全文获取类型
收费全文 | 2084篇 |
免费 | 56篇 |
国内免费 | 1篇 |
专业分类
化学 | 1360篇 |
晶体学 | 40篇 |
力学 | 25篇 |
数学 | 132篇 |
物理学 | 584篇 |
出版年
2023年 | 13篇 |
2022年 | 20篇 |
2021年 | 18篇 |
2020年 | 21篇 |
2019年 | 19篇 |
2017年 | 12篇 |
2016年 | 35篇 |
2015年 | 54篇 |
2014年 | 43篇 |
2013年 | 93篇 |
2012年 | 84篇 |
2011年 | 95篇 |
2010年 | 62篇 |
2009年 | 45篇 |
2008年 | 84篇 |
2007年 | 82篇 |
2006年 | 58篇 |
2005年 | 73篇 |
2004年 | 61篇 |
2003年 | 54篇 |
2002年 | 68篇 |
2001年 | 47篇 |
2000年 | 54篇 |
1999年 | 31篇 |
1998年 | 43篇 |
1997年 | 28篇 |
1996年 | 40篇 |
1995年 | 30篇 |
1994年 | 39篇 |
1993年 | 40篇 |
1992年 | 32篇 |
1991年 | 23篇 |
1990年 | 26篇 |
1989年 | 20篇 |
1988年 | 22篇 |
1987年 | 24篇 |
1986年 | 23篇 |
1985年 | 30篇 |
1984年 | 39篇 |
1983年 | 22篇 |
1982年 | 29篇 |
1981年 | 20篇 |
1980年 | 33篇 |
1979年 | 23篇 |
1978年 | 23篇 |
1977年 | 36篇 |
1976年 | 17篇 |
1974年 | 28篇 |
1973年 | 12篇 |
1968年 | 13篇 |
排序方式: 共有2141条查询结果,搜索用时 15 毫秒
1.
2.
H. G. Bohlen W. von Oertzen R. Kalpakchieva B. Gebauer S. M. Grimes A. Lenz T. N. Massey M. Milin Ch. Schulz Tz. Kokalova S. Torilov S. Thummerer 《Physics of Atomic Nuclei》2003,66(8):1494-1500
The structure of neutron-rich beryllium isotopes has been investigated using different heavy-ion-induced transfer reactions. In neutron transfer reactions, the population of final states shows a strong sensitivity to the chosen core nucleus, i.e., the target nuclei 9Be or 10Be, respectively. Molecular rotational bands up to high excitation energies are observed with 9Be as the core due to its pronounced 2α-cluster structure, whereas only a few states at low excitation energies are populated with 10Be as the core. For 11Be, a detailed investigation has been performed for the three states at 3.41, 3.89, and 3.96 MeV, which resulted in the most probable spin-parity assignments 3/2+, 5/2?, and 3/2?, respectively. Furthermore, we have studied particle-hole states of 16C using the 13C(12C, 9C)16C reaction and found 14 previously unknown states. Using the 12C(12C, 9C)15C reaction, five new states were observed for 15C. 相似文献
3.
Emily S. Tepe Ellen S. Deutsch MD Quiana Sampson Stephen Lawless James S. Reilly Robert Thayer Sataloff 《Journal of voice》2002,16(2):244-250
The objective of this study was to determine the incidence of vocal problems in young choir singers and to correlate vocal problems with demographic and behavioral information. A questionnaire addressing vocal habits and hygiene was offered to 571 young choir singers, up to 25 years of age, who sing at least weekly; 129 (22.6%) responded. More than one-half of the respondents had experienced vocal difficulty, particularly older adolescents. Detrimental behaviors and circumstances surveyed were not reflective of the incidence of vocal difficulty, except for morning hoarseness, chronic fatigue, insomnia, and female gender after puberty. Voice care professionals should be aware that self-reported voice difficulties are common among young choral singers, especially postpubescent girls, and children with symptoms consistent with reflux (morning hoarseness) and emotional stress (insomnia). Laryngologists should communicate with choral conductors and singing teachers to enhance early identification and treatment of children with voice complaints, and to develop choral educational strategies that help decrease their incidence. 相似文献
4.
We introduce a new technique for imaging oxygen concentrations in fuel/air mixtures that takes advantage of the different
responses of toluene and 3-pentanone to collisional quenching by molecular oxygen. Since laser-induced fluorescence signals
from both tracers upon excitation at 248 nm are spectrally well separated, simultaneous detection is possible. The technique
is first applied to instantaneous imaging in turbulent mixing processes of interacting seeded air and nitrogen flows.
Received: 1 August 2001 / Revised version: 29 October 2001 / Published online: 29 November 2001 相似文献
5.
Summary The solubility parameters of cationic surfactants were obtained using the inverse gas chromatographic technique. The surfactants
didodecyl dimethyl ammonium bromide, dioctadecyl dimethyl ammonium bromide and dodecyl pyridinium chloride were used as stationary
phase and retention data of different probe solutes were measured at different temperatures. The results were analysed by
the combination of Flory-Huggins and Hildebrand theories, and the solubility parameters of the surfactants were obtained in
a range of temperatures between 80–120°C. 相似文献
6.
7.
8.
9.
Strains of Escherichia coli, Pseudomonas aeruginosa and Proteus mirabilis, isolated from clinical specimens were disrupted by repeated freezing in liquid nitrogen and thawing at room temperature. The samples were separated by isoelectric focusing using polyacrylamide gels. The resulting protein patterns showed clear differences between the three species and made identification possible. 相似文献
10.
In this paper we present a new method for the solution of optimization problems with PDE constraints. It is based on simultaneous pseudo-time stepping for evolution equations. The new method can be viewed as a continuous reduced SQP method in the sense that it uses a preconditioner derived from that method. The reduced Hessian in the preconditioner is approximated by a pseudo-differential operator, whose symbol can be investigated analytically. We apply our method to a boundary control model problem. The new optimization method needs 3.2-times the overall computational effort of the solution of simulation problem alone. 相似文献