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131.
132.
Carmine Coluccini Yoke Mooi Ng Yves Ira A. Reyes Hsin-Yi Tiffany Chen Yit Lung Khung 《Molecules (Basel, Switzerland)》2020,25(22)
In this paper, a modified Cyclotriveratrylene was synthesized and linked to a branched Polyethylenimine, and this unique polymeric material was subsequently examined as a potential supramolecular carrier for Doxorubicin. Spectroscopic analysis in different solvents had shown that Doxorubicin was coordinated within the hollow-shaped unit of the armed Cyclotriveratrylene, and the nature of the host–guest complex revealed intrinsic Van der Waals interactions and hydrogen bonding between the host and guest. The strongest interaction was detected in water because of the hydrophobic effect shared between the aromatic groups of the Doxorubicin and Cyclotriveratrylene unit. Density functional theory calculations had also confirmed that in the most stable coordination of Doxorubicin with the cross-linked polymer, the aromatic rings of the Doxorubicin were localized toward the Cyclotriveratrylene core, while its aliphatic chains aligned closer with amino groups, thus forming a compact supramolecular assembly that may confer a shielding effect on Doxorubicin. These observations had emphasized the importance of supramolecular considerations when designing a novel drug delivery platform. 相似文献
133.
CáRDENAS Carlos MU?OZ Macarena CONTRERAS Julia AYERS Paul W. GóMEZ Tatiana FUENTEALBA Patricio 《物理化学学报》2018,34(6):631-638
Chemical reactivity towards electron transfer is captured by the Fukui function.However,this is not well defined when the system or its ions have degenerate or pseudo-degenerate ground states.In such a case,the first-order chemical response is not independent of the perturbation and the correct response has to be computed using the mathematical formalism of perturbation theory for degenerate states.Spatialpseudo-degeneracy is ubiquitous in nanostructures with high symmetry and totally extended systems.Given the size of these systems,using degenerate-state perturbation theory is impractical because it requires the calculation of many excited states.Here we present an alternative to compute the chemical response of extended systems using models of local softness in terms of the local density of states.The local softness is approximately equal to the density of states at the Fermi level.However,such approximation leaves out the contribution of inner states.In order to include and weight the contribution of the states around the Fermi level,a model inspired by the long-range behavior of the local softness is presented.Single wall capped carbon nanotubes(SWCCNT) illustrate the limitation of the frontier orbital theory in extended systems.Thus,we have used a C360 SWCCNT to test the proposed model and how it compares with available models based on the local density of states.Interestingly,a simple Hü ckel approximation captures the main features of chemical response of these systems.Our results suggest that density-of-states models of the softness along simple tight binding Hamiltonians could be used to explore the chemical reactivity of more complex system,such a surfaces and nanoparticles. 相似文献
134.
Hiren Solanki Carlos Angulo-Preckler Kevin Calabro Navdeep Kaur Perrine Lasserre Bastien Cautain Mercedes de la Cruz Fernando Reyes Conxita Avila Olivier P. Thomas 《Tetrahedron letters》2018,59(36):3353-3356
Following ecological and chemical screenings, the Antarctic sponge Phorbas areolatus was chemically investigated for the first time. Three new suberitane derivatives named isosuberitenone B, 19-episuberitenone B, and isoxaspirosuberitenone were identified together with the known compounds suberitenones A and B, and oxaspirosuberitenone after a thorough inspection of their NMR data. These compounds were found to exhibit moderate cytotoxic activity and their presence in this sponge rules out their use as a chemotaxonomic marker for Suberites sponges. 相似文献
135.
Lenys Fernández Patricio Espinoza-Montero José Alvarado Hicher Zambrano Patricio Carrera Pablo Pozo 《International journal of environmental analytical chemistry》2018,98(9):844-858
The development and evaluation of a cathode consisting of a gold electrode covered by a polyaniline film, PANI/Au modified electrode, for electrochemical generation of arsine is described. The efficiency of arsine production using the new electrode was ascertained by comparison with corresponding hydride generation atomic absorption spectroscopy determinations of arsenic (As) in aqueous standards. The PANI/Au modified electrodes provide better sensitivity, accuracy and precision than the pure Au cathodes. The PANI/Au cathodes were prepared by controlled electrodeposition cycles of polyaniline films on top of Au electrodes. Cathodes obtained after 10 electrodeposition cycles showed the best performance, while the ones obtained after five voltammetry cycles produced films too thin and those obtained after 20 voltammetry cycles produced films too thick for the purpose of this work. Under optimised conditions, the As limit of detection in aqueous solutions, according to the (3σ) criterion, was 2.48 µg L?1. For accuracy determination, the modified electrode was applied to quantification of As(III) in acidified aqueous solutions of the certified standard reference material, NIST SRM 1643d, and in well-water samples containing possible interfering ions. Application of the Student’s t-test showed no significant difference between the expected and obtained results of the NIST SRM standard analysis at the 95% confidence level. Values for six replicate determinations of As(III) in the well-water samples showed close agreement with values obtained by analyses using hydride generation atomic absorption. Recoveries were in the range of 95–105% at test for acceptable accuracy in the analysis of real samples. 相似文献
136.
M. Carmen Barral Santiago Herrero Reyes Jiménez-Aparicio M. Rosario Torres Francisco A. Urbanos 《Journal of organometallic chemistry》2008,693(8-9):1597-1604
The reaction of [Ru2(O2CMe)(DPhF)3(H2O)]BF4 (DPhF = N,N′-diphenylformamidinate) with CO gas leads to [Ru2(O2CMe)(DPhF)3(CO)]BF4 (1), that is the first isolated carbonyl complex containing the Ru25+ unit. The nitrosyl analogue [Ru2(O2CMe)(DPhF)3(NO)]BF4 (2) is prepared by reaction of Ru2Cl(O2CMe)(DPhF)3 with NOBF4. However, the attempts to obtain the cyanide derivative by reaction of Ru2Cl(O2CMe)(DPhF)3 or [Ru2(O2CMe)(DPhF)3(H2O)]BF4 with NaCN were unsuccessful. The structure of compounds 1 · CH2Cl2 and 2 · CH2Cl2 are described. Both compounds are isomorphous. The magnetic measurements at variable temperature demonstrate that 1 is paramagnetic with one unpaired electron in all range of temperature, in contrast to the three unpaired electrons usually present in Ru25+ complexes. The analogous nitrosyl compound 2 is diamagnetic. 相似文献
137.
Bravo Rodríguez V Jurado Alameda E Martínez Gallegos JF Reyes Requena A García López AI 《Colloids and surfaces. B, Biointerfaces》2008,65(1):92-97
The formation of complexes between soluble potato starch and three commercial alkyl polyglycosides has been studied by means of surface tension measurements at 37 degrees C. All surfactants assayed form complexes with starch, the quantity of bound surfactant being proportional to the amount of starch present in the solution. For all alkyl polyglycoside-starch systems tested, there is a direct proportional relationship between the bound and total surfactant concentrations, so that the formation of the surfactant-starch complex continues until the minimum surface tension is reached without detectable starch saturation prior to the occurrence of surfactant micelles. Binding isotherms and Scatchard plots support the idea that alkyl polyglycosides are bound to amylose by positive cooperative binding and to amylopectin by non-cooperative Langmuir-type binding. 相似文献
138.
Ghumaan S Sarkar B Maji S Puranik VG Fiedler J Urbanos FA Jimenez-Aparicio R Kaim W Lahiri GK 《Chemistry (Weinheim an der Bergstrasse, Germany)》2008,14(34):10816-10828
The quinonoid ligand-bridged diruthenium compounds [(acac)(2)Ru(mu-L(2-))Ru(acac)(2)] (acac(-)=acetylacetonato=2,4-pentanedionato; L(2-)=2,5-dioxido-1,4-benzoquinone, 1; 3,6-dichloro-2,5-dioxido-1,4-benzoquinone, 2; 5,8-dioxido-1,4-naphthoquinone, 3; 2,3-dichloro-5,8-dioxido-1,4-naphthoquinone, 4; 1,5-dioxido-9,10-anthraquinone, 5; and 1,5-diimido-9,10-anthraquinone, 6) were prepared and characterized analytically. The crystal structure analysis of 5 in the rac configuration reveals two tris(2,4-pentanedionato)ruthenium moieties with an extended anthracenedione-derived bis(ketoenolate) pi-conjugated bridging ligand. The weakly antiferromagnetically coupled {Ru(III)(mu-L(2-))Ru(III)} configuration in 1-6 exhibits complicated overall magnetic and EPR responses. The simultaneous presence of highly redox-active quinonoid-bridging ligands and of two ruthenium centers capable of adopting the oxidation states +2, +3, and +4 creates a large variety of possible oxidation state combinations. Accordingly, the complexes 1-6 exhibit two reversible one-electron oxidation steps and at least two reversible reduction processes. Shifts to positive potentials were observed on introduction of Cl substituents (1-->2, 3-->4) or through replacement of NH by O (6-->5). The ligand-to-metal charge transfer (LMCT) absorptions in the visible region of the neutral molecules become more intense and shifted to lower energies on stepwise reduction with two electrons. On oxidation, the para-substituted systems 1-4 exhibit monocation intermediates with intervalence charge transfer (IVCT) transitions of Ru(III)Ru(IV) mixed-valent species. In contrast, the differently substituted systems 5 and 6 show no such near infrared (NIR) absorption. While the first reduction steps are thus assigned to largely ligand-centered processes, the oxidation appears to involve metal-ligand delocalized molecular orbitals with variable degrees of mixing. 相似文献
139.
Ruiz N Reyes E Vicario JL Badía D Carrillo L Uria U 《Chemistry (Weinheim an der Bergstrasse, Germany)》2008,14(30):9357-9367
The organocatalytic conjugate addition of different aldehydes to beta-nitroacrolein dimethyl acetal, generating the corresponding highly functionalized nitroaldehydes in high yields and with high stereoselectivities, has been studied in detail. These transformations have been achieved by using both readily available starting materials in a 1:1 ratio as well as commercially available catalysts at a 10 mol % catalyst loading. Furthermore, a very short and efficient protocol has been devised for the preparation of highly enantioenriched pyrrolidines containing two or three contiguous stereocenters starting from the obtained Michael adducts. 3,4-Disubstituted pyrrolidines have been obtained in a single step by Zn-mediated chemoselective reduction of the nitro group followed by intramolecular reductive amination, and trisubstituted homoproline derivatives have been prepared by means of an olefination reaction and a cascade process involving chemoselective reduction of the nitro group followed by a fully diastereoselective intramolecular aza- Michael reaction. 相似文献
140.
Cabrera S Reyes E Alemán J Milelli A Kobbelgaard S Jørgensen KA 《Journal of the American Chemical Society》2008,130(36):12031-12037
It is shown that racemic oxazolones are excellent reagents for the synthesis of chiral quaternary amino acids and its derivatives by the diastereo- and enantioselective nucleophilic addition to alpha,beta-unsaturated aldehydes catalyzed by diarylprolinol silyl ethers. The scope of this new organocatalytic reaction is demonstrated for different oxazolones having aromatic and alkyl groups at the reactive carbon atom and different aromatic and aliphatic substituted alpha,beta-unsaturated aldehydes, for which the stereoselective reaction proceeds with good yield, moderate to good to very high diastereoselectivity, and very high enantioselectivity. The potential of the reaction is shown for the synthesis of optically active alpha,alpha-disubstituted alpha-amino acids, alpha-quaternary proline derivatives, amino alcohols, lactams, and tetrahydropyranes. Furthermore, we have calculated by DFT-methods the transition-state structures that account for both the diastereo- and enantioselectivity observed for the addition of oxazolones to the alpha,beta-unsaturated aldehydes. For one class of compounds, the stereoselectivity is controlled by a hydrogen-bonding interaction of the enolate-form of the oxazolone with an ortho-hydroxy-phenyl substituent of the alpha,beta-unsaturated aldehyde, whereas the benzhydryl-protecting group in the oxazolone determines the diastereo- and enantioselectivity in a more general manner for both aromatic and aliphatic alpha,beta-unsaturated aldehydes. 相似文献