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   87971篇
  免费   9223篇
  国内免费   6203篇
电工技术   7660篇
技术理论   3篇
综合类   8505篇
化学工业   11552篇
金属工艺   5757篇
机械仪表   6206篇
建筑科学   6620篇
矿业工程   3140篇
能源动力   2267篇
轻工业   9244篇
水利工程   2642篇
石油天然气   3255篇
武器工业   1087篇
无线电   9030篇
一般工业技术   7963篇
冶金工业   3634篇
原子能技术   1411篇
自动化技术   13421篇
  2024年   392篇
  2023年   1194篇
  2022年   2825篇
  2021年   3869篇
  2020年   2792篇
  2019年   1977篇
  2018年   2197篇
  2017年   2561篇
  2016年   2353篇
  2015年   3764篇
  2014年   4613篇
  2013年   5626篇
  2012年   6841篇
  2011年   7276篇
  2010年   7047篇
  2009年   6933篇
  2008年   6910篇
  2007年   6816篇
  2006年   5947篇
  2005年   4951篇
  2004年   3680篇
  2003年   2644篇
  2002年   2494篇
  2001年   2291篇
  2000年   1764篇
  1999年   986篇
  1998年   517篇
  1997年   432篇
  1996年   346篇
  1995年   256篇
  1994年   232篇
  1993年   182篇
  1992年   136篇
  1991年   127篇
  1990年   75篇
  1989年   80篇
  1988年   54篇
  1987年   34篇
  1986年   35篇
  1985年   20篇
  1984年   24篇
  1983年   14篇
  1982年   7篇
  1981年   13篇
  1980年   28篇
  1979年   13篇
  1976年   2篇
  1959年   12篇
  1958年   2篇
  1951年   12篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
谢富金  万宜勇 《水泥》2008,(1):44-45
我公司于2005年7月投产后,部分计量设备由于设计不完善,安装不合理,导致计量不稳定.在此,通过总结,给出解决措施、技改方案及建议.  相似文献   
2.
Previous work has shown that the enzymatic hydrolysis of sugarcane bagasse could be greatly enhanced by peracetic acid (PAA) pretreatment. There are several factors affecting the enzymatic digestibility of the biomass, including lignin and hemicelluloses content, cellulose crystallinity, acetyl group content, accessible surface area and so on. The objective of this work is to analyze the mechanism of the enhancement of enzymatic digestibility caused by PAA pretreatment. Delignification resulted in an increase of the surface area and reduction of the irreversible absorption of cellulase, which helped to increase the enzymatic digestibility. The Fourier transform infrared (FTIR) spectrum showed that the absorption peaks of aromatic skeletal vibrations were weakened or disappeared after PAA pretreatment. However, the infrared crystallization index (N.O'KI) was increased. X‐ray diffraction (XRD) analysis indicated that the crystallinity of PAA‐treated samples was increased owing to the partial removal of amorphous lignin and hemicelluloses and probable physical change of cellulose. The effect of acetyl group content on enzymatic digestibility is negligible compared with the degree of delignification and crystallinity. The results indicate that enhancement of enzymatic digestibility of sugarcane bagasse by PAA pretreatment is achieved mainly by delignification and an increase in the surface area and exposure of cellulose fibers. Copyright © 2008 Society of Chemical Industry  相似文献   
3.
This work was aimed at studying the overall, partial, and local residence time distributions (RTD); overall, partial and local residence revolution distributions (RRD) and overall, partial and local residence volume distributions (RVD) in a co‐rotating twin screw extruder, on the one hand; and establishing the relationships among them, on the other hand. Emphasis was placed on the effects of the type and geometry of mixing elements (a gear block and various types of kneading elements differing in staggering angle) and process parameters on the RTD, RRD and RVD. The overall and partial RTD were directly measured in‐line during the extrusion process and the local ones were calculated by deconvolution based on a statistical theory. The local RTD allowed comparing the mixing performance of mixing elements. Also it was confirmed both experimentally and theoretically that specific throughput, defined as a ratio of throughput (Q) over screw speed (N), controlled all the above three types of residence distributions, be they local, partial or overall. The RRD and RVD do not provide more information on an extrusion process than the corresponding RTD. Rather they are different ways of representing the same phenomena. POLYM. ENG. SCI., 48:19–28, 2008. © 2007 Society of Plastics Engineers  相似文献   
4.
试图构建企业以顾客为中心的营销策略过程的一般模型,并利用已有的研究成果对其构成要素进行了深入分析.在此基础上,对此模型所形成的企业营销策略循环进行分类分析,并以实例说明它们所代表的现实意义,从而为企业的决策提供帮助.  相似文献   
5.
6.
以某企业后桥壳生产线为研究对象,运用作业测定技术中的时间研究法,测定后桥壳各工序的标准时间,评价工艺及找到瓶颈工序;运用"5W1H"提问技术,根据"ECRS"原则,同时结合工艺设计及企业资源情况,对后桥壳生产线现有工艺进行评价及优化,改善后,使生产线的产能每天提高了10件,生产能力提高了33.57%.  相似文献   
7.
A theoretical construction of one-to-many (OTM) and many-to-one (MTO) chaos synchronization communications using semiconductor lasers is presented. One center laser provides strong injections (strong link) to other side lasers, and the side lasers also provide weak injections (weak link) to the center one. Simulation results show that the side lasers synchronize with the center laser through injection-locking. In addition, messages transmitted via the strong links or the weak links experience strong chaos pass filtering, enabling us to realize OTM and MTO communications.  相似文献   
8.
影响混凝土强度的因素及控制措施   总被引:3,自引:3,他引:0  
分析了水泥强度等级、水灰比和骨料质量等内因,及施工条件、养护温度、湿度、龄期等外因对混凝土强度的影响,并提出了控制混凝土强度的相应措施,以确保混凝土强度符合设计及施工要求,从而保证建筑物结构安全。  相似文献   
9.
A space-time optimal power schedule for multiple distributed multiple-input multiple-output (MIMO) links without the knowledge of the instantaneous channel state information (CSI) at the transmitting nodes is proposed. A readily computable expression for the ergodic sum capacity of the MIMO links is derived. Based on this expression, which is a non-convex function of power allocation vectors, a projected gradient algorithm is developed to optimize the power allocation. For a symmetric set of MIMO links with independent identically distributed channels, it is observed that the space-time optimal power schedule reduces to a uniform isotropic power schedule when nominal interference is low, or to an orthogonal isotropic power schedule when nominal interference is high. Furthermore, the transition region between the latter two schedules is seen to be very sharp in terms of nominal interference-to-noise ratio (INR). For MIMO links with correlated channels, the corresponding space-time optimal power schedule is developed based on the knowledge of the channel correlation matrices. It is shown that the channel correlation has a great impact on the ergodic capacity and the optimality of different power scheduling approaches.  相似文献   
10.
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