全文获取类型
收费全文 | 724篇 |
免费 | 9篇 |
国内免费 | 1篇 |
专业分类
化学 | 438篇 |
晶体学 | 8篇 |
力学 | 6篇 |
数学 | 22篇 |
物理学 | 111篇 |
无线电 | 149篇 |
出版年
2022年 | 4篇 |
2019年 | 3篇 |
2018年 | 6篇 |
2017年 | 5篇 |
2016年 | 6篇 |
2015年 | 3篇 |
2014年 | 8篇 |
2013年 | 20篇 |
2012年 | 21篇 |
2011年 | 19篇 |
2010年 | 13篇 |
2009年 | 17篇 |
2008年 | 32篇 |
2007年 | 20篇 |
2006年 | 35篇 |
2005年 | 25篇 |
2004年 | 19篇 |
2003年 | 16篇 |
2002年 | 24篇 |
2001年 | 22篇 |
2000年 | 15篇 |
1999年 | 20篇 |
1998年 | 20篇 |
1997年 | 12篇 |
1996年 | 15篇 |
1995年 | 17篇 |
1994年 | 22篇 |
1993年 | 17篇 |
1992年 | 31篇 |
1991年 | 17篇 |
1990年 | 15篇 |
1989年 | 27篇 |
1988年 | 19篇 |
1987年 | 16篇 |
1986年 | 25篇 |
1985年 | 28篇 |
1984年 | 7篇 |
1983年 | 13篇 |
1982年 | 7篇 |
1981年 | 12篇 |
1980年 | 7篇 |
1979年 | 6篇 |
1978年 | 6篇 |
1977年 | 6篇 |
1976年 | 6篇 |
1974年 | 5篇 |
1965年 | 3篇 |
1940年 | 3篇 |
1939年 | 3篇 |
1938年 | 3篇 |
排序方式: 共有734条查询结果,搜索用时 984 毫秒
111.
A high-speed GaAs monolithic integrated decision circuit for Gbit/s optical repeaters, based on source coupled FET logic (SCFL) and designed to be completely ECL-compatible, has been developed. A clock phase margin of 150 degrees at 2 Gbit/s and IC yields of about 60% are achieved by using SCFL configuration. The developed IC operates stably from 10 to 60°C ambient temperature over a supply voltage fluctuation of more than 2 V. 相似文献
112.
N. Takada T. Nakano K. Sasaki 《Applied Physics A: Materials Science & Processing》2010,101(2):255-258
It is well known that a crater is formed on the target surface by the irradiation of intense laser pulses in laser ablation.
In this work, we report that additional pits are formed on the bottom surface of the ablation crater due to the collapse of
a cavitation bubble in liquid-phase laser ablation. We observed the formation of several cavitation-induced pits when the
fluence of the laser pulse used for ablation was approximately 5 J/cm2. The number of cavitation-induced pits decreased with the laser fluence, and we observed one or two cavitation-induced pits
when the laser fluence was higher than 10 J/cm2. In addition, we examined the influence of the liquid temperature on the formation of cavitation-induced pits. The collapse
of the cavitation bubble was not observed when the liquid temperature was close to the boiling temperature, and in this case,
we found no cavitation-induced pits on the bottom surface of the ablation crater. This experimental result was discussed by
considering the cavitation parameter. 相似文献
113.
Fukui K Takada Y Sumiyoshi T Imai T Takahashi K 《The journal of physical chemistry. B》2006,110(32):16111-16116
The fragmentation of peptides and oligosaccharides in the gas phase was investigated by means of electrospray ionization Fourier transform ion cyclotron resonance (FTICR) mass spectrometry coupled with dissociation by a laser-cleavage infrared multiphoton dissociation (IRMPD) technique. In this technique, an IR free-electron laser is used as a tunable source of IR radiation to cause cleavage of the ionized samples introduced into the FTICR cell. The gas-phase IRMPD spectra of protonated peptides (substance P and angiotensin II) and two sodiated oligosaccharides (sialyl Lewis X and lacto-N-fucopentaose III) were obtained over the IR scan range of 5.7-9.5 microm. In the IRMPD spectra for the peptide, fragment ions are observed as y/b-type fragment ions in the range 5.7-7.5 microm, corresponding to cleavage of the backbone of the parent amino acid sequence, whereas the spectra of the oligosaccharides have major peaks in the range 8.4-9.5 microm, corresponding to photoproducts of the B/Y type. 相似文献
114.
Retro-allylation of homoallyl alcohol by rhodium catalysis occurs to generate allylrhodium species. This allylrhodium reacts with aldehydes to give the corresponding secondary alcohols in situ. Isomerization of these alcohols proceeds in the same pots to furnish the corresponding saturated ketones in good yields. [reaction: see text] 相似文献
115.
Kazuto Koike Gen-you Takada Kazuya Fujimoto Shigehiko Sasa Masataka Inoue Mitsuaki Yano 《Physica E: Low-dimensional Systems and Nanostructures》2006,32(1-2):191
Thermal stability of single-crystalline [ZnO]m[Zn0.7Mg0.3O]n multiple quantum wells (MQWs) grown on a-plane sapphire substrates by plasma-assisted molecular beam epitaxy is reported. X-ray diffraction analysis revealed that these MQWs were grown as designed with a fixed Zn0.7Mg0.3O barrier width of and a series of ZnO well widths of . Cathodoluminescence spectra from these MQWs consisted of two major peaks; one was the emission from the bound excitons in Zn0.7Mg0.3O barrier layers, and the other was that from the confined excitons in ZnO well layers. These structural and optical properties were found to be dramatically changed by the ex situ annealing treatments over 700 °C. These changes were presumably due to the onset of phase separation of the Zn0.7Mg0.3O barrier layers with pronounced Mg diffusion toward the ZnO wells. 相似文献
116.
Otsubo K. Matsuda M. Takada K. Okumura S. Ekawa M. Tanaka H. Ide S. Mori K. Yamamoto T. 《Electronics letters》2008,44(10):631-632
Uncooled 25 Gbit/s direct modulation of 1.3 mum DFB lasers is demonstrated. The 150 mum-long semi-insulating buried-heterostructure AIGalnAs quantum-well DFB lasers show clear eye-openings with dynamic extinction ratio of 5 dB up to 70degC. 13 km singlemode-fibre transmission experiments using the devices show low power penalty within 1.3 dB between 25 and 70degC. These characteristics are the first achievement by 1.3 mum directly modulated lasers. 相似文献
117.
Makoto Nakanishi Yukiyasu Matsuno Jun Takada 《Journal of Physics and Chemistry of Solids》2008,69(1):49-54
The influence of composition on the structural ordering and magnetism in the VxNb1+yS2 system has been investigated by X-ray diffraction and magnetic measurements. Stoichiometric V1/3NbS2 did not exhibit the structural ordering of vanadium between the NbS2 layers. In the ordered structure, the vanadium composition deviated from the ideal value of to both higher and lower values, while the niobium composition was in the range of 0.05?y?0.18. Excess niobium, y>0, is thought to play an essential role in the structural ordering in this system. For samples with excess niobium and ordered structures, a magnetic transition was observed at 20-50 K, depending on the composition. The spontaneous magnetization of 3-5×10−3 μB/V atom is thought to be intrinsic to this system. The magnetization curves consisted of a constant and a proportional parts of the magnetic field, which correspond to the spontaneous magnetization and high-field susceptibility, respectively. The magnetization curves and the temperature dependencies of the high-field susceptibility were quite similar to those of the canted antiferromagnetic NiS2. A correlation between the structural and magnetic ordering is suggested. 相似文献
118.
Cellulose - Ionic liquids (ILs) are powerful media for the modification and functionalization of cellulose. This review article discusses the preparation of cellulosic soft and composite materials... 相似文献
119.
Kohei Takada Akikazu Matsumoto 《Journal of polymer science. Part A, Polymer chemistry》2018,56(22):2584-2594
The reversible addition-fragmentation chain transfer polymerization of diisopropyl fumarate (DiPF) was carried out using ethyl 2-[[(dodecylthio)thioxymethyl]thio]-2-methylpropionate (T1) and 1,1′-(1,2-ethanediyl) bis[2-[[(dodecylthio)thioxymethyl]thio]-2-methylpropionate] (T2) as the monofunctional and difunctional chain transfer agents (CTAs) to synthesize poly(diisopropyl fumarate) (PDiPF) with a rigid chain conformation. The obtained PDiPF had a well-controlled molecular weight, molecular weight distribution, and structure of the chain ends. Size exclusion chromatography and NMR measurements revealed an excellent introduction efficiency (84–98%) of the terminal trithiocarbonate group into the polymer chain end. They were available as the monofunctional and difunctional macro-CTAs to synthesize the AB and ABA block copolymers, respectively. While the well-controlled block copolymers were solely obtained by the polymerization of 2-ethylhexyl acrylate as the second monomer in the presence of PDiPF as the macro-CTA, the block copolymerization of DiPF using poly(2-ethylhexyl acrylate) as the macro-CTA failed. The trithiocarbonate group at the chain end was completely removed by the reaction with n-butylamine and it was valid for the improvement of the coloration and other optical properties of the transparent polymers. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 2584–2594 相似文献
120.
Shohei Nakamukai Kentaro Takada Kazuo Furihata Yuji Ise Shigeru Okada Yasuhiro Morii Nobuhiro Yamawaki Tomohiro Takatani Osamu Arakawa Kirk R. Gustafson Shigeki Matsunaga 《Tetrahedron letters》2018,59(26):2532-2536
Stellatolide H (1) was isolated from a deep-sea sponge Discodermia sp. as the cytotoxic constituent. The planar structure of 1 was elucidated on the basis of the NMR spectroscopic and mass spectrometric data. The absolute configurations of the constituent amino acid residues were determined by the Marfey’s method. Stellatolide H (1) is a peptide lactone of the callipeltin class with its N-terminus blocked by 3-hydroxy-6,8-dimethyldeca-(4Z,6E)-dienoic acid (Hdda). 相似文献