全文获取类型
收费全文 | 1065篇 |
免费 | 22篇 |
国内免费 | 10篇 |
专业分类
化学 | 600篇 |
晶体学 | 48篇 |
力学 | 16篇 |
数学 | 53篇 |
物理学 | 380篇 |
出版年
2019年 | 11篇 |
2018年 | 12篇 |
2017年 | 7篇 |
2016年 | 14篇 |
2015年 | 17篇 |
2014年 | 14篇 |
2013年 | 60篇 |
2012年 | 38篇 |
2011年 | 45篇 |
2010年 | 33篇 |
2009年 | 38篇 |
2008年 | 45篇 |
2007年 | 75篇 |
2006年 | 47篇 |
2005年 | 33篇 |
2004年 | 61篇 |
2003年 | 41篇 |
2002年 | 34篇 |
2001年 | 45篇 |
2000年 | 23篇 |
1999年 | 31篇 |
1998年 | 13篇 |
1997年 | 14篇 |
1996年 | 16篇 |
1995年 | 17篇 |
1994年 | 19篇 |
1993年 | 33篇 |
1992年 | 26篇 |
1991年 | 17篇 |
1990年 | 13篇 |
1989年 | 18篇 |
1988年 | 13篇 |
1987年 | 8篇 |
1986年 | 13篇 |
1985年 | 11篇 |
1984年 | 11篇 |
1983年 | 7篇 |
1982年 | 7篇 |
1981年 | 9篇 |
1980年 | 7篇 |
1979年 | 11篇 |
1978年 | 11篇 |
1977年 | 6篇 |
1976年 | 9篇 |
1975年 | 11篇 |
1974年 | 12篇 |
1973年 | 8篇 |
1972年 | 6篇 |
1971年 | 4篇 |
1970年 | 4篇 |
排序方式: 共有1097条查询结果,搜索用时 15 毫秒
31.
A random phase mask is often used for Fourier transform holography to improve its recording and reconstruction characteristics. However, a conventional random phase pattern has the disadvantage of expanding the recording spot, which is caused by the high-resolution phase modulation. Previously, we proposed a random phase pattern that makes the recording spot narrower than the conventional one with maintaining a moderate reconstruction quality. In the present study, we apply the proposed random phase pattern to computer-generated binary holograms and evaluate both the hologram distribution and reconstruction quality in terms of practical holographic memory systems. The results confirm the effectiveness of the random phase in the reconstruction for an elementary data pattern. 相似文献
32.
33.
34.
The effect of CO2 adsorption on the catalytic activity of alkaline earth metal oxides in the title reaction reveals that the number of active (basic) sites follows the order MgO>CaO>SrO>BaO, and the order of base strength is MgO
CO2 , () : MgO>CaO>SrO>BaO, : MgO相似文献
35.
Motohisa Kaneko Akio Matsuyama Chikayoshi Nagata 《Photochemistry and photobiology》1978,27(3):359-361
Abstract. Photodimerization of thymine in aqueous solution in the presence of tyrosine was studied with monochromatic UV irradiation. The total dimer formation was sensitized in the presence of tyrosine. The action spectrum of sensitized total dimer formation has a peak near 280 nm corresponding to the absorption maximum of tyrosine. Triplet quenchers reduced the sensitization substantially. It seems probable that tyrosine-sensitized photodimerization of thymine occurred via triplet-triplet energy transfer from tyrosine to thymine. 相似文献
36.
Ai Ito Takamasa Amaki Ayako Ishii Kazuo Fukuda Ryu Yamasaki Iwao Okamoto 《Tetrahedron letters》2018,59(45):3994-3998
Aromatic amides bearing 2-azulenyl group on the amide nitrogen were synthesized and their structures were investigated. The π-electron density of the N-aryl group was found to influence the cis-trans conformational preferences of these compounds in solution. X-ray crystallography revealed that the plane of the 2-azulenyl ring has a strong tendency to lie coplanar with the amide plane when the azulene group is located on the same side as the amide oxygen atom. 相似文献
37.
We developed a new system for random separation of a single microorganism, such as a living cell and a microbe, in the microfluidic device under the microscope by integrating the laser-trapping force and dielectrophoretic (DEP) force. An arbitrarily selected single microbe could be isolated in a microchannel, despite the presence of a large number of microbes in solution. Once the target microbe is trapped at the focal point of the laser, we can easily realize exclusion of excess microbes around the target by controlling the electric field, while keeping the target trapped by the laser at the focal point. To realize an efficient separation system, we proposed a new separation cell and produced it by microfabrication. Flow speed in the microchannel is adjusted and balanced to realize high-speed and high-purity extraction of the target. Some preliminary experiments are conducted to show the effectiveness. The target is trapped by the laser, transported, and is taken out from the extraction port. Total separation time is less than 20 s. Our method is extremely useful in the pure cultivation of the cell and will be a promising method for biologists in screening useful microbes. 相似文献
38.
39.
Kenji Yamada Masahiko Minoda Takeshi Fukuda Takeaki Miyamoto 《Journal of polymer science. Part A, Polymer chemistry》2001,39(4):459-467
Amphiphilic block and statistical copolymers of vinyl ethers (VEs) with pendant glucose residues were synthesized by the living cationic polymerization of isobutyl VE (IBVE) and a VE carrying 1,2:5,6‐di‐O‐isopropylidene‐D ‐glucose (IpGlcVE), followed by deprotection. The block copolymer was prepared by a two‐stage sequential block copolymerization, whereas the statistical copolymer was obtained by the copolymerization of a mixture of the two monomers. The monomer reactivity ratios estimated with the statistical copolymerization were r1 (IBVE) = 1.65 and r2 (IpGlcVE) = 1.15. The obtained statistical copolymers were nearly uniform with the comonomer composition along the main chain. Both the block and statistical copolymers had narrow molecular weight distributions (weight‐average molecular weight/number‐average molecular weight ∼ 1.1). Gel permeation chromatography, static light scattering, and spin–lattice relaxation time measurements in a selective solvent revealed that the block copolymer formed multimolecular micelles, possibly with a hydrophobic poly(IBVE) core and a glucose‐carrying poly(VE) shell, whereas the statistical copolymer with nearly the same molecular weight and segment composition was molecularly dispersed in solution. The surface properties of the solvent‐cast films of the block and statistical copolymer were also investigated with the contact‐angle measurement. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 459–467, 2001 相似文献
40.
Ryuichi Iemura Tsuneo Kawashima Toshikazu Fukuda Keizo Ito Goro Tsukamoto 《Journal of heterocyclic chemistry》1987,24(1):31-37
Several types of benzimidazole derivatives were prepared and were screened for H 1-antihistaminic activity. Most of the compounds showed potent antihistaminic activity in vitro. Among them 2-[(1-piperazinyl)methyl]-benzimidazoles 14 and 2-[(1-homopiperazinyi)methyl]benzimidazoles 15 exhibited potent activity also in vivo. 相似文献