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   28759篇
  免费   2606篇
  国内免费   1425篇
电工技术   1737篇
技术理论   1篇
综合类   2286篇
化学工业   4882篇
金属工艺   1754篇
机械仪表   1814篇
建筑科学   2338篇
矿业工程   791篇
能源动力   786篇
轻工业   2024篇
水利工程   583篇
石油天然气   1395篇
武器工业   273篇
无线电   3178篇
一般工业技术   3371篇
冶金工业   1276篇
原子能技术   255篇
自动化技术   4046篇
  2024年   117篇
  2023年   403篇
  2022年   645篇
  2021年   1005篇
  2020年   732篇
  2019年   706篇
  2018年   745篇
  2017年   786篇
  2016年   704篇
  2015年   1073篇
  2014年   1240篇
  2013年   1492篇
  2012年   1714篇
  2011年   1837篇
  2010年   1698篇
  2009年   1772篇
  2008年   1657篇
  2007年   1616篇
  2006年   1771篇
  2005年   1444篇
  2004年   1116篇
  2003年   1198篇
  2002年   1435篇
  2001年   1224篇
  2000年   792篇
  1999年   804篇
  1998年   571篇
  1997年   458篇
  1996年   453篇
  1995年   395篇
  1994年   283篇
  1993年   241篇
  1992年   179篇
  1991年   112篇
  1990年   93篇
  1989年   79篇
  1988年   64篇
  1987年   38篇
  1986年   14篇
  1985年   20篇
  1984年   14篇
  1983年   12篇
  1982年   13篇
  1981年   6篇
  1980年   12篇
  1979年   3篇
  1978年   1篇
  1951年   3篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
951.
Starch–gluten interactions are affected by biopolymer type and processing. However, the differentiation mechanisms for gluten–starch interactions during heating have not been illuminated. The effects of glutens from two different wheat flours (a weak-gluten (Yangmai 22, Y22) and a medium-strong gluten (Yangmai 16, Y16)) on starch’s (S) structural and physicochemical properties during heating and their molecular interactions were investigated in this study. The results showed that gluten hindered the gelatinization and swelling of starch during heating when temperature was below 75 °C, due to competitive hydration and physical barriers of glutens, especially in Y22. Thus, over-heating caused the long-range molecular order and amylopectin branches of starch to be better preserved in the Y22-starch mixture (Y22-S) than in the Y16-starch mixture (Y16-S). Meanwhile, the starch’s degradation pattern during heating in turn influenced the polymerization of both glutens. During heating, residual amylopectin branching points restricted the aggregation and cross-linking of gluten proteins due to steric hindrance. More intense interaction between Y16 and starch during heating mitigated the steric hindrance in starch–gluten networks, which was due to more residual short-range ordered starch and hydrogen bonds involved in the formation of starch–gluten networks in Y16-S during heating.  相似文献   
952.
The formation of neurofibrillary tangles (NFT) with β-sheet-rich structure caused by abnormal aggregation of misfolded microtubule-associated protein Tau is a hallmark of tauopathies, including Alzheimer’s Disease. It has been reported that acetylation, especially K174 located in the proline-rich region, can largely promote Tau aggregation. So far, the mechanism of the abnormal acetylation of Tau that affects its misfolding and aggregation is still unclear. Therefore, revealing the effect of acetylation on Tau aggregation could help elucidate the pathogenic mechanism of tauopathies. In this study, molecular dynamics simulation combined with multiple computational analytical methods were performed to reveal the effect of K174 acetylation on the spontaneous aggregation of Tau peptide 171IPAKTPPAPK180, and the dimerization mechanism as an early stage of the spontaneous aggregation was further specifically analyzed by Markov state model (MSM) analysis. The results showed that both the actual acetylation and the mutation mimicking the acetylated state at K174 induced the aggregation of the studied Tau fragment; however, the effect of actual acetylation on the aggregation was more pronounced. In addition, acetylated K174 plays a major contributing role in forming and stabilizing the antiparallel β-sheet dimer by forming several hydrogen bonds and side chain van der Waals interactions with residues I171, P172, A173 and T175 of the corresponding chain. In brief, this study uncovered the underlying mechanism of Tau peptide aggregation in response to the lysine K174 acetylation, which can deepen our understanding on the pathogenesis of tauopathies.  相似文献   
953.
Ultra-high-purity silicon tetrachloride (SiCl4) is demanded as an electronic-grade chemical to meet the stringent requirements of the rapidly developing semiconductor industry. The high requirement for ultra-high-purity SiCl4 has created the need for a high-efficient process for reducing energy consumption as well as satisfying product quality. In this paper, a mass of production technology of ultra-high-purity SiCl4 was successfully developed through chlorination reaction in the ultraviolet (UV)-based photo microreactor coupled with the distillation process. The influences of key operational parameters, including temperature, pressure, UV wavelength and light intensity on the product quality, especially for hydrogen-containing impurities, were quantified by the infrared transmittance of Fourier transform infrared spectroscopy (FT-IR) at 2185 cm-1 and 2160 cm-1 indicating that characteristic vibrational modes of Si—H bonds, as well as the operating conditions of distillation were also investigated as key factors for metal impurities removing. The advanced intensification of SiCl4 manufactured by the integration of photo microreactor and distillation achieves the products with superior specifications higher than the standard commercial products.  相似文献   
954.
955.
为解决传统模式下电力系统倒闸操作存在效率低、人力成本高的缺点,设计一种以服务机器人为平台并具有远程移动监控功能的倒闸服务机器人系统.系统本地端以搭载Android系统的ARM Cotex-A8工业开发板为主控模块,利用JNI技术实现ARM主控模块与专门定制的硬件功能模块交互通信;系统远程监控端以搭载Android系统的智能手机为远程移动监控平台,通过WiFi或3G/4G移动网络实现与服务机器人本地端网络通信.测试结果表明:服务机器人系统可以辅助倒闸操作并且实时远程监控,具有较高的可靠性、稳定性及管理的灵活性.  相似文献   
956.
直接序列扩频信号(direct sequence spread spectrum,DSSS)是抗干扰低截获概率信号,实现其参数的估计具有重要意义。针对直扩信号载频、码元速率、相位的估计问题,结合谱相关的基本理论,提出了对直扩信号载频、码元速率、相位估计的谱相关方法。理论分析和仿真结果表明:在没有伪随机码序列及相关参数先验信息的条件下,该方法能够完成低信噪比时对信号的检测和载频、码速率、初相的估计,可有效提高计算效率。  相似文献   
957.
提出了一种基于混沌电路的随机脉位调制(RPPM)和随机二相码调相(RBCPM)混合调制的雷达引信系统。介绍了该引信波形的数学模型,平均模型函数及引信的实现框图和工作原理,研究了基于混沌电路的混合调制信号的产生方法,这种引信波形不仅具有结构简单和易于处理等特点,而且具有良好的测距和测速性能,以及极低的截获概率和很强的抗干扰特性。  相似文献   
958.
为提高烟花自动生产线中最易出现爆炸的混药工序的安全性及混药质量,提出滚筒制备发射药、响药的技术。介绍混药机的主要功能,分析其工作原理和结构,给出其工艺流程,列出混药滚筒及有效装载容量的计算方法。结果表明:该技术能实现烟花药剂的自动混药及出药功能,保证药剂混合均匀,配比精确,实现人机隔离和无人化生产,达到预期的设计要求,并已应用于双响炮自动装药装配生产线中。  相似文献   
959.
王毅  赵忠  卫育新 《兵工自动化》2005,24(4):56-56,58
带误差补偿的二位置寻北仪系统包括电源、转机结构、控制电路、计数器等.其补偿算法推导基于陀螺和加速度计一次误差补偿模型,以降低陀螺随机漂移及加速度计的零位漂移对寻北精度的影响.同时再利用由典型静态误差源产生的寻北误差与方位角三角函数成正比或为常值,以罗差修正寻北结果进一步提高寻北精度.  相似文献   
960.
一种橄榄果酒的发酵工艺研究   总被引:2,自引:0,他引:2  
以新鲜橄榄为原料,榨汁后采用果酒酿造工艺进行发酵,获得具有橄榄独特风味的橄榄酒。考察了酵母接种量、初始糖度、初始pH值、发酵温度、SO2添加量对橄榄酒感官评价的影度21℃,酵母接种量7%,SO2添加量70 mg/L,初始pH值3.7,初始糖度18°Bx。  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