全文获取类型
收费全文 | 358260篇 |
免费 | 2278篇 |
国内免费 | 746篇 |
专业分类
化学 | 174855篇 |
晶体学 | 5234篇 |
力学 | 17639篇 |
综合类 | 7篇 |
数学 | 52543篇 |
物理学 | 111006篇 |
出版年
2021年 | 2396篇 |
2020年 | 2666篇 |
2019年 | 3071篇 |
2018年 | 11381篇 |
2017年 | 12022篇 |
2016年 | 9238篇 |
2015年 | 3787篇 |
2014年 | 5253篇 |
2013年 | 11956篇 |
2012年 | 12789篇 |
2011年 | 21435篇 |
2010年 | 13943篇 |
2009年 | 13969篇 |
2008年 | 19367篇 |
2007年 | 22420篇 |
2006年 | 9922篇 |
2005年 | 14148篇 |
2004年 | 10709篇 |
2003年 | 10288篇 |
2002年 | 8442篇 |
2001年 | 7869篇 |
2000年 | 6288篇 |
1999年 | 4528篇 |
1998年 | 3973篇 |
1997年 | 3884篇 |
1996年 | 3713篇 |
1995年 | 3127篇 |
1994年 | 3187篇 |
1993年 | 3214篇 |
1992年 | 3397篇 |
1991年 | 3498篇 |
1990年 | 3331篇 |
1989年 | 3358篇 |
1988年 | 3227篇 |
1987年 | 3147篇 |
1986年 | 3012篇 |
1985年 | 3854篇 |
1984年 | 4095篇 |
1983年 | 3331篇 |
1982年 | 3631篇 |
1981年 | 3412篇 |
1980年 | 3175篇 |
1979年 | 3452篇 |
1978年 | 3704篇 |
1977年 | 3653篇 |
1976年 | 3580篇 |
1975年 | 3398篇 |
1974年 | 3384篇 |
1973年 | 3534篇 |
1972年 | 2393篇 |
排序方式: 共有10000条查询结果,搜索用时 8 毫秒
981.
982.
V. M. Arzhavitin 《Technical Physics》2003,48(6):797-799
The stressed state of in metallic composite systems is analyzed. It is analytically shown that the temperature dependences of the internal friction in the composites may have extrema that are caused by internal stresses. The analytical results are supported by the experimental temperature dependences of the internal friction in (Cu-13% Sn)-30% Nb and Cu-1.3% Cr composites. 相似文献
983.
984.
An effect of Berry’s phase on the NQR spectrum of the rotating powder sample is described and applied for the determination of the electric field gradient asymmetry. The proposed method involves the analysis of the frequency singularities in the NQR powder patterns of the rotating samples. The Berry’s phases for the eigenstates, associated with an adiabatically changing quadrupole hamiltonian, are calculated for nuclei with a spin I = 3/2 and I = 1 as a function of the asymmetry parameter. 相似文献
985.
A. A. Solov’ev M. A. Pashina O. E. Lebedeva 《Russian Journal of Applied Chemistry》2007,80(2):275-278
The influence of inorganic salts on the kinetics of oxidation of 2,4-and 2,6-dinitrophenols by Fenton’s reagent, hydrogen peroxide, in the presence of iron(II) ions was studied. 相似文献
986.
S. Mentus Dijana Jelić Veselinka Grudić 《Journal of Thermal Analysis and Calorimetry》2007,90(2):393-397
Thermal decomposition of lanthanum nitrate to lanthanum oxide was carried out by both temperature programmed heating (TPH)
and citrate-gel combustion. The temperature programmed heating was carried out under flow of oxidizing (air), neutral (nitrogen)
and reducing (25 vol.% hydrogen+argone mixture) gases, and the processes were controlled by simultaneous thermogravimetry
and differential thermal analysis. It was shown that hydrogen atmosphere helps to reduce temperatures of all decomposition
steps. The results of TPH were utilized to check the nature of residues in the products of lanthanum nitrate-to-oxide conversion
performed via citrate-gel combustion technique. 相似文献
987.
M. C. Caracoche J. A. Martínez P. C. Rivas M. A. Taylor A. F. Pasquevich S. Barolin O. A. de Sanctis 《Hyperfine Interactions》2007,179(1-3):87-93
The hyperfine quadrupole interaction at Hf sites in films and powders of 14 mol% CaO–HfO2 and 20 mol% CaO–HfO2 has been determined as a function of temperature. Results indicate the formation of a cubic solid solution and other microstructures assigned to the ?1 (CaHf4O9) and ?2 (Ca6Hf19O44) phases. Dynamical effects on the electric field gradient reveal the existence of oxygen vacancies movements in the solid solution. The thermal behavior of the relaxation constant observed in films allowed the determination of activation energies of 0.54 eV and 0.70 eV for the 14 mol% and 20 mol% CaO doped hafnias, respectively. The influence of the microdomains and the stability of the cubic solid solution are discussed. 相似文献
988.
L. V. Giurgiu M. N. Grecu X. Filip O. Raita Al. Darabont D. Gavre J. Blasco 《Applied magnetic resonance》2003,24(3-4):351-360
We report an electron paramagnetic resonance (EPR) investigation of the spin dynamics in the paramagnetic regime of the colossal magnetoresistive manganites La2/3Ca1/3Mn1?x Me x O3 (Me=Al, In;x≤0.05). The temperature dependences of the EPR linewidth and integral intensity have been analyzed in terms of the bottleneck spin relaxation and small-polaron hopping models. The exchange coupling integral between Mn3+ and Mn4+ ions and the polaron activation energy decrease with increasing doping level. A discussion is given concerning the factors which could explain the observed changes. 相似文献
989.
Infrared difference spectroscopy has been used to study the association of p-nitrophenol (NP) with butyl acetate (BA) in CCl4 and in undiluted BA. It has been shown that in CCl4, an associate is formed, [NP·BA] ·BA (Ia), in which one molecule of BA is linked to the NP by a hydrogen bond, and the second BA molecule is linked to the H-complex NP·BA by outer-sphere (dipole-dipole) interaction. In undiluted BA with low concentrations of NP, (Ia) is formed; with high concentrations of NP, an associate [(NP)2BA] ·mBA is formed, in which two molecules of NP are bonded successively to each other and with a BA molecule; and the number of outer-sphere BA molecules may depend on the concentration of free BA molecules in the solutions.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 3, pp. 593–599, March, 1991. 相似文献
990.
Translated from Matematicheskie Zametki, Vol. 49, No. 5, pp. 37–44, May, 1991. 相似文献