全文获取类型
收费全文 | 3660篇 |
免费 | 449篇 |
国内免费 | 247篇 |
专业分类
化学 | 2460篇 |
晶体学 | 14篇 |
力学 | 161篇 |
综合类 | 22篇 |
数学 | 511篇 |
物理学 | 1188篇 |
出版年
2024年 | 13篇 |
2023年 | 66篇 |
2022年 | 90篇 |
2021年 | 96篇 |
2020年 | 104篇 |
2019年 | 93篇 |
2018年 | 75篇 |
2017年 | 62篇 |
2016年 | 143篇 |
2015年 | 118篇 |
2014年 | 171篇 |
2013年 | 259篇 |
2012年 | 328篇 |
2011年 | 308篇 |
2010年 | 220篇 |
2009年 | 180篇 |
2008年 | 253篇 |
2007年 | 199篇 |
2006年 | 184篇 |
2005年 | 170篇 |
2004年 | 143篇 |
2003年 | 150篇 |
2002年 | 123篇 |
2001年 | 97篇 |
2000年 | 71篇 |
1999年 | 65篇 |
1998年 | 47篇 |
1997年 | 58篇 |
1996年 | 62篇 |
1995年 | 49篇 |
1994年 | 43篇 |
1993年 | 37篇 |
1992年 | 26篇 |
1991年 | 19篇 |
1990年 | 25篇 |
1989年 | 16篇 |
1988年 | 15篇 |
1987年 | 14篇 |
1986年 | 14篇 |
1985年 | 18篇 |
1984年 | 22篇 |
1983年 | 13篇 |
1982年 | 13篇 |
1981年 | 8篇 |
1980年 | 14篇 |
1979年 | 14篇 |
1978年 | 7篇 |
1976年 | 8篇 |
1975年 | 5篇 |
1974年 | 5篇 |
排序方式: 共有4356条查询结果,搜索用时 46 毫秒
991.
992.
993.
Prof. Dr. Sunney I. Chan Yu‐Jhang Lu Dr. Penumaka Nagababu Dr. Suman Maji Mu‐Cheng Hung Marianne M. Lee Prof. Dr. I‐Jui Hsu Pham Dinh Minh Jeff C.‐H. Lai Kok Yoah Ng Sridevi Ramalingam Prof. Dr. Steve S.‐F. Yu Prof. Dr. Michael K. Chan 《Angewandte Chemie (International ed. in English)》2013,52(13):3731-3735
994.
In this work, low-temperature vulcanized, transparent silane modified epoxy resins for LED filament bulb package were prepared. Firstly, transparent silane modified epoxy resins were produced through a controllable sol-gel method using γ-(2,3-epoxypropoxy)propytrimethoxysilane and dimethyldiethoxylsilane. The features of the reaction were investigated and the products were characterized in detail. Subsequently, various curing agents were explored to prepare transparent silane modified epoxy resins. The silane modified epoxy resins cured by PEA-230 at a fairly low temperature(40 °C/2 h then 60 °C/1 h) exhibited excellent thermal stability with a thermal degradation temperature as high as 316.5 °C and adjustable hardness between 40-60 shore A. The application tests showed the materials obtained were good candidates for LED filament bulb package. 相似文献
995.
Sheng Chang Yong Bing Sun Xiu Rong Zhang Lin Lin Dong He Yun Zhu Hong Wei Lai Dan Wang 《应用有机金属化学》2018,32(1)
An efficient procedure for the synthesis of biaryls was catalyzed by Pd(CH3CN)4(BF4)2 is reported. This Pd‐catalyzed cross‐coupling reaction of aryltrifluoroborates with sodium arenesulfinates was developed under mild and environmentally benign conditions, in water without any ligand or additive. The reaction gave a range of structurally diverse unsymmetrical bi‐aryl molecules with excellent yields, in which the byproduct was sulfur dioxide. It is worth noting that this protocol is also applicable to many heterocyclic aromatics such as thiophene, furan, pyridine, quinoline, isoquinoline and indole. 相似文献
996.
Wenjian Wu Xingrong Zeng Hongqiang Li Xuejun Lai Zengyang Yan 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(3):229-239
Polyhydroxylated polybutadiene (PHPB) was synthesized via a thiol-ene click reaction between hydroxyl-terminated polybutadiene (HTPB) and 2-mercaptoethanol (ME) with 2,2’-azoisobutyronitrile (AIBN) as initiator. Effects of AIBN content, reaction time and temperature on the click reaction were investigated by determining hydroxyl value of the PHPB. The PHPB was characterized by FT-IR, 1H-NMR, 13C-NMR and GPC. Relative reactivity of three types of C?C double bonds (1,2-vinyl, 1,4-cis and 1,4-trans units) in the HTPB reacting with the ME was discussed. The results showed that the optimal reaction conditions were that the AIBN content, reaction time and temperature were 2.0 wt%, 180 min and 70°C, respectively. Under these conditions, the hydroxyl value of the PHPB was 3.12 mmol·g?1 when the HTPB/ME mass ratio was 10:2. All three types of C?C double bonds in the HTPB could react with the ME and the reactivity order was: 1,2-vinyl unit > 1,4-cis unit > 1,4-trans unit. 相似文献
997.
998.
The mesogenic behaviours of two azo dye liquid crystals, 1 and 4, differ because of the different length of terminal alkyl chains; azo dye 1 shows a SmB phase, azo dye 4 shows nematic and SmA phases during thermal processing. The molecular stackings of these two azo dye liquid crystals are compared on the basis of crystallographic studies to explain such unexpected mesogenic behaviour. 相似文献
999.
Chunbo Lai Chanjuan Xi Yuping Feng 《Phosphorus, sulfur, and silicon and the related elements》2013,188(3):449-455
Alkyllithium reacts with chlorophosphate to generate the α -lithio- alkylidenediphosphonate, which further reacts with halogen reagents to afford corresponding α -halogenated alkylidenediphosphonates. 相似文献