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   3379篇
  免费   86篇
  国内免费   16篇
化学   2451篇
晶体学   36篇
力学   31篇
数学   126篇
物理学   837篇
  2022年   24篇
  2021年   23篇
  2020年   35篇
  2019年   54篇
  2018年   23篇
  2017年   25篇
  2016年   57篇
  2015年   58篇
  2014年   65篇
  2013年   144篇
  2012年   171篇
  2011年   168篇
  2010年   105篇
  2009年   100篇
  2008年   180篇
  2007年   162篇
  2006年   183篇
  2005年   147篇
  2004年   168篇
  2003年   137篇
  2002年   114篇
  2001年   86篇
  2000年   67篇
  1999年   45篇
  1998年   30篇
  1997年   34篇
  1996年   54篇
  1995年   51篇
  1994年   35篇
  1993年   46篇
  1992年   55篇
  1991年   41篇
  1990年   31篇
  1989年   37篇
  1988年   42篇
  1987年   36篇
  1986年   24篇
  1985年   72篇
  1984年   61篇
  1983年   41篇
  1982年   49篇
  1981年   42篇
  1980年   37篇
  1979年   36篇
  1978年   38篇
  1977年   38篇
  1976年   33篇
  1975年   31篇
  1973年   29篇
  1966年   17篇
排序方式: 共有3481条查询结果,搜索用时 0 毫秒
31.
32.
33.
The gyromagnetic ratios of the 4 1 + , 6 1 + , and 2 2 + states in186W were measured relative to that of the 2 1 + level by means of the transient field implantation perturbedγ-ray angular distribution technique. The nuclei in the states of interest were Coulomb excited using a beam of 220-MeV63Cu projectiles and recoiled swiftly through a thin, polarized Fe foil. The present measurements yielded ratiosg(4 1 + )/g(2 1 + )=1.04±0.07,g(6 1 + )/g(2 1 + )=1.03 ±0.20 andg(2 2 + )/g(2 1 + )=0.63±0.13. The sizable disparity between the measuredg-factors of the ground- and excited-band is examined within the context of the interacting boson approximation model.  相似文献   
34.
In order to investigate the enzyme model reaction the oxidation of 3,4-dihydihydroxy-L-phenylalanine(L-DOPA) was carried out using optically active catalyst, N-lauroyl L or D-histidine-Cu(II) complex(L or D-LauHis-Cu(II)), showing appreciable enantioselectivity in the presence of the mixed micelles with CTABr.  相似文献   
35.
The UV-induced photochemical reactions of pentacarbonyliron with ethene in a low temperature nitrogen matrix were studied by means of the Mössbauer technique. Fe/CO/4/C2H4/ was produced by UV-irradiation of penfacarbonyliron in close proximity to ethene molecules in a pure ethene matrix, or a homogeneous cocondensed matrix. The other products were obtained via thermal reactions with ethene of Fe/CO/4 trapped in stratified matrices.  相似文献   
36.
Radical polymerization and copolymerization of some o-alkylphenyl methacrylates were carried out and the effect of the ortho-substituents on the ability to homopolymerize, on the monomer reactivities, and on the ceiling temperatures of the monomers was studied. The effect of the substituent on tacticities and thermal stabilities of the polymers formed was also discussed. The ability to honiopolymerize and the monomer reactivity were considerably decreased by the introduction of the o-substituent. 2,6-Di-tert-butylphenyl methacrylate formed no methanol-insoluble polymer at 60°C. On the basis of the tacticity determined it was noted that the o-substituted phenyl methacrylates preferred syndiotactic addition in the propagation reaction less than did phenyl methacrylate or methyl methacrylate. The polymers formed from the o-substituted monomers were thermally less stable than poly(phenyl methacrylate), and, consistent with this finding, ceiling temperatures of the o-substituted phenyl methacrylates seemed to be lower than that of phenyl methacrylate. The effects observed were characteristic of the o-substituents conformationally close to the carbon-carbon double bond of the monomer or the carbon carrying the unpaired electron of the polymer radical.  相似文献   
37.
Niwa H  Yasui T  Ishizuki T  Yuchi A  Yamada H  Wada H 《Talanta》1997,45(2):349-355
Performance of six quinolylazo compounds was studied as a pre-column derivatizing reagent for the separation of metal ions in the reversed-phase high-performance liquid chromatography. 2-(4-Methyl-2-quinolylazo)-5-diethylaminophenol (QADP) was suited for the determination of Co, Ni and Cu in the presence of a large amount of Fe. The detection limits under the optimized conditions [stationary phase: L-column ODS; mobile phase: acetone-water (62:38, v/v) containing 0.01 M NH(4)SCN and 0.01 M 2-morpholinoethanesulfonic acid-NaOH (pH 6); injection volume: 10 mul] were 0.24 ng for Co, 0.22 for Ni and 0.53 for Cu. This method was successfully applied to the determination of these metal ions in a standard steel sample.  相似文献   
38.
39.
40.
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