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71.
Paolo Matteini Giovanni Agati Patrizia Pinelli Andrea Goti 《Monatshefte für Chemie / Chemical Monthly》2011,45(2):885-893
Abstract
The interaction of the model flavonoid glycoside rutin with the flavonoid reagent diphenylborinic acid 2-aminoethyl ester (DPBA) was investigated using a combination of HPLC–DAD–ESI–MS analysis, UV–visible spectroscopy, and semiempirical calculations. Mass spectra and spectroscopic data made it possible to describe the complexation pathway as addition of diphenylboron groups to the two available 3′,4′-o-diphenolic and the 5-hydroxy-4-keto coordinating sites of rutin. Semiempirical calculations were carried out to obtain the conformation of the most stable DPBA/rutin adducts. The results showed that a number of complexation dynamics can occur as a function of the characteristics of the medium (type and pH of the solvent) and of the amount of DPBA. This work suggests the possibility of substantially improving existing procedures for recognition of flavonoid compounds by choice of suitable experimental conditions. 相似文献72.
Patrizia Trovalusci Danilo Capecchi Giuseppe Ruta 《Archive of Applied Mechanics (Ingenieur Archiv)》2009,79(11):981-997
This paper presents an overview of the origin of multiscale approaches in mechanics. While the pioneer molecular models of
linear elastic bodies by Navier, Cauchy and Poisson were contradicted by experiments, the phenomenological energetic approach
by Green still seems suitable for simple materials only. Voigt’s molecular model, here reinterpreted in the light of contemporary
mechanics, reconciled the two approaches providing a conceptual guideline for developing constitutive models based on a direct
link between continuum and discrete solid mechanics. Such a theoretical background proves to be especially suitable for new
complex materials. An example referred to masonry-like materials is given. 相似文献
73.
74.
Borghetti P Goldoni A Castellarin-Cudia C Casalis L Herberg F Floreano L Cossaro A Verdini A Gebauer R Ghosh P Sangaletti L 《Langmuir : the ACS journal of surfaces and colloids》2010,26(24):19007-19013
The role of potassium in the formation of synthetic eumelanin aggregates is investigated by atomic force microscopy and soft-X-ray spectroscopy. Control over the thin film granularity is achieved by using K salts, in both drop casting and electrodeposition of eumelanin thin films. Further control over orientation is made possible by a suitable choice of the substrate: evidence of self-assembly is found for thin films deposited on gold. Finally, it is shown that the potassium content affects not only the samples morphology, but also the low-lying states in the valence band, where a transfer of spectral weight across the HOMO-LUMO gap is observed, disclosing possible applications of this multifunctional biomacromolecule. 相似文献
75.
Francesca Tessore Dr. Elena Cariati Prof. Franco Cariati Prof. Dominique Roberto Prof. Renato Ugo Prof. Patrizia Mussini Prof. Cristiano Zuccaccia Dr. Alceo Macchioni Prof. 《Chemphyschem》2010,11(2):495-507
A series of 4‐X‐1‐methylpyridinium cationic nonlinear optical (NLO) chromophores (X=(E)‐CH?CHC6H5; (E)‐CH?CHC6H4‐4′‐C(CH3)3; (E)‐CH?CHC6H4‐4′‐N(CH3)2; (E)‐CH?CHC6H4‐4′‐N(C4H9)2; (E,E)‐(CH?CH)2C6H4‐4′‐N(CH3)2) with various organic (CF3SO3?, p‐CH3C6H4SO3?), inorganic (I?, ClO4?, SCN?, [Hg2I6]2?) and organometallic (cis‐[Ir(CO)2I2]?) counter anions are studied with the aim of investigating the role of ion pairing and of ionic dissociation or aggregation of ion pairs in controlling their second‐order NLO response in anhydrous chloroform solution. The combined use of electronic absorption spectra, conductimetric measurements and pulsed field gradient spin echo (PGSE) NMR experiments show that the second‐order NLO response, investigated by the electric‐field‐induced second harmonic generation (EFISH) technique, of the salts of the cationic NLO chromophores strongly depends upon the nature of the counter anion and concentration. The ion pairs are the major species at concentration around 10?3 M , and their dipole moments were determined. Generally, below 5×10?4 M , ion pairs start to dissociate into ions with parallel increase of the second‐order NLO response, due to the increased concentration of purely cationic NLO chromophores with improved NLO response. At concentration higher than 10?3 M , some multipolar aggregates, probably of H type, are formed, with parallel slight decrease of the second‐order NLO response. Ion pairing is dependent upon the nature of the counter anion and on the electronic structure of the cationic NLO chromophore. It is very strong for the thiocyanate anion in particular and, albeit to a lesser extent, for the sulfonated anions. The latter show increased tendency to self‐aggregate. 相似文献
76.
Amol Date Patrizia Pasini Sylvia Daunert 《Analytical and bioanalytical chemistry》2010,398(1):349-356
Bacterial whole-cell biosensing systems provide important information about the bioavailable amount of target analytes. They
are characterized by high sensitivity and specificity/selectivity along with rapid response times and amenability to miniaturization
as well as high-throughput analysis. Accordingly, they have been employed in various environmental and clinical applications.
The use of spore-based sensing systems offers the unique advantage of long-term preservation of the sensing cells by taking
advantage of the environmental resistance and ruggedness of bacterial spores. In this work, we have incorporated spore-based
whole-cell sensing systems into centrifugal compact disk (CD) microfluidic platforms in order to develop a portable sensing
system, which should enable the use of these hardy sensors for fast on-field analysis of compounds of interest. For that,
we have employed two spore-based sensing systems for the detection of arsenite and zinc, respectively, and evaluated their
analytical performance in the miniaturized microfluidic format. Furthermore, we have tested environmental and clinical samples
on the CD microfluidic platforms using the spore-based sensors. Germination of spores and quantitative response to the analyte
could be obtained in 2.5–3 h, depending on the sensing system, with detection limits of 1 × 10−7 M for arsenite and 1 × 10−6 M for zinc in both serum and fresh water samples. Incorporation of spore-based whole-cell biosensing systems on microfluidic
platforms enabled the rapid and sensitive detection of the analytes and is expected to facilitate the on-site use of such
sensing systems. 相似文献
77.
Pugliesi I Krok P Lochbrunner S Błaszczyk A von Hänisch C Mayor M Riedle E 《The journal of physical chemistry. A》2010,114(48):12555-12560
The ultrafast fluorescence quenching of 2,6-sulfanyl-core-substituted naphthalenediimides was investigated by transient spectroscopy. We find a strong dependence of the relaxation on the chemical structure of the substituent. Direct linking of an aryl rest to the sulfur atom leads to a strong red shift of the fluorescence in 1 ps and the disappearance of the emission in 5-7 ps depending on the polarity and viscosity of the solvent. This complex behavior is interpreted with the help of quantum chemical calculations. The calculations suggest that the initial relaxation corresponds to a planarization of the substituents and an associated partial electron transfer. This is followed by a twisting of the phenylsulfanyl substituents out of the molecular plane that allows a complete localization of the electron-donating orbital on the aryl group. Finally the back transfer happens in another 5-7 ps. For an additional methylene spacer group between the sulfur and the aryl, this sequence of relaxation steps is not possible and a simple exponential decay, slower by about 1 order of magnitude, is found. 相似文献
78.
79.
M. Assunta Girasolo Patrizia Portanova Giuseppe Ruisi 《Journal of organometallic chemistry》2010,695(4):609-3579
Novel diorganotin(IV) derivatives of l-Arginine (HArg), Nα-(tert-Butoxycarbonyl)-l-Arginine (Boc-Arg-OH) and l-Ala-l-Arg (H2Ala-Arg), H2NC(NH)NH(CH2)3CH(NHR′)CO2H, where R′ = H in HArg, R′ = C(O)OC(CH3)3 in Boc-Arg-OH, R′ = H2NCH(CH3)CO in H2Ala-Arg and triorganotin(IV) derivatives of Boc-Arg-OH have been synthesized and structurally characterized. The complexes were investigated by FT-IR and 119Sn Mössbauer in the solid state and by 1H, 13C, 119Sn and 1H-1H COSY NMR spectroscopy, in solution. The spectroscopic characterization leading to the proposed molecular structures was accomplished on the basis of these experiments. l-Arginine appears to behave as a chelating ligand through carboxylate and -NH2 groups in Me2Sn(Arg)2, while in Nα-t-Boc-l-Arginine complex, the Nα-protected amino group being exempted from coordination, only the carboxylate groups are effectors of bonding to the organometallic moieties. FT-IR spectra give a clear indication that guanidino groups in all the complexes are not involved in coordination, since ν(CN-H) frequency of the terminal guanidino group is fairly constant and unshifted relative to the free ligand. The biological activity of organotin(IV)-complexes was also investigated by use of human HT29 colorectal carcinoma cells. The cytotoxic activity of the compounds was determined by the MTT quantitative colorimetric assay, capable of detecting viable cells in comparison with that exerted by cisplatin. A marked cytotoxic activity for nearly all complexes, is evident being higher than that exerted by cisplatin, while no significant improvement of activity was observed for Me2Sn(Arg)2 and Me2Sn(Ala-Arg), which was confirmed by IC50 values. Then, we assessed whether the cytotoxicity induced by organotin(IV) complexes was associated with the induction of apoptosis. Light microscopy analysis, performed to study the morphological changes induced in HT29 cells, confirmed the results obtained with MTT test. No significant morphological alterations were observed in HT29 cells after treatment with Me2Sn(Ala-Arg) and Me2Sn(l-Arg)2. Cells treated with nBu2Sn(Boc-Arg)2, nBu2Sn(Ala-Arg), nBu3Sn(Boc-Arg) and Me3Sn(Boc-Arg), appeared rounded, isolated and detached from culture substrate, indicating the commitment to apoptotic cell death. 相似文献
80.
Mahelet Aweke Tadesse Carlo Galli Patrizia Gentili 《Journal of Physical Organic Chemistry》2011,24(7):529-538
The aminoxyl radical 6‐trifluoromethyl‐benzotriazol‐N‐oxyl (TFNO) has been generated from the parent hydroxylamine 6‐CF3‐1‐hydroxy‐benzotriazole (TFBT) by one‐electron oxidation with a CeIV salt and characterized by spectrophotometry and cyclic voltammetry (CV). Rate constants of H‐abstraction (kH) by TFNO from a number of H‐donor benzylic substrates have been determined spectrophotometrically in MeCN solution at 25 °C. A radical H‐atom transfer (HAT) route of oxidation is substantiated for TFNO by several pieces of evidence. The kinetic data also testify the relevance of stereoelectronic effects upon the HAT reactivity of TFNO. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献