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排序方式: 共有135条查询结果,搜索用时 11 毫秒
91.
Zhu LY Peng JC Reimer PE Awes TC Brooks ML Brown CN Bush JD Carey TA Chang TH Cooper WE Gagliardi CA Garvey GT Geesaman DF Hawker EA He XC Isenhower LD Kaplan DM Kaufman SB Klinksiek SA Koetke DD Lee DM Lee WM Leitch MJ Makins N McGaughey PL Moss JM Mueller BA Nord PM Papavassiliou V Park BK Petitt G Sadler ME Sondheim WE Stankus PW Thompson TN Towell RS Tribble RE Vasiliev MA Webb JC Willis JL Wise DK Young GR;FNAL E/NuSea Collaboration 《Physical review letters》2007,99(8):082301
We report a measurement of the angular distributions of Drell-Yan dimuons produced using an 800 GeV/c proton beam on a deuterium target. The muon angular distributions in the dilepton rest frame have been measured over the kinematic range 4.5相似文献
92.
Megan E. Leitch Elizabeth Casman Gregory V. Lowry 《Journal of nanoparticle research》2012,14(12):1-23
Many international groups study environmental health and safety (EHS) concerns surrounding the use of engineered nanomaterials (ENMs). These researchers frequently use the ??Project on Emerging Nanotechnologies?? (PEN) inventory of nano-enabled consumer products to prioritize types of ENMs to study because estimates of life-cycle ENM releases to the environment can be extrapolated from the database. An alternative ??snapshot?? of nanomaterials likely to enter commerce can be determined from the patent literature. The goal of this research was to provide an overview of nanotechnology intellectual property trends, complementary to the PEN consumer product database, to help identify potentially ??risky?? nanomaterials for study by the nano-EHS community. Ten?years of nanotechnology patents were examined to determine the types of nano-functional materials being patented, the chemical compositions of the ENMs, and the products in which they are likely to appear. Patenting trends indicated different distributions of nano-enabled products and materials compared to the PEN database. Recent nanotechnology patenting is dominated by electrical and information technology applications rather than the hygienic and anti-fouling applications shown by PEN. There is an increasing emphasis on patenting of nano-scale layers, coatings, and other surface modifications rather than traditional nanoparticles, and there is widespread use of nano-functional semiconductor, ceramic, magnetic, and biological materials that are currently less studied by EHS professionals. These commonly patented products and the nano-functional materials they contain may warrant life-cycle evaluations to determine the potential for environmental exposure and toxicity. The patent and consumer product lists contribute different and complementary insights into the emerging nanotechnology industry and its potential for introducing nanomaterials into the environment. 相似文献
93.
A broad mechanistic investigation regarding hydroamination reactions catalyzed by a tethered bis(ureate) zirconium species, [ureate(2-)]Zr(NMe(2))(2)(HNMe(2)), is described. The cyclization of both primary and secondary aminoalkene substrates gives similar kinetic profiles, with zero-order dependence on substrate concentration up to ~60-75% conversion, followed by first-order dependence for the remainder of the reaction. The addition of 2-methylpiperidine changes the observed substrate dependence to first order throughout the reaction, but does not act as a competitive inhibitor. The reactions are first order in precatalyst up to loadings of ~0.15 M, indicating that a well-defined, mononuclear catalytic species is operative. Several model complexes have been structurally characterized, including dimeric imido and amido species, and evaluated for catalytic performance. These results indicate that imido species need not be invoked as catalytically relevant intermediates, and that the mono(amido) complex [ureate(2-)]Zr(NMe(2))(Cl)(HNMe(2)) is much less active than its bis(amido) counterpart. Structural evidence suggests that this is due to differences in coordination geometry between the mono- and bis(amido) complexes, and that an equatorial amido ligand is required for efficient catalytic turnover. On the basis of the determination of kinetic isotope effects and stoichiometric reactivity, the catalytic turnover-limiting step is proposed to be a concerted C-H, C-N bond-forming process with a highly ordered, unimolecular transition state (ΔS(?) = -21 ± 1 eu). In addition to this key bond-forming step, the catalytic cycle involves an on-cycle pre-equilibrium between six- and seven-coordinate intermediates, leading to the observed switch from zero- to first-order kinetics. 相似文献
94.
Leitch AA Lekin K Winter SM Downie LE Tsuruda H Tse JS Mito M Desgreniers S Dube PA Zhang S Liu Q Jin C Ohishi Y Oakley RT 《Journal of the American Chemical Society》2011,133(15):6051-6060
The bromo-substituted bisdiselenazolyl radical 4b (R(1) = Et, R(2) = Br) is isostructural with the corresponding chloro-derivative 4a (R(1) = Et, R(2) = Cl), both belonging to the tetragonal space group P(4)2(1)m and consisting of slipped π-stack arrays of undimerized radicals. Variable temperature, ambient pressure conductivity measurements indicate a similar room temperature conductivity near 10(-4) S cm(-1) for the two compounds, but 4b displays a slightly higher thermal activation energy E(act) (0.23 eV) than 4a (0.19 eV). Like 4a, radical 4b behaves as a bulk ferromagnet with an ordering temperature of T(C) = 17.5 K. The coercive field H(c) (at 2 K) of 1600 Oe for 4b is, however, significantly greater than that observed for 4a (1370 Oe). High pressure (0-15 GPa) structural studies on both compounds have shown that compression reduces the degree of slippage of the π-stacks, which gives rise to changes in the magnetic and conductive properties of the radicals. Relatively mild loadings (<2 GPa) cause an increase in T(C) for both compounds, that of 4b reaching a maximum value of 24 K; further compression to 5 GPa leads to a decrease in T(C) and loss of magnetization. Variable temperature and pressure conductivity measurements indicate a decrease in E(act) with increasing pressure, with eventual conversion of both compounds from a Mott insulating state to one displaying weakly metallic behavior in the region of 7 GPa (for 4a) and 9 GPa (for 4b). 相似文献
95.
Chang TH Beddo ME Brown CN Carey TA Cooper WE Gagliardi CA Garvey GT Geesaman DF Hawker EA He XC Isenhower LD Kaplan DM Kaufman SB Koetke DD McGaughey PL Lee WM Leitch MJ Moss JM Mueller BA Papavassiliou V Peng JC Reimer PE Sadler ME Sondheim WE Stankus PW Towell RS Tribble RE Vasiliev MA Webb JC Willis JL Young GR;FNAL E/NuSea Collaboration 《Physical review letters》2003,91(21):211801
We present measurements of the polarization of the J/psi produced in 800-GeV proton interactions with a copper target. Polarization of the J/psi is sensitive to the ccmacr; production and hadronization processes. A longitudinal polarization is observed at large x(F), while at small x(F) the state is produced essentially unpolarized or slightly transversely polarized. No significant variation of the polarization is observed versus p(T). 相似文献
96.
Beer L Haddon RC Itkis ME Leitch AA Oakley RT Reed RW Richardson JF VanderVeer DG 《Chemical communications (Cambridge, England)》2005,(9):1218-1220
The resonance stabilized bis-thiadiazinyl framework holds potential as a stable and versatile building block for the design of radical-based conductors and magnetic materials. 相似文献
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