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   2317篇
  免费   58篇
  国内免费   6篇
化学   1626篇
晶体学   37篇
力学   19篇
数学   49篇
物理学   650篇
  2022年   8篇
  2021年   15篇
  2020年   23篇
  2019年   26篇
  2018年   21篇
  2017年   11篇
  2016年   40篇
  2015年   34篇
  2014年   49篇
  2013年   92篇
  2012年   73篇
  2011年   88篇
  2010年   52篇
  2009年   62篇
  2008年   135篇
  2007年   105篇
  2006年   131篇
  2005年   122篇
  2004年   146篇
  2003年   104篇
  2002年   81篇
  2001年   59篇
  2000年   42篇
  1999年   48篇
  1998年   22篇
  1997年   26篇
  1996年   41篇
  1995年   43篇
  1994年   35篇
  1993年   27篇
  1992年   54篇
  1991年   46篇
  1990年   28篇
  1989年   34篇
  1988年   24篇
  1987年   33篇
  1986年   34篇
  1985年   34篇
  1984年   20篇
  1983年   16篇
  1982年   29篇
  1981年   30篇
  1980年   31篇
  1979年   23篇
  1978年   22篇
  1977年   19篇
  1976年   14篇
  1975年   23篇
  1974年   20篇
  1973年   26篇
排序方式: 共有2381条查询结果,搜索用时 171 毫秒
71.
N,N-dimethyl-N,N-dihexyl-3-oxapentanediamide, DMDHOPDA, N,N-dihexyl-3-thiopentanediamide, DHTPDA and N,N-dihexyl-3-oxapentanediamide, DHOPDA were synthesized and tested for the synergistic extraction of Eu3+, Th4+, UO 2 2+ , NpO 2 + and Am3+ with thenoyltrifluoroacetone (HTTA). Although Eu3+, Th4+, UO 2 2+ and Am3+ were not extracted by DHTPDA or DHOPDA alone, they were extracted synergistically when combined with HTTA. Analysis of the dependency of extraction on pH and extractant concentration indicated that the dominant extracted species were Eu(TTA)3(A), Th(TTA)3(A)(X), UO2(TTA)2(A) and Am(TTA)3(A) (where A is diamide, and X is chloroacetate or ClO 4 ).  相似文献   
72.
γ-Ray-induced polymerizations of ferrocenylmethyl methacrylate (FMMA) in crystalline and amorphous states were investigated with kinetical and ESR methods. In the crystalline state the polymerization of FMMA proceeded slowly and gave low-molecular-weight polymers, whereas in the amorphous state it proceeded rapidly and gave polymers of much higher molecular weight. Molecular weight distributions of these polymers were binodal. The temperature dependence and the dose-rate dependence of the polymerization rates were different between the two states. Wide-line nuclear magnetic resonance (NMR) spectra of the amorphous monomer suggested that the polymerization proceeded in a supercooled state. Electron spin resonance (ESR) spectra of γ-irradiated FMMA and 1,1′-ferrocenyl-di(methyl methacrylate) showed that ferrocene radicals and methacrylic radicals were formed simultaneously at low temperature; with increasing temperature the former radicals disappeared, whereas the latter changed into growing chain radicals. The yields of radicals were relatively low; this means that ferrocene groups in the monomers behave as a radiation energy absorber.  相似文献   
73.
In order to study how the bile salts and lipids behave in the vicinity of microvillus, the transport properties of a sodium salt of deoxycholic acid (NaDC) and its mixture with monooleoylglycerol (MO) through artificial membranes were investigated in 0.15 M NaCl saline solution at 37°C.The hydrodynamic radius of MO-solubilized micelles was estimated to be approximately 17–20 Å from the transport study. The thermodynamically stable MO-NaDC mixed micelles formed above critical micelle concentration in the higher region of mole fraction of NaDC in the mixture (X NaDC>ca. 0.6), can behave as a single species in transport process and freely pass through the porous membranes of both pore sizes, 0.01 m and 0.1 m.The permeabilities of MO-NaDC mixed micelles are large compared with those of pure NaDC micelles. MO molecules solubilized may probably enhance the interaction between MO and NaDC molecules by better contacting with the respective hydrophobic groups in a mixed micelle (the flexible structure of MO molecule enables it), and in this situation, the smaller micelles compared with those of pure NaDC must be more favorable.  相似文献   
74.
75.
76.
77.
78.
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