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   57844篇
  免费   4877篇
  国内免费   2255篇
电工技术   3187篇
技术理论   5篇
综合类   3260篇
化学工业   10108篇
金属工艺   3455篇
机械仪表   3456篇
建筑科学   4113篇
矿业工程   1898篇
能源动力   1823篇
轻工业   4281篇
水利工程   984篇
石油天然气   3990篇
武器工业   430篇
无线电   6316篇
一般工业技术   6928篇
冶金工业   3122篇
原子能技术   702篇
自动化技术   6918篇
  2024年   310篇
  2023年   1108篇
  2022年   2028篇
  2021年   2782篇
  2020年   1996篇
  2019年   1701篇
  2018年   1902篇
  2017年   2035篇
  2016年   1780篇
  2015年   2355篇
  2014年   2940篇
  2013年   3352篇
  2012年   3533篇
  2011年   3845篇
  2010年   3403篇
  2009年   3051篇
  2008年   2960篇
  2007年   2873篇
  2006年   3040篇
  2005年   2587篇
  2004年   1633篇
  2003年   1415篇
  2002年   1316篇
  2001年   1040篇
  2000年   1244篇
  1999年   1517篇
  1998年   1217篇
  1997年   1037篇
  1996年   1046篇
  1995年   907篇
  1994年   727篇
  1993年   477篇
  1992年   377篇
  1991年   304篇
  1990年   245篇
  1989年   199篇
  1988年   178篇
  1987年   112篇
  1986年   96篇
  1985年   63篇
  1984年   56篇
  1983年   41篇
  1982年   33篇
  1981年   32篇
  1980年   21篇
  1979年   7篇
  1978年   7篇
  1977年   10篇
  1976年   14篇
  1959年   4篇
排序方式: 共有10000条查询结果,搜索用时 109 毫秒
51.
介绍了如何体现产品质量及如何控制产品质量。  相似文献   
52.
本文通过对二氧化硫的形成及危害的阐述,以及对我市近几年大气中二氧化硫监测结果的分析,针对发展趋势和存在的问题,根据实际情况提出相应的建议。  相似文献   
53.
Centimeter-size multi-branched tree-like carbon structures have been generated by the catalytic chemical vapor deposition of toluene using ferrocene as the catalyst precursor and investigated by means of SEM, TEM, and EDX. It is found that a temperature of 1000-1200 °C and a carrier gas flow rate of 1000-2500 ml/min are necessary for the generation of the carbon trees. Their morphologies and microstructures change greatly with the changing reaction conditions. The fractal dimensions of the trees are calculated to quantitatively investigate the influence of different reaction temperatures on the morphologies.  相似文献   
54.
The confined etchant layer technique has been applied to fabricate complex three-dimensional microstructures on nitinol for the first time. HF and HNO3 were locally and simultaneously electrogenerated at the mold surface to etch a nitinol workpiece. NaOH was used as an efficient scavenger to confine the etchant close to the mold. Cyclic voltammetry was employed to study the electrochemical behavior of a Pt electrode in the etching solution in order to choose an appropriate potential for etchant generation on the mold. The thickness of the confined etchant layer was estimated to be several micrometers by inspecting the deviation of the sizes of the etched spots from the sizes of those on the microelectrode. Thus, the composition of the electrolyte could be optimized for better etching precision. By optimizing the composition of the electrolyte, complex microstructures on a Pt-Ir mold bearing the logo “XMU” of Xiamen University were successfully fabricated on nitinol. The etched patterns were approximately negative copies of the mold, and the precision of duplication could easily reach the micrometer scale.  相似文献   
55.
Video Shot Boundary Detection (SBD) is the fundamental process towards video summarization and retrieval. A fast and efficient SBD algorithm is necessary for real-time video processing applications. Extensive work has focused on accurate shot boundary detection at the expense of demanding computational costs. In this paper, we propose a fast SBD approach that reduces the computation pixel-wise and frame-wise while still giving satisfactory accuracy. The proposed approach substantially speeds up the computation through reducing both detection region and scope. Color histogram and mutual information are used together to measure the difference between frames. Corner distribution of frames is utilized to exclude most of false boundaries. We conduct extensive experiments to evaluate the proposed approach, and the results show that our approach can not only speed up SBD, but also detect shot boundaries with high accuracy in both Cut (CUT) and Gradual Transition (GT) boundaries.  相似文献   
56.
在当今社会,校园体育教育得到了社会各界的关注。21世纪是需要创新的年代,而校园体育教育需要更多的资源支持。简要介绍了校园体育教育资源共享的趋势,论述了校园体育教育资源共享的必要性,阐述了校园体育教育资源共享的必然性和可行性。  相似文献   
57.
Well-crystallized bismuth tungstate (Bi2WO6) powders with different morphologies were successfully synthesized via a low-temperature molten salt method. The powders were characterized by X-ray diffraction, transmission electron microscopy, and UV-Vis, respectively. It was found that the variation of morphology of the obtained Bi2WO6 powder mainly depends on the different reaction temperatures and the weight ratio of LiNO3–NaNO3 salt to precursor. In addition, the UV-Visible absorption spectra showed that the synthesized powders had strong light absorption properties not only in the ultraviolet light but also in the visible light region.  相似文献   
58.
通过全球化与社会主义的逻辑关系以及二者相互关系的历史考察与分析,具体阐释了全球化对社会主义的积极影响和全球化下的社会主义价值,论述了全球化下社会主义的发展状况,探讨了全球化的前景和发展社会主义的战略。  相似文献   
59.
AADL 测试模型的构造研究   总被引:1,自引:0,他引:1  
目前,结构分析和设计语言AADL在任务关键嵌入式系统领域有着良好的应用.为了保障任务关键软件的质量,文章提出基于AADL测试模型对AADL设计模型进行测试,以发现设计模型中存在的错误.研究给出了体现系统拓扑结构的AADL测试模型的形式定义及由AADL构造该测试模型的算法,基于该测试模型可以对AADL设计模型中构件交互的输入、输出端口序列和连接的正确性进行测试,并以飞行控制系统的AADL设计模型为例,阐释了研究成果.  相似文献   
60.
In this paper, we propose a new hard problem, called bilateral inhomogeneous small integer solution (Bi-ISIS), which can be seen as an extension of the small integer solution problem on lattices. The main idea is that, instead of choosing a rectangle matrix, we choose a square matrix with small rank to generate Bi-ISIS problem without affecting the hardness of the underlying SIS problem. Based on this new problem, we present two new hardness problems: computational Bi-ISIS and decisional problems. As a direct application of these problems, we construct a new lattice-based key exchange (KE) protocol, which is analogous to the classic Diffie- Hellman KE protocol. We prove the security of this protocol and show that it provides better security in case of worst-case hardness of lattice problems, relatively efficient implementations, and great simplicity.  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