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   503234篇
  免费   5244篇
  国内免费   1660篇
化学   253238篇
晶体学   8241篇
力学   23959篇
综合类   8篇
数学   60659篇
物理学   164033篇
  2021年   4192篇
  2020年   4553篇
  2019年   5160篇
  2018年   6960篇
  2017年   7114篇
  2016年   9963篇
  2015年   5838篇
  2014年   9728篇
  2013年   23396篇
  2012年   17622篇
  2011年   21505篇
  2010年   15661篇
  2009年   15563篇
  2008年   19455篇
  2007年   19402篇
  2006年   18075篇
  2005年   15975篇
  2004年   14864篇
  2003年   13146篇
  2002年   13107篇
  2001年   15338篇
  2000年   11585篇
  1999年   9099篇
  1998年   7615篇
  1997年   7381篇
  1996年   7010篇
  1995年   6224篇
  1994年   6127篇
  1993年   6086篇
  1992年   6562篇
  1991年   6851篇
  1990年   6515篇
  1989年   6370篇
  1988年   6192篇
  1987年   6215篇
  1986年   5817篇
  1985年   7670篇
  1984年   7902篇
  1983年   6427篇
  1982年   6678篇
  1981年   6397篇
  1980年   6203篇
  1979年   6569篇
  1978年   6609篇
  1977年   6586篇
  1976年   6667篇
  1975年   6193篇
  1974年   6166篇
  1973年   6256篇
  1972年   4422篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
131.
132.
Doklady Mathematics - An Erratum to this paper has been published: https://doi.org/10.1134/S1064562421330012  相似文献   
133.
A new derivative of dioxouranium(VI) salen complex, [UO2(L)(pyridine)], where [L = N,N′-Bis(2-hydroxybenzylidene)-2,2-dimethyl-1,3-propanediamine] is synthesized and characterized by elemental analysis (C, H, N), FT-IR, ESI-MS spectrometry, UV/Vis, fluorescence, 1H and 13C NMR spectroscopy and thermal gravimetric (TG) study. Furthermore, the single crystal X-ray diffraction measurements of the complex were carried out at 100 and 273 K. The crystal structure measurements revealed that the complex has distorted pentagonal bipyramidal geometry with uranium atom located at the centre and bonded to two phenoxy oxygen and two azomethine nitrogen in tetradenate fashion and one nitrogen from pyridine making it seven coordinated. In addition, the photoluminescence property of the complex was also recorded.  相似文献   
134.
Russian Journal of Organic Chemistry - A procedure has been proposed for the synthesis of a series of substituted N-(1,3-thiazol-2-yl)-pyrimidin-2-amines and N-(pyrimidin-2-yl)thioureas by...  相似文献   
135.
136.
Saleh  Z. M.  Nasser  H.  Özkol  E.  Günöven  M.  Abak  K.  Canli  S.  Bek  A.  Turan  R. 《Journal of nanoparticle research》2015,17(10):1-12
Journal of Nanoparticle Research - Plasmonic interfaces consisting of silver nanoparticles of different sizes (50–100&;nbsp;nm) have been processed by the self-assembled dewetting...  相似文献   
137.
The biomimetic sol—gel synthesis of silicon—chitosan-containing glycerohydrogels was carried out using silicon tetraglycerolate as a precursor. It was found that chitosan accelerates gel formation in weakly acidic media. In more acidic media, the kinetics of the process changes according to the curve with a maximum, which can be attributed to different mechanisms of silanol condensation before and after the isoelectric point. The investigated silicon—chitosan-containing glycerohydrogels exhibit antibacterial, anti-inflammatory, and wound healing activity. The synthesized hybrid glycerohydrogels are promising materials for biomedical applications.  相似文献   
138.
139.
140.
An innovative volatolomic approach employs the detection of biomarkers present in cerumen (earwax) to identify cattle intoxication by Stryphnodendron rotundifolium Mart., Fabaceae (popularly known as barbatimão). S. rotundifolium is a poisonous plant with the toxic compound undefined and widely distributed throughout the Brazilian territory. Cerumen samples from cattle of two local Brazilian breeds (‘Curraleiro Pé-Duro’ and ‘Pantaneiro’) were collected during an experimental intoxication protocol and analyzed using headspace (HS)/GC–MS followed by multivariate analysis (genetic algorithm for a partial least squares, cluster analysis, and classification and regression trees). A total of 106 volatile organic metabolites were identified in the cerumen samples of bovines. The intoxication by S. rotundifolium influenced the cerumen volatolomic profile of the bovines throughout the intoxication protocol. In this way, it was possible to detect biomarkers for cattle intoxication. Among the biomarkers, 2-octyldecanol and 9-tetradecen-1-ol were able to discriminate all samples between intoxicated and nonintoxicated bovines. The cattle intoxication diagnosis by S. rotundifolium was accomplished by applying the cerumen analysis using HS/GC–MS, in an easy, accurate, and noninvasive way. Thus, the proposed bioanalytical chromatography protocol is a useful tool in veterinary applications to determine this kind of intoxication.  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