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   2949篇
  免费   133篇
  国内免费   22篇
化学   2003篇
晶体学   6篇
力学   121篇
数学   299篇
物理学   675篇
  2023年   20篇
  2022年   27篇
  2021年   95篇
  2020年   83篇
  2019年   58篇
  2018年   65篇
  2017年   43篇
  2016年   130篇
  2015年   84篇
  2014年   90篇
  2013年   160篇
  2012年   148篇
  2011年   215篇
  2010年   133篇
  2009年   91篇
  2008年   149篇
  2007年   144篇
  2006年   151篇
  2005年   142篇
  2004年   101篇
  2003年   108篇
  2002年   86篇
  2001年   60篇
  2000年   83篇
  1999年   52篇
  1998年   26篇
  1997年   26篇
  1996年   36篇
  1995年   28篇
  1994年   35篇
  1993年   35篇
  1992年   25篇
  1991年   30篇
  1990年   16篇
  1989年   29篇
  1988年   17篇
  1987年   12篇
  1986年   12篇
  1985年   22篇
  1984年   18篇
  1983年   13篇
  1982年   15篇
  1981年   12篇
  1980年   13篇
  1979年   13篇
  1978年   11篇
  1976年   18篇
  1975年   11篇
  1974年   10篇
  1973年   13篇
排序方式: 共有3104条查询结果,搜索用时 356 毫秒
961.
Ricerche di Matematica - We prove that some of the main results of linkage theory can be extended to a more general context in homological algebra. Our main result states that, under suitable...  相似文献   
962.
Induced pluripotent stem cells (IPSC) are preferred as an alternative source for regenerative medicine, disease modeling, and drug screening due to their unique properties. As seen from the previous studies in the literature, most of the vector systems to transfer reprogramming factors are viral-based and have some well-known limitations. This study aims to develop a non-viral vector system for the transfection of reprogramming factors. Cationic stearamide lipid nanoparticles (CSLN) were prepared via the solvent diffusion method. The obtained CSLNs were used for the delivery of plasmid DNA (pDNA) encoding Oct3/4, Sox2, Klf4, and GFP to fibroblast cell lines. The optimization studies, for zeta potential and particle size of the conjugate, was performed to achieve high cell viability. CSLN63 with 36.5±0.06 mV zeta potential and 173.6±13.91 nm size was used for the transfection of Fibroblast cells. The transfection efficiency was observed by following GFP expression and was found as 70 %±0.11. The expression of the Oct4, Sox2, Klf4 was determined by RT-qPCR; an increase was observed after the 12th cycle in Klf4 (Ct averages: 13,41), Sox2 (Ct averages; 12,4), Oct4 (Ct average; 13,77). The tendency of colonization was observed. The upregulation efficiency of Oct4 and SSEA-1 with CSLN and another non-viral vector designed for the transportation of Yamanaka factors developed in our lab previously were compared with flow cytometer analysis.  相似文献   
963.
964.
Li-ion batteries (LIBs) are the most employed power source in portable electronics (e.g., cellular phones, laptop computers…) and are accounted as very promising storage/power systems for future electric/hybrid-electric powered transportation. However for their future development, low production costs and environmental friendliness will be key parameters. In this context, the introduction of water processable biosourced polymers such as cellulose and its derivatives is very interesting and is emerging as a viable route toward the development of green materials and processes for LIB manufacturing. The present review briefly introduces the Li-ion technology and gives an overview on cellulose and cellulose derivatives for the elaboration of separators, electrolytes and electrodes.  相似文献   
965.
Dichromate binds to surface‐active maghemite nanoparticles (SAMNs) to form a stable core–shell nanostructures (SAMN@CrVI). The hybrid was characterized by Mössbauer spectroscopy, high‐angle annular dark‐field imaging, electron energy‐loss spectroscopy, and electrochemical techniques, which revealed a strong interaction of dichromate with the nanoparticle surface. Electrochemical characterization showed lower charge‐transfer resistance, better electrochemical performance, and more reversible electrochemical behavior with respect to naked SAMNs. Moreover, SAMN@CrVI is an excellent electrocatalyst for hydrogen peroxide reduction. Furthermore, an enzyme, namely, bovine serum amine oxidase (BSAO: EC 1.4.3.6), was immobilized on SAMN@CrVI by self‐assembly to give a ternary hybrid nanostructured catalyst for polyamine oxidation (SAMN@CrVI‐BSAO). SAMN@CrVI‐BSAO was applied for the development of a reagentless, fast, inexpensive, and interference‐free polyamine biosensor, which was successfully exploited for the discrimination of tumorous tissue from healthy tissue in human crude liver extracts.  相似文献   
966.
967.
968.
969.
970.
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