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   1338937篇
  免费   34331篇
  国内免费   10847篇
化学   670349篇
晶体学   15849篇
力学   76003篇
综合类   244篇
数学   244070篇
物理学   377600篇
  2021年   14352篇
  2020年   16947篇
  2019年   17190篇
  2018年   13533篇
  2016年   29084篇
  2015年   21961篇
  2014年   31976篇
  2013年   76448篇
  2012年   39640篇
  2011年   36319篇
  2010年   38440篇
  2009年   40840篇
  2008年   35068篇
  2007年   30503篇
  2006年   36445篇
  2005年   28848篇
  2004年   29821篇
  2003年   28130篇
  2002年   29317篇
  2001年   27711篇
  2000年   24515篇
  1999年   22670篇
  1998年   21366篇
  1997年   21396篇
  1996年   21525篇
  1995年   19568篇
  1994年   18929篇
  1993年   18415篇
  1992年   18204篇
  1991年   17874篇
  1990年   16999篇
  1989年   17045篇
  1988年   16597篇
  1987年   16620篇
  1986年   15509篇
  1985年   22041篇
  1984年   23379篇
  1983年   19494篇
  1982年   21248篇
  1981年   20478篇
  1980年   19798篇
  1979年   20010篇
  1978年   21376篇
  1977年   20995篇
  1976年   20747篇
  1975年   19418篇
  1974年   19066篇
  1973年   19577篇
  1972年   14092篇
  1967年   12524篇
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
1.
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   
2.
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   
3.
4.
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   
5.
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   
6.
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   
7.
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   
8.
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   
9.
Kinetics and Catalysis - A new ruthenium(II) cage complex with polar terminal groups in the apical substituents has been synthesized; the molecular design of the complex contributes to the...  相似文献   
10.
Zhang  Bing  Yang  Jie-qin  Liu  Ying  Hu  Bin  Yang  Yang  Zhao  Li  Lu  Qiang 《Cellulose (London, England)》2022,29(12):6565-6578
Cellulose - Heating is essential in various biomass pre-treatments and thermal conversion processes. It is of practical significance to study the characteristics of cellulose-lignin and...  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