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   658篇
  免费   19篇
  国内免费   5篇
化学   546篇
晶体学   9篇
力学   5篇
综合类   1篇
数学   12篇
物理学   109篇
  2021年   6篇
  2020年   11篇
  2019年   3篇
  2018年   8篇
  2017年   8篇
  2016年   8篇
  2015年   5篇
  2014年   15篇
  2013年   22篇
  2012年   30篇
  2011年   28篇
  2010年   20篇
  2009年   20篇
  2008年   31篇
  2007年   38篇
  2006年   47篇
  2005年   50篇
  2004年   44篇
  2003年   37篇
  2002年   34篇
  2001年   3篇
  2000年   15篇
  1999年   9篇
  1998年   11篇
  1997年   9篇
  1996年   6篇
  1995年   8篇
  1994年   11篇
  1993年   12篇
  1992年   11篇
  1991年   8篇
  1990年   7篇
  1989年   13篇
  1988年   5篇
  1987年   11篇
  1986年   13篇
  1985年   16篇
  1984年   6篇
  1983年   3篇
  1982年   4篇
  1981年   1篇
  1980年   3篇
  1979年   3篇
  1978年   2篇
  1976年   6篇
  1975年   5篇
  1974年   5篇
  1973年   7篇
  1972年   1篇
  1970年   1篇
排序方式: 共有682条查询结果,搜索用时 15 毫秒
141.
In the multicolor photochromism of TiO2 nanoporous films loaded with photocatalytically deposited Ag nanoparticles, visible light-induced electron transfer from Ag to oxygen molecules plays an essential role. Here we examined the effect of TiO2 on the electron transfer. We found that not only photocatalytically deposited Ag, but also electrodeposited Ag and commercially available Ag nanoparticles in a nanoporous TiO2 film exhibit the multicolor photochromism. The electrodeposited Ag exhibits the multicolor photochromism also in a nanoporous ZnO film, but not in nanoporous indium-tin oxide (ITO) and SiO2 matrices. Photoelectrochemical measurements for the Ag-TiO2 nanocomposite elucidated that some of the photo-excited electrons on Ag are transferred to oxygen molecules via TiO2 and non-excited Ag. Thus, an n-type semiconductor plays an important role in the charge separation between the excited electrons and Ag+. Non-excited Ag on TiO2 also plays an important role in the charge separation and/or catalysis of oxygen reduction. Replacement of the non-excited Ag with Pt accelerated the electron transport from the photo-excited Ag to oxygen molecules and the photochromic behavior.  相似文献   
142.
Two norcarotenoids, 1 and 2, related to peridinin (3) were isolated from the cultured dinoflagellate of the genus Symbiodinium, a symbiont of the Okinawan soft coral Clavularia viridis, which contains in abundance antitumor marine prostanoids such as clavulones. The structures of 1 and 2 were elucidated on the basis of spectroscopic analysis. These compounds showed significant growth-inhibitory activity in vitro toward cancer cells. Analysis of fatty acids of the dinoflagellate was also carried out, suggesting that the marine prostanoids are produced by the host soft coral itself.  相似文献   
143.
A new catalytic regioselective one-pot synthesis of hydroxyl-capped polyolefins is reported. This synthesis employs a new stereorigid bridged metallocene having an indenyl and a fluorenyl ligand named IF catalyst 1, exhibiting high catalytic performances. Here, we report on (1) the first example of allyl alcohol incorporation into the nonpolar polymer backbone using IF catalyst 1 and methylaluminoxane with high activity, high molecular weight, and high polar monomer uptake at high temperature, and (2) the first example of predominant end-site-selective introduction of an alcohol group into the polyolefins. Moreover, we observed the mixed regioselectivity by the type of alkylaluminum.  相似文献   
144.
New aliphatic polyester-type dendrimers were synthesized using a new AB2-type building block 3, prepared from benzyl acetoacetate and 2 equiv of tert-butyl acrylate by acetoacetic acid ester synthesis. The reiterative [deprotection by HCO2H, then EDCI/DMAP coupling] sequence using divergent growth method gave [G1]-4tBu-[G5]-64tBu dendrimers. 13C NMR relaxation time (T1) measurements on the carboxy carbons show that the extended chain conformations are predominant in CDCl3. [structure: see text]  相似文献   
145.
Influenza is an acute respiratory disease caused by the influenza virus. The disease occurs annually, causing fatality in the elderly and children and billions of dollars loss in business and productivity. Traditional viral detection methods include MDCK cell culture, complement fixation, hemagglutinin-inhibition, and recently RT-PCR. Although effective, these methods generally involve labor-intensive laboratory procedures and often require trained personnel to carry them out. The development of biosensor technologies will enable rapid and specific disease diagnosis on-site so that a clinician can quickly determine whether treatment is needed. This paper reviews traditional viral assays and progress in the biosensor development for influenza virus. Recent advances in single-step direct detection using non-labeling techniques such as surface plasmon resonance, quartz-crystal microbalance, and colorimetric functional polymers are discussed.  相似文献   
146.
The complexation behavior of 6-amino-6-deoxy-γ-cyclodextrin (CD), 6A,6X-diamino-6A,6X-deoxy-γ-CDs and 3A-amino-3A-deoxy-altro-γ-CD with 2-anthracenecarboxylic acid (AC) was studied by NMR, UV–vis and circular dichroism spectroscopy. These modified γ-CD derivatives were found to form stable 1:2 host-guest ternary complexes with AC in aqueous solution. Compared with native γ-CD, the primary-face-aminated γ-CDs exhibited remarkably enhanced overall association constants as a result of the additional electrostatic interactions between the oppositely charged host and guest. In contrast, the ternary complex formation of the secondary-face-aminated γ-CD with AC was hindered.  相似文献   
147.
Dihydropyrazolo[5, 1-c][1, 2, 4]triazines 6, 7 and 8 were found to predominate as the 4, 6-dihydro tautomeric form in solution by the measurement of ID NOE different spectra.  相似文献   
148.
The dithia[3.3]pyridinophane consisting of two pyridine rings has been found out to assume the syn-structure by the X-ray crystallography, meaning the two nitrogen atoms point in the same direction. From this cyclophane and cis-protected palladium(II), the self-assembled coordination molecular cage has been constructed.  相似文献   
149.
150.
Das  Kaustav  Yuasa  Tomonori  Nishidate  Izumi  Funamizu  Hideki  Aizu  Yoshihisa 《Optical Review》2020,27(2):233-245
Optical Review - This paper presents a numerical study on simulated spectra and point spread functions in the database that we constructed by moderate grouping of nine layers in a skin model. The...  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