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   151523篇
  免费   13901篇
  国内免费   6510篇
电工技术   8423篇
综合类   9347篇
化学工业   23825篇
金属工艺   7015篇
机械仪表   6981篇
建筑科学   7881篇
矿业工程   3867篇
能源动力   4021篇
轻工业   20857篇
水利工程   3605篇
石油天然气   3217篇
武器工业   1573篇
无线电   10291篇
一般工业技术   16346篇
冶金工业   23036篇
原子能技术   1735篇
自动化技术   19914篇
  2024年   614篇
  2023年   1960篇
  2022年   4520篇
  2021年   6132篇
  2020年   4439篇
  2019年   3574篇
  2018年   4562篇
  2017年   4722篇
  2016年   4697篇
  2015年   5635篇
  2014年   7014篇
  2013年   10275篇
  2012年   10742篇
  2011年   11092篇
  2010年   10055篇
  2009年   9222篇
  2008年   9234篇
  2007年   8778篇
  2006年   7257篇
  2005年   5774篇
  2004年   4534篇
  2003年   3405篇
  2002年   3063篇
  2001年   2597篇
  2000年   2240篇
  1999年   1586篇
  1998年   6548篇
  1997年   4126篇
  1996年   2723篇
  1995年   1558篇
  1994年   1298篇
  1993年   1405篇
  1992年   427篇
  1991年   432篇
  1990年   352篇
  1989年   377篇
  1988年   353篇
  1987年   319篇
  1986年   274篇
  1985年   303篇
  1984年   211篇
  1983年   167篇
  1982年   221篇
  1981年   246篇
  1980年   294篇
  1979年   126篇
  1978年   119篇
  1977年   553篇
  1976年   1111篇
  1973年   105篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
直通链路技术己广泛应用于车联网场景。对于直通链路技术的潜在技术方向给出可行的建议,包括传统直通链路技术的增强方向,如载波聚合、使用非授权频谱等;侧行链路对于中继场景的应用扩展,包括终端到终端之间的中继,以及中继的多链接场景;在高精度定位场景使用直通链路技术。并且,给出直通链路技术与各种新技术的融合应用,如智能反射面与区块链技术,从而解决直通链路技术自身的缺陷。  相似文献   
5.
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   
6.
高环  马方晨  冯理成 《现代导航》2022,13(4):292-296
随着通信、计算机、人工智能和传感器等技术的飞速发展与广泛应用,地面无人装备日趋活跃在作战、搜救和消防等多种军民用任务场景中。对于军事领域而言,地面无人装备是陆军和其他地面作战部队迈向无人化、智能化战场的核心装备,将在未来陆战场各类作战任务中发挥不可替代的作用。通过对外军各类典型地面无人装备发展现状进行深入分析,总结出该装备领域的发展特点与趋势,对地面无人装备发展有一定的借鉴意义。  相似文献   
7.
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   
8.
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   
9.
Our aim was to investigate the subset distribution and function of circulating monocytes, proinflammatory cytokine levels, gut barrier damage, and bacterial translocation in chronic spinal cord injury (SCI) patients. Thus, 56 SCI patients and 28 healthy donors were studied. The levels of circulating CD14+highCD16, CD14+highCD16+, and CD14+lowCD16+ monocytes, membrane TLR2, TLR4, and TLR9, phagocytic activity, ROS generation, and intracytoplasmic TNF-α, IL-1, IL-6, and IL-10 after lipopolysaccharide (LPS) stimulation were analyzed by polychromatic flow cytometry. Serum TNF-α, IL-1, IL-6 and IL-10 levels were measured by Luminex and LPS-binding protein (LBP), intestinal fatty acid-binding protein (I-FABP) and zonulin by ELISA. SCI patients had normal monocyte counts and subset distribution. CD14+highCD16 and CD14+highCD16+ monocytes exhibited decreased TLR4, normal TLR2 and increased TLR9 expression. CD14+highCD16 monocytes had increased LPS-induced TNF-α but normal IL-1, IL-6, and IL-10 production. Monocytes exhibited defective phagocytosis but normal ROS production. Patients had enhanced serum TNF-α and IL-6 levels, normal IL-1 and IL-10 levels, and increased circulating LBP, I-FABP, and zonulin levels. Chronic SCI patients displayed impaired circulating monocyte function. These patients exhibited a systemic proinflammatory state characterized by enhanced serum TNF-α and IL-6 levels. These patients also had increased bacterial translocation and gut barrier damage.  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