全文获取类型
收费全文 | 1234篇 |
免费 | 56篇 |
国内免费 | 1篇 |
专业分类
化学 | 445篇 |
晶体学 | 66篇 |
力学 | 18篇 |
数学 | 222篇 |
物理学 | 540篇 |
出版年
2023年 | 7篇 |
2022年 | 5篇 |
2021年 | 25篇 |
2020年 | 15篇 |
2019年 | 21篇 |
2018年 | 29篇 |
2017年 | 19篇 |
2016年 | 38篇 |
2015年 | 47篇 |
2014年 | 46篇 |
2013年 | 62篇 |
2012年 | 65篇 |
2011年 | 64篇 |
2010年 | 54篇 |
2009年 | 43篇 |
2008年 | 151篇 |
2007年 | 181篇 |
2006年 | 209篇 |
2005年 | 33篇 |
2004年 | 23篇 |
2003年 | 28篇 |
2002年 | 26篇 |
2001年 | 16篇 |
2000年 | 34篇 |
1999年 | 10篇 |
1998年 | 10篇 |
1997年 | 7篇 |
1996年 | 3篇 |
1995年 | 2篇 |
1994年 | 4篇 |
1993年 | 1篇 |
1992年 | 2篇 |
1991年 | 2篇 |
1989年 | 2篇 |
1988年 | 1篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1982年 | 1篇 |
1976年 | 1篇 |
排序方式: 共有1291条查询结果,搜索用时 351 毫秒
1.
2.
Given an ‐vertex pseudorandom graph and an ‐vertex graph with maximum degree at most two, we wish to find a copy of in , that is, an embedding so that for all . Particular instances of this problem include finding a triangle‐factor and finding a Hamilton cycle in . Here, we provide a deterministic polynomial time algorithm that finds a given in any suitably pseudorandom graph . The pseudorandom graphs we consider are ‐bijumbled graphs of minimum degree which is a constant proportion of the average degree, that is, . A ‐bijumbled graph is characterised through the discrepancy property: for any two sets of vertices and . Our condition on bijumbledness is within a log factor from being tight and provides a positive answer to a recent question of Nenadov. We combine novel variants of the absorption‐reservoir method, a powerful tool from extremal graph theory and random graphs. Our approach builds on our previous work, incorporating the work of Nenadov, together with additional ideas and simplifications. 相似文献
3.
Bi Dongxue Sverbil Pavel P. Voinov Yury P. Wu Mengyuan 《Journal of Russian Laser Research》2021,42(6):671-676
Journal of Russian Laser Research - We discuss the use of high-pressure high-temperature (HPHT) diamonds for the determination of trace amounts of various Raman active substances. The amount of the... 相似文献
4.
5.
The dynamics of multiphoton transitions in a two-level spin system excited by transverse microwave and longitudinal RF fields with the frequencies ωmw and ωrf, respectively, is analyzed. The effective time-independent Hamiltonian describing the “dressed” spin states of the “spin + bichromatic field” system is obtained by using the Krylov-Bogoliubov-Mitropolsky averaging method. The direct detection of the time behavior of the spin system by the method of nonstationary nutations makes it possible to identify the multiphoton transitions for resonances ω0 = ωmw + rωrf (ω0 is the central frequency of the EPR line, r = 1, 2), to measure the amplitudes of the effective fields of these transitions, and to determine the features generated by the inhomogeneous broadening of the EPR line. It is shown that the Bloch-Siegert shifts for multiphoton resonances at the inhomogeneous broadening of spectral lines reduce only the nutation amplitude but do not change their frequencies. 相似文献
6.
Results of an experiment on investigating the fluctuations of a sound signal with a frequency of 295 Hz on a stationary 32-km-long acoustic path in a shallow sea are presented. Hydrological conditions on the path were characterized by the presence of a weak thermocline and a frequent occurrence of intense internal wave trains. The space-time characteristics of these internal waves were measured in detail. Experimental evidence of the repetition of the forms of internal solitons in the variations of the amplitude and phase of an acoustic signal was obtained. 相似文献
7.
8.
9.
10.
The influence of a large signal on the characteristics of a small signal near the frequency of the former is experimentally studied for the case of their simultaneous propagation through a resonant transmission line based on backward volume magnetostatic waves. The effects observed are caused by the excitation of spin waves in a ferromagnetic film at different large-signal frequencies and by the back influence of excited spin-wave packets on the amplitude and phase characteristics of the small signal. 相似文献