全文获取类型
收费全文 | 235篇 |
免费 | 2篇 |
专业分类
化学 | 131篇 |
晶体学 | 6篇 |
力学 | 1篇 |
数学 | 6篇 |
物理学 | 93篇 |
出版年
2020年 | 4篇 |
2018年 | 3篇 |
2017年 | 5篇 |
2016年 | 7篇 |
2015年 | 3篇 |
2014年 | 4篇 |
2013年 | 13篇 |
2012年 | 6篇 |
2011年 | 4篇 |
2010年 | 2篇 |
2009年 | 5篇 |
2008年 | 8篇 |
2007年 | 2篇 |
2006年 | 13篇 |
2005年 | 16篇 |
2004年 | 14篇 |
2003年 | 12篇 |
2002年 | 9篇 |
2001年 | 3篇 |
2000年 | 8篇 |
1999年 | 7篇 |
1997年 | 5篇 |
1995年 | 5篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1992年 | 3篇 |
1991年 | 3篇 |
1990年 | 5篇 |
1989年 | 1篇 |
1988年 | 6篇 |
1987年 | 2篇 |
1986年 | 4篇 |
1985年 | 3篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1980年 | 4篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1977年 | 4篇 |
1976年 | 1篇 |
1974年 | 3篇 |
1973年 | 1篇 |
1970年 | 1篇 |
1968年 | 1篇 |
1967年 | 2篇 |
1966年 | 4篇 |
1965年 | 11篇 |
1963年 | 2篇 |
排序方式: 共有237条查询结果,搜索用时 15 毫秒
41.
Yoswathananont N Nitta K Nishiuchi Y Sato M 《Chemical communications (Cambridge, England)》2005,(1):40-42
Continuous flow of the substrate solution and hydrogen gas through a tube reactor packed with Pd/C catalyst brings about a highly reactive and efficient hydrogenation system, which converts 4-cyanobenzaldehyde to the benzyl alcohol derivatives at 25 degrees C, and at 90 degrees C, the cyano group becomes reduced to give the corresponding amine and toluene derivatives within 2 min. 相似文献
42.
Revised structure of terchebin is shown by II-B. Granatin B, a new ellagitannin, has structure V in which partial structure Ic?Id is enantiomeric to Ia?Ib in II-B and geraniin. 相似文献
43.
44.
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
45.
We completely determine the moduli space M(N,k) of k vortices in U(N) gauge theory with N Higgs fields in the fundamental representation. Its open subset for separated vortices is found as the symmetric product (CxCP(N-1))k/(see text)k. Orbifold singularities of this space correspond to coincident vortices and are resolved resulting in a smooth moduli manifold. The relation to K?hler quotient construction is discussed. 相似文献
46.
Dapeng Cai Takashi Gyoshin Nitta 《Journal of Difference Equations and Applications》2013,19(3):359-373
In this paper, we consider how to construct the optimal solutions for the undiscounted discrete time infinite horizon optimization problems. We present the conditions under which the limit of the solutions for the finite horizon problems is optimal among all attainable paths for the infinite horizon problem under two modified overtaking criteria, as well as the conditions under which it is the unique optimum under the sum-of-utilities criterion. The results are applied to a parametric example of a simple one-sector growth model to examine the impacts of discounting on the optimal path. 相似文献
47.
A complete set of elastic constants C ij and piezoelectric coefficients e ij of a La3Ga5SiO14 (langasite) single crystal was determined from 5.5 to 275.5?K by resonant ultrasound spectroscopy. Unlike a conventional crystal, the elastic constants C ij of the langasite crystal showed three types of temperature dependence: (i) monotonic elastic stiffening upon cooling (C 44 and C 14); (ii) monotonic elastic softening (C 66); and (iii) a stiffening-to-softening transition below 150?K (C 11, C 12, C 13 and C 33). In addition, a strong correlation between C 66 and the piezoelectric coefficient e 11 was confirmed. Group theoretical lattice dynamics analysis revealed that the novel phenomena of elastic softening and strong correlation are explained on the basis of two types of optical mode internal displacements which have the totally symmetric A 1 and doubly degenerated E symmetries in the point group D 3. 相似文献
48.
49.
50.
An experimental study on unsteady turbulent near wake of a rectangular cylinder in channel flow 总被引:1,自引:0,他引:1
Unsteady turbulent near wake of a rectangular cylinder in channel flow has been studied experimentally with a laser Doppler
velocimetry (LDV). The time-averaged and phase-averaged statistics were measured for the cylinders having various width-to-height
ratios, b/h. It is shown that the turbulent intensities on the centerline of the channel have their maxima near the rear stagnation point
of a recirculation region. The contours of coherent vorticity and streamline reproduce clearly the shed vortices from the
cylinder observed by the flow visualization. The characteristics of the flow field, which depends on b/h, are discussed and the significant contribution of the coherent structure to the flow field is clarified. Moreover, the turbulent
kinetic energy budget has been examined.
Received: 19 January 1998/Accepted: 21 July 1998 相似文献