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   45606篇
  免费   2728篇
  国内免费   46篇
电工技术   359篇
综合类   26篇
化学工业   9822篇
金属工艺   894篇
机械仪表   980篇
建筑科学   1383篇
矿业工程   94篇
能源动力   1112篇
轻工业   7609篇
水利工程   435篇
石油天然气   171篇
武器工业   5篇
无线电   1848篇
一般工业技术   7512篇
冶金工业   9321篇
原子能技术   225篇
自动化技术   6584篇
  2024年   76篇
  2023年   372篇
  2022年   788篇
  2021年   1293篇
  2020年   952篇
  2019年   1109篇
  2018年   1798篇
  2017年   1756篇
  2016年   1834篇
  2015年   1367篇
  2014年   1699篇
  2013年   3437篇
  2012年   2682篇
  2011年   2708篇
  2010年   2102篇
  2009年   1975篇
  2008年   1847篇
  2007年   1688篇
  2006年   1226篇
  2005年   1052篇
  2004年   934篇
  2003年   832篇
  2002年   811篇
  2001年   602篇
  2000年   583篇
  1999年   606篇
  1998年   2932篇
  1997年   1967篇
  1996年   1269篇
  1995年   776篇
  1994年   601篇
  1993年   670篇
  1992年   256篇
  1991年   260篇
  1990年   195篇
  1989年   197篇
  1988年   199篇
  1987年   174篇
  1986年   156篇
  1985年   180篇
  1984年   152篇
  1983年   124篇
  1982年   159篇
  1981年   185篇
  1980年   185篇
  1979年   92篇
  1978年   97篇
  1977年   308篇
  1976年   665篇
  1973年   79篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
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   
5.
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   
6.
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   
7.
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   
8.
Recent advancements in isolation and stacking of layered van der Waals materials have created an unprecedented paradigm for demonstrating varieties of 2D quantum materials. Rationally designed van der Waals heterostructures composed of monolayer transition-metal dichalcogenides (TMDs) and few-layer hBN show several unique optoelectronic features driven by correlations. However, entangled superradiant excitonic species in such systems have not been observed before. In this report, it is demonstrated that strong suppression of phonon population at low temperature results in a formation of a coherent excitonic-dipoles ensemble in the heterostructure, and the collective oscillation of those dipoles stimulates a robust phase synchronized ultra-narrow band superradiant emission even at extremely low pumping intensity. Such emitters are in high demand for a multitude of applications, including fundamental research on many-body correlations and other state-of-the-art technologies. This timely demonstration paves the way for further exploration of ultralow-threshold quantum-emitting devices with unmatched design freedom and spectral tunability.  相似文献   
9.
10.
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