全文获取类型
收费全文 | 1441篇 |
免费 | 74篇 |
国内免费 | 6篇 |
专业分类
化学 | 1187篇 |
晶体学 | 16篇 |
力学 | 30篇 |
数学 | 32篇 |
物理学 | 256篇 |
出版年
2023年 | 11篇 |
2022年 | 12篇 |
2021年 | 17篇 |
2020年 | 33篇 |
2019年 | 41篇 |
2018年 | 18篇 |
2017年 | 14篇 |
2016年 | 37篇 |
2015年 | 30篇 |
2014年 | 30篇 |
2013年 | 84篇 |
2012年 | 73篇 |
2011年 | 75篇 |
2010年 | 37篇 |
2009年 | 43篇 |
2008年 | 60篇 |
2007年 | 56篇 |
2006年 | 65篇 |
2005年 | 54篇 |
2004年 | 52篇 |
2003年 | 48篇 |
2002年 | 34篇 |
2001年 | 50篇 |
2000年 | 30篇 |
1999年 | 32篇 |
1998年 | 12篇 |
1997年 | 13篇 |
1996年 | 24篇 |
1995年 | 8篇 |
1994年 | 23篇 |
1993年 | 16篇 |
1992年 | 42篇 |
1991年 | 22篇 |
1990年 | 24篇 |
1989年 | 23篇 |
1988年 | 26篇 |
1987年 | 24篇 |
1986年 | 19篇 |
1985年 | 25篇 |
1984年 | 27篇 |
1983年 | 15篇 |
1982年 | 13篇 |
1979年 | 10篇 |
1977年 | 11篇 |
1975年 | 11篇 |
1974年 | 8篇 |
1973年 | 9篇 |
1964年 | 9篇 |
1962年 | 7篇 |
1960年 | 7篇 |
排序方式: 共有1521条查询结果,搜索用时 93 毫秒
91.
Kenji Kinashi Yuki Kambe Masahiro Misaki Yasuko Koshiba Kenji Ishida Yasukiyo Ueda 《Journal of polymer science. Part A, Polymer chemistry》2012,50(24):5107-5114
Three types of bi‐functionalized copolymers ( P1FAz , P2FAz , and P3FAz ) with different numbers of fluorene units and an azobenzene unit were synthesized and characterized using UV–vis and polarized absorption spectroanalysis. The trans‐cis photoisomerization was conformed under 400 nm light irradiation for all copolymers in chloroform. However, in the film state, only the trans‐cis photoisomerization occurred by mono‐fluorene attached copolymer poly[(9,9‐di‐n‐octylfluorenyl‐2,7‐diyl)‐alt‐4,4′‐azobenzene)] ( P1FAz ). Photo‐induced alignment was achieved using the P1FAz film after irradiation with linear polarized 400 nm light and subsequent annealing at 60 °C. Surface orientation of a spin‐coating film of poly(9,9‐didodecylfluorene) ( F12 ) was achieved using the photo‐induced alignment layer of the P1FAz film after annealing at 90 °C. The photo‐induced alignment layer of P1FAz has potential application to the surface orientation technique for appropriate polymers, which will be useful for the fabrication of optoelectronics devices. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 相似文献
92.
93.
Sekiguchi A Ishida Y Fukaya N Ichinohe M Takagi N Nagase S 《Journal of the American Chemical Society》2002,124(7):1158-1159
Dark red crystals of the halogen-substituted cyclotrigermenes [(tBu3Si)3Ge3X; X = Cl, Br, I] were obtained in good yields by the reaction of [(tBu3Si)3Ge3]+.TTFPB- (TTFPB- = tetrakis(2,3,5,6-tetrafluorophenyl)borate) with potassium halides (KCl, KBr, or KI) in diethyl ether. The crystal structures of the halogen-substituted cyclotrigermenes reveal a cis-bent Ge=Ge double bond, caused by the introduction of the electronegative halogen atom on the sp3 germanium atom of cyclotrigermene. In solution, an intramolecular halogen migration over the three-membered ring skeleton was observed. Facial stereoselectivity in the Diels-Alder reaction of new cyclotrigermenes with 2,3-dimethyl-1,3-butadiene is also reported. 相似文献
94.
Ishida K Ozaki D Kamatsuka T Tou H Kyogaku M Kitaoka Y Tateiwa N Sato NK Aso N Geibel C Steglich F 《Physical review letters》2002,89(3):037002
We report (27)Al Knight shift ( (27)K) measurement on a single-crystal UNi(2)Al(3) that reveals a coexistence of superconductivity and a spin-density-wave (SDW) type of magnetic ordering ( T(SDW) = 4.5 K). The spin part of (27)K, (27)K(s), does not change down to 50 mK across the superconducting (SC) transition temperature T(c) approximately 0.9 K. In contrast with the isostructural compound UPd(2)Al(3) ( T(c) approximately 2 K), which was identified to be a spin-singlet d-wave superconductor, the behavior of (27)K strongly supports that UNi(2)Al(3) , like UPt(3) and Sr(2)RuO(4), belongs to a class of spin-triplet SC pairing state superconductors. 相似文献
95.
Dielectric measurements were performed on montmorillonite, allophane, and imogolite suspensions under various pH conditions, using time domain reflectometry over the frequency range 10 kHz-20 GHz. A dielectric relaxation peak due to bound water could be observed for all the clays. Allophane has two peaks, indicating that its peaks are very similar to those of silica-alumina gels. Although imogolite has a similar chemical composition, only one peak was found. The relaxation strength of montmorillonite is greater than that of the other two clays. For all the clays, the relaxation strength depended on the pH. A change in the relaxation strength according to a change in pH is explained in terms of the different network structures of the clay particles. It is suggested that bound water influences the network structure formation. In montmorillonite, a great relaxation process detected at low frequency is caused by surface polarization of counterions. The change in measure of the structural unit with the pH, identified from Schwartz's theory, has a tendency similar to that postulated by other experimental techniques, and surface charge densities identified are close to those estimated from CEC. Copyright 1999 Academic Press. 相似文献
96.
A new type of x-ray spectroscopy is proposed which can detect the thermal-motion-induced distortions of atomic electronic
states in crystals. It is shown that those distortions can cause extra Bragg reflections (so-called forbidden reflections)
and that their intensity should grow with increasing temperature. The reason is that the thermal displacements, which change
the symmetry of atomic environment, can modify the tensor amplitude of x-ray resonant scattering. In the first approximation,
the structure factor of extra reflections is proportional to the reflection vector H and to the mean-square thermal displacement
for optical phonons. It is demonstrated that the forbidden resonant reflections, observed recently in Ge, could be caused
by the thermal motion.
Pis’ma Zh. éksp. Teor. Fiz. 69, No. 12, 885–889 (25 June 1999)
Published in English in the original Russian journal. Edited by Steve Torstveit. 相似文献
97.
98.
The refractive index of SiO2-P2O5 glass prepared by a modified chemical vapor deposition method is measured using an interference microscope. It is found that the refractive index in bulk form increases linearly at 9.5×10-4 (mol.%)-1 as the P2O5 concentration increases. It is also found that quenching at extremely high speed reduces the refractive index over 2 mol.% P2O5. The wavelength dispersion of the refractive index dn/dλ is constant up to 5 mol.% P2O5 producing a refractive index difference of 5×10-3 compared with fused silica. Consequently, this glass materials is thought to be suitable for wide band-width optical fiber applications. 相似文献
99.
Tomoshige Morita Takeshi Hamada Koji Ishida 《Fresenius' Journal of Analytical Chemistry》1981,309(5):377-379
Summary The TLC behaviour of Rh(III), Ir(III) and Ir(IV) has been investigated in the two systems consisting of DEAE-cellulose or ECTEOLA-cellulose and 5 M HCl media containing H2O2. These systems, especially in combination with a simple chemical pretreatment of samples (with LiCl, HCl and H2O2), can effectively be applied to the complete separation of mixtures of Rh(III) and Ir(III) or Ir(IV) in a wide range of ratios and amounts (Rh: Ir=1100 to 1001).
Dünnschicht-chromatographische Trennung von Rhodium(III) und Iridium(III, IV) durch Anionenaustausch
Zusammenfassung Das dünnschicht-chromatographische Verhalten von Rh(III), Ir(III) und Ir(IV) wurde in H2O2-haltiger 5 M salzsaurer Lösung auf DEAE-sowie ECTEOLA-Cellulose untersucht. In Kombination mit einer einfachen chemischen Vorbehandlung der Probe (mit LiCl, HCl, H2O2) kann eine wirkungsvolle Trennung von Rh(III) und Ir(III) oder Ir(IV) über einen weiten Konzentrationsbereich erzielt werden (Rh: Ir=1100 bis 1001).相似文献
100.