全文获取类型
收费全文 | 6358篇 |
免费 | 258篇 |
国内免费 | 125篇 |
专业分类
化学 | 3492篇 |
晶体学 | 35篇 |
力学 | 409篇 |
数学 | 985篇 |
物理学 | 1820篇 |
出版年
2024年 | 7篇 |
2023年 | 60篇 |
2022年 | 116篇 |
2021年 | 153篇 |
2020年 | 331篇 |
2019年 | 218篇 |
2018年 | 382篇 |
2017年 | 493篇 |
2016年 | 393篇 |
2015年 | 422篇 |
2014年 | 605篇 |
2013年 | 923篇 |
2012年 | 636篇 |
2011年 | 522篇 |
2010年 | 340篇 |
2009年 | 259篇 |
2008年 | 143篇 |
2007年 | 113篇 |
2006年 | 116篇 |
2005年 | 83篇 |
2004年 | 47篇 |
2003年 | 44篇 |
2002年 | 43篇 |
2001年 | 73篇 |
2000年 | 26篇 |
1999年 | 83篇 |
1998年 | 49篇 |
1997年 | 36篇 |
1996年 | 21篇 |
1993年 | 1篇 |
1976年 | 2篇 |
1932年 | 1篇 |
排序方式: 共有6741条查询结果,搜索用时 15 毫秒
11.
To construct a class of new multiwave interaction solutions for the (3+1)-dimensional generalized Kadomtsev-Petviashvili equation, we calculate different types of interaction solutions among solitons, periodic waves and rational waves using the direct algebraic method together with the inheritance solving skill. Moreover, a new algorithm is proposed with the aid of the simplified Hirota method, the conjugated parameters assignment and long wave limit strategies, from which multiwave interaction solutions among solitons, breathers and lump waves are generated. 相似文献
12.
13.
14.
Mei Xueqing Li Zhixiong Bagherzadeh Seyed Amin Karimipour Aliakbar Bahrami Mehrdad Karimipour Arash 《Journal of Thermal Analysis and Calorimetry》2021,145(4):2123-2128
Journal of Thermal Analysis and Calorimetry - Artificial neural network/kriging interpolation method optimization method which is evaluated concerned the hybrid nanofluid composed of iron oxide... 相似文献
15.
Efficacy of incorporating PCMs into the commercial wall on the energy-saving annual thermal analysis
Nguyen Quyen Naghieh Alireza Kalbasi Rasool Akbari Mohammad Karimipour Arash Tlili Iskander 《Journal of Thermal Analysis and Calorimetry》2021,143(3):2179-2187
Journal of Thermal Analysis and Calorimetry - In this study, the efficacy of incorporating phase change material (PCM) into the building walls on the annual heat transfer reduction is examined.... 相似文献
16.
Leila Torkian Mostafa M. Amini Tayebeh Gorji Omid Sadeghi 《Arabian Journal of Chemistry》2019,12(7):1315-1321
In this study, multiwalled carbon nanotube (MWCNT) was modified by the pyridine group using a silane agent and characterized by infrared spectroscopy (IR), thermal analysis (TG/DTA), and elemental analysis (CHN) and scanning electron microscopy (SEM). The application of this sorbent was investigated in determination of lead ions in aqueous samples, using flame atomic absorption spectrometry (FAAS). Through this study, different parameters such as pH and sample flow rate on adsorption process and eluent concentration, volume and flow rate were optimized. The limit of detection (LOD), the relative standard deviation and the recovery of the method were 2 ng mL?1, 1.3% and 99.7%, respectively. Two standard reference materials (NIST 1571 and NIST 1572) were used to verify accuracy of this method. Finally, the sorbent was successfully applied for extraction and determination of low levels of Pb(II) ions in aqueous samples. 相似文献
17.
Zheng Yuanzhou Yang Haoran Mazaheri Hossein Aghaei Alireza Mokhtari Namjoo Afrand Masoud 《Journal of Thermal Analysis and Calorimetry》2021,143(2):1425-1438
Journal of Thermal Analysis and Calorimetry - The purpose of this study is to numerically investigate flow field and turbulent heat transfer of hybrid nanofluid, water–DWCNT–TiO2 in a... 相似文献
18.
Nonlinear Dynamics - A robust fixed-time control framework is presented to stabilize flexible spacecraft’s attitude system with external disturbance, uncertain parameters of inertia, and... 相似文献
19.
Zinc polyoxometalate on activated carbon: an efficient catalyst for selective oxidation of alcohols with hydrogen peroxide 下载免费PDF全文
[PW11ZnO39]5? was immobilized on activated carbon and characterized using Fourier transform infrared, X‐ray diffraction, Brunauer–Emmett–Teller and elemental analysis techniques. Effective oxidation of various alcohols with hydrogen peroxide was performed in the presence of this catalyst. Easy separation of the catalyst from the reaction mixture, cheapness, high activity and selectivity, stability as well as retained activity in subsequent catalytic cycles make this supported catalyst suitable for small‐scale synthesis. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
20.
The present study was designed to evaluate the contents of different antioxidants compounds and their antioxidant activities in Jalopeno peppers (Capsicum annuum) cultivars (El Dorido, Grande, Tula, Sayula and El Rey) extracts. Free radical scavenging activity of Grande was recorded as high as 87% followed by El Dorido (83%). Results of reducing power (Fe3+ to Fe2+) showed that Grande (0.85%) and El Dorido (0.81%) fruit extract absorbance value were close to synthetic antioxidant BHT (0. 97%) obtained at100 μg/mL. The results showed that total phenolic content of El Dorido and Grande were significantly higher compared to other Jalapeno pepper. Results indicated strong and positive correlation between antioxidant activity and carotenoids content (r = 0.75), vitamin C (r = 0.78) and total capsaicinoids (r = 0.84), respectively. The results of the antioxidant activity assays showed that the El Dorido and Grande had strongest antioxidant activity compared to other peppers cultivars in this study. 相似文献