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941.
Catalytic Amine Oxidation under Ambient Aerobic Conditions: Mimicry of Monoamine Oxidase B 下载免费PDF全文
Alexander T. Murray Myles J. H. Dowley Dr. Fabienne Pradaux‐Caggiano Dr. Amgalanbaatar Baldansuren Dr. Alistair J. Fielding Dr. Floriana Tuna Christopher H. Hendon Prof. Aron Walsh Prof. Guy C. Lloyd‐Jones Dr. Matthew P. John Dr. David R. Carbery 《Angewandte Chemie (International ed. in English)》2015,54(31):8997-9000
The flavoenzyme monoamine oxidase (MAO) regulates mammalian behavioral patterns by modulating neurotransmitters such as adrenaline and serotonin. The mechanistic basis which underpins this enzyme is far from agreed upon. Reported herein is that the combination of a synthetic flavin and alloxan generates a catalyst system which facilitates biomimetic amine oxidation. Mechanistic and electron paramagnetic (EPR) spectroscopic data supports the conclusion that the reaction proceeds through a radical manifold. This data provides the first example of a biorelevant synthetic model for monoamine oxidase B activity. 相似文献
942.
Our aim is to construct new examples of totally ordered and ∗-ordered noncommutative integral domains. We will discuss the
following classes of rings: enveloping algebras U(L), group rings
G and smash products U(L)
G. All of them are examples of Hopf algebras. Characterizations of orderability for enveloping algebras and group rings and
of ∗-orderability for enveloping algebras have been found before and will be recalled in the article. Our main results are:
for and L finite–dimensional, we characterize the orderability of U(L)
G; for , we give a necessary and a sufficient condition for ∗-orderability of
G (G orderable, respectively, G residually ‘torsion-free nilpotent’). Moreover, for and L finite-dimensional, we reduce the problem of characterizing the ∗-orderability of U(L)
G to the problem of characterizing the ∗-orderability of
G. The latter remains open.
The research of the first author was supported by the Ministry of Education, Science and Sport of the Republic of Slovenia
under grant P1-0222 (Algebraic methods in operator theory). The research of the second and third author was supported by the
Natural Sciences and Engineering Research Council of Canada. 相似文献
943.
By utilizing superelastic electron scattering from laser-excited atoms within a new magnetic angle changing device, the differential cross sections for excitation of atoms by electron impact over the complete scattering geometry are determined for the first time. In the experiments described here, these techniques are combined to reveal the angular momentum transferred to calcium atoms during electron excitation to the 4(1) P(1) state, from near 0 degrees to beyond 180 degrees . The experiments are discussed, and results presented for energies of 45 and 55 eV. These results are compared to calculations using a distorted wave Born approximation. 相似文献
944.
Arsene I Bearden IG Beavis D Bekele S Besliu C Budick B Bøggild H Chasman C Christensen CH Dalsgaard HH Debbe R Gaardhøje JJ Hagel K Ito H Jipa A Johnson EB Jørgensen CE Karabowicz R Katrynska N Kim EJ Larsen TM Lee JH Lindal S Løvhøiden G Majka Z Murray M Natowitz J Nielsen BS Nygaard C Płaneta R Rami F Renault F Ristea C Ristea O Röhrich D Samset BH Sanders SJ Scheetz RA Staszel P Tveter TS Videbaek F Wada R Yin Z Yang H Zgura IS 《Physical review letters》2007,98(25):252001
We present particle spectra for charged hadrons pi(+/-), K(+/-), p, and p[over] from pp collisions at square root[s] = 200 GeV measured for the first time at forward rapidities (2.95 and 3.3). The kinematics of these measurements are skewed in a way that probes the small momentum fraction in one of the protons and large fractions in the other. Large proton to pion ratios are observed at values of transverse momentum that extend up to 4 GeV/c, where protons have momenta up to 35 GeV. Next-to-leading order perturbative QCD calculations describe the production of pions and kaons well at these rapidities, but fail to account for the large proton yields and small p[over]/p ratios. 相似文献
945.
Sakai K Smith EG Webber GB Baker M Wanless EJ Bütün V Armes SP Biggs S 《Journal of colloid and interface science》2007,314(2):381-388
The desorption and subsequent pH-responsive behavior of selectively quaternized poly(2-(dimethylamino)ethyl methacrylate)-block-poly(2-(diethylamino)ethyl methacrylate) (PDMA-PDEA) films at the silica/aqueous solution interface has been characterized. The copolymer films were prepared at pH 9, where micelle-like surface aggregates are spontaneously formed on silica. The subsequent rinse with a copolymer-free electrolyte solution adjusted to pH 9 causes partial desorption of the weakly or non-quaternized copolymers, but negligible desorption for the highly quaternized copolymers. Further rinsing with a pH 4 electrolyte solution results in additional desorption and extension (swelling) of the remaining adsorbed copolymer film normal to the interface. This pH-responsive behavior is reversible for two pH cycles (9-4-9-4) as monitored by both quartz crystal microbalance with dissipation monitoring (QCM-D) and also zeta potential measurements. The magnitude of the pH-responsive behavior depends on the mean degree of quaternization of the PDMA block. Moreover, a combination of contact angle data, zeta potential measurements and in situ atomic force microscopy (AFM) studies indicates that the pH-responsive behavior is influenced not only by the number of cationic binding sites on the adsorbed copolymer chains but also by the adsorbed layer structure. 相似文献
946.
The nitrone above is readily available via the intramolecular aza Diels-Alder reaction of an amino acid derived triene in acetic acid. Subsequent treatment of the nitrone in refluxing toluene with substituted actetylenes produced the pictured pyrrole. At lower temperatures a 2,3-dihydroisoxazole, which is the product of a 3+2 dipolar cycloaddition, is produced. Upon heating in refluxing toluene the 2,3-dihydroisoxazole is converted to the pyrrole. 相似文献
947.
A novel and efficient synthesis of (−)-8-epi-swainsonine 2 is reported. Stereocontrolled diol formation from the bicyclic alkene 3 followed by a stereoselective vinylation of the aldehyde and ring closing metathesis gave the indolizidine ring system, which was converted into (−)-8-epi-swainsonine 2. 相似文献
948.
Characterization of the arene-oxidizing intermediate in ToMOH as a diiron(III) species 总被引:2,自引:0,他引:2
Murray LJ Naik SG Ortillo DO García-Serres R Lee JK Huynh BH Lippard SJ 《Journal of the American Chemical Society》2007,129(46):14500-14510
We report the generation and characterization of a diiron(III) intermediate formed during reaction with dioxygen of the reduced hydroxylase component of toluene/o-xylene monooxygenase from Pseudomonas sp. OX1. The decay rate of this species is accelerated upon mixing with phenol, a substrate for this system. Under steady-state conditions, hydrogen peroxide was generated in the absence of substrate. The oxidized hydroxylase also decomposed hydrogen peroxide to liberate dioxygen in the absence of reducing equivalents. This activity suggests that dioxygen activation may be reversible. The linear free energy relationship determined from hydroxylation of para-substituted phenols under steady-state turnover has a negative slope. A value of rho < 0 is consistent with electrophilic attack by the oxidizing intermediate on the aromatic substrates. The results from these steady and pre-steady-state experiments provide compelling evidence that the diiron(III) intermediate is the active oxidant in the toluene/o-xylene monooxygenase system and is a peroxodiiron(III) transient, despite differences between its optical and M?ssbauer spectroscopic parameters and those of other peroxodiiron(III) centers. 相似文献
949.
Field JS Haines RJ Ledwaba LP McGuire R Munro OQ Low MR McMillin DR 《Dalton transactions (Cambridge, England : 2003)》2007,(2):192-199
The synthesis and characterization of [Pt{4'-(R)trpy}(CN)]X (R = Ph, X = BF(4) or SbF(6); R = o-CH(3)C(6)H(4), X = SbF(6); R = o-ClC(6)H(4), X = SbF(6); or R = o-CF(3)C(6)H(4), X = SbF(6)) are described where trpy = 2,2':6',2'-terpyridine. Single crystals of [Pt{4'-(Ph)trpy}(CN)]BF(4).CH(3)CN were grown by vapour diffusion of diethyl ether into an acetonitrile solution of [Pt{4'-(Ph)trpy}(CN)]BF(4). An X-ray crystal structure determination of the solvated complex confirms the near linear coordination of the cyanide ligand to the platinum centre. The cation is almost planar as evidenced by a twist of only 1.9 degrees of the phenyl group out of the plane of the terpyridyl moiety. Cyclic voltammograms were recorded in DMF/0.1 M TBAH for the [Pt{4'-(R)trpy}(CN)](+) cations. Two quasi-reversible one-electron reduction (cathodic) waves are observed with E(1/2) values that show the trend expected for an increasingly lower energy of the trpy-based LUMO of the complex i.e., [Pt{4'-(Ph)trpy}(CN)](+) approximately [Pt{4'-(o-CH(3)C(6)H(4))trpy}(CN)](+) < [Pt{4'-(o-ClC(6)H(4))trpy}(CN)](+) < [Pt{4'-(o-CF(3)C(6)H(4))trpy}(CN)](+). All the [Pt(4'-(R)trpy}(CN)](+) cations are photoluminescent in dichloromethane. Emission by [Pt{4'-(Ph)trpy}(CN)](+) is from an excited state with largely (3)MLCT orbital parentage, but with some intraligand (3)pi-pi* character mixed-in (tau = 0.1 micros). In contrast, the other three cations display emission that appears exclusively intraligand (3)pi-pi* in origin (tau approximately 0.8 micros). Emission spectra have been recorded in a low concentration frozen DME {1 : 5 : 5 (v/v) DMF-MeOH-EtOH} glass. For the R = o-CH(3)C(6)H(4), o-ClC(6)H(4) and o-CF(3)C(6)H(4) cations the envelope of vibronic structure and energies of the vibrational components are essentially the same as that recorded in dichloromethane. However, for the [Pt{4'-(Ph)trpy}(CN)](+) cation, there is a blue-shift in the energies of the vibrational components as compared to that recorded in dichloromethane, as well as a change in the envelope of vibronic structure to a more "domed" pattern; this has been interpreted in terms of a higher percentage of intraligand (3)pi-pi* character in the emitting state for the glass. Increasing the concentration of the glass invariably leads to aggregation of the cations and the consequent development of new low energy bands, such that at 0.200 mM broad peaks centred at ca. 650 and 700 nm dominate the spectrum; these bands are assigned to excimeric (3)pi-pi* and (3)MMLCT emission, respectively. 相似文献
950.
Weekes SM Ogrin FY Murray WA Keatley PS 《Langmuir : the ACS journal of surfaces and colloids》2007,23(3):1057-1060
We have extended the widely used technique of nanosphere lithography to produce nanosphere templates with significantly improved long-range order. Single, ordered domains stretching over areas greater than 1 cm2 have been achieved by assembling spheres with the correct surface chemistry on a water/air interface. Self-assembly over macroscopic areas is facilitated by a combination of electrostatic and capillary forces. The presented technique is easily implemented, and the assembled monolayers can be transferred onto almost any surface, thus making the procedure applicable to a broad range of nanoscale research. We demonstrate this through the fabrication of hexagonally ordered, macroscopic arrays of magnetic nanostructures with modified magnetic properties. 相似文献