全文获取类型
收费全文 | 458篇 |
免费 | 20篇 |
国内免费 | 20篇 |
专业分类
化学 | 243篇 |
晶体学 | 5篇 |
力学 | 37篇 |
数学 | 70篇 |
物理学 | 143篇 |
出版年
2019年 | 10篇 |
2018年 | 6篇 |
2017年 | 6篇 |
2016年 | 13篇 |
2014年 | 15篇 |
2013年 | 19篇 |
2012年 | 14篇 |
2011年 | 12篇 |
2010年 | 13篇 |
2009年 | 15篇 |
2008年 | 13篇 |
2007年 | 13篇 |
2006年 | 15篇 |
2005年 | 12篇 |
2004年 | 17篇 |
2003年 | 13篇 |
2002年 | 18篇 |
2001年 | 19篇 |
2000年 | 14篇 |
1999年 | 10篇 |
1998年 | 5篇 |
1997年 | 6篇 |
1996年 | 7篇 |
1995年 | 7篇 |
1991年 | 6篇 |
1990年 | 6篇 |
1989年 | 9篇 |
1988年 | 6篇 |
1987年 | 4篇 |
1986年 | 7篇 |
1982年 | 6篇 |
1981年 | 4篇 |
1979年 | 8篇 |
1978年 | 8篇 |
1977年 | 4篇 |
1976年 | 10篇 |
1975年 | 4篇 |
1974年 | 5篇 |
1973年 | 4篇 |
1971年 | 11篇 |
1970年 | 12篇 |
1969年 | 11篇 |
1968年 | 8篇 |
1967年 | 4篇 |
1966年 | 5篇 |
1965年 | 5篇 |
1964年 | 4篇 |
1960年 | 4篇 |
1958年 | 4篇 |
1957年 | 4篇 |
排序方式: 共有498条查询结果,搜索用时 328 毫秒
101.
G. V. Lavrova V. G. Ponomareva I. V. Ponomarenko S. D. Kirik N. F. Uvarov 《Russian Journal of Electrochemistry》2014,50(7):603-612
Composite proton-conducting electrolytes are synthesized based on H4SiW12O40 · xH2O, CsHSO4, (CsH2PO4)0.9(CsHSO4)0.1 and mesoporous matrices SBA-15 and MCM-41 and their transport and structural characteristics are studied. Composites based on silicotungstic acid demonstrate the conductivity from ~10?3 to 10?4 S/cm in the temperature range of 25–140°C at the increased partial pressure of water vapor. The conductivity of systems CsHSO4-SBA-15 (at T = 140–200°C) and (CsH2PO4)0.9(CsHSO4)0.1-SBA-15 (at T = 200–230°C) reaches 10?2 S/cm and is independent of humidity. The electrolytes studied are promising as proton-exchange membranes of fuel cells operating at low and medium temperatures. 相似文献
102.
A. D. Garnovskii A. S. Burlov K. A. Lysenko D. A. Garnovskii I. G. Borodkina A. G. Ponomarenko G. G. Chigarenko S. A. Nikolaevskii V. I. Minkin 《Russian Journal of Coordination Chemistry》2009,35(2):120-127
N-Alkylsalicylideneimines and their complexes with 3d metals were obtained by chemical (from metal salts) and electrochemical methods (from metals in the zero oxidation state). The compounds obtained were characterized by IR and 1H NMR spectroscopy and X-ray diffraction analysis. According to crystallographic data, nickel bis(chelate) exists in the trans-planar configuration. A friction test revealed that the tribotechnical characteristics of lubricating formulations are substantially enhanced in the presence of N-alkylsalicylideneiminates. 相似文献
103.
Vadim I. Ponomarenko Dmitrii V. Krupenya Elena V. Grachova Vladimir A. Gindin Stanislav I. Selivanov Igor O. Koshevoy Sergey P. Tunik Prof. Dr. Matti Haukka Jouni Pursiainen Päivi Pirilä 《无机化学与普通化学杂志》2009,635(15):2515-2526
A novel chiral phosphane (S)‐2‐(4‐isopropyl‐2‐oxazoline‐2‐yl)phenyl‐di‐N‐pyrrolylphosphane (S‐PyrPOx) based on asymmetric oxazoline ring has been prepared and characterised. Reaction of this ligand and its phenyl‐substituted analogue (S‐PhPOx) with H4Ru4(CO)12 and H3RhOs3(CO)12 gave substituted derivatives H4Ru4(CO)10(1,1‐PhPOx) ( 2 ), H4Ru4(CO)10(1,1‐PyrPOx) ( 3 ), and H3RhOs3(CO)10(1,1‐PyrPOx) ( 4 ), which were structurally characterised by X‐ray crystallography in solid state and by a variety of multinuclear NMR spectroscopic measurements in solution. In all studied clusters the coordinated ligands form five‐membered chelate rings through phosphorus and nitrogen atoms of oxazoline moiety to afford a novel chiral center associated with the substituted metal atom. The substitution reactions demonstrate extremely high stereoselectivity, which results in formation of only one diastereomer in all three cases to give S,S isomer in 2 and S,R isomer in 3 and 4 . 相似文献
104.
V.A. Ponomarenko E.L. Berman A.M. Sakharov Z.N. Nysenko 《European Polymer Journal》1981,17(10):1111-1114
The results of studying the kinetic isotope effect of cationic polymerization of some oxygen-containing heterocycles are summarized. The use of this method made it possible to establish the oxonium mechanism of chain propagation and the existence of the step of preliminary monomer coordination on an active centre, preceding the polymeric chain propagation step. 相似文献
105.
The TDDFT method is first applied in a series of tetra-nuclear transition metal clusters studies for nonlinear optical properties. The results indicate that the charge transfer inside the metal core [MCu3X4] (M=W, Mo; X=S, O, Cl, Se, Br) makes contribution to the optical nonlinearity. It is possible to enhance the hyperpolarizability by substituting the ligands of the clusters. 相似文献
106.
Yu-Ming ZHENG Hong-Min LIU Ben-Hao SA Zhong-Dao LU Zhong-Qi WANG Xiao-Ze ZHANG 《理论物理通讯》1993,19(1):71-74
A simple Monte Carlo simulation and even a partition method can be used to reproduce quite well the power law behavior between the factorial moment and the charge interval of fragment charge distributions from the multifragmentation of 197Au nucleus bombarding emulsion at~1 GeV/nucleon. This indicates that the above power law seems not to be a unique precursor of the intermittent behavior in nuclear multifragmentations. 相似文献
107.
The charge dispersion of fragments in high energy p+Cu,Kr and Xe reactions are calculated by statistical model and Monte Carlo technique.The corresponding data are reproduced quite well.It is shown that the charge dispersions are all nearly gaussian.The mass dependence of the most probable fragment charge reflects the rest target memory effect. 相似文献
108.
Following the method developed by the authors,recently,the equation of state of hot nuclei(238U in concrete) before break-up was investigated numerically.The isotherms are drawn in the plan of the general pressure P versus volume VRT. They are similar to those of Van der Waals gas.The critical temperature of phase transition should correspond to the isotherm with one turning point only.It turns out that the data of mass yield distribution can be reproduced by many pairs of parameters T and VRT (freeze-out temperature and freeze-out volume) varying in certain range.For each isotherm (each T),the data are always best reproduced by the value of VRT located at the maximum general pressure within two phases coexistence region. 相似文献
109.
LU ZhongDao SA BenHao Masanori Matsuda Junichi Nagata Atsushi Nakamura Osamu Miyamura 《中国物理C(英文版)》2000,24(8):743-747
The Λ multiplicity and Λ/p ratio are studied by hadron transportation-string fragmentation model in relativistic heavy ion collisions. Firstly, the dependence of Λ multiplicity and Λ/p ratio on the system size and the collision centrality is studied. It shows that the Λ and p multiplicities go up as the increase of system size and the increase of collision centrality. However, their ratio keeps almost a constant. The effect of Λ annihilation cross section to Λ multiplicity and Λ/p ratio is also studied. It is found that this effect is weak: Λ multiplicity and Λ/p ratio have a little amount of increase by the decrease of Λ annihilation cross section. Even the cross section is down to zero, Λ/p ratio is only 1.2 in 200A GeV AuAu head on collision. The Λ/p ratio is obtained to be 0.28 in pp collision, lying in the range of experimental data:0.2—0.3. It is also obtained that the ratio in AA collisions is 3—5 times of that in pp collision. 相似文献
110.