全文获取类型
收费全文 | 2060篇 |
免费 | 10篇 |
专业分类
化学 | 822篇 |
晶体学 | 34篇 |
力学 | 48篇 |
数学 | 193篇 |
物理学 | 973篇 |
出版年
2022年 | 16篇 |
2021年 | 30篇 |
2020年 | 22篇 |
2019年 | 28篇 |
2018年 | 57篇 |
2017年 | 72篇 |
2016年 | 105篇 |
2015年 | 49篇 |
2014年 | 75篇 |
2013年 | 123篇 |
2012年 | 126篇 |
2011年 | 142篇 |
2010年 | 127篇 |
2009年 | 135篇 |
2008年 | 136篇 |
2007年 | 132篇 |
2006年 | 132篇 |
2005年 | 85篇 |
2004年 | 61篇 |
2003年 | 28篇 |
2002年 | 30篇 |
2001年 | 30篇 |
2000年 | 48篇 |
1999年 | 20篇 |
1998年 | 41篇 |
1997年 | 25篇 |
1996年 | 6篇 |
1995年 | 9篇 |
1994年 | 5篇 |
1993年 | 5篇 |
1990年 | 4篇 |
1989年 | 4篇 |
1987年 | 6篇 |
1985年 | 6篇 |
1984年 | 8篇 |
1983年 | 10篇 |
1982年 | 7篇 |
1981年 | 9篇 |
1980年 | 13篇 |
1979年 | 10篇 |
1978年 | 10篇 |
1977年 | 9篇 |
1976年 | 11篇 |
1975年 | 6篇 |
1974年 | 5篇 |
1973年 | 7篇 |
1967年 | 5篇 |
1966年 | 3篇 |
1963年 | 3篇 |
1959年 | 4篇 |
排序方式: 共有2070条查询结果,搜索用时 515 毫秒
81.
Dorota Majda Wac?aw Makowski Maria Mańko 《Journal of Thermal Analysis and Calorimetry》2012,109(2):663-669
Thermoporosimetry, i.e., DSC measurements of melting point depression of water and heptane confined in mesopores, has been used for determination the pore size distribution of several mesoporous silicas synthesized with the use of micelle templates. Porosity of these materials was additionally characterized by low-temperature nitrogen adsorption and quasi-equilibrated thermodesorption of nonane. The pore size distributions obtained using the water thermoporosimetry were similar to those determined using the other methods, but the pore size values found for the narrow pore materials were underestimated by ca 1?nm. Too large pore sizes obtained for the wide pore silica from heptane thermoporosimetry were attributed to nonlinear dependence of the melting point depression on the reciprocal of the pore size. 相似文献
82.
The isotropic cationic networks (CNs) completing the anisotropic CNs ai isotropic CNs binary opposition are identical in the
structures of various rare earth compounds. 相似文献
83.
Vladimir Fal’ko Andre Geim Sankar Das Sarma Allan MacDonald Philip Kim 《Solid State Communications》2009,149(27-28):1039-1040
84.
Various methods are studied for preparing stable gas mixtures with trace amounts of volatile substances based on a buffer
effect of heterogeneous systems and implemented into headspace analysis, that is, static and dynamic versions of gas extraction.
Information is provided on certified procedures for preparing such mixtures, that is, vapor-phase sources of gas mixtures
included into the State Register of Measuring Instruments. 相似文献
85.
Fundamental aspects of phosphorite powder decomposition by citric acid were studied. 相似文献
86.
M. Randić M. Vračko M. Novič D. Plavšić 《SAR and QSAR in environmental research》2013,24(5-6):415-427
We consider a spectrum-like two-dimensional graphical representation of proteins based on a reduced protein model in which 20 amino acids are grouped into five classes. This particular grouping of amino acids was suggested by Riddle and co-workers in 1997. The graphical representation is based on depicting sequentially the amino acids on five horizontal lines at equal separations. One-letter codes, B, O, U, X and Y, to which numerical values 1 to 5 have been assigned, are suggested as labels for the fictional amino acids that represent all the amino acids within each group. The approach is illustrated on ND6 proteins of eight species having from 168 to 175 amino acids. While visual inspection of the novel spectral graphical representations of proteins may reveal local similarities and dissimilarities of protein sequences, arithmetic manipulations of spectra offer an elegant route to graphic visualization of the degree of similarity for selected pairs of proteins. 相似文献
87.
E. Illeková J. Krištiak E. Macová I. Maťko O. Šauša 《Journal of Thermal Analysis and Calorimetry》2013,113(3):1187-1196
The solidification/melting of cetane confined in nine silica glasses with specific controlled pores (CPG) with different pore sizes (r p ranging from 3.7–72 nm) has been studied. Samples with variable coefficient of filling of cetane were prepared and analyzed. Combining the indication of the evolving solidification heats (via differential scanning calorimetry, DSC) with the lifetime spectra of positron annihilation, the mechanism of filling of cetane molecules in the pores of the hosting silica glass matrices has been searched. Three independent solidification effects—three independent DSC peaks—were observed in each measuring cycle, namely one crystallization exotherm Rb of the bulk-cetane (if present) and two crystallization sub-peaks Rc1 and Rc2 of the confined cetane in the case of continuous cooling. The temperatures of both Rc1 and Rc2 effects decrease on decreasing the r p of the CPG matrix. The mutual relation between Rc1 and Rc2 has been analyzed. The kinetics of all three steps of the solidification in the continuous-cooling as well as isothermal regimes have been specified. 相似文献
88.
Ljubiša Balanović Dragana Živković Dragan Manasijević Duško Minić Bata Marjanović 《Journal of Thermal Analysis and Calorimetry》2013,111(2):1431-1435
The results of calorimetric study and thermal analysis of binary Al–Sn system are presented in this paper. The Oelsen calorimetry was used in thermodynamic analysis. Following thermodynamic properties were determined at 727 °C: activities, activity coefficients, partial/integral molar Gibbs excess, and mixing energies. The energetics of mixing in liquid Al–Sn alloys has been analyzed through the study of concentration fluctuation in the long-wavelength limit. Thermal analysis of selected alloys in Al–Sn system was done using differential thermal analysis. Defined characteristic phase transition temperatures were used for comparison with calculated phase diagram of investigated system. Good agreement with available literature data was obtained. Structural analysis of selected alloys was done using optic microscopy. 相似文献
89.
Yu. S. Dzyaz’ko L. N. Ponomareva Yu. M. Vol’fkovich V. E. Sosenkin V. N. Belyakov 《Russian Journal of Electrochemistry》2013,49(3):209-215
The organo-inorganic composites based on a strongly acid gel resin including zirconium hydro-phosphate nanoparticles and their aggregates were studied by impedance spectroscopy, electron microscopy, and standard contact porosimetry. The porous structure of the polymer was transformed under the action of the inorganic filler. The nanoparticles in the transport pores provided a three- to fivefold increase in the electric conductivity of the nanocomposites compared with the conductivity of the nonmodified ionite and a decrease in the percolation threshold. The nanocomposite ionites demonstrated stability against the accumulation of organic substances during electrodeionization to extract Na+ from low-concentrated solutions. 相似文献
90.
V. Yu. Buz’ko G. Yu. Chuiko A. A. Polushin Kh. B. Kushkhov 《Russian Journal of Inorganic Chemistry》2013,58(9):1070-1072
The structural features of solvation and diffusion characteristics of U(IV) ion in model 2LiF-BeF2 melts (Flibe) at 750–1600 K have been studied by the molecular dynamics simulation method. The diffusion activation energy of U(IV) ion in the 2LiF-BeF2 melt has been calculated. 相似文献