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   179597篇
  免费   874篇
  国内免费   262篇
化学   89621篇
晶体学   2635篇
力学   9380篇
综合类   7篇
数学   20965篇
物理学   58125篇
  2020年   1850篇
  2019年   2288篇
  2018年   3394篇
  2017年   3524篇
  2016年   4158篇
  2015年   1853篇
  2014年   3588篇
  2013年   7050篇
  2012年   5536篇
  2011年   6592篇
  2010年   5513篇
  2009年   5635篇
  2008年   6367篇
  2007年   6326篇
  2006年   5622篇
  2005年   4984篇
  2004年   4823篇
  2003年   4369篇
  2002年   4526篇
  2001年   5001篇
  2000年   3691篇
  1999年   2825篇
  1998年   2603篇
  1997年   2457篇
  1996年   2253篇
  1995年   2048篇
  1994年   2006篇
  1993年   2038篇
  1992年   2074篇
  1991年   2382篇
  1990年   2319篇
  1989年   2387篇
  1988年   2267篇
  1987年   2300篇
  1986年   2127篇
  1985年   2661篇
  1984年   2674篇
  1983年   2318篇
  1982年   2374篇
  1981年   2275篇
  1980年   2078篇
  1979年   2395篇
  1978年   2547篇
  1977年   2639篇
  1976年   2729篇
  1975年   2536篇
  1974年   2467篇
  1973年   2635篇
  1972年   2152篇
  1971年   1974篇
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
81.
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   
82.
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   
83.
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   
84.
85.
Monodisperse aqueous upconverting nanoparticles (UCNPs) were covalently immobilized on aldehyde modified cellulose paper via reduction amination to develop a luminescence resonance energy transfer (LRET)-based nucleic acid hybridization assay. This first account of covalent immobilization of UCNPs on paper for a bioassay reports an optically responsive method that is sensitive, reproducible and robust. The immobilized UCNPs were decorated with oligonucleotide probes to capture HPRT1 housekeeping gene fragments, which in turn brought reporter conjugated quantum dots (QDs) in close proximity to the UCNPs for LRET. This sandwich assay could detect unlabeled oligonucleotide target, and had a limit of detection of 13 fmol and a dynamic range spanning nearly 3 orders of magnitude. The use of QDs, which are excellent LRET acceptors, demonstrated improved sensitivity, limit of detection, dynamic range and selectivity compared to similar assays that have used molecular fluorophores as acceptors. The selectivity of the assay was attributed to the decoration of the QDs with polyethylene glycol to eliminate non-specific adsorption. The kinetics of hybridization were determined to be diffusion limited and full signal development occurred within 3 min.  相似文献   
86.
Russian Journal of General Chemistry - Thermogravimetry, differential scanning calorimetry, and flow methods were used to investigate thermal properties of a series of cobalt(II)...  相似文献   
87.
88.
89.
90.
Hopersky  A. N.  Nadolinsky  A. M.  Petrov  I. D. 《JETP Letters》2020,111(2):72-75
JETP Letters - The leading role of the bremsstrahlung at resonant Compton scattering of a hard X-ray photon by a multielectron atom has been theoretically predicted. This result can be important in...  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