全文获取类型
收费全文 | 1943篇 |
免费 | 54篇 |
国内免费 | 135篇 |
专业分类
化学 | 467篇 |
晶体学 | 5篇 |
力学 | 154篇 |
数学 | 895篇 |
物理学 | 611篇 |
出版年
2024年 | 3篇 |
2023年 | 22篇 |
2022年 | 23篇 |
2021年 | 27篇 |
2020年 | 31篇 |
2019年 | 60篇 |
2018年 | 36篇 |
2017年 | 30篇 |
2016年 | 31篇 |
2015年 | 44篇 |
2014年 | 86篇 |
2013年 | 143篇 |
2012年 | 103篇 |
2011年 | 148篇 |
2010年 | 143篇 |
2009年 | 167篇 |
2008年 | 154篇 |
2007年 | 136篇 |
2006年 | 111篇 |
2005年 | 76篇 |
2004年 | 69篇 |
2003年 | 62篇 |
2002年 | 47篇 |
2001年 | 41篇 |
2000年 | 61篇 |
1999年 | 47篇 |
1998年 | 42篇 |
1997年 | 25篇 |
1996年 | 23篇 |
1995年 | 20篇 |
1994年 | 17篇 |
1993年 | 15篇 |
1992年 | 15篇 |
1991年 | 9篇 |
1990年 | 8篇 |
1989年 | 3篇 |
1988年 | 8篇 |
1987年 | 6篇 |
1986年 | 5篇 |
1985年 | 3篇 |
1984年 | 10篇 |
1983年 | 2篇 |
1981年 | 3篇 |
1979年 | 3篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1973年 | 3篇 |
1972年 | 1篇 |
1969年 | 1篇 |
排序方式: 共有2132条查询结果,搜索用时 15 毫秒
91.
92.
For any particular fluid, the set of three critical constants (CC) – pressure Pc, temperature Tc and molar volume Vc – has a central importance in defining the physical behaviour of the fluid in the gas and liquid states. However, little attention seems to have been paid in the past to the relations between the CC of different substances. In the present paper, some simple and apparently novel relations have been found between the three CC for the set of four noble gases: Ne, Ar, Kr, Xe. Defining the critical quotient Qc ≡ RTc/Pc (where R is the Gas Constant) the correlations may be summarised by the dual equation: (Vc/cm3 mol−1) = 27 + 0.31 (Tc/K) = 3.3 + 0.280 (Qc/cm3 mol−1), which describes the CC data for the quartet Ne–Xe with an average uncertainty of 0.5%. Regarding the other two noble gases, the two isotopes of the lightest member, 3He and 4He, show the deviations from these relations that are expected from quantal effects and their low molar masses; while for the heaviest member, Rn, the correlations enable a value of 145(5) cm3 mol−1 to be estimated for Vc that is not otherwise well defined in the literature. By contrast, and contrary to the general assumption, the second lightest member, Ne, apparently does not show appreciable quantal effects in the area, so that Ne–Xe may be considered together as a group. These correlations are compared with the behaviour of a selection of polyatomic fluids; in these comparisons, the NG dual correlation equation provides a reference line defining the presumed simplest behaviour. This and related areas show a “Residual Volume Effect”, in that extrapolating the equivalent temperature and energy parameters to zero for the state of zero-mass point particles, referred to here as the hypothetical element zeronium (Ze), the system in each case still has a finite intercept; this intercept amounts to essentially 34% of the average volume for the present quartet Ne–Xe, rather than the zero volume expected for this condition. 相似文献
93.
94.
稳态荧光探针法测定临界胶束聚集数 总被引:32,自引:0,他引:32
以芘为荧光探针、二苯甲酮为猝灭剂,用稳态荧光探针法测定了SDS和AS的胶束聚集数(Nm).以芘的饱和水溶液为溶剂配制表面活性剂溶液,二苯甲酮的适宜浓度取小于1.00 mmol•L-1时,可以获得满意的实验结果.当表面活性剂溶液浓度为5~9倍cmc时,Nm随表面活性剂浓度增大而线性增大,而随温度的变化略有波动.cSAA=cmc时,Nm值为一本征值,定义为临界胶束聚集数[Nm].[Nm]值可从Nm-cSAA实验曲线外延得到.25℃时SDS的临界胶束聚集数[Nm]为57;40℃时SDS的[Nm]为49,AS的[Nm]为55. 相似文献
95.
96.
Md. Sayem Alam A. Mohammed Siddiq R. Ragupathy 《Journal of Dispersion Science and Technology》2017,38(2):280-287
In the present study, we have investigated the self-association, mixed micellization, and thermodynamic studies of a cationic gemini (dimeric) surfactant, hexanediyl-1,6-bis(dimethylcetylammonium bromide (16-6-16)) and a cationic conventional (monomeric) surfactant, cetyltrimethylammonium bromide (CTAB). The critical micelle concentration (CMC) of pure (16-6-16 and CTAB) and mixed (16-6-16+CTAB) surfactants was measured by electrical conductivity, dye solubilization, and surface tension measurements. The surface properties (viz., C20 (the surfactant concentration required to reduce the surface tension by 20 mN/m), ΠCMC (the surface pressure at the CMC), Γmax (maximum surface excess concentration at the air/water interface), Amin (the minimum area per surfactant molecule at the air/water interface), etc.) of micellar (16-6-16 or CTAB) and mixed micellar (16-6-16+CTAB) surfactant systems were evaluated. The thermodynamic parameters of the micellar (16-6-16 and CTAB) and mixed micellar (16-6-16+CTAB) surfactant systems were also evaluated. 相似文献
97.
98.
99.
康东升 《数学物理学报(A辑)》2006,26(5):716-720
该文研究了一类带有Sobolev-Hardy临界指数的半线性椭圆方程,运用变分理论中的环绕定理证明了方程非平凡解的存在性 相似文献
100.
《Physics and Chemistry of Liquids》2012,50(1):111-114
Recent ab initio predictions concerning the metal-insulator (MI) transition in rings of the light alkali atoms, Li and Na, are compared and contrasted with experimental facts concerning diluted Rb and Cs alkalis. The main focus here is on the local coordination number as a function of density as these two heavy alkali metallic fluids are taken along the liquid–vapour coexistence curve towards the critical point, which in these cases coincides with the MI transition. Also recorded are the results of experiments in which Cs chains are observed at large interatomic spacing outside semiconducting substrates of InSb and GaAs. 相似文献