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   29065篇
  免费   2162篇
  国内免费   871篇
电工技术   1368篇
技术理论   1篇
综合类   1381篇
化学工业   5562篇
金属工艺   1379篇
机械仪表   1424篇
建筑科学   1960篇
矿业工程   584篇
能源动力   1074篇
轻工业   2166篇
水利工程   373篇
石油天然气   1356篇
武器工业   118篇
无线电   3372篇
一般工业技术   3919篇
冶金工业   1546篇
原子能技术   345篇
自动化技术   4170篇
  2024年   91篇
  2023年   473篇
  2022年   871篇
  2021年   1225篇
  2020年   858篇
  2019年   811篇
  2018年   851篇
  2017年   960篇
  2016年   935篇
  2015年   1049篇
  2014年   1434篇
  2013年   1885篇
  2012年   1821篇
  2011年   2052篇
  2010年   1608篇
  2009年   1666篇
  2008年   1527篇
  2007年   1408篇
  2006年   1475篇
  2005年   1289篇
  2004年   918篇
  2003年   822篇
  2002年   828篇
  2001年   590篇
  2000年   562篇
  1999年   630篇
  1998年   607篇
  1997年   487篇
  1996年   483篇
  1995年   371篇
  1994年   298篇
  1993年   201篇
  1992年   187篇
  1991年   139篇
  1990年   102篇
  1989年   83篇
  1988年   100篇
  1987年   54篇
  1986年   56篇
  1985年   39篇
  1984年   49篇
  1983年   33篇
  1982年   39篇
  1981年   20篇
  1980年   18篇
  1979年   24篇
  1977年   10篇
  1976年   11篇
  1975年   9篇
  1973年   9篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
91.
The stochastic reliable control problem for networked control systems (NCSs) subject to actuator failure and input saturation is investigated in this paper. In order to get the relationship between the maximum allowable consecutive packet dropouts, the packet dropout probability, the actuator failure matrix and the input saturation, a packet dropout probability dependent condition is given via linear matrix inequality (LMI) technology. Then, a suitable reliable controller is designed to ensure the closed-loop system to be exponentially mean square stable against actuator failures and input saturation. Finally, numerical examples are provided to show the effectiveness of the proposed method.  相似文献   
92.
点击劫持通过欺骗用户点击经过伪装的界面元素达到攻击目的。移动互联网环境下,智能手机的屏幕特征、手势识别、HTML5支持度高等特性成为点击劫持新的利用点。深入分析并实验验证智能手机脆弱特性,在此基础上提出点击劫持在智能手机上的潜在攻击方案。进而设计并实现一套有针对性的检测方案。该方案从静态页面和动态行为两个角度提取攻击特征,并进行基于规则的量化评估与组合判定。实验结果表明该方案可以有效地降低传统页面特征检测方案的漏报和误报情况。  相似文献   
93.
This study is to investigate the factors influencing the alcohol production byKluyveromyces fragilis using the juice of Jerusalem Artichoke tubers. The cell growth rate and ethanol production rate were stimulated by aeration and by the addition of unsaturated fatty acids and the cell mass production and the ethanol production were substantially improved. It was found that oxygen and unsaturated fatty acids added played a decisive role on the increase of alcohol tolerance of yeast.  相似文献   
94.
本文首先叙述了智能家居的基本概念以及分析了智能家居中的通信技术,分析了WiFi技术在智能家居中的应用优势。接着讨论了串口WiFi的功能,以WiFi插座为例,描述了串口WiFi在智能家居中的具体应用。最后叙述了基于WiFi技术的智能家居系统。  相似文献   
95.
现代科学技术,尤其是生物技术和计算机技术的飞速发展和广泛应用,给化妆品行业带来了全新的发展机遇,赋予化妆品以一定的功效性是新世纪化妆品发展的重要趋势.近20年来,人们对化妆品的要求已从洁肤、润肤为目的的基础护肤品向美白、祛皱为目的的功效性化妆品方向发展.  相似文献   
96.
The thermodynamic properties of polymer solutions are frequently described in terms of the Flory-Huggins equation. This equation includes a parameter χ, which depends upon the intermolecular forces acting between the molecules in a solution. The experimental determination of χ was performed by an improved microtechnique and extended to a wide range of polar and nonpolar diluents of polyethylene. Careful correlations are prescribed for calculating χ from pure-component properties; they are based on an extension of the Hildebrand-Scatchard theory of solutions and on the theory of intermolecular forces. Polar (τ) and nonpolar (δ) solubility parameters are presented for a variety of solvents. For polyethylene—nonpolar solvent systems we have emphasized the factor deciding the sign of heat of mixing, while for polyethylene-polar solvent systems we have determined the contribution of dipole-induced dipole interactions ψ (δτ) in interchange-energy density B and, hence, χ.  相似文献   
97.
The structure of benzoxazines is similar to that of phenolic resin through thermal self‐curing of the heterocyclic ring opening reaction that neither requires catalyst nor releases any condensation byproduct. These polybenzoxazine resins have several outstanding properties such as high thermal stability and high glass transition temperature. To better understand the curing kinetics of this copolybenzoxazine thermosetting resin, dynamic and isothermal differential scanning calorimetry measurements were performed. Three models, the Kissinger method, the Flynn–Wall–Osawa method, and the Kamal method, were used to describe the curing process. Dynamic kinetic activation energies based on Kissinger and Flynn–Wall–Osawa methods are 72.11 and 84.06 KJ/mol, respectively. The Kamal method based on an autocatalytic model results in a total order of reaction between 2.66 and 3.03, depending on curing temperature. Its activation energy and Arrhenius preexponential are 50.3 KJ/mol and 7959, respectively. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 730–737, 2005  相似文献   
98.
从实践论的视角分析马克思主义真理观.通过对真理的属性及其检验标准、真理和价值的关系问题的讨论,阐述了实践在马克思主义真理观中的作用和地位.  相似文献   
99.
The heartwood of bald cypress,Taxodium distichum (L.) Rich., resisted feeding attack by the Formosan subterranean termite,Coptotermes formosanus Shiraki. Hexane-extracted heartwood, however, was consumed at > 12 times the amount of sound heartwood eaten. A bioassay usingT. distichum sapwood as a feeding substrate was employed to assess the antitermitic activity of successive hexane, acetone, and methanol extracts of heartwood shavings and isolates derived from the active hexane extract. Two fractions, eluted from the crude hexane extract by liquid chromatography, significantly reduced termite feeding compared to the parent extract, while a third fraction was less active than the original hexane extract. Each fraction contained one major component. All three components were structurally related diterpenes. The two most active heartwood constituents were identified by GC-MS and NMR as ferruginol and manool, while the third and least active, but most prevalent, compound in heartwood was identified as nezukol. Results of bioassays suggest that these allelochemicals act principally as feeding deterrents with accompanying termite mortality due to starvation.  相似文献   
100.
Rapid growth in social networks(SNs)presents a unique scalability challenge for SN operators because of the massive amounts of data distribution among large number of concurrent online users.A request from any user may trigger hundreds of server activities to generate a customized page and which has already become a huge burden.Based on the theoretical model and analytical study considering realistic network scenarios,this article proposes a hybrid P2P-based architecture called PAIDD.PAIDD fulfills effective data distribution primarily through P2P connectivity and social graph among users but with the help of central servers.To increase system efficiency,PAIDD performs optimized content prefetching based on social interactions among users.PAIDD chooses interaction as the criteria because user’s interaction graph is measured to be much smaller than the social graph.Our experiments confirm that PAIDD ensures satisfactory user experience without incurring extensive overhead on clients’network.More importantly,PAIDD can effectively achieve one order of magnitude of load reduction at central servers.  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