全文获取类型
收费全文 | 328篇 |
免费 | 19篇 |
国内免费 | 15篇 |
专业分类
化学 | 202篇 |
晶体学 | 8篇 |
力学 | 5篇 |
综合类 | 2篇 |
数学 | 30篇 |
物理学 | 115篇 |
出版年
2021年 | 10篇 |
2019年 | 5篇 |
2016年 | 5篇 |
2015年 | 9篇 |
2014年 | 10篇 |
2013年 | 10篇 |
2012年 | 15篇 |
2011年 | 12篇 |
2010年 | 15篇 |
2009年 | 7篇 |
2008年 | 15篇 |
2007年 | 21篇 |
2006年 | 19篇 |
2005年 | 17篇 |
2004年 | 11篇 |
2003年 | 6篇 |
2002年 | 11篇 |
2001年 | 7篇 |
2000年 | 14篇 |
1999年 | 8篇 |
1998年 | 3篇 |
1997年 | 6篇 |
1996年 | 3篇 |
1995年 | 4篇 |
1994年 | 5篇 |
1993年 | 7篇 |
1991年 | 5篇 |
1990年 | 4篇 |
1988年 | 7篇 |
1987年 | 7篇 |
1986年 | 4篇 |
1985年 | 5篇 |
1984年 | 3篇 |
1983年 | 3篇 |
1982年 | 5篇 |
1981年 | 3篇 |
1980年 | 3篇 |
1978年 | 7篇 |
1975年 | 4篇 |
1974年 | 2篇 |
1965年 | 2篇 |
1962年 | 2篇 |
1943年 | 2篇 |
1942年 | 2篇 |
1937年 | 3篇 |
1936年 | 2篇 |
1935年 | 2篇 |
1933年 | 2篇 |
1932年 | 2篇 |
1900年 | 2篇 |
排序方式: 共有362条查询结果,搜索用时 15 毫秒
101.
The anodic coupling of iodobenzene and benzene to the diphenyliodonium cation is shown to be based on attack of an iodobenzene radical cation on a benzene molecule at the anode surface. Only on platinum anodes in acetonitrile solutions the respective adsorption conditions of benzene and iodobenzene are so favourable that a self coupling to the iodophenylphenyliodonium cation can be avoided. According to the predictions which are based on the electrode kinetic investigations, optimal conditions for the coupling are: (1) low working temperature, (2) low working potential (i.e.c.d. around 18–20 mA cm?2), (3) high iodobenzene/benzene ratio in the bulk of the solution. Under these conditions 85% current efficiency and 95% mass yield for the coupling are obtained. 相似文献
102.
Flumorph (SYP‐L190) is a new systemic fungicide with good protective, curative and antisporulant activities but no phytotoxicity to certain plants. Its performance on the environmental ecosystem is unknown. Tetrahymena thermophila and Bacillus thuringiensis are two of biological indicators for the aquatic and soil environmental ecosystem respectively. Microcalorimetric technique based on the heat output was applied to evaluate the influence of fungicide flumorph (SYP‐L190) on the two microorganisms. The thermogenic curves and corresponding thermodynamic and thermokinetic parameters were obtained. SYP‐L190 at a concentration of 50–100 µg·mL?1 had 5% –10% inhibitory ratios aganist Tetrahymena thermophila and was used as a protection reagent, while at a concentration of 100–200 µg·mL?1 SYP‐L190 had 10% –20% inhibitory ratios and was used as a therapy reagent. The metabolic thermogenic curves of Bacillus thuringiensis contained bacterial growth phase and sporulation phase. The SYP‐L190 at a concentration of 0–200 µg·mL?1 had no influence on bacterial growth phase, but led to a little lag of the sporulation phase with a constant heat output. Hormesis was obviously observed in present study. 相似文献
103.
104.
105.
106.
107.
氯化钆与L-酪氨酸和甘氨酸三元固态配合物的热化学及热分解动力学研究 总被引:6,自引:0,他引:6
合成表征了氯化钆与L 酪氨酸和甘氨酸形成的三元固态配合物Gd(Tyr) (Gly) 3 Cl3 ·3H2 O .用具有恒温环境的溶解 -反应热量计 ,测定了配位反应GdCl3 ·6H2 O (s) +Tyr (s) +3Gly (s) =Gd(Tyr) (Gly) 3 Cl3 ·3H2 O (s) +3H2 O (l)在 2 98.15K时的反应焓为 ( 9.45 1± 0 .468)kJ·mol-1 .计算得配合物Gd(Tyr) (Gly) 3 Cl3 ·3H2 O (s)在 2 98.15K时的标准摩尔生成焓为ΔfH m =-( 4 2 69.7± 2 .3 )kJ·mol-1 .并用热分析手段对配合物进行了非等温热分解动力学研究 ,推断配合物第二步热分解反应机理为二级化学反应 ,其动力学方程为 :dα/dT =(A/β)exp( -E/RT) ( 1-α) 2 ,求得分解反应的表观活化能为E =2 15 .17kJ·mol-1 ,指前因子为 10 1 8.71 s-1 . 相似文献
108.
More than 150 years ago Sir Groe invented the fuel cell. Material problems prohibited this type of gassupplied battery to go to market for a very long time. A break-through was achieved during the last 30 years so that today we can distinguish two low-temperature fuel cell technologies (phosphoric acid and membrane cells) from two high-temperature technologies (molten carbonate and oxide ceramic cells) with a working temperature of 650 and 80 to 900°C, respectively. But today only phosphoric acid fuel cells are offered commeriall as containerized 200-kW cogeneration power plants. Membrane cells are most suitable for electrotraction of aumobiles offering a remarkbly low weight per unit power and working with zero emission. The fuel is, however, a particular problem as hydrogen is not easy to store and too expensive. The ultimate goal is supplying the car with methanol and combusing methanol directly in the fuel cell. However, this aim might be only achieved after several more years of intensive research and development. 相似文献
109.
110.
A. Nieminen I. D. Moore J. Billowes P. Campbell K. T. Flanagan Ch. Geppert J. Huikari A. Jokinen T. Kessler B. Marsh H. Penttilä S. Rinta-Antila B. Tordoff K. D. A. Wendt J. Äystö 《Hyperfine Interactions》2005,162(1-4):39-43
The application of laser ionisation is being developed for the IGISOL mass separator facility in Jyväskylä, Finland. The conceived laser ion source will have two independent pulsed laser systems based on all solid-state lasers and dye lasers for maximal coverage of ionisation schemes throughout the periodic table. A laser ion source trap, LIST, method will be pursued for optimal selectivity. 相似文献