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91.
Bernd Berchtold Vasile Lozan Paul‐Gerhard Lassahn Christoph Janiak 《Journal of polymer science. Part A, Polymer chemistry》2002,40(21):3604-3614
Nickel(II) and palladium(II) complexes with α‐dioxime ligands dimethylglyoxime, diphenylglyoxime, and 1,2‐cyclohexanedionedioxime represent six new precatalysts for the polymerization of norbornene that can be activated with methylaluminoxane (MAO), the organo‐Lewis acid tris(pentafluorophenyl)borane [B(C6F5)3], and triethylaluminum (TEA) AlEt3. The palladium but not the nickel precatalysts could also be activated by B(C6F5)3 alone, whereas two of the three nickel precatalysts but none of the palladium systems are somewhat active with only TEA as a cocatalyst. It was possible to achieve very high polymerization activities up to 3.2 · 107 gpolymer/molmetal · h. With the system B(C6F5)3/AlEt3, the activation process can be formulated as the following two‐step reaction: (1) B(C6F5)3 and TEA lead to an aryl/alkyl group exchange and result in the formation of Al(C6F5)nEt3?n and B(C6F5)3?nEtn; and (2) Al(C6F5)nEt3?n will then react with the precatalysts to form the active species for the polymerization of norbornene. Variation of the B:Al ratio shows that Al(C6F5)Et2 is sufficient for high activation. Gel permeation chromatography indicated that it was possible to control the molar mass of poly(norbornene)s by TEA or 1‐dodecene as chain‐transfer agents; the molar mass can be varied in the number‐average molecular weight range from 2 · 103 to 9 · 105 g · mol?1. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3604–3614, 2002 相似文献
92.
M. Badea R. Olar D. Marinescu G. Vasile 《Journal of Thermal Analysis and Calorimetry》2006,85(2):285-288
This paper reports the
investigation of the thermal stability of a series of new complexes with mixed
ligands of the type M(dipy)(C3H3O2)2(H2O)y ((1) M: Mn, y=1; (2) M: Ni, y=2; (3) M: Cu, y=1; (4) M: Zn, y=2; dipy: 2,2’-dipyridine and C3H3O2
is acrylate anion). The thermal behaviour steps were investigated. The thermal
transformations are complex processes according to TG and DTG curves including
dehydration, oxidative condensation of acrylate and thermolysis processes.
The final products of decomposition are the most stable metal oxides. 相似文献
93.
Mihaela Badea Rodica Olar Dana Marinescu Veronica Lazar Carmen Chifiriuc Gina Vasile 《Journal of Thermal Analysis and Calorimetry》2009,97(2):781-785
This paper reports the investigation on the thermal stability of new complexes with mixed ligands of the type [Cd(NN)(C3H3O2)2(H2O)m]·nH2O [(1) NN: 1,10-phenantroline, m = 1, n = 0; (2) NN: 2,2′-bipyridine, m = 0, n = 1.5 and (C3H3O2): acrylate anion]. The IR data indicate a bidentate coordination mode for both heterocyclic amine and acrylate. The in vitro
qualitative and quantitative antimicrobial activity assays showed that the complexes exhibited variable antimicrobial activity
against planktonic as well as biofilm embedded Gram-negative (Escherichia coli, Klebsiella sp., Proteus sp., Salmonella sp., Shigella sp., Acinetobacter boumani, Pseudomonas aeruginosa), Gram-positive (Bacillus subtilis, Staphylococcus aureus) and fungal (Candida albicans) strains, reference and isolated ones from the hospital environment. The thermal behaviour steps were investigated
in synthetic air flow. The thermal transformations are complex processes according to TG and DTA curves including dehydration,
amine as well as acrylate thermolysis. The final products of decomposition are the most stable metal oxides. 相似文献
94.
Răzvan Şuteu Ciprian I. Raţ Cristian Silvestru Andrada Simion Natalia Candu Vasile I. Pârvulescu Anca Silvestru 《应用有机金属化学》2020,34(4):e5393
The compounds [2-(Me2NCH2)C6H4]2SbL (L = ONO2 ( 2 ), OSO2CF3 ( 3 )) and [PhCH2N(CH2C6H4)2]SbL (L = ONO2 ( 5 ), OSO2CF3 ( 6 )) were prepared by reacting [2-(Me2NCH2)C6H4]2SbCl ( 1 ) and [PhCH2N(CH2C6H4)2]SbCl ( 4 ), respectively, with the appropriate silver(I) salt in a 1:1 molar ratio. The new species 2 – 6 were structurally characterized in solution using multinuclear NMR and in the solid state using infrared spectroscopy. The solid-state structures for compounds 2 , 4 and 6, as well as for the hydrolysis ionic product [{2-(Me2N+HCH2)C6H4}{2-(Me2NCH2)C6H4}SbOH][CF3SO3]− ( 3h ) were determined using single-crystal X-ray diffraction. Medium to strong intramolecular N→ Sb interactions were observed in all these four compounds, thus resulting in hypercoordinated organoantimony(III) species 14-Sb-6 in 2 and 10-Sb-4 in the cation of 3h and in 4 and 6 . Compounds 1 – 6 and the starting amines PhCH2NMe2 and PhCH2N(CH2C6H4Br-2)2 were investigated as catalysts in the Henry (nitroaldol) addition of nitromethane to benzaldehyde. The activity of compounds 1 – 6 resulted as an effect of the cooperation of the positively charged antimony with the negatively charged nitrogen. 相似文献
95.
Ionel Danut Savu Sorin Vasile Savu Nicusor Alin Sirbu 《Journal of Thermal Analysis and Calorimetry》2014,115(2):1427-1437
Laser marking is based on the laser heating of the subjected material, the heating being below the melting temperature or thermal degradation starting point. Within and nearby the mark, the material is chemically, physically and mechanically affected. This means that the main characteristics are changing in such a way that the material is ageing. Thermal and mechanical analysis can be used to determine the modification of the material, which is important and necessary to know for predicting its use lifetime. This paper investigates the physical and mechanical modification of the polymer HDPE100, when laser marking is applied. Burst stress, elongation and relaxation modulus were determined for the base material, within the heat affected zone and within the laser burned mark. Information on the crystallization rate and on the elongation viscosity is also reported. According to the results, the polyethylene has very fast crystallization and that affects the marking process if lower than appropriate maintaining during heating process is applied. It becomes stabile after 0.23 min, when it is tested at 103 °C. The elongation viscosity was analysed and values of 105 Pa s were recorded for 10 s, which is a usual time of applying pressure. The performed analysis revealed about 10 % difference between the relaxation modulus of the irradiated and non-irradiated HDPE. 相似文献
96.
Meccanica - Based on Hamiltonian principle and a modified couple stress theory, a nonlinear differential equation of motion of electrostatically actuated microbeams is presented. The method of... 相似文献
97.
Paola Marzullo Zlata Boiarska Helena Pérez-Peña Anne-Catherine Abel Beatriz Álvarez-Bernad Daniel Lucena-Agell Prof. Dr. Francesca Vasile Prof. Dr. Maurizio Sironi Prof. Dr. Karl-Heinz Altmann Dr. Andrea E. Prota J. Fernando Díaz Prof. Dr. Stefano Pieraccini Prof. Dr. Daniele Passarella 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(2):e202103520
Maytansinol is a valuable precursor for the preparation of maytansine derivatives (known as maytansinoids). Inspired by the intriguing structure of the macrocycle and the success in targeted cancer therapy of the derivatives, we explored the maytansinol acylation reaction. As a result, we were able to obtain a series of derivatives with novel modifications of the maytansine scaffold. We characterized these molecules by docking studies, by a comprehensive biochemical evaluation, and by determination of their crystal structures in complex with tubulin. The results shed further light on the intriguing chemical behavior of maytansinoids and confirm the relevance of this peculiar scaffold in the scenario of tubulin binders. 相似文献
98.
Pârvulescu VI Pârvulescu V Endruschat U Filoti G Wagner FE Kübel C Richards R 《Chemistry (Weinheim an der Bergstrasse, Germany)》2006,12(8):2343-2357
Colloids embedded in a silica sol-gel matrix were prepared by using fully alloyed Pd-Au colloids, and pure Pd and Au colloids stabilized with tetraalkylammonium bromide following a modified sol-gel procedure with tetrahydrofuran (THF) as the solvent. Tetraethoxysilicate (TEOS) was used as the precursor for the silica support. The molar composition of the sol was TEOS/THF/H2O/HCl = 1:3.5:4:0.05 for the bimetallic Pd-Au and TEOS/THF/H2O/HCl = 1:4.5:4:0.02 for Pd and Au monometallic systems. After refluxing, the colloid was added as a 4.5 wt % solution in THF for Pd-Au, 10.2 wt % solution in THF for Pd and 8.4 wt % solution in THF for Au at room temperature. The gelation was carried out with vigorous stirring (4 days) under an Ar atmosphere. Following these procedures, bimetallic Pd-Au-SiO2 catalysts with 0.6 and 1 wt % metal, and monometallic Pd- and Au-SiO2 catalysts with 1 wt % metal were prepared. These materials were further treated following four different routes: 1) by simple drying, 2) in which the dried catalysts were calcined in air at 723 K and then reduced at the same temperature, 3) in which they were directly reduced in hydrogen at 723 K, and 4) in which the surfactant was extracted using an ethanol-heptane azeotropic mixture. The catalysts were characterized by nitrogen adsorption-desorption isotherms at 77 K, H2 chemisorption measurements, solid-state 1H, 13C, 29Si-CP/MAS-NMR spectroscopy, powder X-ray diffraction (XRD), small angle X-ray scattering (SAXS), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and 197Au M?ssbauer spectroscopy. The physical characterization by a combination of these techniques has shown that the size and the structural characteristics of the Pd-Au colloid precursor are preserved when embedded in an SiO2 matrix. Catalytic tests were carried out in selective hydrogenation of 3-hexyn-1-ol, cinnamaldehyde, and styrene. These data showed evidence that alloying Pd with Au in bimetallic colloids leads to enhanced activity and most importantly to improved selectivity. Also, the combination of the two metals resulted in catalysts that were very stable against poisoning, as was evidenced for the hydrogenation of styrene in the presence of thiophene. 相似文献
99.
Journaux Y Glaser T Steinfeld G Lozan V Kersting B 《Dalton transactions (Cambridge, England : 2003)》2006,(14):1738-1748
The ligating properties of the 24-membered macrocyclic dinucleating hexaazadithiophenolate ligand (L(Me))2- towards the transition metal ions Cr(II), Mn(II), Fe(II), Co(II), Ni(II) and Zn(II) have been examined. It is demonstrated that this ligand forms an isostructural series of bioctahedral [(L(Me))M(II)2(OAc)]+ complexes with Mn(II) (2), Fe(II) (3), Co(II) (4), Ni(II) (5) and Zn(II) (6). The reaction of (L(Me))2- with two equivalents of CrCl2 and NaOAc followed by air-oxidation produced the complex [(L(Me))Cr(III)H2(OAc)]2+ (1), which is the first example for a mononuclear complex of (L(Me))2-. Complexes 2-6 contain a central N3M(II)(mu-SR)2(mu-OAc)M(II)N3 core with an exogenous acetate bridge. The Cr(III) ion in is bonded to three N and two S atoms of (L(Me))2- and an O atom of a monodentate acetate coligand. In 2-6 there is a consistent decrease in the deviations of the bond angles from the ideal octahedral values such that the coordination polyhedra in the dinickel complex 5 are more regular than in the dimanganese compound 2. The temperature dependent magnetic susceptibility measurements reveal the magnetic exchange interactions in the [(L(Me))M(II)2(OAc)]+ cations to be relatively weak. Intramolecular antiferromagnetic exchange interactions are present in the Mn(II)2, Fe(II)2 and Co(II)2 complexes where J = -5.1, -10.6 and approximately -2.0 cm(-1) (H = -2JS1S2). In contrast, in the dinickel complex 5 a ferromagnetic exchange interaction is present with J = +6.4 cm(-1). An explanation for this difference is qualitatively discussed in terms of the bonding differences. 相似文献
100.