全文获取类型
收费全文 | 614篇 |
免费 | 24篇 |
专业分类
化学 | 460篇 |
晶体学 | 8篇 |
力学 | 13篇 |
数学 | 36篇 |
物理学 | 121篇 |
出版年
2023年 | 4篇 |
2021年 | 5篇 |
2020年 | 5篇 |
2019年 | 11篇 |
2018年 | 7篇 |
2016年 | 15篇 |
2015年 | 13篇 |
2014年 | 9篇 |
2013年 | 21篇 |
2012年 | 36篇 |
2011年 | 29篇 |
2010年 | 10篇 |
2009年 | 16篇 |
2008年 | 38篇 |
2007年 | 38篇 |
2006年 | 33篇 |
2005年 | 35篇 |
2004年 | 24篇 |
2003年 | 30篇 |
2002年 | 27篇 |
2001年 | 18篇 |
2000年 | 19篇 |
1999年 | 13篇 |
1998年 | 4篇 |
1997年 | 9篇 |
1996年 | 6篇 |
1995年 | 4篇 |
1994年 | 6篇 |
1993年 | 4篇 |
1990年 | 6篇 |
1989年 | 6篇 |
1988年 | 6篇 |
1987年 | 8篇 |
1985年 | 8篇 |
1984年 | 8篇 |
1983年 | 4篇 |
1982年 | 4篇 |
1981年 | 12篇 |
1980年 | 6篇 |
1979年 | 8篇 |
1978年 | 7篇 |
1977年 | 5篇 |
1976年 | 7篇 |
1975年 | 5篇 |
1974年 | 6篇 |
1973年 | 3篇 |
1972年 | 3篇 |
1969年 | 3篇 |
1968年 | 3篇 |
1936年 | 3篇 |
排序方式: 共有638条查询结果,搜索用时 15 毫秒
61.
62.
63.
Ryoichi Kikuchi 《Journal of statistical physics》1969,1(2):351-375
The factor of 1017 proposed by Lothe and Pound in the theory of nucleation of droplets from the vapor phase is studied using classical statistical mechanics. The controversial factor is derived from partition functions for an isolatedn-mer and for ann-molecular cluster imbedded in the bulk liquid phase. The rotational degrees of freedom have no place in, in agreement with Reiss, Katz, and Cohen's treatment. It is proved that the surface free energy of a cluster is proportional to the surface area. The estimate of what Lothe and Pound called the replacement term is different from those of previous authors. It is concluded that is written as a ratio =
g/l, where g and
l
, are the volumes per molecule in the gas phase and in the liquid phase, respectively. For water at 300K, is approximately equal to 104. 相似文献
64.
65.
Masanao Oya Tomoko Takahashi Ryoichi Katakai 《Journal of polymer science. Part A, Polymer chemistry》1976,14(8):2065-2069
4-Isobutyloxazolidinedione, L -leucine N-carboxy anhydride, was polymerized to produce high molecular weight polymer with triethylamine in n-hexane which is not a solvent for the N-carboxy anhydride and poly-L -leucine. It was found that as the crystal size became smaller, the total surface area was increased, the initial rate of polymerization was increased, and inherent viscosity of the formed polymer was decreased. 相似文献
66.
67.
Electronic absorption and magnetic circular dichroism (MCD) spectra in UV-vis region of Waugh-structure [XMo9O32]6?(X = Ni(IV), Mn(IV)) ion in aqueous solution and solid IR spectra have been measured. The Ni(IV) ion in the polyanion has a low-spin d6 electronic configuration and the Mn(IV) ion has a d3 configuration. Visible absorption spectrum of the nickelate(IV) polyanion is interpreted to be mainly governed by charge-transfer transitions of the “ligand”, Mo9O32, to Ni(IV) ion, rather than d-d transitions, while visible absorption of the manganate(IV) polyanion is governed, to a great extent, by d-d transitions. It is indicated by the MCD spectrum that the splitting of the first d-d absorption in the manganate(IV) polyanion is due to a contribution of the spin-forbiden transition, rather than from a trigonal splitting of the spin-allowed transition. Absorption and MCD spectra in UV region are due to charge-transfer transition within a common “ligand”, which are less influenced by the kind of heteroatom, Ni(IV) or Mn(IV). The MCD pattern by the intra-ligand charge-transfer is especially characteristic of the Waugh-structure polyanions. 相似文献
68.
Kishi N Kikuchi S Ramesh P Sugai T Watanabe Y Shinohara H 《The journal of physical chemistry. B》2006,110(49):24816-24821
Photoluminescence (PL) from purified (>90%) double-wall carbon nanotubes (DWNTs), which have been synthesized by zeolite catalyst-supported chemical vapor deposition (zeolite-CCVD), of very small diameters (0.8-nm average inner tube) is reported. The PL contour mappings for various ratios (1-90%) of double- versus single-wall carbon nanotubes by thermal oxidation have enabled us to unambiguously identify the chirality of inner tubes for the DWNTs synthesized. After the extensive high-temperature oxidation at 700 degrees C, high-purity (>90%) DWNTs of approximately 0.8 nm inner diameter are obtained, and most of these correspond to the DWNTs having inner tubes with chiralities of (7,5), (7,6), and (9,4). 相似文献
69.
Nakano M Kishi R Nakagawa N Ohta S Takahashi H Furukawa S Kamada K Ohta K Champagne B Botek E Yamada S Yamaguchi K 《The journal of physical chemistry. A》2006,110(12):4238-4243
The second hyperpolarizabilities of bisimidazole- and bistriazole-benzene compounds have been calculated at different levels of approximation to unravel the effects of diradical character as well as of charge and spin multiplicity. The largest second hyperpolarizabilities are associated with intermediate diradical character, provided positive charging does not compensate for this effect. For the neutral diradical bisimidazole compound, the singlet diradical species possesses a second hyperpolarizability two to three times larger than the corresponding triplet, demonstrating the possibility of spin state control of the third-order NLO responses for diradical species. 相似文献
70.
We study the efficiency at maximum power, η*, of engines performing finite-time Carnot cycles between a hot and a cold reservoir at temperatures Th and Tc, respectively. For engines reaching Carnot efficiency ηC=1-Tc/Th in the reversible limit (long cycle time, zero dissipation), we find in the limit of low dissipation that η* is bounded from above by ηC/(2-ηC) and from below by ηC/2. These bounds are reached when the ratio of the dissipation during the cold and hot isothermal phases tend, respectively, to zero or infinity. For symmetric dissipation (ratio one) the Curzon-Ahlborn efficiency ηCA=1-√Tc/Th] is recovered. 相似文献