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311.
312.
A C Dean E Bradford A W Hubbard W D Pocklington J Thomson 《Journal of chromatography. A》1969,44(3):465-471
313.
HBr and HCl react with Pt(111) and Pt(100) surfaces to form adsorbed layers consisting of specific mixtures of halogen atoms and hydrogen halide molecules. Exposure of Pt(111) to HBr yielded a (3×3) LEED pattern beginning at and persisting at the maximum coverage which consisted of plus . The most probable structure at maximum coverage, Pt(111)[c(3 × 3)]-(3 Br + HBr), nas a rhombic unit cell encompassing nine surface Pt atoms, and containing three Br atoms and one HBr molecule. On Pt(100) the structure at maximum coverage appears to be Pt(100)[c(2√2 × √2)]R45°-(Br + HBr), ; the rectangular unit cell involves four Pt atoms, one Br atom and one HBr molecule. Each of these structures consists of an hexagonal array of adsorbed atoms or molecules, excepting slight distortion for best fit with the substrate in the case of Pt(100). Treatment of Pt(100) with HCl produced a diffuse Pt(100)(2 × 2)-(Cl + HCl) structure at the maximum coverage of ΘCl = 0.13, ΘHCl = 0.11. Exposure of Pt(111) to HCl produced a disordered overlayer. Thermal desorption, Auger spectroscopy and mass spectroscopy provided coverage data. Thermal desorption data reveal prominent rate maxima associated with the structural transitions observed by LEED. Br and HBr, Cl and HCl were the predominant thermal desorption products. 相似文献
314.
Arthur T. Hubbard Roy M. Ishikawa James Katekaru 《Journal of Electroanalytical Chemistry》1978,86(2):271-288
Low-energy electron diffraction patterns were obtained for Pt(100), Pt(111) and polycrystalline electrodes before and after exposure to aqueous 1 M H2SO4. Linear potential scan voltammograms were recorded. The results demonstrate that one of the principal peaks in the hydrogen region of the current-potential curves of polycrystalline Pt is assignable to Pt(100) and the other to Pt(111). The maximum amount of chemisorbed hydrogen corresponds to one hydrogen atom per surface Pt atom. The Pt(100)[1×1], Pt(111) and polycrystalline surfaces appear to withstand prolonged voltammetric characterization at potentials between ?0.2 and 1.2 V vs. a calomel reference. Variation of the voltammetric characteristics of hydrogen chemisorption with changes in the nature of the supporting electrolyte anion are described. 相似文献
315.
Rice JE Hughes JW Diamond PH Kosuga Y Podpaly YA Reinke ML Greenwald MJ Gürcan ÖD Hahm TS Hubbard AE Marmar ES McDevitt CJ Whyte DG 《Physical review letters》2011,106(21):215001
Intrinsic rotation has been observed in I-mode plasmas from the C-Mod tokamak, and is found to be similar to that in H mode, both in its edge origin and in the scaling with global pressure. Since both plasmas have similar edge ?T, but completely different edge ?n, it may be concluded that the drive of the intrinsic rotation is the edge ?T rather than ?P. Evidence suggests that the connection between gradients and rotation is the residual stress, and a scaling for the rotation from conversion of free energy to macroscopic flow is calculated. 相似文献
316.
Abstract Humic substances are the major organic constituents of soils and sediments. They also occur in small concentrations in natural surface waters and groundwaters. They form through the breakdown of plant and animal tissues by chemical and biological processes that tend to produce complex chemical structures that are more stable than the original material from which they were derived. One of the more important characteristics of humic substances is their ability to form water-soluble and water-insoluble complexes with metal ions and hydrous oxides and to interact with clay minerals and various organic compounds such as alkanes, fatty acids, and toxic organic substances such as pesticides. 相似文献
317.
Pollack SJ Beyer KS Lock C Müller I Sheppard D Lipkin M Hardick D Blurton P Leonard PM Hubbard PA Todd D Richardson CM Ahrens T Baader M Hafenbradl DO Hilyard K Bürli RW 《Journal of computer-aided molecular design》2011,25(7):677-687
The stress-activated kinase p38α was used to evaluate a fragment-based drug discovery approach using the BioFocus fragment library. Compounds were screened by surface plasmon resonance (SPR) on a Biacore(?) T100 against p38α and two selectivity targets. A sub-set of our library was the focus of detailed follow-up analyses that included hit confirmation, affinity determination on 24 confirmed, selective hits and competition assays of these hits with respect to a known ATP binding site inhibitor. In addition, functional activity against p38α was assessed in a biochemical assay using a mobility shift platform (LC3000, Caliper LifeSciences). A selection of fragments was also evaluated using fluorescence lifetime (FLEXYTE(?)) and microscale thermophoresis (Nanotemper) technologies. A good correlation between the data for the different assays was found. Crystal structures were solved for four of the small molecules complexed to p38α. Interestingly, as determined both by X-ray analysis and SPR competition experiments, three of the complexes involved the fragment at the ATP binding site, while the fourth compound bound in a distal site that may offer potential as a novel drug target site. A first round of optimization around the remotely bound fragment has led to the identification of a series of triazole-containing compounds. This approach could form the basis for developing novel and active p38α inhibitors. More broadly, it illustrates the power of combining a range of biophysical and biochemical techniques to the discovery of fragments that facilitate the development of novel modulators of kinase and other drug targets. 相似文献
318.
Jose Castro-Perez Thomas P. Roddy Nico M. M. Nibbering Vinit Shah David G. McLaren Stephen Previs Athula B. Attygalle Kithsiri Herath Zhu Chen Sheng-Ping Wang Lyndon Mitnaul Brian K. Hubbard Rob J. Vreeken Douglas G. Johns Thomas Hankemeier 《Journal of the American Society for Mass Spectrometry》2011,22(9):1568-1569
319.
Närväinen J Hubbard PL Kauppinen RA Morris GA 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2010,207(2):242-250
Magnetization transfer (MT) MRI and Z-spectroscopy are tools to study both water-macromolecule interactions and pH-sensitive exchange dynamics between water and the protons of mobile chemical groups within these macromolecules. Both rely on saturation of frequencies offset from water and observation of the on-resonance water signal. In this work, an RF saturation method called Z-spectroscopy with Alternating-Phase Irradiation (ZAPI) is introduced. Based on the T(2)-selectivity of the irradiation pulse, ZAPI can be used to separate the different contributions to a Z-spectrum, as well as to study the T(2) distribution of the macromolecules contributing to the MT signal. ZAPI can be run at resonance for water and with low power, thus minimizing problems with specific absorption rate (SAR) limits in clinical applications. In this paper, physical and practical aspects of ZAPI are discussed and the sequence is applied in vitro to sample systems and in vivo to rat head to demonstrate the method. 相似文献
320.
A mathematical model describing the coupling of electrical,optical and thermal effects in semiconductor lasers is introduced.Numerical and asymptotic solutions are derived, including expressionsfor key physical quantities such as the initial time delay,the frequency of spike oscillation and the temperature rise,together with its influence on the photon density, the electronconcentration and the threshold current. The consequences ofthermal effects in reducing efficiency are thus quantified. 相似文献