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   464篇
  免费   6篇
  国内免费   3篇
化学   296篇
晶体学   2篇
力学   11篇
数学   86篇
物理学   78篇
  2023年   3篇
  2022年   13篇
  2021年   16篇
  2020年   9篇
  2019年   18篇
  2018年   11篇
  2017年   9篇
  2016年   8篇
  2015年   14篇
  2014年   18篇
  2013年   35篇
  2012年   23篇
  2011年   40篇
  2010年   23篇
  2009年   18篇
  2008年   16篇
  2007年   18篇
  2006年   25篇
  2005年   24篇
  2004年   13篇
  2003年   9篇
  2002年   5篇
  2000年   2篇
  1999年   6篇
  1998年   4篇
  1997年   3篇
  1996年   6篇
  1995年   4篇
  1993年   5篇
  1992年   4篇
  1991年   4篇
  1989年   3篇
  1988年   4篇
  1987年   4篇
  1986年   1篇
  1985年   10篇
  1984年   5篇
  1983年   3篇
  1982年   10篇
  1981年   2篇
  1980年   4篇
  1979年   2篇
  1978年   5篇
  1976年   2篇
  1974年   2篇
  1973年   2篇
  1972年   2篇
  1968年   1篇
  1967年   2篇
  1959年   1篇
排序方式: 共有473条查询结果,搜索用时 0 毫秒
101.
Every year, thousands of tons of fruit seeds are discarded as agro-industrial by-products around the world. Fruit seeds are an excellent source of oils, monounsaturated fatty acids, and n-6 and n-3 polyunsaturated essential fatty acids. This study aimed to develop a novel technology for extracting active substances from selected seeds that were obtained after pressing fruit juices. The proposed technology involved sonification with the use of ethyl alcohol at a low extraction temperature. Seeds of four species—blueberry (Vaccinium myrtillus L.), raspberry (Rubus idaeus), cranberry (Vaccinium macrocarpon), and cuckooflower (Cardamine pratensis)—were used for extraction. Following alcohol evaporation under nitrogen, the antioxidant activity, chemical composition, and volatile compounds of the obtained extracts were analyzed using chromatographic methods, including gas chromatography (GC)–mass spectrometry (MS) (GC–MS/MS), and high-performance liquid chromatography–MS. We analyzed physicochemical properties, fatty acid, and volatile compounds composition, sterol and tocochromanol content of blueberry, cranberry, raspberry, and cuckooflower seed oils obtained by sonication. This method is safe and effective, and allows for obtaining valuable oils from the seeds.  相似文献   
102.
The purpose of this study was to explore the effects of roasting linseeds on the pigment, lipid profile, bioactive components, and oxidative stability of the extracted oils. The linseed varieties Giza 11, Giza 12, Sakha 3, and Sakha 6 were roasted at 180 °C for 10 min, and the oils were extracted by cold pressing. The results showed that, after roasting, there was an increase in oil percentage and peroxide value, as well as small increases in p-anisidine and acid values. Roasting also caused an increase in chlorophyll content, while lutein and β-carotene tend to slightly decrease, except in the Giza 11 variety. The total phenolics content was markedly enhanced after roasting. Omega-3 fatty acids were not affected by the roasting process. The total amounts of tocochromanol were found to decrease in the Giza 12 and Sakha 6 varieties after roasting. Plastochromanol-8 increased in all varieties after roasting. The phytosterol composition was minimally affected by roasting. Roasting enhanced the stability of the extracted oils, increasing the induction period and decreasing EC50 values. These results may thus help to discriminate between the different linseed varieties and serve to recommend the use of roasting to enhance the oxidative stability of extracted oil.  相似文献   
103.
1,7-Dihalogenated boron dipyrromethene dyes were successfully synthesized and substituted, thus providing an entry to the final, elusive reactivity pattern. The spectroscopic properties of 1,7-disubstituted BODIPY dyes were studied and are discussed as a function of their structure.  相似文献   
104.
Dynamic adsorption of radiocesium on titanium ferrocyanide grains from reactor coolant simulating solution containing salts at moderate concentrations has been investigated. Effective decontamination of the neutral solutions has been achieved, in the amounts of a more than 20 thousand bed volumes. After adsorption the titanium ferrocyanide was transferred to titanates and calcined at 900 °C. The leaching test of the obtained lithium titanates indicates that the loaded adsorbent can serve as an effective primary barrier in nuclear waste repositories.  相似文献   
105.
106.
Every finite disconnected set P is determined (up to automorphism) by the family {P − {a}:a ∈ Max P }.  相似文献   
107.
108.
The reaction of cinnamonitrile [PhCH?=?CHCN] with arenes in the superacid TfOH at room temperature for 1?h gave two types of compounds, 3-aryl-3-phenyl propionitriles [Ar(Ph)CHCH2CN] and/or 3-phenylindanones in 28–76% yield. The formation of these two reaction products depends on the nucleophilicity of the arene. In these reactions, carbocations generated upon the protonation of cinnamonitrile in TfOH behave as bi-centered electrophiles possessing reactive centers on the C3 carbon of the double bond and on the C1 carbon of the nitrile group.  相似文献   
109.
We analyse ω‐categorical precompact expansions of particular ω‐categorical structures from the viewpoint of amenability of their automorphism groups.  相似文献   
110.
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