全文获取类型
收费全文 | 436篇 |
免费 | 12篇 |
国内免费 | 1篇 |
专业分类
化学 | 283篇 |
晶体学 | 8篇 |
力学 | 4篇 |
数学 | 20篇 |
物理学 | 134篇 |
出版年
2023年 | 4篇 |
2022年 | 4篇 |
2021年 | 1篇 |
2020年 | 2篇 |
2019年 | 8篇 |
2018年 | 7篇 |
2017年 | 10篇 |
2016年 | 11篇 |
2015年 | 11篇 |
2014年 | 9篇 |
2013年 | 18篇 |
2012年 | 34篇 |
2011年 | 33篇 |
2010年 | 20篇 |
2009年 | 23篇 |
2008年 | 19篇 |
2007年 | 28篇 |
2006年 | 24篇 |
2005年 | 32篇 |
2004年 | 21篇 |
2003年 | 20篇 |
2002年 | 18篇 |
2001年 | 4篇 |
2000年 | 3篇 |
1999年 | 5篇 |
1998年 | 2篇 |
1997年 | 5篇 |
1996年 | 3篇 |
1995年 | 1篇 |
1994年 | 5篇 |
1993年 | 7篇 |
1992年 | 3篇 |
1991年 | 4篇 |
1989年 | 1篇 |
1988年 | 3篇 |
1987年 | 5篇 |
1986年 | 2篇 |
1985年 | 5篇 |
1984年 | 3篇 |
1982年 | 3篇 |
1981年 | 5篇 |
1980年 | 2篇 |
1979年 | 8篇 |
1978年 | 6篇 |
1977年 | 2篇 |
1976年 | 3篇 |
1974年 | 1篇 |
1963年 | 1篇 |
排序方式: 共有449条查询结果,搜索用时 0 毫秒
1.
Yue Liu Masahito Ohta Grozdena Todorova 《Annales de l'Institut Henri Poincaré (C) Analyse Non Linéaire》2007
We study here instability problems of standing waves for the nonlinear Klein–Gordon equations and solitary waves for the generalized Boussinesq equations. It is shown that those special wave solutions may be strongly unstable by blowup in finite time, depending on the range of the wave's frequency or the wave's speed of propagation and on the nonlinearity. 相似文献
2.
Kunio Miki Yasushi Kai Noritake Yasuoka Nobutami Kasai 《Journal of organometallic chemistry》1979,165(1):79-91
The precise molecular structure of [PdCl(CH2SCH3)(PPh3)2] has been determined from three-dimensional X-ray diffraction data collected at ?160°C. The CH2Cl2 solvated crystal ([PdCl(CH2SCH3)(PPh3)2 · CH2Cl2]) belongs to the monoclinic system, space group P21/n, with four formula units in a cell of dimensions: a 14.973(3), b 15.333(3), c 17.377(3) Å and β 115.77(1)° at ?160°C. The structure was solved by the conventional heavy atom method and refined by the least-squares procedure to R = 0.035 for observed reflections. The geometry around the palladium atom is square-planar. The phosphorus atoms of the two triphenylphosphine ligands are mutually trans. The CH2SCH3 group is bonded to the palladium atom only through the PdC σ-bond and the sulfur atom is not bonded to the metal atom (PdC(1) 2.061(3), SC(1) 1.796(3), SC(2) 1.817(5), Pd?S 2.973(1) Å, PdC(1)S 100.64(14)° and C(1)SC(2) 101.28(18)°). The structure is in contrast to that of [PdCl(CH2SCH3)(PPh3)], in which both the carbon and sulfur atoms of the CH2SCH3 group are bonded to the palladium atom. 相似文献
3.
Sun-Chan Jeong Ichiro Katayama Hirokane Kawakami Yutaka Watanabe Hironobu Ishiyama Nobuaki Imai Yoshikazu Hirayama Hiroari Miyatake Masao Sataka Hiroyuki Sugai Satoru Okayasu Shin-Ichi Ichikawa Katsuhisa Nishio Shinichi Mitsuoka Takamitsu Nakanoya Takashi Hashimoto Takanori Hashimoto Masahito Yahagi 《Solid State Ionics》2009,180(6-8):626-630
The diffusion coefficients of Li in the NaTl-type Li intermetallic compound of β-LiGa have been measured by using a short-lived radioactive diffusion tracer. As the tracer, the α-emitting radioisotope of 8Li delivered as the energetic and pulsed beam from Tokai Radioactive Ion Accelerator Complex (TRIAC) was implanted into the β-LiGa compounds with the composition in the range of about 43 to 54 at.% Li. By analyzing the time-dependent yields of the α-particles measured according to the repetition cycle of the beam, the tracer diffusion coefficients were extracted over the wide range of Li composition. Abnormal composition-dependence of Li diffusion coefficients in β-LiGa was observed; the stoichiometric β-LiGa showed the highest diffusivity of Li. By referring to the composition-dependent diffusivity of Li in the iso-structural β-LiAl and β-LiIn, we could identify the abnormal diffusion of Li in very Li-poor composition of β-LiGa. The anomaly has been discussed qualitatively in terms of the formation of defect complex and the interaction between the constitutional defects. 相似文献
4.
Masahito Sekiguchi Hiromichi Tanaka Noriaki Takami Akiya Ogawa Ilhyong Ryu Noboru Sonoda 《Heteroatom Chemistry》1991,2(3):427-430
The reduction of elemental selenium by samarium diiodide led to selective formation of selenolate anion species (Se2− and Se22−), the alkylation of which provided dialkyl selenides and diselenides, respectively, in excellent yields. 相似文献
5.
6.
Masahito Tagawa Kumiko Yokota Koji Matsumoto Yuden Teraoka Masahito Niibe 《Applied Surface Science》2010,256(24):7678-7683
Surface structural changes of a hydrogenated diamond-like carbon (DLC) film exposed to a hyperthermal atomic oxygen beam were investigated by Rutherford backscattering spectroscopy (RBS), synchrotron radiation photoelectron spectroscopy (SR-PES), and near-edge X-ray absorption fine structure (NEXAFS). It was confirmed that the DLC surface was oxidized and etched by high-energy collisions of atomic oxygen. RBS and real-time mass-loss data showed a linear relationship between etching and atomic oxygen fluence. SR-PES data suggested that the oxide layer was restricted to the topmost surface of the DLC film. NEXAFS data were interpreted to mean that the sp2 structure at the DLC surface was selectively etched by collisions with hyperthermal atomic oxygen, and an sp3-rich region remained at the topmost DLC surface. The formation of an sp3-rich layer at the DLC surface led to surface roughening and a reduced erosion yield relative to the pristine DLC surface. 相似文献
7.
We show that quasi-Nambu-Goldstone (NG) modes, which play prominent roles in high energy physics but have been elusive experimentally, can be realized with atomic Bose-Einstein condensates. The quasi-NG modes emerge when the symmetry of a ground state is larger than that of the Hamiltonian. When they appear, the conventional vacuum manifold should be enlarged. Consequently, topological defects that are stable within the conventional vacuum manifold become unstable and decay by emitting the quasi-NG modes. Contrary to conventional wisdom, however, we show that the topological defects are stabilized by quantum fluctuations that make the quasi-NG modes massive, thereby suppressing their emission. 相似文献
8.
Ochiai M Tada N Murai K Goto S Shiro M 《Journal of the American Chemical Society》2006,128(30):9608-9609
Stable aliphatic bromonium ylides (RfSO2)2C--Br+C6H4-p-CF3 (Rf = CF3, CF3(CF2)3) have been synthesized and structurally characterized for the first time. X-ray crystallographic analyses indicated a ylide structure with an sp2 hybridization of the ylide carbanions and with little double-bond character for the ylidic bond. The bromonium ylides selectively undergo transfer of the aryl group to nitrogen heterocycles, such as pyridines, yielding N-arylpyridinium salts. This is in a marked contrast to the reaction of the iodonium ylides, which produces pyridinium ylides through transylidations. 相似文献
9.
10.
Thomas M. Baker Lisa A. Sloan Lokman H. Choudhury Masahito Murai David J. Procter 《Tetrahedron: Asymmetry》2010,21(9-10):1246-1261
A cascade reaction involving sequential conjugate reduction, stereoselective aldol cyclisation and chemoselective lactone reduction mediated by SmI2–H2O provides access to a cyclopentanol bearing two vicinal quaternary stereocentres with good stereocontrol. The functionalised cyclopentanol product has been converted to a key intermediate in ongoing asymmetric studies towards stolonidiol. 相似文献