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51.
13C-NMR and 1H-NMR spectra of the Reformatsky reagent from t-butylbr moacetate, evidence a C-metallated species: within the limits of detectability of the methods, no O-metallated species can be detected in solution. 相似文献
52.
[reaction: see text] An efficient electrochemical synthesis of 5-methylene-1,3-oxazolidin-2-ones (2a-h) from acetylenic amines (1a-h) and carbon dioxide has been achieved by direct electrolysis of solution of MeCN and Et4NPF6 containing the amine, with subsequent CO2 bubbling and heating. The yields vary from good to excellent, the conditions are mild, and the use of toxic and harmful chemicals and catalysts is avoided. 相似文献
53.
Guido Sello Silvana Bernasconi Fulvia Orsini Patrizia Di Gennaro 《Tetrahedron: Asymmetry》2009,20(5):563-565
The cascade use of enzymatic activities allows for the preparation of enantiomerically pure epoxides. In particular, using whole-cell biocatalysts we can prepare both (?)-[3-(oxiran-2-yl)phenyl]methanol and (?)-3-(oxiran-2-yl)benzoic acid in one-pot, two or three steps procedure. The yield is quantitative and enantiomeric purity greater than 95%. The selected biocatalysts contain a styrene monoxygenase from Pseudomonas fluorescens ST and a naphthalene dihydrodiol dehydrogenase from P. fluorescens N3, cloned and expressed in Escherichia coli. 相似文献
54.
55.
Felix Latourte Xiaoding Wei Zechariah D. Feinberg Alban de Vaucorbeil Phuong Tran Gregory B. Olson Horacio D. Espinosa 《International Journal of Solids and Structures》2012,49(13):1573-1587
Martensitic and austenitic steel alloys were designed to optimize the performance of structures subjected to impulsive loads. The deformation and fracture characteristics of the designed steel alloys were investigated experimentally and computationally. The experiments were based on an instrumented fluid–structure interaction apparatus, in which deflection profiles are recorded using a shadow Moiré technique combined with high speed imaging. Fractographic analysis and post-mortem thickness reduction measurements were also conducted in order to identify deformation and fracture modes. The computational study was based on a modified Gurson damage model able to accurately describe ductile failure under various loading paths. The model was calibrated for two high performance martensitic steels (HSLA-100 and BA-160) and an austenitic steel (TRIP-120). The martensitic steel (BA-160) was designed to maximize strength and fracture toughness while the austenitic steel (TRIP-120) was designed to maximize uniform ductility, in other words, to delay necking instability. The combined experimental–computational approach provided insight into the relationships between material properties (strength, uniform ductility, and post-necking ductility) and blast resistance of structures. In particular, the approach allowed identification of material/structure performances by identifying impulse-center deflection behavior and the impulse leading to panel fracture. 相似文献
56.
Monica Orsini Isabella Chiarotto Mikhail N. Elinson Giovanni Sotgiu Achille Inesi 《Electrochemistry communications》2009,11(5):1013-1017
N-heterocyclic carbenes generated by electrochemical reduction under galvanostatic control of 1,3-dialkylimidazolium-based ionic liquids were employed as organocatalysts in the benzoin condensation reaction. Benzoin was isolated in a good yield (84%) by a catalytic amount of carbene (20%). The use of toxic, volatile molecular solvents as well as any addition of bases has been avoided. 相似文献
57.
A recently published paper1 reporting a new synthetic route to the ethylene glycol mono-ketal of cyclohexane-1,4-dione promted us to publish the results obtained in our laboratory. In fact we have developed a different synthesis of (2), starting from cyclohexane-1,4-diol (1), with overall yields higher than those reported in the above mentioned paper and without employment of any anhydrous solvent. 相似文献
58.
In this article, we describe a dynamic model of the three-dimensional eel swimming. This model is analytical and suited to
the online control of eel-like robots. The proposed solution is based on the Large Amplitude Elongated Body Theory of Lighthill
and a framework recently presented in Boyer et al. (IEEE Trans. Robot. 22:763–775, 2006) for the dynamic modeling of hyper-redundant robots. This framework was named “macro-continuous” since, at this macroscopic
scale, the robot (or the animal) is considered as a Cosserat beam internally (and continuously) actuated. This article introduces
new results in two directions. Firstly, it extends the Lighthill theory to the case of a self-propelled body swimming in three
dimensions, while including a model of the internal control torque. Secondly, this generalization of the Lighthill model is
achieved due to a new set of equations, which are also derived in this article. These equations generalize the Poincaré equations
of a Cosserat beam to an open system containing a fluid stratified around the slender beam. 相似文献
59.
Klaus Blaum Dietrich Beck Martin Breitenfeldt Sebastian George Frank Herfurth Alexander Herlert Alban Kellerbauer H.-Jürgen Kluge David Lunney Romain Savreux Stefan Schwarz Lutz Schweikhard Chabouh Yazidjian 《Hyperfine Interactions》2006,171(1-3):83-91
High-precision mass measurements as performed at the Penning trap mass spectrometer ISOLTRAP at ISOLDE/CERN are an important
contribution to the investigation of nuclear structure. Precise nuclear masses with less than 0.1 ppm relative mass uncertainty
allow stringent tests of mass models and formulae that are used to predict mass values of nuclides far from the valley of
stability. Furthermore, an investigation of nuclear structure effects like shell or sub-shell closures, deformations, and
halos is possible. In addition to a sophisticated experimental setup for precise mass measurements, a radioactive ion-beam
facility that delivers a large variety of short-lived nuclides with sufficient yield is required. An overview of the results
from the mass spectrometer ISOLTRAP is given and its limits and possibilities are described.
相似文献
60.
Rosely dos Reis Orsini Elder Moscardini Filho Lucildes Pita Mercuri Jivaldo do Rosário Matos Fátima Maria Sequeira de Carvalho 《Journal of Thermal Analysis and Calorimetry》2011,106(3):741-745
The better use of agricultural residues is expected, when they are mostly disposed of improperly and it is often burned in
the natural environment. This study of the thermal decomposition of residues was performed from the coffee crop for energy
purposes and in this case was used thermal analysis techniques for such assessment. The TG/DTG and DSC curves showed that
the thermal decomposition occurs in four consecutive events and it is predominantly exothermic. The first mass loss evidenced
in TG/DTG curves has an endothermic peak in DSC curve, which it can be associated with the water liberation of the material.
This first thermal event also can be related to the liberation of volatile compounds present in the sample, which is also
corroborated by the endothermic peak. The other events of mass loss are related with the thermal decomposition of the material.
This decomposition has an exothermic behavior, which is positively applied to the main aim of this scientific research: the
coffee straw use like biomass energy font. The thermoanalytical techniques were satisfactory in the characterization of this
material. 相似文献