全文获取类型
收费全文 | 2094篇 |
免费 | 43篇 |
国内免费 | 5篇 |
专业分类
化学 | 1506篇 |
晶体学 | 34篇 |
力学 | 20篇 |
数学 | 90篇 |
物理学 | 492篇 |
出版年
2021年 | 18篇 |
2020年 | 15篇 |
2019年 | 20篇 |
2018年 | 25篇 |
2017年 | 22篇 |
2016年 | 36篇 |
2015年 | 26篇 |
2014年 | 29篇 |
2013年 | 101篇 |
2012年 | 86篇 |
2011年 | 98篇 |
2010年 | 66篇 |
2009年 | 55篇 |
2008年 | 107篇 |
2007年 | 110篇 |
2006年 | 118篇 |
2005年 | 117篇 |
2004年 | 107篇 |
2003年 | 72篇 |
2002年 | 68篇 |
2001年 | 64篇 |
2000年 | 43篇 |
1999年 | 35篇 |
1998年 | 20篇 |
1997年 | 28篇 |
1996年 | 40篇 |
1995年 | 27篇 |
1994年 | 22篇 |
1993年 | 19篇 |
1992年 | 30篇 |
1991年 | 29篇 |
1990年 | 24篇 |
1989年 | 18篇 |
1988年 | 27篇 |
1987年 | 24篇 |
1986年 | 23篇 |
1985年 | 35篇 |
1984年 | 38篇 |
1983年 | 35篇 |
1982年 | 21篇 |
1981年 | 28篇 |
1980年 | 17篇 |
1979年 | 28篇 |
1978年 | 19篇 |
1977年 | 20篇 |
1976年 | 21篇 |
1975年 | 20篇 |
1974年 | 11篇 |
1973年 | 10篇 |
1967年 | 11篇 |
排序方式: 共有2142条查询结果,搜索用时 15 毫秒
151.
When certain trivalent rare-earth ions (Ln's) are co-doped in CaGa2S4:Mn2+ as sensitizers, the Mn red emission of the compound is strikingly enhanced. In this work, efficiency of each lanthanide is studied. The best efficiencies are achieved with La3+-, Pr3+-, and Tb3+- co-doped compounds, for each of which the effects of concentrations of the co-doped ions on the Mn2+ emission are investigated. The energy-transfer mechanisms and the location of electronic energy levels of both the trivalent and the divalent lanthanides in the energy band gap of the host material are discussed. Depending on Ln's, charge transfer or cross-relaxation should be taken into account. 相似文献
152.
Naoyoshi Komatsu Keiko Masumoto Hidemitsu Aoki Chiharu Kimura Takashi Sugino 《Applied Surface Science》2010,256(6):1803-8310
Synthesis of Si-added aluminum oxide (AlSiO) films is attempted as an insulating film with both a wide bandgap and a high dielectric constant. Electrical characteristics of AlSiO films are investigated. Leakage current of the AlO film is suppressed by Si addition and is minimized with Si composition ratio of 12%. Capacitance versus voltage (C-V) measurements are carried out for Au/AlSiO/Si MIS structure. Both flat band shift and hysteresis of the C-V characteristics are suppressed by Si addition. A low leakage current is demonstrated for Au/AlSiO/n-SiC MIS structure. 相似文献
153.
154.
Suzuki M Yumoto M Kimura M Shirai H Hanabusa K 《Chemical communications (Cambridge, England)》2002,(8):884-885
New L-lysine derivatives with a positively charged terminal can gel water below 1 wt%; particularly, 1a and 2a form a hydrogel at 0.3 wt% corresponding to approximately 12,300 and 12,500 waters/gelator molecule, respectively. 相似文献
155.
Koike Y Metoki N Haga Y McEwen KA Kohgi M Yamamoto R Aso N Tateiwa N Komatsubara T Kimura N Aoki H 《Physical review letters》2002,89(7):077202
The magnetic structure of the localized-5f uranium intermetallic compound U3Pd20Si6 has been determined by means of a neutron diffraction experiment. Our data demonstrate that this compound has a collinear coupling of the sublattice ordering of the uranium spins on the 4a and 8c sites. We conclude that higher-order exchange and/or quadrupole interactions are necessary to stabilize this unique collinear structure. We discovered a new type of spin-flop transition against the uniaxial anisotropy induced by this collinear coupling. 相似文献
156.
Michio Kimura Stanley H. Simonsen Steven R. Caldwell Gary E. Martin 《Journal of heterocyclic chemistry》1981,18(3):469-473
The single crystal X-ray diffraction structure of 2-(2′-pyridylthio)-3-nitropyridine is reported. A non-bonded interaction was observed between the sulfur atom and one of the oxygen atoms of the nitro group with an interatomic distance of 2.678 A. Examination of the molecule's behavior in solution by 13C-nmr spin-lattice (T1) relaxation measurements showed the non-nitro bearing pyridyl ring to reorient anisotropically about the C2′-C5′ bond axis. In contrast, the nitro substituted pyridine ring did not appear to exhibit anisotropic reorientation about the corresponding C2-C5 bond axis. Rather, approximately equivalent relaxation times were noted for all protonated ring carbons, indicating that the relaxations of this portion of the molecule were governed by the overall isotropic reorientation of the system. Based on these observations, it was concluded that the intramolecular sulfur-nitro interaction also operates in the solution state and is sufficiently strong to prevent free rotation of the substituted portion of the molecule about the C2-S bond axis. 相似文献
157.
Doubly differential cross sections, in energy and angle, are reported for the electron transfer reaction between potassium and nitrogen dioxide in a crossed beam apparatus at relative collision energies between 2.7 and 30.8 eV. The formation of NO?2 in its ground 1A1 and excited 3B1 state has been observed. Theoretical consideration of these processes indicates that bond bending during the collision has a stronger influence on ion-pair formation than bond stretching. At the lower collision energies most of the excess energy is converted into internal energy of NO?2. 相似文献
158.
H. Kimura 《Physics letters. A》1974,47(2):173-174
An expression for the free energy of nematic liquid crystals is given by taking account of the excluded volume effects as well as dispersion forces. The dependence of nematic order on concentration and/or shape of molecules is discussed. 相似文献
159.
160.