全文获取类型
收费全文 | 296篇 |
免费 | 2篇 |
国内免费 | 1篇 |
专业分类
化学 | 156篇 |
晶体学 | 9篇 |
力学 | 15篇 |
数学 | 50篇 |
物理学 | 69篇 |
出版年
2021年 | 3篇 |
2015年 | 5篇 |
2014年 | 3篇 |
2013年 | 3篇 |
2012年 | 5篇 |
2011年 | 5篇 |
2008年 | 8篇 |
2007年 | 8篇 |
2006年 | 8篇 |
2005年 | 3篇 |
2004年 | 4篇 |
2003年 | 3篇 |
2002年 | 6篇 |
2001年 | 4篇 |
2000年 | 10篇 |
1999年 | 6篇 |
1998年 | 3篇 |
1996年 | 6篇 |
1995年 | 3篇 |
1994年 | 5篇 |
1993年 | 12篇 |
1992年 | 6篇 |
1991年 | 8篇 |
1990年 | 4篇 |
1989年 | 5篇 |
1988年 | 9篇 |
1987年 | 3篇 |
1986年 | 4篇 |
1985年 | 6篇 |
1984年 | 5篇 |
1983年 | 10篇 |
1981年 | 3篇 |
1980年 | 7篇 |
1979年 | 8篇 |
1978年 | 10篇 |
1976年 | 7篇 |
1975年 | 5篇 |
1973年 | 3篇 |
1972年 | 5篇 |
1971年 | 5篇 |
1944年 | 2篇 |
1939年 | 2篇 |
1936年 | 2篇 |
1933年 | 3篇 |
1931年 | 2篇 |
1930年 | 2篇 |
1928年 | 4篇 |
1924年 | 4篇 |
1911年 | 3篇 |
1910年 | 3篇 |
排序方式: 共有299条查询结果,搜索用时 203 毫秒
51.
52.
53.
Bruins EE Bauer TS den Bok HW Duif CP van Hoek WC de Lange DJ Misiejuk A Papandreou Z Sichtermann EP Tjon JA Willering HW Yeomans DM Reike H Durek D Frommberger F Gothe R Jakob D Kranefeld G Kunz C Leiendecker N Pfeiffer G Putsch H Reichelt T Schoch B Wacker D Wehrmeister D Wilhelm M Jans E Konijn J de Vries R Furget C Voutier E Arenhövel H 《Physical review letters》1995,75(1):21-24
54.
Abstract— The self-sensitized photooxidation of mesodiphenylhelianthrene in various solvents has been investigated. The involvement of 1 O2 as the reactive intermediate in the formation of the endoperoxide has been demonstrated by the quenching of the photooxidation by the efficient 1 O2 -quencher β-carotene. The rate constant for the addition of 1 O2 to mesodiphenylhelianthrene has been determined to be k R ≅ 1010 M -1 s-1 , which is the highest value hitherto known in the literature. The probability factor p , which describes the concentration independent part of the overall quantum yield, has been measured to be p =0.17. 相似文献
55.
Eduard Bernhardt David J. Brauer Martin Köckerling Prof. Dr. Gottfried Pawelke Dr. 《无机化学与普通化学杂志》2007,633(7):947-954
Trimethylamine‐tris(pentafluoroethyl)borane [(C2F5)3BNMe3] ( 1 ) reacts at 190 °C with water under displacement of the trimethylamine ligand to yield the hydroxy‐tris(pentafluoroethyl)borate [(C2F5)3BOH]? ( 2 ). In tributylamine 1 reacts with alkynes HC≡CR to form novel ethynyl‐tris(pentafluoroethyl)borate anions [(C2F5)3BC≡CR]? – R = C6H5 ( 3 ), C6H4CH3 ( 4 ), Si(CH(CH3)2)3 ( 5 ) – in moderate yields. Compound 3 adds water across the triple bond to form the novel anion [(C2F5)3BCH2(CO)C6H5]? ( 6 ). The structures of [(C2F5)3BNMe3], [NMe4][(C2F5)3BOH] and K[(C2F5)3BCH2(CO)C6H5] have been determined by x‐ray crystallography. 相似文献
56.
Measurements of the quantum yield for photoperoxidation of 9,10-diphenylanthracene as a function of dissolved oxygen concentration in toluene at 20°C. are consistent with generation of 1O2 from both the lowest singlet and triplet states of the hydrocarbon. 相似文献
57.
Of the two crystalline products obtained by reacting a silicon tetrachloride/nitrogen mixture in a glow discharge tube, the more volatile (m. p. 78°C) has been confirmed to be tris(trichlorosilyl)amine NSi3Cl9 whereas the less volatile component (m. p. 66°C) has been identified as N,N′-bis(trichlorosilyl)-Si,Si′-tetrachloro-cyclodisildiazane N2Si4Cl10. These conclusions are supported by mass and vibrational spectroscopy and single crystal X-ray structures. NSi3Cl9 possesses a nearly planar NSi3 skeleton with average N? Si distances of 1.734(2) Å. The N2Si4 fragment of N2Si4Cl10 is roughly planar with endocyclic N? Si? N and Si? N? Si angles of 89.2(1) and 90.8(1)°, respectively, and mean N? Si distances of 1.731(3) (endocyclic) and 1.687(3) Å (exocyclic). 相似文献
58.
Christine De Brauer Patrick Germain Marie Pierre Merlin 《Journal of inclusion phenomena and macrocyclic chemistry》2002,44(1-4):197-201
The heat capacities of solid -CD, 8.1 H2O and -CD, 6.0 H2O have been measured between 10 and 300 K by adiabatic calorimetry. Using earlier results obtained in similar experiments with anhydrous cyclodextrins and with -CD, 9.7 H2O, a comparative analysis has been developed. The energetic behaviours of anhydrous and hydrated cyclodextrins (CDs) have been compared in order to investigate the role of water molecules in the stabilization of the cyclodextrin's rings and on their reactivities. Calculations, based on the additivity of thermodynamic properties, provide the energetic and entropic average contributions of water molecules in each cyclodextrin. From these results, we assumed that the water–water and water–CD interactions are rather different according to the cyclodextrin. In the (-CD, 9.7 H2O) structure, the water molecules seem to be better organised in a relatively independent network. Concerning hydrated -CD and -CD, stronger water–CD interactions probably prevent an optimal organisation of the water–water bonds network. Differential scanning calorimetry was also used to follow the evolution of the thermal behaviour of -CD, nH2O versus hydration ratio between 170 and 300 K. Our results indicate that the -CD ring needs at least 1.6 water molecules to be stabilized in the solid state. 相似文献
59.
C. Dedlow D. T. Smith J. Großfeld A. Düring O. Jones E. Waltzinger K. Brauer J. Tillmans R. Strohecker W. Schütze H. Mildner R. Otto Lüttge v. Mertz E. Arbenz R. Herzner O. Mann K. Beck W. Schneider A. Striegel K. Pfizenmaier S. Galanos Th. Sudendorf O. Lahrmann Wilhelm Müller O. Folin L. Geret A. Gompf Gart A. Behre W. Kerp G. Riess A. Juckenack M. Rubner A. Gronover E. Wohnlich H. Willke F. Junker O. Lüning St. Gerö Preußischer Ministerfür Volkswohlfahrt 《Analytical and bioanalytical chemistry》1928,73(1-3):87-104
60.
Christophe Viglianti Khalil Hanna Christine De Brauer Patrick Germain 《Journal of inclusion phenomena and macrocyclic chemistry》2006,56(1-2):275-280
The removal of Polycyclic Aromatic Hydrocarbons (PAHs) from soil using pure water is quite ineffective due to␣their low aqueous solubility. Most of present processes are based on organic cosolvents or surfactants, leading to potential environmental hazard. Addition of cyclodextrin (CD) in aqueous washing solutions has been shown to␣increase the removal efficiency several times, while being non-toxic agents. Herein are investigated the effectiveness of cyclodextrins to remove PAHs occurring in industrially aged-contaminated soil. β-cyclodextrin (BCD), hydroxypropyl-β-cyclodextrin (HPCD) and methyl-β-cyclodextrin (MCD) solutions were used for soil flushing in column test or batch experiments to evaluate some influent parameters that can significantly increase the removal efficiency. The process parameters chosen were CD concentration, ratio of washing solution volume to soil weight, and temperature of washing solution. These parameters were found to have a significant and almost linear effect on PAHs removal from the contaminated soil, except the temperature where no significant enhancement in PAHs extraction was observed for temperature range from 5 to 35 °C. Removal capacity of HPCD and MCD was higher than BCD one. The PAHs extraction enhancement factor compared to water was about 200. 相似文献