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   55777篇
  免费   5096篇
  国内免费   2684篇
电工技术   3514篇
技术理论   8篇
综合类   3661篇
化学工业   9464篇
金属工艺   2993篇
机械仪表   3304篇
建筑科学   3993篇
矿业工程   1514篇
能源动力   1761篇
轻工业   3492篇
水利工程   1099篇
石油天然气   2841篇
武器工业   646篇
无线电   6960篇
一般工业技术   6801篇
冶金工业   2916篇
原子能技术   716篇
自动化技术   7874篇
  2024年   256篇
  2023年   914篇
  2022年   1811篇
  2021年   2473篇
  2020年   1832篇
  2019年   1533篇
  2018年   1710篇
  2017年   1814篇
  2016年   1627篇
  2015年   2285篇
  2014年   2713篇
  2013年   3446篇
  2012年   3589篇
  2011年   3798篇
  2010年   3337篇
  2009年   3235篇
  2008年   3123篇
  2007年   2959篇
  2006年   2993篇
  2005年   2484篇
  2004年   1859篇
  2003年   1625篇
  2002年   1678篇
  2001年   1537篇
  2000年   1329篇
  1999年   1340篇
  1998年   1164篇
  1997年   994篇
  1996年   805篇
  1995年   675篇
  1994年   506篇
  1993年   435篇
  1992年   333篇
  1991年   266篇
  1990年   184篇
  1989年   179篇
  1988年   144篇
  1987年   89篇
  1986年   88篇
  1985年   77篇
  1984年   33篇
  1983年   27篇
  1982年   37篇
  1981年   34篇
  1980年   23篇
  1979年   21篇
  1977年   16篇
  1976年   19篇
  1974年   13篇
  1973年   14篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
随着设计理论和实践的发展,产品设计中越来越强调以用户为中心的体验式设计。本文应用用户研究和设计心理学的方法,通过研究人们在图书馆使用储物箱的活动,建立出用户心理和行为模型,从而提升用户使用过程中的体验和满意度。  相似文献   
72.
提出了一种新型大规模阵列水声信号采集系统设计方法。该设计基于数据流驱动设计思想,利用FPGA实现了高速LINK口,同时在数据传输中采用独特的两级缓冲结构,因而系统拓扑结构灵活,数据吞吐率高,同时具备同步性能好,扩展性强的特点。  相似文献   
73.
Wong KW  Cheng LM 《Applied optics》1994,33(11):2134-2139
We propose performing space-variant optical logic operations in a space-invariant optical system by selectively assigning encoding states that are operation dependent. With this method, encoders using liquid-crystal cells and liquid-crystal light valves to perform space-variant encoding for all 16 Boolean functions are designed. Multiple-instruction-multiple-data processing can then be realized in optical logic systems.  相似文献   
74.
本文简要叙述了刘家峡电厂水轮机增容改造中的水力研究、结构设计、中间试验、材料选择以及制造工艺等方面内容,并探讨了减轻泥砂磨蚀的措施。该水轮机的增容改造经验对含泥砂河流水轮机的设计与改造是有益的。  相似文献   
75.
Organic redox-active materials are promising electrode candidates for lithium-ion batteries by virtue of their designable structure and cost-effectiveness. However, their poor electrical conductivity and high solubility in organic electrolytes limit the device's performance and practical applications. Herein, the π-conjugated nitrogen-containing heteroaromatic molecule hexaazatriphenylene (HATN) is strategically embedded with redox-active centers in the skeleton of a Cu-based 2D conductive metal–organic framework (2D c-MOF) to optimize the lithium (Li) storage performance of organic electrodes, which delivers improved specific capacity (763 mAh g−1 at 300 mA g−1), long-term cycling stability (≈90% capacity retention after 600 cycles at 300 mA g−1), and excellent rate performance. The correlation of experimental and computational results confirms that this high Li storage performance derives from the maximum number of active sites (CN sites in the HATN unit and CO sites in the CuO4 unit), favorable electrical conductivity, and efficient mass transfer channels. This strategy of integrating multiple redox-active moieties into the 2D c-MOF opens up a new avenue for the design of high-performance electrode materials.  相似文献   
76.
Li-rich layered oxides (LLOs) have been considered as the most promising cathode materials for achieving high energy density Li-ion batteries. However, they suffer from continuous voltage decay during cycling, which seriously shortens the lifespan of the battery in practical applications. This review comprehensively elaborates and summarizes the state-of-the-art of the research in this field. It is started from the proposed mechanism of voltage decay that refers to the phase transition, microscopic defects, and oxygen redox or release. Furthermore, several strategies to mitigate the voltage decay of LLOs from different scales, such as surface modification, elemental doping, regulation of components, control of defect, and morphology design are summarized. Finally, a systematic outlook on the real root of voltage decay is provided, and more importantly, a potential solution to voltage recovery from electrochemistry. Based on this progress, some effective strategies with multiple scales will be feasible to create the conditions for their commercialization in the future.  相似文献   
77.
78.
Chen  Ailin  Yang  Pin  Cheng  Pengsen 《The Journal of supercomputing》2022,78(2):2744-2771

The rumors, advertisements and malicious links are spread in social networks by social spammers, which affect users’ normal access to social networks and cause security problems. Most methods aim to detect social spammers by various features, such as content features, behavior features and relationship graph features, which rely on a large-scale labeled data. However, labeled data are lacking for training in real world, and manual annotating is time-consuming and labor-intensive. To solve this problem, we propose a novel method which combines active learning algorithm with co-training algorithm to make full use of unlabeled data. In co-training, user features are divided into two views without overlap. Classifiers are trained iteratively with labeled instances and the most confident unlabeled instances with pseudo-labels. In active learning, the most representative and uncertain instances are selected and annotated with real labels to extend labeled dataset. Experimental results on the Twitter and Apontador datasets show that our method can effectively detect social spammers in the case of limited labeled data.

  相似文献   
79.
This study focuses on the potential of hydrogen-rich syngas production by CO2 reforming of methane over Co/Pr2O3 catalyst. The Co/Pr2O3 catalyst was synthesized via wet-impregnation method and characterized for physicochemical properties by TGA, XRD, BET, H2-TPR, FESEM, EDX, and FTIR. The CO2 reforming of methane over the as-synthesized catalyst was studied in a tubular stainless steel fixed-bed reactor at feed ratio ranged 0.1–1.0, temperature ranged 923–1023 K, and gas hourly space velocity (GHSV) of 30,000 h?1 under atmospheric pressure condition. The catalyst activity studies showed that the increase in the reaction temperature from 923 to 1023 K and feed ratio from 0.1 to 1.0 resulted in a corresponding increase in the reactant’s conversion and the product’s yields. At 1023 K and feed ratio of 1.0, the activity of the Co/Pr2O3 catalyst climaxed with CH4 and CO2 conversions of 41.49 and 42.36 %. Moreover, the catalyst activity at 1023 K and feed ratio of 1.0 resulted in the production of H2 and CO yields of 40.7 and 40.90 %, respectively. The syngas produced was estimated to have H2:CO ratio of 0.995, making it suitable as chemical building blocks for the production of oxygenated fuel and other value-added chemicals. The used Co/Pr2O3 catalyst which was characterized by TPO, XRD, and SEM-EDX show some evidence of carbon formation and deposition on its surface.  相似文献   
80.
曹小琴  邓韵  翟橙  魏晓 《包装工程》2017,38(18):114-118
目的控制器和显示器共同组成数控机床控制面板的整体界面,是机床接受与执行命令的交互平台。从人机交互角度,聚焦于控制器的界面布局进行优化设计。方法基于人机工程学理论的优化流程,采用现场访谈、现场观察等方法,将人机工程学的理论转化为具体考核指标。结论从人机工程学的研究角度出发,结合工业设计、用户体验设计学等内容,从功能区域分区、操纵器色彩设计等方面优化数控机床控制器的界面,提高系统整体效能及使用者满意度,为数控机床系统开发设计提供参考。  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