全文获取类型
收费全文 | 270篇 |
免费 | 5篇 |
专业分类
化学 | 208篇 |
晶体学 | 1篇 |
力学 | 5篇 |
数学 | 27篇 |
物理学 | 34篇 |
出版年
2022年 | 2篇 |
2021年 | 2篇 |
2020年 | 3篇 |
2019年 | 4篇 |
2015年 | 3篇 |
2014年 | 4篇 |
2013年 | 8篇 |
2012年 | 16篇 |
2011年 | 16篇 |
2010年 | 9篇 |
2009年 | 10篇 |
2008年 | 10篇 |
2007年 | 18篇 |
2006年 | 12篇 |
2005年 | 6篇 |
2004年 | 9篇 |
2003年 | 4篇 |
2002年 | 12篇 |
2001年 | 11篇 |
2000年 | 11篇 |
1999年 | 4篇 |
1997年 | 3篇 |
1996年 | 3篇 |
1995年 | 2篇 |
1994年 | 7篇 |
1992年 | 4篇 |
1991年 | 7篇 |
1989年 | 4篇 |
1988年 | 3篇 |
1987年 | 3篇 |
1986年 | 3篇 |
1985年 | 5篇 |
1984年 | 6篇 |
1982年 | 3篇 |
1981年 | 4篇 |
1980年 | 4篇 |
1979年 | 7篇 |
1978年 | 3篇 |
1974年 | 2篇 |
1973年 | 3篇 |
1971年 | 2篇 |
1968年 | 2篇 |
1966年 | 2篇 |
1965年 | 1篇 |
1963年 | 1篇 |
1962年 | 2篇 |
1933年 | 1篇 |
1930年 | 2篇 |
1929年 | 1篇 |
1928年 | 1篇 |
排序方式: 共有275条查询结果,搜索用时 9 毫秒
61.
62.
Dynamic wavelength shifts of a monolithic, two-beam laser diode for a two-beam optical head in optical disk drives were analyzed with a streak camera system. The wavelength shift did not exceed 3 nm for the recording beam which was operated in a series of pulses, and the reproducing beam which was operated continuously showed no shift. The focusing characteristics on the basis of the wavelength shift and specifications of the optical head were also calculated. The dynamic displacement of the focal points caused by the wavelength shifts was so small as compared with the depth of focus in the optical head that the recording and reproducing characteristics were hardly influenced. 相似文献
63.
Keiko Takahashi Kenjiro Hattori 《Journal of inclusion phenomena and macrocyclic chemistry》1994,17(1):1-24
Cyclodextrins have great potential for exploitation as a useful tool for asymmetric induction. Many kinds of asymmetric reaction have been achieved in the presence of cyclodextrin under various conditions such as the solid phase, heterogeneous suspension or homogeneous aqueous or organic solution. Complexation is essential for asymmetric induction. What is necessary to improve CDs for greater asymmetric induction? 相似文献
64.
It is possible to synthesize poly(N-substituted maleimide) by using a chiral complex consisting of a zinc and N-diphenylmethyl-1-benzyl-2-pyrrolidinoethanamine (DPhBP). The optical specific rotations [α]43525 in obtained polymers depend on the chirality of ligands in the catalysts. In the present study, density functional theory (DFT) calculations were adopted to investigate the polymerization mechanism in detail. The bulky diphenylmethyl group in the chiral ligand is effective to enhance the formation of the product in the initiation reaction. The geometry related to the pyrrolidine ring of the chiral ligand in the Zn catalyst is responsible for determining the configuration of polymers. It was also confirmed that the bulky substituent on the N atom of the N-substituted maleimide is another factor for obtaining polymers with high [α]43525. 相似文献
65.
Factors controlling electroosmotic flow in open-tubular capillaries in electrokinetic chromatography
S. Terabe H. Utsumi K. Otsuka T. Ando T. Inomata S. Kuze Y. Hanaoka 《Journal of separation science》1986,9(11):666-670
Effects of pH, concentration of sodium dodecyl sulfate (SDS), additives, and coatings of polymers on the inner wall of fused silica tubing on electrokinetic migration were investigated with SDS solutions. The increase in SDS concentrations caused a substantial increase of the electrophoretic velocity of the SDS micelle but little affected the electroosmotic velocity veo under a constant applied voltage. No significant change in veo was observed either when the pH of the solution was varied from 5.5 to 9 or when additives such as hydroxypropyl cellulose were employed. Compared with an uncoated tube, electroosmosis became stronger in a fused silica tube coated with methyl silicone but weaker in one coated with polyethylene glycol 20M. 相似文献
66.
Asymmetric dipolar cycloadditions of a nitrile oxide to the acrylamide derivatives of two new chiral auxiliaries, (R)-2,2-dimethyl-4-phenyloxazolidines and (S,S)-2,2-dimethyl-4,5-diphenylimidazolidine, show satisfactorily high diastereoselectivities (up to 91%). 相似文献
67.
Hideyoshi Abe Akira Kenmoku Noriyuki Yamaguch Kenjiro Hattori 《Journal of inclusion phenomena and macrocyclic chemistry》2002,44(1-4):39-47
Bi-galactose-branched cyclodextrins (Bi-Gal-CDs)(1–6) having different spacer arm lengths between two terminal galactoses were foundto have the optimum length for association with PNA lectin. Also, the inclusioninteraction of the drug depended on the length of the spacer arms. The dual association of thesecompounds was quantitatively evaluated by SPR and compared to the other oligosaccharide-branchedCDs (Scheme 1). The number and the length of the spacer arm are important for theassociation both with the lectin and drug for the purpose of targeting drug-delivery systems.The association constants K of bi-Gal-CD (2) with rat liver cells showed a 60 timeshigher association than with PNA. Direct evidence of the association between PNA andbi-Gal-CD (2) was characterized by AFM observations. The results obtained strongly suggested a method to find a new design for the targeting drug carrier. In order toincrease the association with the cell, a sufficient spacer arm length is necessary for the effectivedual recognition of the oligosaccharide-CDs. In order to increase the inclusion of thedrug, the CD structure of a multi-saccharide branch is necessary. 相似文献
68.
Huajing Gao Yukio Isobe Kenjiro Onimura Tsutomu Oishi 《Journal of polymer science. Part A, Polymer chemistry》2007,45(16):3722-3738
A kind of N‐substituted maleimide (RMI), chiral (S)‐N‐maleoyl‐L ‐leucine propargyl ester ((S)‐PLMI) with a specific rotation of [α]435 = ?27.5° was successfully synthesized from maleic anhydride, L ‐leucine, and propargyl alcohol. (S)‐PLMI was polymerized by three polymerization methods to obtain the corresponding optically active polymers. Asymmetric anionic, radical, and transition‐metal‐catalyzed polymerizations were carried out using organometal/chiral ligands, 2,2′‐azobisisobutyronitrile (AIBN) and (bicyclo [2,2,1]hepta‐2,5‐diene) chloro rhodium (I) dimer ([Rh(nbd) Cl]2), respectively. Poly((S)‐PLMI) obtained by [Rh(nbd)Cl]2 in DMF showed the highest specific rotation of ?280.6°. Chiroptical properties and structures of the polymers obtained were investigated by GPC, CD, IR, and NMR measurements. Two types of poly((S)‐PLMI)‐bonded‐silica gels as the chiral stationary phase (CSP) were prepared for high‐performance liquid chromatography (HPLC). Their optical resolution abilities were also elucidated. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3722–3738, 2007 相似文献
69.
Masashige Onoda Kenjiro Takao Tomohiro Ikeda 《Physica C: Superconductivity and its Applications》2009,469(4):162-167
Nuclear magnetic resonance and relaxation measurements of the 59Co nuclei for the well-defined field-aligned powder of the triangular lattice superconductor NaxCoO2 · yH2O with a nearly optimal composition for the transition temperature Tc have been performed. Detailed analyses indicate that the Knight shifts for the directions parallel and perpendicular to the CoO2 plane and the spin-lattice relaxation rates, taken by making an inevitable deterioration of specimen minimal, are significantly smaller than most of the data reported to date, and that this compound is classified into one of the unconventional spin-singlet superconductors as suggested by recent works for single crystals with a lower Tc. A small enhancement of two-dimensional antiferromagnetic spin correlations at some nonzero wave vector may emerge near Tc. 相似文献