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   224833篇
  免费   19018篇
  国内免费   10484篇
化学   137429篇
晶体学   3138篇
力学   11604篇
综合类   538篇
数学   23853篇
物理学   77773篇
  2023年   2249篇
  2022年   3361篇
  2021年   4111篇
  2020年   4784篇
  2019年   4627篇
  2018年   4010篇
  2017年   3683篇
  2016年   6176篇
  2015年   5630篇
  2014年   7026篇
  2013年   12184篇
  2012年   12404篇
  2011年   13888篇
  2010年   8982篇
  2009年   8505篇
  2008年   10255篇
  2007年   9782篇
  2006年   9313篇
  2005年   8342篇
  2004年   6686篇
  2003年   5704篇
  2002年   5363篇
  2001年   5403篇
  2000年   4344篇
  1999年   4188篇
  1998年   3664篇
  1997年   3525篇
  1996年   3646篇
  1995年   3250篇
  1994年   2980篇
  1993年   2675篇
  1992年   2796篇
  1991年   2703篇
  1990年   2440篇
  1989年   2230篇
  1988年   2135篇
  1987年   2044篇
  1986年   1954篇
  1985年   2448篇
  1984年   2497篇
  1983年   2039篇
  1982年   2345篇
  1981年   2125篇
  1980年   2147篇
  1979年   2098篇
  1978年   2213篇
  1977年   2117篇
  1976年   2145篇
  1975年   2084篇
  1973年   2133篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
In order to investigate the characteristics of force chains in a granular flow system, a parallel plate shear cell is constructed to simulate the shear movement of an infinite parallel plate and observe variations in relevant parameters. The shear dilatancy process is divided into three stages, namely, plastic strain, macroscopic failure, and granular recombination. The stickslip phenomenon is highly connected with the evolution of force chains during the shear dilatancy process. The load–distribution rate curves and patterns of the force chains are utilized to describe the load-carrying behaviors and morphologic changes of force chains separately. Force chains, namely, “diagonal gridding,” “tadpole-shaped,” and “pinnate” are defined according to the form of the force chains in the corresponding three stages.  相似文献   
72.
73.
Following colonisation of South America by the Spanish, many new naturally occurring substances were sent to Europe. One of these was the silvery, unreactive metal, platinum, discovered in New Grenada in the mid-eighteenth century. It was often found in granular form, associated with gold, and the challenge to chemists was to refine it, produce it as wire or sheet, and determine its chemical properties. This interested the professor of chemistry at the University of Edinburgh, Joseph Black, who was able to obtain samples from London-based Spanish contacts, particularly Ignacio Luzuriaga. This paper examines how Black transmitted his knowledge of the metal to large numbers of students attending his annual course.  相似文献   
74.
75.
76.
77.
78.
Journal of Thermal Analysis and Calorimetry - Over the last few decades, tremendous consideration is drawn towards corrugation surfaces because of their advantages over the improvement in thermal...  相似文献   
79.
Yin  Pengpeng  Liu  Chang  Wang  Ying  Guan  Lei  Chen  Xian  Xiong  Xuejia  Jin  Hongzhe 《Russian Journal of General Chemistry》2021,91(5):897-903
Russian Journal of General Chemistry - A dinuclear Tb complex, Tb2(H2L)3(phen)2 (1), and two similar N-donor coordination complexes, Fe(phen)3·HL (2), Fe(bipy)3·HL·5H2O (3) (Na2H2L =...  相似文献   
80.
Photoactivated chemotherapy (PACT) has appealing merits over traditional chemotherapy as well as photodynamic therapy (PDT) by virtue of its spatial and temporal control on drug activity and oxygen-independent mechanisms of action. However, the short photoactivation wavelengths, e.g., visible light–activated Ru(II)-based PACT agents, limit the clinical application severely. In this work, a facile construction of supramolecular nanoparticles from a poly(ethylene glycol) (PEG)-modified [Ru(dip)2(py-SO3)]+ (abbreviated as Ru-PEG, dip = 4,7-diphenyl-1,10-phenanthroline, py-SO3 = pyridine-2-sulfonate) and 1,3-phenylenebis(pyren-1-ylmethanone) (BP) is shown. While Ru-PEG may undergo photoinduced ligand dissociation and release anticancer species of [Ru(dip)2(H2O)2]2+, BP has extremely large two-photon absorption cross sections (δ2) in the NIR region and intense fluorescence over the wavelengths where Ru-PEG has strong absorption. Thus, two-photon excitation of BP followed by an efficient Förster resonance energy transfer (FRET) from BP to Ru-PEG may lead to a potent inactivation against cisplatin-resistant cancer cells and 3D multicellular tumor spheroids (MCTSs). The residue fluorescence of BP also allows the cellular uptake of the particles to be visualized. This work provides a universal and convenient strategy to realize theranostic PACT in the ideal phototherapeutic window of 650–900 nm.  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