全文获取类型
收费全文 | 20085篇 |
免费 | 3606篇 |
国内免费 | 2926篇 |
专业分类
化学 | 14434篇 |
晶体学 | 197篇 |
力学 | 1261篇 |
综合类 | 234篇 |
数学 | 2486篇 |
物理学 | 8005篇 |
出版年
2024年 | 14篇 |
2023年 | 461篇 |
2022年 | 542篇 |
2021年 | 733篇 |
2020年 | 891篇 |
2019年 | 867篇 |
2018年 | 705篇 |
2017年 | 725篇 |
2016年 | 1053篇 |
2015年 | 1016篇 |
2014年 | 1131篇 |
2013年 | 1561篇 |
2012年 | 1673篇 |
2011年 | 1880篇 |
2010年 | 1283篇 |
2009年 | 1270篇 |
2008年 | 1358篇 |
2007年 | 1143篇 |
2006年 | 1057篇 |
2005年 | 934篇 |
2004年 | 752篇 |
2003年 | 633篇 |
2002年 | 655篇 |
2001年 | 523篇 |
2000年 | 487篇 |
1999年 | 434篇 |
1998年 | 375篇 |
1997年 | 312篇 |
1996年 | 286篇 |
1995年 | 299篇 |
1994年 | 293篇 |
1993年 | 221篇 |
1992年 | 173篇 |
1991年 | 178篇 |
1990年 | 179篇 |
1989年 | 104篇 |
1988年 | 79篇 |
1987年 | 62篇 |
1986年 | 69篇 |
1985年 | 57篇 |
1984年 | 33篇 |
1983年 | 38篇 |
1982年 | 20篇 |
1981年 | 13篇 |
1980年 | 14篇 |
1979年 | 4篇 |
1978年 | 4篇 |
1975年 | 3篇 |
1957年 | 6篇 |
1936年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
12.
A nanomaterials-based novel molecular beacon has attracted growing attentions in fluorescent assays as many nanomaterials possess excellent quenching efficiency. In this work, a gold-based nanobeacon probe was established to detect organophosphorus pesticides for the first time. The constructed gold-based nanobeacon acted as a signal indicator and could display the decreasing of the intensity in the presence of targets, which competitively bound to single strand DNA. To achieve a high sensitive probe, some parameters including solution pH, temperature and reaction time were investigated and optimized. The gold-based nanobeacon probe assay was proved to be rapid and sensitive to achieve a detection limit of 0.035 μM for isocarbophos, 0.134 μM for profenofos, 0.384 μM for phorate and 2.35 μM for omethoate, respectively. The prepared nanobeacon effectively reduced the background and improved the detection sensitivity and selectivity. The probe is stable, easy to operate and does not need sophisticated instruments. These features makes the probe feasible for screening trace organophosphorus pesticides in real samples. 相似文献
13.
14.
Yongjie Zhou Yuqi Mei Tian Luo Wenxue Chen Qiuping Zhong Haiming Chen Weijun Chen 《Molecules (Basel, Switzerland)》2021,26(9)
The contribution of rheological properties and viscoelasticity of the interfacial adsorbed layer to the emulsification mechanism of enzymatic modified sugar beet pectin (SBP) was studied. The component content of each enzymatic modified pectin was lower than that of untreated SBP. Protein and ferulic acid decreased from 5.52% and 1.08% to 0.54% and 0.13%, respectively, resulting in a decrease in thermal stability, apparent viscosity, and molecular weight (Mw). The dynamic interfacial rheological properties showed that the interfacial pressure and modulus (E) decreased significantly with the decrease of functional groups (especially proteins), which also led to the bimodal distribution of particle size. These results indicated that the superior emulsification property of SBP is mainly determined by proteins, followed by ferulic acid, and the existence of other functional groups also promotes the emulsification property of SBP. 相似文献
15.
16.
Sun Yuan Luo Shunlong Lei Xiangyun 《International Journal of Theoretical Physics》2021,60(9):3211-3224
International Journal of Theoretical Physics - Gram matrices arise naturally in the consideration of pair-wise overlap of a family of vectors or quantum pure states, and play an important role in... 相似文献
17.
18.
随着光伏行业的快速发展, 对硅单晶的品质和长晶装备的稳定性的要求也不断提高。直拉法是生产硅单晶的主要方法,通过提高单晶炉副室的高度以扩大单晶硅的生产规模。由于副室高度的大幅增加,且单晶炉提拉头质心相对于旋转轴心有一定距离,对单晶炉整体稳定性有较大影响,从而降低了单晶硅的生产质量。针对此问题,对单晶炉建立可靠的力学分析模型,采用数值仿真方法,对单晶炉整体进行动力学响应分析,计算得到副室高度增加后的单晶炉工作时中钨丝绳下端晶棒的运动规律以及最大摆动幅度,为改进设计提供依据。数值仿真分析表明提高单晶炉副室高度后,提拉头较大的质心偏心是单晶炉提拉系统发生摆动的主要原因。在此基础上提出在提拉头上添加质心调节装置,通过控制系统调节可保证提拉头质心位置在旋转轴线上以降低提拉系统的摆动。 相似文献
19.
Luo Dajuan Liu Bingqian Gao Rong Su Lixia Su Yonghuan 《Journal of Solid State Electrochemistry》2022,26(3):749-759
Journal of Solid State Electrochemistry - Cortisol, a steroid hormone, has been confirmed as a kind of biomarker that reflects the stress response of psychobiology and related adverse health... 相似文献
20.
Highly dispersed palladium nanoclusters incorporated in amino‐functionalized silica spheres for the selective hydrogenation of succinic acid to γ‐butyrolactone 下载免费PDF全文
Highly dispersed palladium nanoclusters incorporated on amino‐functionalized silica sphere surfaces (Pd/SiO2‐NH2) were fabricated by a simple one‐pot synthesis utilizing 3‐(2‐aminoethylamino)propyltrimethoxysilane (AAPTS) as coordinating agent. Uniform palladium nanoclusters with an average size of 1.1 nm can be obtained during the co‐condensation of tetraethyl orthosilicate and AAPTS owing to the strong interaction between palladium species and amino groups in AAPTS. The palladium particle size can be controlled by addition of AAPTS and plays a significant role in the catalytic performance. The Pd/SiO2‐NH2 catalyst exhibits high catalytic activity for succinic acid hydrogenation with 100% conversion and 94% selectivity towards γ‐butyrolactone using 1,4‐dioxane as solvent at 240°C and 60 bar for 4 h. Moreover, the Pd/SiO2‐NH2 catalyst is robust and readily reusable without loss of its catalytic activity. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献