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   11650篇
  免费   1201篇
  国内免费   762篇
电工技术   912篇
综合类   982篇
化学工业   1581篇
金属工艺   636篇
机械仪表   759篇
建筑科学   961篇
矿业工程   337篇
能源动力   353篇
轻工业   779篇
水利工程   272篇
石油天然气   424篇
武器工业   176篇
无线电   1450篇
一般工业技术   1289篇
冶金工业   483篇
原子能技术   129篇
自动化技术   2090篇
  2024年   31篇
  2023年   180篇
  2022年   339篇
  2021年   492篇
  2020年   358篇
  2019年   309篇
  2018年   327篇
  2017年   370篇
  2016年   345篇
  2015年   523篇
  2014年   623篇
  2013年   650篇
  2012年   763篇
  2011年   896篇
  2010年   847篇
  2009年   786篇
  2008年   783篇
  2007年   761篇
  2006年   776篇
  2005年   625篇
  2004年   445篇
  2003年   327篇
  2002年   403篇
  2001年   417篇
  2000年   246篇
  1999年   186篇
  1998年   135篇
  1997年   146篇
  1996年   120篇
  1995年   101篇
  1994年   76篇
  1993年   67篇
  1992年   36篇
  1991年   23篇
  1990年   20篇
  1989年   21篇
  1988年   19篇
  1987年   9篇
  1986年   10篇
  1985年   6篇
  1984年   3篇
  1983年   2篇
  1982年   2篇
  1981年   1篇
  1980年   2篇
  1979年   3篇
  1976年   1篇
  1951年   2篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
141.
泥页岩中的有机质和黏土矿物在沉积演化过程中能够相互结合形成有机质-黏土复合体,成为重要的生烃母质。基于大量的场发射扫描电镜和透射电镜观察分析,以中国鄂尔多斯盆地三叠系延长组、黔北奥陶系-志留系五峰组-龙马溪组、黔中寒武系牛蹄塘组及南华北盆地二叠系山西组4套泥页岩储层为研究对象,详细查明了泥页岩中有机质-黏土复合体的微观结构及变形作用,并深入探讨了其源-储意义。泥页岩中有机质-黏土复合体成分复杂,形态多样,且易发生变形;驱动复合体发生变形的主要机制有构造应力作用、矿物颗粒作用、有机质赋存及黏土矿物转化。其中,由外部构造应力和复合体内部矿物颗粒对黏土层、有机质层挤压引起的变形能够改变复合体局部应力环境,所形成的拉张环境可使复合体发育大量纳米孔隙,且这些孔隙因黏土层的保护而不易发生烃类散失,可有效提升泥页岩的储集能力。相关结论有助于完善泥页岩的成岩理论,增进对页岩油气生成、运移和储集过程的认识,进而指导页岩油气的勘探开发。  相似文献   
142.
目的解决三甘醇工艺脱水效率降低及能耗偏高等问题,对操作参数进行优化。方法采用灵敏度分析法和响应曲面法对运行参数进行优化。①采用灵敏度分析法选出富液进塔温度、重沸器温度、TEG贫液循环量、汽提气体积流量作为因素变量,以干气水露点和运行费用为响应值,通过HYSYS软件模拟计算25组试验数据;②采用响应曲面法进行分析和优化。结果富液进塔温度和汽提气体积流量间的交互作用对干气水露点影响最显著,富液进塔温度和TEG贫液循环量间的交互作用对运行费用影响最显著,优化后的最佳工艺参数为:富液进塔温度144.28℃、重沸器温度205.4℃、TEG贫液循环量4 m^(3)/h、汽提气体积流量24.96 m^(3)/h。在干气水露点满足外输要求和天然气处理量为300×10^(4) m^(3)/d的情况下,运行费用可降低69.33万元/年。结论响应面法可为指导现场运行参数优化提供理论基础。  相似文献   
143.
Hu  Chuang  Zang  Guo-Long  Luo  Jun-Tao  Liu  Qi  Zhao  Quan 《Journal of Applied Electrochemistry》2021,51(6):847-859
Journal of Applied Electrochemistry - The electrocatalytic reduction of CO2 is a promising research direction in resource utilization and sustainable energy development. However, there is still a...  相似文献   
144.
This work studied the effects of adding short basalt fibers (BFs) and multi-walled carbon nanotubes (MWCNTs), both separately and in combination, on the mechanical properties, fracture toughness, and electrical conductivity of an epoxy polymer. The surfaces of the short BFs were either treated using a silane coupling agent or further functionalized by atmospheric plasma to enhance the adhesion between the BFs and the epoxy. The results of a single fiber fragmentation test demonstrated a significantly improved BF/epoxy adhesion upon applying the plasma treatment to the BFs. This resulted in better mechanical properties and fracture toughness of the composites containing the plasma-activated BFs. The improved BF/epoxy adhesion also affected the hybrid toughening performance of the BFs and MWCNTs. In particular, synergistic toughening effects were observed when the plasma-activated BFs/MWCNTs hybrid modifiers were used, while only additive toughening effects occurred for the silane-sized BFs/MWCNTs hybrid modifiers. This work demonstrated a potential to develop strong, tough, and electrically conductive epoxy composites by adding hybrid BF/MWCNT modifiers.  相似文献   
145.
In this work, low density hollow glass beads (HGB)/silicon rubber (SR) composites were prepared by solution method and flocculation process. The prepared samples were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, tensile test, and friction test. The results show that the densities of SR composites decrease from 1.140 to 0.792 g/cm3 with the addition of HGB. By comparing theoretical density with true density, it can be estimated that the ratio of shattered HGB increase from 8.79% to 24.76%. Especially, the mechanical properties of SR composites were improved by surface modification of HGB. By adding surface-modified HGB at 5 and 10 wt%, the tensile strengths of SR composites were enhanced by 17.8% and 28.2%, respectively. In addition, tear strength, shore A hardness, compression set, and friction property were significantly ameliorated. Furthermore, the mechanism of surface-modified HGB in mechanical properties was analyzed.  相似文献   
146.
Sustainable development strategy has aroused a great interest in biomass resources as alternative raw materials. A kind of biomass-derived poly(butylene succinate) (PBS), has been developed as porous foams to reduce resource exhaustion and meet lightweight demands. For fire-safety in-service, graphene oxide (GO) was functionalized by 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) to combine flame-retardant elements and heat-barrier function. Hence, a very low loading level of P-containing GO as only 5 wt% could reduce peak heat release rate (pHRR) and total heat release (THR) of PBS-based foams by 58.5% and 22.3%, respectively. Meanwhile, N-/P-doped mesoporous char with a specific surface area of 136 m2/g, which derived from combustion of flame-retardant foaming PBS, contributes to a potential of energy storage applications in the capacitor or the anode of Li-ion battery with long-term stability. Overall, the sustainability of bio-based polyester could integrate lightweight of foaming, and be extended to utilization after use via facile combustion inspired by flame-retardancy design.  相似文献   
147.
A simple and feasible method to enhance the wear resistance of ultra-high molecular weight polyethylene (UHMWPE) fibers was reported. The graphite oxide (GO) prepared using improved Hummer's method was surface modified with hexadecylamine to improve its compatibility with UHMWPE. Combined with well-dispersion of modified-GO (m-GO) in dichloromethane and the fact that the viscosity of UHMWPE suspension can be decreased by dichloromethane, the well dispersed m-GO/dichloromethane was added into UHMWPE suspension to improve m-GO dispersion in UHMWPE fibers. Finally, UHMWPE fibers with different m-GO concentration were prepared using gel spinning technology. The effect of m-GO concentration on the structure and properties of modified UHMWPE fibers were investigated. The results indicated that the melting temperature and crystallinity of m-GO modified UHMWPE fibers increased with increasing of m-GO concentration, while the fiber's crystal sizes and orientation increased, thus the tensile strength of m-GO modified UHMWPE fibers remained almost undamaged. The introduction of m-GO is beneficial to the formation of smooth transfer film on fiber's surface, which enhanced the self-lubrication of UHMWPE fibers. Compared with pure UHMWPE fiber, the UHMWPE fiber containing 1.5 wt% m-GO had enhanced wear resistance by 55.4% and still maintained high tensile strength of 29.98 cN dtex−1.  相似文献   
148.
考虑供水系统深度响应的微网经济调度策略   总被引:1,自引:0,他引:1  
高风电渗透率微网(microgrid,MG)存在实时功率平衡和经济运行难的问题。为此,该文提出一种考虑供水系统(water supply system,WSS)深度响应的MG经济调度策略。首先,将WSS主动解列成多个独立运行的子系统,降低系统关联约束,提高调节灵活性。进而,建立水压的波动性约束,提出WSS需求侧响应模型。在此基础上,充分考虑外电网调峰、调频等需求,提出一种新型的MG经济调度策略。最后,引入近似线性化的方法,将非线性模型转化为经典的混合整数线性规划(mixed-integerlinearprogramming,MILP)问题,提高求解速度。基于15节点的WSS和典型MG的仿真结果表明,WSS深度响应能够显著改善MG运行经济性。该文研究成果为MG可再生能源消纳问题的解决提供了一个崭新的视角。  相似文献   
149.
作为高压直流控制保护系统最重要的采样通道之一,零磁通电流互感器所测量得到的数据是高压直流输电的控制、保护和测量最关键的信息和可靠的凭证.现有的零磁通电流互感器二次信号现场模拟方法缺乏.提出了一种易于实施的零磁通电流互感器二次信号现场模拟方法,可满足控制、保护对零磁通电流互感器采样通道的准确度和广度测试需要.所提方法在(特)高压直流输电工程开展了零磁通电流互感器采样通道现场模拟测试,验证所提方法有效性.  相似文献   
150.
潘权  陈坚兴 《重型机械》2006,(Z1):89-93
采用共轭曲面原理对应用广泛的环面槽球笼同步万向联轴器,进行了分析;建立了球笼万向轴器实现同步运动时,各接触面的运动关系、曲面方程以及共轭运动关系,推导出了球笼万向联轴器瞬时同步的必要充分条件为两对啮合付的偏心值ε1T=ε1的结论.  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