全文获取类型
收费全文 | 192篇 |
免费 | 13篇 |
国内免费 | 4篇 |
专业分类
化学 | 130篇 |
晶体学 | 1篇 |
力学 | 2篇 |
数学 | 38篇 |
物理学 | 38篇 |
出版年
2022年 | 1篇 |
2021年 | 2篇 |
2020年 | 3篇 |
2019年 | 5篇 |
2018年 | 11篇 |
2017年 | 5篇 |
2016年 | 11篇 |
2015年 | 6篇 |
2014年 | 9篇 |
2013年 | 12篇 |
2012年 | 8篇 |
2011年 | 8篇 |
2010年 | 7篇 |
2009年 | 6篇 |
2008年 | 21篇 |
2007年 | 7篇 |
2006年 | 6篇 |
2005年 | 10篇 |
2004年 | 6篇 |
2003年 | 3篇 |
2002年 | 6篇 |
2001年 | 5篇 |
2000年 | 4篇 |
1999年 | 6篇 |
1998年 | 6篇 |
1996年 | 3篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1986年 | 3篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1974年 | 2篇 |
1973年 | 3篇 |
1972年 | 3篇 |
1971年 | 1篇 |
1970年 | 2篇 |
1967年 | 1篇 |
1964年 | 1篇 |
1961年 | 3篇 |
1960年 | 1篇 |
1957年 | 1篇 |
排序方式: 共有209条查询结果,搜索用时 15 毫秒
1.
V. Z. Kasimov O. V. Ushakova Yu. P. Khomenko 《Journal of Applied Mechanics and Technical Physics》2003,44(5):612-619
An improved procedure for modeling the operation of a light-gas gun is proposed. The motion of working bodies in both the firing chamber and the light-gas chamber is studied within the framework of the mechanics of heterogeneous media. The problem of barrel heating taking into account its melting and removal of thermal ablation products into the medium inside the bore is solved in a coupled formulation. Heat and mass transfer and friction on the barrel surface are calculated using empirical dependences. The deformable piston is considered compressible and elastoviscoplastic. Allowance is made for the presence of a clearance between the lateral surface of the piston and the barrel bore walls and the associated gas flow between the firing and the light-gas chamber. Calculation results are given. 相似文献
2.
Richard P. Kent IV 《Geometriae Dedicata》2004,106(1):145-159
We answer a question of J. Anderson's by producing infinitely many commensurability classes of fibered hyperbolic 3-manifolds whose fundamental groups contain subgroups that are locally free and not free. These manifolds are obtained by performing 0–surgery on a collection of knots with the same properties. 相似文献
3.
4.
5.
6.
V. Yu. Orlov L. E. Gusel'nikov N. S. Nametkin R. L. Ushakova 《Journal of mass spectrometry : JMS》1972,6(3):309-316
The mass spectra of 1,1-dimethyl-1-silacyclobutane (I—as reported by Cherniak et al.),6, 1,1-dimethyl-1-germacyclobutane (II), 1,1,2,2-tetramethyl-1,2-disilacyclopentane (III) and 1,1,2,2-tetramethyl-1,2-digermacyclopentane (IV) are compared and some correlations between electron-impact fragmentation and thermal decomposition are derived. The mass spectra of the germanium compounds with respect to the silicone compounds are enriched by light fragment ions and exhibit lower intensities of odd-electron ions. The composition of some ions and apparently of neutral fragments coincides with that of the unstable intermediates which are suggested in the thermal decomposition mechanism of some related compounds. The loss of C2H4 is more characteristic under electron-impact as well as in thermal decomposition of Si-compounds, while C3H6 is preferable eliminated by the Ge-compounds. 相似文献
7.
L. A. Novokshonova N. Yu. Kovaleva T. M. Ushakova I. N. Meshkova V. G. Krasheninnikov T. A. Ladygina I. O. Leipunskii A. N. Zhigach M. L. Kuskov 《Kinetics and Catalysis》2005,46(6):853-860
The heterogenized reaction products of the partial hydrolysis of the organoaluminum compounds AlMe3 and Al(i-Bu)3 with water as a constituent of highly hydrated supports, zeolite (ZSM-5-H2O) and montmorillonite (MMT-H2O), have been synthesized. The thermal degradation of the resulting heterogenized methylalumoxane compound and methylalumoxane (MAO) in a solid state is studied by temperature-programmed desorption with the mass-spectrometric analysis of liberated gaseous products, and the structural identity of the above compounds is found. Alkylalumoxanes prepared immediately on the surface of a support form heterogenized complexes with the metallocenes Cp2ZrCl2 and Et(Ind)2ZrCl2. These heterogenized complexes exhibit high activity in the reactions of ethylene and propylene polymerization. For this reason, MAO can be replaced by AlMe3 or Al(i-Bu)3 and the additional introduction of MAO or another alkylaluminum for zirconocene activation is unnecessary. It has been found that, upon the immobilization of commercial MAO on dehydrated SiO2, the MAO molecule loses a portion of its most reactive methyl groups and, as a result of this, becomes incapable of activating metallocenes. 相似文献
8.
E. N. Ushakova O. V Konyushko A. A. Glazkov S. P. Krukovsky 《Russian Chemical Bulletin》1996,45(6):1501-1503
A series of 1,1-dihydroperfluorooxaalkan-1-ols and ,,,-tetrahydroperfluorooxaalkanediols has been synthesized. Some tercphthalates were synthesized by the reaction of these alcohols and diols with terephthaloyl chloride.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1573–1576, June, 1996. 相似文献
9.
V. I. Kelarev R. A. Karakhanov M. Bellul' R. L. Ushakova A. I. Mikaya 《Chemistry of Heterocyclic Compounds》1988,24(5):550-555
N-Substituted 2,4-diamino-6-pyridyl-sym-triazines were synthesized by cyclocondensation of pyridinecarboxylic acid esters with biguanides. 4,6-Disubstituted 2-amino-sym-triazines containing pyridyl residues were obtained by the reaction of pyridinecarboxylic acid nitriles with guanidine or of pyridinecarboxylic acid esters with N-imidoylguanidines. Aminotriazines of this type are also formed in the condensation of N-acylguanidines with nitriles or imino esters. The general principles of the fragmentation of 2-amino-4-dialkylamino-6-pyridyl-sym-triazines under the influence of electron impact were established.See [1] for Communication 6.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 674–680, May, 1988. 相似文献
10.
L. A. Novokshonova T. M. Ushakova V. G. Krasheninnikov N. Yu. Kovaleva T. A. Ladygina M. V. Lysova I. O. Leipunskii A. N. Zhigach M. L. Kuskov 《Kinetics and Catalysis》2006,47(2):251-256
Heterogenized alkylaluminoxanes prepared in situ on the montmorillonite (MMT) surface by the partial hydrolysis of AIR3 with water of the support are effective activators for metallocenes. The thermal destruction of isobutylaluminoxane molecules in the MMT-H2O/Al(i-Bu)3 system has been studied by the temperature-programmed desorption method coupled with mass spectrometry (TPD-MS). The process begins at a lower temperature and is more complicated than the destruction of methylaluminoxane (MAO) in MMT-H2O/AlMe3. Isobutyl-substituted aluminoxane and the ansa-metallocene Me2Si(Ind)2ZrCl2 form metal-alkyl complexes that are more active in propylene polymerization than methyl-substituted aluminoxane. The TPD-MS study of the initial stages of gas-phase ethylene and propylene polymerization shows that the nature of the metallocene in the heterogenized metallocene catalysts is an essential factor in the distribution of active sites by the activation energy of the thermal destruction of active Zr-C bonds. 相似文献