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排序方式: 共有104条查询结果,搜索用时 187 毫秒
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The rate coefficients for the reactions of C2H and C2D with O2 have been measured in the temperature range 295 K T 700 K. Both reactions show a slightly negative temperature dependence in this temperature range, with kC2H+O2 = (3.15 ± 0.04) × 10−11 (T/295 K)−(0.16 ± 0.02) cm3 molecule−1 s−1. The kinetic isotope effect is kC2H/kC2D = 1.04 ± 0.03 and is constant with temperature to within experimental error. The temperature dependence and the C2H + O2 kinetic isotope effect are consistent with a capture-limited metathesis reaction, and suggest that formation of the initial HCCOO adduct is rate-limiting. 相似文献
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硅基材料是新一代高容量锂离子蓄电池负极材料的典型代表,近年来已成为理论研究和应用研究的热点.本文介绍了锂离子电池硅基负极材料的制备方法、电化学性能及其研究现状,分析了硅材料作为锂离子电池负极材料存在的问题;讨论了硅材料作为锂离子电池负极材料的研究前景.并指出若能克服目前存在问题,将有望成为新一代锂离子电池负极材料. 相似文献
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N. Hansen G. Kukkadapu B. Chen S. Dong H.J. Curran C.A. Taatjes A.J. Eskola D.L. Osborn L. Sheps W.J. Pitz K. Moshammer A.W. Jasper W. Chen J. Yang Z. Wang 《Proceedings of the Combustion Institute》2021,38(1):299-307
We studied the oxidation of neo-pentane by combining experiments, theoretical calculations, and mechanistic developments to elucidate the impact of the 3rd O2 addition reaction network on ignition delay time predictions. The experiments are based on photoionization mass spectrometry in jet-stirred and time-resolved flow reactors allowing for sensitive detection of the keto-hydroperoxide (KHP) and keto-dihydroperoxide (KDHP) intermediates. With neo-pentane exhibiting a unique symmetric molecular structure, which consequently results only in single KHP and KDHP isomers, theoretical calculations of ionization and fragment appearance energies and of absolute photoionization cross sections enabled the unambiguous identification and quantification of the KHP intermediate. Its temperature and time-resolved profiles together with calculated and experimentally observed KHP-to-KDHP signal ratios were compared to simulation results based on a newly developed mechanism that describes the 3rd O2 addition reaction network. A satisfactory agreement has been observed between the experimental data points and the simulation results, thus adding confidence to the model's overall performance. Finally, this mechanism was used to predict ignition delay times reported previously in shock tube and rapid compression machine experiments (J. Bugler et al., Combust. Flame 163 (2016) 138–156). While the model accurately reproduces the experimental data, simulations with and without the 3rd O2 addition reaction network included reveal only a negligible effect on the predicted ignition delay times at 10 and 20 atm. According to model calculations, low temperatures and high pressures promote the importance of the 3rd O2 addition reactions. 相似文献
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Liondas CA; Chrissoulidis DP 《The Quarterly Journal of Mechanics and Applied Mathematics》2007,60(3):275-287
This paper is intended to clarify a misunderstanding concerningthe source singularity of the electric Green's tensor for aperfectly conducting semi-infinite cone of circular cross-section.Tai's series expansion of the Green's tensor is known to lacka singular term at the source region. Jones has reconstructedthe solution to this problem and has pointed out the differencebetween his result and that of Tai. The aim of our paper isto demonstrate that, although Jones's closed-form solution iscorrect, there is a mistake in his comparison with Tai's seriessolution. We conclude that one of the two additional singularterms that Jones claims as missing from Tai's formula must beomitted. Besides, we compare Jones's closed-form solution withSmyshlyaev's solution to the very same problem. We concludethat the magnetic field expressions given by Jones and Smyshlyaevcoincide, but a singular term is missing from Smyshlyaev's expressionfor the electric field. 相似文献
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Goodman TNT; Micchelli CA; Rodriguez G; Seatzu S 《IMA Journal of Numerical Analysis》1998,18(3):331-354
It is shown that, under certain conditions, orthonormalizingthe positive integer shifts of an exponentially decaying functionon the half line by the Gram-Schmidt process leads to a limitingprofile given by orthonormalizing all their integer shifts onthe whole line. These results derive from properties of Choleskyfactorization of bi-infinite and semi-infinite matrices. Anexample is provided by the negative exponential function andconjectures are given, supported by numerical evidence, forthe Gaussian and Lorentz function. 相似文献
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Goulay F Soorkia S Meloni G Osborn DL Taatjes CA Leone SR 《Physical chemistry chemical physics : PCCP》2011,13(46):20820-20827
The reaction of ethynyl radical (C(2)H) with allene (C(3)H(4)) at room temperature is investigated using an improved synchrotron multiplexed photoionization mass spectrometer (MPIMS) coupled to tunable vacuum ultraviolet (VUV) synchrotron radiation from the Advanced Light Source at the Lawrence Berkeley National Laboratory (LBNL). The orthogonal-accelerated time-of-flight mass spectrometer (OA-TOF) compared to the magnetic sector mass spectrometer used in a previous investigation of the title reaction (Phys. Chem. Chem. Phys., 2007, 9, 4291) enables more sensitive and selective detection of low-yield isomeric products. The C(5)H(4) isomer with the lowest ionization energy, pentatetraene, is now identified as a product of the reaction. Pentatetraene is predicted to be formed based on recent ab initio/RRKM calculations (Phys. Chem. Chem. Phys., 2010, 12, 2606) on the C(5)H(5) potential energy surface. However, the computed branching fraction for pentatetraene is predicted to be five times higher than that for methyldiacetylene, whereas experimentally the branching fraction of pentatetraene is observed to be small compared to that of methyldiacetylene. Although H-atom assisted isomerization of the products can affect isomer distribution measurements, isomerization has a negligible effect in this case. The kinetic behavior of the several C(5)H(4) isomers is identical, as obtained by time-dependent photoionization spectra. Even for high allene concentrations (and hence higher H-atom concentrations) no decay of the pentatetraene fraction is observed, indicating that H-assisted isomerization of pentatetraene to methyldiacetylene does not account for the difference between the experimental data and the theoretical branching ratios. 相似文献
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从烟草(品种革新一号)单倍体花粉植株的叶和茎产生的愈伤组织,结合悬浮培养,获得的细胞分离出原生质体。在液体培养基中静置培养,12小时后原生质体开始变为卵圆形,细胞壁明显可见,24小时后完成第一次细胞分裂。以后继续分裂形成浅黄色的愈伤组织,在培养四星期后可达1毫米大小,再放到转床上进行旋转培养18天左右,愈伤组织可达3—4毫米大小。当转移到分化培养基后,分别分化出苗及根,长成完整的植株。 原生质体再生细胞的分裂与分化,不仅受不同器官来源的愈伤组织及其年龄的影响;还受分化培养基的基本成份及所用细胞分裂素的类型等的影响。 相似文献