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321.
E. M. Kozinets G. A. Silantyev N. V. Belkova E. S. Shubina R. Poli E. Manoury 《Russian Chemical Bulletin》2013,62(3):751-757
Rhodium complexes with the planar chiral phosphinoferrocenyl thioether ligands [Rh(P,SR)(diene)X] (R = Me, But, Ph, Bn, diene is cyclooctadiene (COD) or norbornadiene (NBD), X = Cl, BF4) catalyze hydrogenation of ketones, imines, and heteroaromatic compounds; in the case of acetophenone, the enantioselectivity reached 60% ee. Similar iridium complexes demonstrate a good activity in the hydrogenation of imines, the maximal enantioselectivity in the case of N-phenyl-N-(1-phenylethylidene)amine was about 40% ee. 相似文献
322.
Vera Bernardoni Eleonora Cuccia Giulia Calzolai Massimo Chiari Franco Lucarelli Dario Massabò Silvia Nava Paolo Prati Gianluigi Valli Roberta Vecchi 《X射线光谱测定》2011,40(2):79-87
The knowledge of size‐segregated elemental concentrations in atmospheric particulate matter (PM) gives a useful contribution to the complete chemical characterisation; this information can be obtained by sampling with multi‐stage cascade impactors. In this work, samples were collected using a low‐pressure 12‐stage Small Deposit Impactor and a 13‐stage rotating Micro Orifice Uniform Deposit Impactor?. Both impactors collect the aerosol in an inhomogeneous geometry, which needs a special set‐up for X‐ray analysis. This work aims at setting up an energy dispersive X‐ray fluorescence (ED‐XRF) spectrometer to analyse quantitatively size‐segregated samples obtained by these impactors. The analysis of cascade impactor samples by ED‐XRF is not customary; therefore, as additional consistency test some samples were analysed also by particle‐induced X‐ray emission (PIXE), which is more frequently applied to size‐segregated samples characterised by small PM quantities. A very good agreement between ED‐XRF and PIXE results was obtained for all the detected elements in samples collected with both impactors. The good inter‐comparability proves that our methodology is reliable for analysing size‐segregated samples by ED‐XRF technique. The advantage of this approach is that ED‐XRF is cheaper, easier to use, and more widespread than PIXE, thus promoting an intensive use of multi‐stage impactors. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
323.
D. Hojman M.A. Cardona D.R. Napoli S.M. Lenzi C.A. Ur G. Lo Bianco C.M. Petrache M. Axiotis D. Bazzacco J. Davidson M. Davidson M. De Poli G. de Angelis E. Farnea T. Kroell S. Lunardi N. Marginean T. Martınez R. Menegazzo B. Quintana C. Rossi Alvarez 《The European Physical Journal A - Hadrons and Nuclei》2001,10(3):245-248
High-spin states in 178Ir were investigated by means of in-beam γ-ray spectroscopy techniques using the multidetector array GASP. Excited states
of 178Ir were populated through the 159Tb(24Mg, 5n) fusion-evaporation reaction at E(24
Mg) = 131-141 MeV. Several rotational bands were observed. Among them, the πi
13/2⊗νi
13/2 structure has been identified up to spin 36 ?. This band exhibits an anomalous signature splitting and a signature inversion
around spin 25 ?.
Received: 13 December 2000 / Accepted: 11 April 2001 相似文献
324.
Beccalli EM Broggini G Martinelli M Masciocchi N Sottocornola S 《Organic letters》2006,8(20):4521-4524
A simple and efficient entry to new tetrahydroisoquinolines 4-spiroannulated to a five-membered heterocyclic ring has been achieved starting from secondary N-allylamines and involving sequential 2-iodobenzylation/intramolecular Heck reaction/1,3-dipolar cycloaddition. A variety of Heck cyclization conditions were surveyed. When using Pd(PPh(3))(4) as catalyst, stable sigma-alkylpalladium iodide complexes were isolated and characterizated. 相似文献
325.
326.
Gianluigi Veglia Maurizio Delfini Maria Rosaria Del Giudice Elena Gaggelli Gianni Valensin 《Journal of magnetic resonance (San Diego, Calif. : 1997)》1998,130(2):281-286
1H NMR studies were performed on two β-carboline derivatives interacting with human serum albumin. The spin–lattice relaxation rates of the two derivatives, having side chains of different length and polarity, were used to demonstrate a diverse motional behavior in solution together with slightly different relaxation pathways. Single- and double-selective excitation made it possible to evaluate dynamics in the free and protein-bound states. Occurrence of a relatively long hydrophilic chain interacting with the proton-acceptor nitrogen of the β-carboline moiety was shown to yield lower association constants, slower dissociation rates, and diverse interacting modes with the indole hydrophobic site of the protein. 相似文献
327.
328.
Arylation of various sulfenate anions generated from beta-sulfinyl esters by retro-Michael reaction in the presence of palladium(0) and enantiopure ligands gave the corresponding aryl sulfoxides in enantio-enriched form. The Josiphos-type ligand (R)-(S)-PPF-t-Bu2 turned out to be the best ligand tested, allowing ee's up to 83% in a predictable sense. 相似文献
329.
ATRP/OMRP/CCT Interplay in Styrene Polymerization Mediated by Iron(II) Complexes: A DFT Study of the α‐Diimine System 下载免费PDF全文
Prof. Rinaldo Poli Prof. Michael P. Shaver 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(52):17530-17540
A DFT study of various model systems has addressed the interference of catalytic chain transfer (CCT) as a function of the R2 substituent in the atom‐transfer radical polymerization (ATRP) of styrene catalyzed by [FeCl2(R1N?C(R2)?C(R2)?NR1)] complexes. All model systems used R1=CH3 in place of the experimental Cy and tBu substituents and 1‐phenylethyl in place of the polystyrene (PS) chain. A mechanistic investigation of 1) ATRP activation, 2) radical trapping in organometallic‐mediated radical polymerization (OMRP), and 3) pathways to the hydride CCT intermediate was conducted with a simplified system with R2=H. This study suggests that CCT could occur by direct hydrogen‐atom transfer without any activation barrier. Further analysis of more realistic models with R2=p‐C6H4F or p‐C6H4NMe2 suggests that the electronic effect of the aryl para substituents significantly alters the ATRP activation barrier. Conversely, the hydrogen‐atom‐transfer barrier is essentially unaffected. Thus, the greater ATRP catalytic activity of the p‐NMe2 system makes the background CCT process less significant. The DFT study also compares the [FeCl2(R1N?C(R2)?C(R2)?NR1)] systems with a diaminobis(phenolato) derivative for which the CCT process shows even greater accessibility but has less incidence because of faster ATRP chain growth and interplay with a more efficient OMRP trapping. The difference between the two systems is attributed to destabilization of the FeII catalyst by the geometric constraints of the tetradentate diaminobis(phenolato) ligand. 相似文献
330.
Katrina Campbell Sara E. McNamee Anne-Catherine Huet Philippe Delahaut Natalia Vilarino Luis M. Botana Mark Poli Christopher T. Elliott 《Analytical and bioanalytical chemistry》2014,406(27):6867-6881
Despite ethical and technical concerns, the in vivo method, or more commonly referred to mouse bioassay (MBA), is employed globally as a reference method for phycotoxin analysis in shellfish. This is particularly the case for paralytic shellfish poisoning (PSP) and emerging toxin monitoring. A high-performance liquid chromatography method (HPLC-FLD) has been developed for PSP toxin analysis, but due to difficulties and limitations in the method, this procedure has not been fully implemented as a replacement. Detection of the diarrhetic shellfish poisoning (DSP) toxins has moved towards LC-mass spectrometry (MS) analysis, whereas the analysis of the amnesic shellfish poisoning (ASP) toxin domoic acid is performed by HPLC. Although alternative methods of detection to the MBA have been described, each procedure is specific for a particular toxin and its analogues, with each group of toxins requiring separate analysis utilising different extraction procedures and analytical equipment. In addition, consideration towards the detection of unregulated and emerging toxins on the replacement of the MBA must be given. The ideal scenario for the monitoring of phycotoxins in shellfish and seafood would be to evolve to multiple toxin detection on a single bioanalytical sensing platform, i.e. ‘an artificial mouse’. Immunologically based techniques and in particular surface plasmon resonance technology have been shown as a highly promising bioanalytical tool offering rapid, real-time detection requiring minimal quantities of toxin standards. A Biacore Q and a prototype multiplex SPR biosensor have been evaluated for their ability to be fit for purpose for the simultaneous detection of key regulated phycotoxin groups and the emerging toxin palytoxin. Deemed more applicable due to the separate flow channels, the prototype performance for domoic acid, okadaic acid, saxitoxin, and palytoxin calibration curves in shellfish achieved detection limits (IC20) of 4,000, 36, 144 and 46 μg/kg of mussel, respectively. A one-step extraction procedure demonstrated recoveries greater than 80 % for all toxins. For validation of the method at the 95 % confidence limit, the decision limits (CCα) determined from an extracted matrix curve were calculated to be 450, 36 and 24 μg/kg, and the detection capability (CCβ) as a screening method is ≤10 mg/kg, ≤160 μg/kg and ≤400 μg/kg for domoic acid, okadaic acid and saxitoxin, respectively. 相似文献