全文获取类型
收费全文 | 754篇 |
免费 | 25篇 |
国内免费 | 4篇 |
专业分类
化学 | 551篇 |
晶体学 | 13篇 |
力学 | 13篇 |
数学 | 31篇 |
物理学 | 175篇 |
出版年
2023年 | 5篇 |
2022年 | 4篇 |
2021年 | 14篇 |
2020年 | 7篇 |
2019年 | 16篇 |
2018年 | 7篇 |
2017年 | 8篇 |
2016年 | 21篇 |
2015年 | 11篇 |
2014年 | 21篇 |
2013年 | 34篇 |
2012年 | 36篇 |
2011年 | 35篇 |
2010年 | 27篇 |
2009年 | 32篇 |
2008年 | 41篇 |
2007年 | 34篇 |
2006年 | 37篇 |
2005年 | 23篇 |
2004年 | 29篇 |
2003年 | 24篇 |
2002年 | 23篇 |
2001年 | 23篇 |
2000年 | 20篇 |
1999年 | 14篇 |
1998年 | 8篇 |
1997年 | 12篇 |
1996年 | 11篇 |
1995年 | 6篇 |
1994年 | 7篇 |
1993年 | 9篇 |
1992年 | 10篇 |
1991年 | 16篇 |
1990年 | 6篇 |
1989年 | 5篇 |
1988年 | 12篇 |
1987年 | 6篇 |
1986年 | 9篇 |
1985年 | 17篇 |
1984年 | 11篇 |
1983年 | 5篇 |
1982年 | 11篇 |
1981年 | 10篇 |
1980年 | 5篇 |
1979年 | 16篇 |
1978年 | 9篇 |
1977年 | 8篇 |
1974年 | 5篇 |
1973年 | 3篇 |
1968年 | 4篇 |
排序方式: 共有783条查询结果,搜索用时 0 毫秒
741.
742.
Summary Octadecyl-porous glass was prepared and used as the packing for reversed-phase high-performance liquid chromatography. A mixture
of ginsenosides, saponins of ginseng was analyzed with detection at 203 nm. Ginsenosides Rf, Rg2, Rb1, Rc, Rb2, and Rd were separated with acetonitrile-water (27.5:72.5) as the mobile phase. A well-resoluted chromatogram of ginsenosides
Ro, Rg1 and Re was also obtained with acetonitrile-water (16.5:83.5). The whole separation was achieved in 12 min with a flowrate
of 1 ml/min. Calibration curves of ginsenosides Rb1, Rc, Rb2, Rd, Rg1 and Re were linear up to 5 μg. It can be concluded that the rapid and accurate analysis of ginsenosides is possible by the
described method. 相似文献
743.
Fabrication of photonic crystals in ZnS-doped glass 总被引:3,自引:0,他引:3
Three-dimensional photonic crystals were fabricated in a ZnS-doped silicate glass by use of a femtosecond pulsed laser. Woodpile structures consisting of 36 layers were produced by focusing with a 100x (1.35-numerical-aperture) objective. Attenuations of approximately 3-8 dB arising from a photonic bandgap were observed in the visible and the near-infrared regions. 相似文献
744.
Summary Ultraviolet-absorbing components of human urine were separated by HPLC with a large scale column (250 × 28 mm I.D. stainless-steel)
containing a macroreticular type strongly basic anion-exchange resin. The sample was eluted with a linear gradient of 0.006
M to 6.0 M ammonium acetate buffer (pH 4.40) and different fractions were collected. The identification of one compound using
ultraviolet, infrared and mass spectral data is illustrated; it was found to be uric acid. 相似文献
745.
Nagata M Oguro T Kagei Y Kawami K Hasegawa H Fukumoto N Iida M Masamune S Katsurai M Uyama T 《Physical review letters》2003,90(22):225001
In order to understand self-organization in helicity-driven systems, we have investigated the dynamics of low-aspect-ratio toroidal plasmas by decreasing the external toroidal field and reversing its sign in time. Consequently, we have discovered that the helicity-driven toroidal plasma relaxes towards the flipped state. Surprisingly, it has been observed that not only toroidal flux but also poloidal flux reverses sign spontaneously during the relaxation process. The self-reversal of the magnetic fields is attributed to the nonlinear growth of the n=1 kink instability of the central open flux. 相似文献
746.
Tsuneo?OkuboEmail author Takehiro?Miyamoto Kouji?Umemura Takuya?Noguchi Kenji?Kobayashi Akira?Tsuchida 《Colloid and polymer science》2003,281(11):1055-1061
Kinetic analyses are made for the seed polymerization of tetraethyl orthosilicate (TEOS) in the presence of anionic and cationic polystyrene colloidal sphere seeds by turbidity and dynamic light-scattering measurements. Transmission-electron microscopy pictures of the spheres formed are also used. The seed polymerization of TEOS is difficult to take place on the surface of anionic polystyrene spheres (44–212 nm in diameter). On the other hand, the reaction proceeds easily on the cationic polystyrene spheres. Hairy and soft surfaces of polystyrene spheres will disturb the seed polymerization. Furthermore, the electrostatic attraction between the anionic hydrolytic products of TEOS molecules and cationic polystyrene spheres plays an important role for the seed polymerization. 相似文献
747.
748.
M. Okada M. Saito M. Takatsu K. Kosemura T. Nagata H. Ishiwari N. Yokoyama 《Superlattices and Microstructures》1991,10(4)
This paper reports on the measurement of the angular distribution of electrons injected through a quantum point contact. We observed double peaks in the distribution with the point contact quantized in two modes. Our calculation of the distribution using an approximation of Fraunhofer diffraction through a quantized single slit agreed well with results. This paper also discusses the interference between the first and second modes, and shows how the terms of interference in the angular distribution are canceled. 相似文献
749.
750.
Decomposition of chlorofluorocarbons and hydrofluorocarbons in water by ultrasonic irradiation 总被引:3,自引:0,他引:3
The sonochemical degradation of CFC-113 (F2ClC---CCl2F), HCFC-225ca (F3C---CF2CCl2H), HCFC-225cb (F2ClC---CF2---CClFH) and HFC-134a (F3C---CF2H) in water was investigated. The decomposition rates of CFC-113 increased with increasing the concentration of the CFC and at high concentration the rates far exceeded the rate of OH radical formation by water sonolysis, and OH radicals seemed to have little effect on the decomposition. The pyrolysis in the cavitation bubbles was suggested. 相似文献