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81.
Coherence of an entangled exciton-photon state 总被引:1,自引:0,他引:1
Hudson AJ Stevenson RM Bennett AJ Young RJ Nicoll CA Atkinson P Cooper K Ritchie DA Shields AJ 《Physical review letters》2007,99(26):266802
We study the effect of the exciton fine-structure splitting on the polarization entanglement of photon pairs produced by the biexciton cascade in a quantum dot. Entanglement persists despite separations between the intermediate energy levels of up to 4 microeV. Measurements show that entanglement of the photon pair is robust to the dephasing of the intermediate exciton state responsible for the first-order coherence time of either single photon. We present a theoretical framework incorporating the effects of spin scattering, background light, and dephasing. We distinguish between the first-order coherence time, and a parameter which we measure for the first time and define as the cross-coherence time. 相似文献
82.
George C. Shields 《International journal of quantum chemistry》2020,120(20):e26274
The molecular education and research consortium in undergraduate computational chemistry (MERCURY) consortium, established in 2000, has contributed greatly to the scientific development of faculty and undergraduates. The MERCURY faculty peer-reviewed publication rate from 2001 to 2019 of 1.7 papers/faculty/year is 3.4 times the rate of the physical science faculty at primarily undergraduate institutions. We have worked with over 1000 students on research projects since 2001, and 75% of our undergraduate research students have been under-represented in chemistry, either female or students of color. Approximately half of our alumni attend graduate school for the purpose of obtaining advanced degrees in STEM fields, and two-thirds are female and/or students of color. We have had more than 1600 attendees at 18 MERCURY conferences, including 111 invited speakers, 61 of whom have been female and/or faculty of color. In this paper, the research accomplishments, transformational outcomes, and scientific productivity of the MERCURY faculty are highlighted. 相似文献
83.
84.
Thomas Rosenau Antje Potthast Karin Krainz Yuko Yoneda Thomas Dietz Zenaida Peralta-Inga Shields Alfred D. French 《Cellulose (London, England)》2011,18(6):1623-1633
In the present work, aged cotton linters have been analyzed for their chromophore content according to the CRI (“chromophore
release & identification”) method. Despite the very low contents in the ppb range, nine chromophores have been unambiguously
identified, which makes this account the first one on defined chromophoric structures isolated from cotton. A common feature
of the chromophores are 2-hydroxy-[1,4]benzoquinone, 2-hydroxyacetophenone and 5,8-dihydroxynaphthoquinone moieties, which
resemble chromophoric structures found in other cellulosic substrates, such as bleached pulps or fibers. The finding of these
compounds in lignin-free cotton linters confirms the previous hypothesis that those chromophores are formed from (oxidized)
carbohydrate structures rather than from lignin fragments. 相似文献
85.
Shields SJ Bluhm BK Russell DH 《Journal of the American Society for Mass Spectrometry》2000,11(7):626-638
[M + Cu]+ peptide ions formed by matrix-assisted laser desorption/ionization from direct desorption off a copper sample stage have sufficient internal energy to undergo metastable ion dissociation in a time-of-flight mass spectrometer. On the basis of fragmentation chemistry of peptides containing an N-terminal arginine, we propose the primary Cu+ ion binding site is the N-terminal arginine with Cu+ binding to the guanidine group of arginine and the N-terminal amine. The principal decay products of [M + Cu]+ peptide ions containing an N-terminal arginine are [a(n) + Cu - H]+ and [b(n) + Cu - H]+ fragments. We show evidence to suggest that [a(n) + Cu - H]+ fragment ions are formed by elimination of CO from [b(n) + Cu - H]+ ions and by direct backbone cleavage. We conclude that Cu+ ionizes the peptide by attaching to the N-terminal arginine residue; however, fragmentation occurs remote from the Cu+ ion attachment site involving metal ion promoted deprotonation to generate a new site of protonation. That is, the fragmentation reactions of [M + Cu]+ ions can be described in terms of a "mobile proton" model. Furthermore, proline residues that are adjacent to the N-terminal arginine do not inhibit formation of [b(n) + Cu - H]+ ion, whereas proline residues that are distant to the charge carrying arginine inhibit formation of [b(n) + Cu - H]+ ions. An unusual fragment ion, [c(n) + Cu + H]+, is also observed for peptides containing lysine, glutamine, or asparagine in close proximity to the Cu+ carrying N-terminal arginine. Mechanisms for formation of this fragment ion are also proposed. 相似文献
86.
Evans BA Fiser BL Prins WJ Rapp DJ Shields AR Glass DR Superfine R 《Journal of magnetism and magnetic materials》2012,324(4):501-507
Magnetic elastomers have been widely pursued for sensing and actuation applications. Silicone-based magnetic elastomers have a number of advantages over other materials such as hydrogels, but aggregation of magnetic nanoparticles within silicones is difficult to prevent. Aggregation inherently limits the minimum size of fabricated structures and leads to non-uniform response from structure to structure. We have developed a novel material that is a complex of a silicone polymer (polydimethylsiloxane-co-aminopropylmethylsiloxane) adsorbed onto the surface of magnetite (γ-Fe2O3) nanoparticles 7-10 nm in diameter. The material is homogenous at very small length scales (<100 nm) and can be crosslinked to form a flexible magnetic material, which is ideally suited for the fabrication of micro- to nanoscale magnetic actuators. The loading fraction of magnetic nanoparticles in the composite can be varied smoothly from 0 to 50 wt% without loss of homogeneity, providing a simple mechanism for tuning actuator response. We evaluate the material properties of the composite across a range of nanoparticle loading, and demonstrate a magnetic-field-induced increase in compressive modulus as high as 300%. Furthermore, we implement a strategy for predicting the optimal nanoparticle loading for magnetic actuation applications, and show that our predictions correlate well with experimental findings. 相似文献
87.
Stevenson RM Salter CL Nilsson J Bennett AJ Ward MB Farrer I Ritchie DA Shields AJ 《Physical review letters》2012,108(4):040503
A linear optical quantum computer relies on interference between photonic qubits for logic, and entanglement for near-deterministic operation. Here we measure the interference and entanglement properties of photons emitted by a quantum dot embedded within a light-emitting diode. We show that pairs of simultaneously generated photons are entangled, and indistinguishable from subsequently generated photons. We measure entanglement fidelity of 0.87 and two-photon-interference visibility of 0.60 ± 0.05. The visibility, limited by detector jitter, could be improved by optical cavity designs. 相似文献
88.
Abouzaid E Arenton M Barker AR Bellantoni L Bellavance A Blucher E Bock GJ Cheu E Coleman R Corcoran MD Corti G Cox B Erwin AR Escobar CO Glazov A Golossanov A Gomes RA Gouffon P Hanagaki K Hsiung YB Huang H Jensen DA Kessler R Kotera K Ledovskoy A McBride PL Monnier E Nelson KS Nguyen H Niclasen R Ping H Qi XR Ramberg EJ Ray RE Ronquest M Santos E Shields J Slater W Smith D Solomey N Swallow EC Toale PA Tschirhart R Velissaris C Wah YW Wang J White HB Whitmore J Wilking M Winstein B Winston R 《Physical review letters》2006,96(10):101801
Using the complete KTeV data set of 5,241 candidate K(L)--> pi(+) pi(-) e(+) e(-) decays (including an estimated background of 204 +/- 14 events), we have measured the coupling g(CR)= 0.163 +/- 0.0149(stat) +/- 0.023(syst) of the CP conserving charge radius process and from it determined a K(0) charge radius of = [-0.077 +/- 0.007(stat) +/- 0.011(syst)]fm(2). We have determined a first experimental upper limit of 0.04 (90% C.L.) /g(e1)/ / /g(M1)/ of the couplings for the E1 and M1 direct photon emission processes. We also report the measurement of /g(M1)/ including a vector form factor /g(M1)/(1 + (a(1)/a(2))/((M(2)(p)-(M(2)(k))= 2M(K)E(gamma*)), where vector /g(M1)/= 1.11+/- 0.12(stat) +/- 0.08(syst) and a(1)/a(2) = [-0.744 +/- 0.027(stat) +/- 0.032(syst)] GeV(2)/c(2). Finally, a CP-violating asymmetry of [13.6 +/- 1.4(stat) +/- 1.5(syst)]% in the CP and T odd angle phi between the decay planes of the e(+) e(-) and pi(+) pi(-) pairs in the K(L) center of mass is reported. 相似文献
89.
C. Simon M. Afzelius J. Appel A. Boyer de la Giroday S. J. Dewhurst N. Gisin C. Y. Hu F. Jelezko S. Kr?ll J. H. Müller J. Nunn E. S. Polzik J. G. Rarity H. De Riedmatten W. Rosenfeld A. J. Shields N. Sk?ld R. M. Stevenson R. Thew I. A. Walmsley M. C. Weber H. Weinfurter J. Wrachtrup R. J. Young 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2010,58(1):1-22
We perform a review of various approaches to the implementation of quantum memories, with an emphasis on activities within the quantum memory sub-project of the EU integrated project “Qubit Applications”. We begin with a brief overview over different applications for quantum memories and different types of quantum memories. We discuss the most important criteria for assessing quantum memory performance and the most important physical requirements. Then we review the different approaches represented in “Qubit Applications” in some detail. They include solid-state atomic ensembles, NV centers, quantum dots, single atoms, atomic gases and optical phonons in diamond. We compare the different approaches using the discussed criteria. 相似文献
90.