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81.
Yuan Z Entwistle CD Collings JC Albesa-Jové D Batsanov AS Howard JA Taylor NJ Kaiser HM Kaufmann DE Poon SY Wong WY Jardin C Fathallah S Boucekkine A Halet JF Marder TB 《Chemistry (Weinheim an der Bergstrasse, Germany)》2006,12(10):2758-2771
The (p-R-phenyl)dimesitylboranes (R=Me(2)N, MeO, MeS, Br, I), (p-R-phenylethynyl)dimesitylboranes (R=Me(2)N, MeO, MeS, H), (E)-[2-(p-R-phenyl)ethenyl]dimesitylboranes (R=Me(2)N, H(2)N, MeO, MeS, H, CN, NO(2)), (E)-[2-(2-thienyl)ethenyl]dimesitylborane, and (E)-[2-(o-carboranyl)ethenyl]dimesitylborane have been prepared through the reaction of the appropriate p-R-phenyl- and p-R-phenylethynyllithium reagents with dimesitylboron fluoride and by hydroboration of the appropriate p-R-phenylacetylene, 2-ethynylthiophene, and o-ethynylcarborane with dimesitylborane. Their UV/Vis absorption and emission spectra have been recorded in a range of solvents with the fluorescence maxima of the donor-substituted compounds in particular exhibiting large bathochromic shifts in highly polar solvents, indicative of charge transfer leading to large dipole moments in the excited state. The molecular structures of the (p-R-phenyl)dimesitylboranes (R=Me(2)N, MeO, MeS, Br, I), the (E)-[2-(p-R-phenyl)ethenyl]dimesitylboranes (R=Me(2)N, H(2)N MeO, MeS, H), (p-R-phenylethynyl)dimesitylborane (R=Me(2)N), and (E)-[2-(2-thienyl)ethenyl]dimesitylborane, which have been determined from single-crystal X-ray diffraction measurements, offer evidence of increased conjugation in the ground state with increased donor strength of the R substituent. Their first- and second-order molecular hyperpolarizabilities have been obtained from EFISH and THG measurements, the first-order hyperpolarizabilities being largest for the strongest R-substituent donors. AM1 calculations have been performed on these compounds, showing reasonable agreement with the experimentally obtained bond lengths and hyperpolarizabilities, as well as on several related hypothetical compounds containing multiple C==C bonds, most of which are proposed to have even larger hyperpolarizabilities. 相似文献
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Tkaczyk S Tollefson K Tollestrup A Toyoda H Trischuk W de Troconiz JF Tseng J Turini N Ukegawa F Valls J Vejcik S Velev G Vidal R Vilar R Volobouev I Vucinic D Wagner RG Wagner RL Wahl J Wallace NB Walsh AM Wang C Wang CH Wang MJ Watanabe T Waters D 《Physical review letters》2000,84(23):5273-5278
We have searched for direct production of scalar top quarks at the Collider Detector at Fermilab in 88 pb(-1) of p&pmacr; collisions at sqrt[s] = 1.8 TeV. We assume the scalar top quark decays into either a bottom quark and a chargino or a bottom quark, a lepton, and a scalar neutrino. The event signature for both decay scenarios is a lepton, missing transverse energy, and at least two b-quark jets. For a chargino mass of 90 GeV/c(2) and scalar neutrino masses of at least 40 GeV/c(2), we find no evidence for scalar top production and present upper limits on the production cross section in both decay scenarios. 相似文献
83.
Jardin C Oeckler O Mattausch H Simon A Halet JF Saillard JY Bauer J 《Inorganic chemistry》2000,39(26):5895-5900
The synthesis by arc-melting techniques, the single-crystal X-ray structure, and the theoretical analysis of Gd4B3C4 are reported. It crystallizes in the triclinic space group P1 with a = 3.637(2) A, b = 3.674(2) A, c = 11.859(5) A, alpha = 93.34(5) degrees, beta = 96.77(5) degrees, gamma = 90.24(5) degrees, and Z = 1. In this structure, the boron and carbon atoms form two different types of nonmetal arrangements: 1-D (BC)infinity branched chains and finite (0-D) linear CBC "molecular" units. Gd4B3C4 is the first characterized member of the rare earth metal borocarbide series in which both 1-D and "molecular" 0-D nonmetal atom systems coexist. From the structural and theoretical analysis, the following formal charge distribution can be proposed within the ionic limit: (Gd3+)4(BC2(5-)(BC3-)2.e-. Tight-binding calculations suggest that the excess electron in the ionic limit is mainly localized on the Gd atoms (at the bottom of the 5d band), while LAPW calculations favor its localization on the (BC)infinity chain. The bonding within this compound is fully analyzed and compared to other members of the rare earth metal borocarbide series. 相似文献
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Nabila Suad Lokbani-Azzouz Abdou Boucekkine Jean-François Halet Jean-Yves Saillard 《Journal of Cluster Science》2003,14(1):49-60
DFT calculations have been carried out on a series of isoelectronic M4E2(CO)12 (M=Os, Ru, Fe; E=Bi, As, P, N, CH, SiH) clusters which exhibit an octahedral M4E2 core. For these clusters two different octahedral topologies are possible, one in which the E atoms are bonded together and one in which they occupy opposite vertices. Calculations show that the energy difference between both skeletal isomers is dominated by the strength of the E–E bonding and that it tends to decrease significantly when M is a 4d or 5d metal. These results are discussed in the light of the arrangement of the avalaible experimental structures and in particular of those of Ru4Bi2(CO)12 and Os4Bi2(CO)12. 相似文献
87.
Ferro-Luzzi M Bouwhuis M Passchier E Zhou Z Alarcon R Anghinolfi M van Bommel R Botto T van den Brand JF Buchholz M Bulten HJ Choi S Comfort J Dolfini S Ent R Gaulard C Higinbotham D de Jager CW van Klaveren EP Konstantinov E Lang J de Lange DJ Miller MA Nikolenko D Nooren GJ Papadakis N Passchier I Poolman HR Popov SG Rachek I Ripani M Six E Steijger JJ Taiuti M Unal O Vodanis N de Vries H 《Physical review letters》1996,77(13):2630-2633
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Dr. Goutam Kumar Kole Marta Košćak Dr. Anissa Amar Dr. Dragomira Majhen Dr. Ksenija Božinović Dr. Zlatko Brkljaca Dr. Matthias Ferger Dr. Evripidis Michail Sabine Lorenzen Dr. Alexandra Friedrich Dr. Ivo Krummenacher Michael Moos Prof. Dr. Holger Braunschweig Prof. Dr. Abdou Boucekkine Prof. Dr. Christoph Lambert Prof. Dr. Jean-François Halet Prof. Dr. Ivo Piantanida Prof. Dr. Klaus Müller-Buschbaum Prof. Dr. Todd B. Marder 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(40):e202200753
A series of bis-(4’-pyridylethynyl)arenes (arene=benzene, tetrafluorobenzene, and anthracene) were synthesized and their bis-N-methylpyridinium compounds were investigated as a class of π-extended methyl viologens. Their structures were determined by single crystal X-ray diffraction, and their photophysical and electrochemical properties (cyclic voltammetry), as well as their interactions with DNA/RNA were investigated. The dications showed bathochromic shifts in emission compared to the neutral compounds. The neutral compounds showed very small Stokes shifts, which are a little larger for the dications. All of the compounds showed very short fluorescence lifetimes (<4 ns). The neutral compound with an anthracene core has a quantum yield of almost unity. With stronger acceptors, the analogous bis-N-methylpyridinium compound showed a larger two-photon absorption cross-section than its neutral precursor. All of the dicationic compounds interact with DNA/RNA; while the compounds with benzene and tetrafluorobenzene cores bind in the grooves, the one with an anthracene core intercalates as a consequence of its large, condensed aromatic linker moiety, and it aggregates within the polynucleotide when in excess over DNA/RNA. Moreover, all cationic compounds showed highly specific CD spectra upon binding to ds-DNA/RNA, attributed to the rare case of forcing the planar, achiral molecule into a chiral rotamer, and negligible toxicity toward human cell lines at ≤10 μM concentrations. The anthracene-analogue exhibited intracellular accumulation within lysosomes, preventing its interaction with cellular DNA/RNA. However, cytotoxicity was evident at 1 μM concentration upon exposure to light, due to singlet oxygen generation within cells. These multi-faceted features, in combination with its two-photon absorption properties, suggest it to be a promising lead compound for development of novel light-activated theranostic agents. 相似文献