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   540459篇
  免费   4827篇
  国内免费   1385篇
化学   268472篇
晶体学   7646篇
力学   25989篇
综合类   17篇
数学   67781篇
物理学   163532篇
综合类   13234篇
  2021年   5029篇
  2020年   5482篇
  2019年   6226篇
  2018年   8423篇
  2017年   8584篇
  2016年   11652篇
  2015年   6200篇
  2014年   10469篇
  2013年   23524篇
  2012年   18613篇
  2011年   22158篇
  2010年   16525篇
  2009年   16318篇
  2008年   20936篇
  2007年   20912篇
  2006年   18974篇
  2005年   17036篇
  2004年   15897篇
  2003年   14300篇
  2002年   14229篇
  2001年   15386篇
  2000年   11912篇
  1999年   9125篇
  1998年   7610篇
  1997年   7487篇
  1996年   6942篇
  1995年   6267篇
  1994年   6275篇
  1993年   6029篇
  1992年   6679篇
  1991年   7122篇
  1990年   6854篇
  1989年   6770篇
  1988年   6577篇
  1987年   6427篇
  1986年   6109篇
  1985年   7675篇
  1984年   7948篇
  1983年   6691篇
  1982年   6911篇
  1981年   6422篇
  1980年   6106篇
  1979年   6744篇
  1978年   6979篇
  1977年   6823篇
  1976年   6753篇
  1975年   6483篇
  1974年   6430篇
  1973年   6547篇
  1972年   4825篇
排序方式: 共有10000条查询结果,搜索用时 234 毫秒
171.
High-energy assisted extraction techniques, like ultrasound assisted extraction (UAE) and microwave assisted extraction (MAE), are widely applied over the last years for the recovery of bioactive compounds such as carotenoids, antioxidants and phenols from foods, animals and herbal natural sources. Especially for the case of xanthophylls, the main carotenoid group of crustaceans, they can be extracted in a rapid and quantitative way with the use of UAE and MAE.  相似文献   
172.
Molecular dynamics simulation was performed to study the formation of cluster structure, interfaces, and surfaces with different curvature radii in a perfect nanocrystal passed through by a nonlinear wave. It is shown that this process is a type of nanostructure self-organization in response to an external energy flux with subsequent development of a strong rotational field.  相似文献   
173.
Shinkorenko  A. S. 《JETP Letters》2022,116(10):759-759
JETP Letters - An Erratum to this paper has been published: https://doi.org/10.1134/S0021364022400028  相似文献   
174.
Molecular Diversity - Hypertension is a medical condition that affects millions of people worldwide. Despite the high efficacy of the current antihypertensive drugs, they are associated with...  相似文献   
175.
Journal of Solid State Electrochemistry - Due to their distinctive chemical, electronic, and environmental properties, polypyrrole is used as a blocking barrier for methanol leakage in direct...  相似文献   
176.
Popel  S. I.  Golub’  A. P. 《JETP Letters》2022,115(10):596-601
JETP Letters - One of the main features of the dusty plasma compared to the conventional plasma (without charged dust particles is anomalous dissipation that is caused by the charging of dust...  相似文献   
177.
Russian Journal of General Chemistry - Highly dispersed CaO has been synthesized by heating an aqueous solution of calcium nitrate and D-glucose up to 800°C. Calcium oxide is formed with an...  相似文献   
178.
Differential Equations - We consider an initial–boundary value problem for the heat equation in which the heat conduction coefficient and one of the functions occurring in the source depend...  相似文献   
179.
Russian Journal of Organic Chemistry - Methyl (Z)-3-[(2R,3R,4S,5S)-5-(2-methoxy-2-oxoethyl)-3,4-(isopropylidenedioxy)tetrahydrofuran-2-yl]-prop-2-enoate was synthesized, and its intramolecular...  相似文献   
180.
Tetrahydrotetrazoles are five‐membered‐ring heterocycles containing four contiguous saturated nitrogen atoms. Very few examples of such compounds have been reported in the literature. Our previous attempt at the synthesis of a member of this class of compound suggested that the N—N bonds may be more labile than expected. This finding raised the question as to whether the structures of any of the previously reported tetrahydrotetrazoles had been properly assigned. We have reproduced the synthesis of a reported tetrahydrotetrazole, namely 1,2‐di‐tert‐butyl 3‐phenyl‐1H,2H,3H,10bH‐[1,2,3,4]tetrazolo[5,1‐a]isoquinoline‐1,2‐dicarboxylate, C25H30N4O4, and have now confidently confirmed its structure via X‐ray crystallography. However, while sufficiently stable in the crystal phase, we discovered that it remains very labile in solution (having a half‐life of only 15 min at 20 °C in CDCl3). A tentative reaction pathway for its dissociation based on 1H NMR spectral evidence is provided.  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