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   6494篇
  免费   502篇
  国内免费   122篇
电工技术   265篇
综合类   204篇
化学工业   1124篇
金属工艺   221篇
机械仪表   206篇
建筑科学   383篇
矿业工程   48篇
能源动力   359篇
轻工业   529篇
水利工程   109篇
石油天然气   194篇
武器工业   4篇
无线电   814篇
一般工业技术   990篇
冶金工业   432篇
原子能技术   28篇
自动化技术   1208篇
  2024年   14篇
  2023年   109篇
  2022年   190篇
  2021年   281篇
  2020年   219篇
  2019年   208篇
  2018年   260篇
  2017年   239篇
  2016年   281篇
  2015年   236篇
  2014年   265篇
  2013年   505篇
  2012年   368篇
  2011年   470篇
  2010年   373篇
  2009年   382篇
  2008年   316篇
  2007年   274篇
  2006年   259篇
  2005年   202篇
  2004年   141篇
  2003年   162篇
  2002年   209篇
  2001年   149篇
  2000年   109篇
  1999年   73篇
  1998年   111篇
  1997年   85篇
  1996年   72篇
  1995年   71篇
  1994年   63篇
  1993年   51篇
  1992年   36篇
  1991年   19篇
  1990年   32篇
  1989年   19篇
  1988年   22篇
  1987年   25篇
  1986年   18篇
  1985年   14篇
  1984年   28篇
  1983年   15篇
  1982年   20篇
  1981年   14篇
  1980年   11篇
  1979年   9篇
  1978年   12篇
  1977年   13篇
  1976年   17篇
  1975年   10篇
排序方式: 共有7118条查询结果,搜索用时 15 毫秒
91.
Ben 《电脑》2014,(1):196-197
十年发展,十年沉淀,十年新起点!2013年12月9日,由上海追得贸易发展有限公司主办的"智慧·创新·分享"暨"大师贴膜品牌升级行业发布会"于上海兴荣温德姆五星级酒店隆重召开。时值企业成立十周年,大师贴膜品牌迎来了又一次里程碑式的跨越,追得企业也将迎来更加创新的发展模式。  相似文献   
92.
Rock phosphate fractions were examined for their porous structure by nitrogen adsorption. The pore size distribution and the shape of pores does not seem to depend on the particle size. The specific surface area values present two regions, one above and one below that of the particles with 125 μrn diameter. Particles of a given size were leached with dilute phosphoric acid (1.5 mass% P2O5) at 25°C. It was observed that there is a widening of the initial pores during leaching. The particles collected at the initial period of the reaction are pitted and those collected at the final period are disintegrated.  相似文献   
93.
Ben 《电脑》2014,(6):198-198
正眼下,信息的日益透明化、渠道的日渐扁平化、消费的日趋理性化都给国内窗膜市场提出了新的要求,中美合资羿阳(Unisun)科技趁机而入,带来Sundef山迪品牌,给行业、给消费者带来了源自美国的高性价比高端产品选择。新时代下的消费新需求中国的太阳膜市场拥有近20年的发展历史,期间经历了多次变革。眼下,隔热膜已成为汽车  相似文献   
94.
Ben 《电脑》2014,(10)
正火爆的眼球之争作为有史以来最火爆的亲子节目,《爸爸去哪儿》成为了全民狂欢的游戏,同时也拉动了一系列相关品牌的关注度飙升。比如去年"仅"以2800万"捡"得冠名权的999感冒灵,年销量飙升40%。惹得各路豪强眼红不已,第二季冠名权立马硬生生杀到3.1个亿,各大品牌在节目中争相露脸,你方唱罢我登场,不挤爆观众眼球不罢休。  相似文献   
95.
Ben 《电脑》2014,(10)
正357面玻璃见证圣戈班的诞生巴黎凡尔赛宫,巴黎著名的宫殿之一,同时也是世界五大宫之一(北京故宫、法国凡尔赛宫、英国白金汉宫、美国白宫、俄罗斯克里姆林宫)。法国国王路易十四和路易十六最喜爱的住所,这里历经几代建筑师,雕塑家,装饰艺术家和风景画家的耕耘,成为一个世纪以来欧洲皇家住所的典范。1979年,凡尔赛宫和花园作为法国17世纪艺术的杰作被联合国教科文组织收入世界人文遗产名录。凡尔赛宫宏伟、壮观,它的内部陈设和装潢富于艺术魅力,名胜景观  相似文献   
96.
Polyfunctional monomers (PFMs), namely, trimethylol propane trimethacrylate (TMPTMA), trimethylol propane triacrylate, ethylene glycol dimethacrylate, and diethylene glycol diacrylate were blended with low‐density polyethylene (LDPE) and exposed to different doses of EB irradiation. Fourier transform infrared and ultraviolet and UV–vis spectroscopy of the unirradiated, irradiated, unloaded, and PFMs‐loaded LDPE films were studied under various irradiation doses up to 300 kGy. The degree of crosslinking and oxidative degradation, as measured by the spectroscopic parameters, were dependent on both the irradiation dose and the type of loaded PFMs. For all of the loaded monomers, the extent of crosslinking increased at different rates as a function of irradiation dose. TMPTMA monomer was the most efficient in enhancing the crosslinking of LDPE films compared to the other loaded monomers. However, the unloaded LDPE film showed the least extent of crosslinking. In addition, the EB‐radiation‐induced changes, such as trans‐vinylene formation, a decrease in vinyl and vinylidene unsaturation; and carbonyl double‐bond formation and change in crystallinity were correlated. The importance of these results on the prediction of the role of polyfunctional monomers in the production of crosslinked polymers is discussed. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2025–2035, 2003  相似文献   
97.
准确预报大雾对机场减少航班大面积延误和旅客滞留有重要意义。本文阐述一种适用于机场的大雾短时预报方法。通过选取骆岗机场历史地面逐时观测气象资料,依据气温趋势不同类型,运用模糊隶属度与发生条件概率模型,分别建立短时大雾的预报方法。利用VC++程序开发了骆岗机场大雾短时预报软件,可扩展硬件构建实时预警系统。使用2011年地面资料检验结果显示:对未来3小时大雾预报准确率为91.3%,TS评分为0.84。因此,本文提出的大雾短时预报方法在骆岗机场附近3小时大雾预报中是有效的。  相似文献   
98.
Compositional reasoning using intervals and time reversal   总被引:1,自引:0,他引:1  
Interval Temporal Logic (ITL) is an established formalism for reasoning about time periods. We investigate some simple kinds of ITL formulas which have application to compositional reasoning and furthermore are closed under conjunction and the conventional temporal operator known both as “box” and “always”. Such closures help us modularly construct formulas from simple building blocks in a way which preserves useful compositional properties. The most important class considered here is called the 2-to-1 formulas. They offer an attractive framework for analysing sequential composition in ITL and provide the formal basis for most of the subsequent presentation. A key contribution of this work concerns a useful and apparently new and quite elementary mathematical theorem that 2-to-1 formulas are closed under “box”. We also use a natural form of time symmetry with 2-to-1 formulas. This extends known facts about such formulas by looking at them in reverse. An important example involves showing that 2-to-1 formulas are also closed under a variant of “box” for prefix subintervals rather than suffix ones. We then apply the compositional formulas obtained with time symmetry to analyse concurrent behaviour involving mutual exclusion in both Peterson’s algorithm and a new and more abstract one. At present, our study of mutual exclusion mainly serves as a kind of experimental “proof of concept” and research tool to develop and illustrate some of the logical framework’s promising features. We also discuss how time symmetry sometimes assists in reducing reasoning in ITL to conventional linear-time temporal logic.  相似文献   
99.
The role of the C-terminal Leu300 in maintaining thermal stabilityof the neutral protease of Bacillus subtilis was investigated.From model building studies based on the three dimensional structureof thermolysin, the neutral protease of B.thermoproteolyticus,it was conduded that this residue is located in a hydrophobicpocket composed of residues located in the C-terminal and themiddle domain. To test the hypothesis that Leu300, by contributingto a stabilizing interaction between these domains, is importantfor enzyme stability, several neutral protease mutants wereconstructed and characterized. The thermostability of the enzymewas lowered by deleting Leu300 or by replacing this residueby a smaller (Ala), a polar (Asn) or a sterically unfavourable(He) amino acid. Thermostabiity was increased upon replacingLeu300 by Phe. These results are in agreement with model-buildingstudies. The effects on thermostability observed after mutatingthe corresponding Val318 in the thermostable neutral proteaseof B.stearothermophilus were less pronounced.  相似文献   
100.
2020年中国低碳能源中期目标解读   总被引:3,自引:2,他引:1  
提出了关联能源强度ε与碳强度κ的一个新的能源经济参数—能源碳强度ω;并用以核算、澄清了中国政府宣布的2020年"节能(降低ε)"与"减排(CO2)"两个目标之间的关系.估算出了到2020年中国能源消耗为41亿吨标煤、人均2.93吨标煤、能源弹性系数0.5,二氧化碳排放量不超过76亿吨、占世界24.7%的目标数据;指出了实现这一宏伟目标的最重要途径:除快速发展非化石能源和煤的CCS利用外,就是产业转型和发展天然气冷热电联供能源系统,大幅度提高能效.  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