Chemical Monthly》2000,131(6):527-547
Summary. In this article we review how molecular modeling techniques can be used to shed some light on the influence of organic solvents
on the molecular characteristics of proteins and enzymes. Molecular dynamic simulations on bovine pancreas trypsin inhibitor,
chymotrypsin, and subtilisin make it possible to get a deeper understanding into how increased intramolecular interactions
improve conformational rigidity, thus explaining the lower reactivity and the higher thermostability of enzymes in non-aqueous
media. The application of thermodynamics-based models allows first qualitative predictions on the selectivity of many reaction
types; however, the application of quantum mechanical/molecular mechanical methods is required for the development of quantitative
models of actual reactivity patterns.
Received November 18, 1999. Accepted (revised) February 8, 2000 相似文献
144.
Gianluca Bianchini Valentina Brombin Pasquale Carlino Enrico Mistri Claudio Natali Gian Marco Salani 《Molecules (Basel, Switzerland)》2021,26(7)
In the Adriatic lagoons of northern Italy, manila clam (Ruditapes philippinarum) farming provides important socio-economic returns and local clams should be registered with the Protected Designations of Origin scheme. Therefore, there is a need for the development of rapid, cost-effective tests to guarantee the origin of the product and to prevent potential fraud. In this work, an elemental analysis (EA) coupled with isotope ratio mass spectrometry (IRMS) was employed to identify the isotopic fingerprints of clams directly collected onsite in three Adriatic lagoons and bought at a local supermarket, where they exhibited certification. In particular, a multivariate analysis of C/N, δ13C and δ15N in manila clam tissues as well as δ13C in shells and 13C (calculated as δ13Cshell–δ13Ctissues) seems a promising approach for tracking the geographical origin of manila clams at the regional scale. 相似文献
145.
The use of catalytic methylrhenium trioxide (MTO) and urea hydrogen peroxide in room temperature ionic liquid for the hydroxyglycosylation with glycals in a domino fashion is reported. Excellent conversions and good selectivities for the epoxidation reaction were observed. Application to the synthesis of glycosylphosphates, good glycosyl donors, has been studied. 相似文献
146.
Gianluca Allemandi Monica Capone Salvatore Capozziello Mauro Francaviglia 《General Relativity and Gravitation》2006,38(1):33-60
The debate on the physical relevance of conformal transformations can be faced by taking the Palatini approach into account
gravitational theories. We show that conformal transformations are not only a mathematical tool to disentangle gravitational
and matter degrees of freedom (passing from the Jordan frame to the Einstein frame) but they acquire a physical meaning considering
the bi-metric structure of Palatini approach which allows to distinguish between spacetime structure and geodesic structure.
These facts are relevant at least at cosmological scales, while at small scale (i.e. in the spacetime regions relevant for
observations) the conformal factor is slowly varying and its effects are not relevant. Examples of higher-order and non-minimally
coupled theories are worked out and relevant cosmological solutions in Einstein frame and Jordan frame are discussed showing
that also the interpretation of cosmological observations can drastically change depending on the adopted frame. 相似文献
147.
The philosophy of the applications of the partial least-squares method in chemistry is outlined. The method is compared with multiple regression and illustrated by means of examples in various fields of chemistry. 相似文献
148.
Castellini E Lusvardi G Malavasi G Menabue L 《Journal of colloid and interface science》2005,292(2):322-329
The adsorption of hexametaphosphate ion, an important deflocculant used in the ceramic industry, from aqueous solutions onto kaolinite has been studied at different temperatures. The adsorption isotherm follows the Langmuir model: the thermodynamic parameters DeltaG(ads)(0), DeltaH(ads)(0), and DeltaS(ads)(0) were calculated and found to be consistent with an interaction model involving the formation of an inner-sphere complex between HMP and aluminol groups. Also, the dependence of the adsorption behavior on the kaolinite volume fraction has been studied and discussed in term of association processes between the clay particles. 相似文献
149.
Giorgi G Salvini L Attanasi OA Guidi B Santeusanio S 《Journal of mass spectrometry : JMS》2002,37(2):169-178
Electron ionisation mass spectrometry was usefully used to characterize structurally 2-aryl-5-acetylthiazole derivatives in the gas phase. The compounds show characteristic fragmentation pathways depending on the chemical nature of the substituent at position 2, consisting mainly in the cleavage of both the 1,2- and 3,4-bonds of the thiazole ring. Liquid secondary ion mass spectrometry was applied to study the effects of protonation on the gas-phase unimolecular reactions of this class of compound. Tandem mass spectrometric experiments, carried out on molecular and protonated molecular ions, and also on fragment ions produced in the source, allowed the elucidation of gas-phase decompositions of low-internal energy ions. 相似文献
150.
Gianluca Melillo Lorella Izzo Roberto Centore Angela Tuzi Alexander Z. Voskoboynikov Leone Oliva 《Journal of molecular catalysis. A, Chemical》2005,230(1-2):29-33
The meso ansa zirconocene with dimethylsilyl bridge, activated by methylalumoxane, catalyses the ethylene polymerization, producing ethyl-branched polyethylene. With respect to the polymers obtained with the previously investigated meso zirconocenes, we have found higher branching amount and lower molecular weight. The rapid β-H transfer from the growing chain to the coordinated monomer could account for both these features of the polymer. The investigation on the structural parameters of the complex, through X-ray diffraction analysis, and on the electrophilicity of the cationic center, through NMR experiments, suggests, as a possible rationalization of this behavior, the obstruction in the inward site. 相似文献