全文获取类型
收费全文 | 1285篇 |
免费 | 270篇 |
国内免费 | 284篇 |
专业分类
化学 | 793篇 |
晶体学 | 51篇 |
力学 | 104篇 |
综合类 | 19篇 |
数学 | 176篇 |
物理学 | 696篇 |
出版年
2024年 | 2篇 |
2023年 | 17篇 |
2022年 | 44篇 |
2021年 | 49篇 |
2020年 | 56篇 |
2019年 | 51篇 |
2018年 | 52篇 |
2017年 | 62篇 |
2016年 | 57篇 |
2015年 | 52篇 |
2014年 | 74篇 |
2013年 | 98篇 |
2012年 | 109篇 |
2011年 | 111篇 |
2010年 | 104篇 |
2009年 | 92篇 |
2008年 | 106篇 |
2007年 | 92篇 |
2006年 | 94篇 |
2005年 | 96篇 |
2004年 | 52篇 |
2003年 | 40篇 |
2002年 | 45篇 |
2001年 | 55篇 |
2000年 | 41篇 |
1999年 | 21篇 |
1998年 | 26篇 |
1997年 | 18篇 |
1996年 | 17篇 |
1995年 | 7篇 |
1994年 | 12篇 |
1993年 | 11篇 |
1992年 | 9篇 |
1991年 | 13篇 |
1990年 | 8篇 |
1989年 | 8篇 |
1988年 | 5篇 |
1987年 | 4篇 |
1986年 | 6篇 |
1985年 | 3篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1982年 | 2篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1976年 | 2篇 |
1962年 | 3篇 |
1961年 | 1篇 |
1954年 | 1篇 |
1936年 | 1篇 |
排序方式: 共有1839条查询结果,搜索用时 261 毫秒
51.
52.
Yibo Zhang Prof. Yuying Zheng Prof. Hongbo Geng Dr. Yang Yang Dr. Minghui Ye Dr. Yufei Zhang Prof. Cheng Chao Li 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(35):9031-9037
Metal phosphates have been widely explored in lithium ion batteries and sodium ion batteries owing to high theoretical capacities, mild toxicity and low cost. However, their potassium ion battery applications are less reported due to the limited conductivity and the slow diffusion kinetics. Considering these drawbacks, novel structured M2P2O7/C (M=Fe, Co, Ni) nanoflake composites are prepared through an organic-phosphors precursor-assisted solvothermal method and a subsequent high temperature annealing process. The designed Co2P2O7/C composite exhibits the highest rate capacity with 502 mAh g−1 at 0.1 A g−1 and good cyclability for 900 cycles at 1 A g−1 and 2 A g−1 when compared with Ni and Fe based composites. The superior electrochemical performance can be attributed to their unique nanoparticle-assembled nanoflake structure, which can afford enough active sites for K+ intercalation. In addition, the robust pyrophosphate crystal structure and the in situ formed carbon composition also have positive effects on enhancing the long-term cycling performance and the electrode's conductivity. Finally, this organic-phosphors precursor induced simple approach can be applied for easy fabrication of other pyrophosphate/carbon hybrids as advanced electrodes. 相似文献
53.
The intent of this study is to examine nonequilibrium heat transfer in a copper-argon nanofluid by molecular dynamics simulation. Two different methods, the physical definition method and the curve fitting method, are introduced to calculate the coupling factor between nanoparticles and base fluid. The results show that the coupling factors obtained by these two methods are consistent. The coupling factor is proportional to the volume fraction of the nanoparticle and inversely proportional to nanoparticle diameter. In the temperature range of 90-200 K, the coupling factor is not affected by temperature. The nanoparticle aggregation results in a decrease of the coupling factor. 相似文献
54.
A versatile wet chemistry method is developed for filling of subnanometer sized metal particles in carbon nanotubes with a diameter smaller than 1.5 nm. As an example, we showed that a confined bi-component Pd-V catalyst exhibit a higher benzene hydroxylation activity compared with that within multi-walled carbon nanotubes. 相似文献
55.
56.
57.
Novel thiazolidin-4-one linked pseudo-aza-disaccharides and thiazolidin-4-ones containing C-pseudo-aza-nucleosides were synthesized via a one-pot three component reaction. The former was synthesized stereoselectively by the tandem Staudinger/aza-Wittig/cyclization reaction of azasugar aldehyde 1, an azidosugar, and mercaptoacetic acid. The reaction was structure and temperature controlled, and could be performed stereospecifically under 40 °C. It was the first report of a stereospecific synthesis of thiazolidin-4-one linked derivatives. However, these derivatives were synthesized with low stereoselectivity by involving the condensation reaction of azasugar aldehyde 1, aniline, and mercaptoacetic acid. 相似文献
58.
Qinghua Xie Xia Li Guanquan Wang Xuan Hou Yujun Wang Hongbo Yu Changfa Qu Shunzhong Luo Yali Cui Chuanqin Xia Ruibing Wang 《Journal of Radioanalytical and Nuclear Chemistry》2017,311(3):1697-1708
Here we reported the radiolabeling and evaluation of a novel 131I-radiolabeled quercetin for the treatment of dedifferentiated thyroid cancers. The human thyroid cancer cell lines (FTC-133, TT and DRO) experienced much higher uptake of 131I-quercetin as compared to the free 131I. And the proliferation inhibition rate of 131I-quercetin on in vitro DRO cell line was 86.87 ± 7.15%. Biodistribution and SPECT analysis demonstrated that the injected radioactivity mainly accumulated in tumors. The tumor volume in the treatment group was dramatically inhibited in comparison with the control group. 相似文献
59.
60.
锡二硫族化合物可以通过改变硫和硒的含量来连续调控三元合金材料的带隙、载流子浓度等物理化学性质,在电子和光电子器件应用上具有巨大的潜力。本文采用化学气相沉积(CVD)技术可控地制备了不同元素组分的SnSxSe2-x(x=0,0.2,0.5,0.8,1.0,1.2,1.5,1.8,2.0)单晶纳米片。采用扫描电子显微镜(SEM)、原子力显微镜(AFM)、能量色散X射线光谱(EDS)、透射电子显微镜(TEM)以及拉曼光谱等手段对SnSxSe2-x纳米片进行了综合表征。结果表明本方法成功实现了元素百分比可调的SnSxSe2-x单晶纳米片的可控制备。重点研究了依赖于元素百分比的SnSxSe2-x的拉曼特征谱,实验结果与基于密度泛函理论(DFT)的第一性原理计算得到的SnSxSe2-x的拉曼仿真谱高度吻合,理论计算结果较好地诠释了实验拉曼光谱发生变化的原因。本研究提供了一种元素百分比可调的三元SnSxSe2-x单晶纳米片的可控制备方法,同时对锡二硫族化合物的明确、无损识别提供了方案。 相似文献