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   43814篇
  免费   4505篇
  国内免费   2392篇
电工技术   3287篇
技术理论   2篇
综合类   3505篇
化学工业   6802篇
金属工艺   2513篇
机械仪表   2808篇
建筑科学   3486篇
矿业工程   1259篇
能源动力   1172篇
轻工业   3821篇
水利工程   860篇
石油天然气   2296篇
武器工业   480篇
无线电   5286篇
一般工业技术   4555篇
冶金工业   1806篇
原子能技术   774篇
自动化技术   5999篇
  2024年   263篇
  2023年   846篇
  2022年   1757篇
  2021年   2237篇
  2020年   1716篇
  2019年   1387篇
  2018年   1509篇
  2017年   1619篇
  2016年   1459篇
  2015年   1903篇
  2014年   2376篇
  2013年   2610篇
  2012年   2966篇
  2011年   3082篇
  2010年   2787篇
  2009年   2667篇
  2008年   2677篇
  2007年   2455篇
  2006年   2412篇
  2005年   2059篇
  2004年   1384篇
  2003年   1278篇
  2002年   1347篇
  2001年   1213篇
  2000年   969篇
  1999年   804篇
  1998年   490篇
  1997年   482篇
  1996年   440篇
  1995年   299篇
  1994年   277篇
  1993年   214篇
  1992年   199篇
  1991年   111篇
  1990年   87篇
  1989年   84篇
  1988年   67篇
  1987年   48篇
  1986年   31篇
  1985年   18篇
  1984年   20篇
  1983年   16篇
  1982年   13篇
  1981年   9篇
  1980年   12篇
  1979年   4篇
  1959年   6篇
  1951年   2篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
52.
Electric conductive and microwave absorbing material PANI/Ni/CF was prepared by in situ polymerization of polyaniline on the surface of nickel-coated carbon fiber (Ni/CF). The morphologies and structures of CF, Ni/CF, PANI and PANI/Ni/CF were characterized by scanning electron microscope and X-ray diffraction. Results show that the CF was wrapped tightly around the nickel layer, and the Ni/CF was coated by PANI. Measurement of four probes resistance tester indicates that the electrical conductivity of PANI/Ni/CF was great improved compared with PANI and PANI/CF. Vibrating sample magnetometry shows that the magnetic saturation intensity of Ni/CF and PANI/Ni/CF was 13.8 and 2.3 emu/g, respectively. According to the vector network analyzer, the microwave absorbing properties of PANI/Ni/CF were better than those of PANI and PANI/CF, and its minimum loss value is ?12.4 dB at 8.8 GHz.  相似文献   
53.
The self-assembly of peptidyl virus-like nanovesicles (pVLNs) composed of highly ordered peptide bilayer membranes that encapsulate the small interfering RNA (siRNA) is reported. The targeting and enzyme-responsive sequences on the bilayer's surface allow the pVLNs to enter cancer cells with high efficiency and control the release of genetic drugs in response to the subcellular environment. By transforming its structure in response to the highly expressed enzyme matrix metalloproteinase 7 (MMP-7) in cancer cells, it helps the siRNA escape from the lysosomes, resulting in a final silencing efficiency of 92%. Moreover, the pVLNs can serve as reconfigurable “Trojan horse” by transforming into membranes triggered by the MMP-7 and disrupting the cytoplasmic structure, thereby achieving synergistic anticancer effects and 96% cancer cell mortality with little damage to normal cells. The pVLNs benefit from their biocompatibility, targeting, and enzyme responsiveness, making them a promising platform for gene therapy and anticancer therapy.  相似文献   
54.
介绍荣信钢铁转炉过程控制系统的组成、系统功能、技术应用。  相似文献   
55.
博物馆建筑,是一个城市文化的象征,如何使博物馆具有文化感,体现传统的审美文化,又具有新的设计元素,引导人类审美意识,苏州博物馆与宁波博物馆做了比较好的探索。  相似文献   
56.
提出一种以词性为参考值的文本挖掘算法,能有效挖掘与种子词有关的关联规则。基于Bootstrapping算法思想,既减少了预处理阶段对于词根还原的依赖,能处理日志中出现的中文词汇。增加了对于日志文本上下的理解,提高了关联规则的有效性,并应用与IDS日志挖掘之中,有效改善挖掘效率,为规则库提供关联规则。  相似文献   
57.
This paper is devoted to investigating inventory control problems under nonstationary and uncertain demand. A belief-rule-based inventory control (BRB-IC) method is developed, which can be applied in situations where demand and demand-forecast-error (DFE) do not follow certain stochastic distribution and forecasting demand is given in single-point or interval styles. The method can assist decision-making through a belief-rule structure that can be constructed, initialized and adjusted using both manager’s knowledge and operational data. An extended optimal base stock (EOBS) policy is proved for initializing the belief-rule-base (BRB), and a BRB-IC inference approach with interval inputs is proposed. A numerical example and a case study are examined to demonstrate potential applications of the BRB-IC method. These studies show that the belief-rule-based expert system is flexible and valid for inventory control. The case study also shows that the BRB-IC method can compensate DFE by training BRB using historical demand data for generating reliable ordering policy.  相似文献   
58.
Visual media data such as an image is the raw data representation for many important applications. Reducing the dimensionality of raw visual media data is desirable since high dimensionality degrades not only the effectiveness but also the efficiency of visual recognition algorithms. We present a comparative study on spatial interest pixels (SIPs), including eight-way (a novel SIP detector), Harris, and Lucas‐Kanade, whose extraction is considered as an important step in reducing the dimensionality of visual media data. With extensive case studies, we have shown the usefulness of SIPs as low-level features of visual media data. A class-preserving dimension reduction algorithm (using GSVD) is applied to further reduce the dimension of feature vectors based on SIPs. The experiments showed its superiority over PCA.
Chandra KambhamettuEmail:
  相似文献   
59.
60.
一、生态足迹视野下的四大城市发展弊端加拿大不列颠哥伦比亚大学社区与区域规划学院教授WilliamRees(威廉姆?里斯)2012年3月7日在纽卡斯尔大学建筑规划景观学院发表演讲,提出了"可持续性的障碍是什么?为什么我们如梦游一般走入全球生态危机之中?"的设问。他从生态足迹分析角度,指出了现代城市  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