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Daniele Mazza Maria Lucco-Borlera Esterina Lepore Silvia Ronchetti 《Journal of Thermal Analysis and Calorimetry》1996,46(6):1625-1632
A calorimetric method is proposed to evaluate the catalytic activity of a solid catalyst with respect to the exothermic oxidation of Volatile Organic Compounds (VOC).This method employs a differential thermal analyzer in which an inert reference and a catalytically active sample are both fluxed at a constant rate with a reactive gaseous mixture composed of an inert gas (N2 90% vol.), oxygen and VOC, the last typically 900 to 5000 ppm. While the temperature is varied according to a predefined cycle, the output signal due to the exothermic reaction on the catalyst is continuously recorded. The design of the test chamber, the amount of catalyst, the shape of the holders and finally the flow rate and composition of the gaseous mixture should be carefully selected in order to achieve reproducible results. 相似文献
54.
The orthogonal syn and anti isomers, originated by the restricted rotation about the Ar-C(O)Bu(t) single bonds in 1,4-bis(2,2-dimethylpropanoyl)durene (2e), have been separated by preparative thin layer chromatography. In solution they reach an equilibrium where the syn-anti ratio depends upon the polarity of the solvent. This allowed us to assign the anti structure, which has a null dipole moment, to the least retained isomer. The free energy of activation (DeltaG) for the interconversion was found to be 22.5 kcal mol(-)(1), a value high enough for identifying these species as configurational isomers. When less hindered derivatives, also having two RCO (R = Pr(i), Et, Me) substituents in the positions 1,4 of the durene moiety, were examined, the syn and anti forms could be detected only at low temperature by means of NMR spectroscopy. The corresponding interconversion barriers (DeltaG = 13.4, 11.7, 10.9 kcal mol(-)(1), respectively) are, in fact, much lower than for R = Bu(t), indicating that in these cases we are dealing with conformational rather than with configurational isomers. 相似文献
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Bruno Danieli Giordano Lesma Daniele Passarella Davide Prosperi Alessandra Silvani Ezio Bombardelli 《Helvetica chimica acta》1999,82(9):1502-1508
In an attempt to use 3,5-di(tert-butyl)-1,2-benzoquinone for the oxidative deamination of N-deacetylcolchicine ( 4 ) and N-deacetylthiocolchicine (=N-deacetyl-10-demethoxy-10-(methylthio)colchicine; 5 ) to give the corresponding ketones 2 and 3 , the 2H-1,4-benzoxazine-type adducts 8 / 9 and 11 / 12 , respectively, were formed instead, showing a new and unexpected behavior of Corey's reagent. The adducts were separated and spectroscopically characterized, and a plausible scheme of formation is reported. 相似文献
57.
Daniele Bianchi Rossella Bortolo Rino D'Aloisio Marco Ricci 《Angewandte Chemie (International ed. in English)》1999,38(5):706-708
Effective and stable Pd catalysts for the biphasic synthesis of hydrogen peroxide from carbon monoxide, oxygen, and water [Eq. (a)] can be obtained by the right choice of bidentate nitrogen ligand. The best turnover numbers (578) for this reaction have been achieved with palladium complexes with 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline ligands. 相似文献
58.
Daniele Cauzzi Claudia Graiff Chiara Massera Giovanni Predieri Antonio Tiripicchio 《Journal of Cluster Science》2001,12(1):259-271
The reaction of [Ru3(CO)12] with Ph2(pyth)PSe (pyth=5-(2-pyridyl)-2-thienyl) allows to obtain two novel clusters [Ru3(3-Se)2(CO)7{P(pyth)Ph2}2] 1 and [Ru3(3-Se)(-PPh2)(-pyth)(CO)6{P(pyth)Ph2}] 2 in satisfactory yields. The first one exhibits the well-known bicapped, open triangular, 50-electron nido-core, whereas 2, whose crystal structure has been determined, shows the rather rare Ru3Se tetrahedron with the Ph2P and pyth fragments as side-bridging ligands. Morever cluster 2 belongs to the exiguous family of selenido-phosphido clusters not easily achievable by other routes. 相似文献
59.
This work reports a potentiometric, calorimetric and spectropolarimetric ultraviolet circular dichroism (UV/CD) study of the interaction of l-malic acid with alkaline metals or (poly)ammonium (methylamine, ethylenediamine, diethylenetriamine, triethylenetetramine, spermine, tetraethylenepentamine and pentaethylenehexamine) cations. Stability data (logK, DeltaG(0)) were obtained potentiometrically for the l-malic acid with (poly)ammonium cations systems; calorimetric measurements (25 degrees C) made it possible to obtain DeltaH(0) and TDeltaS(0) values for the complexes formed in the systems under examination. logK values calculated (for the reaction: H(i)A(i+)+H(j)L((j-z))=ALH(r)((i+j-z)), with r=i+j) range between 0.8 and 4.6, i.e., the interactions are from weak to fairly strong while maximum stability for each system is given by the species with the highest z(anion)xz(cation) (z=charge) value. Enthalpy changes associated with reactions H(n)A(n+)+L(2-)=ALH(n)((n-2)) and H(n)A(n+)+HL(-)=ALH(n+1)((n-1)) are always positive and increase progressively with n. The same is valid for T DeltaS(0) values, which indicate that these species are entropically stabilized, as expected for electrostatic interactions. It was verified that the UV/CD signal depends on both ionic medium and ionic strength value; for comparison, we used the l-malic acid signal recorded in tetramethylammonium chloride as baseline background salt (as in potentiometry). UV/CD spectra were recorded for solutions containing both cationic and anionic species. When the cation was a protonated polyamine, CD spectra calculations were performed for most stable ion pairs: the results show remarkable differences in Deltaepsilon (dm(3) mol(-1) cm(-1)) values at 205 nm (which is the l-malate UV/CD lambda(max)) between the chiral ligand and its complex with a polyamine. 相似文献
60.
Érica Aparecida de Oliveira Bluma Linkowski Faintuch Daniele Seo Angélica Bueno Barbezan Ana Funari Roselaine Campos Targino Ana Maria Moro 《Applied biochemistry and biotechnology》2018,185(4):863-874
Early and accurate detection of primary or metastatic tumors is of great value in staging, treatment management, and prognosis. Tumor angiogenesis plays an essential role in the growth, invasion, and metastatic spread of solid cancers, and so, is a promising approach for tumor imaging. The GX1 (CGNSNPKSC) peptide was identified by phage display library and has been investigated as a marker for human cancers. This study aims to evaluate the 99mTc-HYNIC-PEG4-c (GX1) as a biomarker for tumor imaging. Our results showed that GX1 specifically binds to tumor cells in vitro. SKMEL28 and MDA-MB231 cells achieved total binding peak at 60 min of incubation. For B16F10 and MKN45 cells, the total and specific binding were similar during all time points, while A549 cell line showed rapid cellular total uptake of the tracer at 30 min of incubation. Biodistribution showed low non-specific uptakes and rapid renal excretion. Melanoma tumors showed enhanced GX1 uptake in animal model at 60 min, and it was significantly blocked by cold peptide. The radiotracer showed tumor specificity, especially in melanomas that are highly vascularized tumors. In this sense, it should be considered in future studies, aiming to evaluate degree of angiogenesis, progression, and invasion of tumors. 相似文献