全文获取类型
收费全文 | 123篇 |
免费 | 2篇 |
专业分类
化学 | 86篇 |
力学 | 1篇 |
数学 | 6篇 |
物理学 | 32篇 |
出版年
2018年 | 2篇 |
2017年 | 2篇 |
2016年 | 4篇 |
2013年 | 4篇 |
2012年 | 3篇 |
2011年 | 7篇 |
2010年 | 6篇 |
2009年 | 3篇 |
2007年 | 8篇 |
2006年 | 3篇 |
2005年 | 3篇 |
2003年 | 8篇 |
2001年 | 1篇 |
2000年 | 2篇 |
1999年 | 1篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1985年 | 2篇 |
1983年 | 2篇 |
1981年 | 1篇 |
1974年 | 1篇 |
1958年 | 1篇 |
1956年 | 1篇 |
1955年 | 3篇 |
1954年 | 2篇 |
1949年 | 1篇 |
1940年 | 3篇 |
1937年 | 3篇 |
1936年 | 2篇 |
1935年 | 2篇 |
1933年 | 3篇 |
1932年 | 2篇 |
1931年 | 2篇 |
1930年 | 1篇 |
1929年 | 1篇 |
1928年 | 1篇 |
1927年 | 5篇 |
1926年 | 1篇 |
1925年 | 1篇 |
1924年 | 3篇 |
1920年 | 2篇 |
1916年 | 1篇 |
1914年 | 3篇 |
1913年 | 3篇 |
1911年 | 1篇 |
1906年 | 2篇 |
排序方式: 共有125条查询结果,搜索用时 15 毫秒
41.
42.
Gijsbertsen A Siu W Kling MF Johnsson P Jansen P Stolte S Vrakking MJ 《Physical review letters》2007,99(21):213003
We report a novel approach for determining the sign of permanent dipole moments, using nitric oxide [NO(v=0)] as an example. State-selected NO (j=|m|=|Omega=1/2) molecules are focused using a hexapole and oriented in a strong dc electric field. The angular distributions of ionic fragments resulting from extreme ultraviolet single-photon and multiphoton dissociative ionization at 400 and 800 nm are measured and indicate that the dipole moment is negative (corresponding to N-O+). The experiments thus rule out an error in the sign of the dipole of NO as the possible source of a remarkable discrepancy between previous theoretical and experimental work on orientation effects in bimolecular collisions involving oriented NO. 相似文献
43.
We report on experiments investigating quantum transport and band interferometry of an atomic Bose-Einstein condensate in an optical lattice with a two-band miniband structure, realized with a Fourier-synthesized optical lattice potential. Bloch-Zener oscillations, the coherent superposition of Bloch oscillations and Landau-Zener tunneling between the two bands, are observed. When the relative phase between paths in different bands is varied, an interference signal is observed, demonstrating the coherence of the dynamics in the miniband system. Measured fringe patterns of this Stückelberg interferometer allow us to interferometrically map out the band structure of the optical lattice over the full Brillouin zone. 相似文献
44.
45.
Within a variational approach to solving the Gross-Pitaevskii equation we investigate dynamical properties of a rotating Bose-Einstein condensate confined in an anharmonic trap. In particular, we calculate the eigenfrequencies of low-energy excitations out of the equilibrium state and the aspect ratio of the condensate widths during the free expansion. 相似文献
46.
47.
48.
A major property-casualty insurance company had streamlined underwriting procedures and hoped to design a new commercial insurance package which would appeal to its independent agents. They hoped to do this by improving service times, premium and/or commission, but making these improvements would require the agents to fill out a new underwriting form. The research used conjoint analysis to determine for management the optimum levels of each of the factors to be employed in the new programme and the possible negative impact of the new underwriting form. Also discussed are issues relating to the use of conjoint analysis; in particular, the handling of large factorial designs and the aggregation of individual results. 相似文献
49.
50.
Cahoon JF Kling MF Schmatz S Harris CB 《Journal of the American Chemical Society》2005,127(36):12555-12565
The role of 19-electron intermediates in the photochemical disproportionation of [CpW(CO)3]2 (Cp = C5H5) with Lewis bases (PR3; R = OMe, Bu, Ph) is investigated on the ultrafast time scale using femtosecond VIS-pump, IR-probe spectroscopy. Formation of a 19-electron (19e) species CpW(CO)3PR3*by coordination of PR3 with photogenerated 17-electron (17e) radicals CpW(CO)3* is directly observed, and equilibrium is established between the 17e radicals and the 19e intermediates favoring 19e intermediates in the order: Bu > OMe > Ph. Steric effects dominate the 17e/19e equilibrium when the cone-angle of the Lewis base exceeds a certain limiting value (between 132 degrees and 145 degrees ), but below this value electronic properties of the Lewis base control the 17e/19e dynamics. Disproportionation occurs in less than 200 picoseconds by electron transfer between a solvent caged 17e radical and 19e, highly reducing species. The rate and extent of ultrafast disproportionation depends on both the identity and concentration of the Lewis base. In low concentrations of PR3 (typically 1-2 M or less) or with Lewis bases whose equilibrium heavily favors 17e radicals (e.g., PPh3), disproportionation is rate-limited by breakdown of the solvent cage. Density functional theory calculations on vibrational frequencies and charge distributions of the various complexes support the experimental results. 相似文献