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991.
Baciocchi E Bietti M D'Alfonso C Lanzalunga O Lapi A Salamone M 《Organic & biomolecular chemistry》2011,9(11):4085-4090
A kinetic study of the one electron oxidation of substituted ferrocenes (FcX: X = H, COPh, COMe, CO(2)Et, CONH(2), CH(2)OH, Et, and Me(2)) by a series of N-oxyl radicals (succinimide-N-oxyl radical (SINO), maleimide-N-oxyl radical (MINO), 3-quinazolin-4-one-N-oxyl radical (QONO) and 3-benzotriazin-4-one-N-oxyl radical (BONO)), has been carried out in CH(3)CN. N-oxyl radicals were produced by hydrogen abstraction from the corresponding N-hydroxy derivatives by the cumyloxyl radical. With all systems, the rate constants exhibited a satisfactory fit to the Marcus equation allowing us to determine self-exchange reorganization energy values (λ(NO˙/NO(-))) which have been compared with those previously determined for the PINO/PINO(-) and BTNO/BTNO(-) couples. Even small modification of the structure of the N-oxyl radicals lead to significant variation of the λ(NO˙/NO(-)) values. The λ(NO˙/NO(-)) values increase in the order BONO < BTNO < QONO < PINO < SINO < MINO which do not parallel the order of the oxidation potentials. The higher λ(NO˙/NO(-)) values found for the MINO and SINO radicals might be in accordance with a lower degree of spin delocalization in the radicals MINO and SINO and charge delocalization in the anions MINO(-) and SINO(-) due to the absence of an aromatic ring in their structure. 相似文献
992.
Steric control on the redox chemistry of (η5-C9H7)2Yb(II)(THF)2 by 6-aryl substituted iminopyridines
Trifonov AA Shestakov BG Gudilenkov ID Fukin GK Giambastiani G Bianchini C Rossin A Luconi L Filippi J Sorace L 《Dalton transactions (Cambridge, England : 2003)》2011,40(40):10568-10575
A steric control on the reductive capacity of ytterbocenes towards iminopyridine ligands is described. The reaction of (η(5)-C(9)H(7))(2)Yb(THF)(2) with a series of 6-organyl-2-(aldimino)pyridyl ligands (IPy) takes place with the replacement of two THF molecules by one IPy unit. In contrast to the rich reductive ytterbocene chemistry described in the presence of the unsubstituted (aldimino)pyridyl ligand, all 6-aryl substituted IPys scrutinized hereafter are involved into the metal coordination as neutral bidentate {N,N} or tridentate {N,N,S; N,N,O} ligands, with no changes of the metal oxidation state in the final complexes. A series of Yb(II) metallocene complexes of general formula (η(5)-C(9)H(7))(2)Yb(II)(η(2) or η(3))[2,6-(i)Pr(2)(C(6)H(3))N=CH(C(5)H(3)N)-6-R)] have been isolated and completely characterized. The stereo-electronic role of the aryl substituents in the IPy ligands on the ytterbocene redox chemistry has also been addressed. 相似文献
993.
994.
Alexandre G. S. Prado Sheila M. Evangelista Jurandir R. SouzaDe Jeane G. S. Matos Marco A. A. Souza Denise A. Oliveira Claudio Airoldi 《Journal of Thermal Analysis and Calorimetry》2011,106(2):431-436
A microcalorimetric method was applied to study microbial soil activity of ornamental flower (Dahlia pinnata) plantations when irrigated with potable water and wastewaters. The samples were irrigated with potable water PW sample (reference)
and treated wastewaters from Municipal Wastewater Treatment Station of Asa Norte in Brasilia City (Brazil). Three different
water treatments were applied to irrigate soil samples, named TW1, TW2, and TW3 samples. The increase of the microbial soil
activity observed in TW1 sample must have occurred because of the high amount of organic waste dissolved in wastewater used
for irrigation. This rise indicates that the present treated wastewater can affect natural life cycle. However, only a low
alteration in microbial soil activity was observed in the TW2 and TW3 samples, which suggests that these wastewater treatments
can be normally used to irrigate soils without bringing environmental consequences, once they offer a great opportunity to
upgrade and protect the environment. 相似文献
995.
Massimiliano D’Arienzo Maurizio Crippa Paolo Gentile Claudio Maria Mari Stefano Polizzi Riccardo Ruffo Roberto Scotti Laura Wahba Franca Morazzoni 《Journal of Sol-Gel Science and Technology》2011,60(3):378-387
Mesoporous Cr or Pt-doped WO3 thin films to be employed as ammonia gas sensors were prepared by a fast one-step sol–gel procedure, based on the use of
triblock copolymer as templating agent. The obtained films were constituted by aggregates of interconnected WO3 nanocrystals (20–50 nm) separated by mesopores with dimensions ranging between 2 and 15 nm. The doping metals, Pt and Cr,
resulted differently hosted in the WO3 mesoporous matrix. Chromium is homogeneously dispersed in the oxide matrix, mainly as Cr(III) and Cr(V) centers, as revealed
by EPR spectroscopy; instead platinum segregated as Pt (0) nanoparticles (4 nm) mainly included inside the WO3 nanocrystals. The semiconductor layers containing Pt nanoclusters revealed, upon exposure to NH3, remarkable electrical responses, much higher than Cr-doped and undoped layers, particularly at low ammonia concentration
(6.2 ppm). This behavior was attributed to the presence of Pt nanoparticles segregated inside the semiconductor matrix, which
act as catalysts of the N–H bond cleavage, decreasing the activation barrier in the ammonia dissociation. The role of the
mesoporous structure in influencing the chemisorption and the gas diffusion in the WO3 matrix appeared less decisive than the electronic differences between the two examined doping metals. The overall results
suggest that a careful combination between mesoporous architecture and metal doping can really promote the electrical response
of WO3 toward ammonia. 相似文献
996.
Depalo N Carrieri P Comparelli R Striccoli M Agostiano A Bertinetti L Innocenti C Sangregorio C Curri ML 《Langmuir : the ACS journal of surfaces and colloids》2011,27(11):6962-6970
Asymmetric binary nanocrystals (BNCs) formed by a spherical γ-Fe(2)O(3) magnetic domain epitaxially grown onto a lateral facet of a rodlike anatase TiO(2) nanorod have been functionalized with PEG-terminated phospholipids, resulting in a micellar system that enables the BNC dispersion in aqueous solution. The further processability of the obtained water-soluble BNC including PEG lipid micelles and their use in bioconjugation experiments has been successfully demonstrated by covalently binding to bovine serum albumin (BSA). The whole process has also been preliminarily performed on spherical iron oxide nanocrystals (NCs) and TiO(2) nanorods (NRs), which form single structural units in the heterostructures. Each step has been thoroughly monitored by using optical, structural, and electrophoretic techniques. In addition, an investigation of the magnetic behavior of the iron oxide NCs and BNCs, before and after incorporation into PEG lipid micelles and subsequently bioconjugation, has been carried out, revealing that the magnetic characteristics are mostly retained. The proposed approach to achieving water-soluble anisotropic BNCs and their bioconjugates has a large potential in catalysis and biomedicine and offers key functional building blocks for biosensor applications. 相似文献
997.
Funari SS Rebbin V Marzorati L di Vitta C 《Langmuir : the ACS journal of surfaces and colloids》2011,27(13):8257-8262
We synthesize and characterize alkylthiohydroquinones (ATHs) in order to investigate their interactions with lipid model membranes, POPE and POPC. We observe the formation of structures with different morphologies, or curvature of the lipid bilayer, depending on pH and increasing temperature. We attribute their formation to changes in the balance charge/polarity induced by the ATHs. Mixtures of ATHs with POPE at pH 4 form two cubic phases, P4(3)32 and Im3m, that reach a maximum lattice size at 40 °C while under basic conditions these phases only expand upon heating from room temperature. The cubic phases coexist with lamellar or hexagonal phases and are associated with inhomogeneous distribution of the ATH molecules over the lipid matrix. The zwitterionic POPC does not form cubic phases but instead shows lamellar structures with no clear influence of the 2,6-BATH. 相似文献
998.
Acquaroli LN Urteaga R Berli CL Koropecki RR 《Langmuir : the ACS journal of surfaces and colloids》2011,27(5):2067-2072
An experimental study on the capillary filling of nanoporous silicon with different fluids is presented. Thin nanoporous membranes were obtained by electrochemical anodization, and the filling dynamics was measured by laser interferometry, taking advantage of the optical properties of the system, related with the small pore radius in comparison to light wavelength. This optical technique is relatively simple to implement and yields highly reproducible data. A fluid dynamic model for the filling process is also proposed including the main characteristics of the porous matrix (tortuosity, average hydraulic radius). The model was tested for different ambient pressures, porous layer morphology, and fluid properties. It was found that the model reproduces well the experimental data according to the different conditions. The predicted pore radii quantitatively agree with the image information from scanning electron microscopy. This technique can be readily used as nanofluidic sensor to determine fluid properties such as viscosity and surface tension of a small sample of liquid. Besides, the whole method can be suitable to characterize a porous matrix. 相似文献
999.
Direct and competition ligand-based NMR experiments are often used in the screening of chemical fragment libraries against a protein target due to the high relative sensitivity of NMR for protein-binding events. A plethora of NMR methods has been proposed for this purpose. Two of these techniques are the (19)F T(2) filter and the (1)H selective T(2) filter experiments. Modifications of the pulse sequences of these experiments have resulted in a ~2-fold reduction in the experiment time thus allowing an increase in the screening throughput and making NMR an attractive technique for screening large compound collections. 相似文献
1000.
Oliveira SR Nogueira LJ Augusti R Stoianoff MA Aguilar CM Rocha WR Donnici CL 《Rapid communications in mass spectrometry : RCM》2012,26(3):377-384
Sodium adducts of six organosulfur‐α,ω‐ditetrazole compounds (Tz‐(CH2)n‐S(O)m‐(CH2)n‐Tz; where Tz = tetrazole ring; n = 2, 3; m = 0, 1, 2) were generated via electrospray ionization (ESI) and their fragmentation pattern assessed via collision‐induced dissociation (CID). Two main dissociation channels were observed: (a) losses of N2 and HN3 from the tetrazole rings; (b) cleavage of the C–S bond. The sulfoxides pass predominantly through the second fragmentation pathway, but for the sulfides and sulfones the tetrazole ring fragmentation occurs. Theoretical calculations at the B3LYP/6‐31 + G(d,p) level indicate that for all the adducts (sulfide, sulfoxide, and sulfone) the dissociation pathway that leads to product ions arising from loss of N2 was the most exothermic. Based on these results and assumptions, it was postulated that the dissociation of the sulfoxide adducts occurs under kinetic control (N2‐loss pathway via a much more energetic transition state). For the sulfide and sulfone adducts, on the other hand, the dissociation process takes place via a thermodynamically controlled process. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献