全文获取类型
收费全文 | 189篇 |
免费 | 6篇 |
专业分类
化学 | 127篇 |
晶体学 | 1篇 |
力学 | 2篇 |
综合类 | 1篇 |
数学 | 16篇 |
物理学 | 48篇 |
出版年
2021年 | 4篇 |
2020年 | 6篇 |
2018年 | 3篇 |
2016年 | 6篇 |
2015年 | 7篇 |
2013年 | 8篇 |
2012年 | 8篇 |
2011年 | 5篇 |
2010年 | 6篇 |
2009年 | 4篇 |
2008年 | 10篇 |
2007年 | 5篇 |
2006年 | 2篇 |
2005年 | 7篇 |
2004年 | 3篇 |
2003年 | 5篇 |
2002年 | 5篇 |
1999年 | 2篇 |
1997年 | 3篇 |
1994年 | 5篇 |
1992年 | 2篇 |
1988年 | 2篇 |
1986年 | 2篇 |
1985年 | 6篇 |
1984年 | 3篇 |
1983年 | 3篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1978年 | 3篇 |
1977年 | 2篇 |
1976年 | 7篇 |
1975年 | 2篇 |
1974年 | 2篇 |
1973年 | 5篇 |
1955年 | 2篇 |
1928年 | 2篇 |
1913年 | 2篇 |
1912年 | 2篇 |
1910年 | 2篇 |
1909年 | 3篇 |
1908年 | 3篇 |
1905年 | 2篇 |
1897年 | 3篇 |
1888年 | 3篇 |
1887年 | 1篇 |
1885年 | 1篇 |
1884年 | 1篇 |
1880年 | 2篇 |
排序方式: 共有195条查询结果,搜索用时 749 毫秒
71.
The energy barriers to conformational inversion of a number of bridged biphenyls have been measured by the NMR method and the effects of different bridging groups examined. 相似文献
72.
E.H. FinkD.A. Ramsay 《Journal of Molecular Spectroscopy》2002,216(2):322-334
The near-infrared emission spectrum of the Atilde;2A′→X?2A″ transition of DO2 has been studied by Fourier-transform spectrometry. The 000→000 band has been recorded at high spectral resolution. ΔKa=±1 subbands up to Ka′=12→Ka″=11 and Ka′=9→Ka″=10, comprising lines from rotational levels up to N′=34, have been observed. With about a factor of 5-10 lower intensity, ΔKa=0 subbands 0-0 to 6-6 were found, which are due to magnetic dipole transitions. Several local perturbations extending over 3-10 N″ values were observed. Two prominent perturbations in the F1 levels of the Ã2A′, 000, Ka″=11 and 12 states are attributed to ΔKa=0, ΔJ=0, ΔN=±1 interactions with the 211 level of the X?2A″ ground state. The rotational constants for HO2 and DO2 have been used to deduce the molecular geometry of HO2 at the zero point levels of the X?2A″ and Ã2A′ states. 相似文献
73.
Takayoshi Kasakado Mamoru Hyodo Akihiro Furuta Aina Kamardine Ilhyong Ryu Takahide Fukuyama 《中国化学会会志》2020,67(12):2253-2257
In this communication flow Friedel–Crafts alkylation was studied using hydroxy-substituted sulfonic acid-functionalized silica as a catalyst and 1-adamantanol as a model substrate. The reaction of 1-adamantanol ( 1a ) with toluene ( 2a ) proceeded well with 5 min of residence time at 120°C to give good yield of 1-tolyladamantane ( 3a ) as a 1:9 mixture of meta and para isomers. When the flow synthesis was carried out over 2.5 hr of running time, the collected five fractions contain the product 3a in 97–92% yields, suggesting the durability of the catalyst. 相似文献
74.
Z. Kamal J.S.C. McKee W.D. Ramsay M.S.A.L. Al-Ghazi J. Birchall J.J.G. Durocher N. Videla 《Physics letters. A》1980,75(6):475-477
Kβ/KαX-ray intensity ratios have been measured for various elements between Z = 29 and Z = 79 for incident proton energies of 23.6, 32.1 and 43.6 MeV. The results yield no evidence for a variation in ratio with particle energy. 相似文献
75.
Morales W Cason M Aina O de Tacconi NR Rajeshwar K 《Journal of the American Chemical Society》2008,130(20):6318-6319
The energy payback time associated with the semiconductor active material is an important parameter in a photovoltaic solar cell device. Thus lowering the energy requirements for the semiconductor synthesis step or making it more energy-efficient is critical toward making the overall device economics more competitive relative to other nonpolluting energy options. In this communication, combustion synthesis is demonstrated to be a versatile and energy-efficient method for preparing inorganic oxide semiconductors such as tungsten trioxide (WO3) for photovoltaic or photocatalytic solar energy conversion. The energy efficiency of combustion synthesis accrues from the fact that high process temperatures are self-sustained by the exothermicity of the combustion process, and the only external thermal energy input needed is for dehydration of the fuel/oxidizer precursor mixture and bringing it to ignition. Importantly, we show that, in this approach, it is also possible to tune the optical characteristics of the oxide semiconductor (i.e., shift its response toward the visible range of the electromagnetic spectrum) in situ by doping the host semiconductor during the formative stage itself. As a bonus, the resultant material shows enhanced surface properties such as markedly improved organic dye uptake relative to benchmark samples obtained from commercial sources. Finally, this synthesis approach requires only very simple equipment, a feature that it shares with other "mild" inorganic semiconductor synthesis routes such as sol-gel chemistry, chemical bath deposition, and electrodeposition. The present study constitutes the first use of combustion synthesis for preparing WO3 powder comprising nanosized particles. 相似文献
76.
Eibl G Bernardo K Koal T Ramsay SL Weinberger KM Graber A 《Rapid communications in mass spectrometry : RCM》2008,22(14):2248-2252
Isotope correction of a profile is an important step in the analysis of mass spectrometry derived data. The problem is mathematically formulated as a system of linear equations which is general enough to include previous correction methods. For the solution of these equations when applied to the whole profile an efficient algorithm is developed. In experimental tests the resulting algorithm corrected the profile fast and successfully. 相似文献
77.
Turner EH Dickerson JA Ramsay LM Swearingen KE Wojcik R Dovichi NJ 《Journal of chromatography. A》2008,1194(2):253-256
The spectroscopic and electrophoretic properties of proteins labeled with Chromeo P503 were investigated. Its photobleaching characteristics were determined by continually infusing Chromeo P503-labeled alpha-lactalbumin into a sheath-flow cuvette and monitored fluorescence as a function of laser power. The labeled protein is relatively photo-labile with an optimum excitation power of about 2 mW. The unreacted reagent is weakly fluorescent but present at much higher concentration than the labeled protein. The unreacted reagent undergoes photobleaching at a laser power more than an order of magnitude higher than the labeled protein. One-dimensional capillary electrophoresis analysis of Chromeo P503-labeled alpha-lactalbumin produced concentration detection limits (3sigma) of 12 pM and mass detection limits of 0.7 zmol, but with modest theoretical plate counts of 17,000. The reagent was employed for the two-dimensional capillary electrophoresis analysis of a homogenate prepared from a Barrett's esophagus cell line; the separation quality is similar to that produced by 3-(2-furoyl)quinoline-2-carboxaldehyde (FQ), a more commonly used reagent. 相似文献
78.
K. Matsuta Y. Masuda K. Hatanaka S. C. Jeong S. Kawasaki R. Matsumiya M. Mihara Y. Watanabe D. Nishimura Y. Morita K. Asahi T. Adachi J. Martin A. Konaka A. Miller C. Bidinosti T. Dawson L. Lee C. Davis D. Ramsay W. van Oers E. Korkmaz L. Buchman 《Hyperfine Interactions》2013,219(1-3):89-93
Polarized UCNs have been created by selecting only one spin state passing through a magnetized Fe foil. Typical degree of polarization was about 90 %. The polarization relaxation time in the prototype Ramsey cell was $T_1 =1100^{+800}_{-400}(Nd,Pr)-(Tb,Dy,Gd)-(Fe,Co,Al,Cu)-B magnets were heat treated in two different ways and investigated in the temperature range 4.2 to 400 K. After optimal heat treatment intrinsic coercive field i H c?= 1640 and 5040 kA/m for room temperature and 10 K was obtained and the temperature coefficient of remanence α?=??0.01 for temperature range 80 to 375 K was found. On basis of magnetic measurements and 57Fe Mössbauer spectroscopy, the possible reasons for the increase of i H c during multi-step heat treatment are discussed. 相似文献
79.
80.
Ramsay AJ Godden TM Boyle SJ Gauger EM Nazir A Lovett BW Fox AM Skolnick MS 《Physical review letters》2010,105(17):177402
We study optically driven Rabi rotations of a quantum dot exciton transition between 5 and 50 K, and for pulse areas of up to 14π. In a high driving field regime, the decay of the Rabi rotations is nonmonotonic, and the period decreases with pulse area and increases with temperature. By comparing the experiments to a weak-coupling model of the exciton-phonon interaction, we demonstrate that the observed renormalization of the Rabi frequency is induced by fluctuations in the bath of longitudinal acoustic phonons, an effect that is a phonon analogy of the Lamb shift. 相似文献