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   1501篇
  免费   16篇
  国内免费   6篇
化学   838篇
晶体学   3篇
力学   23篇
数学   154篇
物理学   505篇
  2023年   9篇
  2022年   11篇
  2021年   13篇
  2020年   12篇
  2019年   17篇
  2018年   8篇
  2017年   10篇
  2016年   14篇
  2015年   11篇
  2014年   20篇
  2013年   66篇
  2012年   58篇
  2011年   55篇
  2010年   44篇
  2009年   39篇
  2008年   65篇
  2007年   61篇
  2006年   77篇
  2005年   73篇
  2004年   57篇
  2003年   53篇
  2002年   45篇
  2001年   37篇
  2000年   41篇
  1999年   23篇
  1998年   24篇
  1997年   18篇
  1996年   29篇
  1995年   22篇
  1994年   23篇
  1993年   31篇
  1992年   38篇
  1991年   15篇
  1990年   19篇
  1989年   18篇
  1988年   28篇
  1987年   14篇
  1986年   16篇
  1985年   23篇
  1984年   23篇
  1983年   13篇
  1982年   24篇
  1981年   18篇
  1980年   20篇
  1979年   14篇
  1978年   15篇
  1977年   14篇
  1976年   20篇
  1975年   21篇
  1973年   11篇
排序方式: 共有1523条查询结果,搜索用时 15 毫秒
31.
32.
33.
34.
35.
36.
Carbohydrates such as alditols (polyols or sugar alcohols), monosaccharides and disaccharides are separated as anions by anion-exchange chromatography with a sodium hydroxide eluent, MA1 CarboPac column and pulsed amperometric detection. We report a high-pH anion-exchange chromatographic-pulsed amperometric detection (HPAEC-PAD) method that determines all the polyols used as food additives in food products and the most commonly found mono- and disaccharides on a routine basis. The linearity, repeatability, internal reproducibility and accuracy are described. The applicability of the method has been demonstrated by the analysis of 46 relevant samples and by participation twice in the Food Analysis Performance Assessment Scheme (FAPAS) testing programme for food additives.  相似文献   
37.
A reference material for the determination of overall migration from a plastic coextrudate into the fatty food simulant olive oil was produced and certified in an interlaboratory study. The analyses were carried out according to the ENV 1186 standard from the European Committee for Standardization (CEN) [ 1, 2, 3] with exposure of the coextrudate to olive oil for 10 days at 40 degrees C. After an initial preliminary interlaboratory study eight laboratories participated in the certification round, and two different methods were used to obtain single sided exposure of the plastic to the oil. The certified value was determined as the mean of laboratory mean values. No outliers were found. A reference value of 8.6 mg/dm2 +/- 1.4 mg/dm2 (+/- half width of the 95% confidence interval) was obtained which is within the range relevant for the regulatory limit (10 mg/ dm2), making this reference material suitable for laboratories measuring according to the EU overall migration limit [4]. The material has been found stable over 45 months.  相似文献   
38.
Three classes of drugs were screened for analysis feasibility by capillary column supercritical fluid chromatography. These included steroids, therapeutic antibiotic drugs, and drugs of abuse, such as cannabinoids. Supercritical fluid carbon dioxide was used as the mobile phase in conjunction with a methylpolysiloxane stationary phase capillary column and a flame ionization detector. All compounds considered were analyzed either as single component solutions, simple mixtures, or in actual complex mixtures.  相似文献   
39.
40.
[structures: see text] A versatile (S)-3-(hydroxymethyl)butane-1,2,4-triol building block has been synthesized starting from D-isoascorbic acid, a common food preservative. The key transformation in this approach was the introduction of branching through a high yield and fully regioselective epoxide opening. This flexible synthon has been elaborated to a new class of (dihydro-)N-homo(phyto)ceramides.  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