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   247240篇
  免费   5095篇
  国内免费   601篇
电工技术   3801篇
综合类   164篇
化学工业   39835篇
金属工艺   11018篇
机械仪表   7851篇
建筑科学   5201篇
矿业工程   2252篇
能源动力   5326篇
轻工业   19781篇
水利工程   3360篇
石油天然气   7878篇
武器工业   29篇
无线电   23103篇
一般工业技术   52153篇
冶金工业   44554篇
原子能技术   6756篇
自动化技术   19874篇
  2021年   2968篇
  2020年   2393篇
  2019年   2945篇
  2018年   5373篇
  2017年   5362篇
  2016年   5726篇
  2015年   3550篇
  2014年   5332篇
  2013年   12038篇
  2012年   8109篇
  2011年   9363篇
  2010年   7681篇
  2009年   8116篇
  2008年   8226篇
  2007年   7985篇
  2006年   6581篇
  2005年   5998篇
  2004年   5481篇
  2003年   5305篇
  2002年   5073篇
  2001年   4968篇
  2000年   4643篇
  1999年   4755篇
  1998年   13200篇
  1997年   9236篇
  1996年   6822篇
  1995年   4887篇
  1994年   4204篇
  1993年   4546篇
  1992年   3228篇
  1991年   3254篇
  1990年   3087篇
  1989年   3057篇
  1988年   3070篇
  1987年   2682篇
  1986年   2734篇
  1985年   3056篇
  1984年   2841篇
  1983年   2676篇
  1982年   2460篇
  1981年   2462篇
  1980年   2539篇
  1979年   2454篇
  1978年   2477篇
  1977年   2831篇
  1976年   3605篇
  1975年   2245篇
  1974年   2122篇
  1973年   2240篇
  1972年   1968篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
Refractories and Industrial Ceramics - The paper introduces a promising technology for utilizing a traditional scheme for implementing a flow-through micro-arc oxidation method to restore localized...  相似文献   
5.
Combustion, Explosion, and Shock Waves - Results of a numerical study of mixing, ignition, and combustion of a cold hydrogen jet propagating along the lower wall of a channel parallel to a...  相似文献   
6.
Multimedia Tools and Applications - The three-dimensional models of brain tumors serve as diagnostic assistance for physicians, surgeons, and radiologists. The proposed system establishes an...  相似文献   
7.
Journal of Chemical Ecology - Biocontrol agents such as parasitic wasps use long-range volatiles and host-associated cues from lower trophic levels to find their hosts. However, this chemical...  相似文献   
8.
Water Resources Management - The water evaluation and planning (WEAP) approach and the invasive weed optimization algorithm (IWOA) are herein employed to determine the optimal operating policies in...  相似文献   
9.
Photoresponsive biomaterials are experiencing a transition from in vitro models to in vivo demonstrations that point toward clinical translation. Dynamic hydrogels for cell encapsulation, light-responsive carriers for controlled drug delivery, and nanomaterials containing photosensitizers for photodynamic therapy are relevant examples. Nonetheless, the step to the clinic largely depends on their combination with technologies to bring light into the body. This review highlights the challenge of photoactivation in vivo, and presents strategies for light management that can be adopted for this purpose. The authors’ focus is on technologies that are materials-driven, particularly upconversion nanoparticles that assist in “direct path” light delivery through tissue, and optical waveguides that “clear the path” between external light source and in vivo target. The authors’ intention is to assist the photoresponsive biomaterials community transition toward medical technologies by presenting light delivery concepts that can be integrated with the photoresponsive targets. The authors also aim to stimulate further innovation in materials-based light delivery platforms by highlighting needs and opportunities for in vivo photoactivation of biomaterials.  相似文献   
10.
The constructive analysis of Madrid's old timber-framed collective courtyard buildings, whether demolished, preserved intact, or enlarged, has achieved the dating of relevant case studies. New parameters established in this study set a chronology based on front sector original projects: old (1737–1788), pre-modern (1788–1847) and modern (1847–1892). The on-site inspection and archival research point to ongoing misleading construction in the historic Southern area. Some modern corralas erected on top of pre-existing buildings confirm the initial hypothesis. First dimensioning rules for new façades and the stability required in old ones before adding new storeys, maintaining the original masonry or double-layered system, are discovered. Undated buildings suggest their possible origin a la malicia and a later transformation into transitional corralas. Finally, an analysis of the demolished courtyards narrows down the dating and points to new conjectures in some preserved by showing their uneven layout, old features, and structural discordances in each sector.  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