全文获取类型
收费全文 | 8978篇 |
免费 | 1513篇 |
国内免费 | 855篇 |
专业分类
化学 | 6391篇 |
晶体学 | 115篇 |
力学 | 493篇 |
综合类 | 63篇 |
数学 | 1057篇 |
物理学 | 3227篇 |
出版年
2024年 | 20篇 |
2023年 | 152篇 |
2022年 | 233篇 |
2021年 | 273篇 |
2020年 | 333篇 |
2019年 | 321篇 |
2018年 | 286篇 |
2017年 | 269篇 |
2016年 | 380篇 |
2015年 | 414篇 |
2014年 | 485篇 |
2013年 | 695篇 |
2012年 | 809篇 |
2011年 | 796篇 |
2010年 | 574篇 |
2009年 | 533篇 |
2008年 | 602篇 |
2007年 | 502篇 |
2006年 | 516篇 |
2005年 | 417篇 |
2004年 | 372篇 |
2003年 | 280篇 |
2002年 | 274篇 |
2001年 | 205篇 |
2000年 | 147篇 |
1999年 | 158篇 |
1998年 | 145篇 |
1997年 | 155篇 |
1996年 | 151篇 |
1995年 | 112篇 |
1994年 | 114篇 |
1993年 | 88篇 |
1992年 | 55篇 |
1991年 | 54篇 |
1990年 | 59篇 |
1989年 | 40篇 |
1988年 | 28篇 |
1987年 | 21篇 |
1986年 | 33篇 |
1985年 | 29篇 |
1984年 | 22篇 |
1983年 | 19篇 |
1982年 | 11篇 |
1981年 | 13篇 |
1980年 | 16篇 |
1979年 | 10篇 |
1978年 | 22篇 |
1977年 | 10篇 |
1976年 | 13篇 |
1974年 | 12篇 |
排序方式: 共有10000条查询结果,搜索用时 21 毫秒
821.
822.
Jing Sun Jian‐Gong Cheng Wen‐Qing Zhu Shi‐Jie Ren Hong‐Liang Zhong Dan‐Li Zeng Jun‐Ping Du Er‐Jian Xu Ying‐Chun Liu Qiang Fang 《Journal of polymer science. Part A, Polymer chemistry》2008,46(16):5616-5625
A new X‐shaped π‐conjugated monomer comprising of fluorene units and anthracene units was synthesized, and it was used to fabricate the new X‐shaped π‐conjugated polymers and investigate the properties of the new polymers. Using different molar ratios between such monomer and a fluorene monomer gave three polymers that showed higher absolute PL quantum yields than the linear polyfluorene (PF) in the solid state. After thermal annealing at 200 °C for 4 h, the linear PF showed an additional bathochromic emission at about 550 nm, whereas such red‐shifted emission was fully eliminated for the X‐shaped polymers. The electroluminescent devices based on the X‐shaped polymers with a configuration of ITO/PEDOT:PSS/polymer/LiF/Ca/Al displayed blue emission with low turn‐on voltage and high brightness. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5616–5625, 2008 相似文献
823.
设$M$是右$R$-模, $\aleph$是一个无穷基数. 称右$R$-模$N$是$\aleph$-$M$-凝聚的,如果对任意的$B/A\hookrightarrow mR$,其中设$M$是右$R$-模, $\aleph$是一个无穷基数. 称右$R$-模$N$是$\aleph$-$M$-凝聚的,如果对任意的$B/A\hookrightarrow mR$,其中设$M$是右$R$-模, $\aleph$是一个无穷基数. 称右$R$-模$N$是$\aleph$-$M$-凝聚的,如果对任意的$B/A\hookrightarrow mR$,其中设$M$是右$R$-模, $\aleph$是一个无穷基数. 称右$R$-模$N$是$\aleph$-$M$-凝聚的,如果对任意的$B/A\hookrightarrow mR$,其中$0\leq A相似文献
824.
825.
In this first part we propose and analyse a model for the study of two‐dimensional incompressible Navier–Stokes equations with a temperature‐dependent viscosity. The flow is supposed in a mixed convection regime and considers an outflow region, leading to a strongly coupled problem between the Navier–Stokes and energy equations, which will be justified theoretically. The coupling in the continuous problem is treated by an outer temperature fixed point strategy. Existence results for a particular variational formulation follows from this study. Further, a particular uniqueness result for small data is also obtained. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
826.
Catalyzed by ytterbium(Ⅲ) triflate hydrate [Yb(OTf)3.xH2O], the Michael addition and cycloeondensation of α,β-unsaturated ketones with active methylene compounds to afford the 1,4-adducts and benzo[b]pyran derivatives, respectively were studied. 相似文献
827.
828.
829.
830.
The toughening effect of ethylene‐vinyl acetate rubbers (EVM) with maleated ethylene‐vinyl acetate copolymers (EVA‐g‐MAH) on the nylon 1010 was investigated. The addition of 5 phr (per hundred nylon 1010) EVM increased the elongation at break of nylon 1010 to a great extent. The notched Izod impact strength of nylon/EVM blends increased with increasing EVM content. Scanning electron microscope showed that the EVM particle size was around 0.5 μm when the EVM content was 5 phr and increased with increasing EVM content. After the addition of EVA‐g‐MAH to nylon/EVM (100/20) blend, the average diameter of EVM particles decreased from more than 1 μm to 0.5–0.6 μm. EVA‐g‐MAH could improve the adhesion between nylon 1010 and EVM. A sharp brittle‐ductile transition (BDT) was observed when the interparticle distance was about 0.2 μm, independent of the addition of EVA‐g‐MAH. The notched Izod impact strength of nylon/EVM blends at low temperatures was measured and the BDT shifted toward low temperatures with increasing EVM or EVA‐g‐MAH content. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 434–444, 2009 相似文献