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   191148篇
  免费   19726篇
  国内免费   12988篇
化学   104085篇
晶体学   2168篇
力学   13559篇
综合类   785篇
数学   44418篇
物理学   58847篇
  2024年   252篇
  2023年   2163篇
  2022年   3887篇
  2021年   4006篇
  2020年   4558篇
  2019年   4453篇
  2018年   13211篇
  2017年   12785篇
  2016年   11084篇
  2015年   6076篇
  2014年   6756篇
  2013年   8891篇
  2012年   13933篇
  2011年   20753篇
  2010年   12614篇
  2009年   12694篇
  2008年   13896篇
  2007年   15324篇
  2006年   6686篇
  2005年   6676篇
  2004年   5663篇
  2003年   5254篇
  2002年   4214篇
  2001年   2910篇
  2000年   2570篇
  1999年   2606篇
  1998年   2266篇
  1997年   2100篇
  1996年   2281篇
  1995年   1796篇
  1994年   1687篇
  1993年   1406篇
  1992年   1269篇
  1991年   1140篇
  1990年   934篇
  1989年   704篇
  1988年   571篇
  1987年   489篇
  1986年   465篇
  1985年   397篇
  1984年   305篇
  1983年   208篇
  1982年   194篇
  1981年   155篇
  1980年   132篇
  1979年   90篇
  1978年   79篇
  1976年   60篇
  1974年   61篇
  1973年   63篇
排序方式: 共有10000条查询结果,搜索用时 31 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.
74.
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   
75.
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   
76.
Wu  Xuze  Sun  Yu  Wang  Yu  Chen  Yu 《Nonlinear dynamics》2020,99(3):1937-1958
Nonlinear Dynamics - Oblique collisions are more likely to happen in the realistic translational joint with clearance, compared to the full front impacts. It can be a quite demanding task to...  相似文献   
77.
78.
A new approach has been developed to improve SO2 sorption by cyano‐containing ionic liquids (ILs) through tuning the basicity of ILs and cyano–sulfur interaction. Several kinds of cyano‐containing ILs with different basicity were designed, prepared, and used for SO2 capture. The interaction between these cyano‐containing ILs and SO2 was investigated by FTIR and NMR methods. Spectroscopic investigations and quantum chemical calculations showed that dramatic effects on SO2 capacity originate from the basicity of the ILs and enhanced cyano–sulfur interaction. Furthermore, the captured SO2 was easy to release by heating or bubbling N2 through the ILs. This efficient and reversible process, achieved by tuning the basicity of ILs, is an excellent alternative to current technologies for SO2 capture.  相似文献   
79.
80.
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