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   1505924篇
  免费   27668篇
  国内免费   6931篇
电工技术   34630篇
综合类   6406篇
化学工业   265799篇
金属工艺   65230篇
机械仪表   43535篇
建筑科学   45586篇
矿业工程   11571篇
能源动力   50369篇
轻工业   110837篇
水利工程   15329篇
石油天然气   37706篇
武器工业   140篇
无线电   197759篇
一般工业技术   286195篇
冶金工业   165104篇
原子能技术   34257篇
自动化技术   170070篇
  2021年   15417篇
  2020年   11875篇
  2019年   14638篇
  2018年   17107篇
  2017年   16600篇
  2016年   21978篇
  2015年   17524篇
  2014年   28768篇
  2013年   88296篇
  2012年   35693篇
  2011年   49088篇
  2010年   43781篇
  2009年   52160篇
  2008年   45659篇
  2007年   43126篇
  2006年   44578篇
  2005年   40176篇
  2004年   41748篇
  2003年   41460篇
  2002年   40549篇
  2001年   37142篇
  2000年   35571篇
  1999年   34676篇
  1998年   44598篇
  1997年   39288篇
  1996年   35358篇
  1995年   30799篇
  1994年   28761篇
  1993年   28681篇
  1992年   26247篇
  1991年   22873篇
  1990年   23304篇
  1989年   22308篇
  1988年   20869篇
  1987年   19074篇
  1986年   18539篇
  1985年   21878篇
  1984年   22040篇
  1983年   19992篇
  1982年   19024篇
  1981年   19114篇
  1980年   17777篇
  1979年   18271篇
  1978年   17585篇
  1977年   17517篇
  1976年   18737篇
  1975年   15889篇
  1974年   15356篇
  1973年   15466篇
  1972年   13027篇
排序方式: 共有10000条查询结果,搜索用时 171 毫秒
991.
ABSTRACT

This paper proposes the multiple-hypotheses image segmentation and feed-forward neural network classifier for food recognition to improve the performance. Initially, the food or meal image is given as input. Then, the segmentation is applied to identify the regions, where a particular food item is located using salient region detection, multi-scale segmentation, and fast rejection. Then, the features of every food item are extracted by the global feature and local feature extraction. After the features are obtained, the classification is performed for each segmented region using a feed-forward neural network model. Finally, the calorie value is computed with the aid of (i) food volume and (ii) calorie and nutrition measure based on mass value. The experimental results and performance evaluation are validated. The outcome of the proposed method attains 0.947 for Macro Average Accuracy (MAA) and 0.959 for Standard Accuracy (SA), which provides better classification performance.  相似文献   
992.
Abdellah  W. M. 《Radiochemistry》2020,62(3):347-358
Radiochemistry - The study deals with separation of uranium, thorium, and yttrium with highest possible purity from El-Garaa El-Hamara sulfate leach liquor. From the latter, almost complete...  相似文献   
993.
The ability of bacterial species to colonize and infect host organisms is critically dependent upon their capacity to adhere to cellular surfaces of the host. Adherence to cell surfaces is known to be essential for the activation and delivery of certain virulence factors, but can also directly affect host cell signaling to aid bacterial spread and survival. In this review we will discuss the recent advances in the field of bacterial adhesion, how we are beginning to unravel the effects adhesins have on host cell signaling, and how these changes aid the bacteria in terms of their survival and evasion of immune responses. Finally, we will highlight how the exploitation of bacterial adhesins may provide new therapeutic avenues for the treatment of a wide range of bacterial infections.  相似文献   
994.
995.
996.
997.
998.
Itaconate (ITA) is an emerging powerhouse of innate immunity with therapeutic potential that is limited in its ability to be administered in a soluble form. A library of polyester materials that incorporate ITA into polymer backbones resulting in materials with inherent immunoregulatory behavior is developed. Harnessing hydrolytic degradation release from polyester backbones, ITA polymers result in the mechanism specific immunoregulatory properties on macrophage polarization in vitro. In a functional assay, the polymer-released ITA inhibits bacterial growth on acetate. Translation to an in vivo model of biomaterial associated inflammation, intraperitoneal injection of ITA polymers demonstrate a rapid resolution of inflammation in comparison to a control polymer silicone, demonstrating the value of sustained biomimetic presentation of ITA.  相似文献   
999.
The partitioning of predominant lipophilic olive bioactives (squalene, β-sitosterol and α-tocopherol) in olive oil processing was studied for the first time using common integrated olive milling plant. 7% of the oil and 5% of the squalene present in the olives was lost in the last pomace. β-sitosterol and α-tocopherol, which are mainly concentrated in the seed of the olive fruit, was recovered in virgin olive oil to a lesser extent (66%, 67%) while 10% were lost in last pomace. Thus, the loss of β-sitosterol and α-tocopherol was higher than that of squalene and oil, due to nonrecovered bound forms. 19% of the α-tocopherol and 21% of the β-sitosterol loss was unaccounted for, which can be attributed to degradation of α-tocopherol and incomplete recovery of sterols from the olive and pomace matrices. This study provides a basis for process development studies.  相似文献   
1000.
Fluorescent nanodiamonds (fNDs) containing nitrogen vacancy (NV) centers are promising candidates for quantum sensing in biological environments. This work describes the fabrication and implementation of electrospun poly lactic‐co‐glycolic acid (PLGA) nanofibers embedded with fNDs for optical quantum sensing in an environment, which recapitulates the nanoscale architecture and topography of the cell niche. A protocol that produces uniformly dispersed fNDs within electrospun nanofibers is demonstrated and the resulting fibers are characterized using fluorescent microscopy and scanning electron microscopy (SEM). Optically detected magnetic resonance (ODMR) and longitudinal spin relaxometry results for fNDs and embedded fNDs are compared. A new approach for fast detection of time varying magnetic fields external to the fND embedded nanofibers is demonstrated. ODMR spectra are successfully acquired from a culture of live differentiated neural stem cells functioning as a connected neural network grown on fND embedded nanofibers. This work advances the current state of the art in quantum sensing by providing a versatile sensing platform that can be tailored to produce physiological‐like cell niches to replicate biologically relevant growth environments and fast measurement protocols for the detection of co‐ordinated endogenous signals from clinically relevant populations of electrically active neuronal circuits.  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