全文获取类型
收费全文 | 8337篇 |
免费 | 81篇 |
国内免费 | 18篇 |
专业分类
化学 | 4622篇 |
晶体学 | 90篇 |
力学 | 190篇 |
数学 | 1013篇 |
物理学 | 2521篇 |
出版年
2020年 | 63篇 |
2016年 | 97篇 |
2015年 | 80篇 |
2014年 | 94篇 |
2013年 | 291篇 |
2012年 | 216篇 |
2011年 | 230篇 |
2010年 | 141篇 |
2009年 | 162篇 |
2008年 | 207篇 |
2007年 | 244篇 |
2006年 | 225篇 |
2005年 | 258篇 |
2004年 | 210篇 |
2003年 | 177篇 |
2002年 | 174篇 |
2001年 | 123篇 |
2000年 | 130篇 |
1999年 | 140篇 |
1998年 | 80篇 |
1997年 | 105篇 |
1996年 | 146篇 |
1995年 | 148篇 |
1994年 | 119篇 |
1993年 | 126篇 |
1992年 | 133篇 |
1991年 | 121篇 |
1990年 | 110篇 |
1989年 | 102篇 |
1988年 | 107篇 |
1987年 | 125篇 |
1986年 | 91篇 |
1985年 | 126篇 |
1984年 | 121篇 |
1983年 | 121篇 |
1982年 | 129篇 |
1981年 | 108篇 |
1980年 | 131篇 |
1979年 | 111篇 |
1978年 | 122篇 |
1977年 | 117篇 |
1976年 | 104篇 |
1975年 | 102篇 |
1974年 | 95篇 |
1973年 | 95篇 |
1972年 | 58篇 |
1968年 | 51篇 |
1967年 | 52篇 |
1966年 | 54篇 |
1955年 | 59篇 |
排序方式: 共有8436条查询结果,搜索用时 0 毫秒
51.
Based upon a thermodynamical approach, the generalized Onsager type of relaxation of van der Waals networks is presented. By linearly and identically coupling the set hidden variables to the network, the memory function of the system can be related to the equilibrium strain-energy function. The relaxation behavior of real networks on stretching can quantitatively be described by means of a distribution of relaxation times known from small strain experiments. Some new and interesting conclusions are discussed as to how the macroscopically non-linear visco-elastic response might be interpreted. 相似文献
52.
53.
Th. F. Tadros 《Colloid and polymer science》1980,258(4):439-446
Summary The adsorption isotherms of lignosulphonates with various degrees of sulphonation (0.5, 1,0, 2.0 and 4.0 moles per 840 unit weight of lignin) were measured on polystyrene latex particles from aqueous solution at 25 °C. The results showed that the lignin with the lowest degree of sulphonation gave the highest adsorption. The lignin with 1.0 and 2.0 degrees of sulphonation gave similar adsorption which was lower than that obtained with the half sulphonated lignin. However, further increase in degree of sulphonation resulted in an increase in the adsorption.Adsorption layer thickness measurements showed that the lignosulphonate with half degree of sulphonation gave thicker layers than that with 2.0 moles sulphonation. Increasing electrolyte (NaCl and CaCl,) concentration resulted in a decrease in the adsorbed layer thickness. Microelectrophoresis at 25 °C, showed only small differences in the zeta potential as a function of degree of sulphonation. Addition of electrolytes (KCl, Na2SO4 and CaCl2) showed a reduction in the zeta potential. Flocculation by salts of various valence types, namely KCl, Na2SO4 and CaCl2 showed that the critical flocculation concentration (C.F.C.) decreases in the order KCl > Na2SO4 > CaCl2. The change in degree of sulphonation had only a marginal effect on the C.F.C.
Zusammenfassung Die Isothermen der Adsorption von Lignosulfonaten mit verschiedenen Sulfonierungsgraden (S = 0,5, 1,0, 2,0 und 4,0 Mole pro 840 Gewichtseinheit des Lignins) an PolystyrolLatex-Teilchen in wäßriger Lösung wurden bei 25 °C gemessen. Hiernach wird Lignin mit den niedrigsten S-Werten am stärksten adsorbiert. Lignine mitS = 1,0 und 2,0 zeigen ähnliche Adsorption; sie ist aber kleiner als die fürS = 0,5. Mit weiter steigendemS nimmt die Adsorption zu.Aus der Messung der Dicke der Adsorptionsschicht folgt, daß fürS = 0,5 größer als fürS = 2,0 ist. Bei wachsendem Zusatz von NaCl oder CaCl2 fällt ab. Nach Mikroelektrophorese-Messungen bei 25 °C hängt das -Potential nur wenig vonS ab. fällt durch die Gegenwart von KCl, Na2SO4 oder CaCl2 ab. Mit den gleichen Salzen erfolgt eine Ausflockung, wobei die kritische Flockungskonzentration CFC in der Reihenfolge KCl, Na2SO4, CaCl2 abnimmt; CFC ändert sich nur wenig mitS.相似文献
54.
55.
Edwin Weber Claus Wimmer Ingeborg Csöregh Olga Gallardo 《Journal of inclusion phenomena and macrocyclic chemistry》1997,27(2):141-153
A novel host molecule, 1, suitable for crystalline lattice-type inclusion, has been synthesized, and its cocrystal formation ability has been investigated. Host 1 proved to be of potential use for organic solvent separation and retrieval, and a promising auxiliary for solidification of certain odorous substances. The crystal structures of the solvent-free host 1, and its complex with 1,4-dioxane (1 : 1), have been determined by single crystal X-ray diffraction. The structure of 1 (guest-free) is triclinic, P
, with a = 9.452(2), b = 10.359(3), c = 13.116(3) Å, = 101.80(2), = 106.53(1) and = 104.32(1)°. The spacious, propeller-like molecules are held together by weak van der Waals' forces. The dioxane inclusion compound is monoclinic, P21/a, with a = 15.050(1), b = 8.641(1) and c = 20.658(1) Å, and = 94.56(1)°, and contains two crystallographically independent guest molecules, both located around symmetry centres. The molecular packing seems to be governed by C—H···O type bonds (C···O = 3.31 and 3.48 Å) from the host to the dioxane oxygens. 相似文献
56.
The crystal structure of 12,13-dibromopseurotin has been determined by single crystal X-ray analysis. The crystals belong to space group P21 with a = 16.75, b = 9.63, c = 7.42 Å, β 95.9°, Z = 2. The structure was solved by the heavy atom technique and refined to R = 0.062 with 819 significant reflexions for 299 parameters. 相似文献
57.
58.
The mass spectra of five diazaphenanthrenes formed by photochemical cyclodehydrogenation of styryl diazines are investigated. It is shown that fragmentation of these compounds starts almost exclusively at the heterocyclic part of the molecule and proceeds by competitive α-cleavage. From the intensity ratios of the ions [M ? H˙]+, [M ? HCN]+˙, [M ? N2]+˙ and [M ? 2 HCN]+˙ generated in this way, each isomer can unequivocally be identified. 相似文献
59.
60.