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   1348667篇
  免费   46189篇
  国内免费   20238篇
化学   687377篇
晶体学   15838篇
力学   79157篇
综合类   825篇
数学   248366篇
物理学   383531篇
  2021年   16209篇
  2020年   19398篇
  2019年   20589篇
  2018年   13588篇
  2016年   31366篇
  2015年   25067篇
  2014年   35845篇
  2013年   81447篇
  2012年   43038篇
  2011年   37399篇
  2010年   41252篇
  2009年   44140篇
  2008年   35697篇
  2007年   29415篇
  2006年   37389篇
  2005年   27936篇
  2004年   29521篇
  2003年   28088篇
  2002年   29983篇
  2001年   26955篇
  2000年   24728篇
  1999年   23369篇
  1998年   22079篇
  1997年   22044篇
  1996年   22319篇
  1995年   20187篇
  1994年   18976篇
  1993年   18202篇
  1992年   17577篇
  1991年   17835篇
  1990年   16983篇
  1989年   16950篇
  1988年   16449篇
  1987年   16460篇
  1986年   15306篇
  1985年   21838篇
  1984年   23220篇
  1983年   19379篇
  1982年   21149篇
  1981年   20388篇
  1980年   19673篇
  1979年   19759篇
  1978年   21195篇
  1977年   20795篇
  1976年   20478篇
  1975年   19139篇
  1974年   18749篇
  1973年   19299篇
  1972年   13826篇
  1967年   12256篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Journal of Radioanalytical and Nuclear Chemistry - Eco-friendly and low-cost composite, amidoxime-functionalized microcrystalline cellulose/mesoporous silica (MCC/MS-AO), were synthesized by...  相似文献   
2.
Journal of Experimental and Theoretical Physics - Dzyaloshinskii–Moriya interaction, DMI in short, represents an antisymmetric type of magnetic interactions that favor orthogonal orientation...  相似文献   
3.
Journal of Fluorescence - This report describes a combined immunofluorescence and fluorescence viability stain applied as one staining solution for rapid detection of live Legionella...  相似文献   
4.
5.
Kinetics and Catalysis - The catalytic properties of a nickel phosphide catalyst supported on silica gel in the reductive amination of carbonyl compounds were studied in a flow reactor using...  相似文献   
6.
In this study, the transverse relaxation time (T2) of activated carbon (AC) in different relative environment humidity was detected firstly by low-field nuclear magnetic resonance (LFNMR). The pore size (diameter) of AC distributions was calculated by the relationship between T2 and surface relaxation rate (ρ), where ρ was obtained by the detection of nine porous materials with known pore size. The results showed that the pore size distributions of AC calculated by ρ < 0.19 nm/ms were in good agreement with that obtained by nitrogen adsorption method and proved that LFNMR as a new detection method was feasible for characterizing AC pore size distribution.  相似文献   
7.
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   
8.
Yang  T. L.  Kao  C. L.  Kuo  C. E.  Yeh  H. C.  Li  W. J.  Li  H. T.  Chen  C. Y. 《Chemistry of Natural Compounds》2022,58(5):825-827
Chemistry of Natural Compounds - A novel bibenzyl derivative, hydrangchinenin (1), was isolated from the stems of Hydrangea chinensis Maxim. (Hydrangeaceae). Its structure was determined on the...  相似文献   
9.
Zhang  Hongchi  Liu  Rui  Li  Hui  Yang  Yang  Zhou  Feng 《Chemistry of Natural Compounds》2022,58(3):541-544
Chemistry of Natural Compounds -  相似文献   
10.
Chromatographia - We developed a simple, rapid, ecological RP-HPLC method for the estimation of Pitavastatin (PIT), Fenofibrate (FEN), and their impurities in a novel fixed dose combination. We...  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