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   214594篇
  免费   3667篇
  国内免费   526篇
化学   116780篇
晶体学   2499篇
力学   8587篇
综合类   3篇
数学   26816篇
物理学   64102篇
  2021年   1595篇
  2020年   2025篇
  2019年   2153篇
  2018年   2919篇
  2017年   2823篇
  2016年   4600篇
  2015年   3193篇
  2014年   4455篇
  2013年   10460篇
  2012年   8915篇
  2011年   10159篇
  2010年   6990篇
  2009年   6599篇
  2008年   9313篇
  2007年   9256篇
  2006年   8560篇
  2005年   7918篇
  2004年   7173篇
  2003年   6263篇
  2002年   5896篇
  2001年   5837篇
  2000年   4334篇
  1999年   3205篇
  1998年   2643篇
  1997年   2574篇
  1996年   2495篇
  1995年   2329篇
  1994年   2389篇
  1993年   2278篇
  1992年   2576篇
  1991年   2487篇
  1990年   2413篇
  1989年   2350篇
  1988年   2316篇
  1987年   2303篇
  1986年   2178篇
  1985年   2981篇
  1984年   2975篇
  1983年   2549篇
  1982年   2781篇
  1981年   2586篇
  1980年   2548篇
  1979年   2680篇
  1978年   2704篇
  1977年   2620篇
  1976年   2700篇
  1975年   2588篇
  1974年   2549篇
  1973年   2705篇
  1972年   1716篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Russian Journal of Organic Chemistry - The reduction of 1-(adamantan-1-yl)-2-azidoethan-1-one oxime with LiAlH4 gave racemic 1-(adamantan-1-yl)ethane-1,2-diamine, which was resolved with l-tartaric...  相似文献   
992.
Russian Journal of Organic Chemistry - A series of 2-amino-4-aryl-5-oxochromeno[4,3-b]pyridine-3-carbonitriles have been synthesized with good yields (85–90%) by reacting...  相似文献   
993.
Journal of Thermal Analysis and Calorimetry - This study investigated the thermal skin (Tsk) response of lower limbs in older adults with or without osteoarthritis before and after a concurrent...  相似文献   
994.
Journal of Thermal Analysis and Calorimetry - The unsteady thermal behavior of a porous longitudinal fin in a fully wet circumstance in the existence of convection as well as radiation effect is...  相似文献   
995.
Journal of Thermal Analysis and Calorimetry - Geopolymers are considered as environmentally friendly binders with a high potential not only to lower the prices of binders, but mainly to decrease...  相似文献   
996.
3-Methylenecyclobutanecarboxylic acid and its methyl ester were used as the starting compounds for the synthesis of new spiro[2.3]hexane amino acids, the conformationally rigid analogs of γ-aminobutyric acid, namely, 5-aminospiro[2.3]hexanecarboxylic and 5-amino-spiro[2.3]hexanephosphonic acids, promising modulators of GABAergic cascades in the human central nervous system. The methods developed for the synthesis of the target amino acids are based on the reactions of catalytic [1+2] cycloaddition of diazoacetic and diazophosphonic esters to 3-substituted methylenecyclobutanes, as well as on a modified Curtius reaction for the transformation of a carboxy group to the amine one.  相似文献   
997.
A reaction of methyl 2-(4-allyl-2-methoxyphenoxy)acetate with adamantan-2-amine and (adamantan-1-yl)methylamine in butanol leads, together with the target amides, to the formation of butyl ester of the corresponding acid, which is resistant to aminolysis.  相似文献   
998.
Synthetic approaches to the design of new multitarget agents for the treatment of neurodegenerative diseases are surveyed. These approaches are based on the conjugation of the pharmacophoric indole, phenothiazine, and aminoadamantane moieties via 1-oxopropylene and 2-hydroxypropylene spacers using reactions of acrylate- and epoxide-containing pharmacophores with tetrahydro-γ-carbolines, cycloalkaneindoles, carbazoles, and aminoadamantanes. The review considers data on biological activity of the compounds assessed within a complex screening system. This system includes neurotransmitter targets associated with cognitive compensation, such as cholinesterases and glutamate receptors, mitochondria, the influence on which can provide neuroprotective effects, and microtubules, the stabilization of which leads to the improvement of axonal transport. The ability of the compounds to act as free-radical scavengers was evaluated. Types of polypharmacophoric compounds promising for further development are proposed.  相似文献   
999.
Colloidal dispersions of MoS2 in DMF were obtained, and a procedure for the preparation of the fraction of particles with the size distribution 1.5 times narrower than that in the original dispersion was developed. It was shown that for the gradual centrifugation of dispersions with an increase in the acceleration from 126g to 2016g the average thickness of nanosheets decreased from 35 to 8 nm and the average lateral sizes decreased from 250 nm to a constant value of 160 nm. A linear dependence of the absorbance of the dispersions on the concentration of MoS2 was established.  相似文献   
1000.
Russian Chemical Bulletin - Polyfunctional p-tert-butylthiacalix[4]arenes tetrasubstituted at the lower rim with nitrogen-containing fragments in the cone, partial cone, and 1,3-alternate...  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