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   8436篇
  免费   455篇
  国内免费   5篇
  2022年   24篇
  2021年   77篇
  2020年   61篇
  2019年   61篇
  2018年   94篇
  2017年   80篇
  2016年   184篇
  2015年   267篇
  2014年   266篇
  2013年   556篇
  2012年   499篇
  2011年   543篇
  2010年   332篇
  2009年   306篇
  2008年   531篇
  2007年   565篇
  2006年   529篇
  2005年   513篇
  2004年   581篇
  2003年   445篇
  2002年   458篇
  2001年   126篇
  2000年   112篇
  1999年   120篇
  1998年   106篇
  1997年   85篇
  1996年   83篇
  1995年   87篇
  1994年   77篇
  1993年   68篇
  1992年   85篇
  1991年   101篇
  1990年   79篇
  1989年   71篇
  1988年   73篇
  1987年   58篇
  1986年   49篇
  1985年   40篇
  1984年   42篇
  1983年   35篇
  1982年   38篇
  1981年   36篇
  1980年   40篇
  1979年   30篇
  1978年   31篇
  1977年   35篇
  1976年   23篇
  1974年   28篇
  1973年   30篇
  1972年   23篇
排序方式: 共有8896条查询结果,搜索用时 15 毫秒
41.
(S)-2-Hydroxy-β-ionone of 96% e.e. was synthesized from (S)-3-hydroxy-2,2-dimethyl cyclohexanone, which was easily obtained by the baker’s yeast reduction of 2,2-dimethylcyclohexane-l,3-dione.  相似文献   
42.
43.
Quinolactacide isolated from Penicillium citrinum F 1539 was synthesized and evaluated for its insecticidal activities. The key steps of the total synthesis were an acyl migration reaction of the enol ester intermediate and dehydrogenation of tetrahydroquinolactacide with manganese dioxide. The synthesized quinolactacide showed 100% and 42% mortality against the green peach aphid (Myzus persicae) and diamondback moth (Plutella xylostella) at 500 ppm, respectively.  相似文献   
44.
 It is known that the retina contains the protein dystrophin in the ribbon synapse, but the ultrastructural analysis is not yet fully elucidated. Our previous study reported that dystrophin is localized under the rod cell membranes in rat retinas. In the present study, we have investigated the relationship between dystrophin-rich regions of rod cell membranes and other neuronal processes in mouse retinas with a monoclonal antibody raised against the human dystrophin C-terminus. Immunoblotting, immunofluorescence stainings, and immunoelectron microscopy were employed. Immunoblotting analysis indicated that mouse retinas possessed some of the dystrophin isoforms of approximately 260 kDa, 140 kDa, and 70 kDa molecular weight. Confocal images showed a punctate appearance in the outer plexiform layer, as previously described. Immunoelectron microscopy showed that dystrophin immunoreactive products were always observed at submembranous dense regions of the rod spherule abutting bipolar processes. These results suggest that retinal dystrophin may be closely involved in signal transmission from rods to bipolar cells. Accepted: 7 May 1997  相似文献   
45.
The hypervalent iodine-catalyzed oxylactonization of ketocarboxylic acids to ketolactones was achieved in the presence of iodobenzene (10 mol %), p-toluenesulfonic acid monohydrate (20 mol %) and meta-chloroperbenzoic acid as a stoichiometric co-oxidant.  相似文献   
46.
Summary A cellulolyticm obligately anaerobic, extreme thermophile (strain NA10) was isolated from an alkaline hot spring in Nagano Prefecture, Japan. The microorganism was a non-spore-forming, flagellated rod which had a negative reaction to Gram stain, and occurred singly or in pairs. The growth temperature was between 50° C and 85° C with the optimum at 75° C, and the growth pH was between 6.0 and 9.5 with the optimum at 8.1. The anaerobe characteristically fermented cellulose, and produced acetic acid, H2, CO2 (main products) and lactic acid (minor product). The DNA had a base composition of 37.7 mol% guanine+cytosine content.  相似文献   
47.
Mechanosensitive (MS) ion channels are molecular sensors that detect and transduce signals across prokaryotic and eukaryotic cell membranes arising from external mechanical stimuli or osmotic gradients. They play an integral role in mechanosensory responses including touch, hearing, and proprioception by opening or closing in order to facilitate or prevent the flow of ions and organic osmolytes. In this study we use a linear force model of MS channel gating to determine the gating membrane tension (γ) and the gating area change (ΔA) associated with the energetics of MscS channel gating in giant spheroplasts and azolectin liposomes. Analysis of Boltzmann distribution functions describing the dependence of MscS channel gating on membrane tension indicated that the gating area change (ΔA) was the same for MscS channels recorded in both preparations. The comparison of the membrane tension (γ) gating the channel, however, showed a significant difference between the MscS channel activities in these two preparations.  相似文献   
48.
49.
50.
Distribution of tetramethylpyrazine (T.M.P.) in Japanese fermented foodstuffs was investigated by more accurate analytical method.

Namely, the method was successful when trapping T.M.P. with picric acid after flash evaporation of the foodstuffs, followed by analysis with gas chromatography.

T.M.P. was detected in many Japanese fermented foodstuffs, especially in Miso, Soy sause and Natto, which suggests that alkylpyrazines may play an important role as flavor of those foodstuffs.  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