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排序方式: 共有125条查询结果,搜索用时 31 毫秒
91.
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
92.
Tether S Theriot D Thurman-Keup R Tipton P Tkaczyk S Tollefson K Tollestrup A Toyoda H Trischuk W de Troconiz JF Tseng J Turini N Ukegawa F Vaiciulis T Valls J Vejcik S Velev G Vidal R Vilar R Volobouev I Vucinic D Wagner RG Wagner RL Wahl J Wallace NB Walsh AM 《Physical review letters》2000,85(20):4215-4220
We report the first observation of dijet events with a double Pomeron exchange topology produced in &pmacr;p collisions at sqrt[s] = 1800 GeV. The events are characterized by a leading antiproton, two jets in the central pseudorapidity region, and a large rapidity gap on the outgoing proton side. We present results on jet kinematics and production rates, compare them with corresponding results from single diffractive and inclusive dijet production, and test factorization. 相似文献
93.
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
94.
Jianyu Wei Dr. Rémi Marchal Prof. Didier Astruc Prof. Jean-Yves Saillard Prof. Jean-François Halet Dr. Samia Kahlal 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(24):5508-5514
The electronic structure of the spherical Mackay icosahedral nanosized cluster Pd55(PiPr3)12(μ3-CO)20 is analyzed by using DFT calculations. Results reveal that it can be considered as a regular superatom with a “magic” electron count of 20, characterized by a 1S2 1P6 1D10 2S2 jellium configuration. Its open shell nature is associated with partial occupation of non-jellium, 4d-type, levels located on the interior of the Pd55 kernel. This shows that the superatom model can be used to rationalize the bonding and stability of spherical ligated group 10 clusters, despite their apparent 0-electron count. 相似文献
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Clauwaert KM Van Bocxlaer JF Major HJ Claereboudt JA Lambert WE Van den Eeckhout EM Van Peteghem CH De Leenheer AP 《Rapid communications in mass spectrometry : RCM》1999,13(14):1540-1545
This paper describes the investigation of the potential of a quadrupole orthogonal acceleration time-of-flight mass spectrometer (Q-TOF) equipped with an atmospheric pressure ionisation interface for quantitative measurements of small molecules separated by reversed phase liquid chromatography. To this end, the detection limits and linear dynamic range in particular were studied in an LC/MS/MS experiment using 3,4-methylenedioxymethamphetamine standards and 3,4-methylenedioxyethylamphetamine for internal standardisation. In a second phase, the experiment was repeated with real biological extracts (whole blood, serum, and vitreous humour). A calibration for 3,4-methylenedioxymethamphetamine and its metabolite 3,4-methylenedioxyamphetamine was prepared in each of these matrices again using 3,4-methylenedioxyethylamphetamine as internal standard. The resulting quantitative data were compared with those obtained by liquid chromatography with fluorescence detection for the same extracts. The Q-TOF results revealed excellent sensitivity and a linear dynamic range of nearly four decades (2-10 000 pg on-column, r(2) = 0.9998, 1/x weighting). Furthermore, all the calibration curves prepared in biological material were superimposable, LC/MS/MS and LC-fluorescence, and the quantitative results for actual samples compared very favourably. It was concluded that the Q-TOF achieves a linear dynamic range for quantitative LC/MS/MS work exceeding that of fluorescence detection and at much better absolute sensitivity. Copyright 1999 John Wiley & Sons, Ltd. 相似文献
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