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991.
Rajam S Murthy RS Jadhav AV Li Q Keller C Carra C Pace TC Bohne C Ault BS Gudmundsdottir AD 《The Journal of organic chemistry》2011,76(24):9934-9945
The photoreactivity of (3-methyl-2H-azirin-2-yl)-phenylmethanone, 1, is wavelength-dependent (Singh et al. J. Am. Chem. Soc. 1972, 94, 1199-1206). Irradiation at short wavelengths yields 2P, whereas longer wavelengths produce 3P. Laser flash photolysis of 1 in acetonitrile using a 355 nm laser forms its triplet ketone (T(1K), broad absorption with λ(max) ~ 390-410 nm, τ ~ 90 ns), which cleaves and yields triplet vinylnitrene 3 (broad absorption with λ(max) ~ 380-400 nm, τ = 2 μs). Calculations (B3LYP/6-31+G(d)) reveal that T(1K) of 1 is located 67 kcal/mol above its ground state (S(0)) and has a long C-N bond (1.58 ?), and the calculated transition state to form 3 is only 1 kcal/mol higher in energy than T(1K) of 1. The calculations show that 3 has significant 1,3-carbon iminyl biradical character, which explains why 3 reacts efficiently with oxygen and decays by intersystem crossing to the singlet surface. Photolysis of 1 in argon matrixes at 14 K produced ketene imine 7, which presumably is formed from 3 intersystem crossing to 7. In comparison, photolysis of 1 in methanol with a 266 nm laser produces mainly ylide 2 (λ(max) ~ 380 nm, τ ~ 6 μs, acetonitrile), which decays to form 2P. Ylide 2 is formed via singlet reactivity of 1, and calculations show that the first singlet excited state of the azirine chromophore (S(1A)) is located 113 kcal/mol above its S(0) and that the singlet excited state of the ketone (S(1K)) is 85 kcal/mol. Furthermore, the transition state for cleaving the C-C bond in 1 to form 2 is located 49 kcal/mol above the S(0) of 1. Thus, we theorize that internal conversion of S(1A) to a vibrationally hot S(0) of 1 forms 2, whereas intersystem crossing from S(1K) to T(1K) results in 3. 相似文献
992.
Bozzini B Gianoncelli A Kaulich B Kiskinova M Mele C Prasciolu M 《Physical chemistry chemical physics : PCCP》2011,13(17):7968-7974
This paper reports a pioneering application of soft X-ray scanning transmission microscopy (STXM), combined with micro-spot X-ray absorption spectroscopy (XAS) and X-ray fluorescence spectroscopy (XRF), for the investigation of the corrosion of metal electrodes in contact with room-temperature ionic liquids (RTIL). Using an open electrochemical cell in vacuo we explore some fundamental aspects of the aggressiveness of the 1-butyl-1-methyl-pyrrolidinium bis(trifluoromethylsulfonyl)amide ([BMP][TFSA]) RTIL towards Ni under in situ electrochemical polarisation. The possibility of imaging electrochemically-induced morphological features in conjunction with micro-XAS and XRF spectroscopies has provided unprecedented details regarding the space distribution and chemical state of corrosion products. 相似文献
993.
Wang L Meng H Shen PK Bianchini C Vizza F Wei Z 《Physical chemistry chemical physics : PCCP》2011,13(7):2667-2673
The adsorption and electrooxidation pathways of ethylene glycol (EG) on polycrystalline palladium surfaces have been investigated in both alkaline and acidic media by in situ FTIR spectroscopy in conjunction with cyclic voltammetry. Palladium exhibits a high electrocatalytic activity in alkaline solution with low onset oxidation potentials and high current densities, depending on the pH, as well as on the supporting electrolyte. Higher potentials are required for EG oxidation in acidic solutions, where the catalytic performance decreases with increasing the pH. The products and intermediates of EG oxidation on Pd are influenced by the pH. In alkaline media, both C(2) species (glycolate, glyoxal, glyoxylate and oxalate) and C(1) species (formate and carbonate) are formed in mutual concentrations depending on the pH. In contrast, CO(2) is selectively produced in acidic aqueous solution. 相似文献
994.
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
995.
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
996.
997.
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
998.
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
999.
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
1000.
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