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   12622篇
  免费   1075篇
  国内免费   573篇
化学   9004篇
晶体学   139篇
力学   520篇
综合类   47篇
数学   1152篇
物理学   3408篇
  2023年   131篇
  2022年   217篇
  2021年   368篇
  2020年   348篇
  2019年   368篇
  2018年   269篇
  2017年   273篇
  2016年   465篇
  2015年   422篇
  2014年   530篇
  2013年   840篇
  2012年   1025篇
  2011年   1067篇
  2010年   733篇
  2009年   642篇
  2008年   838篇
  2007年   712篇
  2006年   698篇
  2005年   628篇
  2004年   524篇
  2003年   452篇
  2002年   441篇
  2001年   279篇
  2000年   233篇
  1999年   174篇
  1998年   146篇
  1997年   135篇
  1996年   151篇
  1995年   119篇
  1994年   91篇
  1993年   112篇
  1992年   97篇
  1991年   92篇
  1990年   67篇
  1989年   73篇
  1988年   50篇
  1987年   46篇
  1986年   45篇
  1985年   45篇
  1984年   31篇
  1983年   26篇
  1982年   28篇
  1981年   31篇
  1980年   20篇
  1979年   21篇
  1977年   22篇
  1976年   20篇
  1974年   20篇
  1973年   15篇
  1970年   15篇
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
131.
The alkyl polyglycosides (APG) is new type the surfactants that is made by regenerationresource of the starch and the grease, since the nineties of 20th century it is energetically exploited ininternational extent. APG not only good in surface activity, but also plenty on bubble, thin greasyand stabilization, there are good decontamination, compatibility, innocuity, not incitation and uniquefunction that organism decomposition of swiftness and downrightness, and so on.APG is to get production that loses one molecule water with half condensation aldehyde hydroxyand sebum alcohol hydroxy under acid catalysis. The production not is one simplicity compound, butis one of sugar polymerization degree, so it is mixture of the alkyl single glucoside, the alkyl twoglucoside and the alkyl three glucoside.Author synthesizes the surfactants of the alkyl polyglycosides, with the oleaster and potato starchand sebum alcohol, that was chosen to use duality system activator of plant acid and p-toluene-sulfoacid for the first time. The adoption way is that the lower alkyl polyglycosides is firstly formed byreaction of lower alcohol with starch then exchanged with high alcohol to obtain APG. The study isto make certain most technics condition, determining capillary tension and the pastern sheafdeepness of critical, calculating HLB value, determining construction by 1R.To synthesize principium:Peroration :[1]Duality system activator of plant acid and p-toluene-sulfo acid is compare idea activator that was the lower alkyl polyglycosides is firstly formed by reaction of lower alcohol with glucose then exchanged with high alcohol to obtain high alkyl polyglycosides. The advantage is that it overcomes agglomeration, there is reaction entirety, high of sugar transform ratio, reaction time short.[2]Most good reaction temperature is 90~ 170℃, the dosage of activator is 0.5%~0.9%, the mated ratio: The APG of glucose basic butane ratio starch is 5:1, the APG of potato starch basic glycol ratio starch is 6:1, the APG of the oleaster starch basic glycol ratio starch is 12:1, the APG of the mealiest starch basic glycol ratio starch is 6:1, the product of complex is good property.[3]The alkyl polyglycosides is the products of surfactant. IR determines the functional group of the products. On the basis of group of the hydrophile and to close on oil, that the feature peak of α-1, 4- glucoside.[4]The capillary tension of the APG is 26.8~31.0mN/m, the HLB value is 16~18, the products is better emulsifying agent of water- solubility. (O/W).  相似文献   
132.
The oscillating conditions for a series piezoelectric quartz crystal (SPQC) are proposed and verified experimentally. The influence of the cell constant and oscillator phase on the oscillational ability of the SPQC was investigated. It is shown that the SPQC possesses excellent oscillational ability in low or high conductivity solutions, but in solution of intermediate conductivity, the oscillational ability decreases with increasing oscillator phase or decreasing cell constant, sometimes resulting in a cease-to-oscillate zone. The SPQC was applied to determine the urease activity in plant seeds with a detection limit of 0.004 U ml−1, based on the change in conductivity.  相似文献   
133.
134.
A macro-azoinitiator containing polyarylate segment and azo group was prepared by the solution polycondensation of azobiscyanopentanoyl chloride and hydroxy-terminated polyarylates having viscosity-average molecular weights of 6200, 8100, and 12 400. These macro-azoinitiators were used in the radical polymerization of styrene to synthesize polyarylate-polystyrene block copolymers. Thermal properties measured by the differential scanning calorimetry indicated the phase separated morphology of the block copolymers except at low molecular weight of the block constituents. © 1993 John Wiley & Sons, Inc.  相似文献   
135.
136.
137.
138.
139.
140.
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