全文获取类型
收费全文 | 4688篇 |
免费 | 153篇 |
国内免费 | 28篇 |
专业分类
化学 | 3406篇 |
晶体学 | 43篇 |
力学 | 71篇 |
综合类 | 1篇 |
数学 | 265篇 |
物理学 | 1083篇 |
出版年
2022年 | 40篇 |
2021年 | 34篇 |
2020年 | 57篇 |
2019年 | 66篇 |
2018年 | 47篇 |
2017年 | 45篇 |
2016年 | 103篇 |
2015年 | 97篇 |
2014年 | 100篇 |
2013年 | 209篇 |
2012年 | 242篇 |
2011年 | 230篇 |
2010年 | 161篇 |
2009年 | 145篇 |
2008年 | 263篇 |
2007年 | 248篇 |
2006年 | 266篇 |
2005年 | 235篇 |
2004年 | 229篇 |
2003年 | 188篇 |
2002年 | 165篇 |
2001年 | 110篇 |
2000年 | 86篇 |
1999年 | 64篇 |
1998年 | 48篇 |
1997年 | 42篇 |
1996年 | 66篇 |
1995年 | 66篇 |
1994年 | 36篇 |
1993年 | 56篇 |
1992年 | 60篇 |
1991年 | 50篇 |
1990年 | 30篇 |
1989年 | 41篇 |
1988年 | 53篇 |
1987年 | 39篇 |
1986年 | 27篇 |
1985年 | 85篇 |
1984年 | 76篇 |
1983年 | 40篇 |
1982年 | 68篇 |
1981年 | 56篇 |
1980年 | 47篇 |
1979年 | 58篇 |
1978年 | 49篇 |
1977年 | 54篇 |
1976年 | 48篇 |
1975年 | 41篇 |
1974年 | 24篇 |
1973年 | 32篇 |
排序方式: 共有4869条查询结果,搜索用时 15 毫秒
951.
W. Bartel L. Becker C. Bowdery D. Cords R. Felst D. Haidt J. Huttunen H. Junge G. Knies H. Krehbiel P. Laurikainen R. Meinke B. Naroska J. Olsson E. Pietarinen D. Schmidt P. Steffen S. Yamada 《Physics letters. [Part B]》1984,139(4):327-331
We have searched for the supersymmetric partner of the photon, the photino, by investigating two-photon and single photon final states in e+e? collisions. No significant signals were observed, which excludes the existence of the photino in the mass range 0.08–18 GeV/c2 at the 95% confidence level, subject to the assumptions d=(100 GeV)2 and , where d is the supersymmetry breaking scale parameter and is the scalar electron mass. 相似文献
952.
953.
A diffusion anomaly in dipole-oriented two-dimensional excitons in GaAs/AlGaAs coupled quantum wells
Il Nuovo Cimento D - We have observed an anomaly in the low-temperature photoluminescence of dipole-oriented long-lived excitons in a coupled quantum well under an electrical bias. A discrepancy... 相似文献
954.
Sufficient conditions are obtained that guarantee the existence of at least two positive solutions for the equation (g(u′(t)))′+a(t)f(u)=0 subject to boundary conditions, by a simple application of a new fixed-point theorem due to Avery and Henderson. 相似文献
955.
K. Kasazaki K. Yasukawa H. Sano K. Yamada H. Utsumi 《Applied magnetic resonance》2003,23(3-4):585-595
In order to analyze free radical reactions in living stomach, we developed a noninvasive measurement by an in vivo electron spin resonance (ESR) and spin probe technique and applied it to mucosal injury. NH4OH-induced gastric lesions were prepared in rats. A nitroxyl probe was administered intragastrically or intravenously, and then in vivo ESR spectra of the gastric region were obtained by 300 MHz ESR spectroscopy. The signal of the intragastrically administered spin probe decreased gradually and the decay significantly enhanced 30 min after NH4OH administration. The enhanced signal decay was attributed to the OH radical generation, since it was completely suppressed by mannitol, catalase, and desferrioxamine. Two commercially available antigastric lesion drugs, rebamipide and taurine, were tested with a NH4OH-induced gastric lesion model. Both intraperitoneal administration of rebamipide and intravenous administration of taurine suppressed gastric lesion formation induced by NH4OH in a dose-dependent manner. Intraperitoneal preadministration of rebamipide also suppressed the enhanced signal decay, but neither pre- nor coadministration of taurine showed any effect on the enhanced signal decay. The results strongly indicate that the inhibitory mechanism on gastric lesion formation in NH4OH-treated rats is quite different for the two antigastric lesion drugs rebamipide and taurine. 相似文献
956.
The synthesis of marine dolabellane diterpenoids claenone, palominol and dolabellatrienone was conducted from d-mannitol. In each case, formation of the bicyclo[2.2.1]heptane derivative by sequential Michael reaction, preparation of the tetrasubstituted cyclopentane derivative by retro-aldol reaction and cyclization of sulfone were involved as key steps. 相似文献
957.
A total synthesis of the natural enantiomer of the title compound was accomplished, which confirmed the structure proposed for the fruiting-inducing cerebroside of . 相似文献
958.
Effect of the molecular structure on the gas-surface scattering
studied by supersonic molecular beam
T. Kondo H. S. Kato T. Yamada S. Yamamoto M. Kawai 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2006,38(1):129-138
The experimental apparatus for investigating the gas-surface interaction has
been newly developed. The coherent length of the helium, the energy
resolution and the angular spread of the beam in the apparatus were
established as ω= 16 nm,
DE/E = 2.4%\Delta E/E = 2.4{\%}
and Δθ= 0.5○, respectively, through the
measurements of the time-of-flight of He beam and of the angular intensity
distributions of He scattered from LiF(001). The angular intensity
distributions of Ar, N2 and CO scattered from the LiF(001) surface
along the [100] azimuthal direction were then measured as a function of
incident translational energy. The effects of the molecular structural
anisotropy and center-of-mass position on the gas-surface inelastic
collision at the corrugated surface are discussed with predictions based on
a recently developed simple classical theory of the ellipsoid-washboard
model. 相似文献
959.
Toshiya Okazaki Takeshi Saito Koji Matsuura Satoshi Ohshima Motoo Yumura Yuji Oyama Riichiro Saito Sumio Iijima 《Chemical physics letters》2006,420(4-6):286-290
Band gap photoluminescence (PL) behaviors of single-walled carbon nanotubes (SWNTs) grown by the methods of chemical vapor deposition and pulsed-laser vaporization are investigated over the wide diameter range (≈0.8–1.4 nm). The peak intensity of the PL signals strongly depends on chirality and the ‘(2n + m) family type’ of SWNTs. Based on the PL results, a population analysis of these SWNTs is conducted by combining the calculated PL yields for each (n, m) tube. The results are directly compared with the histograms of diameter distributions estimated by the transmission electron microscope (TEM) observations to check the validity of the analysis. 相似文献
960.
Akihiro Ohta Masami Inoue Junichi Yamada Yasuhiko Yamada Teruo Kurihara Toshihiro Honda 《Journal of heterocyclic chemistry》1984,21(1):103-106
Some 2,3-diphenylpyrazine 1-oxides were heated with acetic anhydride to give the corresponding 2,3-di-acetoxy-2,3-dihydro-5,6-diphenylpyrazines. By X-ray diffraction analysis, the configuration of two acetoxyl groups was determined to be trans. 相似文献