首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   6983篇
  免费   315篇
  国内免费   68篇
化学   5224篇
晶体学   47篇
力学   283篇
综合类   2篇
数学   952篇
物理学   858篇
  2024年   10篇
  2023年   53篇
  2022年   100篇
  2021年   373篇
  2020年   265篇
  2019年   310篇
  2018年   283篇
  2017年   228篇
  2016年   365篇
  2015年   264篇
  2014年   297篇
  2013年   692篇
  2012年   472篇
  2011年   482篇
  2010年   311篇
  2009年   253篇
  2008年   326篇
  2007年   323篇
  2006年   270篇
  2005年   231篇
  2004年   193篇
  2003年   168篇
  2002年   164篇
  2001年   69篇
  2000年   78篇
  1999年   52篇
  1998年   33篇
  1997年   51篇
  1996年   42篇
  1995年   38篇
  1994年   41篇
  1993年   40篇
  1992年   35篇
  1991年   32篇
  1990年   42篇
  1989年   29篇
  1988年   24篇
  1987年   31篇
  1986年   29篇
  1985年   39篇
  1984年   26篇
  1983年   26篇
  1982年   30篇
  1981年   27篇
  1980年   17篇
  1979年   16篇
  1978年   15篇
  1977年   14篇
  1976年   11篇
  1975年   9篇
排序方式: 共有7366条查询结果,搜索用时 140 毫秒
1.
Favipiravir is a potential antiviral medication that has been recently licensed for Covid-19 treatment. In this work, a gadolinium-based magnetic ionic liquid was prepared and used as an extractant in dispersive liquid–liquid microextraction (DLLME) of favipiravir in human plasma. The high enriching ability of DLLME allowed the determination of favipiravir in real samples using HPLC/UV with sufficient sensitivity. The effects of several variables on extraction efficiency were investigated, including type of extractant, amount of extractant, type of disperser and disperser volume. The maximum enrichment was attained using 50 mg of the Gd-magnetic ionic liquid (MIL) and 150 μl of tetrahydrofuran. The Gd-based MIL could form a supramolecular assembly in the presence of tetrahydrofuran, which enhanced the extraction efficiency of favipiravir. The developed method was validated according to US Food and Drug Administration bioanalytical method validation guidelines. The coefficient of determination was 0.9999, for a linear concentration range of 25 to 1.0 × 105 ng/ml. The percentage recovery (accuracy) varied from 99.83 to 104.2%, with RSD values (precision) ranging from 4.07 to 11.84%. The total extraction time was about 12 min and the HPLC analysis time was 5 min. The method was simple, selective and sensitive for the determination of favipiravir in real human plasma.  相似文献   
2.
Journal of Thermal Analysis and Calorimetry - Nanofluids are attractive alternatives for the current heat transfer fluids due to their remarkably higher thermal conductivity which leads to the...  相似文献   
3.
Russian Journal of General Chemistry - Some new fluoro-heterocyclic compounds containing thiazole and pyridine moities have been synthesized and studied for their antiproliferative activity....  相似文献   
4.
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   
5.
Journal of Sol-Gel Science and Technology - High temperature stable brookite rich titanium dioxide of average crystallite size 20&;nbsp;nm has been prepared by a novel aqueous sol–gel...  相似文献   
6.
7.
Research on Chemical Intermediates - A theoretical study on four organic dyes based on bis(4-hexyloxy)triphenylamine as donor and electron acceptor cyanoacrylic acid with a...  相似文献   
8.
In this paper, the deformation of the Heisenberg algebra, consistent with both the generalized uncertainty principle and doubly special relativity, has been analyzed. It has been observed that, though this algebra can give rise to fractional derivative terms in the corresponding quantum mechanical Hamiltonian, a formal meaning can be given to them by using the theory of harmonic extensions of function. Depending on this argument, the expression of the propagator of the path integral corresponding to the deformed Heisenberg algebra, has been obtained. In particular, the consistent expression of the one dimensional free particle propagator has been evaluated explicitly. With this propagator in hand, it has been shown that, even in free particle case, normal generalized uncertainty principle and doubly special relativity show very much different result.  相似文献   
9.
10.
[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   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号