全文获取类型
收费全文 | 365170篇 |
免费 | 7378篇 |
国内免费 | 5574篇 |
专业分类
化学 | 175404篇 |
晶体学 | 5119篇 |
力学 | 20904篇 |
综合类 | 327篇 |
数学 | 64406篇 |
物理学 | 111962篇 |
出版年
2022年 | 2736篇 |
2021年 | 3576篇 |
2020年 | 3908篇 |
2019年 | 4237篇 |
2018年 | 15088篇 |
2017年 | 14688篇 |
2016年 | 12562篇 |
2015年 | 5330篇 |
2014年 | 7035篇 |
2013年 | 13817篇 |
2012年 | 15335篇 |
2011年 | 23413篇 |
2010年 | 15158篇 |
2009年 | 15421篇 |
2008年 | 18127篇 |
2007年 | 20008篇 |
2006年 | 11225篇 |
2005年 | 11051篇 |
2004年 | 10499篇 |
2003年 | 9886篇 |
2002年 | 8964篇 |
2001年 | 8894篇 |
2000年 | 6958篇 |
1999年 | 5356篇 |
1998年 | 4608篇 |
1997年 | 4353篇 |
1996年 | 4147篇 |
1995年 | 3719篇 |
1994年 | 3610篇 |
1993年 | 3432篇 |
1992年 | 3689篇 |
1991年 | 3760篇 |
1990年 | 3653篇 |
1989年 | 3382篇 |
1988年 | 3325篇 |
1987年 | 3310篇 |
1986年 | 3130篇 |
1985年 | 3821篇 |
1984年 | 4070篇 |
1983年 | 3409篇 |
1982年 | 3551篇 |
1981年 | 3438篇 |
1980年 | 3274篇 |
1979年 | 3475篇 |
1978年 | 3564篇 |
1977年 | 3543篇 |
1976年 | 3718篇 |
1975年 | 3390篇 |
1974年 | 3399篇 |
1973年 | 3561篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
181.
Kinetics of oxidation of indigo carmine (IC) by sodium hypohalites, NaOX (X ? Cl or Br), in alkaline buffer of pH 9–11 has been studied spectrophotometrically at λ = 610 nm. The experimental rate law obtained is ?d[IC]/dt = k[OX?][IC][OH?]x where x <1. Variation of ionic strength or dielectric constant of the medium had no effect on the reaction rate while the addition of halide ions slightly retarded the rate. A most plausible mechanism proposed on the basis of experimental results involves the formation of isatin sulphonate which undergoes further oxidation to anthranilate. Activation parameters have been evaluated. 相似文献
182.
The impurity weakening of crystalline NaCl:Mg and NaCl:Mn associated with purification of the matrix in a melt is demonstrated.
This effect is manifested in a consistent change in the yield strength and mobility of dislocations. Its unusual temperature
dependence is determined: in a number of cases weakening becomes greater as the temperature is lowered within the interval
293–4.2 K. A deviation in the elastic region of the stress-strain curves is observed to increase as the temperature is lowered.
Plasticizing of crystalline NaCl is established: when the deformation temperature is lowered from 293 to 77 and 4.2 K the
rate of rise in the yield strength of Cd2+ and Sr2+ doped samples is lower than that of undoped samples. An explanation for this fact is proposed.
Fiz. Tverd. Tela (St. Petersburg) 39, 313–317 (February 1997)
Deceased. 相似文献
183.
J. S. Vrentas D. C. Venerus C. M. Vrentas 《Journal of Polymer Science.Polymer Physics》1991,29(5):537-545
An integral constitutive equation which includes strain-coupling effects is proposed. The constitutive equation is more general than the K-BKZ equation, and it is shown that this equation can explain various important aspects of double-step stress-relaxation data. 相似文献
184.
185.
186.
James Tanton 《Mathematical Intelligencer》2007,29(3):55-59
This column is a place for those bits of contagious mathematics that travel from person to person in the community, because
they are so elegant, suprising, or appealing that one has an urge to pass them on.
Contributions are most welcome. 相似文献
187.
188.
X-ray, DSC and optical studies of a new class of substances with aromatic rings in the lateral branches are reported. The thermal behaviour of the substances is discussed. The X-ray measurements lead to a structural model of the SA phases consisting of layer structures with intercalating molecules. 相似文献
189.
In this paper we examine clathrate formation in the tetraisoamylammonium propionate-water binary system. We have found formation
of four polyhydrates, two of which are metastable over the whole temperature range studied. All polyhydrate crystals were
isolated and their compositions and densities determined; for (i-C5H11)4NC2H5COO·36.5H2O, unit cell parameters were additionally found. The results are compared with data for tetra-n-butylammonium carboxylate
polyhydrates, and the structure of the title compounds is suggested. It is confirmed that the isoamyl radical stabilizes the
tetradecahedral void of the clathrate hydrate framework better than the n-butyl radical.
Institute of Inorganic Chemistry, Siberian Branch, Russian Academy of Sciences. Translated fromZhurnal Strukturnoi Khimii, Vol. 35, No. 3, pp. 67–71, May–June, 1994.
Translated by L. Smolina 相似文献
190.
In this paper we show that the director profile of a low pre-tilt surface stabilized ferroelectric liquid crystal passes through quasi-static stressed states during domain switching under direct drive conditions. Using polarized stroboscopic microscopy, we have observed two quasi-static transmission levels during a domain switching transition from dark to light. This is a result of the directors reorienting into stressed profiles both before and after the chevron interface has switched. By modelling the interaction between the elastic forces and the torque from the applied field, we have determined these voltage dependent director profiles and, by calculating their corresponding transmissivities, have shown very good agreement with the experimentally observed values. 相似文献