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   11057篇
  免费   715篇
  国内免费   258篇
电工技术   24篇
综合类   537篇
化学工业   6405篇
金属工艺   112篇
机械仪表   94篇
建筑科学   396篇
矿业工程   300篇
能源动力   66篇
轻工业   1510篇
水利工程   23篇
石油天然气   860篇
武器工业   40篇
无线电   69篇
一般工业技术   1378篇
冶金工业   128篇
原子能技术   56篇
自动化技术   32篇
  2024年   42篇
  2023年   100篇
  2022年   189篇
  2021年   220篇
  2020年   221篇
  2019年   235篇
  2018年   217篇
  2017年   278篇
  2016年   250篇
  2015年   268篇
  2014年   442篇
  2013年   582篇
  2012年   730篇
  2011年   747篇
  2010年   626篇
  2009年   583篇
  2008年   537篇
  2007年   676篇
  2006年   757篇
  2005年   649篇
  2004年   603篇
  2003年   490篇
  2002年   405篇
  2001年   369篇
  2000年   350篇
  1999年   301篇
  1998年   248篇
  1997年   207篇
  1996年   126篇
  1995年   115篇
  1994年   110篇
  1993年   100篇
  1992年   76篇
  1991年   51篇
  1990年   31篇
  1989年   34篇
  1988年   13篇
  1987年   7篇
  1986年   4篇
  1985年   8篇
  1984年   8篇
  1983年   5篇
  1982年   10篇
  1981年   1篇
  1980年   5篇
  1978年   1篇
  1951年   3篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
用两亲聚合物制备大颗粒苯丙乳液   总被引:10,自引:0,他引:10  
分别以两亲聚合物P(C9-AA)和P(DCPD-St-α-St-AA)作乳化荆,研究了制备大颗粒(约1μm)及具有一定稳定性的苯丙乳液的方法,讨论了乳化剂,温度及引发剂用量对乳液性能的影响。结果表明,以P(C9-AA)作乳化剂时,引发剂用量为单体质量的1.2%,90℃时可以合成性能良好的苯丙乳液;以P(DCPD-St-α-St-AA)作乳化荆时,引发剂用量为单体质量的1.2%,80℃时可以合成性能良好的苯丙乳液。  相似文献   
52.
Environmentally responsive hydrogels have become attractive research subjects for many applications. In this work, a series of pH‐sensitive and color‐changing nanoparticles (nanogels) with core–shell structures were synthesized. The cores were blue latex particles synthesized by a miniemulsion technique with styrene and methacrylic acid as monomers and Neozapon Blue 807 as a dye. The shell was a pH‐sensitive polymer that was precipitation‐polymerized onto the core from 2‐(diethylamino) ethyl methacrylate with N,N′‐methylenebisacrylamide, poly(propylene glycol) diacrylate, and divinylbenzene as crosslinking agents. In the resultant latexes, the color was observed to change from deep blue to pale blue as the pH of the system was changed from a high of 10 to a low of 3. The synthesized latexes and particles (gels) were then characterized with an ultraviolet–visible spectrometer, dynamic light scattering, Fourier transform infrared, and nuclear magnetic resonance. Atomic force microscopy was also used to investigate the different morphologies of the particles after the synthesized latexes were dried at different pH values. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008  相似文献   
53.
Polymer/Silica nanocomposite latex particles were prepared by emulsion polymerization of methyl methacrylate (MMA) with dimethylaminoethyl methacrylate (DM). The reaction was performed using a nonionic surfactant and in the presence of silica nanoparticles as the seed. The polymer‐coated silica nanoparticles with polymer content and number average particle sizes ranged from 32 to 93 wt % and 114–310 nm, respectively, were obtained depending on reaction conditions. Influences of some synthetic conditions such as MMA, DM, surfactant concentration, and the nature of initiator on the coating of the silica nanoparticles were studied. Electrostatic attraction between anionic surface of silica beads and cationic amino groups of DM is the main driving force for the formation of the nanocomposites. It was demonstrated that the ratio of DM/MMA is important factor in stability of the system. The particle size, polymer content, efficiency of the coating reaction, and morphology of resulted nanocomposite particles showed a dependence on the amount of the surfactant. Zeta potential measurements confirmed that the DM was located at the surface of the nanocomposites particles. Thermogravimeteric analysis indicated a relationship between the composition of polymer shell and polymer content of the nanocomposites. The nanocomposites were also characterized by FTIR and differential scanning calorimetry techniques. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008  相似文献   
54.
综述了聚丙烯酸酯防水乳液的理论研究进展,重点评述了组合功能单体、优选乳化体系和进行粒子设计三方面的改性手段。  相似文献   
55.
丙烯酸二甲氨基乙酯的合成   总被引:6,自引:0,他引:6  
以丙烯酰氯与二甲氨基乙醇为原料 ,乙醚为溶剂 ,过量的二甲氨基乙醇为缚酸剂合成了丙烯酸二甲氨基乙酯。较佳实验条件为 :丙烯酰氯 /二甲氨基乙醇 /乙醚 (物质的量比 ) 1∶2 .0 5∶5 .6 ,反应温度 5℃ ,反应时间 4h ,w(吩噻嗪 ) 0 .5 0 %,产物为无色透明液体 ,相对密度 0 .943 1( 2 0℃ ) ,折光率为 1.435 2 ,收率大于 91%。  相似文献   
56.
A new type of polysiloxane modified polyurethane–acrylic hybrid emulsion was synthesized by solvent-free method and the polysiloxane was introduced into the soft segment of polyurethane chains using dihydroxybutyl-terminated polydimethylsiloxane (PDMS). The formed film from the hybrid emulsion could provide obviously higher water-resistance property. The preparation technologies such as the content of carboxy group and acrylic monomer, the rate and the time of emulsification were discussed systematically. The chain structure and the particle size were confirmed by the analysis of Fourier transform infrared spectroscopy and transmission electron microscopy, respectively. The effect of PDMS content on the water resistance and the mechanical property were investigated by absorbed water ratio, water contact angle and dynamic mechanical measurement.  相似文献   
57.
原油破乳脱钙复合剂的研制   总被引:2,自引:0,他引:2  
介绍了原油破乳脱钙复合剂的筛选方法。所用的破乳剂有PY、UD 10、2 0 40、SDX、SL、硬脂酸 三乙醇胺 ,所用的脱钙剂有KL 1、KL 2、KL 3、KL 4、YH、EA、SJ、LP。首先将一定量的破乳剂与原油混合 ,振荡、静置 ,按油水分层情况及脱水率 ,筛选出较优的破乳剂。然后 ,在已加入破乳剂的原油中加入一定量的脱钙剂水溶液 ,振荡、静置 ,用燃烧瓶法处理油样 ,用原子吸收分光光度计测其钙含量 ,并与未经处理的原油对比。根据脱钙率 ,筛选出较优的脱钙剂。经过对破乳剂和脱钙剂的种类、用量、pH值等条件的选择 ,配出了针对俄罗斯原油、布伦特原油、扎非罗原油破乳、脱钙效果最好的复合剂PY YH、PY EA ,其脱钙率大于 80 %,脱水率大于98%,可直接用于炼厂的原油破乳脱钙工艺中。  相似文献   
58.
乳化炸药的乳化物理模型和理想乳化模态   总被引:3,自引:1,他引:2  
文章以平推流模拟了乳化炸药乳胶质的形成过程,并建立了机械强制乳化的物理模型及理想模态。  相似文献   
59.
郭子如  胡企强 《爆破》1994,11(1):78-80
文章分析了光爆炸药的性能特点,提出了制造光爆炸药新方法。该炸药密度(0.35、0.70g/cm ̄3)与爆速(1300、2200m/s)可调,贮存性能稳定;爆轰感度好,能满足不同硬度岩石尤其是软岩的光爆需要。  相似文献   
60.
This paper reports a study undertaken using techniques of static and dynamic light scattering to investigate the influence of sodium salicylate and methyl salicylate on droplet size of oil-in-water emulsions. The rates of changes were measured by determining the size and distribution of the oil droplet in the material. All emulsions showed a bimodal size distribution; the mean diameters and polydispersity were calculated from intensity. These data were analyzed with nonlinear regressions and bootstrap methodology. An amount of methyl salicylate component induced a decrease of mean diameter and standard deviation. On the contrary, sodium salicylate entailed the growth of all droplet populations and coalescence for the highest concentration.  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