全文获取类型
收费全文 | 150篇 |
免费 | 3篇 |
国内免费 | 2篇 |
专业分类
化学 | 87篇 |
晶体学 | 1篇 |
力学 | 1篇 |
数学 | 5篇 |
物理学 | 61篇 |
出版年
2023年 | 1篇 |
2022年 | 1篇 |
2020年 | 1篇 |
2019年 | 2篇 |
2018年 | 2篇 |
2017年 | 1篇 |
2016年 | 6篇 |
2014年 | 1篇 |
2013年 | 2篇 |
2012年 | 6篇 |
2011年 | 10篇 |
2010年 | 2篇 |
2009年 | 2篇 |
2008年 | 7篇 |
2007年 | 3篇 |
2006年 | 11篇 |
2005年 | 7篇 |
2004年 | 9篇 |
2003年 | 7篇 |
2002年 | 7篇 |
2001年 | 3篇 |
2000年 | 5篇 |
1999年 | 2篇 |
1998年 | 1篇 |
1997年 | 4篇 |
1996年 | 8篇 |
1995年 | 1篇 |
1994年 | 4篇 |
1993年 | 5篇 |
1992年 | 3篇 |
1991年 | 4篇 |
1990年 | 1篇 |
1989年 | 6篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1985年 | 1篇 |
1984年 | 4篇 |
1983年 | 1篇 |
1980年 | 1篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1977年 | 1篇 |
1975年 | 1篇 |
1974年 | 2篇 |
1970年 | 1篇 |
1962年 | 1篇 |
排序方式: 共有155条查询结果,搜索用时 15 毫秒
71.
Selective catalytic oxidation of ammonia to nitrogen on atomic oxygen precovered Au(111) 总被引:1,自引:0,他引:1
Gong J Ojifinni RA Kim TS White JM Mullins CB 《Journal of the American Chemical Society》2006,128(28):9012-9013
We demonstrate ammonia oxidation promoted by an atomic oxygen precovered Au(111) surface. The selectivity of the catalytic oxidation of ammonia to NO or N2 on Au(111) is tunable by the atomic oxygen coverage. We propose that N2 and NO are produced via the recombination reactions of Nad + Nad and Nad + Oad. 相似文献
72.
Methanol adsorption and reaction have been studied on Rh-deposited cerium oxide thin films under UHV conditions using temperature-programmed desorption and synchrotron soft X-ray photoelectron spectroscopy. The methanol behavior was examined as a function of the Ce oxidation state, methanol exposure, and Rh particle size and coverage. When Rh nanoparticles were deposited on the ceria films, methanol decomposed on Rh to CO and H below 200 K. H atoms recombined and desorbed between 200 and 300 K. CO evolved from Rh deposited on fully oxidized ceria between 400 and 500 K. However, on reduced ceria films, the CO on Rh further decomposed to atomic C. Methanol adsorbed on the ceria films deprotonated to form methoxy as the only intermediate on the surface. This methoxy decomposed and desorbed as CO and H2 at higher temperatures regardless of the ceria oxidation state. Compared with the methanol reaction on Rh-free ceria thin films, formaldehyde formation from methoxy was completely suppressed after Rh deposition. Our results indicate that Rh can promote the decomposition of methoxy adsorbed on the ceria and that decomposition of methoxy intermediates occurred at the metal/oxide interfaces. On the other hand, the reduced ceria can promote total methanol decomposition on Rh. 相似文献
73.
McClure SM Safarik DJ Truskett TM Mullins CB 《The journal of physical chemistry. B》2006,110(23):11033-11036
We have examined transport mechanisms in amorphous solid water (ASW) by studying thermal desorption of layered nanoscale films of CCl4 and labeled ASW. The interlayer mixing observed near T approximately 150-160 K is inconsistent with a mechanism involving diffusion through a dense phase. Instead, intermixing occurs via vapor-phase transport through an interconnected porous network created within the film during crystallization. As a consequence, the self-diffusivity of ASW is significantly smaller than previously thought, indicating that water undergoes either a glass transition or a fragile-to-strong transition at a temperature above 160 K. 相似文献
74.
Donna A. Chen Jay S. Ratliff Xiaofeng Hu Wesley O. Gordon Sanjaya D. Senanayake David R. Mullins 《Surface science》2010,604(5-6):574-587
The thermal decomposition of dimethyl methylphosphonate (DMMP) on crystalline ceria thin films grown on Ru(0 0 0 1) was studied by temperature programmed desorption (TPD), X-ray photoelectron spectroscopy (XPS) and infrared absorption reflection spectroscopy (IRAS). TPD experiments show that methanol and formaldehyde desorb as the two main products at 575 K, while water, formaldehyde and CO are produced above 800 K. IRAS studies demonstrate that DMMP adsorbs via the phosphoryl oxygen at 200 K, but the PO bond converts to a bridging OPO species at 300 K. DMMP decomposition initially occurs via POCH3 bond scission to form methyl methylphosphonate (MMP) and methyl phosphonate (MP) between 300 and 500 K; XPS and IRAS data are consistent with a methoxy intermediate on the surface at these temperatures. The more stable PCH3 bonds remain intact up to 700 K, and the only surface intermediate at higher temperatures is believed to be POx. Although the presence of POx decreases activity for DMMP decomposition, some activity on the ceria surface remains even after 7 cycles of adsorption and reaction. The ceria films become reduced by multiple DMMP adsorption-reaction cycles, with the Ce+4 content dropping to 30% after seven cycles. Investigations of DMMP reaction on reduced ceria surfaces show that CO and H2 are produced in addition to methanol and formaldehyde. Furthermore, DMMP decomposition activity on the reduced ceria films is almost completely inhibited after only 3 adsorption-reaction cycles. Similarities between DMMP and methanol chemistry on the ceria films suggest that methoxy is a key surface intermediate in both reactions. 相似文献
75.
N. J. Ncapayi S. M. Mullins M. Benatar E. Gueorgueiva J. J. Lawrie G. K. Mabala S. Mukherjee S. H. T. Murray K. P. Mutshena R. T. Newman J. F. Sharpey-Schafer F. D. Smit P. Vymers 《The European Physical Journal A - Hadrons and Nuclei》2005,23(2):265-269
Excited states in 175Yb, 176Yb and 177Yb were populated via the bombardment of a 176Yb target with a 750 MeV 136Xe beam. Gamma-ray decays from these states were measured with the AFRODITE multi-detector spectrometer. The rotational band
previously assigned to the ground state of 177Yb has been reassigned to the first-excited state of 175Yb. A new rotational band based on the ground state of 177Yb is presented, and the band based on the Kπ = 4- two-quasiparticle state in 176Yb has been identified. Also a candidate for the rotational band based on the Kπ = 8-, T1/2 = 11.4(3) s two-quasiparticle state in 176Yb has been found. Comparisons of gK values derived from in-band branching ratios are consistent with the ν9/2+[624] assignment to the ground state of 177Yb, the ν2{9/2+[624] ⊗ 1/2-[510]} assignment to the Kπ = 4- state and with the ν2{9/2+[624] ⊗ 7/2-[514]} assignment to the Kπ = 8- metastable excited state in 176Yb. 相似文献
76.
Minimization of Fragmentation and Aggregation by Laser Desorption Laser Ionization Mass Spectrometry
Qinghao Wu Andrew E. Pomerantz Oliver C. Mullins Richard N. Zare 《Journal of the American Society for Mass Spectrometry》2013,24(7):1116-1122
Measuring average quantities in complex mixtures can be challenging for mass spectrometry, as it requires ionization and detection with nearly equivalent cross-section for all components, minimal matrix effect, and suppressed signal from fragments and aggregates. Fragments and aggregates are particularly troublesome for complex mixtures, where they can be incorrectly assigned as parent ions. Here we study fragmentation and aggregation in six aromatic model compounds as well as petroleum asphaltenes (a naturally occurring complex mixture) using two laser-based ionization techniques: surface assisted laser desorption ionization (SALDI), in which a single laser desorbs and ionizes solid analytes; and laser ionization laser desorption mass spectrometry (L2MS), in which desorption and ionization are separated spatially and temporally with independent lasers. Model compounds studied include molecules commonly used as matrices in single laser ionization techniques such as matrix assisted laser desorption ionization (MALDI). We find significant fragmentation and aggregation in SALDI, such that individual fragment and aggregate peaks are typically more intense than the parent peak. These fragment and aggregate peaks are expected in MALDI experiments employing these compounds as matrices. On the other hand, we observe no aggregation and only minimal fragmentation in L2MS. These results highlight some advantages of L2MS for analysis of complex mixtures such as asphaltenes. Figure
? 相似文献
77.
The condensation between dienophiles and α,β-unsaturated hydrazone azadienes was previously reported to afford piperidines. During an attempt to adapt this reaction to the preparation of piperidine-based conformationally restricted analogs of glutamate, it was discovered that the electrophile, dimethyl oxoglutaconate (DOG) led to highly substituted dihydropyrans in 20-50% yield. The unexpected pyran product likely results from an initial 1,4-addition of the hydrazone to the oxoglutaconate followed by intramolecular cyclization of the resultant enolate oxygen to the α,β-unsaturated iminium ion. Further manipulations afford substituted tetrahydropyran 6-methamino-2,4-dicarboxylic acids. 相似文献
78.
A. Lopez-Martens T. Wiborg-Hagen K. Hauschild M.L. Chelnokov V.I. Chepigin D. Curien O. Dorvaux G. Drafta B. Gall A. Görgen M. Guttormsen A.V. Isaev I.N. Izosimov A.P. Kabachenko D.E. Katrasev T. Kutsarova A.N. Kuznetsov A.C. Larsen O.N. Malyshev A. Minkova S. Mullins H.T. Nyhus D. Pantelica J. Piot A.G. Popeko S. Saro N. Scintee S. Siem N.U.H. Syed E.A. Sokol A.I. Svirikhin A.V. Yeremin 《Nuclear Physics A》2011
New high-statistics data have been obtained on the decay properties of 253No and its daughters using the reaction 207Pb(48Ca, 2n)253No. This was made possible thanks to an improved transmission of fusion–evaporation residues through the VASSILISSA recoil separator and an increased efficiency of the GABRIELA detector setup. The decay schemes of 253No and 249Fm have been revisited. The known level scheme of 249Fm has been confirmed, including a new level at 669 keV excitation energy. The observation of L X-rays in coincidence with the α decay of 249Fm gives additional support to the ground-state configuration of 1/2+[631] instead of 5/2+[622] for 245Cf. In both 249Fm and 245Cf, the interpretation of the data has been checked by comparing experimental α-particle and γ-ray spectra with realistic simulations of the decay cascades and of the interaction of particles and photons in the detectors of GABRIELA. The population of a 0.7 ms isomeric state attributed to 253No is confirmed by an α-tagged calorimetric measurement and the corresponding γ and electron decay spectra are presented. Possible evidence for more than one isomer is given and a tentative partial decay scheme is discussed in the light of the available experimental data, systematics and theoretical expectations. 相似文献
79.
Several gentamicin bulk samples from different origins were investigated using an LC/MS method.LC equipped with ion trap MS with positive ionization was performed on a Capcell Pak C18(AQ) column with the mobile phase containing 50 mM trifluoroacetic(TFA) and methanol.Impurities present in batches of gentamicin bulk samples were elucidated and compared according to their fragmentation behavior.In total seventeen impurities present in samples,five impurities were not elucidated and two compounds were identifi... 相似文献
80.
F. Eimer F. Weise A. Merli S. Birkner F. Sauer L. W?ste A. Lindinger R. A?ano?lu C. P. Koch W. Salzmann T. Mullins S. G?tz R. Wester M. Weidemüller 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2009,54(3):711-714
We present spectrally resolved pump-probe experiments on the photoassociation of ultracold rubidium atoms with shaped ultrashort
laser pulses. The pump pulse causes a free-bound transition leading to a coherent transient signal of rubidium molecules in
the first excited state. In order to achieve a high frequency resolution the bandwidth of the pump pulse is reduced to a few
wavenumbers. The frequency dependence of the transient signal close to the D1 atomic resonance is investigated for characteristic
pump-probe delay times. The observed spectra, which show a pronounced dip for pump-probe coincidence, are interpreted using
quantum dynamical calculations. 相似文献