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   83016篇
  免费   7763篇
  国内免费   5029篇
电工技术   5659篇
技术理论   1篇
综合类   8035篇
化学工业   12305篇
金属工艺   5076篇
机械仪表   5364篇
建筑科学   5803篇
矿业工程   2320篇
能源动力   2194篇
轻工业   7536篇
水利工程   1863篇
石油天然气   3314篇
武器工业   774篇
无线电   9637篇
一般工业技术   8565篇
冶金工业   3554篇
原子能技术   1232篇
自动化技术   12576篇
  2024年   194篇
  2023年   951篇
  2022年   1817篇
  2021年   2684篇
  2020年   2094篇
  2019年   1782篇
  2018年   1907篇
  2017年   2103篇
  2016年   2059篇
  2015年   2976篇
  2014年   4005篇
  2013年   4868篇
  2012年   5852篇
  2011年   6298篇
  2010年   6035篇
  2009年   5886篇
  2008年   5901篇
  2007年   5640篇
  2006年   5408篇
  2005年   4548篇
  2004年   3647篇
  2003年   3187篇
  2002年   3735篇
  2001年   3283篇
  2000年   2246篇
  1999年   1516篇
  1998年   950篇
  1997年   803篇
  1996年   718篇
  1995年   627篇
  1994年   462篇
  1993年   345篇
  1992年   277篇
  1991年   208篇
  1990年   179篇
  1989年   117篇
  1988年   108篇
  1987年   77篇
  1986年   35篇
  1985年   47篇
  1984年   39篇
  1983年   32篇
  1982年   17篇
  1981年   23篇
  1980年   21篇
  1979年   16篇
  1978年   10篇
  1977年   12篇
  1976年   15篇
  1959年   10篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
Process object is the instance of process. Vertexes and edges are in the graph of process object. There are different types of the object itself and the associations between object. For the large-scale data, there are many changes reflected. Recently, how to find appropriate real-time data for process object becomes a hot research topic. Data sampling is a kind of finding c hanges o f p rocess o bjects. There i s r equirements f or s ampling to be adaptive to underlying distribution of data stream. In this paper, we have proposed a adaptive data sampling mechanism to find a ppropriate d ata t o m odeling. F irst o f all, we use concept drift to make the partition of the life cycle of process object. Then, entity community detection is proposed to find changes. Finally, we propose stream-based real-time optimization of data sampling. Contributions of this paper are concept drift, community detection, and stream-based real-time computing. Experiments show the effectiveness and feasibility of our proposed adaptive data sampling mechanism for process object.  相似文献   
32.
Herein, we propose a novel method to enhance the photoreactivity of an MOF catalyst by grafting isocyanate bonds ( NCO) and sulfhydryl-complexed copper ( SCu) onto ZIF-8 (NIF-SCu). The grafting process intercalated interlayer bands between the conduction and valence bands of ZIF-8, thereby providing a “ladder” for facile electron transition. The extreme improvement in the photoreactivity of NIF-SCu could be attributed to the enhancement in light responses in the range of 350–450 nm by  NCO groups and the widening of the visible light range of the MOF by  SCu groups. The formation of staggered energy levels in NIF-SCu could also narrow the band gap, lower the resistance, and facilitate the transfer of photogenerated carriers, thereby generating electrons with strong reduction potential in the  SCu conduction band. This study provides a new strategy for improving or even endowing the photoactivity of environmental functional materials with wide bandgaps.  相似文献   
33.
34.
In the field of images and imaging, super-resolution (SR) reconstruction of images is a technique that converts one or more low-resolution (LR) images into a highresolution (HR) image. The classical two types of SR methods are mainly based on applying a single image or multiple images captured by a single camera. Microarray camera has the characteristics of small size, multi views, and the possibility of applying to portable devices. It has become a research hotspot in image processing. In this paper, we propose a SR reconstruction of images based on a microarray camera for sharpening and registration processing of array images. The array images are interpolated to obtain a HR image initially followed by a convolution neural network (CNN) procedure for enhancement. The convolution layers of our convolution neural network are 3×3 or 1×1 layers, of which the 1×1 layers are used to improve the network performance particularly. A bottleneck structure is applied to reduce the parameter numbers of the nonlinear mapping and to improve the nonlinear capability of the whole network. Finally, we use a 3×3 deconvolution layer to significantly reduce the number of parameters compared to the deconvolution layer of FSRCNN-s. The experiments show that the proposed method can not only ameliorate effectively the texture quality of the target image based on the array images information, but also further enhance the quality of the initial high resolution image by the improved CNN.  相似文献   
35.
36.
37.
Zhang  Huawei  Yang  Zhi  Wu  Zhaoyu  Hong  Xiaoyu  Li  Zhong  Xu  Yulai  Li  Jun  Ni  Gaojin  Xiao  Xueshan 《Oxidation of Metals》2019,92(1-2):49-65
Oxidation of Metals - The isothermal oxidation behavior and oxide-scale evolution on a newly developed Ni–Fe-based superalloy were investigated. Three oxidation stages were generally...  相似文献   
38.
39.
The extensive research interests in environmental temperature can be linked to human productivity / performance as well as comfort and health; while the mechanisms of physiological indices responding to temperature variations remain incompletely understood. This study adopted a physiological sensory nerve conduction velocity (SCV) as a temperature‐sensitive biomarker to explore the thermoregulatory mechanisms of human responding to annual temperatures. The measurements of subjects’ SCV (over 600 samples) were conducted in a naturally ventilated environment over all four seasons. The results showed a positive correlation between SCV and annual temperatures and a Boltzmann model was adopted to depict the S‐shaped trend of SCV with operative temperatures from 5°C to 40°C. The SCV increased linearly with operative temperatures from 14.28°C to 20.5°C and responded sensitively for 10.19°C‐24.59°C, while tended to be stable beyond that. The subjects’ thermal sensations were linearly related to SCV, elaborating the relation between human physiological regulations and subjective thermal perception variations. The findings reveal the body SCV regulatory characteristics in different operative temperature intervals, thereby giving a deeper insight into human autonomic thermoregulation and benefiting for built environment designs, meantime minimizing the temperature‐invoked risks to human health and well‐being.  相似文献   
40.
利用猪毛、风化煤和腐植酸钠的水解液为增效剂制备了一种增效过磷酸钙,探讨了增效过磷酸钙的增效机制及其对玉米生长的影响。结果表明,蒸馏水浸提条件下,增效过磷酸钙能减缓水溶磷的释放,具备较高的pH值缓冲性。与普通过磷酸钙相比,增效过磷酸钙处理的玉米生物量平均增加了41.9%,吸磷量和吸钙量分别增加了61.7%和27.8%,根系活力增加了24.3%。该研究结果对过磷酸钙生产的技术改进具有指导意义。  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