全文获取类型
收费全文 | 956篇 |
免费 | 29篇 |
国内免费 | 2篇 |
专业分类
化学 | 642篇 |
晶体学 | 8篇 |
力学 | 14篇 |
数学 | 140篇 |
物理学 | 183篇 |
出版年
2023年 | 8篇 |
2022年 | 13篇 |
2021年 | 24篇 |
2020年 | 17篇 |
2019年 | 15篇 |
2018年 | 16篇 |
2017年 | 19篇 |
2016年 | 36篇 |
2015年 | 31篇 |
2014年 | 30篇 |
2013年 | 50篇 |
2012年 | 61篇 |
2011年 | 56篇 |
2010年 | 43篇 |
2009年 | 26篇 |
2008年 | 55篇 |
2007年 | 49篇 |
2006年 | 62篇 |
2005年 | 48篇 |
2004年 | 23篇 |
2003年 | 32篇 |
2002年 | 18篇 |
2001年 | 12篇 |
2000年 | 7篇 |
1999年 | 11篇 |
1998年 | 9篇 |
1997年 | 7篇 |
1996年 | 13篇 |
1995年 | 7篇 |
1994年 | 9篇 |
1993年 | 20篇 |
1992年 | 11篇 |
1991年 | 17篇 |
1990年 | 7篇 |
1989年 | 9篇 |
1988年 | 6篇 |
1986年 | 8篇 |
1985年 | 7篇 |
1984年 | 9篇 |
1983年 | 5篇 |
1982年 | 13篇 |
1981年 | 6篇 |
1980年 | 6篇 |
1979年 | 7篇 |
1978年 | 8篇 |
1977年 | 9篇 |
1976年 | 4篇 |
1975年 | 4篇 |
1974年 | 4篇 |
1944年 | 8篇 |
排序方式: 共有987条查询结果,搜索用时 0 毫秒
1.
The problem considered is that of determining the shape of aplane acoustically sound-soft obstacle from the knowledge ofthe far-field pattern for one time-harmonic incident field.An iterative procedure is proposed based on two boundary integralsrepresenting the incident field and the far-field pattern, respectively.Numerical examples are included which show that the proceduregives accurate numerical approximations in relatively few iterations. 相似文献
2.
6,7-Dimethoxy-2-naphthylethylamine, prepared by the diborane reduction of 6,7-dimethoxy-2-naphtlialeneacetamide, underwent a Pictet-Spengler cyclization to form 8,9-dimethoxy-1,2,3,4-tetrahydrobenz[h]isoquinoline. This compound is identical with that obtained by reduction of the corresponding dihydrobenzisoquinoline prepared from formamide cyclization. 6,7-Dialkoxy-2-naphthaleneacetic acids, the key intermediates for the preparation of these amides, were obtained from 6,7-dialkoxy-2-acetonaphthones by a modified Willgerodt reaction. 相似文献
3.
S. E. Arnell D. Foltescu H. A. Roth Ö. Skeppstedt A. Nilsson S. Mitarai J. Nyberg 《Zeitschrift für Physik A Hadrons and Nuclei》1993,346(2):111-117
The level structure of92Ru has been studied by means of γ-ray spectroscopy. The nucleus was produced by the58Ni(40Ca, α2p)92Ru reaction at beam energies of 147 and 187 MeV. The NORDBALL detector system including particle selection was used. A large number of new levels with excitation energies up to 11.3 MeV and spin values up to 22 or 23 units of angular momentum have been established. The level scheme is compared with recent shell model calculations using100Sn as a core. Some systematics of the g 9 2/?2 configuration is discussed and a strong correlation between the levels in90Mo and92Ru is found. 相似文献
4.
A method for the quantitative analysis of tricyclic antidepressants in the serum of psychiatric patients is described. The method can be used for determining amitriptyline, nortriptyline, imipramine, demethyllimipramine, clomipramine, demethylclomipramine, trimipramine and protriptyline. The method consists in a series of extraction steps followed by gas chromatography with flame-ionization detector. The drugs are determined in their native state. The internal standard method is used for the quantitation. 相似文献
5.
6.
7.
D. Seweryniak B. Cederwall J. Nyberg C. Fahlander A. Johnson A. Kerek J. Kownacki L. -O. Norlin E. Adamides A. Atac J. Blomqvist H. Grawe E. Ideguchi R. Julin S. Juutinen W. Karczmarczyk S. Mitarai M. Piiparinen R. Schubart G. Sletten S. Törmänen A. Virtanen 《Zeitschrift für Physik A Hadrons and Nuclei》1993,345(2):243-244
Neutron deficient nuclei close to 100Snhave been investigated in-beam by γ-ray spectroscopic methods using the NORDBALL detector array. A beam of 270 MeV 58Niwas used to bombard a target of 54Fe.Reaction channel separation was achieved with a 4π charged particle multidetector setup together with a 1π neutron detector wall placed in the forward direction. Excited states of 102Inwere identified for the first time. The level scheme constructed from γ-γ-particle-coincidence and γ-γ-angular correlation analysis is presented. The structure of 102 In is discussed and compared to neighboring nuclei in the framework of the nuclear shell-model. 相似文献
8.
A clustering method has been developed to group signals that display similar dynamic behavior. The procedure involves using the method of time delay embedding to construct a trajectory in state space from a time series. Certain features that characterize the geometry of the trajectory have been defined. These features were subjected to a series of statistical tests to determine their usefulness in a hierarchical clustering analysis. The latter is aimed at finding groups of similar trajectories. The trajectory-based clustering algorithm has been applied to simulated data, which included both stochastic data generated by a linear AR model, and nonlinear data generated by a Duffing oscillator. The results show that the algorithm works reliably in both cases. 相似文献
9.
10.
Martin Månsson Oscar Tjernberg Tomas Claesson Henrik S. Karlsson Ulf O. Karlsson 《Applied Surface Science》2006,252(15):5308-5311
Transiently excited electron states at the GaSb(0 0 1) surface have been studied by means of time- and angle-resolved photoemission spectroscopy based on a femtosecond laser system. A normally unpopulated surface electron state has been found at ∼250 meV above the valence band maximum with a strong confinement at the center of the surface Brillouin zone. The lifetime of transiently excited carriers at the intergap surface states has been found to be ∼11 ps, associated with rapid carrier diffusion. 相似文献