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   304380篇
  免费   1789篇
  国内免费   648篇
化学   146091篇
晶体学   4317篇
力学   15079篇
综合类   6篇
数学   46567篇
物理学   94757篇
  2020年   1970篇
  2019年   2264篇
  2018年   10953篇
  2017年   11674篇
  2016年   7998篇
  2015年   3112篇
  2014年   3936篇
  2013年   9372篇
  2012年   10877篇
  2011年   19882篇
  2010年   12514篇
  2009年   12561篇
  2008年   17833篇
  2007年   21220篇
  2006年   7819篇
  2005年   12977篇
  2004年   9273篇
  2003年   8887篇
  2002年   6863篇
  2001年   6103篇
  2000年   5004篇
  1999年   3511篇
  1998年   3063篇
  1997年   3054篇
  1996年   2997篇
  1995年   2429篇
  1994年   2505篇
  1993年   2534篇
  1992年   2669篇
  1991年   2733篇
  1990年   2641篇
  1989年   2622篇
  1988年   2560篇
  1987年   2527篇
  1986年   2439篇
  1985年   3126篇
  1984年   3305篇
  1983年   2660篇
  1982年   2926篇
  1981年   2802篇
  1980年   2595篇
  1979年   2831篇
  1978年   2925篇
  1977年   2866篇
  1976年   2867篇
  1975年   2716篇
  1974年   2687篇
  1973年   2876篇
  1972年   1887篇
  1967年   1868篇
排序方式: 共有10000条查询结果,搜索用时 421 毫秒
71.
Vorob’ev  N. T.  Lantsetova  E. D. 《Mathematical Notes》2021,110(5-6):655-665
Mathematical Notes - It is proved that the lattice of all Fitting classes of finite groups is not distributive, and conditions under which Fitting classes satisfy the distributive and modular laws...  相似文献   
72.
Journal of Applied Spectroscopy - Aqueous solutions of human hemoglobin have been studied by the multi-angle static light scattering method. The tendency of sickle-shaped erythrocytes to aggregate...  相似文献   
73.
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   
74.
Russian Journal of Organic Chemistry - Selenopheno[2,3-d]pyrimidine- and selenopheno[2,3-d][1,2,3]triazine-containing compounds were synthesized starting from...  相似文献   
75.
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   
76.
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   
77.
78.
A fully quantitative theory of the relationship between protein conformation and optical spectroscopy would facilitate deeper insights into biophysical and simulation studies of protein dynamics and folding. In contrast to intense bands in the far-ultraviolet, near-UV bands are much weaker and have been challenging to compute theoretically. We report some advances in the accuracy of calculations in the near-UV, which were realised through the consideration of the vibrational structure of the electronic transitions of aromatic side chains.  相似文献   
79.
Russian Journal of Applied Chemistry - Organo-inorganic composite materials based on films of polytetrafluoroethylene and tetrafluoroethylene–hexafluoropropylene copolymer, modified with...  相似文献   
80.
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