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   6381篇
  免费   497篇
  国内免费   277篇
电工技术   817篇
技术理论   1篇
综合类   665篇
化学工业   383篇
金属工艺   231篇
机械仪表   473篇
建筑科学   648篇
矿业工程   314篇
能源动力   249篇
轻工业   192篇
水利工程   246篇
石油天然气   493篇
武器工业   31篇
无线电   439篇
一般工业技术   254篇
冶金工业   893篇
原子能技术   48篇
自动化技术   778篇
  2024年   10篇
  2023年   49篇
  2022年   112篇
  2021年   119篇
  2020年   179篇
  2019年   118篇
  2018年   117篇
  2017年   133篇
  2016年   167篇
  2015年   208篇
  2014年   360篇
  2013年   294篇
  2012年   484篇
  2011年   550篇
  2010年   412篇
  2009年   374篇
  2008年   343篇
  2007年   441篇
  2006年   447篇
  2005年   382篇
  2004年   341篇
  2003年   331篇
  2002年   240篇
  2001年   218篇
  2000年   138篇
  1999年   108篇
  1998年   91篇
  1997年   69篇
  1996年   58篇
  1995年   47篇
  1994年   41篇
  1993年   25篇
  1992年   17篇
  1991年   11篇
  1990年   16篇
  1989年   15篇
  1988年   9篇
  1987年   5篇
  1984年   4篇
  1966年   3篇
  1965年   7篇
  1964年   6篇
  1962年   5篇
  1961年   3篇
  1960年   5篇
  1959年   9篇
  1958年   5篇
  1957年   3篇
  1956年   3篇
  1955年   7篇
排序方式: 共有7155条查询结果,搜索用时 15 毫秒
1.
分析了注射模生产的现状,针对其生产中智能化调控应用方面的不足,提出模内参数的自适应调节方案,还介绍了自适应工作的原理、可调参数种类、逻辑推理等,并实际验证了基于注塑设备联网集成工艺数据下注射模成型工艺自适应调节的可行性。  相似文献   
2.
Project valuation, as a decision-making tool for initiating investments in projects, should be able to value project flexibilities and incorporate reasonable risk preferences of relevant decision makers. Real options valuation methods are the available approaches for valuing project flexibilities, whereas they have shortcomings in considering managers’ reasonable risk preferences in project decisions. Therefore, researchers have suggested approximating the perspective on risk of real options methods and practitioners in project management. This study proposes a fair real options valuation for project-based environments by a behavioral economic approach, which adopts binomial lattice method, Monte-Carlo simulation, and cumulative prospect theory. The results show that behavioral factors such as ‘risk attitude’ and ‘loss aversion’ should be accepted in project investment decisions while limited to an acceptable amount depending on the project conditions (e.g. uniqueness of decision-making scenarios). This research contributes to the project management domain by enhancing project investment decisions that include project flexibilities.  相似文献   
3.
Low-light images enhancement is a challenging task because enhancing image brightness and reducing image degradation should be considered simultaneously. Although existing deep learning-based methods improve the visibility of low-light images, many of them tend to lose details or sacrifice naturalness. To address these issues, we present a multi-stage network for low-light image enhancement, which consists of three sub-networks. More specifically, inspired by the Retinex theory and the bilateral grid technique, we first design a reflectance and illumination decomposition network to decompose an image into reflectance and illumination maps efficiently. To increase the brightness while preserving edge information, we then devise an attention-guided illumination adjustment network. The reflectance and the adjusted illumination maps are fused and refined by adversarial learning to reduce image degradation and improve image naturalness. Experiments are conducted on our rebuilt SICE low-light image dataset, which consists of 1380 real paired images and a public dataset LOL, which has 500 real paired images and 1000 synthetic paired images. Experimental results show that the proposed method outperforms state-of-the-art methods quantitatively and qualitatively.  相似文献   
4.
分析了汽轮机的喷嘴调节、节流调节、旁通调节、定压调节和滑压调节等几种基本调节方式的特点,指出现役燃煤火电机组多因调节方式单一而普遍存在着调峰能力不足、负荷响应迟缓以及因长期偏离设计工况致使运行安全经济性下降等诸多问题,提出了通过调节方式的优化组合,采用(节流)定压-滑压-(喷嘴)定压-旁通调节的复合调节方式,以实现煤电机组安全、经济、灵活、快速地参与电网的深度调峰,破解具有强随机波动性的新能源电量规模化并网的困境。  相似文献   
5.
火电厂锅炉是利用燃料的化学能转变为热能加热给水生产出一定参数的蒸汽,是一个多元素的能量转化系统。火电厂耗煤量占我国煤炭总消耗量的52%~63%,因此提高火电厂的发电效率对整个能源工业的效率具有十分显著的作用。现以350MW超临界锅炉及其燃烧过程作为研究对象,分别介绍超临界直流锅炉概况,分析锅炉燃烧调整试验及对比锅炉燃烧调整前后经济效益进行总结,从而获得较好效果,对提高超临界直流锅炉的燃烧效果具有重大意义。  相似文献   
6.
Wire arc additive manufacturing(WAAM)has been investigated to deposit large-scale metal parts due to its high deposition efficiency and low material cost.However,in the process of automatically manufacturing the high-quality metal parts by WAAM,several problems about the heat build-up,the deposit-path optimization,and the stability of the process parameters need to be well addressed.To overcome these issues,a new WAAM method based on the double electrode micro plasma arc welding(DE-MPAW)was designed.The circuit principles of different metal-transfer models in the DE-MPAW deposition process were analyzed theoretically.The effects between the parameters,wire feed rate and torch stand-off distance,in the process of WAAM were investigated experimentally.In addition,a real-time DE-MPAW control system was developed to optimize and stabilize the deposition process by self-adaptively changing the wire feed rate and torch stand-off distance.Finally,a series of tests were performed to evaluate the con-trol system's performance.The results show that the capability against interferences in the process of WAAM has been enhanced by this self-adaptive adjustment system.Further,the deposition paths about the metal part's layer heights in WAAM are simplified.Finally,the appearance of the WAAM-deposited metal layers is also improved with the use of the control system.  相似文献   
7.
The polymer electrolyte based solid-state lithium metal batteries are the promising candidate for the high-energy electrochemical energy storage with high safety and stability. Moreover, the intrinsic properties of polymer electrolytes and interface contact between electrolyte and electrodes have played critical roles for determining the comprehensive performances of solid-state lithium metal batteries. In this review, the development of polymer electrolytes with the design strategies by functional units adjustments are firstly discussed. Then the interfaces between polymer electrolyte and cathode/anode, including the interface issues, remedy strategies for stabilizing the interface contact and reducing resistances, and the in-situ polymerization method for enhancing the compatibilities and assembling the batteries with favorable performances, have been introduced. Lastly, the perspectives on developing polymer electrolytes by functional units adjustment, and improving interface contact and stability by effective strategies for solid-state lithium metal batteries have been provided.  相似文献   
8.
中俄东线天然气即将引入中国,将对东北地区的天然气利用项目产生有力的推动作用,同时也将面临各种问题。为建立长期可持续发展资源供应体系,结合能源供需实际,讨论了俄气到来后,东北地区天然气未来的发展方向,并分析了存在的主要问题:①天然气自产不足,域外依存度高;②地域特点决定替代能源可有多种选择;③调峰困难且富余天然气难以处理;④天然气替代经济性差,价高难以承受。并针对矛盾点进行了总结,指出来源多元化和资源多样化才能可持续发展。明确东北地区宜以天然气作为过渡能源,并提出了适宜地区经济发展的天然气利用建议。  相似文献   
9.
苏戈曼  崔国民  肖媛  赵倩倩 《化工进展》2020,39(10):3879-3891
换热单元的生成频次对换热网络优化有直接的影响,分析其机理可以指导求解算法的改进。本文采用节点非结构模型及强制进化随机游走算法,通过设置不同的换热单元生成概率与生成个数以改变换热单元的生成频次,观察并记录个体在优化过程中产生的年综合费用变化情况。发现不同生成频次下整型变量和连续变量的相对优化频率发生了变化,从而改变了整体优化过程,并且与个体当前优化状态不适应的生成频次会造成相对优化频率不平衡、优化结果较差。基于此,本文提出了一种具有生成参数动态调节策略的换热单元生成方式,在优化过程中根据个体状态实时调整换热单元的生成概率与生成个数,平衡整型变量与连续变量的相对优化频率。最后,采用15SP、10SP和20SP算例进行验证,换热网络的年综合费用较文献结果分别下降了1.06%、0.16%、0.68%,验证了该策略使得换热单元的生成频次更为合理,有效地提高了算法的优化效率。  相似文献   
10.
Controlled tabular adjustment (CTA) is a relatively new protection technique for tabular data protection. CTA formulates a mixed integer linear programming problem, which is challenging for tables of moderate size. Even finding a feasible initial solution may be a challenging task for large instances. On the other hand, end users of tabular data protection techniques give priority to fast executions and are thus satisfied in practice with suboptimal solutions. This work has two goals. First, the fix-and-relax (FR) strategy is applied to obtain good feasible initial solutions to large CTA instances. FR is based on partitioning the set of binary variables into clusters to selectively explore a smaller branch-and-cut tree. Secondly, the FR solution is used as a warm start for a block coordinate descent (BCD) heuristic (approach named FR+BCD); BCD was confirmed to be a good option for large CTA instances in an earlier paper by the second and third co-authors (Comput Oper Res 2011;38:1826–35 [23]). We report extensive computational results on a set of real-world and synthetic CTA instances. FR is shown to be competitive compared to CPLEX branch-and-cut in terms of quickly finding either a feasible solution or a good upper bound. FR+BCD improved the quality of FR solutions for approximately 25% and 50% of the synthetic and real-world instances, respectively. FR or FR+BCD provided similar or better solutions in less CPU time than CPLEX for 73% of the difficult real-world instances.  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