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   124383篇
  免费   21583篇
  国内免费   4146篇
电工技术   5720篇
技术理论   7篇
综合类   6452篇
化学工业   31054篇
金属工艺   5890篇
机械仪表   6338篇
建筑科学   8632篇
矿业工程   2999篇
能源动力   3550篇
轻工业   12132篇
水利工程   1919篇
石油天然气   5883篇
武器工业   737篇
无线电   16035篇
一般工业技术   21097篇
冶金工业   4996篇
原子能技术   956篇
自动化技术   15715篇
  2024年   284篇
  2023年   1306篇
  2022年   2126篇
  2021年   3494篇
  2020年   3814篇
  2019年   5206篇
  2018年   5431篇
  2017年   5982篇
  2016年   6120篇
  2015年   7136篇
  2014年   7871篇
  2013年   9656篇
  2012年   7863篇
  2011年   7977篇
  2010年   7798篇
  2009年   7387篇
  2008年   6794篇
  2007年   6565篇
  2006年   6498篇
  2005年   5498篇
  2004年   4454篇
  2003年   4712篇
  2002年   5320篇
  2001年   4527篇
  2000年   3476篇
  1999年   2938篇
  1998年   1824篇
  1997年   1525篇
  1996年   1543篇
  1995年   1221篇
  1994年   916篇
  1993年   712篇
  1992年   542篇
  1991年   390篇
  1990年   303篇
  1989年   242篇
  1988年   213篇
  1987年   124篇
  1986年   86篇
  1985年   58篇
  1984年   43篇
  1983年   32篇
  1982年   33篇
  1981年   20篇
  1980年   31篇
  1979年   8篇
  1978年   4篇
  1977年   3篇
  1951年   4篇
  1890年   1篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
本文基于大数据视角设计了电网公司安全生产数据分析平台.通过平台挖掘分析电网公司实时运行数据信息,可全方位充分掌握公司安全生产状态,还可及时发现、共同解决不符合公司发展需要的相关问题,对于公司安全生产与长远稳定发展发挥着重要作用.通过研究表明,安全生产数据分析平台的设计可推动电网公司创新改革安全生产管理模式,切实整合信息资源,提高安全生产水平,实现精益化运营;而明确的平台发展定位与功能优化设计,可确保安全生产数据分析平台高效稳定运转.  相似文献   
82.
Incompressible dipping substrata are commonly encountered in engineering practice. Compared to horizontal underlying strata, the inclined underlying stratum increase the risk of collapse of embankments reinforced with columns because it weakens the restraint of the column base. The objective of this study is to investigate the effectiveness of geosynthetics on improving the embankment stability when the underlying stratum is inclined. The influence of geosynthetic tensile stiffness on the ultimate surcharge and failure mechanism is studied. A deep-seated failure with column tilting occurs when the geosynthetic tensile stiffness is low, whereas a lateral sliding occurs when the geosynthetic tensile stiffness is high. To illustrate the contribution of geosynthetics, the distribution of the lateral pressures acting on the columns is analyzed.  相似文献   
83.
Lithium-sulfur batteries (LSBs) are considered a promising next-generation energy storage device owing to their high theoretical energy density. However, their overall performance is limited by several critical issues such as lithium polysulfide (PS) shuttles, low sulfur utilization, and unstable Li metal anodes. Despite recent huge progress, the electrolyte/sulfur ratio (E/S) used is usually very high (≥20 µL mg−1), which greatly reduces the practical energy density of devices. To push forward LSBs from the lab to the industry, considerable attention is devoted to reducing E/S while ensuring the electrochemical performance. To date, however, few reviews have comprehensively elucidated the possible strategies to achieve that purpose. In this review, recent advances in low E/S cathodes and anodes based on the issues resulting from low E/S and the corresponding solutions are summarized. These will be beneficial for a systematic understanding of the rational design ideas and research trends of low E/S LSBs. In particular, three strategies are proposed for cathodes: preventing PS formation/aggregation to avoid inadequate dissolution, designing multifunctional macroporous networks to address incomplete infiltration, and utilizing an imprison strategy to relieve the adsorption dependence on specific surface area. Finally, the challenges and future prospects for low E/S LSBs are discussed.  相似文献   
84.
International Journal of Information Security - Data integrity is a critical security issue in cloud storage. The data integrity checking schemes by a third-party auditor (TPA) have attracted a lot...  相似文献   
85.
86.
This paper considers the state‐dependent interference relay channel (SIRC) in which one of the two users may operate as a secondary user and the relay has a noncausal access to the signals from both users. For discrete memoryless SIRC, we first establish the achievable rate region by carefully merging Han‐Kobayashi rate splitting encoding technique, superposition encoding, and Gelfand‐Pinsker encoding technique. Then, based on the achievable rate region that we derive, the capacity of the SIRC is established in many different scenarios including (a) the weak interference regime, (b) the strong interference regime, and (c) the very strong interference regime. This means that our capacity results contain all available known results in the literature. Next, the achievable rate region and the associated capacity results are also evaluated in the case of additive Gaussian noise. Additionally, many numerical examples are investigated to show the value of our theoretical derivations.  相似文献   
87.
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   
88.
The ‐centroid problem or leader–follower problem is generalized considering different customer choice rules where a customer may use facilities belonging to different firms, if the difference in travel distance (or time) is small enough. Assuming essential goods, some particular customer choice rules are analyzed. Linear programming formulations for the generalized ‐medianoid and ‐centroid problems are presented and an exact solution approach is applied. Some computational examples are included.  相似文献   
89.
When solving a mathematical problem, students who do not have sufficient conceptual understanding may perform poorly and exhibit misconceptions. This study was aimed to examine students' conceptual understanding and significant misconceptions when solving number sense‐related problems. An online three‐tier diagnostic test was administered to 125 fifth‐grade students with varied socio‐economic backgrounds in Hong Kong. Only 14.40% of the students exhibited high performance with high confidence, indicating that these students had a profound conceptual understanding of number sense. In addition, the majority of the students (66.40%) did not demonstrate number sense; these students exhibited several significant misconceptions and could solve the questions only by using a rule‐based method or guessing. Accordingly, most students performed unsatisfactorily on number sense‐related problems. This study is imperative in identifying early predictors and provides information for further compatible interventions in the teaching and learning of number sense in Hong Kong in particular and worldwide in general.  相似文献   
90.
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