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   456568篇
  免费   2451篇
  国内免费   920篇
化学   225130篇
晶体学   6877篇
力学   23435篇
综合类   9篇
数学   61761篇
物理学   142727篇
  2021年   4307篇
  2020年   4911篇
  2019年   5793篇
  2018年   7700篇
  2017年   7811篇
  2016年   10410篇
  2015年   5128篇
  2014年   9148篇
  2013年   18861篇
  2012年   14834篇
  2011年   17560篇
  2010年   13742篇
  2009年   13860篇
  2008年   17052篇
  2007年   16834篇
  2006年   15447篇
  2005年   13694篇
  2004年   12752篇
  2003年   11747篇
  2002年   11899篇
  2001年   11972篇
  2000年   9581篇
  1999年   7144篇
  1998年   6485篇
  1997年   6401篇
  1996年   5918篇
  1995年   5109篇
  1994年   5242篇
  1993年   5238篇
  1992年   5427篇
  1991年   5814篇
  1990年   5684篇
  1989年   5706篇
  1988年   5410篇
  1987年   5432篇
  1986年   5146篇
  1985年   6294篇
  1984年   6638篇
  1983年   5532篇
  1982年   5928篇
  1981年   5512篇
  1980年   5159篇
  1979年   5765篇
  1978年   6006篇
  1977年   6139篇
  1976年   6186篇
  1975年   5813篇
  1974年   5680篇
  1973年   5964篇
  1972年   4619篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
102.
The behavior of real disperse systems with organic impurities was examined under conditions of destabilization by inorganic coagulants. A number of physicochemical methods of analysis and a simulation method were used to identify the character and type of the complexes formed and to calculate their stability constants.  相似文献   
103.
104.
A standard model Lagrangian is constructed making the pseudo-Finsleroid generalization of the Yang-Mills field equation by the conformal method. The Higgs field potential is suggested that ensures generation of particle masses caused by the spontaneous symmetry breaking. After transition to the conformal coordinates, the expressions obtained assume the standard form that in many cases allows the results of pseudo-Euclidean theory to be used in calculations of the Feynman diagrams. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 44–51, April, 2006.  相似文献   
105.
106.
The luminescence and scintillation properties of poly(methyl methacrylate) containing 1,1,3-trimethyl-3-phenylindan were studied.  相似文献   
107.
The known plant growth regulator, Al'den [1-(3,7-dimethyloctyl)-1-allylpiperidinium bromide], and also 1-(3,7-dimethyloctyl)-1-methylpiperidinium iodide were synthesized by treatment with allyl bromide and methyl iodide, respectively, of exhaustively hydrogenated 1-nerylpiperidine which was obtained by anionic telomerization of isoprene with piperidine. Various quaternary ammonium salts having a terpene sub- stituent with unnatural dimethyloctane skeleton, which effectively stimulate florification of Aster Chinensis L., were prepared by the action of alkyl halides on telomerization products derived from isoprene and piperidine or morpholine in the presence of palladium complexes.  相似文献   
108.
109.
The main transitions of cellulose fatty esters with different degrees of substitution (DSs) were investigated with dynamic mechanical thermal analysis. Two distinct main relaxations were observed in partially substituted cellulose esters (PSCEs). They were attributed to the glass‐transition temperature and to the chain local motion of the aliphatic substituents. The temperatures of both transitions decreased when DS or the number of carbon atoms (n) of the acyl substituent increased. Conversely, all the transitions of fully substituted cellulose esters occurred within a narrow temperature range, and they did not vary significantly with n. This phenomenon was explained by the formation of a crystalline phase of the fatty substituents. The presence of few residual OH groups in PSCEs was responsible for a large increase in the storage bending modulus, and it eliminated the effect of n on damping. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 281–288, 2003  相似文献   
110.
It is proved that a Galois extension of a field of characteristic p is completely determined by its Galois group and the endomorphism of the additive group of the group algebra that corresponds to the raising to the power p.  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